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.