Tarsal coalition

definition

· syn. peroneal spastic flat foot

· fibrous, cartilagenous or bony connection of two or more tarsals

· congenital origin

epidemiology

· true incidence not known but thought to be

· present in 6% of population

· symptomatic in 1% of population

· bilateral in 50%

· likely to be autosomal dominant with variable penetrance

· may be associated with

· symphalangism

· other gross limb anomalies

aetiology

· result of failure of differentiation and segmentation of primitive mesenchyme

pathology

· most common is calcaneonavicular bar

· middle facet of talocalcaneal joint is next most common

· uncommon in other tarsals

· multiple coalitions may occur

· valgus deformity leads to adaptive shortening of peroneal tendons

· may cause reflex spasm of tendon

clinical features

Symptoms

· majority are asymptomatic and remain so in adulthood

· if symptomatic, symptoms usually develop in adolescence

· usually when bar ossifies

· 8-12 in calcaneonavicular

· 12-16 in talocalcaneal

· due to reduction in subtalar movement and joint stress

· vague aching pain

· aggravated by activity

· may be frequent ankle sprains

Signs

· reduced subtalar motion (esp. talocalcaneal bar)

· pes planus

· valgus heel with talocalcaneal bar

· peroneal tendons may be shortened but rarely spastic

radiology

Plain x-rays

Standard

· AP, lateral and oblique views

· oblique often diagnostic in calcaneonavicular

· may see ossified bar

· may see elongated process on calcaneus or prolongation of navicular

· talocalcaneal dificult to see

· may see secondary changes on lateral view

· talar beaking

· broadening of lateral talar process

· blurring of subtalar joint

Special

· to visualise talocalcaneal

· difficult to perform and interpret

CT scan

· superior technique

· accurate

· easy

· provides reference of other side

· gives idea of nature of coalition

· reveals multiple coalitions

· hips and knees flexed and feet on table

differential diagnosis

· any condition that injures subtalar joint

· traumatic

· arthritic

· infectious

· flexible flat foot

treatment

Nonoperative

· successful in 1/3 of cases

· aimed at relieving subtalar joint of stress

· avoidance of aggravating activities

· moulded longitudinal arch support

· if fails, try short leg walking cast for 3-6 weeks

Operative

Indications

· persistent pain

Options

· resection of bar

· triple arthrodesis

· criteria for resection

· young (< 12 yrs)

· absence of complete bony bar

· bar involving < 50% of joint

· absence of degenerative changes

Calcaneonavicular

· very amenable to resection

· most do well

· technique

· dorsolateral approach

· resection of rectangle of bone 1 cm long

· interposition of fat or extensor digitorum brevis into defect

Talocalcaneal

· traditionally thought

· resection more difficult

· results less predictable

· results good if indications observed

· technique

· medial approach

· between FDL and neurovascular bundle

· resection of bone until middle facet seen