Intraoperative Torque Test to Assess Syndesmosis Instability

Area of Science:

• Orthopedic Surgery
• Anatomy
• Biomechanics

Background:

• Ankle syndesmosis injuries require accurate diagnostic tools.
• Assessing tibiofibular diastasis is crucial for diagnosing syndesmotic instability.
• Existing stress tests may lack sensitivity and specificity.

Purpose of the Study:

• To compare the diagnostic accuracy of a novel torque test (TT) against established external rotation stress test (ERT) and lateral stress test (LST) for ankle syndesmosis instability.
• To evaluate the TT's sensitivity and specificity in detecting tibiofibular diastasis following sequential ligamentous injury.

Main Methods:

• A cadaveric study involving 10 fresh-frozen human ankles.
• Sequential sectioning of anteroinferior tibiofibular ligament (AiTFL), interosseous membrane (IOM), and posteroinferior tibiofibular ligament (PiTFL).
• Assessment of tibiofibular diastasis using LST, ERT, and TT under direct visualization at each dissection stage.

Main Results:

• All tested methods showed significant syndesmotic motion after sectioning at least two ligaments.
• The TT yielded the largest mean increase in diastasis (4.8 mm with 2-ligament injury, 6.2 mm with complete injury).
• The TT demonstrated 90% sensitivity and 100% specificity for detecting 2-ligament syndesmotic injury.

Conclusions:

• The torque test (TT) is a more sensitive and specific diagnostic tool for ankle syndesmosis instability compared to LST and ERT.
• Posterolateral fibular stress via the TT generates greater distal tibiofibular diastasis, facilitating intraoperative detection.
• The TT requires less force and offers improved diagnostic capability for syndesmotic injuries.