Stress vs. Non-Stress Radiographs in Subtle Syndesmotic Injuries

Abstract

Category: Sports Introduction/Purpose: Between 1-18% of all ankle sprains and 23% of all ankle fractures involve injury to the distal tibio-fibular syndesmosis. Syndesmotic injuries can create a substantial diagnostic and therapeutic challenge for orthopaedic surgeons. While acute injuries can be assessed using conventional radiographs, subtle syndesmotic injuries may be misdiagnosed using X-rays. Misdiagnoses may result in chronic ankle instability, pain and post-traumatic osteoarthritis of the tibio-talar joint. The purpose of this study was to investigate whether syndesmotic injury was more easily diagnosed with stress vs. non-stress radiographs.radiographs.sed with stress vs. non-stress radiographs. Methods: Five pairs of cadavers (tibia plateau to toe-tip, mean 61 years, range 52-70 years) were scanned with weight-bearing CT (170 lb, w/ and w/o 10 Nm static external rotation torque). Digitally reconstructed radiographs (DRRs), which are comparable to conventional radiographs, were reconstructed from the 3D CT data. The following conditions were tested: First, intact ankles (Native) were tested. Second, one specimen from each pair underwent AITFL resection, while the contralateral underwent deltoid resection (Condition 1). Third, the remaining intact deltoid ligament or AITFL was resected in each ankle (Condition 2). Finally, the interosseous membrane (IOM) was resected in all ankles (Condition 3). Condition 3 was defined as acute syndesmotic injury. Using antero-posterior (AP) views, the tibio-fibular clear space (TFCS), tibiofibular overlap (TFO) and medial clear space (MCS) were assessed. Statistical analysis was performed using paired (comparison within groups) and unpaired (comparison between groups) t-test where p=0.05 was considered significant. Results: Regarding the TFCS, Native vs. Condition 3 in 10 Nm stress radiographs was significantly different in the deltoid group (p=0.021). Using TFO in stress and non-stressed radiographs, Native vs. Condition 2 and 3 was significantly different for the deltoid group (p=0.043), and Native vs. Condition 3 in the syndesmotic group (p=0.027). Regarding the MCS in non-stress radiographs, Native vs. Condition 3 was significantly different in the deltoid group (p=0.007), while in stress views, Native vs. Condition 2 was significant different in the syndesmotic (p=0.026) and Native vs. Condition 3 in the deltoid group (p=0.030). No differences were found comparing the conditions of the AITFL with the same conditions of the deltoid group. Conclusion: The TFCS cannot be used to assess subtle or acute syndesmotic injuries in stress and non-stress radiographs. The TFO can be used to assess a combined injury to the AITFL and deltoid ligament in stress and non-stress radiographs. The MCS can be used to assess acute syndesmotic injuries in stress and non-stress radiographs. Radiographs (stress or non-stress) cannot be used to distinguish between injuries to the AITFL or deltoid ligament. Therefore, stress and non-stress radiographs are not useful in assessment of subtle syndesmotic injuries. Stress-radiographs are not superior compared to non-stress radiographs in assessment of acute syndesmotic injuries.