Summary

This study evaluate three different methods of rotator cuff tear repair augmentation, including a novel techniques

Abstract

Methods: Fifteen cadaveric shoulders were used for the comparison with 5 shoulders in each group. Each shoulder was prepared by removing the extrinsic shoulder muscles and sharply dissecting the supraspinatus from the humeral insertion. A conventional rotator cuff tear repair (RCTR) was performed with two anchors in the lateral aspect of the supraspinatus foot print using alternating simple and Modified Mason-Allen technique. The three augmentation techniques compared were: 1) ATR independently anchored to the humerus with two anchors lateral to the medial row alternating two simple sutures with two Modified mason-Allen sutures, 2) ATR anchored to humerus incorporating the rotator cuff and the ATR with two lateral anchors alternating simple and Mason Allen suture technique and 3) same as method 2 plus a third anchor was added lateral to subscapularis which was incorporated into the repair. Each repaired humerus was clamped in the test machine at 30° to the vertical and the supraspinatus was clamped in a tissue clamp and attached to the actuator of the Instron E3000 (Instron Corp, Norwood MA). The mechanical test consisted of a sinusoidal tensile load from 10 to 100 N in load control at 0.5 Hz for 200 cycles. Final load to failure was then performed in displacement control at a rate of 1.0 mm/sec. The monitoring of the stretch across the repair was performed with two digital variable reluctance transducers (DVRT’s) placed spanning the repair location, one side in the humerus and the other in the ATR. The voltages from the DVRT’s were captured on an A/D converter and stored on computer and synchronized with the measures of load and displacement from the Instron.
Results: A preexisting tear in one cadaver reduced the second group to 4 specimens. After cycling there was no evidence of residual stretch or gap formation in any of the groups. The subsequent measuring of the 5 mm “gap” employing the DVRT’s1 was actually a measure of the stretching of the soft tissues in the area. Also no statistically significant difference between the repair methods regarding the load reached after a 5 mm stretch was measured.
The final load to failure revealed that the technique with the subscapularis incorporated in the repair (41.7 ± 10.4 N/mm) was significantly stiffer (p = 0.046 N/mm) than the identical repair without the subscapularis incorporated (28.0 ± 3.6 N/mm), see Fig. 1. Repair 2 was less stiff than the first method (35.6 ± 10.4 N/mm) but not significantly so (p = 0.24). The third technique (856.8 ± 81.4 N) also was statistically significantly stronger (p = 0.046) than the first method (538.0 ± 156.1 N) that didn’t suture the ATR with the rotator cuff but not statistically stronger (p = 0.051) than the second method (687.0 ± 86.8 N) that did.Conclusion: The cyclic testing of the repairs did not result in any gap formation for the three repairs methods. As a result of this the conclusions from the study are based on the final test to failure that took place after 200 cycles of tensile loading. The incorporation of the subscapularis in the rotator cuff repair enhanced the stiffness of the repair as well as significantly increasing the force required to disrupt the repair.