16 year old with foot pain.
Plain films: Frontal, lateral and oblique views of the right foot reveal pes planus with osseous fusion of the navicular and cuboid bones. There is close approximation of the adjacent calcaneocuboid and calcaneonavicular articulations with sclerotic changes.
CT Scan: Axial images of the right foot demonstrate bony fusion of the navicular and cuboid bones with fibro-osseous fusion of the calcaneonavicular and calcaneocuboid articulations. These joint spaces are markedly narrowed and surrounded by sclerotic changes.
Tarsal coalition is characterized by abnormal osseous, fibrous, or cartilaginous fusion between two or more tarsal bones. The prevalence of tarsal coalition is estimated to be less than one percent, and it is bilateral in 50-60% of cases (1). Patients often present in adolescence with vague mid-foot pain, flatfoot, and limited motion of the subtalar joint (2). An everted foot with painful inversion has classically been described in relation to tarsal coalition as “peroneal spastic flatfoot,” but this may occur without coalition (3).
The most common types of tarsal coalitions in decreasing prevalence are calcaneonavicular, talocalcaneal, talonavicular, and calcaneocubiod. Other coalitions are much less common. Radiographic evidence of tarsal coalition varies based on the involved articulation. Calcaneonavicular coalition is best assessed with a 45 degree oblique view and may exhibit an osseous bridge between the calcaneous and navicular bones on the lateral view dubbed the “anteater sign.” Talocalcaneal coalitions occur mostly at the middle facet and are classically associated with beaking of the talus and the “C sign” on the lateral view, although the sensitivity of this finding is low (4). Even though radiographs are a valuable screening tool with good sensitivity in detecting tarsal coalition (5), computed tomography is the current gold standard for imaging diagnosis and is better at detecting non-osseous coalitions and the extent of joint involvement (6).
Asymptomatic coalition may be treated with non-operative therapy and orthotics, but this will not correct the underlying anatomic abnormalities. The treatment of choice for calcaneonavicular and talocalcaneal coalitions is resection of the fused articulation and inter-position of the extensor digitorum to prevent re-fusion (2). Subtalar fusion or “triple arthrodesis” is reserved for cases in which surgical resection has failed (7).
- Vincent KA. Tarsal Coalition and Painful Flatfoot. J Am Acad Orthop Surg 1998;6:274-281
- Sullivan JA, Pediatric Flatfoot: Evaluation and Management. J Am Acad Orthop Surg 1999;7:44-53
- Harris, EJ, et al. Diagnosis and Treatment of Pediatric Flatfoot. J Foot Ankle Surg. 2004 Nov-Dec;43(6):341-73.
- Taniguchi A, et al. C Sign for Diagnosis of Talocalcaneal Coalition. Radiology. 2003 Aug;228(2):501-5. Epub 2003 Jun 20.
- Crim JR, Kjeldsberg KM. Radiographic Diagnosis of Tarsal Coalition. AJR Am J Roentgenol. 2004 Feb;182(2):323-8.
- Upasani VV, Chambers RC, Mubarak SJ. Analysis of calcaneonavicular coalitions using multi-planar three-dimensional computed tomography. J Child Orthop. 2008 Aug;2(4):301-7. Epub 2008 Jul 2.
- Bohne WH. Tarsal coalition. Curr Opin Pediatr. 2001 Feb;13(1):29-35.