Acromioclavicular Joint Arthroscopy and Distal Clavicle Excision

The acromioclavicular (AC) joint is a common but sometimes overlooked source of shoulder problems. Degenerative disease of the AC joint frequently accompanies extrinsic impingement and cuff deterioration and must be addressed at the same time as decompression and/or cuff repair. Conversely, AC disease may also be isolated (osteolysis) and must be distinguished from and treated apart from the rest of the uninvolved shoulder. This chapter discusses the diagnosis and arthroscopic treatment of AC disease.
ANATOMY

The AC joint is an oval-shaped, synovial-lined articulation of the medial concave acromion and the lateral convex end of the clavicle. The joint allows gliding, shearing, and rotational motion. The normal joint has cartilage on the articular surfaces that evolves from hyalin to fibrocartilage as aging occurs.1 The acromial side is most often covered to a variable extent by a fibrocartilaginous disk as described by DePalma.2 His study associated early degenerative AC joint disease with lack of this meniscoid tissue.

The joint is stabilized by thick and strong superior and weaker inferior capsular thickenings—the AC ligaments. The posterior and superior portions of the capsule play the most important role in limiting anterior and posterior translation of the distal clavicle.3 The coracoclavicular ligaments function to stabilize the clavicle to the scapula, with the conoid ligament primarily preventing anterior and superior clavicular displacement. The trapezoid ligament is the primary constraint against compression of the distal clavicle into the acromion4 (Fig. 10.1).

FIGURE 10.1. Acromioclavicular (AC) and coracoclavicular anatomy. A: Superior and inferior AC ligaments. B: Coracoclavicular ligaments—conoid (medial) and trapezoid (lateral). C: Coracoacromial ligament.

The angle of the AC joint on anteroposierior (AP) view is variable. Urisl5 found 49% inclined from superolaleral to inferomedial, 27% vertically oriented, 21% incongruous, and 3% laterally oriented. The joint is also inclined a few degrees from anterolateral to posterior medial on the axillary view (Fig. 10.2).

FIGURE 10.2. AC joint orientation (Urist).

PATHOPHYSIOLOGY

FIGURE 10.3. Degenerative arthritis of the AC joint X-ray appearance.

The AC joint may become symptomatic secondary to a number of etiologies. Traumatic causes include AC separation and distal clavicle fracture. Mumford6 and Gurd7 independently reported in 1941 on resection of the distal clavicle for symptomatic AC joint dislocations. The open procedure gradually evolved into the treatment of choice for degenerative arthritis of the AC joint and for unresponsive osteolysis of the distal clavicle.

The pathoanatomy differs for posttraumatic or degenerative arthropathy as compared to repetitive use or traumatic osteolysis and has some bearing on the arthroscopic approach utilized. The degenerative process is characterized by loss of cartilage, joint space narrowing, osteophytes, and subchondral cysts (Fig. 10.3).

Osteolysis, however, demonstrates a wider joint secondary to an inflammatory hyperemic bone resorption with cystic changes and occasionally cupping of the AC joint8 (Fig. 10.4).

FIGURE 10.4. Radiographic appearance of AC osteolysis.

ASSOCIATED PATHOLOGY

Whether the process is degenerative or osteolytic, associated pathology must be carefully evaluated. Impingement syndrome as described by Neer9 is frequently associated with AC joint disease and must be treated with a concomitant decompression for successful results. Partial- and full-thickness cuff tears, superior labrum anterior to posterior (SLAP) lesions, biceps fraying or rupture, and glenohumeral degenerative disease have all been reported with impingement and AC arthritis.10-11 Similar pathology may also be found in patients with apparent isolated AC osteolysis if glenohumeral arthroscopy is performed at the time of resection.
DIAGNOSIS

Points of concern in the history include previous AC separation or clavicle fracture, the presence of degenerative or inflammatory arthritis, weight-lifting intensity and duration, and repetitive cross-arm usage.

Clinically, the patient will often present with pain radiating along the trapezius to the neck and laterally over the deltoid toward its humeral insertion. Sleeping on the affected side is troublesome, as the joint is compressed. The overlap with rotator cuff complaints is obvious. Discomfort with cross-chest adduction maneuvers is well documented but should localize to the superior aspect of the shoulder and not deep and anterior as found in anterior subcoracoid impingement as described by Gerber et al.12 The patient may complain of pain with extension, adduction, and internal rotation only when the degeneration of the AC joint localizes posteriorly. Weight lifters commonly have problems with bench and military presses.

Physical exam frequently demonstrates localized tenderness at the AC joint and often a prominence of the distal clavicle. Hawkins’s flexion and internal rotation impingement maneuver13 may be positive especially if inferior AC osteophytes are prominent. Straight flexion and abduction and external rotation maneuvers may localize pain at the AC area but not be impressive unless there is associated subacromial impingement. Injection of lidocaine in specific different locations about the shoulder can be very helpful in distinguishing AC disease from subacromial, rotator cuff, bicipital groove, and anterior subcoracoid pathology; 2 to 3 cc of a mixture of 1% lidocaine and 0.25% bupivacaine with a 25-gauge ( 5/8-inch) needle from a superior AC approach should prevent false-positive tests from inadvertent subacromial injection. Effective relief from pain with subsequent provocative maneuvers is a reliable indicator of AC disease.

Imaging Studies

Routine AP and Y (or outlet) lateral x-ray evaluation of the shoulder will often miss AC joint pathology. An AP radiograph of the AC joint with the x-ray beam directed 15 degrees cephalad and the voltage reduced by 30% to 50% will alleviate the superimposition of the joint on the scapular spine and its routine overexposure14,15 (Fig.10.5). Comparison AC views are often necessary for distinguishing the early narrowing and sclerosis of degenerative disease or the contrasting widening and osteopenia of osteolytic disease.

FIGURE 10.5.
A: Standard anteroposterior (AP) shoulder radiograph.
B: Anterior AC joint radiograph with 15-degree cephalad angulation and reduced exposure.

A good-quality axillary view is often the best radiograph for capturing the decreased posterior joint space and sometimes subtle posterior sclerosis noted in those patients with posterior AC arthritis with its associated pain with extension, adduction, and internal rotation. Magnetic resonance imaging (MRI) scans, which are frequently obtained for rotator cuff evaluation, are rarely needed but often available for AC review. Soft tissue enlargement and synovitis and encroachment of inferior joint osteophytes on the bursa and rotator cuff tendons can be appreciated. AC joint impingement, however, has become a popular radiographic diagnosis and needs to be carefully correlated with the patient’s clinical picture lest premature distal clavicle resection be performed. MRI findings associated with osteolysis include diffuse bone marrow edema, cortical thinning or irregularity, and tiny subchondral cysts of the distal clavicle.16 The most sensitive study for diagnosing osteolysis in equivocal cases is a magnesium bone scan, which will demonstrate increased uptake of radiotracer at the distal clavicle and AC joint.

TREATMENT

Nonoperative treatment, which is successful in a majority of cases, consists of (1) activity modification; (2) nonsteroidal antiinflammatories; (3) local steroid injection; (4) passive modalities such as ice, heat, and ultrasound; and (5) preventive therapeutic exercises to avoid atrophy or contracture. Weight lifters who resume, or persist with, their lifting activities generally fail the other nonoperative treatment modalities.8

Indications for operative treatment are failure of conservative care after 6 to 12 months of activity modification (or an unwillingness to give up weight training), localized tenderness with a positive injection test, and positive imaging studies. Debate exists regarding the advisability of either open or arthroscopic distal clavicle excision alone versus resection and stabilization (e.g., Weaver-Dunn or Bosworth procedure) in patients with chronic unstable AC separation.

ARTHROSCOPIC TECHNIQUE

There are two basic approaches to arthroscopic resection of the distal clavicle: superior and subacromial. Both techniques have advantages over the open technique in that they allow evaluation of the glenohumeral joint and subacromial space, permitting diagnosis of previously unrecognized pathology.10,11 They both preserve the deltoid origin, permitting quicker return to activities.17 One can combine these techniques with other arthroscopic or mini-open techniques for rotator cuff repair with less soft tissue trauma, less pain, and improved cosmesis.

Disadvantages of the arthroscopic techniques are that they are technically more demanding, equipment intensive, and have a longer learning curve. There is also the potential for increased morbidity if performed incorrectly (e.g., variable resection, rotator cuff and musculotendinous damage).

Superior Approach

First described by Lanny Johnson18 and championed more recently by Bigliani and Flatow,17,19,20 this technique approaches the AC joint from above through anterior-superior and posterior-superior AC portals. These authors routinely utilized interscalene regional anesthesia and placed the patient in the beach-chair position for this technique, although it can also be performed with the patient in the lateral decubitus position.

The AC joint position and inclination is exactly determined with three 22-gauge needles, and the joint is distended with normal saline. A 2.7-mm, 30-degree arthroscope is then inserted through a posterior-superior portal and a 2.0-mm resector placed through an anterior-superior portal to debride the meniscal remnant and debris. A 2.0-mm burr is then inserted, and removal of the distal clavicle is commenced. The scope and burr are then switched to the opposite portal and bone resection continued until the 4.0-mm arthroscope and larger tapered burr can be inserted. Electrocautery is used to “shell out” the distal clavicle from the surrounding soft tissues, but the capsule and ligaments are not incised. Final beveling of the bone surface is performed with an arthroscopic rasp.

Bigliani and Flatow attempt to resect 5 to 6 mm of distal clavicle with a uniform gap anteriorly and posteriorly. They report a 91% success rate in patients with arthritis or osteolysis with stable AC joints. Failures were due to retained posterior cortical ridges. Patients with previous second-degree AC separations and chronic AC pain faired poorly, with only 37% satisfactory results.20

The proposed advantages of this technique are direct visualization of the pathology “without violating the glenohumeral joint or subacromial bursa” and “precise bone resection and contouring.”20

The disadvantages of this technique are the following:

1. It requires a small joint arthroscope and instruments.
2. Arthritic and tight joints are difficult to operate in.
3. The technique requires one to work backhanded, with the shaver coming toward the scope, with more potential equipment damage.
4. The temptation exists not to examine the glenohumeral joint or the subacromial space, with associated pathology thus left undiagnosed.
5. The posterior-superior portal with multiple passage of scopes, shavers, and burrs likely produces some injury to the most important part of the capsule, the posterior-superior AC joint ligament.

Subacromial Approach

Ellman21 and Esch et al22 were the first to describe the subacromial approach to the AC joint in conjunction with arthroscopic subacromial decompression. Modifications to their approach have been introduced by Tolin and Snyder23 Meyers,24 and Maki.25

All these techniques approach the AC joint while performing subacromial bursoscopy, resecting the medial bursal wall, the fat pad, and inferior AC joint ligament. With the joint exposed, a burr can be introduced posteriorly or laterally, removing that portion of the clavicle that can be pushed into view under the acromion with manual pressure from above. The remaining superior portion of the clavicle is resected from the anterior AC joint portal while viewing from the posterior or lateral portal.

The advantages of this technique are the following:

1. It facilitates concurrent exam of the glenohumeral joint and subacromial bursa to diagnose and treat unrecognized pathology.
2. It is easily performed in conjunction with arthroscopic subacromial decompression.
3. It entails no injury to the posterior-superior capsule.
4. It does not require small joint scopes or instruments.

The disadvantages of this technique are the following:

1. It necessitates traversing and resecting a portion of nonpathologic bursa and inferior capsule in isolated AC joint disease.
2. One or two more portals are necessary.
3. A 70-degree scope may be needed.
4. The technique entails more potential bleeding and fluid extravasation.
5. It may be difficult to deliver the clavicle inferiorly with a medially inclined joint.

The subacromial approach is my preferred method for arthroscopic AC resection. I believe it is imperative to examine the glenohumeral joint and subacromial bursa even with presumed isolated AC joint disease. If this additional exam is performed, four portals rather than two are necessary for the superior approach, negating its major advantage. In addition, sacrifice of the weak inferior AC capsule rather than compromise of the thick and strong posterior-superior capsule is preferable. Finally, routinely switching from small-joint to standard-size arthroscopy equipment seems time-consuming and wasteful.

AUTHOR’S CURRENT SURGICAL TECHNIQUE

The patient is placed in the lateral decubitus position and rolled posteriorly 30 degrees to orient the glenoid parallel to the floor26 with an axillary roll and neutral head support (Fig. 10.6). The arm is abducted 25 to 30 degrees and flexed 10 to 15 degrees, and 10 pounds (15 in heavy or well-muscled patients) of traction applied.

