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Background: Acromioclavicular (AC) horizontal instability is a problem affecting not only young athletic patients after a trauma to the AC joint but also older patients who have undergone distal clavicle resection. It may cause pain and poor functional outcomes unless the reconstruction technique specifically addresses the horizontal instability of the clavicle, in addition to the well-known superior instability. Methods: Three cadaveric specimens underwent dissection of the AC joint capsule to determine the superior attachments of the AC joint capsule. These shoulders subsequently underwent distal clavicle resection and were loaded to a 7-kg weight in the horizontal plane. The horizontal displacement of the clavicle was measured and resection continued to the point of horizontal instability of the clavicle. Thereafter, the reverse coracoacromial ligament reconstruction technique was performed and recreation of horizontal stability assessed. Utilization of the reverse coracoacromial ligament transfer in two clinical cases will also be presented. Results: The AC joint capsule is continuous with trapezius and deltoid insertions. The average distance between the articular surface and insertion of the capsule on the clavicle is 10 mm and on the acromion is 14.8 mm. Horizontal clavicular translation increased from 2.3 mm when intact to 3.3 mm with capsular transection, 8.7 mm with 5 mm clavicle resection, and finally 15 mm with a 10-mm clavicle resection. Horizontal instability of the clavicle was demonstrated with a 10-mm clavicle resection. Conclusion: Horizontal instability of the clavicle is evident with distal clavicle resection of greater than 10 mm. A reverse coracoacromial ligament transfer may be a reasonable technique to address horizontal stability of the clavicle during AC joint reconstruction in the context of painful instability.

Background: Reverse shoulder arthroplasty is gaining popularity owing to its proven longevity and good outcome scores. Scapular notching remains a concern. This study aimed to assess the safety of larger polyethylene glenospheres with increased eccentricity in comparison with the more conventional metal bearings. The secondary effects on scapular notching, clinical outcomes, range of movement, and complications were also analyzed. Methods: We conducted a 10-year retrospective review of 145 SMR reverse shoulder arthroplasties (LimaCorporate, Udine, Italy) in 132 patients with radiographs at a minimum of 2 years postoperatively. The primary outcome measure was the survivorship of the larger polyethylene glenospheres. Secondary outcomes were the presence and size of notching, subjective satisfaction score, American Shoulder and Elbow Surgeons score, Oxford Shoulder Score, range of motion, and shoulder-related complications. Results: No failures of the polyethylene glenospheres were noted in the 10-year period. At a minimum of 2 years’ follow-up, notching was noted in 16 (25%) of the metal glenospheres vs. 9 (11.1%) of the polyethylene glenospheres (P = .028). The mean Oxford Shoulder Score was lower for the metal glenospheres (P = .005). Range of motion, complications, and overall satisfaction were similar in both groups. Conclusion: The inverted bearing configuration demonstrated no failures at a minimum of 2 years’ follow-up. A larger study is required to determine whether the decreased incidence and size of early notching are related to the bearing size or material.