Effect of increasing distal medial closing wedge metatarsal osteotomies on the distal metatarsal articular angle.

The recognition, definition, and management of the congruent hallux valgus deformity continue to evolve. To correct the skeletal deformity and maintain joint congruity, many authors have emphasized the importance of extra-articular procedures. One such procedure is a distal medial closing wedge osteotomy of the first metatarsal. Unfortunately, there are few guidelines to help determine the pre- and intraoperative size of the medial wedge to obtain the desired correction of the distal metatarsal articular angle (DMAA). The purpose of this study was to quantify the effects of increasing distal medial closing wedge osteotomies on the DMAA in an in vitro cadaver model. In this study, a closing wedge osteotomy was performed 2 cm proximal to the articular surface, removing wedges measuring 2 mm, 4 mm, and 6 mm in width. The mean preoperative DMAA was 8.5 degrees, and the mean postoperative DMAAs after 2-mm, 4-mm, and 6-mm closing wedge osteotomies were -2.6 degrees, -10.2 degrees, and -20.2 degrees, respectively. The data showed that for every 1 mm of closing wedge osteotomy, the DMAA decreased by 4.7 degrees +/- 0.6 degrees. These results can be used for pre- and intraoperative planning when surgically correcting a congruent hallux valgus deformity with a distal medial closing wedge osteotomy of the first metatarsal. Additional information obtained from this cadaver study includes (1) increased shortening of the first metatarsal and (2) incongruity produced at the joint after the medial-based osteotomy. The amount of shortening of the first metatarsal correlated directly with the size of the medial-based wedge. The second point indicates that a lateral soft-tissue release may still be required when using this method of reorienting the DMAA.