Arch height and first metatarsal joint axis orientation as related variables in foot structure and function.
BACKGROUND
This study investigated the association of arch height combined with first metatarsal joint axis vertical (V) orientation to the size of the 1-2 intermetatarsal angle (IMA) and first metatarsal adduction/abduction position simulating foot postures during gait, kinematics commonly affected by bunion.


METHODS
Nine cadaver specimens were mounted in a loading frame. Measures of arch height ratio and IMA were made. With the foot placed in positions seen during normal gait cycle an electromagnetic device measured displacement of the relative angle of rotations between the first metatarsal and navicular, and helical axis (HA) parameters. Canonical correlation analysis assessed the relationship among the variables.


RESULTS
A negative relationship (r = -0.73) was found between arch height and first metatarsal HA V-orientation. When considered as combined variables, arch height and metatarsal HA V-orientation accounted for 69% of the variance of IMA and change in first metatarsal adduction/abduction position.


CONCLUSIONS
Orientation of the first metatarsal joint axis was highly variable between specimens but correlated with arch height. The conjoined factors of arch height and first metatarsal HA V-orientation accounted for most of the variance of IMA and change in first metatarsal adduction/abduction position during the sequence of foot position during simulated gait.


CONCLUSIONS
These findings suggest that orthotic arch support could reorient the metatarsal joint axis out-of-vertical and in effect, limit the first metatarsal from displacing into an adducted bunion deformity. These findings could help to explain the pathogenesis of bunions.
Program in Physical Therapy, University of Minnesota, Medical School, Mayo Mail Code 388, 420 Delaware St SE, Minneapolis, MN 55455, USA. glaso008@umn.edu
Ward
W
Glasoe
Fernando
F
Pena
Vandana
V
Phadke
Paula M
PM
Ludewig
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D005545:Forefoot, Human / Q000033:anatomy & histology* / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008682:Metatarsal Bones / Q000033:anatomy & histology*; D008683:Metatarsophalangeal Joint / Q000033:anatomy & histology* / Q000502:physiology; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D013640:Tarsal Joints / Q000033:anatomy & histology* / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology