Background

 

 

 

Definition

 

A fixed equinus deformity of the forefoot in relation to the hindfoot 

 

Abnormally high arch that fails to flatten with weight bearing

 

Etiology

 

Neuromuscular - two thirds of condition with Charcot-Marie-Tooth (CMT) most common

Congenital - congenital cavo-varus, residual club foot, arthrogryposis

Traumatic - compartment syndrome, foot fracture malunion

Degenerative - arthritis of hindfoot

Idiopathic

 

Neuromuscular causes

Central	Spinal cord	Anterior horn cell	Peripheral nerves	Muscle disease
Friedreich's Ataxia Cerebral Palsy Hydrocephalus	CMT type 2 Spina bifida Syringomyelia Spinal cord tumours	Polio SMA	CMT type 1	Muscular dystrophy

 

Charcot-Marie-Tooth

 

Inherited disorder of nerves

- most common inherited neurological disorder

- heterogenous group

- characterised by weak muscles and abnormal sensation

- positive family history

CMT Type 1	CMT Type 2
Demyelinating disorder of peripheral nerve roots	Degeneration of spinal axons Primary axonal neuropathy
Most common 80%	Second most common 20%
Glove and stocking parasthesia Absent reflexes Claw toes, cavus feet, stork legs Loss of intrinsics in hand	Reflexes intact

 

Deformity

 

Rang Tripod concept

 

Heel, 1st MTPJ and 5th MTPJ must all touch the ground

 

If 1st MTPJ plantaflexed the heel must move into varus

 

Imbalance is the key to understanding

 

Cavus foot	Varus hindfoot	Clawed toes
Weak Tibialis anterior	Strong Tibialis posterior	Weak intrinsics
EHL / EDL plantar flex first ray Equinus forefoot	Brings heel into varus Allows lateral column to sit on floor	MCPJ hyper-extended Toes flexed
Plantar fascia contracts Fixed cavus deformity

 

History

 

Metatarsalgia

Lateral ankle instability - weak P brevis / hindfoot varus

Pain from claw toes

Foot numbness

Difficulty shoewear

 

Neurological examination

 

CMT - stork legs, high stepping gait, abnormal sensation, reflexes

Spina bifida - examine spine

 

Stork legs of CMT

 

Examination

 

Cavus foot

 

Varus hindfoot

 

Aim is to determine stage

1. Flexible cavus / flexible 1st metatarsal

2. Fixed 1st metatarsal equinus / mobile hindfoot varus

3. Fixed hindfoot varus

4. Bony changes

 

Flexible / correctable cavus / plantaflexed first metatarsal

 

Plantarflexion corrects with pressure on 1st metatarsal

 

Flexible / correctable hindfoot varus

 

Coleman Block  / Lateral Block Test

- block under lateral foot so first ray touches the ground

- eliminates forefoot deformity

- if hindfoot corrects the hindfoot is flexible

 

Correctable hindfoot

 

Differential diagnosis

 

Bilateral	Unilateral	Calcaneocavus
Central	Peripheral / local	Calcaneum is dorsiflexed
Spina bifida Spinal cord tumour	Polio Clubfoot Incomplete spinal cord Compartment syndrome

 

X-ray

 

Meary's angle

- longitudinal talus axis - 1st metatarsal angle 

- normal 0^o

- cavus > 30^o

 

 

Calcaneal Pitch

- normal 20^o or less

- > 30^o abnormal

 

 

MRI spine

 

Exclude spinal dysraphism

 

NCS

 

Can help diagnose CMT