Assessing Lisfranc Instability With Triplanar Weightbearing CT Alignment: Standardized Second Metatarsal Dorsal...

Area of Science:

• Orthopedic surgery
• Radiology
• Biomechanics

Background:

• Subtle Lisfranc injuries often go undetected with conventional imaging.
• Weightbearing computed tomography (WBCT) provides 3D assessment under load, potentially improving instability detection.
• The interval between the medial cuneiform (C1) and second metatarsal (M2) is a common measurement, but sagittal displacement may offer additional diagnostic value.

Purpose of the Study:

• To evaluate the reliability and diagnostic utility of a new WBCT measurement, second metatarsal dorsal offset (M2DO), for detecting Lisfranc instability.
• To compare M2DO measurements between injured and uninjured feet.
• To assess the intra- and interobserver reliability of the M2DO measurement.

Main Methods:

• Retrospective analysis of 31 patients with acute Lisfranc injuries who underwent bilateral WBCT.
• Standardized measurement of M2DO following triplanar alignment of the second metatarsal (M2) relative to the second cuneiform (C2).
• Independent measurements by two foot and ankle surgeons, with one repeating measurements after two weeks to assess reliability.

Main Results:

• M2DO showed a significant difference between injured (0.71 ± 1.18 mm) and uninjured feet (-0.74 ± 0.66 mm) (P < .0001).
• Intra- and interobserver reliability for M2DO was almost perfect in injured feet (intrarater 0.92, interrater 0.94) and the overall cohort (0.93, 0.92).
• Substantial reliability was observed in uninjured feet (intrarater 0.79, interrater 0.67).

Conclusions:

• Second metatarsal dorsal offset (M2DO) is a reliable parameter derived from WBCT for assessing Lisfranc instability.
• M2DO may complement existing C1-M2 measurements, enhancing diagnostic accuracy and reproducibility.
• Further research is needed to establish M2DO thresholds for surgical decision-making and clinical application.