[Correlative study between length of first metatarsal and transfer metatarsalgia after osteotomy of first metatarsal].

OBJECTIVE

To evaluate the correlation between the length of first metatarsal, hallux valgus angle (HVA), intermetatarsal 1-2 angle (IMA1-2), plantar appearance, sesamoid position and postoperative 2-5 transfer metatarsalgia.

METHODS

Retrospective analysis was performed for the clinical data of 375 cases (626 feet) undergoing osteotomy of first metatarsal with mini-incision. All cases were examined radiographically via weight-bearing and lateral views. HVA, IMA1-2 and the length of first metatarsal were measured preoperatively and postoperatively. Forefoot plantar pressure was measured during walking by Foot scan system preoperatively and postoperatively.

RESULTS

After a mean follow-up period of 12-30 (18.5 ± 6.8) months, all patients had satisfactory bone healing without late healing or disunion. There were superficial wound infection (n = 1, 1 foot) and suture reaction (n = 1, 1 foot). HVA was 7.18° ± 4.55° postoperatively and corrected by 30.54°; IMA1-2 5.07° ± 1.70° and corrected by 12.33°. The number of shorting of first metatarsal during 0-2 mm was 424 feet, there was 1 case of transfer metatarsalgia at rays 4; the number during 2-4 mm was 186 feet, there were 5 cases of transfer metatarsalgia at rays 2. The center of pressure shifted laterally; the number during 2-4 mm was 16 feet, there were 4 cases of transfer metatarsalgia at rays 2 and 3. The center of pressure shifted evidently medially; the shorting of first metatarsal was 4.8 ± 0.46 mm. A negative correlation was found between length of metatarsal and transfer metatarsalgia at rays 2 and 3. No correlation existed between transfer metatarsalgia at rays 2 and 5, HVA and IMA1-2. A positive correlation existed between HVA decrease and patient satisfaction with their postoperative foot alignment. There was no correlation between lengthening of metatarsal and IMA1-2 decrease.

CONCLUSION

Length preservation of first metatarsal seems to prevent the postoperative transfer metatarsalgia on second and third rays. The shorting of first metatarsal should be no more than 2 mm.