Numbness/Saphenous Nerve

Introduction

Leg numbness due to nerve damage is one of the considerable complications after anterior cruciate ligament (ACL) reconstruction using both bone–patellar tendon–bone (BPTB) and medial hamstring tendons. Such patients especially complain of uncomfortable feelings when falling on their knees. Harvesting a BPTB graft includes risks of damaging nerves and causing sensory disturbance. Pagnani et al. pointed out the risk of saphenous nerve damage by harvesting medial hamstring tendons in the region of the pes anserinus.

Many authors have reported the nerve distribution patterns of the infrapatellar regions. It is well known that both the medial cutaneous nerve of the femoral nerve and the infrapatellar branch of the saphenous nerve are distributed throughout the infrapatellar region and the anterior lower leg region. The saphenous nerve descends laterally along the femoral artery and enters the adductor canal. It then leaves the artery at the distal end of the canal to proceed vertically along the medial side of the knee and runs between the sartorius and gracilis tendons. In contrast, the medial femoral cutaneous nerve originates from the anterior cutaneous branches of the femoral nerve. The medial femoral cutaneous nerve runs laterally to the femoral artery, and then it crosses anteriorly to the artery at the apex of the femoral triangle to be distributed to the anteromedial thigh and the infrapatellar region. Branches of the medial femoral cutaneous nerve and the infrapatellar branch of the saphenous nerve connect to each other and form the subsartorial plexus in the infrapatellar region.

Bone–Tendon–Bone Autograft

Anterior knee pain including leg numbness has been reported as a main complication of ACL reconstruction using BPTB grafts. In previous reports, the rate of postoperative anterior knee pain ranged from 4% to more than 40%. Mishra et al. at first described a technique using two horizontal incisions for patellar tendon harvest for the purpose of more cosmetic scarring and reducing pain and flexion limitation. Kartus et al. used a technique with two vertical incisions and reported an insensitive area compared with the insensitive area that resulted from a traditional vertical incision, which averaged 24 cm. Tsuda et al. changed the method of approaching the retinaculum layer, opening it horizontally rather than splitting it to protect nerves using two horizontal incisions. They reported a 17% rate of postoperative leg numbness. Portland et al. compared a horizontal incision and a vertical incision and reported an infrapatellar numbness of 43% resulting from a horizontal incision and 59% resulting from a horizontal incision.