Is Pes Cavus Alignment Associated With Lisfranc Injuries of the Foot?

BACKGROUND: Lisfranc (tarsometatarsal joint) injuries are relatively rare, accounting for less than 1% of all fractures, and as many as 20% of subtle Lisfranc injuries are missed at the initial patient presentation. An undiagnosed Lisfranc injury can have devastating consequences to the patient. Therefore, any factor that can raise a clinician's index of suspicion to make this diagnosis is potentially important. The cavus foot has been associated with various maladies of the lower extremity, but to our knowledge, it has not been reported to be associated with Lisfranc injury. QUESTIONS/PURPOSES: Do patients who experience a low-energy Lisfranc injury have greater talar head coverage and a greater talo-first metatarsal angle than control subjects? METHODS: A retrospective, case-control study was conducted from September 2011 to December 2014 to identify patients diagnosed and treated for a low-energy Lisfranc injury. Twenty-three adult patients with an average age of 42.6 years (SD, 16.3 years) were identified and compared with 61 adult control subjects with an average age of 49.4 years (SD, 14.1 years). Control subjects came from the practice of a fellowship-trained foot and ankle orthopaedic surgeon. Control subjects underwent a history and physical, clinical examination, and diagnostic imaging to confirm that they had no prior foot disorder, no prior foot surgeries, were within 3 years of age of a patient with a Lisfranc injury, and were independent ambulators. Two authors (DSD and JDP) measured the talonavicular and talo-first metatarsal angles on weightbearing AP and lateral radiographs of the foot. The intrarater reliability and interrater reliability for the talo-first metatarsal angle and the talonavicular angle showed high agreement. The intrarater intraclass correlation coefficients (ICC) of the talo-first metatarsal angle were 0.94 (95% CI, 0.91-0.96) and 0.93 (95% CI, 0.9-0.96). For the talonavicular angle the ICCs were 0.83 (95% CI, 0.75-0.89) and 0.88 (95% CI, 0.81-0.92) for Raters 1 and 2 respectively. The interrater ICCs were 0.91 (95% CI, 0.69-0.96) for the talo-first metatarsal angle and 0.9 (95% CI, 0.85-0.94) for the talonavicular angle. The patients and controls were compared to determine if the patients who sustained a Lisfranc injury were more likely to have a pes cavus foot alignment. We performed a mixed modeling analysis to control for potential cofounding variables and determine if there was an association of Lisfranc injury with the talo-first metatarsal angle and the talonavicular angle. RESULTS: After controlling for confounding variables such as the effect of the measurement round effect and the effect of the rater, our repeated measures analysis via mixed model showed patients were associated with a higher talo-first metatarsal angle than control subjects (adjusted least square mean for patients = 3.05; for controls = -2.65; mean difference, 5.7; p = 0.001). Repeated measures analysis via mixed model showed that patients also were associated with a more positive talonavicular angle than control subjects (adjusted least square mean for patients = -4.83, for controls = -11; mean difference, 6.17; p = 0.002). Patients with Lisfranc injuries had a higher mean talo-first metatarsal angle than did control subjects (1.9° ± 7.9° versus -2.2° ± 7.3°; mean difference, 4.1°; 95% CI, -7.7° to -0.5°; p = 0.028), and less talar uncovering (-4.2° ± 9.7° versus -11° ± 8°; mean difference, 6.7°; 95% CI, -6.7° to -10.8°; p = 0.001). CONCLUSIONS: We found that cavus midfoot alignment was more prevalent among patients with Lisfranc injuries than among individuals with no foot injury or disorder. Although this does not suggest that cavus alignment causes or predisposes patients to this injury, we believe the finding is important because this provides a radiographic parameter that clinicians can use to raise their index of suspicion for a Lisfranc injury and aggressively pursue this diagnosis. Future studies would benefit from obtaining contralateral foot imaging at the time of injury in all patients with Lisfranc injury or prospectively following patients with foot imaging and recording the incidence of future foot injury. LEVEL OF EVIDENCE: Level III, prognostic study.