Use of bony landmarks for more accurate tibiofibular syndesmotic fixation: Validity and safety analysis of the angle bisector method.

BACKGROUND AND AIMS: The Angle Bisector Method uses the cortices of the tibia and fibula as reference points and suggests a syndesmotic fixation trajectory through the bisector of the angle formed by two lines tangent to the anterior and posterior aspects of the tibia and fibula. This study aimed to assess whether the Angle Bisector Method can provide a patient- and level-specific syndesmotic fixation angle that is reproducible, safe, and independent of the surgeon in a cadaveric setting.

METHODS

Twelve matched above-knee leg specimens from six cadavers, underwent syndesmotic fixation (using either screws or suture-buttons) at two levels-2 cm and 3.5 cm proximal to the tibial plafond. The fixations were carried out using the angle bisector method by two surgeons employing an open lateral approach. Subsequently, CT images of the cadavers were obtained. The angle between the true centroidal axis and the axis of the syndesmotic implant trajectory was measured using radiological software. Additionally, distances between fibular entry points of the centroidal axis and the implant trajectory were measured. Distances between the positioned K-wires and major neurovascular structures were measured on cadaver dissections, and any resultant damage was documented.

RESULTS

The average angle between the centroidal axis and screw trajectory was 2.7 ± 2.9 degrees at the 2 cm level and 1.8 ± 2.5 degrees at the 3.5 cm level. The average distance between the fibular entry points of the centroidal axis and the screw was 1.7 ± 1.2 mm at the 2 cm level and 1.2 ± 1.0 mm at the 3.5 cm level. The results demonstrated low inter-surgeon variability and high intra- and inter-observer reliability (ICC>0.80). The distance between the placed K-wires and major neurovascular structures was always higher than 5 mm, affirming the safety of the technique.

CONCLUSION

Our data suggests that the angle bisector method can provide a reliable trajectory for syndesmotic fixation and may be safely used in surgical procedures. This approach can be applied with K-wires or a specially designed jig to facilitate syndesmotic fixation.