Microvasculature of the First Tarsometatarsal Joint Following Open vs MIS Lapidus Bunionectomy: A Cadaveric Micro-Computed Tomography Analysis

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Arthrodesis of the 1st tarsometatarsal joint (modified Lapidus) is an option for surgical correction of moderate to severe hallux valgus deformity. There is little data on the effect of Lapidus bunionectomy on the surrounding microvasculature. The primary aim of this study was to use MicroCT perfusion imaging to compare the rate of vascular injury between open and minimally invasive (MIS) Lapidus bunionectomy techniques. We hypothesized that MIS Lapidus would have a lower rate of vascular injury compared to the open technique. Methods: Twenty-four fresh-frozen cadaveric limbs (12 matched pairs) were disarticulated at the knee. The popliteal artery was cannulated using an 18-gauge angiocath. The arterial system was perfused with 50mL of radiopaque contrast (50% barium sulfate/2.5% gelatin). For controls (n=12) the medial midfoot was resected en-bloc and scanned using MicroCT. The contralateral feet underwent either open (n=6, dorsal approach) or MIS (n=6, medial approach) Lapidus fusion. For the open technique the joint was scraped with a curette and fenestrated with a 2 mm drill bit. For the MIS technique the joint was prepped with a 2x12 mm Shannon burr using fluoroscopic guidance. For both techniques, fixation entailed two crossing dorsal to plantar 4.0 mm cannulated screws. After fixation, the medial midfoot was resected en-bloc. MicroCT scans were performed and qualitatively analyzed to compare incidence of microvascular injury between the two Lapidus techniques. Results: Nutrient vessels were found to have variable distribution and branching points, even within matched pairs. There were 2 arterial injuries in the open group involving the first proximal perforating artery (n=1) and the deep plantar arterial arc (n=1). There were 8 arterial injuries in the MIS group involving the first proximal perforating artery (n=4), the deep plantar arterial arc (n=3), and the first plantar metatarsal artery (n=1). All injuries occurred at the level of the 1st TMT joint, consistent with iatrogenic injury. Conclusion: Percutaneous Lapidus fusion of the 1st TMT joint resulted in a higher incidence of microvascular injury as compared to open Lapidus. The first proximal perforating artery and the deep plantar arterial arc were the most commonly injured arterial vessels. The clinical implications of these findings remain unclear, and further in vivo studies are needed to assess if there is a difference in union rates between open and MIS Lapidus procedures.