Landmarking an Extra-Capsular Position for Minimally Invasive Transverse First Metatarsal Osteotomy for Hallux Valgus...

BackgroundMinimally invasive hallux valgus reconstruction is a technique that has been undergoing refinements since its inception. The fourth-generation technique differentiates itself with a transverse metatarsal osteotomy. The location of this osteotomy is a key consideration. It is desirable for this osteotomy to be as distal as possible while remaining extra-capsular and preserving the blood supply to the capital fragment. Limited guidance exists for identifying this position intraoperatively. This cadaveric investigation aims to identify an extra-capsular location for a transverse metatarsal osteotomy for fourth-generation hallux valgus reconstruction and assess the effects of this osteotomy on the blood supply to the capital fragment.MethodsTen clinical-grade cadaveric specimens were injected with radiopaque contrast to define the first metatarsophalangeal (MTP) joint capsule. Measurements from the metatarsal head and the sesamoids to the proximal edge of the capsule were recorded from the radiographic images. Using fluoroscopic guidance, a transverse minimally invasive osteotomy was performed near the capsule border. Anatomic dissections assessed capsular integrity and vascular supply to the distal first metatarsal.ResultsRadiographic measurements showed that the distance between the articular surface and proximal edge of the capsule was 27.3 mm. Mean distance from the articular surface of the metatarsal head to the osteotomy was similar at 27.3 mm. Distances from the medial and lateral sesamoids to the proximal edge of the capsule were 3.8 mm and 3.9 mm, respectively. An osteotomy at 29.5 mm from the articular surface would be extra-articular in 80% of specimens. Dissections confirmed extra-capsular osteotomy placement and preserved vascular integrity in all specimens.ConclusionInsertion of the first MTP joint capsule varies among specimens. A transverse osteotomy performed at 29.5 mm from the articular surface achieves an extra-capsular position in 80% of our specimens without compromising vascular supply to the capital fragment. These values provide reproducible intraoperative guidance.Level of Evidence(5) Clinical Research.