Sensory conduction study of the infrapatellar branch of the saphenous nerve.

Although neuropathies of the infrapatellar nerve (infrapatellar branch of the saphenous nerve, IPBSN) have been reported clinically, no electrophysiological method has been defined to evaluate IPBSN conduction. We therefore studied a total of 60 saphenous nerves and 60 IPBSNs from 36 volunteers. The IPBSN was stimulated medially with a surface electrode 2 cm below the patella. The response was recorded with a needle electrode located close to the nerve 1 cm lateral to the femoral artery in the inguinal region. Sensory nerve action potentials were obtained from each subject; mean latency of the first positive peak was 8.1 +/- 0.9 ms, conduction velocity was 54 +/- 4.4 m/s, and response amplitude was 1.3 +/- 1.1 microV. The method that we describe may be an easy and useful electrophysiological test for neuropathies of the IPBSN.