Columbia Orthopaedic Surgery, New York Presbyterian Hospital, New York, NY.
J Orthop Trauma. 2014 Jun;28(6):e123-7. doi: 10.1097/BOT.0000000000000010.
According to the classification of Lauge-Hansen, supination-external rotation IV (OTA 44-B) injuries should not have syndesmotic instability; yet, several studies have suggested disruption is present in up to 40% of these injuries based on stress tests. In this study, we examine various stress radiographic parameters in a cadaver model of supination-external rotation IV equivalent injury. We hypothesize that external rotation stress testing and widening of the medial clear space do not always represent syndesmotic instability. Rather, the better predictor of syndesmotic instability will be an increased tibia-fibula clear space with the lateral stress test.
Eleven fresh frozen human lower limbs were each secured into a custom frame. External rotation stress test was performed by applying an external moment of 7.5 Nm, and lateral stress test was performed by applying 100 N lateral pull at the distal fibula. True mortise radiographs were taken of intact ankles and while performing external rotation and lateral stress tests at each stage of sequentially sectioning the ankle ligaments. The deltoid ligament was sectioned first, then anterior-inferior tibiofibular ligament, posterior-inferior tibiofibular ligament, and interosseous membrane. Tibiofibular clear space and medial clear space were measured on each radiograph.
External rotation stress test produced significant medial clear space widening when the deltoid ligaments were sectioned (P < 0.05). Lateral stress test produced no significant widening of the tibiofibular clear space until interosseous membranes were sectioned (P < 0.05).
Lateral stress test with widening of the tibiofibular clear space is the preferred indicator of syndesmotic instability. The external rotation stress is a poor indicator of syndesmotic injury in the setting of deltoid ligament injury.
根据劳赫-汉森（Lauge-Hansen）分类，旋后-外旋 IV 度（OTA 44-B）损伤不应有关节内不稳定；然而，几项研究表明，根据压力测试，多达 40%的此类损伤存在破坏。在这项研究中，我们在旋后-外旋 IV 度等效损伤的尸体模型中检查了各种压力放射学参数。我们假设，外旋压力测试和内侧间隙增宽并不总是代表下胫腓联合不稳定。相反，外侧压力测试中胫骨腓骨间隙增大将更好地预测下胫腓联合不稳定。
将 11 个新鲜冷冻的人下肢分别固定在一个定制框架中。通过施加 7.5 Nm 的外部力矩进行外旋压力测试，通过在远端腓骨施加 100 N 的侧向拉力进行侧向压力测试。在完整踝关节和在逐步切断踝关节韧带的每个阶段进行外旋和侧向压力测试时，拍摄真实的跗骨正位片。首先切断三角韧带，然后切断前下胫腓韧带、后下胫腓韧带和骨间膜。在每张 X 光片上测量胫腓骨间隙和内侧间隙。
当三角韧带被切断时，外旋压力测试导致明显的内侧间隙增宽（P < 0.05）。直到骨间膜被切断，侧向压力测试才导致胫腓骨间隙明显增宽（P < 0.05）。
伴有胫腓骨间隙增宽的侧向压力测试是下胫腓联合不稳定的首选指标。在三角韧带损伤的情况下，外旋压力测试是下胫腓联合损伤的一个较差指标。
