Biomechanical evaluation of arthroscopic rotator cuff stitches.

Abstract

The suture configurations in arthroscopic rotator cuff repairs have been limited to simple and horizontal stitches. Recent objective evaluations have demonstrated high failure rates of arthroscopic repairs of rotator cuff tears. A novel stitch for arthroscopic repair of the rotator cuff, the massive cuff stitch, was developed to increase the strength of the suture-tendon interface. The goal of this study was to determine the biomechanical properties of the massive cuff stitch and to compare it with other stitches commonly used for rotator cuff repair. Eight pairs of sheep infraspinatus tendons were harvested and split in half to yield a set of four tendon specimens from each animal. Four stitch configurations (simple, horizontal, massive cuff, and modified Mason-Allen) were randomized and biomechanically tested in each set of tendon specimens. Each specimen was first cyclically loaded on an MTS uniaxial load frame under force control from 5 to 30 N at 0.25 Hz for twenty cycles. Each specimen was then loaded to failure under displacement control at a rate of 1 mm/sec. Cyclic elongation, peak-to-peak displacement, ultimate tensile load, and stiffness were measured with use of an optical motion analysis system and load-cell output. The type of failure (suture breakage or pull-out) was also recorded. A repeated-measures analysis of variance was performed on the results, with the alpha level of significance set at p < 0.05. There was no difference in cyclic elongation or peak-to-peak displacement among the four stitches. Ultimate tensile load was significantly higher (p < 0.05) for the massive cuff stitch (233 +/- 40 N) and the modified Mason-Allen stitch (246 +/- 40 N) than it was for either the simple stitch (72 +/- 18 N) or the horizontal stitch (77 +/- 15 N). There was no significant difference in the ultimate load between the massive cuff and modified Mason-Allen stitches. There was also no difference in stiffness among the four stitches. The simple and horizontal stitches failed by tissue pull-out, whereas the massive cuff and Mason-Allen stitches failed by a mixture of suture breakage and pull-out. The massive cuff stitch provides strength comparable with that of the modified Mason-Allen stitch commonly used in open rotator cuff repair. The ultimate tensile load before failure of the massive cuff stitch was significantly higher (p < 0.05) than that of the simple and horizontal stitches.