Pre-operative factors influence the recovery of range of motion following reverse shoulder arthroplasty

Introduction Recently the use of reverse shoulder arthroplasty (RSA) has increased because of a clinical perception of durable functional outcome. However, some patients unexpectedly have a poor recovery of range of motion (ROM) after surgery. Objective factors such as initial diagnosis, pre- and intra-operative ROM, deltoid impairment or arm lengthening have previously been associated with anterior forward flexion (AFF). This study sought to determine if subjective pre-operative factors influence the rate and timing of ROM recovery after RSA. Methods Between January 2011 to January 2012, all RSAs performed by a single surgeon were prospectively enrolled in this study. The cohort was divided into two groups based on AFF <90 or >= 90 after surgery. A multivariate analysis was performed to define independent predictive factors of post-operative ROM. Factors assessed included: age, sex, dominant arm, patient activity, body mass index (BMI), pre-operative diagnosis, deltoid status, pain and Constant scores, subjective shoulder value (SSV), simple shoulder test (SST) and radiographic findings. Patients were reviewed at six weeks, and three, six, 12 and 24 months. Results One hundred and one RSAs were available for analysis. Poor post-operative AFF at six weeks was significantly related to poor pre-operative deltoid strength. Poor post-operative AFF at one-year follow-up was related to surgery of non-dominant arm, pre-operative poor AFF, pre-operative activity, poor subjective shoulder value (SSV), and a low contralateral Constant score. AFF and Constant score improved until six months and then plateaued. In contrast, both external and internal rotation continued to improve beyond six months after surgery. Conclusions AFF and Constant scores after RSA plateau at six months after surgery whereas internal and external rotation continue to improve up to two years post operation. Several pre-operative factors including poor pre-operative AFF, surgery on the non-dominant arm, and lower SSV and Constant scores are correlated with post-operative ROM following RSA. Identification of these factors may be useful for counseling on functional expectations as well as customizing rehabilitation plans.