Factors associated with functional improvement after posteriorly augmented total shoulder arthroplasty

Posteriorly augmented glenoid components in anatomic total shoulder arthroplasty (TSA) address posterior glenoid bone loss with inconsistent results. The purpose of this study is to identify pre- and postoperative factors that impact range of motion and function after augmented TSA in patients with B2 or B3 glenoid morphology.A retrospective review was performed of all patients who underwent TSA with a step type augment by a single surgeon between 2009 and 2018. Patients with a Walch type B2 or B3 glenoid were included. Outcomes included forward elevation (FE), external rotation (ER), internal rotation (IR), Single Assessment Numeric Evaluation (SANE), and Visual Analog Scale for pain (VAS). Preoperative imaging was reviewed to assess glenoid retroversion and posterior humeral head subluxation relative to the scapular body and mid-glenoid 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 range of motion and functional outcome scores.Fifty patients (mean age, 68.1 + 8.0) with a mean follow-up of 42.0 months (Range, 24-106 months) were included. Glenoid morphology included 41 B2 and 9 B3 glenoids. One patient had center-peg osteolysis and one patient had glenoid component loosening. The average preoperative FE, ER, and IR was 110°, 21°, and S1, respectively. The average postoperative FE, ER, and IR was 155°, 42°, and L1, respectively. The mean postoperative VAS score was 0.5 + 0.8 and mean SANE score was 94.5 + 5.6. Patients with B3 glenoids were associated with better postoperative internal rotation compared to B2 glenoids (T10 vs L1, p=0.024), with no other differences in range of motion between the glenoid types. Preoperative glenoid retroversion did not significantly impact postoperative range of motion. Postoperative glenoid component retroversion and residual posterior subluxation relative to the scapular body or glenoid face did not correlate with range of motion in any plane. However, posterior subluxation relative to the glenoid face was moderately associated with lower SANE scores (r= -0.448, p=0.006).Patients achieved excellent functional outcomes and pain improvement after TSA with an augmented glenoid component. Postoperative range of motion and function had no clinically important associations with pre- or postoperative glenoid retroversion or humeral head subluxation in our cohort of posteriorly augmented total shoulder arthroplasties except for worse functional scores with increased humeral head subluxation in relation to the glenoid surface.