FIGURE 10.6. Lateral decubitus position with axillary roll, padding, and head support exactly in neutral. Patient’s torso is angled posteriorly 25–30˚, orienting glenoid surface parallel to floor.

The next three steps vary with the type of patient:

• Patients with Subacromial Symptoms
• Patients with Apparent AC Disease
• Patients with Either Technique.

Patients with Subacromial Symptoms

The scope is introduced through the standard posterior portal (2 cm inferior and 1 cm medial to the posterolateral corner of the acromion). An anterosuperior outflow cannula is introduced, and glenohumeral arthroscopy from both the anterior and posterior portals utilizing switching sticks is performed. Any intra-articular pathology is addressed (e.g., partial cuff tear, labral or biceps debridement).

The arthroscope is then inserted through the same skin incision into the subacromial bursa with the same anterior portal utilized for outflow and orientation at the anterolateral corner of the acromion, just under the coracoacromial ligament. A midlateral portal is made approximately 3.5 to 4 cm lateral to the acromion and directed slightly up at the undersurface of the acromion and directly at the AC joint (Fig. 10.7). A bursectomy and coracoacromial ligament release, or a subacromial decompression, is then performed, depending on the preoperative diagnosis and arthroscopic appearance.

FIGURE 10.7.
A: Portal position for right shoulder glenohumeral exam and subacromial decompression and distal clavicle resection. Scope posteriorly; gray cannula in lateral portal; blue cannula in anterior superior portal; needle at anterior AC portal.
B: Posterior view of debrided undersurface of right acromion with shaver tip on coracoacromial ligament. Anterior lateral corner of acromion to right.
C: Small amount of anterior and lateral acromial bone resected with burr on lateral edge of CA ligament.

If decompression is indicated, a two-portal, cutting block technique is routinely utilized (Fig. 10.8),27 except in a very thin, broad anterior hooked acromion where a lateral approach as described by Ellman21 would be utilized. After the acromion has been flattened with the burr from the posterior portal, the inferior one-third to one-half of the distal clavicle is often exposed. With the scope still in the lateral portal, the burr is then directed more medially and the lateral 1 to 1.5 cm of the inferior tip of the clavicle is resected. Manual pressure from above can usually deliver much of the remaining clavicle for resection (Fig. 10.8D).

FIGURE 10.8.
A. Scope placed laterally with burr introduced posteriorly for planing of the acromion.
B. Subacromial view of planing from posterior (left) to anterior (right).
C: Further planing with tip of clavicle visible under tip of burr.
D: Completed decompression with inferior clavicle partially resected—lateral view.

The scope is then placed posteriorly and rotated upward, visualizing the line of orientation of the AC joint and remaining superior clavicular bone. The burr (with the aid of an 18-gauge needle) is then introduced through an anterior and slightly inferior AC portal and directed from anterior to posterior and lateral to medial to remove the remaining superior cortical shell (Fig. 10.9).

FIGURE 10.9.
A: Scope placed posteriorly with burr introduced from anterior-inferior AC portal.
B: Posterior view of undersurface of acromion (right), AC joint line,
and clavicle (left) with inferior half of clavicle resected.
C: Burr resecting remaining superior clavicle.

Rotation of the scope from superior to medial exposes the posterior cortex and posterior-superior capsule to view (Fig. 10.10). If bursal tissue compromises visualization, either it can be debrided or the scope can be inserted through the lateral portal. If superior visualization is poor, a 70-degree scope can be utilized.

FIGURE 10.10.
A: Superior clavicle resected exposing superior capsule.
B: Scope rotated medially to view completed clavicle resection.
Posterior superior capsule intact.

Patients with Apparent Isolated AC Diseas

If the glenohumeral joint looks pristine from the posterior portal with the 30-degree scope, I may not utilize an anterior-superior portal and instead finish the 15-point glenohumeral exam with a 70-degree scope from posteriorly.

The scope is then redirected into the subacromial bursa from the posterior portal. If the bursa looks normal, again I will not utilize an anterior portal but still place a lateral portal and introduce a bipolar cautery/ablation tip or a shaver to debride the fat pad and inferior capsule of the AC joint.

Once the AC joint has been exposed, a burr is introduced from an anterior-inferior AC portal and directed from anterior to posterior and inferior to superior, resecting approximately 1.0 to 1.5 cm of the clavicle (and the medial acromial facet if the joint is inclined medially). The scope can be inserted through the lateral portal for visualization of the posterior clavicle if needed. It should be noted that for isolated AC joint disease, only three portals (posterior, lateral, and anterior inferior AC joint) are needed to perform a thorough glenohumeral exam, a subacromial bursoscopy (with minimal violation), and AC resection.

With Either Technique

The gap is then examined to make sure all cortical bone superiorly is removed and resection is even from anterior to posterior. It is measured with two parallel 18-gauge needles from above; 10 to 15 mm of bone is resected with more bone removed in patients with any previous AC instability (Fig. 10.11).

FIGURE 10.11.
A: Needles placed percutaneously in a parallel fashion to measure the amount of distal clavicle resection.
B: Arthroscopic view of gap with needles.
C: Lateral view of acromion (posterior to left) and resected end of clavicle.

The pump pressure is then reduced and hemostasis of larger vessels is obtained with the electrocautery device; 10 cc of 0.25% bupivacaine with epinephrine are instilled into the subacromial space and the incisions are closed with simple 4-0 nylon sutures. No immobilization is utilized unless associated rotator cuff repair is performed.

POSTOPERATIVE CARE

Passive support and motion of the affected shoulder is provided by the opposite arm if needed. Pendulum exercises are started the next day. Home range of motion exercises are utilized the first week. Physical therapy may or may not be utilized depending on the patient’s progress with the home program. Closed chain scapular stabilizing exercises are initiated at the end of week one. Gentle elastic tubing exercises for internal and external rotation are started at week two or three. Light-duty work is instituted early (1/2 to 2 weeks), but heavy labor usually begins at 6 to 12 weeks postoperatively. Sports activities are individualized and variable.

COMPLICATIONS

The complications associated with arthroscopic distal clavicle excision are the following:

1. Inadequate resection.
2. Heterotopic bone formation.
3. Underlying muscle injury.
4. Excessive bleeding

The amount of bone to be resected arthroscopically from the tip of the clavicle is still unresolved. If the posterior-superior AC ligaments are well preserved, the length of the clavicle to removed can be reduced.17 Bigliani20 found a 91% success rate in AC resection with just 5 to 6 mm of resection in patients with arthritis or osteolysis and stable joints. If the posterior and superior ligaments are violated or previously injured, then the remaining tip of the clavicle becomes more unstable and more resection is needed.3,4 Bigliani had only 37% satisfactory results in patients with painful AC joints after second-degree AC separations. However, he continued to perform minimal (5 to 6 mm) resections in this subgroup. Other investigators have had much improved results with second-degree and even third-degree separations with either open or arthroscopic technique when 1.5 to 2 cm of clavicle was resected.28,29

My present practice is as follows:

• In AC joint disease with or without decompression with intact AC and coracoclavicular ligaments —10 to 12 mm of resection.
• In AC joint disease with or without decompression with previous AC ligament injury but generally intact coracoclavicular ligament (second-degree separation or mild third-degree) — 15 to 17 mm of resection.
• Chronic symptomatic, unstable, third-degree or fourth degree AC separation with both AC and coracoclavicular compromise — open modified Weaver-Dunn reconstruction and deltotrapezial fascial repair.

Care should be taken to measure the distance between the clavicle and the acromion with two 18-gauge needles from above; if needed, this should be performed at both the anterior and posterior aspect of the clavicle. It is easy to obtain an uneven gap in resection with more bone removed anteriorly than posteriorly.

Incomplete resection of the superior cortical bone during distal clavicle resection is not uncommon. Clear visualization of this area using either a 30-degree or 70-degree arthroscope is necessary to remove all the superior bone. If a cortical egg shell of bone is left behind, elevation and cross-chest maneuvers will remain painful, and the bone will also serve as a nidus of heterotopic bone formation (Fig. 10.12).

FIGURE 10.12.
Heterotopic bone formation.
A: Immediate postoperative x-ray with slight residual superior bone.
B: Six-month follow-up radiograph showing early heterotopic nidus.
C: Two-year postoperative radiograph demonstrating mature bone in AC interval.

Caution should be exercised when using burrs for resecting the tip of the clavicle. It is easy to wrap up the soft underlying cuff musculature in the instrument. I prefer to use a well-hooded burr with the open side always facing up or in toward the cancellous middle of the clavicle. Suction should be just enough to clear debris.

The vascularity around the tip of the clavicle and AC joint is plentiful. Cauterization of the fat pad underneath the AC joint before the debridement is helpful. It is also beneficial to outline the tip of the clavicle frequently with a cautery device as the clavicle is being resected medially because the periosteal vessels are numerous.

Other strategies can be utilized for the control of bleeding:

• Inject 0.25% bupivacaine with epinephrine into the portals (2 cc) and subacromial space (10 cc) at the beginning of the case.
• Incise skin only and avoid deeper muscle laceration.
• Utilize a blunted conical trocar for penetration of muscle, joint, and subacromial space.
• Add epinephrine, 10 mL (1:1,000 per 3-L bag to first irrigation bag only).
• Utilize electrocautery immediately when significant bleeders are encountered.
• Increase inflow with large bore sheath at scope. A pump with independent control of pressure and flow rate is helpful.
• Decrease outflow to maintain pressure. Control suction on shavers and burrs to reduce “red out.” Integrated fluid deliver and shaver systems are helpful for this problem.
• Reduce blood pressure, if the medical condition allows, to maintain a systolic pressure of less than 95 to 100 mm Hg.
• Increase pressure on pump or elevate bags to level where bleeding is well controlled.

RESULTS

Ellman, Kay, and Harris21 reported on a series of 10 patients treated with the subacromial approach. All patients obtained a satisfactory outcome and returned to their previous level of sports participation. Bigliani17 had a 91% success rate in patients with isolated AC disease with stable clavicles.

My own series encompasses a period of time from 1991 to 1995 (minimum 2-year follow-up) and is composed of 35 cases of AC resection with varying degrees of decompression. The series includes patients with isolated AC disease and those with associated impingement. Excluded were cased with significant rotator cuff tears, biceps degeneration, or instability.

Thirty-five patients had well-documented preoperative and postoperative University of California at Los Angeles (UCLA) scores and returned for a long-term follow-up exam. An additional eight patients were doing well at last exam, had resumed work activities, were happy with their functional level, and did not return for long-term follow-up. One remaining patient complained of pain with light activities but had only slight restriction and could work above shoulder level (UCLA score 27).

In the 35 patients, preoperative UCLA scores averaged 14.83, and postoperative scores were 30.50. Eleven (31%) had excellent results, 19 (54%) good, 3 (9%) fair, and 2 (6%) poor. Of the five patients with fair or poor results, four were female with pain responsive to AC and subacromial injections but recurrent, and radiographic changes that were on the mild end of the spectrum. The one male with a fair result developed postoperative heterotopic bone and had some residual pain with light activities but only slight restriction.

SUMMARY

Arthroscopic AC resection is an increasingly popular technique, performed either primarily or in conjunction with an arthroscopic subacromial decompression. The learning curve for this procedure is steep and should not be underestimated. Two arthroscopic approaches were presented, and both can prove successful, with a more rapid recovery than with traditional open techniques. Diligent preoperative evaluation and intra-operative attention to potential complications will lead to positive surgical outcomes (Fig. 10.13).

FIGURE 10.13.
A: Pre- and postoperative radiograph of arthroscopic subacromial decompression.
B: Pre- and postoperative AP radiograph of AC resection.

REFERENCES

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3. Klimkiewicz J, Sher J, et al. Biomechanical function of acromioclavicular ligaments in limiting anterior posterior translation of the acromioclavicular joint. Paper presented at the open meeting of the American Shoulder and Elbow Surgeons in 1997, San Francisco, CA.

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11. Lewis DM, Arroyal JS, Pollock RG, et al. Early glenohumeral arthritis diagnosed at arthroscopy for impingement syndrome and rotator cuff disease. Paper presented at the 16th annual meeting of the Arthroscopy Association of North America, 1997, San Diego, CA.

