Lower deltoid tuberosity indices are associated with the use of a stemmed instead of a preoperatively planned stemless implant

Abstract

BackgroundAnatomic total shoulder arthroplasty (TSA) using a stemless prosthesis continues to increase in popularity as literature supporting their use grows. Intraoperative findings, however, may require switching from a planned stemless prosthesis to using a stemmed implant, yet literature attempting to understand the incidence and risk factors leading to this outcome is limited. The purpose of this study was to document the incidence of intraoperative change from a planned stemless implant to a stemmed prosthesis and to determine the correlation between the deltoid tuberosity index and this decision. MethodsAll patients scheduled to undergo TSA with a stemless humeral prosthesis between 2018 and 2023 at a single academic institution were retrospectively reviewed. Sociodemographic data, comorbidities, and preoperative deltoid tuberosity indices (DTI) were collected for review. DTI was used as an approximation for a patient’s bone mineral density. Surgeon plan for stemless TSA was verified via saved three-dimensional preoperative plans. ResultsNinety-two patients were scheduled to undergo stemless TSA, 8 (8.70%) of which received a stemmed implant based on intraoperative findings. In all cases, the operative surgeon deemed the metaphyseal bone inadequate to facilitate use of a stemless implant. DTI was significantly higher in the stemless group relative to the stemmed group (1.55 vs. 1.37, P = .0023). Discussion and ConclusionApproximately 9% of planned stemless TSA were converted to stemmed TSA due to proximal humerus bone insufficiency based on surgeon assessment at time of surgery. Diminished DTI was noted to be a risk factor. Preoperative planning may be improved by including imaging parameters to assess bone sufficiency (eg, DTI).