Comparison of dorsal and dorsomedial displacement in evaluation of first ray hypermobility in feet with and without hallux valgus

Background: Hypermobility of the first ray, a probable primary cause of hallux valgus, has traditionally been evaluated in the dorsal direction only although the first tarso-metatarsal joint allows movement in a dorso-medial direction. Materials and methods: 600 feet, divided according to the presence or absence of hallux valgus, were evaluated for both dorsal and dorso-medial displacement using a Klaue device. Results: In the control group, the mean first ray displacement was 7.2 mm (4.2–11.3) in the dorsal direction (sagittal plane) and 8.3 mm (4.0–12.6) in the 458 dorso-medial direction. In the hallux valgus group, the mean first ray mobility was 9.8 mm (5.2–14.1) in the dorsal direction compared to a mean of 11.0 mm (5.9–16.2) in the 458 dorso-medial direction. Conclusion: It is a paradox that hypermobility of the first ray is measured in only a dorsal (vertical) direction whereas a hallux valgus angle and an intermetatarsal angle are only measured in a transverse plane. Furthermore, the weightbearing foot pronates during gait and the first metatarsal is displaced in a dorsomedial direction rather than a pure dorsal direction. It is suggested that measurement hypermobility of the first ray at a 458 dorso-medial direction is more appropriate. 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.