12. Gerber C, et al. The role of the coracoid process in the chronic impingement syndrome. J Bone Joint Surg 1985;67B:703–708.

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15. Zanca P. Shoulder pain: involvement of the acromioclavicular joint. Analysis of 1000 cases. AJR 1971;112:493–506.

16. Patten RM. Atraumatic osteolysis of the distal clavicle: MR findings. J Comput Assist Tomogr 1995;19(1):92–95.

17. Flatow EL, Bigliani LU. Arthroscopic acromioclavicular joint debridement and distal clavicle resection. Oper Tech Orthop 1991;1:240–247.

18. Johnson LL. Shoulder arthroscopy. In: Johnson LL, ed. Diagnostic and surgical arthroscopy. St. Louis: CV Mosby, 1981: 1404.

19. Flatow EL, Cordasco FA, McClusky GM, et al. Arthroscopic resection of the distal clavicle via a superior portal: a critical quantitative radiographic assessment of bone removal [abstract]. Arthroscopy 1990;6:153–154.

20. Bigliani LU, Nicholson GP, Flatow EL. Arthroscopic resection of the distal clavicle. Orthop Clin North Am 1993;24(1): 133–141.

21. Ellman H. Arthroscopic subacromial decompression: analysis of one to three year results. Arthroscopy 1987;3:173–181.

22. Esch J, Ozerkis LR, Helgager JA, et al. Arthroscopic subacromial decompression: results according to the degree of rotator cuff tear. Arthroscopy 1988;4:241–249.

23. Tolin BS, Snyder SJ. Our technique for the arthroscopic Mumford procedure. Orthop Clin North Am 1993;24:143–151.

24. Meyers JF. Arthroscopic debridement of the acromioclavicular joint and distal clavicle resection. In: McGinty JB, ed. Operative arthroscopy. New York: Raven Press, 1991:557–560.

25. Maki NJ. Arthroscopic resection of the acromioclavicular joint: a new two portal technique. Paper presented at the 16th Annual Meeting of the Arthroscopy Association of North America, 1997, San Diego, CA.

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Arthroscopic Subacromial Decompression: Lateral Approach

Arthroscopic subacromial decompression (ASAD) is becoming a widely performed surgical procedure of the shoulder. The technique has evolved from open anterior acromioplasty as described by Neer,^1-2 Hawkins et al,^3’4 Rockwood,⁵ and Bigliani et al.⁶ The transition from open to arthroscopic technique entails a definite learning curve and should not be underestimated. This chapter focuses on the technical aspects of the procedure and how to avoid complications.

HISTORICAL PERSPECTIVE

The arthroscopic technique for subacromial decompression was first described by Johnson7 in 1986. Ellman8 presented the first series with follow-up and detailed description of the operative technique. Esch et al9 evaluated their results with ASAD and related them to the severity of associated rotator cuff tears. Paulos and Franklin¹⁰ presented one of the largest early series (80 patients) and introduced the use of the midlateral subacromial portal.

All of these authors originally described the procedure with the scope viewing from the posterior portal and the instruments entering from a lateral approach.

Sampson et al¹¹ first described the “cutting block” technique for precision acromioplasty in 1991. This technique places the scope laterally and introduces shaving and burring instruments from a posterior portal, using the posterior half of the acromion as a guide for resection. The authors also emphasized the importance of the supraspinatous outlet x-ray in both preoperative planning and postoperative evaluation and the benefits of evaluating the flatness of the cut from both the lateral and the posterior portals.

Many orthopaedists (myself included) who began performing arthroscopic acromioplasty from the originally described lateral approach now routinely utilize a technique incorporating the cutting-block principles. There are, however, still a number of cases where the posterior technique as described by Sampson et al will lead to complications, and the lateral approach with modifications is still preferable.

With either approach, the advantages of arthroscopic versus open subacromial decompression are evident and include the following:

1. Less disruption of deltoid insertion and more rapid rehabilitation.
2. Ability to assess both the articular and bursal surfaces of the rotator cuff and fully evaluate the glenohumeral joint for associated pathology.
3. Ease of combining with other arthroscopic techniques (distal clavicle resection and/or rotator cuff de-bridement or repair).
4. Improved cosmesis.
5. Outpatient setting.

The disadvantages are the significant learning curve and the increased equipment needs of the arthroscopic procedure. Determination of the amount of bone resection especially with the lateral approach, may be more difficult than with open techniques. Complications, if encountered, may be harder to deal with arthroscopically than with an open procedure.

ETIOLOGY

Impingement is a nonspecific clinical syndrome with a number of different underlying etiologies. Accurate diagnosis is imperative to ensure appropriate nonoperative or surgical treatment. Patients complaining of pain with overhead activities are differentiated into one of the following categories:

1. Primary impingement.
2. Secondary impingement.
3. Posterior superior impingement.
4. Anterior subcoracoid impingement.
5. Pseudoimpingement

Primary Impingement

Figure 2.1.1. Neer's impingement sign.

Neer¹ introduced the concept of extrinsic impingement of the anterior acromion, coracoacromial arch, and the acromioclavicular joint on the underlying rotator cuff and biceps tendon. He also emphasized that forward flexion of the arm is the dominant functional position and that anterior decompression, not lateral acromionectomy, is the appropriate operative approach for significant cuff degeneration. His impingement sign is performed with the patient seated in front of the examiner, who stabilizes the scapula as the arm is elevated slightly lateral to the midline to impinge the tuberosity against the acromion (Fig. 2.1.1).

Pain thus produced is eliminated by injecting 10 cc of 1% Xylocaine into the subacromial bursa beneath the anterior acromion (impingement injection test) to confirm the diagnosis. Hawkins and Kennedy⁴ described a second impingement sign in which the arm is flexed forward 90 degrees and then forcibly internally rotated, jamming the supraspinatus tendon against the anterior edge of the coracoacromial ligament to produce pain.

Figure 2.1.2. Hawkins's flexion-internal rotation impingement

Patients with primary extrinsic impingement are usually in an older age group or have a bony architecture with an anterior acromial hook or spur that presses directly on the cuff and biceps with forward elevation of the arm. There is also a younger subgroup of overhead athletes who have benign bony anatomy but have a prominent or hypertrophied anterolateral band of the coracoacromial ligament.¹² This produces an extrinsic irritation of the underlying bursa and cuff and occasionally a snap or click. Both of these types of patients have the most predictable operative success with arthroscopic subacromial decompression or coracoacromial ligament resection when conservative treatment has failed.

Secondary Impingement

The concept of secondary impingement originates with Codman,¹³ who proposed an intrinsic tendinous degeneration as the essential lesion in rotator cuff disease. The micro vascular studies by Rathbun and McNab,¹⁴ Moseley and Goldie,¹⁵ and Rothman and Parke¹⁶ support this concept. This vascular compromise results in tissue devitalization characterized as “angiofibroblastic hyperplasia” by Nirschl.17 The subsequent pain and weakness of the supraspinatus compromises its function as a humeral head depressor and allows the upward humeral migration forces of the deltoid to dominate, producing a secondary impingement of the cuff into the acromion.

F. Jobe et al¹⁸ enlarged this concept to include patients with underlying anterior glenohumeral ligament instability. As the humeral head subluxes anteriorly, the cuff is secondarily compressed against the coracoacromial arch.

Secondary impingement is more prevalent in a younger patient population actively involved in sports activities that entail overhead arm motion, and should be suspected when the bony architecture is unremarkable. The subluxation-relocation test, as described by Jobe et al18 is helpful in differentiating secondary causes of impingement (Fig. 2.1.3). With the arm abducted 90° and externally rotated, an anterior force is applied by the examiner’s hand on the posterior aspect of the humeral head. This accentuates the impingement pain in an unstable shoulder as the head and overlying cuff drive into the anterior edge of the acromial arch (subluxatiori). Conversely, posterior pressure on the head alleviates the impingement discomfort (relocation).

Figure 2.1.3. Jobe's subluxation-relocation test. Subluxation.

Figure 2.1.3. Jobe's subluxation-relocation test. Relocation.

Posterior Superior Impingement

Walsch et al¹⁹ and C. Jobe²⁰ more recently have described another variety of impingement noted in overhead athletes that occurs when the arm is maximally externally rotated while abducted and extended (such as in the cocking phase of throwing). In this position the posterior superior articular surface fibers of the supraspinatus are placed under tension and sheer but are also compressed between the humeral head and adjacent glenoid rim, resulting in posterior superior synovitis and partial under-surface tears. Whether or not any underlying instability is a factor in this compression is still unresolved. While easily confused with primary or secondary anterior impingement, careful examination usually demonstrates pain more at the posterior-superior aspect of the rotator cuff with the arm abducted and externally rotated and extended, in contrast to the impingement positions of Neer and Hawkins. This apprehension position, although painful in this syndrome, does not elicit the usual anxiety found in patients with instability. However, there still may be a reduction of pain with the relocation maneuver of the subluxation-relocation test described by Jobe.

Anterior Subcoracoid Impingement

Gerber et al²¹ have described this type of anterior impingement between the humeral head and the coracoid process secondary to traumatic, iatrogenic, or idiopathic causes. Whatever the underlying etiology, the tip of the coracoid is positioned more lateral than normal, and as the arm is brought into forward flexion there is a compression of the rotator cuff between the humeral head and the tip of the coracoid. This produces pain with Neer’s forward flexion test, but it occurs usually between 80 and 130 degrees of flexion rather than at full flexion. Also Hawkin’s flexion and internal rotation test is consistently positive, but the pain is lower and more anterior than with superior impingement. The patient also demonstrates decreased horizontal adduction with pain similar to that found with acromioclavicular (AC) disease (Fig. 2.1.4), but the pain is again more at the tip of the coracoid and not at the AC joint.

Figure 2.1.4. Horizontal adduction test.

Pseudoimpingement

Gartsman²² coined the term pseudoimpingement syndrome for patients who demonstrated clinical history and physical findings of anterior superior impingement but in whom impingement was due to a lack of full external rotation. This restriction in range of motion does not allow the humerus to rotate externally with elevation, and the rotator cuff is compressed between the greater tuberosity and the acromion when the arm is elevated. This problem is easily confused with primary extrinsic compression but routinely resolves with therapy directed at regaining the lost external rotation.

ANATOMY

Knowledge of the coracoacromial anatomy is crucial both for diagnostic accuracy and operative facility, and the avoidance of complications.

The bony architecture is composed of the acromion, the AC joint, the coracoid process, and the greater humeral tuberosity. The shape of the acromion and contour of its undersurface is best evaluated with Neer’s supraspinatus outlet view (Fig. 2.1.5). Bigliani et al²³ described three distinct acromial shapes: type 1, flat; type 2, curved; and type 3, hooked. They found an increased correlation between the type III hooked acromion and underlying full-thickness rotator cuff tears (69.5% for type 3 and 3% for type 1). This radiographic view is also valuable in determining the overall slope and thickness of the acromion, and in predetermining those cases where the cutting block technique of acromioplasty would be inappropriate.

Figure 2.1.5. Supraspinatus outlet view (right shoulder, anterior to right).

Rockwood and Lyons24 have described a modified anteroposterior (AP) view of the shoulder for differentiating the hooked acromion. This x-ray involves angulating the beam 30 degrees caudad to accentuate the anterior acromial protruberance (Fig. 2.1.6). Although this view is helpful in terms of diagnosis, it is not particularly useful in terms of preoperative planning or determining whether to use a lateral or a posterior approach for the acromioplasty.

The AC joint borders the coracoacromial space medially. As it degenerates, it may play an active role in the extrinsic impingement process. Osteophytic overgrowth on the undersurface of the distal clavicle and medial acromion can impinge on the underlying rotator cuff. The pain of an arthritic or osteolytic joint can also mimic that of anterior impingement. Careful preoperative evaluation is necessary to avoid residual pain at the AC joint after decompression.

Figure 2.1.6. A 30-degree caudal tilt view (right shoulder).

The coracoid process forms the anterior border of the subacromial space. It may be enlarged, fractured, or iatrogenically altered, such as occurs with a laterally positioned Bristow transfer of the coracoid tip onto the anterior glenoid rim. Fractures of the coracoid can occur with the recoil of a rifle into the shoulder in hunters. A posterior opening wedge osteotomy for instability also effectively lateralizes the coracoid tip relative to the humeral head. These changes, which can be associated with anterior subcoracoid impingement, are best noted on axillary view x-rays or a computed axial tomography (CAT) scan with the arm flexed 90 degrees and internally rotated.

