Letters to the Editor
REFERENCES 1. Mulroy MF, Weller RS, Liguori G. A checklist for performing regional nerve blocks. Reg Anesth Pain Med. 2014;39:195–199. 2. Haynes AB, Weiser TG, Berry WR, et al. A surgical safety checklist to reduce morbidity and mortality in a global population. N Engl J Med. 2009;360:491–499. 3. Universal Protocol 2010, The Joint Commission; Universal protocol for preventing wrong site, wrong procedure, wrong person surgery. http://www.jointcommission.org/standards_information/ up.aspx. Accessed January 13, 2014. 4. Simmons H, Brits R. Survey of wrong site regional anaesthetics. Department of Anaesthetics, East Lancashire Hospitals NHS Trust, Lancashire. http://www.rcoa.ac.uk/sites/ default/files/CSQ-PS-WSB-BritsSimmons2011.pdf. Updated May 19, 2011. Accessed January 2, 2014. 5. Lie J, Naylor K. A questionnaire on the prevention of wrong-sided nerve blocks in the North Western Deanery. Abstracts and Highlight Papers of the 32nd Annual European Society of Regional Anaesthesia and Pain Therapy (ESRA) Congress 2013 Posters: Posters. Reg Anesth Pain Med. 2013;38:E217. 6. Stanton MA, Tong-Ngork S, Liguori GA, Edmonds CR. A new approach to preanaesthetic site verification after 2 cases of wrong site peripheral nerve block. Reg Anesth Pain Med. 2008;33:174–177.
Regional Anesthesia and Pain Medicine • Volume 39, Number 5, September-October 2014
(AC). We disagree. The caudad end of the AC is typically 10 cm proximal to the adductor tubercle which is at the level of the base of the patella. The length of the AC is approximately 8 cm as previously described by Tubbs et al.3 Thus, the needle insertion point of the ACB as suggested by Jæger et al1 would be proximal to the AC in a normal adult (Fig. 1) and local anesthetic injected here is subsartorial at the level of the femoral triangle (FT). This is clinically important because even with 30 mL of local anesthetic, the injectate cannot be expected to spread reliably distal throughout the AC. This is confirmed by the solitary MR T2-weighted image provided by Jæger et al1 in their reply to our letter. The coronal plane inlet in their figure shows that local anesthetic spreads only a few centimeters from the needle insertion point. Of course, one image from an arbitrary patient is not a final proof, as also acknowledged by Jæger et al. We are not quite sure what kind of MR sequence the term “turbo inversion recovery magnitude” refers to, but we assume it is a STIR sequence, which we agree can be combined with T1- and T2weighted sequences to discriminate safely between fat, muscle, and water. The now presented T2-weighted image from another patient apparently allows discrimination between water and fat. But the problem
remains as displayed by the MR image published in the original paper that T2weighted images do not always allow “safe” discrimination between water and fat. Accordingly, it would have been pertinent if Jæger et al had shown the other MRI sequences of the patient presented in the original paper to substantiate their point. It is clinically relevant that the local anesthetic does not spread throughout the AC after ACB. The ACB by Jæger et al is merely a subsartorial saphenous nerve block at the level of the FT. The saphenous nerve is the one and only nerve consistently present within the AC. The knee joint is innervated by the femoral nerve through the 3 vasti branches and the saphenous nerve, and also by the posterior branch of the obturator nerve and the genicular branches from the tibial and common peroneal branches of the sciatic nerve. The posterior obturator nerve descends outside the AC.4 Sometimes, branches from the posterior obturator nerve accompany the femoral artery through the adductor hiatus.4 But even in those patients, the posterior obturator branch is not consistently anesthetized by local anesthetic spread with the ACB technique described by Jæger et al.1 Jæger et al1 have eloquently documented that the ACB is equivalent to a
Redefining the Adductor Canal Block Accepted for publication: May 24, 2014.
