Postoperative infraspinatus contractility is associated with acromiohumeral distance after arthroscopic rotator cuff repair.

OBJECTIVE

To investigate whether infraspinatus muscle contractility improves following arthroscopic rotator cuff repair (ARCR) and its impact on postoperative acromiohumeral distance (AHD).

METHODS

In this prospective case series, 61 shoulders with posterosuperior rotator cuff tears involving at least a full-thickness supraspinatus tear, with or without extension into the infraspinatus tendon (mean age: 66.4 ± 7.7 years; 31 men, 30 women) were followed for 1 year after ARCR. Shoulders with subscapularis tears or re-tears were excluded. Muscle contractility was measured using real-time tissue elastography (activity value = elasticity difference between rest and contraction), while AHD was assessed radiographically at 0° and 60° abduction.

RESULTS

The infraspinatus activity value increased significantly (0.52 ± 0.25 to 0.76 ± 0.28; p < 0.05) and showed positive correlations with AHD at 0° (r = 0.424, p < 0.05) and 60° abduction (r = 0.587, p < 0.05), with postoperative AHD increasing by approximately 1 mm at both angles at 1 year. Supraspinatus muscle contractility demonstrated no significant correlations. In the multivariable regression analysis, the infraspinatus activity value and its Goutallier grade were independently associated with postoperative AHD.

CONCLUSION

Improvement in infraspinatus muscle contractility was associated with postoperative AHD, suggesting a potential role of infraspinatus function in postoperative glenohumeral mechanics.