Six first metatarsal shaft osteotomies: mechanical and immobilization comparisons.

Because malunion (usually with dorsal elevation of the first metatarsal) has been reported after the treatment of severe hallux valgus deformities by proximal osteotomies, the current study was designed to compare the sagittal stability of six different metatarsal shaft osteotomies: the proximal crescentic, proximal chevron, Mau, Scarf, Ludloff, and biplanar closing wedge osteotomies. A plate was used in the biplanar closing wedge osteotomy; all others used screws for fixation. Ten fresh-frozen, human anatomic lower extremity specimens were used for each osteotomy. Failure loads were measured as units of force (newtons) and converted to pressure (kilopascals). Then the F-Scan system, which uses a thin insole to measure plantar pressure, was used to evaluate the pressure under the first metatarsal of seven volunteers using four types of shoes. According to the results, in patients with normal bone stock who are compliant, any of the four shoe types tested may be used after a Ludloff, Scarf, biplanar wedge (plantar screw fixation), or Mau osteotomy, but the wedge-based shoe should be used after a proximal crescentic or chevron osteotomy or for patients with severe osteopenic bone.