Accuracy of Ultrasound Imaging of the Lisfranc Joint Complex

Abstract

Lisfranc injuries account for 1 in 55,000 injuries yearly and are associated with poor outcomes and high complication rates. Superficially connecting the medial cuneiform and second metatarsal, the dorsal Lisfranc ligament is easily visualized with ultrasound. Ultrasound can provide quick, cost effective diagnosis but is not currently standard in clinical practice. PURPOSE: This study sought to compare measurement accuracy of the dorsal Lisfranc ligament using ultrasound, external software, and gross anatomic dissection, with an additional anatomic study of the joint complex. METHODS: Ultrasound images of 22 embalmed cadaveric feet (13 male, 9 female, 79.5±13.3 years) were obtained using a 6-13MHz linear array. Dorsal Lisfranc ligament length and joint space were measured and compared between methodologies. Images were also re-measured using ImageJ software. Specimens were dissected to evaluate dorsal, interosseous, and plantar Lisfranc ligaments. Joint complex morphology was documented. RESULTS: Ultrasound (8.39±1.26 mm) and ImageJ measurements (8.26±1.76 mm) of the dorsal Lisfranc ligament did not differ significantly, but both were significantly different (p < 0.05) than gross dissection (10.8± 1.84 mm). There were no significant differences in dorsal joint space measures between ultrasound (2.19±0.49 mm) and ImageJ (2.05±0.52 mm), but both were significantly different (p < 0.05) than dissection measurements (1.04±0.24 mm). The dissected dorsal and interosseous ligaments had consistent morphology, whereas the plantar ligament demonstrated a Y- and a fan-shaped variant. A connection between the interosseous and plantar ligaments was present in 64% of dissections. CONCLUSION: The dorsal Lisfranc ligament is easily visualized on ultrasound with 23% of the ligament not clearly visible at the peripheral bony attachments. While visually underrepresented on ultrasound, measurements were consistent. Radiographic joint space measurement remains the diagnostic gold standard. Further research should focus on using ultrasound to measure both bony and ligament integrity. Ligament echogenicity provides additional diagnostic information to assess more subtle joint injuries. Additionally, the plantar Lisfranc ligament variability may impact the stability of the joint in some patients.