Normal Contralateral Variation of the Lisfranc Complex and Diagnostic Cutoffs for Subtle Instability Using 3D...

Area of Science:

• Orthopedics
• Radiology
• Biomechanics

Background:

• Weightbearing computed tomography (WBCT) allows dynamic foot evaluation by comparing injured and uninjured limbs under physiologic load.
• Understanding normal 3D WBCT variations in the Lisfranc complex is crucial for diagnosing instability.

Purpose of the Study:

• To establish 3D WBCT Lisfranc variations in healthy individuals.
• To determine WBCT measurement cutoff values for diagnosing Lisfranc instability.

Main Methods:

• A retrospective analysis of 222 adult patients with bilateral foot WBCT scans was conducted.
• Lisfranc complex volume, axial area, and diastasis were measured, and percentage differences between contralateral feet were calculated.
• Area Under the Receiver Operator Curve (AUC) analysis was used to determine diagnostic cutoff values.

Main Results:

• Significant differences in WBCT measurements were observed between patients with Lisfranc instability and controls (P < .001).
• Diagnostic cutoff values were identified: 20% for volume, 26% for area, and 34% for diastasis.
• Diastasis demonstrated the highest diagnostic performance (AUC = 0.905) with a sensitivity of 0.813 and specificity of 0.900.

Conclusions:

• Physiologic differences between contralateral feet in healthy individuals are typically up to 12%.
• Lisfranc instability cases showed median percentage differences of ≥32%.
• Diastasis measurement offers the highest diagnostic accuracy for isolated Lisfranc instability, with a cutoff of 34%.