Traumatic isolated Lis Franc ligament rupture - 44 yo female
Clinical History
A 44 years old female left foot injury 17 days ago while hopping on the foot after right foot surgery – heard a “snap”, felt a sharp pain on the dorsal aspect, followed by swelling. X-ray non-weight bearing no fracture seen. Query extensor tendon, flexor hallucis longus tendon or plantar fascia injury.
Ultrasound Findings
Midfoot dorsal aspect 1st and 2nd tarsometatarsal joints soft tissue swelling, increased vascularity, bone irregularity, separation of the bones, and focal tenderness. Comparison with the right side shows a significant difference.
Figure 1: 1st & 2nd TMT joints region soft tissue thickening, increased vascularity, and bone irregularity.
Figure 2: Comparison between right and left 1st & 2nd TMT joints.
Opinion
Lis Franc ligament rupture. Referred for weight bearing X-ray.
Feet X-ray weight bearing (following the ultrasound): Malalignment between the base of the 2nd metatarsal & medial margin of cuneiform with increased space between 1st & 2nd metatarsals. Consistent with Lis Franc ligament injury.
Figure 3: Bilateral weight bearing feet X-rays shows on the left side the region of abnormality (red circle) compared to the right side (blue circle).
Follow-up
Referral to Orthopaedic specialist sent for CT which showed comminuted fractures at the plantar aspect of the 1st & 2nd TMT joints. Small avulsion fractures at the dorsum & lateral aspects of the 3rd TMT joint.
There are three layers of Lis Franc ligaments; dorsal (weakest), interosseous (the Lis Franc ligament), and plantar. Unstable midfoot sprains when all three Lis Franc ligaments have ruptured require surgical repair – in this case open reduction & internal fixation (ORIF) x4 screws.
Figure 4: X-rays immediately after surgery open reduction internal fixation (ORIF).
Figure 5: Plantar ecchymosis is often a sign of Lis Franc ligament injury (Note image not from the patient from this case).
Reference
Granata JD and Philbin TM: The Midfoot Sprain: A Review of Lisfranc Ligament Injuries. The Physician & Sportsmedicine 119-126. December 2010 No 4, Vol.48.