The greater tuberosity of the humerus forms the floor of the coracoacromial space. It is important to note its size and shape, any osteophytic overgrowth, sclerosis, erosion, or cysts. It is best evaluated radiographically with an AP view with the arm in external rotation.

Soft Tissue Anatomy

It is important to remember that the subacromial bursa is an anterior structure. It extends from the anterior one-half to one-third of the acromion to just medial to the AC joint to 1 to 2 cm anterior to the acromion and 2 to 3 cm laterally (Fig. 2.1.7). The bursal wall is frequently thickened and troublesome posteriorly, and has been named the “posterior bursal curtain.” This curtain frequently “closes” as one backs the scope posteriorly to get a larger field of view of the subacromial bursa. It is frequently necessary to resect a portion of this structure when performing subacromial surgery.

Figure 2.1.7. Anterior view of latex injected subacromial bursa. Black arrow, anterior edge of bursa; white arrow, superolateral bursa; black wedge, coracoacromial ligament.

The anatomy of the coracoacromial ligament is pertinent to the technique of acromioplasty. It attaches to the front and undersurface of the acromion as a thick band and continues around the anterolateral corner to attach to the lateral ridge for a variable distance. Anteriorly the coracoacromial ligament attaches to the anterior inferior edge of the acromion, while the deltoid fascia attaches more superiorly (Fig. 2.1.8). As the coracoacromial ligament is detached, it falls away easily from the overlying anterior deltoid muscle and fascia. Laterally, however, the coracoacromial ligament blends inextricably with the deltoid muscle fascia along the lateral acromion. Care must be taken not to aggressively detach the fascia or resect too much bone laterally, as this may result in a deltoid detachment.

Figure 2.1.8. Lateral view of coracoacromial ligament and deltoid fascia attachment on anterior acromion.

Gallino et al26 found that the CA ligament has a variable thickness of insertion on the undersurface of the acromion, ranging from 2 to 5.6 mm. Those patients with excessively thickened ligaments would be the ones most likely to have anterior functional stenosis and/or snapping, as described by O’Boyle et al,12 and benefit from anterolateral band resection.

Edelson and Luchs²⁵ and others have noted various degrees of transformation of the coracoacromial ligament into bone at its acromial insertion. Gartsman22labeled this phenomenon “anterior acromial protruberance.” Rockwood5 in his open technique recommends resecting 8 to 10 mm of full-thickness anterior bone and then reattaching the deltoid fascia. This technique of full-thickness anterior bone resection back to the level of the AC joint has insinuated itself into some authors’ description of subacromial decompression.²⁶ For the most part the anterior acromial protruberance is really an inferior extension of calcification into the coracoacromial ligament insertion. One does not need to resect full-thickness acromial bone anteriorly to remove it, and in fact great care should be taken not to resect too much superior anterior bone, as this may detach the anterior deltoid fascia producing an operative disaster. The best radiographic views for determining the amount of anterior acromial protruberance are the axillary view and the supraspinatus outlet view (Fig. 2.1.9). The axillary x-ray is also an excellent view for evaluation of the AC joint, particularly for picking up posterior AC arthritis that may be missed on a routine AP view.

Figure 2.1.9. Anterior acromial protuberance on axillary view. Protuberance (shaded portion).

Figure 2.1.9. Anterior acromial protuberance on axillary view. Radiograph demonstrating anterior acromial protuberance.

DIAGNOSISM

The history is important. Pain with the cocking and acceleration phase of throwing is most likely secondary to an underlying instability or posterior superior impingement. Nocturnal and rest pain is often indicative of a rotator cuff, whereas patients with cuff tendinitis develop pain with progressive activity.²⁷ Other causes of shoulder pain such as scapular thoracic bursitis, suprascapular nerve syndrome, cervical radiculopathy, and referred pain from the gallbladder, liver, lung, or heart also need to be differentiated.

The clinical signs and x-rays noted previously are the most valuable in making a diagnosis of impingement. Concomitant rotator cuff disease or AC joint disease can be evaluated with both an arthrogram or magnetic resonance imaging (MRI). The arthrogram may be more accurate in determining full-thickness rotator cuff tears but less sensitive in picking up partial-thickness lesions or intratendinous pathology. Isolated AC joint injection and/or bone scan may be helpful in differentiating AC joint versus sub-acromial disease. It is important to know the status of the AC joint prior to arthroscopic decompression so that residual pathology in this location is not left unattended.

TREATMENT

Conservative care should be diligent and prolonged. The goal is to diminish the inflammation in the tissues and then regain full range of motion and full strength in the scapular stabilizers and rotator cuff to balance the deltoid force couple. This is accomplished with rest, hot and cold modalities, massage, nonsteroidal antiinflammatories, and selective injection. Directed physical therapy and home treatment programs are beneficial. Various authors have recommended from 6 to 18 months of conservative care prior to consideration of operative intervention.

Operative Indications for Arthroscopic Subacromial Decompression

1. Primary extrinsic impingement with type II or III acromion or coracoacromial ligament calcification. Clearly, this patient population has the most predictable success with either the open or arthroscopic operation.
2. Secondary impingement with associated bony changes in conjunction with arthroscopic stabilization for anterior instability.
3. Elderly patients with bony changes and full-thickness rotator cuff tears. If the cuff can technically be repaired and the patient can comply with the postoperative rehabilitation, then studies would indicate that the final outcome will be more favorable if this is performed either arthroscopically, mini-open, or as an open procedure with the ASAD. Unrepairable massive tears may also respond to decompression, as demonstrated by Rockwood for open procedures.²⁸ When associated, however, with significant glenohumeral degenerative arthritis or superior migration of the humeral head, decompression is not recommended and maintenance of the coracoacromial arch with implantation of an oversized humeral hemiarthroplasty may prove more successful.
   In conjunction with arthroscopic or mini-open rotator cuff repair.
   

Indications for Bursectomy, CA Ligament Release, and Resection

1. Younger patients with type I acromion but unresponsive subacromial pain and/or snapping with abduction and rotational maneuvers.
2. Calcific tendinitis of the supraspinatus or subscapularis when associated with type III acromion.

Contraindications

1. Secondary impingement with underlying instability in a young athlete with a type I acromion.
2. Psuedoimpingement syndrome.
3. Anterior subcoracoid impingement.
4. Isolated AC osteolysis.
5. Undersurface partial cuff tears with normal subacromial bursa and benign bony architecture.
6. Association with massive rotator cuff tears and significant degenerative arthritis of the glenohumeral joint.

OPERATIVE TECHNIQUE

Careful preoperative evaluation is necessary to determine the appropriate operative approach and to avoid complications. Outlet and axillary views are the key to evaluating the acromion. The outlet view is utilized to determine the shape of the acromion (type II or type III) and the overall thickness.^22,29 On the outlet view, lines are drawn on the undersurface of the acromion—one from the front tip of the acromion to the posterior edge, and a second line along the posterior half of the undersurface of the acromion extending out anteriorly. The distance between these two lines at the anterior margin approximates the amount of undersurface anterior bone that will be resected (Fig. 2.1.10).

Figure 2.1.10. Preoperative planning for ASAD. a, cutting block line.

The axillary view is used to determine the shape of the acromion (cobra versus square tipped) and whether there is any anterior acromial protruberance. If present, this protuberance will need to be resected at the time of coracoacromial ligament release.

If on the outlet view one notes a very thin or curved acromion, the cutting block line on the undersurface of the posterior half of the acromion may actually exit the superior aspect of the acromion, taking off too much anterior bone (Fig. 2.1.11). In these cases, the cutting block technique, as described by Sampson et al,¹¹ would be inappropriate. Instead, the lateral approach (described below) would be more applicable, removing just a small anterior hook and not producing a type I flat acromion.

Figure 2.1.11. Thin curved acromion where cutting-block technique would not be appropriate. a, Original cutting-block line. b, Modified cut resecting only anterior hook, preserving deltoid fascia and not producing a type I flat acromion.

Poor visualization in the subacromial space is one of the more frustrating aspects of either approach and is usually secondary to either excessive bleeding or inadequate debridement of the subacromial space. Use of electrocautery is strongly recommended. Other strategies to control bleeding during arthroscopic subacromial decompression include the following:

1. Inject 0.25% bupivacaine with epinephrine into the portals (2 cc) and subacromial space (10 cc) at the beginning of the case.
2. Incise skin only and avoid deeper muscle laceration.
3. Use a blunted conical trocar for penetration of muscle, joint, and subacromial space.
4. Add epinephrine, 10 mL (1:1,000) per 3-L bag to first irrigation bag only.
5. Avoid debridement of anterior medial acromion and the undersurface of the AC joint until late in the case.
6. Use electrocautery immediately when significant bleeders are encountered.
7. Increase inflow with large-bore sheath at scope. A pump with independent control of pressure and flow rate is helpful.
8. Decrease outflow to maintain pressure. Control suction on shavers and burrs to reduce “red out.” Integrated fluid delivery and shaver systems are helpful for this problem.
9. 9. Reduce blood pressure if medical condition allows, to maintain systolic pressure of less than 95 to 100 mm Hg.
10. 10. Increase pressure on pump and elevate bags to level where bleeding is well controlled.

Operating Room Setup (Fig. 2.1.12)

I perform the procedure in an outpatient setting with the patient in the lateral decubitus position. I use general anesthesia. I don’t routinely use an interscalene nerve block, but this may ensure better postoperative pain control. The procedure may also be done in a beach-chair position with regional anesthesia as per surgeon preference.

The table is turned approximately 100 to 110 degrees from the anesthesiologist, who is then situated at the patient’s abdomen. Long anesthesia tubing is required. The TV monitor tower with contained video equipment is positioned directly anterior to the patient’s head and chest. The shoulder holder is attached to the operating table on the anterior side of the body near the foot. The inflow pump is positioned so that it can be observed by the surgeon during the procedure.

Figure 2.1.12

Patient Preparation

The patient is positioned in the modified lateral decubitus position as described by Gross and Fitzgibbons.30 This position rolls the patient back 25 to 30 degrees, placing the glenoid orientation parallel to the floor (Fig. 2.1.13). The patient is placed in the beanbag with the U position toward the head and the tails extending to the superior-anterior and posterior chest cephad to the axilla for support. The shoulder is isolated with large plastic U drapes, and traction is applied to the patient’s arm. An axillary roll and appropriate head support is utilized. The arm is positioned at approximately 30 degrees of abduction and 10 degrees of flexion with 7 to 15 pounds of traction applied depending on the patient’s size and muscularity. A second dual-traction apparatus may be applied if a stabilization procedure needs to be performed.

Figure 2.1.13A - Patient position with appropriate support for head and axillary roll.

Figure 2.1.13B - Roll-back position (Gross30 with permission)

PROCEDURE

Glenohumeral Diagnostic Arthroscopy

The anatomy of the shoulder is outlined with a marking pen prior to the operative procedure and the portals marked. The glenohumeral joint is then examined completely from both a posterior and a high anterior portal, established inside out at the superior aspect of the rotator interval. This will later be the anterior portal for the subacromial bursoscopy. Any pathology within the glenohumeral joint is appropriately addressed.

Figure 2.1.14.

Partial undersurface or small complete rotator cuff tears are frequently marked with a tag suture placed through an 18-gauge needle introduced from superiorly into the joint and retrieved out the anterior portal (Fig. 2.1.14). This suture marker is beneficial later when subacromial bursoscopy is performed, as it provides a quick reference to the questionable cuff area from the superior view. The scope is then removed from the glenohumeral joint and through the same posterior skin portal, redirected at a 10-degree caudad angle to the acromion into the subacromial bursa and far enough anteriorly to enter the chamber. If the bursa is easily entered and distended, then the inflow is brought in at the scope with a pump and a lateral portal is then made on the basis of an accurately placed 18-gauge needle.

If the bursa is significantly inflamed or not easily distended, with poor visualization, then the scope trocar and sheath is brought directly out anteriorly just lateral to the coracoacromial ligament to exit from the previously made high anterior skin portal. The outflow cannula is then placed on the tip of the trocar and pushed back into the subacromial space so that it lies under the anterior half of the acromion. The sheath is separated slightly, the scope is inserted into the posterior cannula, and flow and visualization are established. A lateral portal is then directed with an 18-gauge needle.

