Tarsal coalition refers to the union two or more tarsal bones by osseous, fibrous or catilagenous connections. The commonest forms of tarsal coalition are talocalcaneal and calcaneonavicular. (1-3) (1,2,3). There is an approximate 2:1 male to female ratio for the condition. (1)
Injury Mechanism: Condition can begins embryologically however may only become symptomatic after the coalition ossifies or fibrous coalition develops. (4) Ossification occurs at different ages depending on the bones involved. Talonavicular between 3 and 5 years, calcaneonavicular between 8 and 12, and finally talocalcaneal occurs between 12 and 16 years. (1) Coalitions may be asymptomatic in up to 75% of patients.(4) These coalitions can subsequently cause problems in adulthood affecting mobility in the hindfoot and altering biomechanics and can be found incidentally with prolonged symptoms after ankle injuries.
Stress fracture, osteochondrosis, osteochondral dissecans, osteochondral lestion, ankle sprain, osteonecrosis, osteomyelitis.
Inspection: Gait may be antalgic secondary to affected side. Swelling may be present, a decreased arch may be present.
Palpation – may be tender over sustenaculum tali, dorsum of talar-navicular joint
AROM – May be normal
PROM – may reveal reduced subtalar movement however 50-60% of coalitions may be present bilaterally.(1)
AROM v. Resistance: May be weak on affected side with eversion or inversion v. resistance.
Ottawa ankle rules can be negative.
Exam may not be effective in localizing patient’s symptoms.
Xray – Plain radiographs can be used to identify coalitions, however often require further imaging. The following signs can be seen on plain radiographs:
Talar Beak Sign – A protrusion of the superior distal talus angled over the navicular seen on Lateral Xrays.
C-sign – A C-shaped appearance from the posterior aspect of the talus on lateral Xrays.
Anteater sign – Calcaneonavicular coalition – as the calcaneus does not normally articulate with the navicular. The projection of a calcaneal protusion towards the navicular on a lateral xray resembles the snout of an anteater.
Drunken waiter sign – The Sustenacula Tali shelf is angled either upward and downward resembling a waiter’s unsteady arm holding an un-level serving tray after a few drinks. This is a sign of hypoplastic sustenacula tali and is associated with talocalcaneal coalition.
Bonescan – Can be used in difficult cased that are difficult to localize the issue. It has also shown to be useful in determining middle facet coalitions in CT’s and MRI’s reported as normal.(3)
MRI – Identifies osseous, fibrous and cartilaginous coalitions. Superior to CT for non-osseous coalition visualization
CT – Excellent for identifying and characterizing osseous coalitions.
Conservative: Activity modification reducing impact activity with a period of rest 4-6 weeks. If no improvement consider a walking boot or short leg cast for another 4-6 weeks.(1)
Surgical: If conservative treatment fails to resolve symptoms, resection may be considered in mild to moderately symptomatic patients. A study of 304 talar coalition resection patients found only 14.1% required reoperation at a mean follow up of 9.5 years (4) Excision tends to be less predictable. If resection or excision fail arthrodesis may be required (1)
Dr. Neil Dilworth (July 28, 2014)
(1) Drennan’s the child’s foot and ankle. 2nd ed. ed. Philadelphia: Lippincott Williams & Wilkins; 2009.
(2) Iyer RS, Thapa MM. MR imaging of the paediatric foot and ankle. Pediatr Radiol 2013;43:107-119.
(3) Lawrence DA, Rolen MF, Haims AH, Zayour Z, Moukaddam HA. Tarsal Coalitions: Radiographic, CT, and MR Imaging Findings. HSS Journal 2014;10(2):153-166.
(4) Khoshbin A, Law PW, Caspi L, Wright JG. Long-term functional outcomes of resected tarsal coalitions. Foot & ankle international./ American Orthopaedic Foot and Ankle Society [and] Swiss Foot and Ankle Society 2013;34(10):1370-1375.