NMBL - Neuromuscular Biomechanics Lab

Movement Abnormalities -- Internal Rotation Gait

Children with cerebral palsy frequently walk with excessive internal rotation of the hip. Spastic medial hamstrings or adductors, among other factors, are thought to contribute to the excessive internal rotation in many patients based on evidence from electromyographic recordings. Surgical lengthening of these muscles is often expected to decrease excessive internal rotation. However, the extent to which the hamstrings, adductors, and other hip muscles contribute to hip internal rotation is unclear, and the changes in hip rotation following surgery are inconsistent. We have performed a series of investigations to determine which muscles have the greatest potential to rotate the hip. We found that the medial hamstrings or adductors are unlikely to be important contributors to excessive internal rotation of the hip. This work has provided new biomechanical guidelines for the treatment of excessive hip internal rotation.

We have used our MR-based and deformable models to examine other possible causes of excessive hip internal rotation. Based on these analyses, we believe that the exaggerated hip flexion of patients, which dramatically increases the internal rotation moment arms of the gluteus medius and gluteus minimus, is more likely than the hamstrings or adductors to cause abnormal internal rotation. This conclusion is consistent with our measurements of hip rotation moment arms in cadaver specimens. Additional simulations have shown that anteversion and valgus deformities of the femur decrease the abduction moment arm of the gluteus medius substantially, and that this moment arm can be restored with internal rotation of the hip. Hence, it is also feasible that hip internal rotation is a compensatory mechanism adopted by some children with femoral deformities to preserve abduction capacity.
		A graphics-based model of the lower extremity animated with gait kinematic data of a subject with excessive internal rotation of the hip.

Associated Publications

Arnold and Delp. Computer modeling of gait abnormalities in cerebral palsy: application to treatment planning. Theoretical Issues in Ergonomics Science, 2005. (Download PDF)

Arnold and Delp. Rotational moment arms of the medical hamstrings and adductors vary with femoral geometry and limb position: implications for treatment of internally-rotated gait, Journal of Biomechanics, 2001. (Download PDF)

Arnold, Asakawa, Delp. Do the hamstrings and adductors contribute to excessive internal rotation of the hip in persons with cerebral palsy, Gait and Posture, 2000. (Download PDF)

Delp, Hess, Hungerford, Jones. "Variation of Rotational Moment Arms with Hip Flexion."Journal of Biomechanics, 1999. (Download PDF)

Schmidt, Arnold, Carroll, and Delp. "Length Changes of the Hamstrings and Adductors Resulting from Derotational Osteotomies of the Femur." Journal or Orthopaedic Research, 1999. (Download PDF)

Arnold, Komattu, Delp. Internal rotation gait: A compensatory mechanism to restore abduction capacity decreased by bone deformity? Developmental Medicine and Child Neurology, 1997. (Download PDF)