Congruity of the subtalar joint in tongue fracture of the calcaneus: An anatomical study

Study Design: An anatomic study. Objectives: To evaluate the effect of displacement of the fractured posteri or facet in tongue fracture of the calcaneus on the congruity of the subtal ar joint, Methods: Eleven feet were used in this study. Seven females and four males with age range from 59 to 78. The specimens were dissected from both the la teral and the medial aspects of the calcaneus to expose these surfaces. A p rimary fracture line was created first, then a secondary line was engineere d to simulate tongue fracture. Displacement of the superio-lateral fragment was done with 5-mm increment. Radiography was performed and the graphs wer e scanned and studied on specific computer software to explore the effects of displacement on joint congruity. Results: The anterior end of the fragment of the tongue fracture, when disp laced, not only is depressed but also rotated in the sagittal plane in a do wnward or planterward direction. The articular surface of the posterior fac et of the calcaneus and the inferior facet of the talus are maintained in c ongruence with each other despite the varying degree of displacement and ro tation. Conclusion: Congruity of the subtalar joint in tongue fractures is maintain ed despite different degrees of displacement. This study explains why the n on-surgical treatment outcome is comparable to that of the operative treatm ent in tongue fractures of calcaneus. It also explains why tongue fractures have a good outcome with closed reduction.