Influence of surgery involving tendons around the knee joint on ankle motion during gait in patients with cerebral palsy

Abstract

Category: Ankle Introduction/Purpose: The gastrocnemius, a biarticular muscle that crosses the knee and ankle, acts as a knee flexor as well as an ankle plantar flexor. Although simultaneous motion of the knee and ankle joints is required for many activities including standing, running, swimming, and cycling, the change in ankle motion during gait has not been described in patients with cerebral palsy who underwent distal hamstring lengthening or distal hamstring lengthening with rectus femoris transfer. Therefore, we aimed to evaluate the influence of surgery involving tendons around the knee on ankle motion during gait in cerebral palsy patients. Methods: The analysis included data regarding 55 limbs from 34 patients with spastic cerebral palsy, who were followed-up after they had undergone distal hamstring lengthening with or without additional rectus femoris transfer. Mean age of the patients at time of the knee surgery was 11.2 ± 4.7 years. Preoperative and postoperative kinematic variables that were extracted from three-dimensional gait analyses were compared to assess the change in ankle motion after surgery involving tendons around the knee. The postoperative 3D gait analysis was performed at a mean of 0.9 ± 1.3 years after the surgery. The outcome measures were relevant kinematics parameters including peak ankle dorsiflexion at initial contact, peak ankle dorsiflexion during stance, ankle peak dorsiflexion during swing, and dynamic range of motion of the ankle. A linear mixed model was constructed to estimate the changes in ankle motion after adjusting for multiple factors. Results: We estimated that peak ankle dorsiflexion at initial contact, peak ankle dorsiflexion during stance, ankle peak dorsiflexion during swing, and dynamic range of motion of the ankle decreased, respectively, by 0.4º (p=0.016), 0.6º (p<0.001), 0.2º (p=0.038), and 0.5º (p=0.006) per degree increase in total range of motion of the knee after knee surgery (Table). Estimated ankle peak dorsiflexion in the swing phase increased by 0.4º per degree increased in postoperative peak knee flexion in the swing phase (Table). Age at the time of the knee surgery did not significantly affect ankle kinematics. Conclusion: Improvement in total knee range of motion was correlated with a decrease in ankle kinematics after surgery involving tendons around the knee. Knee surgery may reduce the need for an additional surgical procedure involving the ankle joint. Because the simultaneous motion of the knee and ankle joints is cross-linked, surgeons should be aware of potential changes in the ankle joint after knee surgery.