The surgical anatomy of the infrapatellar branch of the saphenous nerve in relation to incisions for anteromedial knee surgery.

BACKGROUND: Iatrogenic injury to the infrapatellar branch of the saphenous nerve is a common complication of surgical approaches to the anteromedial side of the knee. A detailed description of the relative anatomic course of the nerve is important to define clinical guidelines and minimize iatrogenic damage during anterior knee surgery. METHODS: In twenty embalmed knees, the infrapatellar branch of the saphenous nerve was dissected. With use of a computer-assisted surgical anatomy mapping tool, safe and risk zones, as well as the location-dependent direction of the nerve, were calculated. RESULTS: The location of the infrapatellar branch of the saphenous nerve is highly variable, and no definite safe zone could be identified. The infrapatellar branch runs in neither a purely horizontal nor a vertical course. The course of the branch is location-dependent. Medially, it runs a nearly vertical course; medial to the patellar tendon, it has a -45° distal-lateral course; and on the patella and patellar tendon, it runs a close to horizontal-lateral course. Three low risk zones for iatrogenic nerve injury were identified: one is on the medial side of the knee, at the level of the tibial tuberosity, where a -45° oblique incision is least prone to damage the nerves, and two zones are located medial to the patellar apex (cranial and caudal), where close to horizontal incisions are least prone to damage the nerves. CONCLUSIONS: The infrapatellar branch of the saphenous nerve is at risk for iatrogenic damage in anteromedial knee surgery, especially when longitudinal incisions are made. There are three low risk zones for a safer anterior approach to the knee. The direction of the infrapatellar branch of the saphenous nerve is location-dependent. To minimize iatrogenic damage to the nerve, the direction of incisions should be parallel to the direction of the nerve when technically possible. CLINICAL RELEVANCE: These findings suggest that iatrogenic damage of the infrapatellar branch of the saphenous nerve can be minimized in anteromedial knee surgery when both the location and the location-dependent direction of the nerve are considered when making the skin incision.

Injury to the infrapatellar branch of the saphenous nerve, a possible cause for anterior knee pain after tibial nailing?

The purpose of this study was to determine the long-term incidence of infrapatellar nerve damage after tibial nailing and its relation to anterior knee pain. We retrospectively evaluated 71 patients in whom 72 isolated tibial shaft fractures were treated with an intramedullary nail. The mean follow-up time was 84 months. Twenty-seven patients (38%) complained of chronic anterior knee pain. Infrapatellar nerve damage was found in 43 patients (60%). Of the 27 patients with knee pain, 21 (78%) had sensory deficits in the distribution area of the infrapatellar nerve, compared to 22 of the 45 patients (49%) without knee pain (p=0.025). Patient and fracture characteristics showed no significant differences between the two groups. At time of follow-up a total of 33 nails were removed of which twelve were taken out because of knee pain. The pain persisted in seven of these twelve patients (58%). The incidence of iatrogenic damage to the infrapatellar nerve after tibial nailing is high and lasting. Injury to this nerve appears to be associated with anterior knee pain after tibial nailing.