- Everted foot associated with peroneal muscle spasm, but not produced by muscle imbalance
- The syndrome consists of a painful, rigid valgus deformity of both the fore and hind parts of the foot and peroneal muscle spasm, but not true spasticity
Pathophysiology
- Often associated with calcaneo-talar or calcaneo-navicular bars (tarsal coalition) with a faulty pattern of movement in the subtalar joint producing pain and muscle spasm
- Talonavicular and subtalar coalition can coexist
- Tarsal coalition in the fetus occurring as a result of failure of differentiation and segmentation of primitive mesenchyme
- May also occur in inflammatory conditions such as Reiters disease and other inflammatory arthropathies, when there is involvement of the subtalar joint
Incidence
- Usually 12 – 16 years at presentation
- Males : Females 2:1
- Often bilateral
- Calcaneonavicular coalition is the most common, followed by the middle facet talocalcaneal coalition
Aetiology
- ? Fusion of accessory ossicles
- ? Failure of segmentation
- ? Autosomal dominant inheritance
Classification
- Talo-navicular
- Calcaneo-cuboid
- Calcaneo-navicular
- Talo-calcaneal
Clinically
- Presents with pain and gait disturbance as coalition ossifies
- Calcaneo-navicular age 8 – 12
- Talo-calcaneal age 12 – 16
- Peroneal and extensor tendons can be seen standing out on the lateral foot (not spastic, but adaptively shortened)
- May be associated with diffuse tenderness around the tarsus
- Ankle movement is normal, but subtalar movements are restricted or absent
X-Rays
- Evidence of a tarsal coalition may be seen on lateral radiographs, however oblique views or CT may be required
- Best seen in 45 oblique radiograph
- Degenerative joint disease may be evident in inflammatory conditions
Treatment
- Calcaneonavicular Coalition
- Initially conservative. Symptomatic patients initially treated with immobilization for 3 to 6 weeks, followed by an orthosis
- Refractory cases do well with calcaneonavicular bar resection
- Talocalcaneal Coalition
- Initially conservative. Symptomatic patients initially treated with immobilization for 3 to 6 weeks, followed by an orthosis.
- Surgical treatment for failure of conservative management
- If less than 50% of middle facet of subtalar joint is involved, excise the coalition
- If greater than 50% involved, perform an arthrodesis
- Bar excision in patients with a hindfoot in >20 degrees valgus is associated with worse outcomes and is a relative contraindication to excision
- Consider a medial wedge excision or lateral opening wedge calcaneal osteotomy to correct associated valgus heel
- Perform subtalar or triple arthrodesis if degenerative changes are present
- Older people with degeneration of the talo-navicular and subtalar joints : Triple arthrodesis
Prognosis
- Results can be expected to be good or excellent in about 75% of cases
- Best results are obtained in patients who had a cartilaginous coalition and who were less than 16 y/o at the time of the operation
