Simulating clamp placement across the trans-syndesmotic angle of the ankle to minimize malreduction: A radiological study

Abstract

Background Ankle fractures associated with syndesmotic injury have a poorer prognosis than those without such an injury. Anatomic reduction of the distal tibiofibular joint restores joint congruency and minimizes contact pressures, yet operative fixation of syndesmotic ankle injuries is frequently complicated by malreduction of the syndesmosis. Current methods of assessing reduction have been shown to be inadequate. As such, additional methods to judge the accuracy of syndesmotic reduction are required. Questions/Purposes The purposes of our study were (1) to determine the anatomic axis of the syndesmosis, or the trans-syndesmotic angle (TSA), and (2) to describe the intraoperative fluoroscopic appearance of syndesmotic clamp reduction oriented along the anatomic syndesmotic angle. Methods Computed tomography (CT) scans of 45 uninjured adult ankles were analyzed to measure the TSA, defined as the angle between the plane of a lateral ankle radiograph and a line drawn perpendicular to the fibular incisura. Three-dimensional reconstructions of CT scans were then used to demonstrate clamp placement collinear with the TSA as would be seen on an intraoperative lateral ankle radiograph. Results The average TSA measured 21±5 degrees anterior to the plane of a lateral radiograph. When a simulated reduction clamp tine was placed on the fibular ridge and the clamp oriented along the TSA, the medial tine, as seen on a lateral radiograph, was within the anterior one-third of the tibia 93% of the time. It was, on average, 23±7% of the distance from the anterior to the posterior tibial cortex, with tine placement occurring in this range in 73% of ankles. The medial tine rested 53±17% of the distance between the anterior cortices of the tibia and fibula, with 71% of tines placed in this range. Conclusions Reduction clamp placement oriented along the TSA has a predictable appearance on lateral ankle imaging and can guide clamp positioning during syndesmotic reduction. With one tine placed on the fibular ridge, placing the medial clamp tine in the anterior third of the tibia, or halfway between the anterior cortices of the tibia and fibula is the most accurate position for reduction in line with the TSA. Level of Evidence 2 (Retrospective diagnostic)

Getting the Starting Point Right: Prevention of Skiving and Fibular Cortical Breach During Suture Button Placement for Syndesmotic Ankle Injuries

“…8,30 Malreduction of the fibula within the incisura has been shown to occur with eccentric clamp placement or syndesmotic fixation that deviates from the trans-syndesmotic axis (TSA). 28,[31][32][33][34] Although this technical tip focuses on decreasing the chances of eccentric drilling during SB fixation, it may also achieve a secondary purpose of reducing the incidence of syndesmotic malreduction when placing a SB through a limited incision. The above-mentioned technique centers the starting point on the lateral distal fibula, which has been shown to increase the chance of accurate syndesmotic reduction in biomechanical studies.…”

“…The above-mentioned technique centers the starting point on the lateral distal fibula, which has been shown to increase the chance of accurate syndesmotic reduction in biomechanical studies. 31,33,34 Without this technique, it may be challenging to orient the drill to match the TSA of 21° ± 5° to achieve an accurate syndesmotic reduction without risking skiving off the fibula and cortical breach. 34 In conclusion, accurate SB placement through a limited exposure can be challenging because of drill size along with distal fibular diameter and morphology.…”

“…31,33,34 Without this technique, it may be challenging to orient the drill to match the TSA of 21° ± 5° to achieve an accurate syndesmotic reduction without risking skiving off the fibula and cortical breach. 34 In conclusion, accurate SB placement through a limited exposure can be challenging because of drill size along with distal fibular diameter and morphology. 26 The surgical technique described is a safe and simple way to mitigate the risk of breaching the anterior or posterior fibular cortex and to ensure an adequate starting position.…”

A Novel Indirect Reduction Technique in Ankle Syndesmotic Injuries: A Cadaveric Study

“…In this series, the average TSA angle and the resulting medial clamp tine position along the tibial line were similar to a previous study using CT imaging software to simulate clamp tine placement. 27…”

“…At a level 1cm above the tibial plafond, the TSA angle, defined on the axial CT as the angle between the plane of the a true talar-dome lateral and a line perpendicular to the tangent of the anterior and poster borders of the fibular incisura, was recorded as previously described (Figure 2-C). 27 The apex of the TSA was then positioned on the lateral fibular ridge and extended towards the medial tibial cortex, simulating the positions of the lateral and medial clamp tines, respectively. The projected location of the medial clamp tine along the TSA was then recorded as a percentage of the distance from the anterior tibial cortex along the “tibial line”, defined as the distance between the anterior to posterior cortices of the tibia.…”