Factors associated with functional improvement after posteriorly augmented total shoulder arthroplasty.

Abstract

Posteriorly augmented glenoid components in anatomic total shoulder arthroplasty (TSA) address posterior glenoid bone loss with inconsistent results. The purpose of this study was to identify preoperative and postoperative factors that impact range of motion (ROM) and function after augmented TSA in patients with type B2 or B3 glenoid morphology. This was a retrospective review of all patients who underwent TSA with a step-type augmentation performed by a single surgeon between 2009 and 2018. Patients with Walch type B2 or B3 glenoids were included. Outcomes included forward elevation (FE), external rotation (ER), internal rotation (IR), Single Assessment Numeric Evaluation (SANE) score, and visual analog scale pain score. Preoperative imaging was reviewed to assess glenoid retroversion and posterior humeral head subluxation relative to the scapular body and midglenoid face. Postoperative measurements included glenoid retroversion, subluxation relative to the scapular body, subluxation relative to the central glenoid peg, and center-peg osteolysis. Measurements were performed by investigators blinded to ROM and functional outcome scores. Fifty patients (mean age, 68.1±8.0 years) with a mean follow-up period of 42.0 months (range, 24-106 months) were included. Glenoid morphology included type B2 glenoids in 41 patients and type B3 glenoids in 9. One patient had center-peg osteolysis, and 1 patient had glenoid component loosening. Average preoperative FE, ER, and IR were 110°, 21°, and S1, respectively. Average postoperative FE, ER, and IR were 155°, 42°, and L1, respectively. The mean postoperative visual analog scale score was 0.5±0.8, and the mean SANE score was 94.5±5.6. Type B3 glenoids were associated with better postoperative IR compared with type B2 glenoids (T10 vs. L1, P=.024), with no other differences in ROM between the glenoid types. Preoperative glenoid retroversion did not significantly impact postoperative ROM. Postoperative glenoid component retroversion and residual posterior subluxation relative to the scapular body or glenoid face did not correlate with ROM in any plane. However, posterior subluxation relative to the glenoid face was moderately associated with lower SANE scores (r=-0.448, P=.006). Patients achieved excellent functional outcomes and pain improvement after TSA with an augmented glenoid component. Postoperative ROM and function showed no clinically important associations with preoperative or postoperative glenoid retroversion or humeral head subluxation in our cohort of posteriorly augmented TSAs, except for worse functional scores with increased humeral head subluxation in relation to the glenoid surface.