The influence of metatarsal support height and longitudinal axis position on plantar foot loading.
BACKGROUND
Metatarsal supports are effective at decreasing plantar foot pressures at the metatarsal heads, however, little is known about the dependence of this decrease upon height and position.


METHODS
Barefoot static stance pressure measurements were recorded during standing in single limb support (n=22). Two metatarsal support heights (5mm, 10mm) were evaluated in six positions at 5mm increments (0, 5, 10, 15, 20, 25 mm) proximal to the metatarsal heads along the longitudinal axis of the foot. The barefoot condition with no metatarsal support served as the control. Mean force was measured for each test condition. The findings of this study are limited to the barefoot (unshod) condition.


RESULTS
Mean plantar force decreased significantly under the second metatarsal head with both 5 and 10mm metatarsal supports compared to the control, and 10mm metatarsal support compared with 5mm metatarsal support (P<0.05) while no statistically significant differences were noted relative to longitudinal axis position.


CONCLUSIONS
The results of this study suggest that the thickness of a metatarsal support is a determinant factor in regulating plantar loading. Surprisingly, the longitudinal axis location of a metatarsal support does not appear to be as important as clinically presumed since the data showed that the force decrease was similar for all positions from 5 to 25 mm. Thus, the orthotic induced effect of a metatarsal support seems to have a sizable interaction range that has not previously been reported. We speculate that the metatarsal support's fulcrum and lift effect can be sustained at a more proximal position due to the foot's rigidity as a lever and the manner in which a metatarsal support interacts with the plantar aponeurosis.
Department of Rehabilitation, School of Health Sciences, Jönköping University, Sweden. Thor-Henrik.Brodtkorb@ihs.liu.se
Thor-Henrik
TH
Brodtkorb
Géza F
GF
Kogler
Anton
A
Arndt
D000328:Adult; D003198:Computer Simulation; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D008297:Male; D008682:Metatarsal Bones / Q000502:physiology*; D008954:Models, Biological; D009989:Orthotic Devices; D016474:Weight-Bearing / Q000502:physiology*