To the Editor: e want to thank Jæger and colleagues1 for responding to our concerns about the so-called adductor canal block (ACB).2 However, some important issues require further clarification. Jæger et al1 state that the anatomical basis of the ACB has academic interest but limited clinical relevance. Because we agree with Alon Winnie that “regional anesthesia is simply an excercise of applied anatomy,” we believe that it is highly relevant to discuss and understand the anatomical basis of ACB. The needle insertion point for the ACB as defined by Jæger et al1—and in past publications by the same research group—is the midpoint between the anterior superior iliac spine and the base of the patella. Jæger et al1 insist that this point is per definition within the adductor canal
W
442
FIGURE 1. The photographs show a cadaver limb from a man (A) and a woman (B). The distance from the base of patella (red) to the anterior superior iliac spine (blue) is 50 cm in the male limb and 44 cm in the female limb. The midpoint (cyan) is 25 cm proximal to the base of the patella in the male and 22 cm in the female limb. The midpoint is approximately 9 cm from the upper margin (magenta) of the AC in the male and 7.5 cm in the female limb. The distance from the lower border of the greater trochanter (green) to the base of patella (red) is 32 cm in the male and 29 cm in the female limb, and the midpoint (yellow) is at the level of the AC. © 2014 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 39, Number 5, September-October 2014
Letters to the Editor
Another clarification is required for the statement of Jæger et al1 that “the AC is roofed by the sartorius muscle and the underlying fascia.” First, the sartorius muscle is not the roof of the AC. The muscle lies on the roof of the AC. Second, the roof itself is built by the vastoadductor membrane which is not a fascia.6 This is relevant because sonographically membranes, aponeuroses, ligaments, intramuscular septae, and tracts are typically doublelayered hyperechoic structures, whereas fascia has 1 layer. It is also clinically important that the subsartorial plexus is located outside the AC and sandwiched between the vastoadductor membrane and the sartorius muscle. The subsartorial plexus receives branches from the saphenous nerve, the medial cutaneous femoral nerve, and the anterior division of the obturator nerve. It innervates the skin of the medial side of the thigh. Thus, the subsartorial plexus is not anesthetized even by a true ACB. In conclusion, the technique of ACB as described by Jæger et al1 is a subsartorial saphenous nerve block at the level of the FT, not an ACB, and it cannot be expected to reliably block the posterior branch of the obturator nerve by spread through the adductor hiatus. That would require a true ACB, which was described by Manickam et al7 in 2009. In our opinion, the simplest and most effective way to block both the saphenous nerve and the posterior branch of the obturator nerve consistently is to use 2 selective small volume blocks. However, only few studies demonstrate the need for obturator nerve block after TKA and further research is mandated to clarify this.
Histology and Embryology Innsbruck Medical University Innsbruck, Austria
femoral nerve block for analgesia after total knee replacement (TKA) with preserved quadriceps strength. A possible explanation is that the vasti branches are not clinically important for post-TKA analgesia. Jæger et al1 are probably correct to state that analgesia after TKA is improved when a subsartorial saphenous nerve block is combined with a posterior obturator nerve block. As explained, the ACB technique of Jæger el al does not achieve this. However, posterior obturator nerve block can be achieved by ultrasoundguided blockade of either the common obturator nerve or the posterior branch in the subinguinal region just as easy as the subsartorial saphenous nerve block. It is surprising that the authors dismiss the block combination of the saphenous and obturator nerves based on concerns about risks of complications and difficulty of performance. Most regional anesthetists who work clinically with regional anesthesia techniques on a daily basis would categorize these blocks as basic level. Instead, Jæger et al1 recommend a technique that defeats its own purpose of dual nerve blockade combined with insertion of a catheter into the AC which is indeed an advanced level procedure associated with a higher risk of complications. Also, the frequency of secondary displacement of AC catheters inserted in-plane across the short axis of the saphenous nerve is very high, making catheter insertion redundant (unpublished data). Much confusion is stirred up by the phrase “midthigh,” which can have different definitions. This probably explains misinterpretation by Jæger et al1 for the term “midthigh” as stated in a recently published article by Børglum et al5 and in Gray’s anatomy. It is only correct to state that the AC is located in the midthigh when the “midthigh” is defined by the middle one third of the distance from the base of the patella to the lower border of the greater trochanter. The distance from the base of the patella to the lower border of the greater trochanter is approximately 30 cm in a normal adult (Fig. 1).
