Selective voluntary motor control influences knee joint torque, work and power in children with spastic cerebral palsy.

BACKGROUND: Children with spastic cerebral palsy (CP) have damage to the corticospinal tracts that are responsible for selective motor control (SMC). Force, velocity and timing of joint movement are related biomechanical features controlled by the corticospinal tracts (CSTs) that are important for skilled movement. RESEARCH QUESTION: Does SMC influence knee joint biomechanics in spastic CP? METHODS: In this prospective study, relationships between SMC and knee biomechanics (peak torque, total work, average power) across a range of velocities (0-300 deg/s) were assessed using an isokinetic dynamometer in 23 children with spastic CP. SMC was assessed using Selective Control Assessment of the Lower Extremity (SCALE). Logistic and linear regression models were used to evaluate relationships between SCALE and biomechanical measures. RESULTS: The ability to produce knee torque diminished with increasing velocity for both Low (0-4 points) and High (5-10 points) SCALE limb score groups (p < 0.01). More knees in the High group produced extension torque at 300 deg/s (p < 0.05) and flexion torque at 30, 90,180, 240 and 300 deg/s (p < 0.05). The ability to produce torque markedly decreased above 180 deg/s for Low group flexion. For knees that produced torque, significant positive correlations between SCALE limb scores and joint torque (0 and 120 deg/s), work (120 deg/s) and power (120 deg/s) were found (p < 0.05). Greater knee torque, work and power for the High group was found for the extensors at most velocities and the flexors for up to 120 deg/s (p < 0.05). Few Low group participants generated knee flexor torque above 120 deg/s limiting comparisons. SIGNIFICANCE: Biomechanical impairments found for children with low SMC are concerning as skilled movements during gait, play and sport activities occur at high velocities. Differences in SMC should be considered when designing individualized assessments and interventions.

Gait outcomes following proximal tibial tumor resection and endoprosthetic reconstruction.

BACKGROUND: Despite the proximal tibia being a common site of primary malignant bone tumors, there is limited information about gait function following proximal tibial tumor resection and endoprosthetic reconstruction (PTR). RESEARCH QUESTION: What is the impact of PTR on gait and quality of life? METHODS: This was a cross-sectional study of patients ≥18 years old who were ≥2 years post-PTR compared to a control group of similar age and sex distribution. Eighteen participants (9 PTR, 9 Control) were recruited. Gait spatial-temporal data, joint kinematics and kinetics were collected at preferred and fast walking speeds. Community walking cadence, health-related quality of life (SF-36) and knee joint torque were assessed. Comparisons were performed using one-way ANOVAs with Bonferroni corrections for multiple comparisons. Nonparametric tests were used for data not normally distributed. RESULTS: Mean age was 31 years for each group (PTR range = 18-42 yrs, Control range = 18-44 yrs). Compared to both control and nonsurgical limbs, the surgical limb exhibited significantly decreased % single limb support time, reduced heel rise during terminal stance and an absence of normally occurring knee flexion angles, extensor moments and power generation during initial double limb support. Additionally, a reduced peak plantar flexor moment was found for the surgical as compared to the control limb. The number of gait abnormalities increased during fast walking. Significantly reduced surgical knee extensor torque on isokinetic testing and weakness of the knee and ankle on clinical examination support gait findings. During community walking, the number of low frequency strides was an average of 5.3 % greater for the PTR group (p <  0.05). Norm-based PTR group SF-36 component scores were within normal values (53.4 physical, 56.5 mental). SIGNIFICANCE: Gait abnormalities were consistent with ankle muscle resection and transposition and knee extensor mechanism disruption. Despite these deficits, walking speed and quality of life were relatively normal.