Anatomy of the tibial incisura as a risk factor for syndesmotic injury
Introduction
The tibiofibular syndesmosis serves as a dynamic link between the distal tibia and fibula thus contributing to the integrity of the ankle mortise. The distal fibula is engaged into the tibial incisura. This connection is reinforced by a complex system of ligaments [1]. Syndesmosis injuries continue to receive wide attention in recent years as anatomic reduction of the distal fibula into the tibial incisura is an important prognostic factor in ankle fractures with relatively high rates of malreduction reported [2].
The bony anatomy of the tibiofibular syndesmosis has also been an area of interest. Several studies have analyzed the radiologic features of the syndesmosis in the normal population. These included measurements of groove depth, width, distances from the anterior and posterior tubercles to the fibular margins and many other linear parameters [3], [4], [5], [6], [7]. Höcker and Pachucki, in 1989, observed that the fibular incisura has a rotational variability [8]. Numerous studies analyzed the quality of syndesmosis reductions [9], [10], [11], [12]. The features of the radiographic syndesmosis anatomy in patients with syndesmotic injury have not yet been studied.
The aim of this study was to compare the anatomy of the syndesmosis in patients who sustained a high fibular fracture with syndesmosis disruption to that of the non-injured control population. We hypothesized that the anatomy of the syndesmosis in patients who sustained syndesmotic disruption would differ from the anatomy of the noninjured group. In other words, we believed that there are certain anatomical features making the syndesmosis more susceptible to ligamentous injury (“syndesmotic dysplasia”).
This situation would be analogous to femoral groove dysplasia leading to an elevated risk of patellar instability [13]. In knee surgery it is well understood, that certain anatomical features of the femoral condyles make the patella more prone to dislocation [14]. Patients with these anatomical features are overrepresented among patients with patellar dislocation. If “syndesmotic dysplasia” exists, patients with dysplastic syndesmoses would be overrepresented in the syndesmotic disruption group.
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Material and methods
The study population consisted of two groups of 75 patients each with a complete set of bilateral CT scans of their ankles that were identified retrospectively over a period of five years. The CT examination was performed with the patient supine with a multi-detector scanner (General Electric). Both feet were placed with the ankle in neutral position and parallel to each other in a holding device. The parameters for image acquisition were as follows: section collimation 0.75 mm, section
Reliability
For the noninjured group A Cronbach’s alpha for intra-rater reliability was 0.97, 0.92, and 0.94 for depth, engagement and angular measurement and 0.93, 0.93, and 0.96 for inter-rater reliability, respectively. For the injured group B Cronbach’s alpha for intra-rater reliability was 0.95, 0.96 and 0.94 for depth, engagement and angular measurement and 0.97, 0.97 and 0.93 for inter-rater reliability respectively. These numbers are consistent with excellent reliability for each measurement.
The
Discussion
The tibiofibular syndesmosis is crucial for maintaining ankle stability while providing a dynamic support between the distal tibia and fibula. The fibula is engaged into its incisura within the distal tibia [1]. Wide variations in the bony and ligamentous anatomy of the syndesmosis have been reported [4], [8], [21], [22]. These features have attracted renewed interest in recent years with wider use of CT scanning and understanding the prognostic relevance of syndesmosis injuries in the wake of
Conclusions
Patients with syndesmoses that are shallow, disengaged, and/or retroverted are overrepresented among patients with a high, suprasyndesmal fibular fracture. These bony anatomical features seem to be predisposing to syndesmotic disruption. Studies dealing with syndesmosis reduction should take into account that the anatomy of the tibial incisura in patients with syndesmotic disruption may not be representative for the whole population.
Funding
The work was supported by Centre of Postgraduate Medical Education. Grant no 501-1-07-18-16.
Ethical approval
Ethical approval was granted on 08.06.2016 by Ethic Committee of Centre of Postgraduate Medical Education.
Conflicts of interest
Andrzej Boszczyk, Sławomir Kwapisz, Martin Krümmel, Rene Grass have nothing to declare.
Stefan Rammelt is receiving non-financial support from AO Trauma (Travel/Housing for AO Meetings, Courses as Member of the Foot & Ankle Expert Group) not directly related to this work.
Acknowledgement
The authors wish to thank Agata Boszczyk, BEng, MSc in Architecture, for help in preparing the illustrations.
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