Significance of the acromiohumeral distance on stress radiography for predicting healing and function after arthroscopic repair of massive rotator cuff tears

Background: A decreased acromiohumeral distance (AHD) is commonly detected in patients with massive rotator cuff tears (mRCTs). Most studies evaluating fixed humeral elevation have used preoperative or postoperative standardized radiography and not stress radiography. This study aimed to evaluate the predictive role of the preoperative AHD measured using stress radiography (AHD_stress) in rotator cuff healing and function after arthroscopic repair of mRCTs. Methods: The data of 113 patients who underwent arthroscopic repair of mRCTs 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 months (range, 24-92 months) postoperatively. Forty-seven patients showed healing failure. Propensity score matching (1-1) was performed between the healed group and healing failure group. Thirty-eight patients in each group were matched in the final analysis. The 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. The AHD difference (AHD_diff) was defined as the difference between the AHD and AHD_stress values. Receiver operating characteristic curve analysis was performed to determine cutoff values for significant variables. Results: No difference in the mean preoperative AHD was found between the healed group (7.5 +/- 2.0 mm) and healing failure group (6.9 +/- 2.2 mm, P = .234). The AHD_diff value was significantly higher in the healed group (4.4 +/- 2.1 mm) than in the healing failure group (3.0 +/- 2.0 mm, P = .002; cutoff, 3.2 mm). Patients with an AHD_diff value >= 3.2 mm showed a lower healing failure rate (28.9% vs. 71.1%, P < .001) and higher functional scores than patients with an AHD_diff value < 3.2 mm. The AHD_diff value 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 = .024). Among patients with healing failure, only the postoperative AHD showed a significant difference between those with an ASES score >= 80 (7.0 +/- 2.5 mm) and those with an ASES score < 80 (4.8 +/- 2.1 mm, P = .009; cutoff, 4.8 mm). Conclusion: A reducible AHD, which increased by >= 3.2 mm under stress radiography, can be a favorable predictor of rotator cuff healing and function after arthroscopic repair of mRCTs. Our findings suggest that this new and simple radiologic parameter should be considered preoperatively and would be helpful to determine appropriate treatment strategies. (C) 2020 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.