Screw fixation for syndesmotic injury is stronger and provides more contact area of the joint surface than TightRope®: A biomechanical study.

BACKGROUND

The rupture of syndesmotic ligaments is treated with a screw fixation as the gold standard. An alternative is the stabilization with a TightRope®. A couple of studies investigated the different clinical outcome and some even looked at the stability in the joint, but none of them examined the occurring pressure after fixation.

OBJECTIVE

Is there a difference in pressure inside the distal tibiofibular joint between a screw fixation and a TightRope®? Does the contact area differ in these two treatment options?

METHODS

This biomechanical study aimed to investigate the differences in fixation of the injured syndesmotic ligaments by using a fixation with one quadricortical screw versus singular TightRope® both implanted 1 cm above the joint. By using 12 adult lower leg cadaveric specimens and pressure recording sensor, we recorded the pressure across the distal tibiofibular joint. Additionally we measured the contact surface area across the joint.

RESULTS

The mean of the pressure across the distal tibiofibular joint from the start of the insertion of the fixation device to the complete fixation was 0.05 Pascal for the TightRope® and 0.1 for the screw (P= 0.016). The mean of the maximum pressure across the joint (after completion of fixation and releasing the reduction clamp) was 1.750 mega Pascal with the screw fixation and 0.540 mega Pascal with TightRope® (P= 0.008). The mean of the measured contact area of the distal tibiofibular joint after fixation was 250 mm2 in the TightRope® group and of 355 mm2 in the screw fixation (P= 0.123).

CONCLUSIONS

The screw fixation is stronger and provides a larger surface contact area, which leads us to the conclusion that it provides a better stability in the joint. While previous clinical studies did not show significant clinical difference between the two methods of fixation, the biomechanical construct varied. Long term clinical studies are required to establish whether this biomechanical distinction will contribute to various clinical outcomes.