Sciatic Nerve Block Using the Subgluteal Space Approach: A Comparison With the Infragluteal Approach
Condition: Neuromuscular Blockade
Study type: Interventional

Summary: 
      A new ultrasound-guided "subgluteal space" approach to sciatic nerve block that has been
      recently described obviates the need to identify the sciatic nerve. The investigators
      hypothesize that the use of an ultrasound-guided subgluteal space injection to perform
      sciatic nerve block will increase the proportion of patients experiencing complete sensory
      block in both terminal branches of the Sciatic nerve in comparison to the same proportion in
      those who receive the block via ultrasound-guided infragluteal approach with circumferential
      injection in patients scheduled for unilateral TKA(total knee arthroplasty) surgeries.
    

Detailed description: 
      The subgluteal space technique is performed by injecting local anesthetics in the space
      sandwiched between the gluteus maximus and biceps femoris muscle at the level of the greater
      trochanter and ischial tuberosity rather than circumferentially around the nerve. The bone
      landmarks are particularly easier to identify because of the high acoustic mismatch and
      attenuation of bone. The end point of this technique is the distention of the subgluteal
      space to injection through the block needle. This new approach may translate in benefits
      including reducing block procedure time, reducing number of needle passes, reducing side
      effects (vascular complications), and ultimately block success.

      The philosophy of injecting local anesthetics in designated anatomic spaces or between the
      fascial planes where nerves travel, as in the fascia iliaca block for example, is a time
      tested approach and has become more popular with the introduction of ultrasound because of
      the ease of visualizing fascia and bone in comparison to nerves under ultrasound. The call
      for injecting between planes and to stay away from nerves being blocked has found supporting
      evidence in trials involving ultrasound-guided brachial plexus block at the interscalene
      level.

      One important potential advantage of the subgluteal space approach may be an increased safety
      margin created when distance is maintained between injecting needles and target nerves, an
      advantage that seems to make these injection techniques progressively more popular and to
      expand into a variety of single and continuous nerve blocks.

      The investigators aim to compare the newly described ultrasound-guided subgluteal space block
      technique of the sciatic nerve to the currently practiced ultrasound-guided infragluteal
      sciatic nerve block with circumferential perineural spread in patients undergoing unilateral
      TKA surgery.
    

Intervention name(s): Infragluteal space group; Subgluteal space group
Intervention type(s): Procedure; Procedure
Intervention description(s): Sciatic Nerve Block "Infragluteal group": Ultrasound scanning will be used to identify and mark the greater trochanter laterally and the ischial tuberosity medially. The midpoint between these two structures is a rough non-binding estimate of the approximate location of the sciatic nerve. 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.; Subgluteal space group: The operator will identify the gluteus maximus and biceps femoris muscles at the level of the greater trochanter and ischial tuberosity and the infragluteal space.
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Sciatic Nerve Block; Subgluteal space; Infragluteal space