A Biomechanical Comparison of the Modified Mason-Allen Stitch and Massive Cuff Stitch In Vitro

Abstract

The suture-tendon interface is generally regarded as the weak link in rotator cuff fixation. High rates of failure in arthroscopic rotator cuff repair have led to a search for strong yet easy-to-perform suture configurations. The goal of this study was to compare the strength of 2 commonly used suture configurations, the modified Mason-Allen stitch and the massive cuff stitch, when suture-anchored into bone. Fourteen sheep shoulders were harvested and the infraspinatus tendon isolated. Each infraspinatus tendon was split in half longitudinally along the axis of its fibers to yield 2 tendon-bone specimens per shoulder, for a total of 28 specimens. Each split tendon was then repaired by use of a double-loaded suture anchor with a modified Mason-Allen and simple suture in one specimen and the massive cuff stitch in the other. Each specimen was initially cyclically loaded on a vertical MTS uniaxial load frame (MTS Systems, Eden Prairie, MN) under force control from 5 to 30 N at 0.25 Hz for 20 cycles. Each specimen was then loaded to failure under displacement control at a rate of 1 mm/s. Peak-to-peak displacement, cyclic elongation, ultimate tensile load, stiffness, and mode of failure were recorded. A repeated-measures analysis of variance was performed, with an alpha level of significance set at P < .05. No statistically significant difference was found with regard to ultimate load to failure between the modified Mason-Allen stitch (110.4 +/- 55.1 N) and massive cuff stitch (116.4 +/- 37.9 N). In addition, no statistically significant difference was found with regard to cyclic elongation, peak-to-peak displacement, or initial displacement. The most common mode of failure for both suture configurations was suture pullout. The modified Mason-Allen stitch and massive cuff stitch yield similar biomechanical profiles when suture-anchored into bone. The massive cuff stitch may be a simpler and biomechanically equivalent alternative to the modified Mason-Allen stitch in arthroscopic rotator cuff repair.