Tarsal Coalition

Tarsal Coalition is a disorder of mesenchymal segmentation that leads to fusion of two or three tarsal bones and lead to a deformity of rigid flatfoot.

The tarsal coalition might be:

• Bony (synostosis).
• Cartilaginous (synchondrosis).
• Fibrous (syndesmosis).

Tarsal Coalition is either congenital which is the most common type, or acquired which is less common and caused by trauma, degenerative or infections.

Tarsal Coalition’s forms are primarily a talocalcaneal or calcaneonavicular coalition:

• Calcaneonavicular coalition is most common in children 9 to 12 years of age.
• Talocalcaneal coalition is more common in children 12 to 14 years of age.

See Also: Tarsal Tunnel Syndrome

Deformity in Tarsal Coalition:

1. Medial longitudinal arch flattening.
2. Forefoot abduction.
3. Hindfoot valgus.
4. Peroneal spasticity.
5. Absence of internal rotation of the subtalar joint during walking.

See Also: Anatomical Deformities in Hallux Valgus

Possible causes of pain:

Possible causes of pain in Tarsal Coalition include:

1. Ossification of previously fibrous or cartilaginous coalition
2. Micro-fracture at coalition bone interface.
3. Secondary chondral damage or degenerative changes.
4. Increased stress on other hindfoot joints.

Calcaneonavicular coalition

Calcaneonavicular coalition is the most common form. It is most common in children 9 to 12 years of age (but it probably presents since birth).

The abnormal bar runs from the anterior process of the calcaneus just lateral to the anterior facet dorsally and medially to the lateral and dorsolateral extraarticular surface of the navicular. Bar usually is 1.0 to 2.0 cm long × 1.0 to 1.2 cm wide.

The talar head might appear small and underdeveloped. Beaking of the dorsal articular margin of the talus (uncommon).

The symptoms usually are:

• Dorsolateral foot pain centering around the sinus tarsi.
• Difficulty walking on uneven surfaces.
• Foot fatigue.
• Occasionally a painful limp.
• Hindfoot valgus, some loss of the longitudinal arch, peroneal spasm varying degrees of loss of subtalar motion are present in most adolescent patients.

Imaging Study:

X-Ray Views: AP view, Standing lateral foot view, 45-degree internal oblique view and Harris view of heel.

Findings: Ant eater sign elongated anterior process of the calcaneus.

CT scan: Determine size, location and extent of coalition.

MRI: It’s helpful to visualize a fibrous or cartilaginous coalition.

Tarsal Coalition Treatment:

Observation and shoes with medial arch support in asymptomatic flatfoot patients. A trial of reduced activity or cast immobilization or both is th initial treatment for symptomatic cases.

Surgery is done with coalition Resection with interposition of muscle (extensor digitorum brevis) or fat. It’s indicated if persistent symptoms despite prolonged period of nonoperative management and coalition involves <50% of joint surface area.

In advanced case, failed resections, and patients with multiple coalitions, triple arthrodesis is often required.

2. Talocalcaneal coalition

Talocalcaneal coalition is a bridge of bone between the sustentaculum of calcaneus and talus. It is less common than calcaneonavicular coalition. It’s more common in children 12 to 14 years of age. The talocalcaneal bridge ossifies either completely or incompletely when an individual is between 12 and 16 years old.

Symptoms and clinical examination:

• Foot fatigue and pain around the hindfoot on increased activity.
• Loss of the longitudinal arch.
• Peroneal spasm frequently is present
• Marked reduction or absence of subtalar motion (compared to calcaneonavicular bar, which may allow varying degrees of subtalar motion).
• Tenderness in the sinus tarsi, over the talonavicular joint, along the peroneal tendons, and especially medially over the sustentaculum tali.
• Heel valgus and loss of the normal longitudinal arch usually occur.

Imaging Study:

X-Ray Views: AP view, Standing lateral foot view, 45-degree internal oblique view, Harris view of heel.

Findings include:

1. Talar beaking on lateral radiograph
2. C-sign: c-shaped arc formed by the medial outline of the talar dome and posteroinferior aspect of the sustentaculum tali
3. Dysmorphic sustentaculum appears enlarged and rounded

CT scan: Determine size, location and extent of coalition. Size of talocalcaneal coalition based on size of posterior facet using coronal slices

MRI is helpful to visualize a fibrous or cartilaginous tarsal coalition.

Talocalcaneal coalition Treatment:

Nonoperative with reduced activity 4 to 6 weeks in a short-leg walking cast followed by a period of wearing firm arch supports. Possibly a corticosteroid injection within the sinus tarsi.

Coalition Resection with interposition of muscle (extensor digitorum brevis) or fat: it’s indicated in persistent symptoms despite prolonged period of nonoperative management, and coalition involves <50% of joint surface area.

Subtalar arthrodesis: If more than 50% of the middle facet is involved.

In advanced case, failed resections, and patients with multiple coalitions, triple arthrodesis is often required.

References & More

1. Campbel’s Operative Orthopaedics 12th edition Book.
2. Millers Review of Orthopaedics -7th Edition Book.
3. Kulik SA Jr, Clanton TO. Tarsal coalition. Foot Ankle Int. 1996 May;17(5):286-96. doi: 10.1177/107110079601700509. PMID: 8734800.