Biomechanics of hip injuries in frontal motor -vehicle crashes.

Abstract

This research was conducted to quantify the force required to cause hip fracture, to determine the knee loading conditions that produce hip injuries in frontal crashes, and to develop new injury assessment criteria that allow forces measured by crash test dummy femur and acetabular load cells to be used to accurately assess the risk of knee-thigh-hip injury in motor-vehicle crash tests. Biomechanical testing with specimens from unembalmed human cadavers was performed to determine the injury tolerance of the hip to loading applied to the anterior surface of the flexed knee as a function of hip posture. Hip fracture force data from these tests were used to develop injury risk curves, which relate force applied to the hip to the likelihood of hip fracture. These injury risk curves were combined with data from existing studies on the tolerances of the knee and distal femur to determine forces associated with a 35% risk of injury to all parts of the knee-thigh-hip complex. Symmetric impacts to the knees of whole unembalmed cadavers were performed to collect data that were used to develop and validate a mathematical model that can predict knee impact forces and the decrease in force along the knee-thigh-hip complex under knee impact loading. Simulations with this model demonstrated that, for the majority of knee loading conditions that occur in frontal crashes, the force associated with a 35% risk of hip injury was exceeded before the forces associated with 35% risks of injury to the other parts of the knee-thigh-hip complex were exceeded. Models of the THOR-NT and Hybrid III crash test dummies were also developed and used with the cadaver model in simulations to develop improved injury assessment criteria for these dummies. The new injury assessment criteria define combinations of peak force and impulse, determined from crash test dummy femur and acetabular load cell force measurements, that are associated with a risk of clinically significant injury to the knee-thigh-hip complex that is less than or equal to 35%.