The morphology of medial malleolus and its clinical relevance

Objective: To provide morphological data of medial malleolus to decrease the possibility of posterior tibial tendon injury and inadvertent ankle penetration. Methods: Computed tomography scans of the ankle in 215 patients were reviewed. Then parameters in the 3-D reconstruction images were measured by three independent, qualified observers on two separate occasions. Results: The average angle between tibia plafond and the articular facet of the medial malleolus was 55.88±4.11°. The distance from the most anterior point of the anterior colliculus to the center of the intercollicular groove was 11.68±1.13 mm. And the average angle between the bimalleolar axis and the articular facet of the medial malleolus was 76.61±2.04°. Significant differences were observed in the distance from the most anterior point of the anterior colliculus to the center of the intercollicular groove between males and females. (P 0.05) All of the parameters exhibited moderate to excellent intra-class correlation coefficient (ICC). Conclusions: According to this study, the insertion angle is much smaller than previously believed, and adequate space only exists for two 4.0-mm screws in some large cases. The second screw will probably be near the posterior tibial tendon, especially in some small cases.