The course and distribution of the infra patellar nerve in relation to ACL reconstruction

A common complication after ACL (anterior cruciate ligament reconstruction) is injury to the infra-patellar branch of the saphenous nerve (IPBSN). Very little about its origin and course of this nerve has been described. The aim of this study was to understand the course of IPBSN in relation to surgery around the knee.

The course of the nerve was dissected and traced in 25 knees from 14 cadaveric knees (10 males; four females). An incision was made posterior to the medial condyle of the tibia and continued deeper towards the saphenous nerve which is located under the sartorius muscle. The saphenous nerve branch was then followed to distally supply the anterior leg (IPBSN). The relationship of saphenous nerve and IPBSN to each other and the hamstrings were recorded.

Four paths of IPBSN, in relation to the sartorius muscle, were identified: (1) posterior--inferior posterior border of the muscle, (2) transmuscular--penetrating through the muscle, (3) anterior--anterior border of the muscle, (4) posterior patellar--posterior of the muscle at the level of the patellar bone and (5) combined. The posterior pathway of IPSBN was the most common (57%) and had the closest proximity to the tendons of semitendinosus and gracilis muscles. The terminal branches of the IPSBN crossed over the patellar tendon in every dissection.

A posterior path IPBSN is more prone to damage during a tendon harvest due to its proximity to the gracilis and semitendinosus muscle tendons.