Introduction: During the design of minimally invasive surgeries (MIS) carried out on the third toe of the foot, it is important to know the position of the nutrient foramen in the third metatarsal shaft and/or proximal phalanx to prevent complications such as avascular necrosis or delays in consolidation further to corrective osteotomies carried out to treat certain conditions that affect the third toe in toe-to-hand surgical transposition. Our aim was to determine the location of the main nutrient foramen of the third metatarsal and/or proximal phalange providing a mathematical method to accurately locate it prior to surgery.

Materials and methods: We studied 70 third metatarsals and proximal phalanges of the third toe from surgically amputated lower limbs. We established the position of the nutrient foramen in both normal feet and those with forefoot pathological conditions by means of the nutrient index and the distance from the nutrient foramen to the base and the distal cartilage border and, for the third metatarsal, also to the dorsal aspect.

Results: The most frequent location of the nutrient foramen was the middle third of the shaft on the plantar aspect of both bones, and in the majority it was the only location. The distance from the nutrient foramina to each base was significantly correlated with their total length and physiology; we provide the corresponding predictive equations with regression lines.

Conclusions: We propose predictive equations of the distance of the NF from the base of both bones based on their total lengths. This distance can be determined by somatic measurement or by means of conventional dorso-plantar x-rays without contrast medium.