Acromial and scapular spine fractures (ASF) are known complications following implantation of Reverse Total Shoulder Arthroplasty (RTSA). The entity of acromial stress reaction (ASR) without fracture has recently been described. The purpose of this study was to analyze the incidence, radiographic predictors, treatment options, healing rate and clinical outcome of ASF and ASR compared to a control group.
A total of 854 primary RTSAs were implanted between 2005 and 2018 in a single shoulder unit of a tertiary referral hospital and retrospectively reviewed for the incidence of ASF and ASR. ASR was defined as pain at the acromion or scapular spine after fracture exclusion on CT scans. The ASF group was matched to a control group. Preoperative and postoperative radiographs were analyzed for radiographic predictors of ASF or ASR. The impact of ASF and ASR, operative versus non-operative treatment and fracture union on clinical outcome (Constant-Murley Score, Subjective Shoulder Value and range of motion) with minimum follow-up of 2 years was analyzed.
A total of 46 ASF (5.4 %) in 44 patients and 44 ASR (5.2%) in 43 patients were detected at a mean of 16 ± 24 months and 20±23 months postoperative, respectively. Predictive radiographic factors were an increased critical shoulder angle (CSA) and lateralization shoulder angle (LSA). The overall union rate was 55% (22/40) but significantly higher following operative treatment (9/11, 82%) compared to non-operative treatment (13/29, 45%). Patients with ASF/ASR demonstrated inferior clinical outcome (CS 44 ± 21 and 48 ± 18; SSV 52 ± 25 and 57 ± 27) compared to the control group (CS 66 ± 14; SSV: 82 ± 22) independent of bony union or treatment at mean of 59 ± 33 months (ASF) and 61 ± 38 months (ASR).
ASF and ASR are frequent complications following RTSA implantation with similar poor clinical outcome measures. The healing rate was shown to be much higher with a surgical approach. Nevertheless, fracture consolidation does not result in better clinical outcomes compared with nonunion.