Biomechanical Comparisons of Three Posterior Cruciate Ligament Reconstruction Procedures with Load-Controlled and Displacement-Controlled Cyclic Tests

BACKGROUND: Biomechanical behaviors of posterior cruciate ligament reconstructions under cyclic loading have not been sufficiently clarified. HYPOTHESIS: Biomechanical behaviors of the reconstruction that involves use of flexor tendons and an Endobutton are significantly different under cyclic loading from behaviors of the two standard reconstructions in which bone-patellar tendon-bone graft is used. STUDY DESIGN: Controlled laboratory study. METHODS: In a porcine model, the tendon/Endobutton reconstruction, the tendon-bone/interference screw reconstruction, and the tendon-bone/tibial-inlay reconstruction were biomechanically compared by using two cyclic tests. In each group of 15 specimens, 5 knees underwent tensile testing without cyclic loading, and the remaining 10 underwent the same tensile test after 5000 cycles of load-controlled or displacement-controlled loading. RESULTS: At the 5000th cycle, the peak displacement or the peak load was affected by each type of cyclic loading to a significantly greater degree in the knees with the tendon/Endobutton procedure than in the knees reconstructed with the other two procedures. CONCLUSIONS: Plastic deformation occurred more easily during cyclic loading in the knees with the tendon/Endobutton reconstruction than in the knees with the tendon-bone reconstructions. CLINICAL RELEVANCE: When the tendon/Endobutton reconstruction is used, a longer period of postoperative immobilization is necessary.