Torsional profiles of the lower limbs, such as femoral anteversion, can dictate gait and mobility, joint biomechanics and pain, and functional impairment. It currently remains unclear how the interactions between femoral anteversion, kinematics, and muscle activity patterns contribute to joint biomechanics and thus conditions such as knee pain. This study presents a computational modeling approach to investigating the interactions between femoral anteversion, muscle forces, and knee joint loads.We employed an optimal control approach to produce actuator and muscle-driven simulations of the stance phase of gait for femoral anteversion angles ranging from −8°(retroversion) to 52°(anteversion) with a typically developing baseline of 12°of anteversion and implemented a Monte Carlo analysis for variations in lower limb muscle forces. While total patellofemoral joint load decreased with increasing femoral anteversion, patellofemoral joint load alignment worsened, and knee abduction/adduction magnitude increased with both positive and negative changes in femoral anteversion (p < 0.001). The rectus femoris muscle was found to greatly influence patellofemoral joint loads across all femoral anteversion alignments (R > 0.8, p < 0.001), and the medial gastrocnemius was found to greatly influence knee abduction/adduction moments for the extreme version cases (R > 0.74, p < 0.001). Along with the vastus lateralis, which decreased with increasing femoral anteversion (R = 0.89, p < 0.001), these muscles are prime candidates for future experimental and clinical efforts to address joint pain in individuals with extreme femoral version. These findings, along with future modeling efforts, could help clinicians better design treatment strategies for knee joint pain in populations with extreme femoral anteversion or retroversion.

BACKGROUND Femoral derotational osteotomies are used by Orthopaedic surgeons to decrease anteversion in a variety of pathologies. Intraoperatively, the goal of the surgery is to decrease the rotation of the femur to within physiologic range. Surgeons generally visually estimate the angle of correction based off bone markers at the rotating cylindrical portion of the femur. This study sought to assess the inter-subject reliability between subjects and modalities with respect to alpha angle creation. METHODS A rotational femur model was constructed and tested amongst undergraduates, medical students, surgical residents and attendings. Subjects were asked to create angles of 15, 30, 45, and 60 degrees using only Kirschner wires and then only bone marks for reference. Two-tailed independent t-tests were performed to determine variability between cohorts, and effect size was calculated for significant results. RESULTS The participants were split into two cohorts: undergraduates and medical students in the ‘non-surgeon’ cohort, and surgical residents and attendings in the ‘surgeon’ cohort. The overall average angle creation error of the surgeon cohort was significantly lower than the non-surgeon cohort. The average angle creation range across all modalities and angles created was significantly lower in the surgeon cohort when compared to the non-surgeon cohort. The non-surgeon cohort was significantly more accurate with the wire modality as compared to the mark modality. The surgeon cohort had no significant difference in inter-modality average error. CONCLUSIONS The considerable inter-subject range within the surgeon cohort highlights a need for reinforcement of basic geometric principles within orthopaedic instruction. This model allows for immediate accurate feedback on angle creation. The physiologic range allows for a degree of variability between surgical outcomes without consequence. However, the more than twenty-degree range determined by this study does not fall within those bounds and should be addressed. Moving forward, rotational estimation as a surgical skill should increase in prominence within orthopaedic instruction, and additional emphasis should be placed on fundamental spatial orientation during training.