Popliteal fossa block

An understanding of the anatomy of the popliteal fossa is essential in order to successfully block the nerves of the lower extremity below the knee. The innervation of the lower extremity originates from the lumbar and sacral plexuses. The sciatic nerve, which is formed from the sacral plexus, innervates the hamstrings and all the muscles of the lower leg and foot. With one exception, the saphenous nerve, all the sensation of the lower leg is via branches of the sciatic nerve. In the past, all techniques for blocking nerves in the popliteal fossa involved the use of a stimulating needle and a nerve stimulator to elicit a characteristic dorsi or plantar flexion in the foot. However, recently interest has centered on the use of ultrasonic guidance to facilitate the placement of regional blocks. Needle guidance and block placement with ultrasound offers the following distinct advantages over all other techniques: precise location of nerves, avoidance of major vessels or organs, direct visualization of the needle and spread of the local anesthetic solution and to make peripheral blocks possible in the morbidly obese where landmarks are obscured. This manuscript provides detailed guidance in the use of ultrasound to facilitate the placement of the popliteal fossa block.