[Calculation of hallux bending moments from plantar pressure distribution measurement].
OBJECTIVE
The following study aims to demonstrate the bending stress on a hallux valgus during normal gait. The bending axis was related to the position of an open wedge osteotomy. The moments were calculated from plantar pressure measurements.


METHODS
In the gait analysis laboratory plantar pressure distribution measurement was done with healthy adult volunteers during barefoot gait. From the plantar pressure distribution the vertical forces were derived just for the region hallux metatarsal I. The following calculation of the bending stress regarding to the hypothetic region of the osteotomy was done by integrating the pressure distribution multiplicated with the distance to the osteotomy. The measurements are compared with theoretical values derived from the anatomy of the foot under some plausible assumptions.


RESULTS
The results of the mean values of the bending stress were 15.8 +/- 4.8 Nm for the female subjects and 21.6 +/- 5.6 Nm for the male subjects. The amount of the bending moments depended with low significance on the weight. More important is the individual type of gait.


CONCLUSIONS
The measurements show the size of bending stress the plate stabilizing the osteosynthesis has to resist under unfavorable circumstances (for example if the plantar foot muscles are not adequately activated) and if no external stabilization (for example, cast) is used.
Lampe
R
R
Gang- und Bewegungsanalyselabor, Klinik für Orthopädie und Sportorthopädie der TU München, Klinikum Rechts der Isar, Munich. renee.lampe@lrz.tu-muenchen.de
Mitternacht
J
J
Steinhauser
E
E
Gerdesmeyer
L
L
Gradinger
R
R
D000293:Adolescent; D000328:Adult; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D005528:Foot / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006214:Hallux / Q000502:physiology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011312:Pressure; D013314:Stress, Mechanical; D025321:Surgery, Computer-Assisted / Q000379:methods; D019415:Torque