Bilateral External Rotation Torque CT Remains Reliable in Syndesmotic Assessment Despite Lateral Ligament Injury, but...

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomechanics

Background:

• Accurate diagnosis of syndesmotic injuries requires understanding their relationship with lateral ligament disruptions.
• The impact of concurrent lateral ligament lesions on syndesmotic instability assessment using bilateral external torque computed tomography (BET-CT) is not well-established.
• Existing literature primarily focuses on deltoid ligament injury's influence on BET-CT syndesmotic evaluation.

Purpose of the Study:

• To determine if lateral ligament lesions influence syndesmosis instability measurements in BET-CT.
• To investigate whether combined lateral ligament and syndesmotic injuries cause a quantifiable increase in tibiotalar instability.
• To assess the reliability of BET-CT for syndesmotic evaluation in the presence of lateral ligament injuries.

Main Methods:

• Seven cadaveric lower limb pairs underwent sequential lateral ligament sectioning (ATFL, CFL, PTFL) after iatrogenic syndesmotic transection.
• BET-CT imaging was performed under varying external rotation torques (0-7.5 Nm).
• Measurements included anterior/posterior tibiofibular distances, tibiofibular clear space, and medial/lateral tibiotalar gutter angles.

Main Results:

• Anterior tibiofibular distance remained stable despite ligament dissection and increased torque.
• Tibiofibular clear space and posterior distance showed no significant or consistent changes.
• The medial tibiotalar gutter angle significantly increased with complete lateral complex disruption (22.9° to 27.6°).

Conclusions:

• BET-CT reliably assesses syndesmotic widening, unaffected by concurrent lateral ligament injuries.
• Disruption of the lateral ligament complex significantly exacerbates rotational tibiotalar instability.
• Combined ankle ligament injuries require comprehensive evaluation, with clinical validation pending.