Fig 3.

Four US-guided approaches to the SN (parasacral, subgluteal, anterior, and popliteal). Each approach includes the US transducer position, angle of needle insertion, original US image, and coloured US image highlighting the key anatomy relevant to performing the block. Parasacral: gmm, gluteus maximus muscle; gsf, greater sciatic foramen; pm, piriformis muscle; sp, sacral plexus. Subgluteal: bfm, biceps femoris muscle; gt, greater trochanter; it, ischial tuberosity; qfm, quadratus femoris muscle; sn, sciatic nerve; tosm, tendon of semimembranosus muscle. Anterior: abm, adductor brevis muscle; alm, adductor longus muscle; amm, adductor magnus muscle; bf/st, biceps femoris/semitendinosus; sfa, superficial femoral artery; sm, sartorius muscle; sn, sciatic nerve; vmm, vastus medialis muscle. Popliteal: bfm, biceps femoris muscle; blue dotted line, common paraneural sheath; cpn, common peroneal nerve; smm, semimembranosus muscle; stm, semitendinosus muscle; tn, tibial nerve; X, space within common paraneural sheath.