Increased scapular spine fractures after reverse shoulder arthroplasty with a humeral onlay short stem: an analysis of 485 consecutive cases

Abstract

Background: Scapular stress fractures after reverse shoulder arthroplasty (RSA) are a potentially serious complication with modern lateralized and onlay implants. The aim of this study was to report the scapular spine stress fracture rate after RSA with an onlay, 145° humeral stem, analyzing potential fracture risk factors and clinical outcomes in a large cohort of patients.

Methods: A consecutive series of 485 RSAs were implanted with the Aequalis Ascend Flex stem. Data collection included preoperative and postoperative clinical and radiographic assessment findings (rotator cuff Goutallier grade; Hamada, Walch, and Favard classifications; range of motion; Constant score) and perioperative data. Patients with a scapular spine fracture following RSA were matched with nonfracture control patients, and preoperative variables were tested to determine whether they were predictive of a scapular spine fracture.

Results: A scapular spine fracture following RSA occurred in 21 patients (4.3%), with a mean time to diagnosis of 8.6 months (range, 1-34 months). No preoperative factor was found to be a significant predictor of scapular spine fracture. Both groups showed significant improvements in active mobility measurements and Constant scores from preoperatively to final follow-up (P < .001). The control group scored significantly better than the scapular spine fracture group regarding the Constant score and forward flexion.

Conclusion: Scapular spine fractures have shown an increased prevalence after onlay-design RSA. This series was not able to link any clear risk factors. Functional results are limited, regardless of the fracture management.

Keywords: Scapular fracture; acromion; lateralized stem; onlay design; outcomes; postoperative complication; reverse shoulder arthroplasty; spine.