Thomas Fichtner Bendtsen, MD, PhD Department of Anesthesiology and Intensive Care Medicine, Aarhus University Hospital, Aarhus, Denmark
Bernhard Moriggl, MD, PhD Division of Clinical and Functional Anatomy Department of Anatomy
© 2014 American Society of Regional Anesthesia and Pain Medicine
Vincent Chan, MD Department of Anesthesia University of Toronto Toronto, Ontario, Canada Department of Anesthesia Toronto Western Hospital Toronto, Ontario, Canada
Erik Morre Pedersen, MD, DMSc Department of Radiology, Aarhus University Hospital, Aarhus, Denmark
Jens Børglum, MD, PhD Department of Anesthesia and Intensive Care Medicine, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
The authors declare no conflict of interest.
REFERENCES 1. Jæger P, Lund J, Jenstrup MT, Brøndum V, Dahl JB. Reply to Dr Bendtsen. Reg Anesth Pain Med. 2014;39:254–255. 2. Bendtsen TF, Moriggl B, Chan V, Pedersen EM, Børglum J. Defining adductor canal block. Reg Anesth Pain Med. 2014;39:253–254. 3. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surg Radiol Anat. 2007;29:569–573. 4. Kumka M. Critical sites of entrapment of the posterior division of the obturator nerve: anatomical considerations. J Can Chiropr Assoc. 2010;54:33–42. 5. Børglum J, Johansen K, Christensen MD, et al. Ultrasound-guided single-penetration dual-injection block for leg and foot surgery: a prospective, randomized, double-blind study. Reg Anesth Pain Med. 2014;39:18–25. 6. Terminologia Anatomica. FCAT—Federative Committee on Anatomical Terminology. 1998, Thieme, Stuttgart, New York. 7. Manickam B, Perlas A, Duggan E, Brull R, Chan VW, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the saphenous nerve in the AC. Reg Anesth Pain Med. 2009;34:578–580.
443
Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
REFERENCES 1. Mulroy MF, Weller RS, Liguori G. A checklist for performing regional nerve blocks. Reg Anesth Pain Med. 2014;39:195–199. 2. Haynes AB, Weiser TG, Berry WR, et al. A surgical safety checklist to reduce morbidity and mortality in a global population. N Engl J Med. 2009;360:491–499. 3. Universal Protocol 2010, The Joint Commission; Universal protocol for preventing wrong site, wrong procedure, wrong person surgery. http://www.jointcommission.org/standards_information/ up.aspx. Accessed January 13, 2014. 4. Simmons H, Brits R. Survey of wrong site regional anaesthetics. Department of Anaesthetics, East Lancashire Hospitals NHS Trust, Lancashire. http://www.rcoa.ac.uk/sites/ default/files/CSQ-PS-WSB-BritsSimmons2011.pdf. Updated May 19, 2011. Accessed January 2, 2014. 5. Lie J, Naylor K. A questionnaire on the prevention of wrong-sided nerve blocks in the North Western Deanery. Abstracts and Highlight Papers of the 32nd Annual European Society of Regional Anaesthesia and Pain Therapy (ESRA) Congress 2013 Posters: Posters. Reg Anesth Pain Med. 2013;38:E217. 6. Stanton MA, Tong-Ngork S, Liguori GA, Edmonds CR. A new approach to preanaesthetic site verification after 2 cases of wrong site peripheral nerve block. Reg Anesth Pain Med. 2008;33:174–177.
