The risks and benefits of distal first metatarsal osteotomies.

From a total of 138 patients who initially underwent either Chevron or Mitchell distal metatarsal osteotomies, 50 were available with complete pre- and postoperative data for study. Chevron osteotomies were performed on 60 feet (41 patients) and Mitchell osteotomies on 12 (nine patients). The results indicate that both procedures provide good or excellent subjective and objective results in about 90% of cases. There was no statistically significant difference between the procedures as regards the results. Age did not influence the outcome. Complications included damage to the proper digital nerve of the great toe in 30% indicating either direct injury to the nerve with subsequent neuroma formation or indirect injury by nerve entrapment. Osteonecrosis of the first metatarsal head occurred following Chevron osteotomies in 12 feet (12 of 60 or 20%) and following a Mitchell in one (one of 12 or 8%). However, four of the 10 (40%) patients who had a Chevron osteotomy plus a lateral adductor release developed osteonecrosis. Osteonecrosis is described and classified into three stages: stage I, the precollapse condition; stage II, the collapsed condition; and stage III, the osteoarthritic condition. The major causes of failure were preexisting osteoarthritis, injury to the dorsal proper digital nerve, and osteonecrosis. Theoretically, most of these should be avoidable. Significant metatarsus primus varus and MTP osteoarthritis are contraindications to distal metatarsal osteotomies. A tourniquet should be routine and the nerve, visualized and protected. If a distal osteotomy is performed, a concomitant lateral adductor release is contraindicated and stripping of the distal soft tissues should be minimal.