Dorsiflexory Wedge First Metatarsal Osteotomy: Does an Oblique Cut Increase Surface Area?

CATEGORY: Ankle INTRODUCTION/PURPOSE: A plantarflexed first metatarsal can contribute to a forefoot driven cavus foot deformity or result in plantar ulcerations from forefoot pressure overload in a neuropathic patient. Often, this deformity is managed via a dorsiflexon first metatarsal base osteotomy. This osteotomy is often described as a vertical wedge, with a dorsal base, in the proximal metatarsal. Alternatively we propose an oblique wedge, which may also allow for increased surface area for osseous healing to occur, in addition to being more theoretically stable to weightbearing with greater fixation options. METHODS: Ten cadaveric below-knee specimens were randomized into an oblique wedge (5 specimens) and vertical wedge (5 specimens) groups. The osteotomies were performed by a single surgeon on the same date. Digital calipers were utilized to obtain measurements to calculate surface area for each osteotomy. Demographic data including patient age at death, height, weight, BMI, sex, and laterality were obtained. RESULTS: The mean surface area of the proximal metatarsal for the vertical group was 298.2±76.5 mm2, whereas the oblique group was significantly larger at 538.6 ± 200.4 mm2 (CI 95%, p=0.0255). Similarily, but not to significance the distal side of the osteotomy demonstrated increased surface area for the oblique group with 397.8±191.4 mm2 compared to the vertical group with 265.8±75.3 mm2 (CI 95%, p=0.13. The groups were demographically similar, including height (CI 95%, p=0.62) and BMI (CI 95%, p=0.19). CONCLUSION: Our results demonstrate significantly greater surface area for the oblique dorsiflexory wedge first metatarsal osteotomy, compared to the vertical dorsiflexory wedge first metatarsal osteotomy. Further analysis is recommended for large cohort head-to-head clinical comparison of these techniques with consideration for cost effectiveness of fixation constructs, procedural complications and patient reported clinical outcome measures.