Imaging Threshold for Assessment of the Correct Reduction in the Treatment of Unstable Syndesmotic Injuries - A Retrospective Analysis of 57 CT Scans

Introduction: An incongruence of the distal tibiofibular joint (TFJ) after treatment of upper ankle joint injury represents a prearthrotic deformity and must be corrected. The objectives of this study were to analyze postoperative CT scans after surgical treatment of unstable syndesmotic injuries, and to determine the prevalence of syndesmotic malreduction and its contributing factors. The specific parameters of three-dimensional imaging for objective detection of malreduction should be identified as a helpful intraoperative imaging threshold. Materials and Methods: Postoperative CT scans of 57 patients were analyzed by identifying cases requiring correction. Factors that influenced the reduction result (patient age, sex, fracture type and surgeon qualifications) were evaluated. The following CT measurements were determined: anterior ( AD) and posterior tibiofibular distance (PD), TFJ width, anteroposterior fibular translation (APT), length and rotation of the fibula, position of the malleoli to the talar joint surface. A confidence interval of 95% was assumed (significance level p < 0.05). Results: A very high proportion of the cases required revision (38.5%). Age (p=0.199), sex (p=0.752), body mass (p=0.722), and fracture type (p=0.266) had no significant influence on the reduction result. The risk of requiring correction was slightly lower for well-experienced trauma surgeons. The measurements revealed the following thresholds: AD: circle divide 3.2 mm (+/- 2.2), PD: circle divide 5.1 mm (+/- 2.2), TFJ: circle divide 3.4 mm (+/- 1.4), APT: circle divide 7.9 mm (+/- 3.5), and rotation: circle divide 10.7 degrees (+/- 6.8). The fibula was too long in 4 cases (7%) and too short in 8 cases (14%). There was a malleolar incongruence in 5 cases (8.7%). The analysis revealed a significant correlation between the ratio of the anterior and posterior tibiofibular distances and a need for correction. Conclusion: The ratio between the anterior and posterior tibiofibular distances in the axial sectional image is an aid for intraoperative assessment of the correct reduction in the TFJ.