Increased latissimus dorsi and teres major muscle volume after anterior transfer for irreparable anterior superior rotator cuff tear: correlation with improved internal rotation strength

Introduction While the well-established correlation between increased muscle volume and enhanced muscle strength is widely recognized, there have been no studies assessing volumetric muscle changes in transfer surgery in the shoulder. This study aimed to evaluate changes in transferred muscle volume and their clinical implications in anterior latissimus dorsi and teres major (aLDTM) tendon transfer in patients with anterior superior irreparable rotator cuff tears (ASIRCTs). Materials and methods The study retrospectively examined 40 patients who underwent aLDTM tendon transfers for ASIRCTs between August 2018 and January 2022. Using ImageJ software, the LDTM muscle was segmented in T2-weighted oblique axial images, and total muscle volume (tLDTMV) of both immediate and postoperative 1-year were calculated. Pearson correlation analysis was used to determine the correlation between ΔtLDTMV and ΔASES scores, Δactive-ROM, and Δstrength. Results The current study revealed an 11.4% increase in tLDTMV at 1-year postoperative. Patients were grouped based on postoperative ASES score: Group 1 (Optimal, n = 17) and Group 2 (Suboptimal, n = 23). Although tLDTMV immediate postoperative values were similar between groups ( P = 0.954), tLDTMV 1-year postoperative value was significantly higher in Group 1 compared to Group 2 ( P = 0.021). In correlation analysis, ΔtLDTMV showed significant correlations with ΔASES score ( r = 0.525, P < 0.001), ΔaROM of forward elevation (FE) ( r = 0.476, P = 0.002), ΔaROM of internal rotation (IR) at back ( r = 0.398, P = 0.011), Δstrength of FE ( r = 0.328, P = 0.039), Δ strength of IR at 90° abduction ( r = 0.331, P = 0.037), and IR at side ( r = 0.346, P = 0.029). Conclusions Significant increase in tLDTMV was observed at 1-year postoperative for ASIRCT patients. Notably, greater ΔtLDTMV exhibited a correlation with better ASES scores, increased aROM and strength in both FE and IR. Nevertheless, further research is required by employing more robust standardized measurement tools and a larger sample size.