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

Abstract

Objective: To describe a novel technique using preoperative computed tomography (CT) to plan clamp tine placement along the trans-syndesmotic axis (TSA). We hypothesized that preoperative CT imaging provides a reliable template on which to plan optimal clamp tine positioning along the TSA, reducing malreduction rates compared with other described techniques.

Methods: CT images of 48 cadaveric through-knee specimens were obtained, and the TSA was measured as well as the optimal position of the medial clamp tine. The syndesmosis was then fully destabilized. Indirect clamp reductions were performed with the medial clamp tine placed at positions 10 degrees anterior to the TSA, along the TSA, and at both 10 and 20 degrees posterior to the TSA. The specimens were then separately reduced using manual digital pressure and palpation alone. CT was performed after each clamp and manual reduction.

Results: On average, reduction clamp tines were within 3 ± 2 degrees of the desired angle and within 5% ± 4% of the templated location along the tibial line for all clamp reduction attempts. Palpation and direct visualization produced the overall lowest malreduction rates in all measurements: 4.9% and 3.0%, respectively. Off-axis clamping 10 degrees anterior or 20 degrees posterior to the patient-specific TSA demonstrated an increased overall malreduction rate: 15.8% and 11.3%, respectively. Significantly more over-compression occurred when a reduction clamp was used versus manual digital reduction alone (8.6% vs. 0%).

Conclusions: Reduction clamp placement directly along an optimal clamping vector can be facilitated by preoperative CT measurements of the uninjured ankle. However, even in this setting, the use of reduction clamps increases the risk for syndesmotic malreduction and over-compression compared with manual digital reduction or direct visualization.

Figure 1

Axial CT view of an intact syndesmosis 1cm above the tibial plafond with measurements (A-G) of fibular position relative to the incisura as originally described by Nault et al.

Figure 2

A. Adjustment of axial CT at the level of the talus such that the localizer line runs tangential to the talar dome. Correction in this plane is equivalent to internal or external rotatory adjustments when obtaining a true talar dome lateral using fluoroscopy. B. Adjustment of coronal CT images such that the localizer line runs tangential to the superior talar dome. Correction in this plane is equivalent to abducting or adducting the lower extremity in the plane of the fluoroscopy machine to eliminate the projection of talar dome double densities. C. Blue dotted lines: Anterior and Posterior cortices as visualized in the lateral projection. Red line: The trans-syndesmotic axis (TSA) which runs perpendicular to a line (white) that is tangential to both the anterior and posterior borders of the incisura. Yellow dot: Templated position of the medial clamp tine Green dot: Templated position of the lateral clamp tine D. True talar dome lateral image with the corresponding location of the yellow dot representing the templated position of the medial clamp tine along the TSA.

Figure 3

Overall malreduction rates versus clamp positioning relative to the TSA angle. The highest malreduction rates occurred when the medial clamp tine was placed 10 degrees anterior, or 20 degrees posterior to the TSA. Lowest malreduction rates were seen in the palpation and direct visualization techniques.