Anatomic study of the medial neurovascular structures in relation to calcaneal osteotomy

Medial displacement osteotomy of the calcaneous is commonly performed for s tage II posterior tibial tendon insufficiency in an effort to improve the v algus deformity of the hindfoot. We performed an anatomic study examining t he medial neurovascular anatomy and its relation to the osteotomy in an att empt to determine which structures may be at risk during the procedure. Calcaneal osteotomies were performed through a lateral approach on 22 fresh -frozen cadaver below-knee specimens. Dissection was then performed mediall y to identify the Medial Plantar Nerve (MPN), the Lateral Plantar Nerve (LP N), the Posterior Tibial Artery (PTA), and their respective branches. Measu rements determined either 1) where the structure crossed the osteotomy or 2 ) if the structure did not cross, the closest perpendicular distance from t he osteotomy and at which point along its length this occurred. Perpendicul ar distances were recorded in millimeters and position along the osteotomy as a percentage of the total length from the posterosuperior aspect. An average of four neurovascular structures crossed each osteotomy site (ra nge 2 to 6), most of which were branches of the LPN or the PTA. The MPN did not cross in any of the specimens studied, the LPN crossed in one specimen , and the PTA crossed in two specimens. The MPN distributed no crossing bra nches. The calcaneal sensory branch of the LPN was identified and crossed i n 86% of the cadavers at 19% (+/- 15%) along the osteotomy length. A more d istal second branch of the LPN (Baxter's nerve) was identified and crossed in 95% of the specimens at 61% (+/- 20%) along the osteotomy length. A thir d crossing branch existed in one specimen. Each PTA distributed from zero t o three branches which variably crossed the osteotomy at a point from 2% to 100% along its length. The PTA bifurcated in 77% of the specimens at 49% ( +/- 9%) along the osteotomy length. A consistent finding in every specimen was the presence of two veins accompanying the PTA with one on either side. A number of medial neurovascular structures may be at risk when perfoming a calcaneal osteotomy through a lateral approach. A minimum of two structure s crossed the osteotomy site at variable positions in this study, although most of these structures represented branches off of the LPN or the PTA, wi th the LPN and the PTA themselves crossing only infrequently. The authors r ecommend that the completion of the osteotomy through the medial calcaneal cortex be performed in a carefully controlled manner to reduce the risk of post-operative complications including pain, numbness, and hematoma formati on.