SLR - January 2022 - Amar Chandra

Predicting Syndesmotic Injury in OTA/AO 44-B2.1 (Danis-Weber B) Fractures

Reference: Kellam PJ, Dekeyser GJ, Haller JM, Rothberg DL, Higgins TF, Marchand LS. Predicting Syndesmotic Injury in OTA/AO 44-B2.1 (Danis-Weber B) Fractures. J Orthop Trauma. 2021 Sep 1;35(9):473-478.

Level of Evidence: Prognostic Level III

Scientific Literature Review

Reviewed By: Amar Chandra, DPM
Residency Program: Grant Medical Center – Columbus, Ohio

Podiatric Relevance: Syndesmotic injuries are commonly seen with rotational-type ankle fractures but can be difficult to predict outside the operating room. While descriptive classifications are commonly utilized for these fractures, they fail to provide prognostic value and accurate assessment of the syndesmosis. As such, standard pre-operative radiographs may provide insight into the prevalence of syndesmotic injuries based on the level and extent of the fracture line. This study aimed to determine whether pre-operative radiographs could accurately predict injuries to the syndesmosis in Weber-B-type fractures. The authors hypothesized that the distal extent of the proximal fragment could predict syndesmotic injury, and that superior extensions would have a higher risk of injury than fractures extending more inferiorly.

Methods: Two hundred eighty-seven patients met the inclusion criteria and were retrospectively reviewed over a ten-year period. This included skeletally mature individuals with OTA/AO 44-B2.1 fractures only. Standard ankle Anterior-posterior (AP) and mortise views were used to determine the distal extent of the proximal fracture fragment. The distal extent was classified into one of three zones based on distal tibial landmarks: Zone 1 was distal to the plafond, Zone 2 was located between the plafond and physeal scar, and Zone 3 was proximal to the physeal scar but within the incisura. Fracture height (FH), medial clear space, and AP physeal scar measurements were taken using AP and mortise views. On lateral views, the lateral physeal scar (LPS), fracture displacement, and fracture length were measured. Intra-operatively, external rotational stress testing was performed after fibular stabilization with syndesmotic fixation being applied if indicated. Inter- and intraobserver reliability was measured by two reviewers.

Results: A total of one hundred ninety-one patients demonstrated fractures in zone 1, fifty-seven in zone 2, and thirty-nine in zone 3 with syndesmotic fixation needed in 17 percent, 42 percent, and 74 percent of cases, respectively. The risk of syndesmotic injury between different zones was found to be significant: 2.44 between zones 1 and 2 (P<0.001), 1.77 between zones 2 and 3 (P=0.0017), and 4.3 between zones 1 and 3 (P<0.001). Medial clear space ratio and zone of distal extent were the only two factors to demonstrate correlation with syndesmotic instability following binary logistic regression. Both inter- and intraobserver reliability were found to be good to excellent.

Conclusions: The authors in this study were able to demonstrate significant correlations with the distal extent of the proximal fibular fracture and the rate of syndesmotic injury. Fractures ending within the zone of the physeal scar (zone 2) were 2.44 times more likely to have syndesmotic injuries compared to those ending distal to the plafond (zone 1). Furthermore, zone 3 fractures demonstrated a syndesmotic injury rate of 74 percent compared to 42 percent for zone 2 and 17 percent for zone 1. While other studies evaluating Weber B fractures have demonstrated similar results, the current one provides a method by which physicians can easily and accurately predict syndesmotic injuries based off pre-operative radiographs. This information could play an important role when discussing treatment options during the pre-operative period and aid the surgeon in operative planning. 

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