Three-dimensional evaluation of the cyclic loading behavior of different rotator cuff reconstructions.

Abstract

To perform a biomechanical comparison of single-row rotator cuff repairs with modified suture configurations versus double-row repairs using radiostereometric analysis (RSA). The infraspinatus tendon and the humerus of 40 porcine cadaveric shoulders were marked with tantalum beads and placed in an RSA calibration cage that allows for calculation of 3-dimensional positions of the tantalum markers. The intact tendon was cyclically loaded (50 cycles/20 N). After sharp dissection of the infraspinatus from the bone, the repairs were made by use of 3 single-row (modified Mason-Allen, double mattress, inclined mattress) and 2 double-row (modified Mason-Allen, suture bridge) configurations. The reconstructions were cyclically loaded for 50 cycles (10 N to 40, 60, 80, and 100 N). Displacements under cyclic loading were quantified in the anteroposterior (x), craniocaudal (y), and mediolateral (z) direction. The craniocaudal measurements were compared with the results of a video extensometer. Cyclic loading of the intact tendon showed a mean displacement of 0.06 +/- 0.08 mm at the x-level, 0.16 +/- 0.18 mm at the y-level, and 0.19 +/- 0.28 mm at the z-level. High correlations between the RSA and the video extensometer measurements were found (0.87). Comparison of rotator cuff repairs showed significant differences in gap formation at 40, 60, 80, and 100 N in the craniocaudal plane (P < .0001) and the mediolateral plane (P <or= .05), with the double-row Mason-Allen repair providing the lowest gap formation of all tested configurations. However, these results were not statistically significant compared with the single-row double-mattress repair. No significant differences were measured at the anteroposterior level (P > .05). Single-row repairs using modified Mason-Allen or double-mattress repair were able to achieve biomechanical results comparable to double-row repairs as measured by RSA and digital video. Single-row repairs, using modified suture configurations, were able to decrease implant costs compared with double-row repairs, by achieving comparable results. Furthermore, RSA gives additional information on the applied forces acting on the rotator cuff repair in 3 different planes, which may help to decrease the rerupture rate of rotator cuff reconstructions.