Microvasculature of the Distal Fifth Metatarsal Following Open vs Percutaneous Bunionette Correction: A Cadaveric Micro-Computed Tomography Analysis

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Distal 5th metatarsal osteotomy is often used for correction of symptomatic bunionette deformities when conservative treatment fails. There is limited data regarding the effect of distal 5th metatarsal osteotomy on the surrounding microvasculature. The primary aim of this study was to use MicroCT to compare the rate of vascular injury between open and percutaneous techniques for distal 5th metatarsal osteotomy. We hypothesized that percutaneous osteotomy would have a lower rate of vascular injury compared to the open technique. Methods: A total of 20 fresh-frozen cadaveric limbs (10 matched pairs) were used for this study. All specimens were disarticulated at the knee and without previous foot and/or ankle surgery. Proximally the popliteal artery was cannulated using an 18-gauge angiocath, and the limbs were flushed with 500mL of warmed 0.9% saline, 500mL 3% hydrogen peroxide, and 500mL of water. Perfusion was then performed using 50mL of radiopaque contrast (50% barium sulfate, 2.5% gelatin). The lateral forefoot was resected en-bloc and scanned using a MicroCT (Sky-Scan-1275, Bruker MicroCT) to obtain baseline microvascular anatomy. Each matched pair then underwent open (9x25 microsagittal saw) or percutaneous (2x12mm Shannon burr) transverse osteotomy of the distal 5th metatarsal. The head was shifted medially and fixed with a retrograde 0.062 Kirschner wire. MicroCT scans were again performed and qualitatively analyzed to compare incidence of microvascular injury. Results: Baseline anatomy and course of the dorsal metatarsal artery, plantar metatarsal artery, medial branch of the plantar metatarsal artery, and lateral branch of the plantar metatarsal artery were visualized in all specimens. Nutrient vessels to the metatarsal head and neck were found to have variable distribution and branching points, even within matched pairs. There were 4 lacerations of the dorsal metatarsal artery (3 open, 1 percutaneous) and 2 lacerations of the lateral branch of the plantar metatarsal artery, both in the open group. All injuries occurred at the level of the osteotomy, consistent with iatrogenic injury. Conclusion: In this cadaveric study, open osteotomy of the distal 5th metatarsal resulted in a higher incidence of iatrogenic vascular injury compared to percutaneous osteotomy. The dorsal metatarsal artery was the most commonly injured arterial vessel, followed by the lateral branch of the plantar metatarsal artery. Although disruption of surrounding microvasculature might impede healing, the clinical implications of these findings remain unclear. Further in vivo studies are needed to assess if there is a difference in union rates between open and percutaneous 5th metatarsal osteotomy for bunionette correction.