Popliteal Approach to Sciatic Nerve Block Provides Postoperative Analgesia That Is Not Inferior to That of the Infragluteal Approach in Patients Undergoing Unilateral Total Knee Arthroplasty Under Spinal Anesthesia

Sciatic nerve block provides clinically significant analgesic benefits following total knee arthroplasty (TKA). These benefits include a reduction in pain scores and decrease analgesic requirements.

Despite these benefits, sciatic nerve block has remained among the least performed peripheral nerve block by anesthesiologists. Some impediments relating to single shot sciatic nerve block (SSNB) that may cause anesthesiologists to avoid it include, patient discomfort due to needle passage through dense gluteal or thigh adipose and musculature, and unreliable success because of difficulty in localizing the sciatic nerve (particularly in obese patients).

Even in the current era of US guidance, sciatic nerve block remains a challenge. Despite its helpfulness, ultrasound technology remains hindered by an intrinsic limitation: a trade off between depth of penetration and image resolution; therefore, it works well for superficial blocks but becomes less useful when deep structures are imaged-ironically where this guidance is needed most. The challenge of anatomical depth, as in the case of the sciatic nerve, is one remaining challenge that dictates practical restrictions on the patterns of practice of ultrasound-guided regional anesthesia.

Actually, the recommendations of the Joint Committee for Education and Training composed of the American Society of Regional Anesthesia and the European Society of Regional Anesthesia cite the depth of block resulting in degradation of both ultrasound and needle image as the first among other causes that increase the level of difficulty of a nerve block.

As the sciatic nerve travels caudally in the body, it becomes more superficial with less thickness of tissue separating it from skin surface, making distal sciatic nerve block an attractive alternative. Indeed, both articular branches which provide sensory innervation to the knee joint as well as its muscular branches which provide innervation to the muscles surrounding knee joint most commonly arise from the sciatic nerve either at the knee level, or just above the knee or within the popliteal fossa.