Reversibility of Supraspinatus Muscle Atrophy in Tendon-Bone Healing after Arthroscopic Rotator Cuff Repair

Background: To date, there are few reports of the definite reversibility of rotator cuff muscle atrophy after repair. Purpose: To evaluate the reversibility of rotator cuff muscle atrophy after successful arthroscopic repair. Study Design: Case series; Level of evidence, 4. Methods: Included in this study were 47 patients (mean age, 61.2 ± 7.3 years; range, 49-73 years) who underwent arthroscopic rotator cuff repair as well as magnetic resonance imaging (MRI) preoperatively and at 6-month and last follow-up. Patients who had confirmed rotator cuff healing (grades 1-3 according to the Sugaya classification) on both series of postoperative MRI were enrolled in the study. The mean time from the onset of symptoms to surgery was 24.7 ± 25.6 months (range, 3-120 months). The minimum follow-up was 2 years, and the mean follow-up duration was 41.8 ± 14.4 months. Serial changes in the supraspinatus muscle area on the most matching MRI scans (sagittal-oblique view) were evaluated. The area was measured by 2 independent observers. Results: Both independent observers reported no significant difference in the area of the supraspinatus muscle between the preoperative time point and 6-month follow-up (observer 1: P =.135; observer 2: P =.189). However, there was a significant difference between the 6-month and last follow-up (mean, 41.8 months; observers 1 and 2: P <.001). The serial changes in the area preoperatively and at 6-month and last follow-up were 419.41 ± 122.97 mm², 431.76 ± 104.27 mm², and 466.73 ± 121.42 mm², respectively (observer 1), and 421.01 ± 116.61 mm², 432.56 ± 100.78 mm², and 469.84 ± 113.80 mm², respectively (observer 2). The intraclass correlation coefficient between the 2 observers was 0.988. At final follow-up, the area increase on the medial and lateral aspects of the sagittal-oblique view compared with preoperatively was 13.9% (P <.001) and 11.3% (P <.001), respectively. Fatty infiltration did not change from preoperatively to 6-month follow-up (P >.999) or from 6-month to final follow-up (P =.077). Conclusion: After successful arthroscopic rotator cuff repair, there was a slight (11.3%-13.9%) increase in muscle volume from preoperatively to final follow-up, as seen on serial MRI. Fatty infiltration according to the Goutallier grade was not reversed (P =.077). Some reversibility of supraspinatus muscle atrophy may exist in tendon-bone healing after arthroscopic rotator cuff repair; further follow-up is needed to better elucidate this result.