The effect of the subacromial balloon spacer on humeral head translation in the treatment of massive, irreparable rotator cuff tears: a biomechanical assessment

Background: The current management of massive, irreparable rotator cuff tears is challenging, and no individual surgical technique has demonstrated clinical superiority. This study evaluated the role of a subacromial balloon spacer and its ability to depress the humeral head in the setting of a massive, irreparable rotator cuff tear. Methods: Eight cadaveric shoulders were tested. The specimens were mounted onto a shoulder simulator that applied muscle loading. Five shoulder states were tested: intact; irreparable rotator cuff tear; and inflation of the subacromial balloon spacer with 10, 25, and 40 mL of saline solution on the irreparable rotator cuff tear. Humeral head migration was measured at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of shoulder abduction. Results: After creation of a massive, irreparable rotator cuff tear, in 0' of abduction, the humeral head migrated superiorly by a mean of 3.5 +/- 0.7 mm compared with the intact shoulder state (P = .002). The subacromial balloon spacer inflated to 25 mL translated the humeral head inferiorly relative to the torn state by an average of 3.2 +/- 0.6 mm (P = .001) for all abduction angles. The balloon inflated to 10 mL was ineffective at restoring humeral head position as it was still significantly superior than intact (P = .017). The balloon inflated to 40 mL was successful in depressing the humeral head; however, it overtranslated the humeral head anteroinferiorly, such that it was significantly different from the intact condition (P < .001). Overall, the 25-mL balloon best restored the humeral head position. Conclusion: The results of this study demonstrate that the subacromial balloon spacer is most effective in depressing the humeral head and restoring the glenohumeral joint position when inflated to 25 mL. (C) 2019 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.