Significance of the Acromiohumeral Distance on Stress Radiography for Predicting Healing and Function after Arthroscopic Repair of Massive Rotator Cuff Tears.

BACKGROUND Decreased acromiohumeral distance (AHD) is commonly detected in patients with massive rotator cuff tears (mRCT). Most studies evaluating fixed humeral elevation have used pre- or postoperative standardized radiography and not stress radiography. This study aimed to evaluate the predictive role of preoperative AHD measured using stress radiography on rotator cuff healing and function after arthroscopic repair of mRCT. METHODS Data of 113 patients who underwent arthroscopic repair of mRCT were analyzed. Postoperative cuff integrity was evaluated using magnetic resonance imaging at 1 year and shoulder function was evaluated at a mean of 34.9 ± 17.8 (range, 24-92) months postoperatively. Forty-seven patients showed healing failure. Propensity score matching (1-to-1) was performed between the healed and healing failure groups. Thirty-eight patients in each group were matched in the final analysis. AHD and AHD_stress were defined as the shortest distances from the inferior acromion to the superior humerus on standard anteroposterior radiography and stress radiography (5.4 kg weight applied inferiorly in a neutral position), respectively. AHD difference (AHD_diff) was defined as the difference between AHD on standard anteroposterior radiography and AHD_stress on stress radiography. Receiver operating characteristic curve analysis was performed to determine cutoff values for significant variables. RESULTS There was no difference in the mean preoperative AHD between the healed (7.5 ± 2.0) and healing failure groups (6.9 ± 2.2, p = 0.234). AHD_diff was significantly higher in the healed (4.4 ± 2.1 mm) than in the healing failure group (3.0 ± 2.0 mm, p = 0.002: cutoff, 3.2 mm). Patients with an AHD_diff ≥ 3.2 mm showed lower healing failure (28.9% vs. 71.1%, p < 0.001) and higher functional scores than those with AHD_diff < 3.2 mm. AHD_diff was higher in patients with an American Shoulder and Elbow Surgeons (ASES) score ≥ 80 (4.9 ± 1.9 mm) than in those with an ASES score < 80 (3.1 ± 2.1 mm, p = 0.024). Among patients with healing failure, only postoperative AHD showed a significant difference between ASES ≥ 80 and ASES < 80 (7.0 ± 2.5 mm vs. 4.8 ± 2.1 mm, respectively, cutoff, 4.8 mm, p = 0.009). CONCLUSION Reducible AHD, which increased by more than 3.2 mm under stress radiography, can be a favorable predictor of rotator cuff healing and function after arthroscopic repair of mRCT. These findings suggest that this new and simple radiologic parameter should be considered preoperatively and would be helpful to determine appropriate treatment strategies.