Abstract
Category:
Midfoot/Forefoot; Trauma
Introduction/Purpose:
Early detection of Lisfranc instability is critical for improving clinical outcomes, but more subtle instability can be difficult to diagnose. Weightbearing computed tomography (WBCT) provides a unique opportunity to evaluate such injuries in three dimensions (3D) while under physiologic load. This study aimed to assess the utility of one-dimensional, two-dimensional, and three-dimensional measurements on weight-bearing computed tomography (WBCT) to diagnose subtle instability 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 (DLL) and interosseous Lisfranc ligament (IOL) to create subtle Lisfranc instability, and finally after transectioning of plantar Lisfranc ligament (PLL) to create complete Lisfranc instability. Measurements performed on WBCT images included: (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 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 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 0.001 to 0.014). Additionally, Lisfranc joint volume and area, C1-M2 distance, M1-M2 distance, TMT2 alignment and TMT2 dorsal step off measurements were increased in complete Lisfranc injury state. Of all measurements, C1-M2 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:
WBCT scan can accurately diagnose subtle Lisfranc instability. 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 instability. These findings suggest that 2D Joint Area and 3D Joint Volume have potential as supplementary measurements to more accurately diagnose subtle Lisfranc injuries.
