Background: Early detection of Lisfranc injury is critical for improving clinical outcomes, but diagnosing subtle injury can be difficult. Weightbearing computed tomography (WBCT) allows evaluation of such injuries in 3 dimensions (3D) under physiologic load. This study aimed to assess the utility of 1-, 2-, and 3-dimensional measurements on WBCT to diagnose subtle injury in isolated ligamentous Lisfranc injuries.
Methods: Ten cadaveric specimens underwent WBCT evaluation of the Lisfranc joint complex in the intact state and subsequently with sequential sectioning of the dorsal Lisfranc ligament and interosseous Lisfranc ligament (IOL) to create subtle Lisfranc injury, and finally after transectioning of plantar Lisfranc ligament (PLL) to create the injury conditions for complete ligamentous Lisfranc injury. Measurements under static vertical tibial load of 80 kg were performed on WBCT images including (1) Lisfranc joint (medial cuneiform-base of second metatarsal) volume, (2) Lisfranc joint area, (3) C1-C2 intercuneiform area, (4) C1-M2 distance, (5) C1-C2 distance, (6) M1-M2 intermetatarsal distance, (7) first tarsometatarsal (TMT1) alignment, (8) second tarsometatarsal (TMT2) alignment, (9) TMT1 dorsal step-off distance, and (10) TMT2 dorsal step-off distance.
Results: In the subtle Lisfranc injury state, Lisfranc joint volume and area, C1-M2 distance, and M1-M2 distance measurements on WBCT significantly increased, when compared with the intact state (P values .001 to .014). Additionally, Lisfranc joint volume and area, C1-M2 distance, M1-M2 distance, TMT2 alignment, and TMT2 dorsal step-off measurements were increased in the complete Lisfranc injury state. Of all measurements, C1-M2 distance had the largest area under the curve (AUC) of 0.96 (sensitivity = 90%; specificity = 90%), followed by Lisfranc volume (AUC = 0.90; sensitivity = 80%; specificity = 80%) and Lisfranc area (AUC = 0.89; sensitivity = 80%; specificity = 100%).
Conclusion: In a cadaveric model we found that WBCT scan can increase the diagnostic accuracy for subtle Lisfranc injury. Among the measurements, C1-M2 distance exhibited the highest level of accuracy. The 2D joint area and 3D joint volume also proved to be accurate, with 3D volume measurements of the Lisfranc joint displaying the most significant absolute difference between the intact state and increasing severity of Lisfranc injury. These findings suggest that 2D joint area and 3D joint volume may have potential as supplementary measurements to more accurately diagnose subtle Lisfranc injuries.
Clinical relevance: WBCT may help surgeons detect subtle Lisfranc injuries.
Keywords: Lisfranc; Lisfranc joint; injury; instability; tarsometatarsal joint; weightbearing computed tomography.