Short and midterm results of reverse shoulder arthroplasty according to the preoperative etiology.

BACKGROUND: Reverse shoulder arthroplasty (RSA) has shown promising results for cuff tear arthropathy but the indication has been extended to fracture sequelae and revision shoulder arthroplasty with different preconditions. Further, the clinical relevance of inferior scapular notching for different etiologies is uncertain. Our hypothesis was that preoperative etiology as well as the occurrence of scapular notching would significantly influence the clinical outcome.
METHODS: We reviewed 76 reverse shoulder arthroplasties for cuff tear arthropathy (45 patients), fracture sequelae (10 patients) and revision arthroplasty (21 patients) retrospectively. The follow-up consisted of 71 patients and the mean follow-up period was 23 months (±14 months). All patients were evaluated postoperatively using the Constant score adjusted for age and gender and the simple shoulder test. A radiological investigation was performed preoperatively and at the time of the final follow-up including the evaluation of scapular notching according to Sirveaux. For further evaluation of scapular notching, patients were separated into three groups according to the inferior glenosphere overlap: negative or no inferior overlap -6-0 mm), mild overlap (1-4 mm) and pronounced overlap (5-9 mm).
RESULTS: After a mean follow-up of 23 months the average age- and gender-adjusted Constant score (CS) was 77.8 % (±26 %). According to the etiology, patients with cuff tear arthropathy (CTA) showed a higher CS of 83 % compared with patients with fracture sequelae (CS 73 %) and compared with patients who had undergone RSA as a revision for failed shoulder arthroplasty (CS 69 %). The difference was significant comparing the cuff tear arthropathy patients with the revision surgery patients (p = 0.035). Within the group of fracture sequelae, patients with type three sequelae according to the Boileau classification (surgical neck nonunion) had a significantly worse outcome compared with the type four fracture sequelae patients (severe tuberosity dislocation) (CS 57 vs. 87 %, p = 0.01). The overall complication rate was 27 % with 8 % infections and 9 % dislocations. Revision surgery was necessary in 11.5 % with removal or replacement of the implants in 8 %. Inferior scapular notching was detected in 43 % of the patients. These patients had an inferior CS (70 ± 18 %) compared with patients without scapular notching (84 ± 25 %, p = 0.015). The incidence of scapular notching was significantly reduced with an increasing inferior overlap of the glenosphere.
CONCLUSIONS: In conclusion, we found the preoperative etiology to influence the clinical results after RSA with superior results given for cuff tear arthropathy and inferior results for revision arthroplasty and fracture sequelae type three. Further, we found a correlation between scapular notching and the clinical outcome. The inferior scapular notching was significantly reduced by an increased inferior glenosphere overlap. LEVEL OF EVIDENCE: Level IV, case series, treatment study.