Functional outcomes and complications of classic grammont-style reverse shoulder arthroplasty in patients with os acromiale: a retrospective case-control study.

Purpose: To determine the functional impact and complications associated with os acromiale after the implantation of a reverse total shoulder arthroplasty (RTSA) with medialization of the centre of rotation.

Methods: A retrospective case-control study with cross-sectional evaluation was conducted. Between 2004 and 2021, patients who underwent RTSA for cuff arthropathy, GH osteoarthritis or massive irreparable rotator cuff tears with os acromiale (OA) and more thantwo years of follow-up, were identified. A control cohort (2:1) without acromial compromise (NOOA) was also identified. Functional (Constant, ASES, Quick-DASH, VAS, ROM) and radiological assessment (os acromiale type, acromiohumeral distance, acromion tilt) were performed.

Results: RTSA was implanted in 432 cases during the study period, 221 with rotator cuff arthropathy, irreparable tears, or osteoarthritis, of these, 12 had an os acromiale (OA) (5.4%) and were compared to 24 patients without os acromiale (NOOA). Epidemiologic data OA/NOOA were: female 10/20, mean follow-up 47.2 ± 25/56.1 ± 30 months, mean age 73.5 ± 4.7/75.4 ± 4.1 years. Regarding the difference in preoperative and final follow-up functional outcomes (OA/NOOA): Constant 20.2/30.9 (p =.012), ASES 28/54 (p =.017), Quick-DASH - 19.6/-27.2 (p =.220), VAS - 5/-7 (p =.007), difference in pre-surgery/last follow-up ROM: elevation 50º/60º (p =.138), abduction 60º/60º (p =.775). The os acromiale group presented two prosthetic dislocations (16.7%).

Conclusion: Patients with os acromiale improve their preoperative condition after RTSA implantation; however, although there are no differences in joint balance, this improvement is significantly lower in the Constant and ASES scores, primarily due to a decrease in strength and pain relief experienced by patients with os acromiale.