Spontaneous Reduction in the Intermetatarsal Angle in Distal First Metatarsal Osteotomies with No Lateral Head Displacement in Hallux Valgus.

Background: The outcomes of first metatarsal (M1) distal osteotomies in hallux valgus (HV) can be improved, especially for intermetatarsal angle (IMA) correction, which is mainly based on lateral displacement of the M1 head (i.e., translation) through the osteotomy. Conversely, there is a spontaneous reduction in the IMA in first metatarsophalangeal joint (MTP1) arthrodesis. But we do not know whether this can be applied to distal osteotomies. We propose a distal osteotomy, called 3D chevron, which combines supination and varization of the M1 head. This might realign soft tissues around the MTP1, potentially leading to a spontaneous reduction in the IMA by an analogous mechanism to MTP1 fusion. Therefore, our study aimed to assess whether spontaneous reductions in IMAs exist in distal M1 osteotomies in the absence of lateral translations of M1 heads.

Methods: A prospective continuous series of 25 3D chevrons was performed. Two groups were formed during surgery. Patients requiring no M1 head lateral displacement were included in the "successful correction without translation" group, and patients requiring M1 head lateral displacement were included in the "failed correction without translation" group. Radiographic analysis was performed preoperatively and at 1 year postoperatively.

Results: Twenty-two women and three men, with a mean age of 44.8 ± 14.2 years and a mean body mass index of 22.6 ± 4.1 kg/m, underwent follow-up at one year after surgery. The "successful correction without translation" group was composed of HV with milder deformities (13/25 HVs, median preoperative IMA = 13 (IQR 2)) compared to the "failed correction without translation" group (median IMA = 16 (IQR 2.25) < 0.001). Spontaneous reductions in IMAs were observed in the "successful correction without translation" group, with a median decrease in the IMA of 6 degrees (CI95%[5.5; 8.0]; < 0.001) between preoperative and 1-year radiographs.

Conclusion: Distal osteotomies allow for spontaneous reduction in the IMA in HV. First metatarsal head translation through an osteotomy should not be considered as the only procedure to correct IMAs in distal osteotomies.