SLR - September 2014 - Alexander R. Pérez

Preoperative Radiographic and CT Findings Predicting Syndesmotic Injuries in Supination-External Rotation-Type Ankle Fractures

Reference: Young, Choi MD; Soon-Sun Kwon, PhD; Chin Youb Chung, MD, PhD; Moon Seok Park, MD, PhD; Seong Yeol Lee, MD; Kyoung Min Lee, MD. Preoperative Radiographic and CT Findings Predicting Syndesmotic Injuries in Supination-External Rotation-Type Ankle Fractures. J Bone Joint Surg Am, 2014 Jul 16;(96)14:1161-1167.

Scientific Literature Review

Reviewed By: Alexander R. Pérez, DPM
Residency Program: Englewood Hospital and Medical Center

Podiatric Relevance: The standard of care in evaluating syndesmotic injuries in the presence of ankle fractures is the intraoperative stress test. Given the intraoperative necessity of the test and its inherent subjectivity, an objective preoperative evaluation is needed. This study sought to identify the factors leading to syndesmotic injury. The authors hypothesized that fibular bone mineral density, determined by attenuation seen on CT, fibular fracture height from ankle joint line, and concurrent deltoid ligament injuries would contribute to syndesmotic injuries.

Methods: This retrospective Level II study consisted of 191 patients with SER-type ankle fracture (as per the Lauge-Hansen Classification system) who had undergone operative treatment. Preoperative ankle radiographs and CT imaging were obtained for all patients. After demographic stratification, patients were further divided into two groups – a stable syndesmotic group and an unstable syndesmotic group. Positive lateral stress test was confirmed for all patients intraoperatively. On CT, fracture height, fracture length, medial joint space, extent of fractures and osseous attenuation were evaluated. On plain radiographs, fracture height and medial joint space were evaluated. Binary logistic regression analysis was performed in order to determine which factors were statistically significant contributors in unstable syndesmotic injuries in SER-type ankle fractures.

Results: Patient mean age at time of surgery was 50.7 ± 16.4 years. There were 104 male and 87 female patients included in the study. Of this cohort, 38 (19.9 percent) patients had a syndesmotic injury that underwent syndesmotic fixation and open reduction with internal fixation. Statistically significant contributing factors to formation of unstable syndesmotic injuries in SER-type injuries were observed on CT imaging for all of the following: unstable and stable syndesmotic groups, age, sex, the proportion of high-energy trauma, fracture height on CT, medial joint space on CT, and bone attenuation of the medial and lateral malleoli. Differences in fracture height and medial joint space were also statistically significant on plain radiographs. Cutoff factors for predicting unstable syndesmotic injuries in SER-type fractures were as follows: a fracture height of > 3mm on CT, a medial joint space of > 4.9mm on CT, a fracture height of > 7mm on radiographs and a medial joint space of > 4.5 mm on radiographs.

Conclusions: In considering whether syndesmotic fixation is needed for SER-type ankle fractures, the authors concluded that fracture height, medial joint space and bone attenuation on CT imaging and plain radiograph were the significant preoperative factors to take into account. In addition the authors noted that compared with the stable syndesmotic group, the unstable syndesmotic group had a propensity toward young male patients injured by a high-energy trauma. Consequently, when evaluating SER-type ankle injuries the authors recommend evaluating for syndesmotic injury in young male patients with high-energy trauma, especially when the lateral malleolar fracture line begins > 7mm proximal to the ankle joint line or the medial joint space is > 4.5mm wide on radiographs.

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