BACKGROUND: Although os acromiale is often noted on preoperative imaging in patients undergoing reverse total shoulder arthroplasty (rTSA), its clinical significance is ill-defined. The purpose of this study was to compare the clinical outcomes in shoulders with an os acromiale undergoing rTSA with a matched control group.
METHODS: We conducted a retrospective review of a prospectively collected shoulder arthroplasty database for patients who underwent primary rTSA with a minimum 2-year clinical follow-up. Preoperative imaging studies taken within 6 months of surgery were assessed for an os acromiale. Sixty-four shoulders with os acromiale were identified and were matched in a ratio of 1:5 to a control group (n = 320) based on age (within 3 years), sex (exact), preoperative diagnosis, preoperative forward elevation (within 5°) and American Shoulder and Elbow Surgeons score (within five points). Clinical outcome scores, shoulder strength, and active range of motion assessed preoperatively and at latest follow-up as well as the incidence of complications were compared between cohorts. Outcomes of meso- and meta-acromion were grouped and compared with preacromion shoulders.
RESULTS: The incidence of os acromiale was 9.7% (64/663) in our institution. Of these, 55% (n = 34) were preacromion, 38% (n = 24) were mesoacromion, and 8% (n = 5) were meta-acromion. No statistically significant differences were found in any outcome score, shoulder strength, or range of motion measures between shoulders with os acromiale and matched controls. Similar proportions of each cohort achieved a clinically significant benefit (minimal clinically important difference/substantial clinical benefit) for the Shoulder Pain and Disability Index, Simple Shoulder Test, American Shoulder and Elbow Surgeons score, constant score, abduction, forward flexion, external rotation, and internal rotation. Shoulders with os acromiale had a similar overall complication rate compared with matched controls (14% vs. 12%; P = 0.658). No statistical difference in outcomes were observed between the pre- and meso-/meta-acromion shoulders.
CONCLUSIONS: Patients with os acromiale undergoing rTSA have similar postoperative functional outcomes and pain relief compared with matched controls.
LEVEL OF EVIDENCE: Ⅲ, Retrospective Matched Cohort Study.
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