Popliteal Approach to Sciatic Nerve Block Is Not Inferior to Infragluteal Approach
Condition: Neuromuscular Blockade
Study type: Interventional

Summary: 
      Study Hypothesis The investigators approach to demonstrate noninferiority of analgesia
      provided by popliteal block in TKA surgery will be based on a hypothesis of absence of a
      clinically significant difference in pain visual analogue sores (VAS) between the analgesia
      provided by the popliteal block and that of the infragluteal sciatic block in TKA surgery
      patients.
    

Detailed description: 
      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.

      Blockade of the sciatic nerve at the level of the popliteal fossa, commonly termed a
      popliteal block, is technically easier to perform than gluteal sciatic block and may even be
      associated with less risk of intravascular injection and nerve injury. Indeed, popliteal
      block has been reported to provide good postoperative analgesia in total knee replacement and
      other major knee surgery. However, the small posterior cutaneous nerve of the thigh, which
      supplies only the skin on the back of the thigh and knee, separates from the sciatic nerve
      proximally and variably in the gluteal region, and will be spared in more distal approaches.
      It is for this reason why many practitioners are hesitant to perform distal sciatic nerve
      blocks for TKA. However, the relative importance of the posterior cutaneous nerve of the
      thigh for post-operative analgesia following TKA is unknown and maybe clinically
      insignificant.
    

Intervention name(s): Popliteal approach; Infragluteal approach
Intervention type(s): Procedure; Procedure
Intervention description(s): Popliteal approach:
Under ultrasound guidance a 50 to 90 mm 22 G needle is inserted in and advanced to contact the target nerve until nerve movement is detected. The end point of nerve block in this group is obtaining a circumferential local anesthetic spread around the sciatic nerve.; Infragluteal approach: The patients in this group will receive sciatic bock according to the approach described by Chan et al. Ultrasound scanning will be used to identify and mark the greater trochanter laterally and the ischial tuberosity medially. The sciatic nerve is usually found anterior (deep) to the gluteus maximus muscle and lateral to the origin of the biceps femoris muscle at the ischial tuberosity as well as medial to the greater trochanter. The end point of nerve block in this group is obtaining a circumferential local anesthetic spread around the sciatic nerve.
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: sciatic nerve block; infragluteal approach; popliteal approach