The rate and predictors of healing of repaired lesser tuberosity osteotomy in reverse total shoulder arthroplasty.

Abstract

Evidence is building that a functional subscapularis improves function-specifically internal rotation tasks-following reverse total shoulder arthroplasty (rTSA). However, the optimal method for subscapularis repair during rTSA remains unknown with variable healing rates reported. This study aims to investigate the rate of and predictors for healing a lesser tuberosity osteotomy (LTO) following rTSA. Following local institutional review board approval, patients with at least one-year follow-up for rTSA managed with an LTO and subsequent repair between March, 2017 and March, 2020 were retrospectively identified. Shoulders were selected for LTO repair based upon preoperative imaging and intraoperative assessment of subscapularis quality. All patients were implanted with a system consisting of a 150° or 155° (constrained) humeral neck-shaft angle and 2.5 to 4.5 millimeters (mm) of glenoid lateralization (Trabecular Metal Reverse Shoulder System; Zimmer Biomet, Warsaw, IN, USA). At a minimum of six months, radiographs were reviewed for an assessment of LTO healing by three independent reviewers. Healing was classified as displaced, fibrous union, or ossified union. For assessing predictors, the repair was considered intact if the LTO fragment was not displaced (fibrous union or ossified union). Sixty-five rTSA with LTO repair were performed in 64 patients. These patients had an average age of 67.2 years (range, 31-81) and 36 (55.4%; 36/65) were female. At an average follow-up of 15.2 months (range, 8-38), 50 cases (76.9%; 50/65) were classified as having an ossified union. The radiographic healing could not be assessed in a single case. Of the 14 cases without ossific union, 8 (12.3%; 8/65) were displaced and 6 (9.2%; 6/65) were classified as a fibrous union. In logistic regression, only combined humeral liner height predicted LTO displacement (odds ratio=1.4 [95% confidence interval=1.1-1.8]; P=.01). Humeral loosening was not found in any cases following LTO. This analysis demonstrates that radiographic healing of LTO repair is more favorable than published rates of healing after subscapularis tenotomy or peel in the setting of rTSA. Subscapularis management with LTO provides the ability to monitor repair integrity with plain radiographs and a predictable radiographic healing rate. The integrity of subscapularis repair may be influenced by the use of thicker humeral liners. Further investigation is needed to determine the functional impact of a healed subscapularis following rTSA.