Physiologic Motion in the Intact and Unstable Syndesmosis During Plantigrade Weightbearing in Controlled Ankle Motion Boots

Abstract

Consensus has not been reached for the optimal postoperative care after high ankle sprain and syndesmotic fixation. A potential drawback of earlier return to activity is greater instability of the ankle and fixation failure. The controlled ankle motion (CAM) boot has been an effective implementation to stabilize the leg and may aid in safe early weight-bearing status. However, there is insufficient study of its effect on motion in the syndesmosis following injury. Hence, the aim of this cadaveric study was to determine the stability of the ankle with a CAM boot at three levels of injury: syndesmosis ligaments intact (no injury), syndesmosis ligaments cut, and syndesmosis and fibula cut. Six cadaveric legs were subjected to each level of injury and axially loaded at 1Hz between 100N - 1.5 times body weight for 50 seconds, and axial force, axial displacement, and optical tracking data were recorded. It was found that the ankle, when protected by the CAM boot, maintained syndesmosis motion with no difference (p>0.05) from the uninjured state, regardless of syndesmotic ligament and fibular injury. This finding was consistent across anterior-posterior, medial-lateral, and superior-inferior axes. Overall, our study may suggest that early weight-bearing with a CAM boot maintains a physiologically range of motion in the syndesmosis.