Regional Anesthesia and Pain Medicine • Volume 39, Number 5, September-October 2014
(AC). We disagree. The caudad end of the AC is typically 10 cm proximal to the adductor tubercle which is at the level of the base of the patella. The length of the AC is approximately 8 cm as previously described by Tubbs et al.3 Thus, the needle insertion point of the ACB as suggested by Jæger et al1 would be proximal to the AC in a normal adult (Fig. 1) and local anesthetic injected here is subsartorial at the level of the femoral triangle (FT). This is clinically important because even with 30 mL of local anesthetic, the injectate cannot be expected to spread reliably distal throughout the AC. This is confirmed by the solitary MR T2-weighted image provided by Jæger et al1 in their reply to our letter. The coronal plane inlet in their figure shows that local anesthetic spreads only a few centimeters from the needle insertion point. Of course, one image from an arbitrary patient is not a final proof, as also acknowledged by Jæger et al. We are not quite sure what kind of MR sequence the term “turbo inversion recovery magnitude” refers to, but we assume it is a STIR sequence, which we agree can be combined with T1- and T2weighted sequences to discriminate safely between fat, muscle, and water. The now presented T2-weighted image from another patient apparently allows discrimination between water and fat. But the problem
remains as displayed by the MR image published in the original paper that T2weighted images do not always allow “safe” discrimination between water and fat. Accordingly, it would have been pertinent if Jæger et al had shown the other MRI sequences of the patient presented in the original paper to substantiate their point. It is clinically relevant that the local anesthetic does not spread throughout the AC after ACB. The ACB by Jæger et al is merely a subsartorial saphenous nerve block at the level of the FT. The saphenous nerve is the one and only nerve consistently present within the AC. The knee joint is innervated by the femoral nerve through the 3 vasti branches and the saphenous nerve, and also by the posterior branch of the obturator nerve and the genicular branches from the tibial and common peroneal branches of the sciatic nerve. The posterior obturator nerve descends outside the AC.4 Sometimes, branches from the posterior obturator nerve accompany the femoral artery through the adductor hiatus.4 But even in those patients, the posterior obturator branch is not consistently anesthetized by local anesthetic spread with the ACB technique described by Jæger et al.1 Jæger et al1 have eloquently documented that the ACB is equivalent to a
Redefining the Adductor Canal Block Accepted for publication: May 24, 2014.
To the Editor: e want to thank Jæger and colleagues1 for responding to our concerns about the so-called adductor canal block (ACB).2 However, some important issues require further clarification. Jæger et al1 state that the anatomical basis of the ACB has academic interest but limited clinical relevance. Because we agree with Alon Winnie that “regional anesthesia is simply an excercise of applied anatomy,” we believe that it is highly relevant to discuss and understand the anatomical basis of ACB. The needle insertion point for the ACB as defined by Jæger et al1—and in past publications by the same research group—is the midpoint between the anterior superior iliac spine and the base of the patella. Jæger et al1 insist that this point is per definition within the adductor canal
W
442
FIGURE 1. The photographs show a cadaver limb from a man (A) and a woman (B). The distance from the base of patella (red) to the anterior superior iliac spine (blue) is 50 cm in the male limb and 44 cm in the female limb. The midpoint (cyan) is 25 cm proximal to the base of the patella in the male and 22 cm in the female limb. The midpoint is approximately 9 cm from the upper margin (magenta) of the AC in the male and 7.5 cm in the female limb. The distance from the lower border of the greater trochanter (green) to the base of patella (red) is 32 cm in the male and 29 cm in the female limb, and the midpoint (yellow) is at the level of the AC. © 2014 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 39, Number 5, September-October 2014
Letters to the Editor
Another clarification is required for the statement of Jæger et al1 that “the AC is roofed by the sartorius muscle and the underlying fascia.” First, the sartorius muscle is not the roof of the AC. The muscle lies on the roof of the AC. Second, the roof itself is built by the vastoadductor membrane which is not a fascia.6 This is relevant because sonographically membranes, aponeuroses, ligaments, intramuscular septae, and tracts are typically doublelayered hyperechoic structures, whereas fascia has 1 layer. It is also clinically important that the subsartorial plexus is located outside the AC and sandwiched between the vastoadductor membrane and the sartorius muscle. The subsartorial plexus receives branches from the saphenous nerve, the medial cutaneous femoral nerve, and the anterior division of the obturator nerve. It innervates the skin of the medial side of the thigh. Thus, the subsartorial plexus is not anesthetized even by a true ACB. In conclusion, the technique of ACB as described by Jæger et al1 is a subsartorial saphenous nerve block at the level of the FT, not an ACB, and it cannot be expected to reliably block the posterior branch of the obturator nerve by spread through the adductor hiatus. That would require a true ACB, which was described by Manickam et al7 in 2009. In our opinion, the simplest and most effective way to block both the saphenous nerve and the posterior branch of the obturator nerve consistently is to use 2 selective small volume blocks. However, only few studies demonstrate the need for obturator nerve block after TKA and further research is mandated to clarify this.
