Surgical outcomes of cavovarus foot deformity in children with Charcot-Marie-Tooth disease

Highlights

• First comprehensive study to investigate surgical outcomes in children with CMT.

• Cavovarus surgery improved foot alignment, ankle flexibility, and daily trips/falls.

• Plantar pressure loading improved beneath the rearfoot and lateral midfoot.

• Strength, function and quality of life generally mirrored the natural course of CMT.

Abstract

Charcot-Marie-Tooth disease (CMT) causes disabling cavovarus foot deformity. Orthopaedic surgery is performed in severe cases; however few studies have investigated whether surgery improves health outcomes during childhood. This study investigated the impact of cavovarus surgery on validated physical, functional, parent/self-reported and biomechanical measures in 21 consecutive patients (mean age at surgery 12.5 years, SD 2.7) evaluated before and after surgery (mean duration 15.7 months, SD 5.9), and compared to natural history data from 206 children with CMT. Measures from the CMT Pediatric Scale evaluated foot alignment (Foot Posture Index), ankle flexibility (lunge test), strength (foot dorsiflexion/plantarflexion by hand-held dynamometry), function (balance, long jump, 6-minute walk test) and self-reported symptoms. Quality of life (Child Health Questionnaire) and gait (pressure loading) were also assessed. Foot Posture Index and lunge improved with surgery by 6.0 points (SD 3.2) and 6.1° (SD 7.3) respectively (p< 0.01), and differed to the natural course of the disease (p< 0.005). Self-reported daily trips/falls reduced from 60% to 13% (p = 0.016). Pressure improved beneath the rearfoot and midfoot (p = 0.043). Surgery had no effect on strength, function or quality of life, which generally mirrored the natural course. Cavovarus surgery improved foot alignment, ankle flexibility and self-reported trips/falls in children with CMT.

Introduction

Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of inherited peripheral neuropathies affecting 3–82 per 100,000 individuals of both sexes and all backgrounds [1]. CMT is characterised by demyelination and/or axonal degeneration of the peripheral nerves, with typical onset in the first two decades of life [2], [3]. More than 90 causative genes have been identified so far, and CMT type 1A is the most common subtype [4]. Most patients exhibit a length-dependent progression of symptoms and impairments, with symptoms initially distal at the feet and hands, progressing proximally. The clinical phenotype is characterised by progressive muscle weakness, atrophy, sensory deficits and skeletal deformities. Foot deformities, such as cavovarus (highly-arched) and clawed toes, are observed in patients with CMT in 60–90% of cases [5], [6], [7]. The cavovarus foot deformity commonly features an excessively high medial longitudinal arch that does not flatten on weight bearing, varus (inverted) rearfoot and a plantarflexed (downward) position of the first metatarsal, adducted forefoot, claw toes and secondary contracture of the plantar fascia [8]. A flexible deformity usually develops during childhood, and is often bilateral, painful and becomes increasingly severe and rigid as the disease progresses [9]. Imbalance of foot and ankle musculature is thought to play a critical role in the development of cavovarus foot deformity [10], [11], whereby the length-dependent nerve degeneration affects the intrinsic foot muscles, progressing to selected extrinsic lower leg muscles responsible for foot eversion and dorsiflexion (e.g., peroneus brevis muscles and tibialis anterior). Whilst the foot invertors and plantarflexors (e.g., tibialis posterior, triceps surae and peroneus longus muscle) remain relatively stronger and overpower the opposing evertors and dorsiflexors resulting in an adducted forefoot, inverted rearfoot and plantarflexed first metatarsal [10].

There are a multitude of physical, functional, psychosocial and biomechanical sequelae of the cavovarus foot deformity associated with CMT during childhood. These include ankle contracture, impaired balance and power, foot pain, unsteady ankles, frequent trips and falls, poor walking ability and decreased endurance [12], [13], [14]. Health-related quality of life is also commonly affected in children with CMT who have cavovarus foot deformity [15]. Furthermore, patients commonly exhibit abnormal plantar pressure loading during gait which are significantly related to callosities, foot pain and stress fractures [16].

As yet there is no disease modifying therapy to reverse or halt the progression of CMT during childhood. Symptomatic management of cavovarus deformity is often necessary to ameliorate symptoms, improve impairments and maintain function. These interventions include orthotic therapy to accommodate the deformity, improve pressure loading and reduce foot pain [13], [17], physiotherapy such as stretching, mobilisation, splinting and serial casting to increase ankle flexibility [14], [18] and progressive resistance exercise to improve or maintain muscle strength [19]. Surgical management of the cavovarus deformity is often indicated when symptomatic management has failed. Indications may include inability fitting orthoses and footwear due to severity of foot deformity and ankle contracture, recurrent musculoskeletal complications such as trips/falls and pain, significant gait impairment, day-to-day limitations such as walking difficulties and fatigue. The goals of surgery are to produce well-aligned, plantigrade and functional feet by correcting the bony deformity (via osteotomies) and rebalancing the deforming muscles (via soft tissue transfers). Surgical decisions are individualised and multifaceted. An overview of the common types of surgical procedures for cavovarus foot deformities is summarised in Table 1.

Whilst a variety of surgical procedures for cavovarus deformity have been described in the literature [20], [21], [22], [23], [24], very few studies have evaluated the impact of foot surgery on health outcomes in children with CMT. The evidence base on surgical management of cavovarus deformity in CMT includes case reports or case series that are limited by small sample size [21], [24], [25], [26], [27], mixed cohorts of paediatric and adult patients [20], [21], [23], [27], [28], [29], [30], heterogeneous cavovarus aetiology with a subset of CMT cases [21], [26], [31], [32], primarily radiographic outcomes [21], [30], [32], or non-validated measures [26], [31]. There is a need to longitudinally evaluate the impact of cavovarus foot surgery on paediatric patients with CMT using validated and multifaceted outcome measures. Therefore, the aim of this study was to investigate the effect of cavovarus foot surgery on validated physical, functional, parent/self-reported and biomechanical outcome measures in affected children and adolescents before and after surgery, and compared to the natural course of the disease.