Recent recommendations describe a set of core anatomical structures to identify on ultrasound for the performance of basic blocks in ultrasound-guided regional anesthesia (UGRA). This project aimed to generate consensus recommendations for core structures to identify during the performance of intermediate and advanced blocks. An initial longlist of structures was refined by an international panel of key opinion leaders in UGRA over a three-round Delphi process. All rounds were conducted virtually and anonymously. Blocks were considered twice in each round: for "orientation scanning" (the dynamic process of acquiring the final view) and for "block view" (which visualizes the block site and is maintained for needle insertion/injection). A "strong recommendation" was made if ≥75% of participants rated any structure as "definitely include" in any round. A "weak recommendation" was made if >50% of participants rated it as "definitely include" or "probably include" for all rounds, but the criterion for strong recommendation was never met. Structures which did not meet either criterion were excluded. Forty-one participants were invited and 40 accepted; 38 completed all three rounds. Participants considered the ultrasound scanning for 19 peripheral nerve blocks across all three rounds. Two hundred and seventy-four structures were reviewed for both orientation scanning and block view; a "strong recommendation" was made for 60 structures on orientation scanning and 44 on the block view. A "weak recommendation" was made for 107 and 62 structures, respectively. These recommendations are intended to help standardize teaching and research in UGRA and support widespread and consistent practice.

There is no universally agreed set of anatomical structures that must be identified on ultrasound for the performance of ultrasound-guided regional anesthesia (UGRA) techniques. This study aimed to produce standardized recommendations for core (minimum) structures to identify during seven basic blocks. An international consensus was sought through a modified Delphi process. A long-list of anatomical structures was refined through serial review by key opinion leaders in UGRA. All rounds were conducted remotely and anonymously to facilitate equal contribution of each participant. Blocks were considered twice in each round: for “orientation scanning” (the dynamic process of acquiring the final view) and for the “block view” (which visualizes the block site and is maintained for needle insertion/injection). Strong recommendations for inclusion were made if ≥75% of participants rated a structure as “definitely include” in any round. Weak recommendations were made if >50% of participants rated a structure as “definitely include” or “probably include” for all rounds (but the criterion for “strong recommendation” was never met). Thirty-six participants (94.7%) completed all rounds. 128 structures were reviewed; a “strong recommendation” is made for 35 structures on orientation scanning and 28 for the block view. A “weak recommendation” is made for 36 and 20 structures, respectively. This study provides recommendations on the core (minimum) set of anatomical structures to identify during ultrasound scanning for seven basic blocks in UGRA. They are intended to support consistent practice, empower non-experts using basic UGRA techniques, and standardize teaching and research.

INTRODUCTION:Instrumenting the anterior abdominal wall carries a potential for vascular trauma. We previously assessed the presence, position, and size of the anterior abdominal wall superior and inferior (deep) epigastric arteries with computed tomography (CT). We now present a study using ultrasound (US) assessment of these arteries, to evaluate its use for real time guidance of percutaneous procedures involving the rectus sheath.MATERIALS AND METHODS:Twenty-four participants (mean age 67.9 ± 9 years, 15 M:9 F [62:38%]) were assessed with US at three axial planes on the anterior abdominal wall: transpyloric plane (TPP), umbilicus, and anterior superior iliac spine (ASIS).RESULTS:An artery was visible least frequently at the TPP (62.5 - 45.8%), compared with the umbilicus (95.8-100%) and ASIS (100%), on the left, χ2 (2) = 20.571; p < .001, and right, χ2 (2) = 27.842; p < .001, with a moderate strength association (Cramer's V = 0.535 [left] and 0.622 [right]). Arteries were most commonly observed within the rectus abdominis muscle at the level of the TPP and umbilicus, but posterior to the muscle at the level of the ASIS (95.8-100%). As with the CT study, the inferior epigastric artery was observed to be larger in diameter, start more laterally, and move medially as it coursed superiorly.CONCLUSIONS:These data corroborate our previous results and suggest that the safest level to instrument the rectus sheath (with respect to vascular anatomy) is at the TPP. Such information may be particularly relevant to anesthetists performing rectus sheath block and surgeons during laparoscopic port insertion.

