|
Year |
2002 |
|---|---|
|
Question Number |
148. |
|
Category |
Foot and Ankle |
Question
With dorsiflexion of the ankle, the fibula will move in which of the following directions?
1- Internal rotation and lateral deviation
2- Internal rotation and medial translation
3- External rotation and medial translation
4- External rotation and distal translation
5- External rotation and proximal translation
Figures
Answer (click for answer)
Preferred Response: 5
With dorsiflexion of the ankle the mortise of the tibiotalar joint must open up in order to accommodate the increased size of the talus. In order to do this the fibula must be externally rotated along with migrating proximally. The literature cited are both anatomical studies designed to discern the function of the fibula during certain phases of gait. The first is a cadaveric study that showed during dorsiflexion there was an increase in both medially and laterally directed forces towards the malleoli. These forces are responsible for the external translation that occurs when the ankle is put into dorsiflexion. The second paper showed that with plantarflexion of the ankle the fibula is pulled distally by the flexors of the foot. This results in a deepening of the ankle mortise and tightening of the interosseus membrane, thereby pulling the fibula medially during the stance and push-off phase of gait. Therefore, during dorsiflexion the relaxation of the foot flexors and the decreased tension through the interosseus membrane, the fibula rotates externally and migrates proximally.
Reference: *Michelson JD, et al. Intra-articular load distribution in the human ankle during motion. Foot & ankle international; 22: 226-233.
*Scranton PF, et al. Dynamic fibular function. Clin Ortho & rel research; 18:76-81.