Ultrasound Assessment of Infrapatellar and Sartorial Branches of the Saphenous Nerve: Establishing a Safety Zone for Preventing Nerve Injury in Knee Surgery and Injections

Abstract Purpose Our study aimed to illustrate the positional relationship of the two branches of the saphenous nerve: the infrapatellar branch of the saphenous nerve (IPBSN) and sartorial branch of the saphenous nerve (SBSN), as well as the anatomical landmarks using high-resolution ultrasound (HRUS) to help prevent iatrogenic nerve injury. Methods We used HRUS to explore the positional relationships among the anatomical landmarks, IPBSN, and SBSN in 40 knees of 20 participants. The distances from these branches to key reference points were recorded. Using the ultrasound caliper mode, we measured the depth from the skin surface to the nerves at four distinct points. Results The average distances between IPBSN and medial border of patella (MBP) and IPBSN and medial border of patellar ligament (MBPL) were 47 ± 7 mm and 42 ± 9 mm, respectively. SBSN showed mean distances of 94 ± 9 mm and 96 ± 9 mm to MBP and MBPL, respectively. The mean distance from the upper edge of pes anserine to IPBSN at the patellar apex (PA) level was 24 ± 10 mm and to SBSN was 34 ± 9 mm. Conclusion We used high-resolution ultrasound to evaluate IPBSN and SBSN and their positions relative to anatomical landmarks. The study results offer valuable insights into the course of these nerves, which can help establish a safety zone to prevent accidental nerve injuries during knee surgeries and injections.