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Subtle Differences between Ultrasound Guided Subgluteal Sciatic Nerve Block at the Subgluteal Space
- M.K. Karmakar, W.H.Kwok, A.M.Ho, K.Tsang, P.T.Chui, T.Gin (10 June 2007)
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Ultrasound-guided Subgluteal Sciatic nerve block
- Sherif Abbas, Richard Brull (29 May 2007)
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Ultrasound-guided sciatic nerve block: description of a new approach at the subgluteal space
- Shiv k Singh, S Seppi (30 March 2007)
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M.K. Karmakar , W.H.Kwok, A.M.Ho, K.Tsang, P.T.Chui, T.Gin
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Editor, We thank Dr. Abbas and Brull for their interest in our recent article.1 They suggest that we have reported on a technique that their group has previously described.2 We respectfully disagree with their assertion and would like to offer the following explanation to substantiate our claims. In the article that Abbas and Brull refer to,2 but is misquoted in their correspondence, Chan et al. describe the sonoanatomy of the sciatic nerve and a technique of performing ultrasound guided sciatic nerve injection at the infragluteal location in volunteers.2 By definition, “infragluteal” is inferior to the gluteal crease.3 Therefore an infragluteal injection for sciatic nerve block is performed inferior to a line joining the greater trochanter and the ischial tuberosity.3,4 Figure 1B in the article by Chan et al. illustrates the location at which the infragluteal ultrasound scan and injection is performed.2 In the technique that we describe the ultrasound scan and needle insertion is performed above the gluteal crease and directly over a line joining the lateral prominence of the greater trochanter and the ischial tuberosity.1 Although the two techniques may appear similar, because they are both “subgluteal” injections, i.e. under the gluteus maximus, and both injections are made in relation to the greater trochanter and the ischial tuberosity, there are subtle anatomical differences that make these two techniques different. In the technique that we describe the “subgluteal space”, which is a well defined anatomical space and contains the sciatic nerve,1 is initially identified on the ultrasound image as a hypoechoeic area between the hyperechoeic perimysium of the gluteus maximus and the quadratus femoris muscle.1 Distention of the subgluteal space to a test injection of saline through the block needle is then confirmed – “our end point”, irrespective of whether a motor response to nerve stimulation is elicited in the foot or not, before the local anaesthetic is injected.1 In contrast, Chan et al. perform their ultrasound guided subgluteal injection in the infragluteal position after identifying the sciatic nerve using nerve stimulation.2 There is no mention by Chan et al. as to whether they were able to identify a potential perineural space on the ultrasound image of the infragluteal area prior to the local anaesthetic injection although they report enlargement of the space after the injection.2 We were able to identify pulsations of the inferior gluteal artery medial to the sciatic nerve in the “subgluteal space”1 while Chan et al. were unable to identify any blood vessel in the vicinity of their injection2 confirming that our two techniques were performed at different locations. Moreover, local anaesthetic also spreads between different muscles in the two techniques. In our technique the local anaesthetic spread between the gluteus maximus and the quadratus femoris muscle.1 In comparison, in the infragluteal technique it spreads between the gluteus maximus and biceps femoris muscle posteriorly5 and the adductor magnus muscle anteriorly. We agree that the above discussion should have been included in our report and hope that it will help clarify the differences between our technique1 and the technique of ultrasound guided subgluteal sciatic nerve block at the infragluteal position.2 References 1. Karmakar MK, Kwok WH, Ho AM, Tsang K, Chui PT, Gin T. Ultrasound- guided sciatic nerve block: description of a new approach at the subgluteal space. Br J Anaesth 2007; 98: 390-5. 2. Chan VW, Nova H, Abbas S, McCartney CJ, Perlas A, Xu dQ. Ultrasound examination and localization of the sciatic nerve: a volunteer study. Anesthesiology 2006; 104: 309-14. 3. Franco CD, Tyler SG. Modified subgluteal approach to the sciatic nerve. Anesth Analg 2003; 97: 1197. 4. Sukhani R, Candido KD, Doty R, Jr., Yaghmour E, McCarthy RJ. Infragluteal-parabiceps sciatic nerve block: an evaluation of a novel approach using a single-injection technique. Anesth Analg 2003; 96: 868- 73. 5. Gray AT, Collins AB, Schafhalter-Zoppoth I. Sciatic nerve block in a child: a sonographic approach. Anesth Analg 2003; 97: 1300-2. Conflict of Interest:None declared |
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Sherif Abbas , Richard Brull
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To the Editor: We read with interest the recent manuscript entitled “Ultrasound- guided sciatic nerve block: description of a new approach at the subgluteal space”, By Karmakar and colleagues1, that appeared in the March 2007 issue of the Journal. We are pleased to learn that our previously described technique2 has gained popularity in other centers worldwide. The standard of care at Toronto Western Hospital for patients undergoing total knee arthroplasty is continuous catheter-based femoral nerve block, single shot sciatic nerve block and a spinal anesthetic. Since 2005, we have performed a total of 675 sciatic nerve blocks, of which 207 were done using our ultrasound guided subgluteal approach2. We have found excellent reliability with no reported complications. Karmakar and colleagues have provided a well written detailed description of their experience with the ultrasound guided subgluteal sciatic nerve blockade, however given the similarity with our previously described subgluteal technique, we were disappointed to find no mention of our endeavors. 1) Karmakar M. K., Kwok W. H., Ho A. M., Tsang K., Chui P. T., and Gin T. Ultrasound-guided sciatic nerve block: description of a new approach at the subgluteal space. Br J Anaesth. 2007; 98 (3):390-5. 2) Chan VW, Brull R, McCartney CJ, Xu D, Abbas S, Shannon P. Ultrasound Examination and Localization of the Sciatic Nerve, Anesthesiology 2006; 104:309–14 Conflict of Interest:None declared |
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Shiv k Singh , S Seppi
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Editor- We read the description of the ultrasound-guided sciatic nerve block at subgluteal region with great interest. The technique is very well described but then we couldnot find any difference in the approach that is described by dabu and Chan in "A Practical Guide to Ultrasound Imaging for Peripheral Nerve Blocks" (1). A brief mention of the approach can also be found in the review article "Current practice of ultrasound-assisted regional anesthesia". by Popovic et al(2). The approach is also taught at the various ultrasound guided nerve blocks in UK. I would think that the authors probably are not aware of the publications and in this case the approach is not as new as the authors suggest. Dabu A, Chan VWS. A Practical Guide to Ultrasound Imaging for Peripheral Nerve Blocks. Toronto: University of Toronto; 2004: http://www.usra.ca/ultrasound_ guided_peripheral_nerve_blocks. Popovic J; Morimoto M; Wambold D; Blanck TJJ; Rosenberg AD. "Current practice of ultrasound-assisted regional anesthesia". Pain practice. 2006; 6: 127 (#J0115043) Conflict of Interest:None declared |
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