DOES ROTATOR CUFF REPAIR AUGMENTATION WITH A SUBACROMIAL BALLOON INCREASE CONTACT AREA AND PRESSURE AT THE ROTATOR CUFF FOOTPRINT? A BIOMECHANICAL STUDY

Various rotator cuff repair techniques have been developed to improve tendon-to-bone healing by increasing the contact area and pressure at the rotator cuff footprint. Rotator cuff repair with subacromial balloon augmentation may be an effective method to increase tendon-to-bone contact area and pressure. Therefore, it was the objective of this study to evaluate the contact area and pressure between a repaired rotator cuff tendon and bone for several different rotator cuff repair techniques, with and without subacromial balloon augmentation. The subacromial balloon spacer final fill volume and insertion portal were also varied to determine their effect on achieving optimal rotator cuff to footprint contact area and pressure. Ten cadaveric shoulders were mounted onto a biomechanical simulator which employed static muscle loading to the deltoid and rotator cuff. A full thickness supraspinatus tendon tear was simulated and repaired using a single-row, double-row, and transosseous equivalent (TOE) techniques. Each repair was first assessed without augmentation, followed by a subacromial ballon augmentation. The balloon spacers were evaluated with 60%, 80%, 100%, and 120% of their recommended final fill volumes (25mL). The orientation of the balloon spacer was examined by inserting the spacer through both lateral and posterior shoulder portals. A thin pressure sensor (Model 4201, Tekscan Inc, South Boston, MA, USA) was securely fixed to the supraspinatus footprint at the location of the tendon tear prior to testing and was used to evaluate contact area and pressure between the repaired tendon and bone for each variable assessed. Contact area and pressure outcomes were assessed using repeated measures analysis of variance with statistical significance set as P < 0.05. The greatest contact area and pressure was observed with the TOE repair technique, followed by double-row and single-row methods (Figures 1 & 2). Balloon spacer augmentation increased contact area for all repair types, but was only statistically significant for the single-row technique (P = 0.003). Increases in pressure were also observed when augmenting the single- and double-row repairs with the balloon spacer, although these increases were not statistically significant (P > 0.136). Insertion of the subacromial balloon spacer through a lateral portal produced greater contact area and pressure relative to insertion through a posterior portal. This trend was statistically significant for contact area (P = 0.007), but not pressure (P = 0.059). The subacromial balloon final fill volume was not found to have a significant effect on either contact area or pressure (P = 0.130). The optimal contact area and pressure were observed when using a TOE repair technique with a balloon spacer inserted through a lateral portal, with a final fill volume below that of the recommended final fill volume. Rotator cuff repair with subacromial balloon augmentation was found to increase the contact area between the repaired tendon and bone, with a significant increase observed after a single-row repair. Furthermore, reduced final fill volumes and insertion of the spacer through a lateral portal were also found to optimize contact area and pressure between the repaired tendon and bone. These findings suggest balloon-augmented rotator cuff repair may be effective for improving contact area, particularly when double-row or TOE repair is not feasible. For any figures or tables, please contact authors directly.