Listract test: a Standardized Assessment Method for Isolated Lisfranc Instability in Cadaver Models

BackgroundThe gold standard for diagnosis of Lisfranc instability is direct visualization in the operation room while the examination techniques is still unstandardized and non-reproducible. We aimed to introduce a novel reproducible intraoperative mechanical testing method (Listract test) for intraoperative isolated Lisfranc instability assessment. MethodsThe Lisfranc ligament between the first cuneiform (C1) and second metatarsus (M2) in eight lower leg cadaveric specimens were dissected to replicate C1-M2 Lisfranc instability by eight foot and ankle surgeons. The 50N distraction force was applied in the direction of the C1-M2 ligament. Three methods of fixation - flexible fixation, metal screw, and bio-absorbable screw- were used to fix the injury, and Listract test was applied again after fixation. Besides intraoperative assessment, C1-M2 diastasis and area were measured using radiographs for assessment of Lisfranc instability. ResultsThe sensitivity and specificity of the Listract test for detection of C1-M2 instability were 100% and 100% intraoperatively, 33.3% and 95.2% using radiographic diastasis measurement, and 63.2% and 38% using area measurement, respectively. The Listract test had a specificity and sensitivity of 100% and 96% for intraoperative assessment, 87.5% and 64.3 for radiographic C1-M2 diastasis, and 48% and 50% for radiographic area. ConclusionThe Listract test is a simple, reproducible, and replicable intraoperative method for evaluating the Lisfranc joint for instability. Developing a device with this mechanism can help clinicians confirm the diagnosis and provide appropriate treatment particularly for equivocal diagnoses. Authors contributionsSAE: Conception, design, and conducting the study, analysis, drafting the manuscript; VM, DOH, SHSH, FR: conducting the study, analysis, preparing the manuscript draft; LBP, JK, GW, PK: conducting the study, manuscript preparation, discussion.