The bursa is then viewed from posteriorly and debrided from the lateral portal until good visualization is established. Any suspicious areas of the rotator cuff that may have been previously identified with a suture marker are debrided and examined from both the posterior portal and the lateral portal.

Lateral Approach for Subacromial Decompression

Preoperatively I will have decided whether I am going to use a modified lateral approach or a cutting-block approach for the decompression. If the patient has a thin curved acromion and a lateral approach is appropriate, I place my lateral portal 3.5 to 4 cm lateral to the acromion and about midway between the midportion of the acromion and the anterolateral corner. I make sure with an 18-gauge needle that I can get the shaver along the anterior-inferior edge of the acromion and a short distance down the anterolateral side, and that it can be directed slightly upward at the acromion for ease in burring and shaving.

The undersurface of the anterior half of the acromion is then debrided with an aggressive shaver and/or a cautery ablation system (Fig. 2.1.15). Care should be taken with either instrument to stay on the undersurface of the bone and not pop off anteriorly or laterally into the deltoid fibers, which are very vascular. The anterolateral corner of the acromion is identified with an 18-gauge needle directed from superiorly, and the debridement is started at this point and progresses medially toward the AC joint and also posteriorly.

Figure 2.1.15.

From the preoperative planning, the amount of bone to be resected is known, as is the diameter of the burr. Starting at the anterolateral corner, the appropriate amount of anterior hook is resected from anterior to medial. Care is taken not to remove full-thickness bone anteriorly and thereby detach the anterior deltoid fascia. This cannot be subsequently repaired as in open operative procedures. After the anterior bone is resected from lateral to medial, tapering of the remaining posterior bone is then accomplished from anterior to posterior to the midportion of the clavicle, or the scope can be placed laterally and the shaver introduced posteriorly to taper from posterior to anterior. Because of the thin and curved nature of the acromion, the goal is not to produce a completely flat undersurface but to perform a smooth and even taper (Fig. 2.1.16). Whether one tapers from anterior to posterior or posterior to anterior, the scope is always placed laterally to evaluate the decompression in two planes.

Figure 2.1.16A Preoperative outlet x-ray of think curved acromion with exuberant osteophyte.

Figure 2.1.16B Postoperative x-ray of anterior osteophyte and hook resection. Note increased anterior acromial-humeral distance in spite of nonflat acromial undersurface.

If there is no evidence of degenerative disease of the AC joint and no inferior osteophytes, I do not take the decompression into the joint or bevel it. If inferior osteophytes are present, then the undersurface of the AC joint is exposed and the osteophytes removed. Manual pressure from above will then deliver a portion of the distal clavicle to view and if it is noticeably arthritic, an arthroscopic distal clavicle resection can be performed. If the articular cartilage looks healthy, then the beveling alone would be performed.

Following adequate decompression, the pump pressure is reduced and hemostasis is obtained with the electrocautery unit. The subacromial space is then instilled with 10 cc of 0.25% bupivacaine with epinephrine and then 1 to 2 cc in each incision. The portals are closed with 4-0 nylon and a sterile dressing is applied.

Postoperative Care

Immediate postoperative motion is allowed and encouraged. No sling is utilized. On the first postoperative day, passive and active motion is encouraged to avoid the possibility of developing an adhesive capsulitis or captured shoulder, as described by Gross’s group.31 Patients are allowed to return to sedentary work as soon as possible. Heavy manual labor usually requires a slower progression and may take from 6 to 12 weeks.

RESULTS

I routinely utilize a two-portal cutting-block technique as described by Sampson et al.11 Although I orient the acromion on the top of the screen when I am in either the posterior or lateral portal, the principles of the procedure still apply. I have found this technique to be considerably more reproduceable and reliable than the traditional lateral approach as described herein and by Ellman8 and utilize it for at least 95% of my subacromial decompressions. On the rare occasions where a thin, broad, and curved acromion is encountered, then the cutting-block technique is inappropriate. The lateral approach as described above is still utilized with success.

REFERENCES

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2. Neer CS. Impingement lesions. Clin Orthop 1983;173:70-77.

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10. Paulos LE, Franklin JL. Arthroscopic shoulder decompression development and application—five year experience. Am J Sports Med 1990; 18:235-244.

11. Sampson TG, Nisbet JK, Glick JM. decision acromioplasty in arthroscopic subacromial decompression of the shoulder. Arthroscopy 1991;7:301-307.

12. O’Boyle M, Newton PM, Arroyo JS, et al. Arthroscopic resection of the anterolateral and of the coracoacrornial ligament for impingement in the overhead athlete. Paper presented at the 16th Annual Meeting of the Arthroscopy Association of North America, San Diego, California, April 1997.

13. Codman EA. Rupture of the supraspinatus tendon and other lesions in or about the subacromial bursa. In: The shoulder. Boston: Thomas Todd, 1934;73-75.

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19. Walsch G, Boylau P, Noel E, et al. Impingement of the deep surface of the supraspinatus tendon on the posterior superior glenoid rim: an arthroscopic study. J Shoulder Elbow Surg 1992; 1:238-245.

20. Jobe CM. Posterior superior glenoid impingement: expanded spectrum Arthroscopy. 1995;11:530-536.

21. Gerber C, Terier F, Ganz R, The role of the coracoid process in chronic impingement syndrome. J Bone Joint Surg 1985; 678:703-708.

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25. Edelson JG, Luchs J. Aspects of coracoacrornial ligament anatomy of interest to the arthroscopic surgeon. Arthroscopy 1995;11:715-719.

26. Gallino M, Vatiston B, Annaratone G, et al. Coracoacromiol ligament: a comparative arthroscopic and anatomic study. Arthroscopy 1995;ll:564-567.

27. Esch JC, Baker CL. Rotator cuff disease and impingement. In: Whipple TL, ed. Arthroscopic surgery—the shoulder and elbow. Philadelphia: JB Lippincott, 1993:161-163.

28. Rockwood CA Jr. Shoulder function following decompression and irrepairable cuff lesions. Orthop Trans 1984;8:92.

29. Wuh HCK, Snyder SJ. Modified classification of the supraspinatus outlet view based on the configuration and the anatomical thickness of the acromion. Paper presented at the Fifty-Ninth Annual Meeting of the American Academy of Orthopedic Surgeons, Washington, DC, February 1992.

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31. Mormino MA, Gross RM, McCarthy JA. Captured shoulder a complication of rotator cuff surgery. Arthroscopy 1996;12 457-461.

Arthroscopic Subacromial Decompression
Posterior (Cutting Block) Approach

Indications

1. Primary extrinsic impingement syndrome with subacromial bursitis and/or cuff tendinosis with type II or III acromion.
2. Chronic secondary impingement with adaptive pathologic sub-acromial bony/soft tissue changes (e.g., anterior acromial traction spur or undersurface acromial fraying or bursal cuff degeneration).
3. Lack of response to diligent conservative treatment program including scapular and rotator cuff retraining, non-steroidal anti-inflammatory drugs, subacromial injection, and activity modification for 6 to 12 months.

Contraindications

1. Secondary impingement with underlying subluxation.
2. Internal posterior-superior impingement with/without superior labrum anterior and posterior (SLAP) lesion.
3. Anterior subcoracoid impingement.
4. Pseudo-impingement.

Mechanism of Injury

Elevation of arm abuts the greater tuberosity against the prominent anterior acromial hook or coracoacromial spur, resulting in inflammation and bursal side degeneration/tearing of the rotator cuff and/or biceps tendon.

Physical Examination

1. Pain with impingement maneuvers (Neer and Hawkins signs) relieved with subacromial injection of lidocaine.
2. Tenderness to palpation of anterior acromion and anterior and superior cuff when arm is extended.
3. Pain with resisted abduction and flexion (cuff tendinosis) and/or positive Speed’s test (biceps tendinosis).

Diagnostic Tests

1. Standard shoulder radiographs including outlet, glenohumeral anteroposterior (AP), axillary, and acromioclavicular (AC) views to evaluate acromial morphology and AC disease.
2. Magnetic resonance imaging, arthrogram, or ultrasound may be utilized to further evaluate rotator cuff and biceps tendon.
3. Selective lidocaine injections into subacromial space versus AC joint versus bicipital groove to delineate pathology.

Special Considerations

Impingement symptoms in younger patients with benign bony morphology are likely secondary to underlying scapular or cuff/deltoid muscle imbalance or glenohumeral instability, and these problems should be addressed prior to consideration of arthroscopic subacromial decompression. Success with arthroscopic subacromial decompression (ASAD) can only be expected with extrinsic primary impingement, or chronic secondary as noted above.

Preoperative Planning and Timing of Surgery

1. Outlet and axillary views are key to evaluating the acromion. AP of AC joint and axillary views are key for the AC joint.
2. Determine the shape (should be type II or III or you are likely performing an inappropriate procedure) and thickness of acromion on outlet view. Draw two lines: one on the undersurface of the acromion from the front tip to the back edge; a second line along the posterior one half of the undersurface of the acromion extending through the anterior acromion. The distance between these two lines approximates the amount of undersurface anterior bone that will be resected (Fig. 10-1A).


Figure 10-1 A. Radiographs allow determination of the shape and thickness of the acromion on the outlet view.

3. Visualize the AC joint and acromion on the axillary view to determine the amount of anterior acromial protuberance that extends anterior to the AC joint. This approximates the amount of bone that will be taken off anteriorly :is one resects the AC spur in addition to the undersurface bone (Fig. 10-1B).


Figure 10-1 B. The axillary view allows determination of the amount of a interior acromial rotuberance that will be removed. Co=coracoid, Cl=clavicle, Ac=acromion, H=humerus

4. It is important on the outlet view to evaluate the thickness and shape of the acromion because those that are very thin and curved will not be candidates for the “cutting block” technique as too much bone would be resected, risking acromial fracture or deltoid detachment. A limited resection of the anterior hook would he more appropriate in these cases (Fig. 10-2).

Figure 10-2. In cases with a very thin and curved acromion, a limited resection of the anterior hook is more appropriate.

Special Instruments

1. An arthroscopic eIectrocautery/ablation device is strongly recommended in the subacromial space to control hemorrhage, improve visualization, and aid in removal of soft tissue.
2. A high-torque bone-cutting burr greatly facilitates anterior acromial resection.
3. Anesthetic Options: General anesthesia. Scalene block.

Patient and Equipment Position

1. Lateral decubitus.
2. Anesthesia anterior to the abdomen for 180-degree surgical access to the superior shoulder with careful axillary and peroneal padding.
3. Arm abducted 30 degrees and flexed 10 to 15 degrees with 7 to 15 pounds of distraction, depending on the patient’s body habitus.
4. Patient rolled back 25 degrees to get the plane of the glenoid parallel to the floor.
5. Beach chair position (alternative)

Surgical Approach

1. After an exam under anesthesia and a thorough arthroscopic glenohumeral exam from both a standard posterior and high anterior approach, the scope is removed and redirected at a 15-degree caudad angle to the acromion. The scope is placed far enough anteriorly (under the anterior one half of the acromion) to enter the bursal chamber that is distended.
2. With scope and flow posterior and outflow through anterior cannula (placed through previous high anterior portal with Wissinger rod), a lateral working portal is established 3 to 4 cm from the lateral border of the acromion, slightly anterior to the midpoint of the acromion and directed slightly upward so the shaver/ablator does not impinge on the lateral cortex.
3. Define anterior one half of the bony acromion with shaver and cautery/ ablation from the lateral portal. Ablate or transect the coracoacromial ligament with the cautery unit or shaver and resect the anterior 3 to 4 mm of acromial bone from the anterolateral corner to the AC joint with burr. Also thin down the lateral border of the anterior one half of the acromion tapering posteriorly (Fig. 10-3). Eighteen-gauge needles at the anterolateral corner and AC joint aid in orientation.


Figure 10-3. Remove the anterior 3 to 4 mm of acromion from the anterolateral corner to the AC joint. Thin down the lateral border of the anterior one half of the acromion, tapering posteriorly. (HH=humeral head, Ac=acromion, CL=clavicle, Co=coracoid.)

