Abstract
BACKGROUND: The purpose of this study was to compare the restoration of humeral head anatomy, as well as 2-year radiographic and functional outcomes of anatomic total shoulder arthroplasty (aTSA) using a convertible metaphyseal-based short inlay humeral stem and a stemless humeral component. METHODS: All patients between May 2021 and May 2022 that underwent aTSA using a convertible metaphyseal-based short inlay humeral stem by a single surgeon were included and compared to a cohort of patients that underwent stemless aTSA by the same surgeon between February 2019 and October 2020. An intramedullary cutting guide, a large lesser tuberosity osteotomy (LTO) repaired with cerclage wires, and preoperative 3-dimensional planning were utilized in all cases. The restoration of humeral head anatomy was assessed on an AP radiograph of the proximal humerus 2 weeks postoperatively. Functional outcome scores, range of motion, and LTO healing were collected 2-years postoperatively. Calcar stress shielding was assessed on 2-year postoperative radiographs using the Levy classification. RESULTS: Overall, there were 26 patients (81.3% follow-up) in the stem group and 43 patients (84.3% follow-up) in the stemless group with 2-year follow-up data. All patients (32 stem/51 stemless) were included in the radiographic analysis assessing humeral head restoration. There were no differences in the humeral head height change (P = .733), percent of patients with <5 mm of humeral head height change (P = .52), percent of patients with an acceptable neck shaft angle (>130°) (P = 1), and mean shift in center of rotation (P = .546) between patients that underwent stemmed and stemless aTSA. There were no differences in American Shoulder and Elbow Surgeons scores (stem 93.8 ± 9.1; stemless 92.4 ± 10.8; P = .566), visual analog scale pain scores (stem 0.4 ± 1.1; stemless 0.4 ± 0.9; P = .941), or LTO bony union (stem 88.5%; stemless 92.6%; P = .083) between groups 2 years postoperatively. The stem group was found to have greater forward flexion at 2 years (P = .017), but similar external rotation at the side (P = .445) and internal rotation (P = .268). There were no differences in the degree of stress shielding between groups (P = .185). CONCLUSIONS: Anatomic shoulder arthroplasty with a convertible metaphyseal-based short inlay humeral stem demonstrates excellent patient-reported functional and radiographic outcomes 2 years postoperatively. No differences in restoration of humeral head anatomy, degree of stress shielding, patient-reported functional outcomes, and osteotomy healing rates were identified between patients undergoing metaphyseal short-stemmed and stemless aTSA.