Lower-grade midfoot sprains are difficult to detect on plain imaging and fracture-dislocation classification systems are not suitable for Lisfranc injuries without a fracture present.
The Nunley-Vertullo classification of Lisfranc injuries was developed to classify low-grade midfoot sprains on weight-bearing radiographs.
- grade 1
- low-grade ligament sprain
- no findings on the weight-bearing radiograph
- positive bone scan
- grade 2
- ligament insufficiency or disruption with an intact plantar ligament
- 2–5-mm M1-M2 diastasis on a weight-bearing radiograph
- grade 3
- complete ligament disruption
- >5-mm M1-M2 diastasis on DP weight-bearing radiograph
- loss of arch height on the lateral projection