Posterior Cruciate Ligament Response to Proximal Tibia Impact 2019-01-1221

Posterior cruciate ligament (PCL) injuries, although rarely life threatening, affect the quality of life of the person who sustains the injury. The PCL is the primary restraint to posterior tibial translation and can be injured when the tibia moves posteriorly relative to the femur. This type of injury is can occur in frontal crashes where the tibia may impact the dashboard or steering column. The purpose of this study was to quantify the PCL response to realistic dynamic loading of the tibial plateau in isolated cadaveric lower limb experiments by simulating frontal impacts for seated vehicle occupants. A fixture was designed to mimic lower extremity loading characteristics seen in frontal crashes. Isolated cadaveric lower limbs (n = 14) were impacted near the tibial plateau at dynamic rates with a linear pneumatic ram. The specimens were impacted at 1.4 and 2.9 m/s with two different knee flexion angles. During the testing, a static load was applied to the quadriceps tendon to simulate active musculature and forces. A micro-differential variable reluctance transducer was inserted into the PCL to measure the stretch of the PCL and high-speed video was recorded. Following testing, each specimen was dissected to identify injuries to the ligaments of the knee joint and the lower extremity bones. The lower extremity stiffness values for the tests at impact velocities of 1.4 and 2.9 m/s were on average 120 N/mm and 141 N/mm, respectively. Using a two-way repeated measures ANOVA, it was found that stiffness was significantly different for the two impact velocities (p = 0.018) but not for the knee flexion angles. The most common injuries were tibia fractures and PCL tears. The study presents biofidelity targets for the response of the cadaveric limbs, which can be used in the development of anthropomorphic test devices or computational models.