The effects of arthroscopic acromioplasty on the acromioclavicular joint.

Thirty patients with 31 shoulders underwent clinical and radiologic evaluation 5 to 6 years after arthroscopic acromioplasty. The mean age was 51 years. The acromioclavicular (AC) joint was assessed for tenderness on palpation and pain on horizontal adduction of the shoulder. All patients underwent a radiologic examination consisting of an anteroposterior view of the AC joint and bilateral stress views. No patient had superior translation or widening of more than 1 mm of the AC joint on stress views on the unoperated side. On the operated side 12 (38%) shoulders showed signs of instability consisting of a superior translation of the clavicle of 2 to 3 mm, distraction on weight bearing view, or both. No severely osteoarthritic AC joint (grade 3 or 4) was unstable. The degree of osteoarthritis did not differ for both shoulders, suggesting that arthroscopic acromioplasty does not accelerate osteoarthritic change in the AC joint but can induce instability. Nine patients had tenderness over the AC joint and instability on stress views. They had a significantly reduced University of California Los Angeles score of 25 +/- 5 compared with the other patients (29.5 +/- 7). We conclude that preservation of the inferior capsule during arthroscopic acromioplasty is important for the integrity of the AC joint in patients without severe osteoarthritic changes.