The Spread of Ultrasound-Guided Injectate from the Adductor Canal to the Genicular Branch of the Posterior Obturator Nerve and the Popliteal Plexus: A Cadaveric Study

Background and Objectives The popliteal nerve plexus contributes to afferent knee-pain conduction. It is mainly formed by genicular branches from the posterior obturator and the tibial nerves, innervating the intra-articular and posterior knee region. A subinguinal obturator nerve block alleviates pain after total knee arthroplasty. Reduced hip adductor motor function could be avoided by a posterior obturator nerve block inside the popliteal fossa. The aim of this study was to evaluate the spread of dye after a distal adductor canal (AC) injection to the popliteal fossa and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve by dissection. We also assessed the spread of dye into the popliteal fossa after a distal femoral triangle injection. Methods Ten milliliters of dye was injected into the distal part of the AC in 10 cadaver sides and into the distal part of the femoral triangle in 3 sides. Dissection was used to assess the spread of the injectate and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve, as well as the saphenous and medial vastus nerves. Results The popliteal plexus and the genicular branch of the posterior obturator nerve were dyed in all 10 dissections after AC injections. No dye spread into the popliteal fossa after femoral triangle injections. Conclusions Injection of 10 mL of dye into the distal part of the AC spreads into the popliteal fossa and colors the popliteal plexus and the genicular branch of the posterior obturator nerve.