Augmented Stress Weight-Bearing CT for Evaluation of Subtle Tibiofemoral Syndesmotic Injuries in the Elite Athlete

Abstract

Category: Ankle; Sports; Trauma Introduction/Purpose: Tibiofibular syndesmotic injuries occur in association with fractures or in isolation, often referred to as 'high ankle sprains'. Dynamic instability of the syndesmosis in the high-level athlete is difficult to diagnose, requiring a high index of suspicion for the identification and surgical stabilization to prevent late adverse sequelae, such as recurrent ankle pain, anterolateral soft tissue impingement, local synovitis, and chronic instability of distal syndesmosis. Both CT and MRI have been helpful in identifying syndesmotic injuries, but are static, non-weight bearing imaging modalities that cannot demonstrate dynamic instability, which may miss the unstable nature of some injuries. We present a novel imaging technique utilizing weight-bearing CT with syndesmotic stress in which a case is presented to illustrate it's utility in the elite athlete. Methods: Cone beam weight bearing computed tomography (WBCT) is a well-described imaging modality for evaluation of foot and ankle injuries. We have found it highly beneficial to teach our CT technologists about syndesmosis injuries and the importance of augmented physiologic stress applied across the ankle joint (in addition to the standard WBCT) to better demonstrate instability or motion, particularly at the tibiofibular syndesmosis. To perform an augmented stress weight bearing CT, the patient is positioned in the WBCT scanner and initial images are acquired in the standing weight bearing position with feet directed forward and weight distributed equally. A second image acquisition is then performed (augmented stress), where the patient is coached to firmly plant both feet on the ground and internally rotate the shin and knee. This places an external rotational moment on the TFS due to the planted foot and ankle. Results: Our case is of a 21-year-old male collegiate football player, wide receiver, that sustained an eversion injury to his left ankle during game play. He subsequently was unable to bear weight, with pain anteriorly over the distal tibiofibular joint. Pain was reproduced with dorsiflexion and eversion stress; however, he had a negative 'squeeze test' on examination. Initial weight bearing radiographs were negative. An MRI was obtained which did not reveal evidence of syndesmotic injury. Subsequently, weight- bearing CT stress examination of the syndesmosis was obtained and found to have 8 mm widening of the tibiofibular syndesmosis, 4 mm increased when compared to his contralateral, uninjured, ankle. This was also compared with a neutral WBCT without stress that did not illustrate the unstable nature of the injury. The coronal images also demonstrate increased uncovering of the talus underneath the tibial plafond. Conclusion: Tibiofibular syndesmotic injuries have historically been detected with standard x-ray, stress plain films, standard CT, and MRI. In cases where injury and stability are not obvious by these diagnostic studies, more subtle injuries may be frequently missed leading to increased morbidity, chronic instability, and increased return to play times. The addition of a stress view on weight-bearing CT can allow further identification of instability of the syndesmosis. We propose this technique for diagnosing otherwise unrecognized, subtle dynamically unstable syndesmosis injuries where clinical suspicion persists despite negative imaging, particularly in the elite athlete.