Posterior facet talocalcaneal coalition

Talocalcaneal coalition: A focus on radiographic findings and sites of bridging

BACKGROUND

Verifying the exact location of talocalcaneal (TC) coalition is important for surgery, but the complicated anatomy of the subtalar joint makes it difficult to visualize on radiographs. No study has used computed tomography (CT) or magnetic resonance imaging (MRI) to verify the radiological characteristics of TC coalition or those of different facet coalitions. Therefore, this study verified the radiological findings used to identify TC coalitions and those of different facet coalitions using CT and MRI.

MATERIALS AND METHODS

Plain with/without weight bearing anteroposterior and lateral radiographs, CT, and MRI of 43 feet in 39 patients with TC coalitions were reviewed retrospectively. CT or MRI was used to verify the location of the TC coalition. Secondary signs for the presence of a coalition in the anteroposterior and lateral plain radiographs, including talar beak, humpback sign, duck-face sign, and typical or deformed C-sign, were evaluated. Three independent observers evaluated the radiographs twice at 6-week intervals to determine intraobserver reliability. They examined the radiographs for the secondary signs, listed above, and coalition involved facets.

RESULTS

The average rates from both assessments were as follows: Middle facet 5%, middle and posterior facets 27%, and posterior facet 68%. The deformed C-sign is more prevalent in posterior facet coalitions. The posterior facet has the highest prevalence of involvement in TC coalitions, and the deformed C-sign and duck-face sign have high correlations with TC coalitions in the posterior subtalar facet.

CONCLUSION

A posterior facet is the most prevalent for TC coalition, and the C-sign is useful for determining all types of TC coalition.

[Dorsomedial talocalcaneal coalition: a rare condition]

Talocalcaneal coalitions are rare but a posterior facet talocalcaneal coalition is even rarer. There are three different types: fibrous, cartilaginous and osseous coalitions. Besides conventional x-rays computed tomography is essential for assessment of the subtarsal joint. In the absence of concomitant coalitions and foot deformity resection of the coalition is advocated due to good clinical results when there is an adequate size of the talocalcaneal joint (>50%) and without osteoarthrosis. A case of a rare posterior facet talocalcaneal coalition is reported.

The types of talar articular facets and morphometric measurements of the human calcaneus bone on Turkish race

INTRODUCTION

There are three facets over upper side of talocalcaneal joint: anterior talar facet, middle and posterior. Three types of calcaneus that have distinct talar facets were defined as types A, B and C.

MATERIALS AND METHODS

A total of 221 calcanei (98 right, 123 left), with unknown gender, were dried and evaluated.

RESULTS

In our study type B calcaneus (58%) was defined as the most common type, and type A calcaneus (39.3%) as the second most common type. By using facet joint differences and bone measurement, we tried to define calcaneus bone.

DISCUSSION

In many diseases of foot, such as the talocalcaneal artritis and coalition, intraarticular fractures and congenital dysmorphology, flatfood, valgus deformities, the size and shape of the bones, the relationships of the talus and calcaneus with each other and other bones of the foot must be considered for the internal and external fixation and surgical procedures. Type B calcaneus was defined as the most comman type in Turkish race and these results correlate with the ones which were performed on bones of American, Indian and African people, and it was uncorrelated with the results of the researches performed in Europe.

Anatomy of the subtalar joint and imaging of talo-calcaneal coalition

Talo-calcaneal coalitions may be intra-articular or extra-articular in position and may be classified as fibrous, cartilaginous or osseous in morphology. Fibrous coalitions, particularly extra-articular talo-calcaneal coalitions, may have cross-sectional imaging findings that resemble normal anatomic variants, particularly the medial talo-calcaneal ligament and to a lesser extent the presence of an accessory articular facet between the posterior margin of the sustentaculum and postero-medial process of the talus. Typically, in the adult fibrous coalition, there will be some osseous deformity at the entheses, allowing differentiation from a medial talo-calcaneal ligament. The anatomy of the subtalar joint and its ligamentous supports, normal anatomic variations and their corresponding imaging appearance are reviewed in the first part of this article. In the second part, the various forms of talo-calcaneal coalition and their imaging appearance are reviewed.

Radiographic diagnosis of posterior facet talocalcaneal coalition

Tarsal coalition is a relatively common segmentation abnormality of the hindfoot that can result in foot and ankle pain in both adolescents and adults. The most common types are calcaneonavicular and talocalcaneal. Posterior subtalar facet coalition is less common. We present a 10-year-old boy with a history of chronic left ankle and foot pain. Radiographs demonstrated calcaneal "humpback" sign, representing the posterior subtalar bony coalition, and CT demonstrated in more detail the extent of bony and fibrous coalition. These findings led to surgical intervention.