Cruciate injury patterns in knee hyperextension: A cadaveric model

We created an experimental model to evaluate the effects of strain rate on the mechanism of combined cruciate ligament injuries in knee hyperextension . Using straight knee hyperextension to rupture the anterior and posterior cruciates, two strain rates (approximately 100% per second and 5400% per se cond) were applied to reproduce two clinical injury patterns of the knee: l ow energy (sporting) and high energy (pedestrian-motor vehicle accident). T en pairs of fresh-frozen cadaveric knees were injured to 45 degrees of hype rextension. Strain rate sensitivity of the posterior cruciate ligament was shown in this model, with midsubstance tears occuring in specimens tested a t a low rate and avulsion "stripping" injuries from the femoral side occuri ng at a high rate. A variable pattern of anterior cruciate ligament tears a t both high and low rates suggests that the specific injury mechanism may a lso involve other factors including notch morphology. We present a simplifi ed mathematic model used to estimate posterior cruciate Ligament strain dur ing knee hyperextension.