DIAPHYSEAL TIBIOFIBULAR SYNOSTOSIS: A TRAPEZOIDAL BONEY BRIDGE BETWEEN THE TIBIA AND FIBULA — ANATOMICAL, BIOMECHANICAL, AND CLINICAL CORRELATIONS

Abstract

Introduction: Tibiofibular synostosis (TS) is a rare anatomical variation characterized by bony fusion between the tibia and fibula. When located in the diaphyseal region, it is termed diaphyseal tibiofibular synostosis (DTS). TS can be associated with multiple osteochondromas, a rare autosomal dominant condition, and can cause anterior leg compartment pain, especially in athletes, due to repetitive microfractures and biomechanical alterations of the fibula during gait. Objective: To report a case of diaphyseal tibiofibular synostosis (DTS) with a trapezoidal morphology in dry bones, correlating it with its anatomical, biomechanical, and clinical implications. Case Report: During academic-scientific activities at the Anatomy Laboratory of the Federal University of Sergipe, a DTS was identified in a left lower limb, located in the middle third of the leg. The trapezoidal bony bridge originated from the lateral surface of the tibia with a maximum height of 28 mm, progressively tapering to 23 mm in its intermediate portion and 21 mm at the fibular insertion. The superior, middle, and inferior widths were 15 mm, 12 mm, and 7 mm, respectively, totaling an approximate area of 261 mm². The superior margin presented a regular curvature with cranial concavity; the inferior margin exhibited an irregular contour with a bony spicule adjacent to the fibula. Areas of bone callus suggestive of previous fractures were observed, indicating a post-traumatic etiology. Conclusion: DTS is a rare condition, highly relevant in athletes, whose understanding is essential for the differential diagnosis and clinical management of anterior leg pain.