The Contralateral Ankle Joint Is a Reliable Reference for Testing Syndesmotic Stability Using Bilateral External...

Area of Science:

• Orthopedic biomechanics
• Radiographic imaging analysis
• Ankle joint diagnostics

Background:

• Subtle chronic or latent ankle instabilities are challenging to diagnose with current methods.
• Ligamentous functionality assessment is limited in diagnosing syndesmotic lesions.
• A bilateral external torque computed tomography (CT) method showed promise in cadaveric studies for detecting syndesmotic lesions.

Purpose of the Study:

• To evaluate the efficacy of an external torque device in assessing syndesmotic stability in healthy young adults.
• To compare measurements between contralateral ankle joints under varying torque levels.
• To establish baseline data for identifying potential syndesmotic instability.

Main Methods:

• Ten healthy subjects underwent four CT scans with an external torque device applying 0, 2.5, 5, and 7.5 Nm of external rotation.
• Radiographic measures including anterior distance (AD), tibiofibular clear space (TCS), posterior distance (PD), external rotation (ER), and β angle were analyzed.
• Measurements were compared between the left and right ankle joints for each subject.

Main Results:

• Increasing external torque led to slight increases in AD, ER, and β angle, and slight decreases in TCS and PD.
• Significant inter-subject variability was observed for all parameters.
• Intra-individual side differences were minimal, with the smallest difference observed in AD (max 0.5 mm).

Conclusions:

• The contralateral healthy ankle serves as a reliable reference for assessing syndesmotic stability using the external torque device.
• Side differences exceeding 0.5 mm in AD or 0.9 mm in PD may indicate significant syndesmotic instability.
• Further research is required to establish definitive cutoff values for diagnosing acute and chronic syndesmotic instability.