Percutaneous Distal Metatarsal Mini-Invasive Osteotomy: Comparison Between Standard vs Modified Intraosseous Approach: A Cadaveric Study

CATEGORY: Midfoot/Forefoot INTRODUCTION/PURPOSE: Minimally invasive surgery (MIS) of the forefoot has gained popularity as an alternative to traditional open procedures for the treatment of metatarsalgia and hammertoe deformity. Distal metatarsal mini-invasive osteotomy (DMMO) is an extraarticular osteotomy done in a percutaneous manner, with minimal soft tissue dissection that permits elevation as well as shortening. However, there is concern for damage to vital structures due to lack of direct visualization. The objective of the study was to evaluate the structures at risk in standard versus modified DMMO. METHODS: 11 thawed fresh-frozen cadaveric specimens underwent minimally invasive DMMO using both the standard and modified approach. The standard technique was performed by moving the burr in a circular motion with an angle of 45° (right- handed surgeon), which cut sequentially the left, plantar, right and dorsal cortices. It was compared to a modified intraosseous technique requiring less wrist supination while remaining intraosseous. After completion of the procedures, the cadavers were fully dissected and analysed to identify unintentional injury to soft tissue structures and to verify if cuts were completely extraarticular and performed with proper angulation. RESULTS: In the standard group the most commonly injured structures were the metatarsal joint capsules (MJC) (27%), extensor digitorum longus (EDL) (18%), and extensor digitorum brevis (EDB) (9%). The modified intraosseous group demonstrated injury to the EDL (27%), while MJC (0%) and EDB (0%) were not damaged. Distances between osteotomies and structures were 6.08 +- 3.99 mm from the dorsal metatarsal head articular surface (DMHAS), 4.85 +- 2.45 mm from EDB and 0.76 +- 1.72 mm from the EDL in the standard group and 9.92 +- 3.42 mm from the DMHAS, 4.71 +- 3.24 mm from EDB and 1.24 +- 1.84 mm from the EDL in the modified group. Statistically significant difference was found among osteotomy site and DMHAS (p=0.02). CONCLUSION: The most frequently injured structure was the EDL tendon with both DMMO techniques used. Intra-articular positioning of the osteotomy was more frequently observed in the standard technique. There was also a statistically significant difference between the distance of the osteotomy site and the dorsal metatarsal head articular surface when comparing the standard group and the modified group. Overall, it appears that the modified method could be a safer, less complex alternative to the standard DMMO technique, especially for the inexperienced surgeons.