2017 ISAKOS Biennial Congress ePoster #115

 

Can Ankle Syndesmosis Fixation with a Tricortical Screw or Suture Button Restore Physiologic Tibiofibular Kinematics?

Thomas R. Pfeiffer, MD, Cologne, NRW GERMANY
Conor I. Murphy, MD, Pittsburgh, PA UNITED STATES
Jason P. Zlotnicki, MD, Pittsburgh, PA UNITED STATES
Patrick J. Haggerty, BS, Pittsburgh, PA UNITED STATES
Joseph Russell, BS, College Park, MD UNITED STATES
Richard Debski, PhD, Pittsburgh, PA UNITED STATES
MaCalus V. Hogan, MD, MBA, Pittsburgh, PA UNITED STATES
Volker Musahl, MD, Pittsburgh, PA UNITED STATES

Universiy of Pittsburgh, Pittsburgh, Pensilvania , UNITED STATES

FDA Status Not Applicable

Summary

The suture button only partially restores intact ankle motion after syndesmosis injury. The tricortical screw fixation is able reduce fibular medial-lateral translation, anterior-posterior translation, and external rotation while overconstraint of the tibiofibular joint was not observed.

Abstract

Introduction

Disruption of the Anterior inferior tibiofibular ligament (AITFL), Posterior inferior tibiofibular ligament (PITFL) and Interosseous membrane (IOM) is a predictive measure of residual symptoms after ankle injury. In unstable injuries, the syndesmosis is treated operatively with cortical screw fixation or a suture button apparatus. Biomechanical analyses of suture button versus cortical screw fixation methods show contradicting results regarding suture button integrity and maintenance of syndesmotic fixation. The objective of this study is to quantify tibiofibular joint motion in both fixation models compared to the intact ankle.

Methods

Five fresh-frozen human cadaveric specimens (mean age 58 yrs.; range 38-73 yrs.) were tested using a 6-degree-of-freedom robotic testing system. The tibia and calcaneus was rigidly fixed to the robotic manipulator, while the subtalar joint was fused. The full length of the fibula was maintained and fibular motion was unconstrained. The 3D motion of the fibula with respect to the tibia was tracked by a 3D optical tracking system. A 5Nm external rotation moment and 5Nm inversion moment were applied to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. Outcome variables included fibular medial-lateral (ML) translation, anterior-posterior (AP) translation, and external rotation (ER) in the following conditions: 1) intact ankle, 2) AITFL transected, 3) PITFL and IOM transected, 4) 3.5mm cannulated tricortical screw fixation, and 5) suture button fixation. For statistical analysis an ANOVA with a post-hoc Tukey analysis was performed (*p<0.05).

Results

There were significant differences in AP translation and ER between the suture button and intact ankle. Significant differences in fibular motion were only during the inversion moment. Posterior translation of the fibula was significantly higher with complete syndesmosis injury when compared to the intact ankle at 0°, 15, and 30 plantarflexion and the tricortical screw at 15° and 30°. No significant difference in AP translation exists between the tricortical screw and intact ankle at 15° and 30° plantarflexion. In addition, the suture button demonstrated significantly higher fibular posterior translation compared to the intact ankle at 15° and 30 plantarflexion and compared to the tricortical screw at 15° plantarflexion. ER was significantly increased with full syndesmosis injury compared the intact ankle and tricortical screw at 0° and 30° plantarflexion but only the intact ankle at 10° dorsiflexion. The suture button demonstrated significantly greater ER at 0° plantarflexion and 10° dorsiflexion compared to the intact ankle. The only significant difference in ML translation exists between the tricortical screw and full syndesmosis injury at 30° plantarflexion.

Discussion

The suture button did not restore physiologic motion of the syndesmosis. It only restored fibular ML translation of the fibula while significant differences in AP translation and ER persisted between the suture button and compared to the intact ankle. The tricortical screw restored fibular motion in all planes. No significant differences were observed compared to the between the tricortical screw and intact ankle. These findings are consistent with previous studies. This study utilized a novel setup to measure unconstrained motion in a full length, intact fibula. Physicians should evaluate AP translation and ER as critical fibular motions when reconstructing the syndesmosis with suture button fixation.