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Updated: May 13 2023

Tarsal Coalition

Images
https://upload.orthobullets.com/topic/4068/images/anteater.jpg
https://upload.orthobullets.com/topic/4068/images/key image.jpg
https://upload.orthobullets.com/topic/4068/images/flatfoot.jpg
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https://upload.orthobullets.com/topic/4068/images/45-degree oblique.jpg
https://upload.orthobullets.com/topic/4068/images/talar beaking.jpg
  • summary
    • Tarsal Coalition is a common congenital condition caused by failure of embryonic segmentation leading to abnormal coalition 2 or more of the tarsal bones. The condition is usually asymptomatic, but may present with a flatfoot deformity or recurrent ankle sprains. 
    • Diagnosis is made with plain radiographs of the foot and ankle showing a coalition, most commonly a calcaneonavicular or talocalcaneous coalition.
    • Treatment is usually a course of casting and NSAIDs for symptomatic patients. Surgical coalition resection or joint arthrodesis is indicated for patients with persistent symptoms who fail conservative management. 
  • Epidemiology
    • Prevalence
      • varies from 1%-2%
    • Demographics
      • age of onset
        • calcaneonavicular usually 8-12 years old
        • talocalcaneal usually 12-15 years old
    • Anatomic location
      • calcaneonavicular (most common)
      • talocalcaneus
  • Etiology
    • Two types
      • congenital
        • most common
      • acquired
        • less common and caused by
          • trauma
          • degenerative
          • infections
    • Pathophysiology
      • embryology
        • failure of mesenchymal segmentation leading to coalition between two or three tarsal bones
          • develops into a fibrous coalition, or undergoes metaplasia to cartilage +/- bone
      • pathoanatomy
        • gait mechanics
          • subtalar joint will normally rotate 10 degrees internally during stance phase
            • in presence of coalition, internal rotation does not occur
        • deformity
          • flattening of longitudinal arch
          • abduction of forefoot
          • valgus hindfoot
          • peroneal spasticity (also known as peroneal spastic flatfoot)
        • pain generator theories
          • ossification of previously fibrous or cartilaginous coalition
          • microfracture at coalition bone interface
          • secondary chondral damage or degenerative changes
          • increased stress on other hindfoot joints
    • Associated conditions
      • nonsyndromic
        • autosomal dominant
      • syndromic
        • fibular hemimelia
        • carpal coalition
        • FGFR-associated craniosynostosis (FGFR-1, FGFR-2, FGFR-3)
        • Apert syndrome, Pfeiffer, Crouzon, Jackson-Weiss and Muenke
  • Classification
    • Anatomic classification
      • calcaneonavicular
        • between calcaneus and navicular bones (most common)
      • talocalcaneal
        • middle facet of talocalcaneal joint
    • Pathoanatomic classification
      • 3 types
        • fibrous coalition (syndesmosis)
        • cartilagenous coalition (synchondrosis)
        • osseous coalition (synostosis)
  • Presentation
    • History
      • history of prior recurrent ankle sprains
    • Symptoms
      • asymptomatic
        • most coalitions are found incidentally
        • 75% of people are asymptomatic
      • pain
        • location of pain
          • sinus tarsi and inferior fibula suggests calcaneonavicular
          • distal to medial malleolus or medial foot suggests talocalcaneal
        • pain worsened by activity
          • onset of symptoms correlates with age of ossification of coalition
        • calf pain
          • secondary to peroneal spasticity
    • Physical exam
      • inspection
        • hindfoot valgus
        • forefoot abduction
        • pes planus
      • range of motion
        • limited subtalar motion
        • heel cord contractures
        • arch of foot does not reconstitute upon toe-standing
          • hindfoot remains in valgus (does not swing into varus) upon toe-standing
      • special tests
        • reverse Coleman block test
          • evaluate for subtalar rigidity
  • Imaging
    • Radiographs
      • recommended views
        • required
          • anteroposterior view
          • standing lateral foot view
          • 45-degree internal oblique view
            • most useful for calcaneonavicular coalition
          • Harris view of heel
      • findings
        • calcaneonavicular coalition
          • "anteater" sign
            • elongated anterior process of calcaneus
        • talocalcaneal coalition
          • talar beaking on lateral radiograph
            • occurs as a result of limited motion of the subtalar joint
            • irregular middle facet joint on Harris axial view
          • c-sign
            • c-shaped arc formed by the medial outline of the talar dome and posteroinferior aspect of the sustentaculum tali
          • dysmorphic sustentaculum
            • appears enlarged and rounded
    • CT scan
      • Has been suggested as part of the preoperative workup to
        • rule-out additional coalitions
          • incidence approx. 5%
        • determine size, location and extent of coalition
          • size of talocalcaneal coalition based on size of posterior facet using coronal slices
    • MRI
      • may be helpful to visualize a fibrous or cartilaginous coalition
      • STIR sequences help to differentiate inflammatory changes (e.g. tendinitis) in local structures
  • Treatment
    • Nonoperative
      • observation, shoe inserts
        • indications
          • unclear.
