Abstract
Purpose
The anterior inferior tibiofibular ligament (AiTFL) is the primary lateral ligamentous stabilizer of the ankle syndesmosis. Current syndesmosis repair techniques traverse the tibia and fibula, but do not anatomically reconstruct the AiTFL. We compared a novel AiTFL anatomic repair technique (ART) to rigid syndesmosis screw fixation (SCREW).
Method
Twelve cadaveric below knee specimens were compared radiographically and using a biomechanical testing protocol. All specimens underwent a CT scan of the ankle joint prior to testing. Next, the AiTFL, interosseous membrane and deltoid ligament were sectioned, and the posterior malleolus osteotomized, to recreate a trimalleolar-equivalent ankle fracture. The posterior malleolus was repaired with the posterior ligamentous insertions intact and functional (PMALL). Ankles were examined under fluoroscopy with an external rotation stress exam and the medial clear space (MCS) measured. Specimens were then randomized to receive either a conventional syndesmosis screw (SCREW), or the novel anatomic repair technique (ART). External rotation stress fluoroscopy was repeated. A second CT was completed and the fibular position compared to the pre-injury CT. Each specimen was then loaded in external rotation until failure using a custom biomechanical jig.
Results
The MCS during stress examination increased by 1.04 0.31mm in the PMALL group. MCS increased significantly less at only 0.300.07mm (p=0.002) in the ART group. The SCREW fixation method demonstrated a delta MCS of 0.280.16mm (p=0.008). Post repair CT showed that 33% of specimens were subluxed from the SCREW group compared to 0% for the ART. Mean torque at failure for ART was 24.85.5Nm compared to 16.85.8Nm for SCREW (p=0.01).
Conclusion
Repair of the posterior malleolus alone demonstrated a greater than 1mm of medial clear space widening and is not sufficient to re-establish syndesmotic stability. Addition of the ART or SCREW technique restored syndesmotic stability. None of the ART specimens demonstrated fibular subluxation, while 33% of SCREW specimens were subluxed anteriorly on CT. Biomechanical strength of the ART was found to be greater than that of rigid screw fixation.
