SLR - September 2022 - Benjamin Bogert, DPM
Reference: Yu T, Zhang Y, Zhou H, Yang Y. Distribution of posterior malleolus fracture lines in ankle fracture of supination-external rotation. Orthop Traumatol Surg Res. 2021 Oct;107(6):103000. doi: 10.1016/j.otsr.2021.103000. Epub 2021 Jun 30. PMID: 34216839.Level of Evidence: 5
Scientific Literature Review
Reviewed By: Benjamin Bogert, DPM
Residency Program: Legacy Health – Portland, OR
Podiatric Relevance: Posterior malleolus fractures are regularly seen in severe Lauge-Hansen supination external rotation (SER) ankle fractures. As SER is the most common mechanism of injury in ankle fractures, surgeons are regularly tasked with the difficult decision whether or not to perform open reduction and internal fixation of the posterior malleolus fracture. The purpose of this study was to provide surgeons with a better understanding of the distribution of fracture lines on the articular surface of the distal tibia in posterior malleolus fractures to aid them in the surgical planning process, specifically when managing an SER ankle fracture.
Methods: Computed tomography (CT) scans of a consecutive series of 70 cases (from January 2012 to March 2017) were included in this study and analyzed retrospectively. Any patient over the age of 18 years old, who sustained an SER ankle fracture and received a preoperative CT scan was included in the present study. Patients with isolated posterior malleolus fractures, open fractures, ankle fractures combined with other injuries, and bilateral fractures were excluded. The CT scans were uploaded to a software for image processing and 3D modeling. Virtual reduction of the fracture was performed and then the posterior malleolus fracture lines were marked. All the individual renderings were then converted into a heat map using a program designed by the authors of this article. A separate software was utilized to measure the articular surface.
Results: The study revealed that most fracture lines start at 20.4% from the tangent of the posterior edge, exiting into the incisura fibularis, and end at 58.7% from the lateral edge into the posterior cortex. Additionally, the study discovered that the posterior malleolus fracture encompassed 14.96% of the total distal tibial articular surface.
Conclusions: The amount of distal tibia articular surface involvement is generally recognized as one of the most important factors that influence surgical decision making, in regard to posterior malleolus fractures. Utilizing the heat maps formulated in this study, the authors discovered that, while some fracture lines move closer or further away from the posterior margin of the distal tibia, the majority of posterior malleolus fractures exist in an arcuate zone close to the posterolateral margin generally involving 15 percent of the total distal tibia articular surface. The authors posited that the heat map introduced in this study could help establish an experimental model for future biomechanics research but would more likely be of benefit in future comparative studies of posterior malleolus fracture lines in other Lauge-Hansen ankle fractures. The 3D rendering of the fracture lines in this study provided better visualization than can be obtained through analysis of a CT scan on the most regularly used imaging software in hospitals, due to the concavity of the distal tibia articular surface. Despite the limitations of this descriptive research design, the aim of this study was achieved to provide surgeons with a better baseline understanding of posterior malleolus fracture lines, specifically regarding those sustained in SER ankle fractures.