Anatomical and Micro-CT Assessment of the First Metatarsal Head Vascularization and Soft Tissue Envelope Following Minimally Invasive Chevron Osteotomy for Hallux Valgus Deformity.

Abstract

Background: Minimally invasive surgical (MIS) chevron-type osteotomy for hallux valgus (HV) treatment offers a surgical alternative to open surgery with minimal surgical dissection and a hypothetical decreased risk for soft tissue complications. The objectives of this study were to assess the incidence of injuries to the soft tissue envelope and to the blood supply of the first metatarsal head through gross dissection and, using micro-computed tomography (micro-CT), to identify the safe position to perform the MIS chevron-type osteotomy of the first metatarsal head based on the anatomical data.

Methods: Twenty cadaveric specimens with HV were used for the study. Seven specimens were perfused with a low-viscosity radiopaque polymer preoperatively. All specimens underwent MIS chevron-type osteotomy executed using a 20 × 2-mm Shannon burr at the metatarsal neck's flare. Anatomical dissection of all specimens was then performed to assess macroscopic injury to the first metatarsal head complex soft tissue structures and blood supply. The 7 specimens that were preinjected then underwent micro-CT assessment to assess the first metatarsal head blood supply.

Results: Two soft tissue injuries in 2 cadavers were identified, including a 2-mm injury to the flexor hallucis brevis in one specimen and a 1-mm injury to the dorsomedial nerve. No arterial injuries were identified in either the gross dissection or micro-CT imaging. Micro-CT has pinpointed a secure location to complete the chevron-type osteotomy. We found that finalizing the dorsal arm of the MIS chevron-type osteotomy at a median distance of 25.6 mm, and the plantar arm at 23.9 mm from the most distal point of the first metatarsal head, ensured safety in the specimens we used.

Conclusion: As tested in this cadaveric study on 20 specimens, the MIS chevron-type osteotomy procedure preserved the soft tissue envelope of the first metatarsal head complex and the blood supply of the first metatarsal head, with a low number of injuries. Completing the dorsal arm of the MIS chevron-type osteotomy at a median distance of 25.6 mm, and the plantar arm at 23.9 mm from the furthest point of the first metatarsal head, while ensuring the Shannon burr does not exceed 3.9 mm dorsolaterally and 4.0 mm plantar-laterally from the cortical bone exit point, appeared crucial to avoid vascular damage.