4. Place scope in lateral portal to view arch of acromion and introduce burr through posterior portal directly on undersurface of posterior one half of the acromion. Using this as a “cutting block” the burr is advanced anteriorly with a sweeping motion medially to laterally (Figs. 10-4)


Figure 10-4. The burr is advanced anteriorly using the posterior half of the acromion as a cutting block to remove the bone with a sweeping motion medially to laterally.

5. The anterior hook of the acromion is resected and the undersurface flattened in AP plane (Figure 10-5). Take care not to advance the burr anteriorly into deltoid fibers or fascia (by sweeping more medially after flattening the acromion, the inferior portion of the clavicle can be excised if one desires to perform a concomitant Mumford distal clavicle resection).


Figure 10-5. The anterior hook of the acromion is resected and the undersurface flattened in the AP plane.

6. The scope is then placed posteriorly to view the acromion and ensure it is flat in the medial-lateral plane (Fig. 10-6). One can also view a burr from an anterior AC portal, resecting the superior remaining clavicle while performing a Mumford.


Figure 10-6. The scope is placed posteriorly to view the acromion and ensure that it is flat in the mediolateral plane.

7. The flow pressure is reduced and hemostasis obtained with the electrocautery unit.

Postoperative Care and Rehabilitation

1. A simple absorptive sterile dressing is applied to the skin with foam tape and ice is used intermittently for 36 hours. Immediate active and passive range of motion and daily activities are allowed as tolerated, with sling usually not utilized unless associated cuff repair performed.
2. Scapular stabilization and cuff exercises arc instituted at week 1.

Tips and Pearls

1. Take care to keep the burr tightly on the undersurface of the posterior one half of the acromion as one comes forward on the “cutting block.” If portal is too low or soft tissue gets interposed posteriorly, the burr may falsely angle upward, resulting in excess anterior bone resection and risking subsequent acromial fracture or deltoid detachment (Fig. 10-7).


Figure 10-7. Keep the burr flat against the undersurface of the posterior acromion to avoid incorrect resection angle.

2. Resect 3 to 4 mm of anterior acromial bone from the anterolateral corner of the acromion to the AC joint and taper back along the lateral aminion from the lateral portal before placing the burr posteriorly to use the “cutting block.” This clearly outlines the bony anatomy, improves visualization, and lessens the potential for inaccurate resection (Fig. 10-3)
4. If the AC joint is asymptomatic preoperatively and has no inferior osteophytes or degenerative changes on X-ray, an effort should be made not to violate the inferior capsule or joint as this may destabilize the joint and a percentage of these may become symptomatic postoperatively. If the AC joint is degenerative or has prominent inferior osteophytes, then beveling the inferior tip of the clavicle (co-planing) or arthroscopic distal clavicle resection (Mumford) is appropriate.

Suggested Readings

• Gartsman GM. Arthroscopic acromioplasty for lesions of the rotator cuff. J Bone Joint Surg Am 1990;72:169-180.
• Gerber C. Terrier F, Ganz R. The role of the coracoid process in the chronic impingement syndrome. J Bone Joint Surg Br 1985;B7:703-708,
• Jobe KW, Kvitne KS, Giangarra CE. Shoulder pain in the overhand or throwing athlete: the relationship of anterior instability and rotator cuff impingement. Orthrop Rev 1989;18:963-975.
• Neer CS. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. J Bone joint Surg Am 1972:54:41-54.
• Sampson TG, Nisbel JK, Glick JM. Precision acromioplasty in arthroscopic subacromial the decompression of the shoulder. Arthroscopy 1991;7;301-307.
• Walch G, Boilean P, Noel E, Donell ST. Impingement of the deep surface of the supraspinatus tendon on the posterior or superior glenoid rim: an arthroscopic study. J Shoulder Elbow Surg 1992;l:238-245.

The technique of arthroscopic subacromial decompression (ASAD) and distal clavicle resection has become an increasingly common procedure for dealing with impingement and acromioclavicular (AC) joint disease. Many surgeons are now routinely combining these arthroscopic decompression techniques with either mini-open or, more recently, completely arthroscopic repair of rotator cuff tears. As with other open operations that have evolved arthroscopically, the learning curve for these procedures is significant and should not be underestimated.

Complications associated with shoulder arthroscopy in general are low. Small, in his 1986 study [1], found a complication rate in subacromial space surgery of 0.76%. However, the complication rate with anterior staple capsulorraphy was 5.3%. The rates excluded clinical failures. In his follow-up study in 1988 [2,3], reporting on complications relating to arthroscopy performed by experienced arthroscopists, the complication rate with shoulder arthroscopy was 0.7% overall, again with the highest rate in anterior capsulorraphy.

Curtis et al. [4] reviewed 711 shoulder arthroscopies and found an overall complication rate of 6%. Of the 43 complications, 19 were secondary to postoperative stiffness, six secondary to transient neurologic symptoms, five associated with wound hematomas, and six associated with bruising. One patient each had problems with hardware removal, reflex sympathetic dystrophy, laceration of the cephalic vein, pulmonary embolus, and painful posterior portal, corneal abrasion, and heterotopic bone. The rate increased from 4.5% for arthroscopic procedures to 8.0% for combined arthroscopic and open surgery (i.e., mini-open cuff repair or stabilization).

Several of the complications associated with shoulder arthroscopy are related to arthroscopic technique in general and are common to other joints that are arthroscopically examined [5]. In a survey sent to arthroscopy association members of the shoulder study group, however, some procedure-specific complications were also identified [6]. This chapter identities some of the difficulties inherent in these arthroscopic techniques and provides some suggestions for precautions and modifications that may help in their avoidance.

TECHNIQUE-RELATED COMPLICATIONS

Neurologic
For the most pant, neurologic complications have been associated with the lateral decubitus position for shoulder arthroscopy (Fig. 12-1). Neuropraxia involving traction injury to the brachial plexus may be secondary to the traction weight, direction of pull, and duration of the surgery. Five to 10 Ibs of distal traction is usually adequate for the average patient, and 15 Ibs is reserved for larger or well-muscled individuals. Increasing the weight to 20 Ibs or more, as was initially done in shoulder arthroscopy, results in changes in the somatosensory-evoked potentials of the musculocutaneous, median, ulnar, and radial nerves, with the musculocutaneous being the most sensitive at all arm positions and traction weights [7].

In a cadaver study, Klein et al. [8] demonstrated the greatest brachial plexus strain with the arm at 70° abduction and 30° of forward flexion. The minimum overall strain was noted at 90° of flexion and 0° of abduction, but this resulted in poor visualization. They recommended positions of 45° of forward flexion and either 0° or 90° of abduction, depending on the intra-articular region of interest.

Figure 12-1. The lateral decubitus position (solid) with necessary padding and support, and the dual traction technique (dotted) with the same padding and 7-10 lbs lateral distraction.

Dual traction as described by Gross and Fitzgibbons [9] (see Fig. 12-1) with low distal traction weights on a minimally abducted arm coupled with a laterally directed distraction force appeared to be associated with less compromise to somatosensory-evoked potentials in Pittman et al.’s study [7]. Gross and Fitzgibbons [9] also recommended rolling the patient back about 25° to 30° to orient the glenoid joint surface parallel to the floor. The rollback position coupled with 15° of additional flexion of the arm puts the direction of pull into Klein et al.’s safer zone [8]. No work has been specifically directed at determining the neurologic effects of the laterally directed distraction force in this set-up, but no reported complications have been associated with this type of traction.

For arthroscopic surgery in the subacromial space, minimal abduction (15° to 25°) and 15° of flexion from the rollback position opens up the space and yet does not put excessive strain on the brachial plexus. Excessive forward flexion of the arm brings the tuberosity into contact with the anterior acromial hook, making exposure difficult.

Careful attention needs to be given to the position of the head, which should be as close to exactly neutral as possible. Any sagging of the head down and away from the operative arm increases the strain on the brachial plexus. Overcompensation and excessive propping of the head away from the “down” arm can result in the opposite brachial strain. Careful padding and wrapping of the traction device at the wrist are necessary to avoid compression injury to the sensory branch of the radial nerve with resultant thumb numbness. Moreover, careful padding of the ulnar and peroneal nerves on the downside is necessary [10]. Time in traction is also a factor, and conversion to an open operation is recommended if the operation is extending past 2 hours or if distention is becoming severe.

The beach-chair position alleviates most of the neurologic concerns already stated [11], but careful positioning and support of the head are still necessary. A case of hypoglossal nerve injury has been reported with this position [12]. Exposure in the subacromial space, however, may be diminished because of loss of distraction. The dual traction technique is not possible with this position.

Anesthetic
General anesthesia provided to the patient in the lateral decubitus position appears safe relative to hypotensive and neurologic problems, so long as proper padding has been established. Interscalene nerve blocks are commonly used for either intraoperative anesthesia or additional postoperative pain relief. A temporary ipsilateral phrenic nerve palsy routinely results from this block but rarely causes pulmonary problems except in patients with preexisting pulmonary insufficiency [13,14].

Esch and Baker [15], however, reported on two patients requiring ventilatory support after interscalene block for ASAD. The anesthesia literature documents various relatively significant complications with interscalene blocks, including bilateral spread affecting both phrenics; complete spinal, bilateral cervical, and thoracic epidural blockade; prolonged Horner’s syndrome; auditory disturbance; and cardiac arrest [16-22]. Pneumothorax caused by incorrect needle placement has also been reported [23]. Complications associated with interscalene block appear to be more common when the block is performed after induction of a general anesthetic as opposed to when the patient is awake and a nerve stimulator has been used.

PORTAL PLACEMENT

Direct nerve injury can be associated with incorrect portal placement.

Posterior Portals
The traditional posterior portal as described by Andrews et al. [24] has become the standard position for the initiation of glenohumeral and subacromial arthroscopy. This penetrates the so-called soft spot approximately 1 cm medial and 1 to 2 cm inferior to the posterolateral corner of the acromion. The arthroscope should enter the joint approximately in the interval between the infraspinatus and teres minor muscles. This portal passes through the deltoid, ranging from 2 to 4 cm from the axillary nerve and the posterior humeral circumflex artery, and lies approximately 1 cm lateral to the suprascapular nerve and artery.

Inferior medial migration of this portal as described by Wolf [25] for the central posterior portal or inferior lateral migration for his modified posterior portal [26] places these structures at greater risk. Directing a blunted conical trocar toward the coracoid process provides some increased margin of safety for these posterior portals. Sharp trocars should generally be avoided for shoulder arthroscopy because of the increased risk of neurologic and chondral damage.

Anterior Portals
Several anterior shoulder arthroscopic portals have been described [24,25,27-30]. The anterior superior portals as described by Andrews et al. [24] and Wolf [25,26] and the superolateral portal described by Laurcncin et al, [30] are neurologically safe and most useful for subacromial surgery. They are also readily used to provide an anterior viewing portal for glenohumeral work. The central anterior portal in the superior recess above the subscapularis tendon as described by Matthews et al. [27] also appears to be safe relative to neurovascular structures. As the surgeon moves inferior to the tip of the coracoid process, the risk to neurovascular structures increases. These portals as described by Wolf (anterior-inferior portal) [25], Resch el al. [28], and Davidson and Tibonc [29] (anterior-inferior transubscapular) are more useful for arthroscopic instability surgery and are not generally used for subacromial or rotator cuff work (Fig. 12-2).

.

.

Figure 12-2.
External (A) and arthroscopic (B) views of the anterior portals, including the superolateral [30], anterior-superior [25], anterior [24], central anterior [27], anterior-inferior [25], and anterior-inferior trans-subscapular [28, 29] portals.

Superior Portal
The supraclavicular fossa portal was devised by Neviaser [31]; it allowed placement of an additional inflow portal at the posterior superior aspect of the joint, as well as access for superior instrumentation. The suprascapular nerve and artery lie deep and on the inferior surface of the supraspinatus muscle, approximately 2 cm medial to the path of the cannula. Too vertical a passage can injure the suprascapular nerve and artery; too lateral a passage can injure the rotator cuff tendon, particularly if the arm is abducted more than 30° [32]. This portal is no longer routinely needed or used, particularly for subacromial work (Fig. 12-3).

Subacromial Portals
Multiple subacromial portals have been described for decompression and for AC joint and rotator cuff surgery. These include the traditional posterior portal with angulation of the arthroscope or instrument superiorly into the subacromial bursa, the posterolateral portal [33], the central lateral portal [34], the anterolateral portal, the anterior and posterior AC joint portals [35], and the accessory high portals for anchor placement in rotator cuff surgery (see Fig. 12-3).

