title: Observed changes in radiographic measurements of the first ray after frontal plane rotation of the first metatarsal in a cadaveric foot model.
abstract: We observed the changes in the angular measurements commonly used in the evaluation of the first metatarsal and first metatarsophalangeal joint in cadaveric specimens before and after frontal plane rotation of the first metatarsal. Measurements of the first and second intermetatarsal angle (IMA), hallux abductus angle, proximal articular set angle, and tibial sesamoid position (TSP) were taken after varying degrees of varus and valgus rotation of the first metatarsal. Standard dorsoplantar radiographs were taken at 0°, 10°, 20°, and 30° of valgus rotation of the first metatarsal and repeated at 10°, 20°, and 30° varus rotation of the first metatarsal. The data were analyzed using a mixed linear model to compare the change in each angle measurement over the range of valgus and varus rotation. The change in the TSP was significant in both valgus and varus rotations (p = .0004 and p = .028, respectively), an increase in valgus rotation causing an increase in the TSP and an increase in varus rotation causing a decrease in TSP. The change in the IMA was significant compared with valgus rotation (p = .028), showing that as the valgus rotation increased, the IMA also increased. However, compared with the varus rotation, the correlation was not significant (p = .18). The proximal articular set angle and hallux abductus angle measurements, compared with metatarsal rotation, showed positive trends but were not statistically significant. From our results and a review of the published data, we have hypothesized that frontal plane rotation of the first metatarsal is an integral component of hallux abducto valgus pathologic features, specifically in relation to the TSP and IMA.
authors.affiliation: Unity Point Health, Trinity Regional Medical Center, Des Moines University College of Podiatric Medicine and Surgery, Fort Dodge, IA. Electronic address: daytonp@me.com.
authors.forename: Paul
authors.initials: P
authors.lastname: Dayton
authors.affiliation: Des Moines University College of Podiatric Medicine and Surgery, Des Moines, IA.
authors.forename: Mindi
authors.initials: M
authors.lastname: Feilmeier
authors.affiliation: Des Moines University College of Podiatric Medicine and Surgery, Des Moines, IA.
authors.forename: Jordan
authors.initials: J
authors.lastname: Hirschi
authors.affiliation: Des Moines University College of Podiatric Medicine and Surgery, Des Moines, IA.
authors.forename: Merrell
authors.initials: M
authors.lastname: Kauwe
authors.affiliation: Departments of Biology and Neuroscience, Brigham Young University, Provo, UT.
authors.forename: John S K
authors.initials: JS
authors.lastname: Kauwe
mesh_terms: D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006214:Hallux / Q000000981:diagnostic imaging*; D006801:Humans; D008682:Metatarsal Bones / Q000000981:diagnostic imaging*; D008683:Metatarsophalangeal Joint / Q000000981:diagnostic imaging*; D011859:Radiography; D012399:Rotation
keywords: hallux valgus; intermetatarsal angle; metatarsal phalangeal joint; sesamoid position