Clinical and Radiologic Outcomes of Small Glenoid Baseplate in Reverse Total Shoulder Arthroplasty: A Prospective Multicenter Study

BACKGROUND: The purpose of this study was to evaluate the clinical and radiologic outcomes of reverse total shoulder arthroplasty (RTSA) using a small glenoid baseplate in patients with a small glenoid and to analyze the contributing factors to scapular notching. METHODS: A total of 71 RTSAs performed using a 25-mm baseplate were evaluated at a mean of 37.0 ± 3.3 months. Shoulder function was evaluated using American Shoulder and Elbow Surgeons (ASES) score, visual analog scale (VAS) for pain, Single Assessment Numeric Evaluation (SANE) for satisfaction, and active range of motion. Scapular neck angle (SNA), prosthesis-scapular neck angle (PSNA), peg glenoid rim distance (PGRD), and sphere bone overhang distance (SBOD) were measured to assess the effects on scapular notching. RESULTS: Shoulder function (ASES: 39.4 ± 13.8 preoperative vs. 76.2 ± 9.5 at last follow-up, p < 0.001), VAS for pain (6.1 ± 1.8 vs. 1.7 ± 1.4, p < 0.001), SANE for satisfaction (7.0 ± 11.8 vs. 83.4 ± 15.3, p < 0.001), and active forward flexion (115.6° ± 40.1° vs. 141.6° ± 17.2°, p < 0.001) were significantly improved. The mean diameter of the inferior glenoid circle was 26.0 ± 3.0 mm and the mean glenoid vault depth was 24.0 ± 4.5 mm. Scapular notching was found in 13 patients (18.3%) and acromial fracture in 2 patients (2.8%). There were no significant differences in preoperative SNA and PSNA at postoperative 3 years between patients with and without scapular notching (101.6° ± 10.5° and 110.8° ± 14.9° vs. 97.3° ± 13.3° and 104.9° ± 12.4°; p = 0.274 and p = 0.142, respectively). PGRD and SBOD were significantly different between patients with scapular notching and without scapular notching (24.8 ± 1.6 mm and 2.6 ± 0.5 mm vs. 21.9 ± 1.9 mm and 5.8 ± 1.9 mm; p < 0.001 and p < 0.001, respectively). CONCLUSIONS: RTSA using a 25-mm baseplate in a Korean population who had relatively small glenoids demonstrated low complication rates and significantly improved clinical outcomes. Scapular notching can be prevented by proper positioning of the baseplate and glenosphere overhang using size-matched glenoid baseplates.