An osteotomy in the proximal first metatarsal will produce, because of the long lever arm, correction of the metatarsal head position with much less movement of the fragment than an equivalent osteotomy in the distal part of the bone. It is therefore able to correct very severe deformities which may be beyond distal or diaphyseal procedures.
The corollary of the long lever arm argument, however, is that ground reaction force on the metatarsal head exerts a larger bending moment on a proximal osteotomy than on a distal one. Therefore, there have been problems with dorsal malunion and metatarsalgia.
Resch's RCT comparing distal chevron and proximal closing wedge osteotomies illustrates this well: the proximal osteotomies achieved better correction of deformity but the results were no better because of an increased incidence of metatarsalgia. The different types of proximal osteotomy are attempts to overcome these potential problems.
Faber's (2004) RCT comparing the Hohman (distal) metatarsal osteotomy with the Lapidus procedure (actually a first tarsometatarsal fusion, but essentially a proximal procedure) again showed no difference in clinical outcome.
Both Stienstra (2002) and Schneider (2004) displaced the distal chevron osteotomy more than half-shaft diameter, to the point where it might have been expected to be unstable as illustrated above. They obtained corrections of deformity that might have been expected from a proximal osteotomy.
Neither Resch nor Faber selected patients with severe deformities, who would normally be the patients in whom a proximal osteotomy would be specifically advised. Nevertheless, it appears that the theoretical advantages of proximal osteotomies may not be bourne out in clinical trials. Nevertheless, it is not unusual to see patents in tertiary clinics who have had inadequate correction with a distal procedure who are significantly improved with a proximal procedure. Further trials comparing well-chosen proximal and distal osteotomies are needed to show whether the greater complexity and potential complications of proximal osteotomies are justified by improved outcomes in appropriate patients. Forr the moment, in the exam, it would be best to recommend a proximal osteotomy (or perhaps a scarf procedure) in patients with severe deformities.