Abstract
Background: Specific anatomic variations of the ankle mortise may predispose people to ankle sprains.
Hypothesis: There is a correlation between a higher malleolar index (posteriorly positioned fibula) and incidence of ankle sprain.
Study Design: Prospective case control study.
Methods: We compared the malleolar index (transverse plane of the talus) on computerized axial tomographic images of 61 patients with ankle sprain with that of 101 normal controls. A positive number for the malleolar index meant that the lateral malleolus was posterior to the plane of the medial malleolus. A negative number meant that the lateral malleolus was actually anterior to the plane of the medial malleolus.
Results: The average malleolar index of the patients with ankle sprain was +11.5° with a standard deviation of 7°. Malleolar relationships varied from —6° to +39°, a range of 45°. The average malleolar index in the control group was +5.85° with a standard deviation of 4.9°, which varied from —8° to +16°. However, there was no correlation between recurrence of sprains and malleolar index values.
Conclusion: Patients with an ankle sprain were more likely to have a posteriorly positioned fibula, possibly predisposing them to ankle sprain.
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