Proximal humeral bone resorption (PHBR) after reverse total shoulder arthroplasty (RTSA) is not fully understood, partly because prior two-dimensional (2D) radiographic studies may under-/overestimate three-dimensional (3D) bone loss. We aimed to quantify 1-year postoperative bone loss using volumetric 3D computed tomography (CT) and identify associated risk factors. We performed a retrospective cohort study of 63 shoulders that received primary RTSA for cuff tear arthropathy (CTA) between April 2019 and April 2023. Mimics 26.0 software (Materialise, Leuven, Belgium) and 3-Matic 18.0 software (Materialise, Leuven, Belgium) were used to segment four proximal-humeral regions and the humeral shaft using 3D reconstruction and segmentation. Bone formation and resorption were volumetrically estimated. Paired t-tests were used to compare preoperative and 1-year postoperative bone volumes, and univariable and multivariable linear regression analyses were performed to identify factors associated with PHBR. Bone resorption was detected in all four proximal‑humeral regions and the shaft, with the greatest loss at the greater tuberosity region (mean ± SD, 1,468.9 ± 1,161.1 mm3) and the least at the teres minor region (423.9 ± 540.2 mm3). Shoulders reconstructed with onlay-cup implants demonstrated significantly more proximal bone loss than inlay-cup implants (P .05). 3D CT volumetric analysis demonstrated substantial proximal humeral bone loss within the first postoperative year after RTSA, most pronounced at the greater tuberosity. An onlay-cup design, higher canal filling ratio, smaller NSA, and female sex were associated with greater regional bone resorption, whereas stem length and surface‑coating type were not associated. Retrospective comparative study, LEVEL III.
Koo et al. (Fri,) studied this question.