The Relationship of the Infrapatellar Branches of the Saphenous Nerve to Arthroscopy Portals and Incisions for Anterior Cruciate Ligament Surgery: An Anatomic Study

Abstract

The purposes of this study were 1) to carefully define the anatomic distribution of the infrapatellar branches of the saphenous nerve, 2) to provide the surgeon with reliable parameters for where the nerve is most commonly encountered, and 3) to provide specific surgical recommendations to minimize the risk of nerve injury. To accomplish these goals, we dissected 20 cadaveric, fresh-frozen, matched-pair knees. Calipers were used to measure the distance from the nerve to three clinically relevant and easily reproducible landmarks: the inferior pole of the patella, the medial border of the patella at its midpoint, and a point 2 cm medial to the patellar ligament at the level of the joint line. Distances were recorded with the knees in extension and in 90° of flexion to examine the effect of dynamic knee motion on nerve position. We consistently found two main trunks of the nerve that traverse the knee primarily in a medial to lateral but somewhat proximal to distal direction. Because of this, we recommend that incisions for arthroscopy portals be made in a horizontal fashion to decrease the likelihood of nerve injury. Measured from both the inferior pole of the patella and the medial border of the patella, the nerve moved distally with knee flexion. We therefore recommend that incisions across the anterior aspect of the knee be made with the knee in flexion. In 8 of our 20 specimens, the nerve was actually found at the landmark located 2 cm medial to the patellar ligament. This is an extremely high-risk area and should be avoided if possible.