        • techniques
          • medial arch support and preserved hindfoot alignment
        • outcomes
          • In rigid flat feet shoe inserts may be the cause of discomfort.
      • immobilization with casting, analgesics
        • indications
          • initial treatment for symptomatic cases
        • techniques
          • below-knee walking cast for six-weeks
        • outcomes
          • up to 30% of symptomatic patients will become pain-free with a short period of immobilization
    • Operative
      • coalition resection with interposition graft, +/- correction of associated foot deformity
        • indications
          • persistent symptoms despite nonoperative management
          • coalition involves <50% of joint surface area
        • techniques
          • open vs arthroscopic coalition resection
          • interposition material
            • extensor digitorum brevis (calcaneonavicular coalition)
            • split flexor hallucis longus tendon (talocalcaneal coalition)
            • interposed fat graft
            • bone wax
          • correction of associated hindfoot, midfoot or forefoot deformities
            • calcaneal osteotomy for hindfoot valgus
            • calcaneal lengthening to create arch after resection
            • heel cord lengthening if intraoperative ankle dorsiflexion is not past neutral
        • outcomes
          • 80-85% will experience pain relief
          • poor outcomes
            • coalition resection >50% size of joint surface area
            • uncorrected hindfoot valgus
            • associated degenerative changes
      • subtalar arthrodesis
        • indications
          • role has not been well established
          • consider if coalition involves >50 % of the joint surface of a talocalcaneal coalition
        • technique
          • open vs. arthroscopic
          • consider an associated calcaneal osteotomy with severe hindfoot malalignment
      • triple arthrodesis (subtalar, calcaneocuboid, and talonavicular)
        • indications
          • advanced coalitions that fail resection
          • diffuse associated degenerative changes affecting calcaneocuboid and talonavicular joints
        • technique
          • open vs. arthroscopic
  • Techniques
    • Calcaneonavicular coalition resection
      • approach
        • lateral or sloppy lateral position
        • anterolateral approach over coalition
      • incision
        • oblique incision just distal to subtalar joint
        • between extensor tendons and peroneal tendons
      • technique
        • protect branches of superficial peroneal and sural nerves
        • reflect fibrofatty tissues in sinus tarsi anterior and extensor digitorum brevis distally
        • identify coalition between anterior process of calcaneus and navicular bones and confirm with fluorscopy
        • excise bar with saw or osteotomes, which leaves defect ~1cm in size
        • interpose fat, bone wax or portion of extensor digitorum brevis muscle into defect
      • post-operative
        • short-leg, non-weight bearing cast for 3-4 weeks
    • Talocalcaneal coalition resection
      • approach
        • positioned supine
        • medial approach to hindfoot
      • incision
        • horizontal or curved incision centered over sustentaculum tali
        • between flexor digitorum longus and neurovascular bundle
      • technique
        • sustentaculum tali usually just plantar to the talocalcaneal coalition
        • identify normal subtalar joint cartilage by dissecting out the anterior and posterior facets
          • this will help determine location and size of coalition resection
          • confirm with two needles immediately anterior and posterior to coalition clinically and confirm with fluorscopy
        • resect coalition with high speed-burr, ronguers and curettes
        • invert and evert subtalar joint to demonstrate improvement in subtalar motion
        • interpose fat, bone wax or portion of flexor hallucis longus tendon into defect
      • post-operative
        • short-leg non-weight bearing cast for three weeks
  • Complications
    • Incomplete resection
    • Recurrence of the coalition
    • Residual pain or stiffness
      • due to malalignment or associated arthritis
      • due to unrecognized 2nd coalition - this should be identified by a preoperative CT scan
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