Changes of Muscle Atrophy According to the Immediate Postoperative Time Point in Magnetic Resonance Imaging After Arthroscopic Rotator Cuff Repair

The purpose of this study was to investigate changes of rotator cuff muscles after arthroscopic rotator cuff repair by measuring the muscle atrophy (MA) of rotator cuff muscles at the preoperative, immediate postoperative, and 1-year postoperative time points.Inclusion criteria were (1) arthroscopic rotator cuff repair of a full-thickness rotator cuff tear and (2) the presence of the preoperative (approximately 1 month before surgery), immediate postoperative (approximately 3 days after surgery), and 1-year postoperative magnetic resonance imaging (MRI) undertaken at our institution. Exclusion criteria were (1) the absence of any of the 3 MRIs, (2) isolated subscapularis repair, and (3) rotator cuff repair with margin convergence only. The MA was assessed with the modified tangent sign (TS), the occupation ratio (OR), and the cross-sectional areas (CSAs) of the supraspinatus and infraspinatus. Structural integrity was evaluated using Sugaya's classification. Measurements 1 year after surgery were compared with those of the preoperative and the immediate postoperative time points according to the integrity.Seventy-seven patients were included in the study. The TS improved in 23.4% of patients and worsened in 6.5% with the preoperative baseline, while it improved in 5.2% of patients and worsened in 23.4% (P.001). The OR improved in 24.5% of patients but worsened in 3.9% with the preoperative baseline, while it improved in 13.0% and worsened in 11.7% patients (P.001). The CSAs of the supraspinatus and infraspinatus changed by 8.7% ± 24.5% and -0.3% ± 16.1% with the preoperative baseline and by -12.8% ± 20.3% and -10.5% ± 14.9% with the immediate postoperative baseline (all P.001).The results of the study showed that changes of the MA after arthroscopic rotator cuff repair were different with respect to the baselines and the integrity. Generally, the MA measured with the immediate postoperative baseline worsened, whereas that measured with the preoperative baseline improved.Level III, retrospective comparative study.