Stemless total shoulder arthroplasty with nonspherical polyethylene humeral head

The use of a nonspherical humeral head has been recently introduced in anatomic total shoulder arthroplasty (aTSA). This multicenter observational study investigated the early outcomes of a novel shoulder prosthesis with a nonspherical polyethylene humeral head in a consecutive series of patients with stemless aTSA.

From January 2022 to December 2022, 35 patients (35 shoulders) with primary glenohumeral osteoarthritis received a stemless implant with inverted bearing materials: a nonspherical polyethylene humeral head articulating with a metal glenoid. Axial plane glenoid morphology was Walch A2 in 26 patients, B2 in 7, and C in 2. At 2-year follow-up, patients were assessed through subjective satisfaction; implant awareness; active range of motion; Constant-Murley Score; American Shoulder and Elbow Surgeons; and Disabilities of the Arm, Shoulder, and Hand scores. Postoperative radiographs were assessed for radiolucent lines, component loosening, and migration. Any complications and revisions were recorded.

At 2-year follow-up, mean forward elevation increased from 91.0° (standard deviation [SD], 27.7°) to 146.0° (SD, 19.1°) (P < .001) and mean external rotation from 16.6° (SD, 11.6°) to 48.8° (SD, 18.4°) (P < .001). Disabilities of the Arm, Shoulder, and Hand, American Shoulder and Elbow Surgeons, and Constant-Murley Scores improved from 60.4, 35.7, and 37.5 to 18.9, 82.0, and 75.0, respectively (P < .001). All patients were satisfied and reported no awareness of their artificial shoulder. Radiographically, all implants appeared stable and osseointegrated. There was no implant-related revision, reoperation, or complication.

The early clinical and radiographic results of this novel implant are promising and support the concept of inverted bearing materials in stemless aTSA, demonstrating improvements that outreach the relative substantial clinical benefit for the patients.