The proximity of the medial soft tissue structures to a posterior calcaneal osteotomy (PCO) was examined to determine which structures are at risk of injury.

A PCO was performed on 12 adult frozen cadaver feet. At the lateral side of each specimen, the inclination of the osteotomy line was 45° to the plantar aspect of the foot and its proximal end was began approximately 10 mm anterior to the posterosuperior corner of the calcaneus. Two different PCOs were made in order to include any variations in the osteotomy. Using a guide device to direct the osteotomy, the PCOs were performed 10° anteromedially in half of the specimens and 10° posteromedially in the other half. The medial side of the hindfoot was carefully dissected after the PCO had been fixated with K-wires.

The most inferior portion of the osteotomy was 8.1 mm anterior to the inferior tubercle. The structures found closest to the osteotomy on the medial side were the medial head of the quadratus plantae (QP) and the branches of the lateral plantar nerve (LPN). In both osteotomies, the nerve to the abductor digiti quinti (ADQ) and calcaneal branch of the LPN crossed the osteotomy site. The thickness of the soft tissue coverage at the crossing site medially averaged 2.3 mm at the nerve to the ADQ and 5.9 mm for the calcaneal branch. In all specimens, the soft tissue coverage was thinner at the more inferior aspect of the osteotomy. No major neurovascular structures, such as the medial and lateral plantar arteries and nerves, crossed the osteotomy site.

In the PCO, the structure most at risk is the medial head of the QP and the nerve to the ADQ, which is followed by the calcaneal branch of the LPN. Care should be taken for these nerve injuries, particularly at the inferior portion of the osteotomy due to the thinner coverage of the intervening soft tissue. The PCO can be safely carried out without involving the major neurovascular bundle of the foot, when the inclination of osteotomy line is 45° to the plantar aspect and its proximal end begins within 10 mm anterior to the posterosuperior corner of the lateral side of the calcaneus.