Recurrence of knee flexion contracture after surgical correction in children with cerebral palsy

American Society of Biomechanics Clinical Biomechanics Award 2021: Redistribution of muscle-tendon work in children with cerebral palsy who walk in crouch

BACKGROUND

Previous study showed the triceps surae exhibits spring-like behavior about the ankle during walking in children with cerebral palsy. Thus, the work generated by the triceps surae is diminished relative to typically developing children. This study investigated whether the quadriceps offset the lack of triceps surae work production in children with cerebral palsy who walk in crouch.

METHODS

Seven children with cerebral palsy (8-16 yrs) and 14 typically developing controls (8-17 yrs) walked overground at their preferred speed in a motion analysis laboratory. Shear wave tensiometers were used to track patellar and Achilles tendon loading throughout the gait cycle. Tendon force measures were coupled with muscle-tendon kinematic estimates to characterize the net work generated by the quadriceps and triceps surae about the knee and ankle, respectively.

FINDINGS

Children with cerebral palsy generated significantly less triceps surae work when compared to controls (P < 0.001). The reverse was true at the knee. Children with cerebral palsy generated positive net work from the quadriceps about the knee, which exceeded the net quadriceps work generated by controls (P = 0.028).

INTERPRETATION

There was a marked difference in functional behavior of the triceps surae and quadriceps in children with cerebral palsy who walk in crouch. In particular, the triceps surae of children with cerebral palsy exhibited spring-like behavior about the ankle while the quadriceps exhibited more motor-like behavior about the knee. This redistribution in work could partly be associated with the elevated energetic cost of walking in children with cerebral palsy and is relevant to consider when planning treatments to correct crouch gait.

Grice extra-articular subtalar fusion for spastic pes planovalgus

INTRODUCTION

A pes planovalgus deformity, an unstable foot deformity, affects the gait of children with cerebral palsy (CP). Treatments, including subtalar fusion, were proposed. The Grice procedure maintains foot stability, but bone graft non-union poses a challenge. This study aimed to identify the rate and factors related to post-operative bone graft non-union.

METHODS

Thirty-one paediatric CP patients (age, 8.9 ± 1.8 years) who underwent the Grice procedure (53 feet) using ipsilateral tibial bone grafts were reviewed. Pre-operative gross motor function classification system (GMFCS) classes were class 1 in five, 2 in five, 3 in 14, and 4 in seven patients. Standing foot radiographs were assessed for signs of non-union, and parameters (talocalcaneal and talar declination angles and talar head uncovering index) measured pre-operatively, post-operatively, and at the most recent evaluation were compared. Factors associated with bone graft non-union were analysed by regression analysis. P < 0.05 was considered statistically significant. Degenerative changes in hindfoot joints were evaluated by Bargon's criteria.

RESULTS

At the average follow-up evaluation at 5.4 ± 4.3 years, the GMFCS class was improved or was maintained in 29/31 patients. Post-operative radiographic measurements were restored and were maintained over the follow-up period (P < 0.001). A total of 14/53 feet (26%) had non-union. The pre-operative lateral talocalcaneal angle (OR 1.08, p = 0.04) and follow-up duration (OR 1.18, p = 0.03) were identified in univariate analysis as potential factors related to non-union but were not confirmed in a multivariate model. Hindfoot joints in most feet showed mild degenerative changes.

CONCLUSION

Grice subtalar fusion in patients with a higher pre-operative lateral talocalcaneal angle might lead to bone graft non-union.