Non-spherical head designs in total shoulder arthroplasty: A systematic review of clinical and biomechanical data.

Abstract

Biomechanical studies have shown that non-spherical (NS) humeral head designs in total shoulder arthroplasty (TSA) may provide superior restoration of native anatomy, improved mechanics, and enhanced stability when compared with spherical heads. This systematic review critically evaluates the literature on NS designs in anatomic TSA. Following the PRISMA guidelines, PubMed, Cochrane, and Google Scholar (pages 1-20) were searched from inception till November 2025. Extracted data included biomechanical data such as glenohumeral kinematics, range of motion (ROM), anatomic replication, contact mechanics, and coverage, and clinical data such as radiographic outcomes, ROM, patient-reported outcome measures (PROMs), and implant-related complications. Twelve biomechanical and nine clinical studies comprising a total of 647 patients were included. Most of the biomechanical data were contradictory with some studies reporting no differences in the assessed outcomes between the designs, while most reported it to be better in NS head designs. Coverage was uniformly reported to be better with NS head designs. As for clinical data, radiographic outcomes, ROM, and PROMs all improved post-operatively with one study reporting better ROM in patients with NS TSA compared to the standard TSA. Biomechanical and clinical data report similar and sometimes improved outcomes in using non-spherical head designs for TSA. III.