3D-Evaluation der biomechanischen Eigenschaften verschiedener Rekonstruktionen der Rotatorenmanschette

In a biomechanical laboratory study, various rotator cuff reconstructions were compared in three different planes (dorsoventral, craniocaudal, mediolateral) using radiostereometric analysis (RSA). The infraspinatus tendon and the humeral head were marked with tantalum beads and RSA measurements were performed using two X-ray machines simultaneously at a 90° angle and a special calibrating cage. After cyclic loading of the intact tendon with 20 N, different single-row and double-row reconstructions were performed and cyclically loaded for 50 cycles between 10 to 40, 60, 80, and 100 N. Elongation under cyclic loading was calculated using radiostereometric analysis and a video extensometer which was used as the reference method in the craniocaudal plane. Cyclic loading of the intact tendon showed a mean dislocation of 0.06±0.08 mm in the x-plane, 0.16±0.18 mm in the y-plane and 0.19±0.28 mm in the z-plane. Highly significant differences were found in the craniocaudal plane between the tested fixations at 40, 60, 80, and 100 N (p<0.0001). Significant differences were also found in the mediolateral plane (p<0.05). No significant differences were seen in the dorsoventral plane (p<0.05). Comparing the results obtained by RSA in the craniocaudal plane and the video extensometer showed high correlations in the Pearson correlation coefficient (0.87). In conclusion, radiostereometric analysis is an excellent method to evaluate the cyclic loading behavior of different rotator cuff reconstructions. Measurements in three different planes allow the shear forces on the tested fixations to be examined.