Radiological findings of fibrocartilaginous coalition of the third tarsometatarsal joint: a retrospective cross-sectional study with computed tomography and magnetic resonance imaging.

BACKGROUND: Fibrocartilaginous coalition of the third tarsometatarsal joint has been indicated as an extremely rare form of tarsal coalition in the radiological literature, and most articles concerned with tarsal coalition do not mention involvement of this joint. Only two reports written in the English language that approach this subject were found, an orthopedic report and an anthropological report. PURPOSE: To evaluate the prevalence of this finding and discuss and illustrate the radiological characteristics of this coalition. MATERIAL AND METHODS: A retrospective analysis of 614 computed tomography or magnetic resonance imaging scans of the ankle and/or foot, acquired at a health service within a period of three months, was performed to assess the prevalence of this coalition. RESULTS: Of the examinations characterized as valid for analysis for the purposes of the study, 17 cases compatible with fibrocartilaginous coalition of the third tarsometatarsal joint were found, thus indicating an involvement of approximately 2.97% of the examined feet. CONCLUSION: Our radiological findings are typical, and the prevalence found in this study was statistically significant, being similar to that described in the anthropological report (3.2%-6.8%).