Intersegmental dynamics imbalance in gait impairments of children with spastic hemiplegia: insights from different torque contribution

Challenges in the rehabilitation of gait impairments among children with spastic hemiplegia (CSH) suggest significant difficulties in controlling lower limb intersegmental dynamics (ISD), which may be closely associated with underlying proprioceptive and neuromuscular impairments. To quantify the ISD imbalance of lower limb in CSH, we developed a novel protocol utilizing motion capture and kinetic analysis to assess multi-joint torque contributions during the gait cycle. In this prospective, hospital and school-based, case-control study, 21 typically developing children (age = 7.7 ± 1.2 years, 15 boys and 6 girls) and 21 children with spastic hemiplegia (age = 7.9 ± 1.7 years, 14 boys and 7 girls) were tested. The kinematic and kinetic data were collected synchronously and gait parameters were analyzed. The intersegmental dynamics analysis was conducted by a customized program based on ISD formulation. The knee flexion angles (p = 0.045) and ankle dorsiflexion angles (p<0.001) of CSH were significantly lower than TDC. The Co-direction Ratio (CDR) of external contact torque of CSH was significantly lower than TDC (p = 0.015) during the first double stance phase. During the single stance phase, the CDR of hip external contact torque (p = 0.042), knee muscle torque p = 0.014), knee interactive torque (p < 0.001) of CSH were significantly greater than TDC. The net impulse of knee external contact torque (p < 0.001) and knee muscle torque (p < 0.001) of CSH were significantly greater than TDC. The net impulse of ankle gravitational torque of CSH was significantly lower than TDC (p = 0.03) during the swing phase. A mismatch between muscle and passive torques may be associated with gait disturbance of CSH, characterized by a pathological shift in leading joint (hip to knee), inefficient passive torque utilization, and excessive yet ineffective muscle contractions. The findings suggest the potential relevance of rehabilitation strategies that focus on improving coordination during the stance phase and enhancing gravitational torque utilization during the swing phase.