Cadaveric Study of the Femoral Nerve Sensory Branches: An Anatomical Guide for Saphenous Nerve Reconstruction

The majority of nerve reconstruction techniques are performed on the sciatic nerve in above-the-knee amputees. However, sensory branches in the anterior thigh are often overlooked and may contribute to postoperative pain. This study aims to provide an anatomical guide for performing targeted muscle reinnervation (TMR) in the anterior thigh to improve pain in transfemoral amputees.

This observational study was conducted on 12 formalin-fixed, well-embalmed cadaveric lower limbs. The femoral nerve was identified and dissected to isolate its anterior and posterior divisions. The saphenous nerve is the terminal branch of the posterior division of the femoral nerve, entering the adductor canal. Linear measurements were taken from the midpoint of the inguinal ligament (IL) in the direction of the medial femoral condyle. An additional proof-of-concept dissection on 2 cadaveric limbs was completed using the recorded measurements to identify the saphenous nerve and nearby motor branches.

The median distance from the IL to the saphenous branch point was 19 cm (IQR, 19.1-25.5 cm). The nerve to vastus medialis (VM) was the closest motor branch to the saphenous nerve in 83% of limbs, originating at a median distance of 17.8 cm (IQR, 15.9-21.5 cm). From the posterior division of the femoral nerves, 60% gave 2 motor branches to VM, 30% gave 3, and 10% gave 4. In 2 limbs, we observed no VM branches from the posterior division and found that the closest motor branches were to vastus intermedius (9 cm) and to the sartorius (18 cm). Proximally, branches to vastus intermedius, rectus femoris, and sartorius were highly variable. Using measurements from the 12 cadavers, the saphenous nerve and VM motor branches were found in both cadaveric limbs 16-26 cm from the inguinal crease.

Surgeons performing TMR of the saphenous nerve should explore the anterior medial thigh approximately 16-26 cm distal to the inguinal crease to reliably identify VM targets. If more proximal, motor targets are more variable, and other nerve reconstruction techniques such as regenerative peripheral nerve interfaces should be utilized.