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

Purpose: To perform a biomechanical comparison of single-row rotator cuff repairs with modified suture configurations versus double-row repairs using radiostereometric analysis (RSA). Methods: 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. Results: 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 ≤ .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). Conclusions: 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. Clinical Relevance: 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.