71928
document
Risk of anterior cruciate ligament fatigue failure is increased by limited internal femoral rotation during in vitro repeated pivot landings . BACKGROUND A reduced range of hip internal rotation is associated with increased peak anterior cruciate ligament ( ACL ) strain and risk for injury . It is unknown , however , whether limiting the available range of internal femoral rotation increases the susceptibility of the ACL to fatigue failure . HYPOTHESIS Risk of ACL failure is significantly greater in female knee specimens with a limited range of internal femoral rotation , smaller femoral-ACL attachment angle , and smaller tibial eminence volume during repeated in vitro simulated single-leg pivot landings . STUDY DESIGN Controlled laboratory study . METHODS A custom-built testing apparatus was used to simulate repeated single-leg pivot landings with a 4×-body weight impulsive load that induces knee compression , knee flexion , and internal tibial torque in 32 paired human knee specimens from 8 male and 8 female donors . These test loads were applied to each pair of specimens , in one knee with limited internal femoral rotation and in the contralateral knee with femoral rotation resisted by 2 springs to simulate the active hip rotator muscles ' resistance to stretch . The landings were repeated until ACL failure occurred or until a minimum of 100 trials were executed . The angle at which the ACL originates from the femur and the tibial eminence volume were measured on magnetic resonance images . RESULTS The final Cox regression model ( P = .024 ) revealed that range of internal femoral rotation and sex of donor were significant factors in determining risk of ACL fatigue failure . The specimens with limited range of internal femoral rotation had a failure risk 17.1 times higher than did the specimens with free rotation ( P = .016 ) . The female knee specimens had a risk of ACL failure 26.9 times higher than the male specimens ( P = .055 ) . CONCLUSION Limiting the range of internal femoral rotation during repetitive pivot landings increases the risk of an ACL fatigue failure in comparison with free rotation in a cadaveric model . CLINICAL RELEVANCE Screening for restricted internal rotation at the hip in ACL injury prevention programs as well as in individuals with ACL injuries and/or reconstructions is warranted .
71929
Intervention_Educational
A custom-built testing apparatus