Figure 12-3. Subacromial and superior portals, including the posterior 24, posterolateral 33, central lateral 34, 50, anterolateral 33, superolateral 30, anterior-superior 25, anterior and posterior acromioclavicular (AC) 35, and superior 31 portals. Dotted line indicates course of axillary nerve 5cm lateral to the acromial edge.

The neurologic structure most at risk with the use of these portals is the axillary nerve, which traverses the underside of the deltoid muscle approximately 3 to 5 cm from the acromial margin. If the surgeon keeps the skin incision less than 5 cm from the acromion and directs the trocar toward the subacromial space, as opposed to directly down through the deltoid muscle, axillary nerve problems should be avoided [36]. These portals are best set up after preliminary placement and direct visualization of an 18-gauge needle to ensure the proper orientation for shaving or anchor placement.

Vascular
Problems related to hypotension have been associated with arthroscopy done with the patient in the beach-chair position, especially in elderly or hypertensive patients. Adequate fluid replacement and compression leg stockings may be beneficial to avoid premature termination of the procedure or switching to a lateral decubitus position. Although deep venous thrombosis is rare, it has also been reported with shoulder arthroscopy [37].

Likely, the most common vascular complication with subacromial surgery is bleeding. Because the subacromial area is extensively traversed by veins, frequently inflamed, and not a closed space, bleeding is more troublesome here than at almost any other arthroscopic site. Failure to control bleeding and to maintain visualization and orientation are common sources of complications in subacromial surgery. Use of electrocautery is strongly recommended. Strategies currently used for the control of bleeding include:

• Inject 0.25% bupivacaine with epinephrine into the portals (2 ml) and subacromial space (10 mL) at the beginning of the procedure.
• Incise only the skin to avoid deeper muscle laceration.
• Use a blunted conical trocar for penetration of muscle, joint, and subacromial space.
• Add epinephrine, 10 ml (1:1000) per 3-L bag to only the first irrigation bag.
• Avoid debridement of anterior medial acromion and the undersurface of the AC joint until late in the case.
• Use electrocautery immediately when significant “bleeders” are encountered.
• Increase inflow with large-bore sheath at level of the arthroscope. A pump with independent control of pressure and flow rate is helpful.
• Decrease outflow to maintain pressure. Control suction on shavers and burrs to reduce “red-out.” Integrated fluid delivery and shaver systems are helpful for this problem.
• Reduce blood pressure, if the patients’ medical condition allows, to maintain systolic pressure of less than 95 to 100 mm Hg.
• Increase pressure on pump or elevate bags to level at which bleeding is well controlled.

Pulmonic
Pneumothorax is a known complication associated with interscalene block anesthesia [23]. There have been rare cases of subcutaneous emphysema, pneumomediastinum, and potentially life-threatening tension pneumothorax associated with arthroscopic decompression [38].

Soft-Tissue Injury
Skin burns have been reported with shoulder arthroscopy if a noninsulated cautery tip is used with conductive solution. This problem can be avoided if the surgeon uses an insulated tip, or newer bipolar devices for ablation and cautery. These tips can be used safely even in conductive solutions such as normal saline or lactated Ringer’s solution.

Sterile water, which was used early on because of its nonconductivity, is injurious to soft tissues. Scattered reports exist of skin and muscle necrosis associated with extremely long procedures using water as an irrigating solution. Glycine (1.5%), used in urologic procedures, and less frequently as an arthroscopic medium, has been associated with transient blindness and is no longer recommended [39].

Extravasation and distention of the soft tissues with saline or lactated Ringer’s solution may sometimes produce alarming appearances. Studies have shown, however, that the intramuscular pressures rapidly return to normal at the end of the procedure [40,41]. The effect of soft-tissue distention on the nerves surrounding the shoulder has not been well-documented.

Infection
The infection rate resulting from arthroscopy in general is very low. Johnson et al. [42] reported less than one infection in 2000 new arthroscopies when using 2% glutaraldehyde as a sterilizing agent. Only four infection cases with shoulder arthroscopy have been noted in the literature to date [1,15,43].

Glutaraldehyde solution has been commonly used for instrument sterilization, especially in the outpatient setting. However, instruments must be thoroughly rinsed before use. Even trace amounts (such as may be found in arthroscopic rinse baths) can induce a severe synovial inflammatory reaction [44]. Because of this and because of concerns regarding HIV transmission through the use of glutaraldchyde, sterilization is increasingly being performed by automated sterilization units such as the Steris (peracetic acid; Steris Co, Mentor, OH) [45] or Sterad (gas plasma with hydrogen peroxide;
J & J Medical, Arlington, TX) [46].

Equipment Failure
The potential for an equipment failure increases with the complexity of the procedure. Cannulated suture hooks and punches, various suture retrievers, linear punches, and grasping forceps can break off in the joint. Keeping a retrieval instrument, such as the magnetic Golden Retriever suction device (Instrument Makar, Okemos, Ml), handy can considerably simplify recapture of metallic pieces.

PROCEDURE-RELATED COMPLICATIONS

Arthroscopic Subacromial Decompression
Complications of ASAD include 1) variable bone resection, 2) deltoid detachment, 3) heterotopic bone, and 4) residual coracoacromial ligament (CAL) snapping.

Variable Bone Resection
Variable hone resection is probably the most common complication of ASAD. Both inadequate decompression and excessive resection have been reported. Wolf [47] reviewed 35 patients with failed previous arthroscopic surgery of the shoulder. Of these patients, 60% failed because of previous inadequate ASAD; 20 of 21 had complete recovery after further ASAD [47]. Matthews et al. [27) and Esch [48] have reported on both acromial and clavicular fractures secondary to excessive resection.

Inaccurate decompression is usually secondary to inadequate preoperative planning with or without poor visualization and orientation during the procedure.

Preoperative Evaluation
Outlet and axillary views are key to evaluating the acromion. The outlet view is used to determine the shape of the acromion (type I, II, or III) and the overall thickness [49,50]. Rockwood and Lyons [51] have described a modified anterior shoulder view that, although helpful in making the diagnosis of impingement, is not beneficial in terms of preoperative planning. On the outlet view, two lines are drawn on the undersurface of the acromion – the first from the front tip of the acromion to the posterior edge, and the second along the posterior half of the under-surface of the acromion extending out anteriorly. The distance between these two lines at the anterior margin approximates the amount of undersurface anterior bone that will be resected (Fig. 12-4).

Figure 12-4. Preoperative determination of bone resection shown on an outlet-view radiograph. CAL - coracoacromial ligament. Shaded area between dotted lines denotes bone resection.

The axillary view is used to determine the shape of the acromion (cobra-shaped vs. square-tipped), as well as to determine whether there is any “anterior acromial protuberance” [52] anterior to the level of the AC joint (Fig. 12-5). This approximates the amount of bone that will be removed anteriorly in addition to the amount of bone that will be taken from the undersurface.

Figure 12-5. Preoperative evaluation (axillary view) of anterior acromial protuberance and the amount of resection. Shaded area between dotted lines denotes bone resection.

After these measurements have been determined, the two-portal technique of acromioplasty makes it relatively simple to reproduce this resection. It is difficult to obtain a flat acromion when visualizing only from the posterior portal because of the amount of curving away of the acromion from the arthroscope . The acromion may appear flat from medial to lateral and front to back, but may still have a considerable anterior-to-posterior concavity when later viewed from the lateral portal. Placing the arthroscope laterally and then bringing the shaver forward from the posterior portal using the posterior half of the acromion as a “culling block” [53] helps ensure a straight, flat cut in the sagittal plane. This technique reliably converts a type II or type III acromion to a type I flat surface as demonstrated on postoperative radiographs (Fig. 12-6). The surgeon should be sure to subsequently replace the arthroscope posteriorly and to confirm flatness of the acromion in the medial to lateral plane. The anterior lateral acromial comer is often difficult to visualize from the lateral portal. Good visualization from both portals assures a flat, smooth surface.

Figure 12-6
(A) Preoperative templating for arthroscopic subacromial decompression (ASAD) on outlet- view radiograph. Dolled line indicates correct line of bone resection.
(B) Postoperative radiograph of ASAD.

The surgeon should beware of the thin curved type acromion (type C) [50]. If, on the outlet view, a very thin or curved acromion is found, the cutting block line on the undersurface of the posterior half of the acromion may actually exit from the superior aspect of the acromion, taking off too much anterior bone (Fig, 12-7A) . In such cases, the cutting block technique would be inappropriate. In this situation, the original resection technique as described by Ellinan [33] is more applicable, that is, removing only a small anterior hook and not producing a type I flat acromion (Fig. I2-7B).

Figure 12-7.
Preoperative (A) and postoperative (B) radiographs of decompression on the thin, curved acromion. Dotted line in (A) indicates excessive bone resection with cutting-block technique. Postoperative radiograph demonstrates more conservative anterior resection with significant increase in anterior acromial humeral distance.

Inadequate Visualization
This finding is usually secondary to excessive bleeding (which can be managed as previously outlined), poor localization of the subdeltoid bursa, or inadequate debridement of the subacromial space. Remembering that the bursa is an anterior structure, the surgeon should make every effort when in the subacromial space to direct the arthroscope into what Wuh and Snyder [50] termed the room with a view. Time and care should be spent at the beginning of the procedure, debriding the bursitis and the thickened periosteum on the undersurface of the anterior half of the acromion. Some of the posterior bursal curtain may need to be resected to clearly visualize the bony architecture. Debridement can be done with a shaver-burr, or a cautery-ablation system, but the surgeon should be sure to stay on the acromial bone and not deviate into the deltoid fibers. Debridement should be performed from the anterior lateral corner of the acromion toward, but not into, the AC joint, and then posteriorly along the lateral edge of the acromion. Spinal needles are used in the anterior lateral corner and the AC joint to gain better clarification of the bony landmarks.

A burr should next be used to resect 3 to 4 mL of bone, again along the anterior margin of the acromion from the anterior lateral corner to the AC joint, then tapering posteriorly along the lateral edge of the anterior half of the acromion. This improves orientation and visualization when the arthroscope is placed in the lateral portal and the shaver is brought in posteriorly. The surgeon should not resect too much anterior bone – only enough to make it easy to delineate the anterior edge of the acromion as seen from the lateral portal. The surgeon should let the shaver from the posterior portal resect most of the bone, coming forward in a smooth, controlled, flat cut (Fig. 12-8)The amount of bone resected is easy to determine by comparing the anterior remaining ledge with the thickness of the burr.

Figure 12-8
Serial intraoperative views of arthroscopic subacromial decompression of the right shoulder.
A) Conservative anterior resection from the lateral portal with the shaver tip in the coracoacromial ligament.
B) Lateral view of the burr starting forward during cutting block resection.
C) Completed resection with flat acromial undersurface posterior to anterior and intact deltoid fascia.

The posterior portal (through the deltoid muscle) must be at the inferior edge of the acromion, and not further below with soft-tissue interposition, so that the shaver does not angulate superiorly in an excessive or artificial manner (Fig. 12-9). Although the same placement of posterior skin incision is used for both glenohumeral and subacromial arthroscopy, the burr needs to puncture the soft tissues right at the inferior edge of the acromion for successful two-portal cutting-block technique.

Figure 12-9A
Although the same skin incision is utilized for both the glenohumeral and subacromial examinations, the trocar penetrates the deeper soft tissues at different levels, so the shaver can be closely applied to the undersurface of the acromion.
Figure 12-9B
If portal or soft-tissue penetration is too inferior, the burr will angulate too far superiorly and excess resection will occur.

Deltoid Detachment
Deltoid detachment results from overly aggressive resection at the anterior aspect of the acromion. If no significant anterior acromial protuberance is seen on the axillary radiograph, then simply flattening the undersurface of the acromion will adequately decompress it.

When a protuberance does exist, it usually is an extension of calcification interiorly into the CAL. Resecting the ligament and the contained bone with subsequent flattening of the acromion will usually eliminate the anterior overhang. Routinely resecting 8 to 10 mm of full-thickness anterior bone (as described for open procedures [51]) from the lateral portal puts the deltoid attachment at significant risk. This damage cannot subsequently be repaired unless the shoulder is then opened. The surgeon should take a small amount of anterior bone from the lateral portal and the bulk of the bone from the posterior portal using the cutting-block technique, thus teasing the bone off anteriorly from the fascia. Deltoid detachment, either open or closed, is arguably the most devastating complication of shoulder surgery and should be avoided [54].

