Is a Plantarflexed First Ray the Primary Deformity In Children With Cavovarus Feet Secondary to Charcot-Marie-Tooth Disease? A Pedobarographic Analysis

Abstract

Background: Charcot-Marie-Tooth disease (CMT) is a common cause of cavovarus foot deformity in children. This deformity is often quoted as being forefoot driven, with a primary deformity of first ray plantarflexion driving the hindfoot into varus by virtue of the tripod effect of the foot, which was hypothesized by Coleman and is commonly assessed clinically using his eponymous block test. The primary goal of this study was to objectively investigate this hypothesis using dynamic pedobarography. Methods: A review of the gait lab archives at a large tertiary referral center was carried out to identify children with CMT who had foot photos and dynamic pedobarographic data. Two orthopaedic surgeons then determined the weight-bearing hindfoot alignment of these children using clinical photography. The order of contact during gait of the first metatarsal relative to the fifth metatarsal was then obtained from the dynamic pedobarographic data. Results: One hundred eighteen feet from 60 children with CMT met the study inclusion criteria. Sixty-eight varus feet were compared with 50 nonvarus feet. First ray contact occurred before fifth ray contact in only 39.7% of the varus feet compared with 34.0% of the nonvarus feet, which did not meet statistical significance (P=0.526). Conclusions: In this cohort, dynamic pedobarography did not consistently demonstrate the first metatarsal contact occurring before the fifth metatarsal contact in children with varus feet secondary to CMT. While nearly 40% of the feet did make initial contact on the first ray, 60% of the feet landed in varus before the first ray made contact, leading us to believe that the foot is prepositioned in varus. This may be in part due to the progressive muscle imbalance and secondary deformity that has occurred. Surgical management of these children should take this.