BIOMECHANICAL EVALUATION OF ARTHROSCOPIC ROTATOR CUFF STITCHES IN CHRONIC RUPTURED HUMAN ROTATOR CUFFS VERSUS INTACT CUFFS: AN IN VITRO STUDY.

Abstract

Background: Recent studies of arthroscopic rotator cuff repairs have shown high failure. The different suture configurations were mostly tested in non degenerative animal tendon specimen. We used instead fresh-frozen degenerative human cadaver rotator cuffs. The goal of this study was to determine the biomechanical properties of commonly used arthroscopic stitches in ruptured human cuffs in comparison to intact rotator cuffs.

Method: 36 human rotator cuff tendons were harvested, documented according to size, thickness and location of rupture, and divided into a ruptured and non ruptured specimen group. We found 12 ruptured and 24 intact cuffs. Three stitch configurations (simple, horizontal, and massive cuff stitch) with a Fiber Wire 2 (Arthrex) were randomized and biomechanically tested in each set of tendon specimen. The specimen were mounted on a uniaxial load machine (ZM200, Fa Shokoohi) and loaded to failure under displacement control at a rate of 0.6 mm/sec. Ultimate tensile load, and type of failure were recorded.

Results: Ultimate tensile load was significantly higher (p < 0.05) for the massive cuff stitch (186 ± 12 N) than it was for either the simple stitch (102 ± 9 N) or the horizontal stitch (138 ± 10 N) in the intact cuff cohort. In the ruptured cuff group ultimate tensile load was significantly lower (p < 0.05) for the massive cuff stitch (115 ± 12 N), the simple stitch (77 ± 9 N), and the horizontal stitch (103 ± 10 N) in comparison to the intact cuff group. The simple and horizontal stitches failed by tissue pull-out in both groups, whereas the massive cuff failed by pull-out and once by suture breakage in the group of intact cuffs.

Conclusion: Ruptured rotator cuffs showed significant less biomechanical strength concerning all three stitches in comparison to the intact cuff group. Overall the massive cuff stitch showed superior ultimate tensile load.