Heterotopic Bone
This finding has been reported to be associated with both acromioplasty and AC resection [55,56]. In the 10 cases reported by Berg et al. [55], eight developed recurrent impingement symptoms, with an apparent strong correlation with active spondylitic arthropathy or a profile of hypertrophic pulmonary osteoarthropathy – male, obese, smoker with chronic pulmonary disease. They recommended prophylactic measures (indomethacin or radiotherapy} with these two types of patient groups. The surgeon should also unplug clogged shavers and burrs (or use an accessory gravity drainage portal) to avoid debris (“clouds of snow”).

Coracoacromial Ligament
Continued snapping with abduction and rotation maneuvers from an inadequate resection and a rescarring of the CAL do occur occasionally. After bony decompression has been completed, another 5 to 10 mm of ligament can be resected using a shaver, basket punches, or an ablation device. This is especially appropriate if snapping of the biceps tendon or bursal fold on the CAL is an identifiable preoperative complaint. Partial release of the anterolateral band alone may be curative in some athletes engaged in overhead throwing maneuvers |57]. Care should be taken to avoid excessive release of the lateral extension of the ligament along the lateral edge of the acromion. The ligament and deltoid fascia are intimately connected at this location, and release risks the deltoid attachment [58-].

Resection should not be done in the presence of significant degenerative arthritis of the glenohumeral joint or cuff arthropathy with a massive cuff tear, or if future arthroplasty is contemplated [59].

Arthroscopic Distal Clavicle Resection
Thorough clinical and radiologic evaluation of the AC joint should be performed prior to decompression. Significant inferior osteophytes should be noted on the anteroposterior view, and narrowing and sclerosis (degenerative joint disease) or widening and cystic changes (osteolysis) should be noted on the anteroposterior and axillary views. Differential injection into the AC joint instead of into the subacromial bursa may be necessary to confirm AC involvement.

Depending on the findings listed above, a decision must be made preoperatively (if possible) regarding the AC joint and distal clavicle. The surgeon must decide whether to 1) leave the AC joint untouched, 2) bevel the distal clavicle, or 3) perform an arthroscopic distal clavicle resection.

Most early descriptions of ASAD recommended routine beveling of the distal clavicle [33,60]. However, this practice destabilizes the AC joint to a certain extent by resecting the’ weaker inferior ligaments. The author has seen two patients in his own practice (and anecdotal reports from others) who, after decompression and beveling, developed AC joint pain necessitating later distal clavicle resection. Prior to surgery, these patients appeared clinically and radiographically to have normal AC joint.

If there are significant inferior osteophytes off the clavicle, then there is likely already compromise of the inferior AC ligaments and enough direct irritation of the underlying cuff to warrant beveling the tip. As the beveling is performed, downward pressure on the clavicle will bring some of the articular surface into view. If it appears significantly arthritic, then a complete resection of 1.0 lo 1.5 cm of clavicle should be performed.

However, in patients with AC joints appearing normal on preoperative clinical and radiographic examinations, the author no longer routinely bevels the clavicle; instead, the medial acromial bone is leased off the capsule and cartilage, much as is done with the deltoid fascia during decompression.

Other complications associated with distal clavicle excision relate to )) heterotopic bone formation, 2) inadequate resection, 3) underlying muscle injury, and 4) excessive bleeding. Incomplete resection of the superior cortical bone during distal clavicle resection is not uncommon. Clear visualization of this area using either a 50° or 70° arthroscope is necessary to remove all the superior bone (Fig. 12-10).

Figure 12-10
A) View from the posterior portal looking up at the acromioclavicular (AC) joint (arrowhead) with the inferior half of the distal clavicle already resected from the right shoulder.
B) Posterior view of the AC space with the distal clavicle resected and two spinal needles placed externally to measure the distance between the clavicle tip and the medial edge of the acromion (right).
C) Lateral view of the clavicle resection with the posterior and superior ligaments intact (arrow).

If a conical eggshell of bone is left behind, elevation or cross-chest maneuvers by the patient will remain painful. The bone will also serve as a nidus of heterotopic hone formation (Fig. 12-11).

Figure 12-11
Heterotopic bone formation after distal clavicle resection (right shoulder).
A) Six month follow-up radiograph showing early heterotopic nidus.
B) Two-year postoperative radiograph demonstrating mature bone in the AC interval.

The optimal amount of bone to be removed arthroscopically from the tip of the clavicle remains unresolved. If the superior and posterior AC ligaments are well maintained with the resection, the length of clavicle 10 be removed can be reduced [61 ]. If the superior and posterior ligaments are violated, however, then the remaining tip of the clavicle becomes more unstable, and further resection is needed [62,63«|. Studies suggest that 1 lo 1.5 cm of bone resection would be adequate with use of the arthroscopic technique (Fig. 12-12); 1.5 cm of bone should be resected if the posterior-superior ligaments have been compromised.

Figure 12-12
Preoperative (A) and postoperative (B) radiographs of the acromioclavicular resection (right shoulder).

Care should be taken to measure the distance between the clavicle and the acromion with two 18-gauge spinal needles placed parallel through the skin from above. This should be performed at both the anterior and posterior aspects of the clavicle (see Fig. 12-10B). It is easy to obtain an uneven gap in resection with more bone removed anteriorly than posteriorly, which should he avoided.

Caution should be taken when using unhooded burrs to resect the tip of the clavicle because it is very simple to wrap up the soft underlying cuff musculature in the instrument. The author prefers to use a well-hooded burr with the open side always either facing up or in, toward the cancellous middle of the clavicle. Suction should be low, just sufficient to clear debris.

Vascularity around the tip of the clavicle and AC joint is plentiful. Cauterization of the fat pad beneath the AC joint before debridement is helpful. t is also beneficial to outline the tip of the clavicle frequently with the cautery device when it is being resected medially because periosteal vessels are numerous.

Arthroscopic Rotator Cuff Repair
The rotator cuff should be thoroughly evaluated arthroscopically both from the articular and bursal sides. Partial tears are usually well-managed with limited debridement and ASAD. Excessive debridement of partial tears can lead to complete rotator cuff tears if caution is not exercised. Evaluation is aided by placement of “suture markers” – an 18-gauge needle placed from a superior position through the cuff and into the joint with a #1 monofilament suture grasped in the joint and brought out through the anterior portal as the needle is removed. This allows the investigator to closely examine the exact area on the bursal surface of the cuff that corresponds to the torn area on the articular side. Nearly complete tears that will not heal with adequate strength should he completed and repaired [64|. Several clinical studies have demonstrated that repair of rotator cuff tears in conjunction with ASAD fares better in the long run when compared with simple debridement and decompression [52,64,65].

Failure of fixation of rotator cuff repair is a common problem with both open and arthroscopic repair. This may be due to mechanical factors, biological factors, or both.

Mechanical Considerations
Several factors related to technique can affect the mechanical strength of rotator cuff repair and increase the likelihood of success. Anchor fixation into bone can be improved by roughening the area of the tuberosity widely to increase the surface area for cuff repair, while decorticating lightly. Creation of deep troughs in the soft cancellous bone lead to anchor pull-out (or tunnel breakage during open techniques). St. Pierre et al. [66] demonstrated good healing in animal studies without the need of a deep trough.

Inserting the anchor at about a 45° angle to the direction of pull (Burkhart’s “deadman’s angle”) [67] results in increased resistance to pull-out and puts the anchor under the stronger subchondral bone medially. Recent studies also suggest that simple suture may be stronger than mattress sutures in the fixation of tendon to bone in the rotator cuff area [68].

With the 45° “deadman’s angle” approach to the bone, the suture is pulled at an acute angle, with repetitive tension over the medial lip of the anchor hole. If the edge is too sharp, fraying and breaking of the suture may ensue. If the initial drill has a slight bevel at the stop point or if the hole is subsequently chamfered, the results of this problem may be diminished.

Biologic Considerations
The vascular involvements of rotator cuff repairs in older patients are always in question. Factors that may affect the blood supply to the repair should be kept in mind. Debriding the edges of a rotator cuff back to bleeding tissue stimulates an acute healing response.

Reducing tension on the rotator cuff repair in its early healing phase improves circulation and healing potential. This reduction can be accomplished by fixing small tears where they appear (i.e., more medially than the normal tuberosity attachment). Burkhart has described the principle of “margin convergence” [69] in the reduction of tension on rotator cuff tissue and repairs. By repairing the larger tears with side-to-side sutures medially and then working laterally to fix the remaining Y-shaped or L-shaped tissue to bone using anchors, tension on the repair and susceptibility to anchor pull-out are reduced. This appears to be a valid principle in the author’s practice.

The larger the tear, the more beneficial an abduction pillow may be to improve blood flow to the “critical zone” and again reduce tension on sutures. Careful monitoring of postoperative rehabilitation is essential. The goal is to protect the repair and to avoid development of excessive scar tissue formation in the subdeltoid space – a “captured shoulder,” as described by Mormino et al. [70]. Passive motion is less stressful on the repair in the early phases. Debate exists as to when to allow active abduction; this decision should be influenced by the size, pattern, and vascularity of the tear, as well as the stability of fixation.

Incorrect Diagnosis
Symptoms that persist despite adequate decompression or distal clavicle excision may be secondary to incorrect diagnosis. Decompression in a patient with secondary impingement from underlying anterior instability may often be unsuccessful until the underlying instability has been addressed. Posterior superior impingement is not likely to respond to anterior decompression. Underlying glenohumeral arthritis in weightlifters may negate the beneficial effects of distal clavicle excision for osteolysis. Suprascapular nerve syndrome must be diagnosed using specific neurologic modifications of standard electromyographic technique. A high index of suspicion for this entity must be maintained. Radicular cervical disease, metastatic carcinoma of the scapular neck, Pancost’s tumors of the lung, and referred pain to the shoulder from visceral structures are also part of the differential diagnosis. Postoperative pain associated with a cracking sensation is most likely secondary to a fracture of the acromion.

Norwood and Fowler [71] reported on four cases of recurrent symptoms after technically well-performed shoulder arthroscopy, secondary to persistent cuff tears. These appeared to be related to inadequate healing on the articular side of the tendinous portion of the cuff at the posterior portal site. Because larger cannulae are now being used routinely, this problem may become increasingly noted, both anteriorly and posteriorly. If persistent or recurrent pain and weakness occur after arthroscopy, repetition of the arthrogram may be worthwhile. If results are positive, an open repair is likely to be beneficial.

Inadequate Surgical Preparation
Surgical preparation entails not only physician training, preoperative planning, and equipment requirements, but also patient education. Many patients have unrealistic expectations as to the results that arthroscopic surgery can accomplish relative to the shoulder. Education about soft-tissue healing times and scar tissue maturation should help temper unwarranted enthusiasm and activity. Because pain associated with arthroscopic procedures is often reduced, careful monitoring of postoperative activity, especially with rotator cuff repair, is necessary.

Physician preparation is mandatory for successful surgical results. Training at meetings and cadaver laboratories, such as the Orthopedic Learning Center (Chicago, IL), is prudent before attempting new techniques in one’s practice. These procedures are equipment intensive, and a step-wise progression from open to mini-open to arthroscopic technique is recommended.

CONCLUSION

Arthroscopic subacromial decompression, distal clavicle excision, and rotator cuff repair are demanding operative procedures. It is hoped that diligent preoperative planning and intraoperative attention to the possible complications presented will increase the potential for successful surgical outcomes.

REFERENCES AND RECOMMENDED READING

Recently published papers of particular interest have been highlighted as:

* Of Interest
** Of Outstanding Interest

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60. Discusses the anatomic differences between the anterior and the lateral insertion of the coracoacromial ligament and the deltoid fascia and their pertinence to decompression technique.
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66. Demonstrates the importance of the posterior and superior acromioclavicular ligaments for stability.
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69. * St. Pierre P, Olson FJ, Elliott JJ, et al.: Tendon healing to cortical bone versus a cancellous trough: a biomechanical and histological model in the goat. Presented at the 14th Annual Meeting of the Arthroscopy Association of North America. San Francisco, CA; 1995.
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