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 degrees 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.

Retropatellar Accessory Portals for Improved Access to the Patella; Anatomic Description and Evaluation of Safety

“…Finding consistency within IPBSN branching has been the aim of many studies since. 2,9,14,16,18,34 Despite our relatively small sample size of 10 cadaveric knees, the relationship between the IPBSN and bony landmarks was no different than those reported in the large seminal study by Mochida and Kikuchi. 24 In their study of 129 knees, these authors reported an insignificant difference in the mean distance from the IPBSN to the midpatella in left (52.2 mm) and right (54.2 mm) knees.…”

“…1,8,12,28,33,34 Our clinical study of 109 patients revealed no such complications. Our anatomic study showed that the medial and lateral epicondyles can serve as dependable landmarks for portal placement (± 4.7 mm and ± 3.8 mm, respectively).…”

Injury to the Lateral Femoral Cutaneous Nerve During Minimally Invasive Hip Surgery: A Cadaver Study

“…1 From the results presented here, division of cutaneous nerve branches is common in the SLA and the PA. Studies have reported better patient outcome following knee arthroscopy and arthroscopic ACL reconstruction when the incision lines are placed horizontally (parallel to the infragenicular branch of the saphenous nerve) rather than vertically, across the path of the nerve. 12 Similarly, symptoms (pain and numbness) after harvesting of bone from the posterior iliac crest are reduced when incisions are made parallel to the nerves, rather than perpendicular to them. 13 There is conflicting evidence for the benefits of MIS in the literature.…”

“…All the cadavers used had been embalmed; the position of the hip at rigor mortis may have influenced the position of cutaneous nerves. However, unlike nerves around the knee where joint movement can influence nerve position markedly, 12 the hip position during dissection was similar to the intra-operative position at the time of skin incision for THA. There is also a risk of inter-observer bias as the dissections were performed by two of the authors independently.…”

“…[8][9][10] Surgical incisions aligned parallel to cutaneous nerves reduce sensory disturbance following knee arthroscopy and iliac crest bone graft harvesting. [11][12][13] Should skin incisions for THA aim to preserve cutaneous nerves in order to reduce troublesome symptoms, and improve rehabilitation and patient satisfaction?…”