A new and original sonographic technique to document the morphology of
normal feet and splay feet is presented: a standard sectional plane c
uts the transverse arch from the plantar side using the sesamoids of t
he first metatarsal bone and the head of the fifth metatarsal bone as
reference points. A 5-MHz linear transducer and a rather simple custom
-made platform with an integrated gelpad are required in order to get
reproducible results. The morphology of the transverse arch can be cha
racterized by the ''transverse arch index Q'' as the parameter of the
relative height of the transverse arch. Based on this transverse arch
index Q, splay feet can be distinguished from normal feet in a statist
ically significant way (p < 0,01). Furthermore, grading of splay feet
is possible and a documentation of rigidity/flexibility of the forefoo
t in splay feet; thus, the decision on whether to use conservative or
operative treatment can additionally be based on sonographic documenta
tion, and the results of surgical reconstruction of the transverse arc
h can be checked and documented sonographically.