The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force - A biomechanical analysis

To determine if untreated grade III injuries of the posterolateral structur es contribute to increased force on an anterior cruciate ligament graft, we measured the force in the graft in cadaveric knees during joint loading af ter reconstruction with otherwise intact structures and in the same reconst ructed knees after selected cutting of specific posterolateral knee structu res. Tests were first performed on the knee with the posterolateral structu res intact and then after sequential sectioning of the fibular collateral l igament, popliteofibular ligament, and popliteus tendon. The graft force wa s significantly higher after fibular collateral ligament transection during varus loading at both 0 degrees and 30 degrees of knee flexion than it was for the same loading of the joint with intact posterolateral structures. I n addition, coupled loading of varus and internal rotation moments at 0 deg rees and 30 degrees of flexion further increased graft force beyond that wi th varus force alone. The increase in graft force remained significant with additional sequential cutting of the popliteofibular ligament and popliteu s tendon. We believe this study supports the clinical observation that untr eated grade III posterolateral structure injuries contribute to anterior cr uciate ligament graft failure by allowing higher forces to stress the graft .