Histology and Embryology Innsbruck Medical University Innsbruck, Austria
femoral nerve block for analgesia after total knee replacement (TKA) with preserved quadriceps strength. A possible explanation is that the vasti branches are not clinically important for post-TKA analgesia. Jæger et al1 are probably correct to state that analgesia after TKA is improved when a subsartorial saphenous nerve block is combined with a posterior obturator nerve block. As explained, the ACB technique of Jæger el al does not achieve this. However, posterior obturator nerve block can be achieved by ultrasoundguided blockade of either the common obturator nerve or the posterior branch in the subinguinal region just as easy as the subsartorial saphenous nerve block. It is surprising that the authors dismiss the block combination of the saphenous and obturator nerves based on concerns about risks of complications and difficulty of performance. Most regional anesthetists who work clinically with regional anesthesia techniques on a daily basis would categorize these blocks as basic level. Instead, Jæger et al1 recommend a technique that defeats its own purpose of dual nerve blockade combined with insertion of a catheter into the AC which is indeed an advanced level procedure associated with a higher risk of complications. Also, the frequency of secondary displacement of AC catheters inserted in-plane across the short axis of the saphenous nerve is very high, making catheter insertion redundant (unpublished data). Much confusion is stirred up by the phrase “midthigh,” which can have different definitions. This probably explains misinterpretation by Jæger et al1 for the term “midthigh” as stated in a recently published article by Børglum et al5 and in Gray’s anatomy. It is only correct to state that the AC is located in the midthigh when the “midthigh” is defined by the middle one third of the distance from the base of the patella to the lower border of the greater trochanter. The distance from the base of the patella to the lower border of the greater trochanter is approximately 30 cm in a normal adult (Fig. 1).
Thomas Fichtner Bendtsen, MD, PhD Department of Anesthesiology and Intensive Care Medicine, Aarhus University Hospital, Aarhus, Denmark
Bernhard Moriggl, MD, PhD Division of Clinical and Functional Anatomy Department of Anatomy
© 2014 American Society of Regional Anesthesia and Pain Medicine
Vincent Chan, MD Department of Anesthesia University of Toronto Toronto, Ontario, Canada Department of Anesthesia Toronto Western Hospital Toronto, Ontario, Canada
Erik Morre Pedersen, MD, DMSc Department of Radiology, Aarhus University Hospital, Aarhus, Denmark
Jens Børglum, MD, PhD Department of Anesthesia and Intensive Care Medicine, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark
The authors declare no conflict of interest.
REFERENCES 1. Jæger P, Lund J, Jenstrup MT, Brøndum V, Dahl JB. Reply to Dr Bendtsen. Reg Anesth Pain Med. 2014;39:254–255. 2. Bendtsen TF, Moriggl B, Chan V, Pedersen EM, Børglum J. Defining adductor canal block. Reg Anesth Pain Med. 2014;39:253–254. 3. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surg Radiol Anat. 2007;29:569–573. 4. Kumka M. Critical sites of entrapment of the posterior division of the obturator nerve: anatomical considerations. J Can Chiropr Assoc. 2010;54:33–42. 5. Børglum J, Johansen K, Christensen MD, et al. Ultrasound-guided single-penetration dual-injection block for leg and foot surgery: a prospective, randomized, double-blind study. Reg Anesth Pain Med. 2014;39:18–25. 6. Terminologia Anatomica. FCAT—Federative Committee on Anatomical Terminology. 1998, Thieme, Stuttgart, New York. 7. Manickam B, Perlas A, Duggan E, Brull R, Chan VW, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the saphenous nerve in the AC. Reg Anesth Pain Med. 2009;34:578–580.
443
Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
