Arthroscopic Excision of the Acromioclavicular Joint
Excision arthroplasty of the acromioclavicular joint is a well-tried and tested procedure for degenerative change at this joint. Traditionally, via an open exposure, the outer centimeter of the clavicle is removed, and any osteophytes on the acromial side are also trimmed. This can also be achieved arthroscopically. One may be forgiven for thinking that this may be the triumph of technique over reason, or that this is how to make a simple job difficult. However, the arthroscopic method has certain distinct advantages.
Open excision arthroplasty is less successful in the young, when it is sometimes required secondary to injury with destruction of the articular cartilage. Open excision arthroplasty may lead to some mild loss of strength, but more importantly, an irritating horizontal instability. During open excision arthroplasty of the acromioclavicular joint, the integrity of the superior acromioclavicular ligament may be damaged. One function of this ligament is to prevent movement at the joint in the anteroposterior plane. If this ligament is not carefully reconstructed at the time of excision arthroplasty in the young, then an aching instability may ensue, following repetitive use above shoulder height. This problem is less noticeable in those over 45 years of age. Arthroscopic resection preserves the superior acromioclavicular ligament. Other advantages of the arthroscopic method are improved cosmetic appearance and less immediate postoperative pain.
The indications for arthroscopic excision of the acromioclavicular joint are the same as for open excision arthroplasty of the acromioclavicular joint:
- Symptomatic acromioclavicular osteoarthritis.
- Rotator cuff impingement secondary to degenerative change in the acromioclavicular joint, that is, with large inferior osteophytes causing secondary impingement.
- Symptoms interfering with activities of daily living, work, sports and recreation, unresponsive to conservative treatment for a minimum of 6 months.
The acromioclavicular joint could have been identified as the source of pain by the patient's history of localized injury or overuse. Physical examination with local tenderness, high painful arc, pain on stressing the acromioclavicular joint, and rehef of diese signs and symptoms by local anesthetic injection into the joint itself.
The diagnosis is essentially clinical, but confirmation of degenerative change in the acromioclavicular joint can be made with either plain radiographs or bone scan, in particular when the diagnosis is in doubt.
Position of Patient
The patient is positioned in the lateral position with the arm on traction as for gleno-humeral arthroscopy, with one small but important difference. Instead of directly on the side, the patient is rolled toward the operator, who is standing by the posterior aspect of the patient. This allows ease of maneuverability of the shaver anteriorly during resection of the joint.
The arthroscope is inserted through the standard posterior portal. First, a routine gleno-humeral arthroscopy is made to exclude any other source of shoulder pain and pathology. The arthroscope is then passed superiorly into the subacromial bursa, as described in Chapter 11 (Fig. 13-1).
The undersurface of the acromion is checked to make sure there is no obvious subacromial cause for the pain. The joint is then palpated from outside, and a direct anterior portal made 4 cm anterior to the joint. The shaver is passed through this anterior portal into the subacromial bursa and is directly visualized with the arthroscope (Fig. 13-2).
Initial visualization of the inferior surface of the acromioclavicular joint may be difficult because of bursal attachments and extra bursa fat in this region. The undersurface of the acromion is palpated 'with the shaver tip, and then bursa and soft tissue are cleared away from the undersurface of the joint. Bone is identified on the medial side of the acromion and resected with the notchplasty blade. The line of the joint can then be easily identified (Fig. 13-3). Occasionally, it may be necessary to pass a needle from superiorly outside the joint into the bursa to identify the exact line of the acromioclavicular joint, but this is usually unnecessary, because resection of the medial part of the acromion identifies the joint line fairly easily.
Bone is then resected from the -whole depth of the medial portion of the acromion, such that the whole of the lateral end of the clavicle is visualized. The outer centimeter of the clavicle is then removed with the power shaver, taking more bone inferiorly than superiorly and more bone posteriorly than anteriorly, because this is where any residual impingement may occur (Fig. 13-4). During this maneuver, the exact superior edge of the bone is easily identified from the overlying capsule and ligament, and hence every effort is made to preserve the superior capsule and ligament, to preserve stability in the excision arthroplasty
Alternative Procedure (in Conjunction With Acromioplasty)
Excision arthroplasty of the acromioclavicular joint is often required in conjunction with acromioplasty to decompress the anterior rotator cuff. In this case, the posterior portal is made first, the glenohumeral joint is inspected, and then the scope is passed up into the bursa via the posterior portal. A lateral portal is made initially, and the power shaver is used to complete the acromioplasty as described in the arthroscopic acromioplasty section (Fig. 13-5). At the end of the acromioplasty procedure, the acromioclavicular joint is easily delineated as the most medial margin of the acromion. With the power shaver still in the lateral portal, the inferior half of the lateral end of the clavicle is removed with the power shaver (Fig. 13-6). However, to complete the resection of the lateral end of the clavicle, the direct anterioral portal must be made. The acromioclavicular joint is palpated externally, and the anterior portal is made in direct anterior line with the acromioclavicular joint, 4 cm inferiorly. The shaver is then passed into the subacromial bursa under direct vision from the posterior portal arthroscope. External pressure can push the distal end of the clavicle end down into the bursa and bimanual palpation in association with manipulation of the shaver, the lateral 1 cm of the clavicle is removed. More bone is removed inferiorly and posteriorly from the clavicle, because this is -where residual impingement may occur. Great care is taken to preserve the superior capsule and superior acromioclavicular ligament, and this superior part must be done under direct vision.
Too much bone may be resected from the acromion, hence weakening the deltoid attachment. The amount of bone removed from the outer end of the clavicle may be assessed by judging against the width of the shaver; that is, if it is a 4-mm shaver, then approximately two and a half times its own width must be removed. As part of the subacromial bursa is resected medially, swelling increases rapidly once the bursa is broached. The procedure should then be completed as quickly as possible with the most minimal inflow pressure possible to reduce the amount of swelling. The swelling in itself is not a problem, because this quickly reduces postoperatively, but it can affect the mobility of the shaver through the portals if the swelling is great. The inflow pressure is kept at just above arterial pressure.
The patients are put in a sling for pain relief but told that they can do no harm by moving the arm and are encouraged to do so from as soon after operation as possible. Most patients get rid of the sling within a few days but are told they will still have discomfort in the shoulder when they are seen for review at 3 -weeks. In 3 -weeks they generally have a good range of movements at least below shoulder height and are told that it takes 3 months to get 80 percent of the improvement. The time scale to the static level is the same as that for open excision arthroplasty, but time off work is generally less.
Copeland SA: Primary osteoarthritis of the acromioclavicular joint—results of excision arthroplasty. pp. 128-30. In: the Shoulder. Professional Postgraduate Service, Tokyo, 1986 Ellman H, Gartsman GM: Arthroscopic Shoulder Surgery and Related Procedures. Lea & Febiger,
Philadelphia, 1993 Flatow EL, Cordasco FA, Bigliani LU: Arthroscopic resection of the outer end of the clavicle from a superior approach. A critical, quantitative radiographic assessment of bone removal.Arthroscopy 8:55, 1992
Gartsman M, Coombs AH, Davis PF, Tullos HS: Arthroscopic acromioclavicular joint resection. Ananatomic study. Am J Sports Med 19:2, 1991