EVALUATION OF A BIODEGRADABLE SUBACROMIAL BALLOON SPACER ON GLENOHUMERAL JOINT BIOMECHANICS IN THE SETTING OF IRREPARABLE SUPERIOR ROTATOR CUFF TEARS

摘要

Purpose: The purpose of this study was to investigate the biomechanical effects of the biodegradable subacromial balloon spacer on the gleno-humeral joint in the setting of irreparable superior rotator cuff tears. Methods and Results: Seven fresh-frozen cadaveric shoulders were tested. Each specimen was tested with: intact rotator cuff, simulated supraspinatus (SS) tear, repaired SS tear, repaired SS tear with balloon spacer augmentation, irreparable SS rotator cuff tear simulation, and irreparable SS rotator cuff tear with balloon spacer. Measurements were recorded in 30° external rotation, at 0°, 30°, and 60°. Glenohumeral joint and subacromial space contact pressures and position were measured using a dynamic pressure sensor. The deltoid force significantly increased by placing the balloon compared to the irreparable supraspinatus tear model. At 0° it increased from 38.6 N to 41.25 N, at 30° from 33.8 N to 37.8 N and at 60° from 25.6 N to 28.5 N. In the balanced load condition: testing irreparable SS rotator cuff tear with balloon spacer significantly inferiorized the center of contact pressure of the glenohumeral joint at 0°, 30° and 60° abduction compared to the irreparable SS tear by 10.6 mm, 8.6 mm and 5.9 mm respectively. At 0° it also increased glenohumeral contact pressure to 105.3 kPa from 49 kPa in the irreparable SS model. The intact glenohumeral contact pressure was 60.7 kPa, which was lower than the balloon plus SS tear. There were no statistically significant differences between total glenohumeral contact pressures at 30° and 60° abduction. Conclusion: With irreparable supraspinatus rotator cuff tears, the balloon spacer inferiorizes the center of glenohumeral pressure and increases the overall glenohumeral pressure compared to an irreparable rotator cuff state, re-establishing similar glenohumeral contact pressures and position of the normal intact rotator cuff.