Surgical outcomes of cavovarus foot deformity in children with Charcot-Marie-Tooth disease
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.
Section snippets
Study design and participants
This is a pre- and post-operative cohort study involving all patients enrolled in the Australasian Paediatric CMT Registry who were treated surgically for cavovarus foot deformity at The Children's Hospital at Westmead (Sydney, Australia) by a single surgeon (P.G.) from January 2006 to August 2017. Written informed consent was obtained from all participants’ parents or guardians in accordance with the requirements of the Human Research Ethics Committee, and when appropriate, participant's
Participant characteristics
Table 2 presents the baseline demographic, anthropometric and clinical characteristics of the sample. Twenty-one consecutive children and adolescents (13 males, mean age at the time of surgery 12.5 years, SD 2.7, range 8–16 years) included in the study were surgically treated for cavovarus foot deformity at The Children's Hospital at Westmead (Sydney, Australia) by a single surgeon (P.G.) between January 2006 and August 2017. None were excluded. As part of the Inherited Neuropathies Consortium,
Discussion
The main findings of this study were that cavovarus foot surgery in children with CMT significantly improves foot alignment, ankle dorsiflexion flexibility, and frequency of trips and falls. Strength, function and quality of life did not significantly improve with surgery, and generally mirrored the natural course of the disease. Preliminary data suggests an improvement in plantar pressure loading beneath the rearfoot and midfoot following cavovarus foot surgery.
Direct comparison with the
Acknowledgements
The authors wish to thank the staff and patients of The Children's Hospital at Westmead (Peripheral Neuropathy Management Clinic and Paediatric Gait Analysis Service of New South wales) for their support and ongoing contributions to the data registry that made this study possible.
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