Editor—Structural and functional variation of the peripheral nervous system is known to exist. Recent reports have discussed the potential for such variation to impact the efficacy of regional anaesthesia techniques.1Desai N. Merjavy P. Anatomical Variation of the Brachial Plexus and its Clinical Implications. Anaesthesia Tutorial of the Week, 2017Google Scholar, 2Keplinger M. Marhofer P. Moriggl B. Zeitlinger M. Muehleder-Mattere S. Marhofer D. Cutaneous innervation of the hand: clinical testing in volunteers shows high intra- and inter-individual variability.Br J Anaesth. 2018; 120: 836-845Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar Our group has been assessing the anatomy of the superficial peroneal nerve (SPN, aka superficial fibular nerve),3Bowness J. Turnbull K. Taylor A. et al.Identifying the emergence of the superficial peroneal nerve through deep fascia on ultrasound and by dissection: implications for regional anesthesia in foot and ankle surgery.Clin Anat Adv. 2018; (Access published on December 10)https://doi.org/10.1002/ca.23323Crossref Scopus (7) Google Scholar as we find that the dorsum of the foot may develop incomplete anaesthesia during awake surgery under ankle block. Natural variation in the structure of the SPN has been described in the anatomical literature.4Tomaszewski K.A. Graves M.J. Vikse J. et al.Superficial fibular nerve variations of fascial piercing: a meta-analysis and clinical consideration.Clin Anat. 2017; 30: 120-125Google Scholar, 5Reiman R. Accessory peroneal nerves in the human.Anat Anz. 1984; 155: 257-267Google Scholar, 6Adkison D.P. Bosse M.J. Gaccione D.R. Gabriel K.R. Anatomical variations in the course of the superficial peroneal nerve.J Bone Jt Surg Am. 1991; 73: 112-114Crossref PubMed Scopus (127) Google Scholar, 7Canella C. Demondion X. Guillin R. Boutry N. Peltier J. Cotten A. Anatomic study of the superficial peroneal nerve using sonography.Am J Roentgenol. 2009; 193: 174-179Crossref PubMed Scopus (57) Google Scholar, 8Pacha D. Carrera A. Llusa M. Permanyer E. Molona O. Morro R. Clinical anatomy of the superficial peroneal nerve in the distal leg.Eur J Anat. 2003; 7: 15-20Google Scholar However, clinical accounts of the SPN and ankle block often focus on clinical aspects and the anatomical descriptions are less detailed.9Purushothaman L. Allan A.G.L. Bedforth N. Ultrasound-guided ankle block.Br J Anaesth Ed. 2013; 13: 174-178Scopus (9) Google Scholar We questioned whether failure to transfer anatomical knowledge to clinical practice may lead to variability in identifying relevant anatomy by anaesthetists, which in turn may influence regional anaesthesia success. We therefore assessed the recognition of variant anatomy of the SPN by two consultant anaesthetists who had completed advanced training in ultrasound-guided regional anaesthesia (UGRA) and are considered local experts with publications in this field. With approval from the University of St Andrews School of Medicine Ethics Committee (MD13364), we recruited eight male and eight female volunteers (mean age 29 yr, range 19–50 yr) with written informed consent, which allowed us to assess the sonoanatomy of the SPN on 32 limbs. We marked the most prominent part of the lateral malleolus (LM) and the head of the fibula (HF), and then drew a straight line on the skin between these two points (LM-HF line). The ultrasound operators were not informed of the objective of recognising variant anatomy. We asked them to independently identify the nerve on ultrasound at the anterolateral ankle, then trace it proximally to the point at which it penetrated the deep (crural) fascia and further to the point of origin at the neck of the fibula. In our practice, the site at which we target the SPN during an ultrasound-guided ankle block is the point immediately after it penetrates the fascia to lie in a more superficial plane. This point was marked and then a second straight line (intersecting line) drawn from it to intersect the LM-HF line (Fig. 1). The distance from the LM to the point at which the intersecting line crossed the LM-HF line was measured, as was the total distance of the LM-HF line. A ratio of these distances was calculated;3Bowness J. Turnbull K. Taylor A. et al.Identifying the emergence of the superficial peroneal nerve through deep fascia on ultrasound and by dissection: implications for regional anesthesia in foot and ankle surgery.Clin Anat Adv. 2018; (Access published on December 10)https://doi.org/10.1002/ca.23323Crossref Scopus (7) Google Scholar we use this ratio in clinical practice as a guide to begin ultrasound assessment of the leg to identify the SPN. The two ultrasound operators were then informed of the results of previous work,3Bowness J. Turnbull K. Taylor A. et al.Identifying the emergence of the superficial peroneal nerve through deep fascia on ultrasound and by dissection: implications for regional anesthesia in foot and ankle surgery.Clin Anat Adv. 2018; (Access published on December 10)https://doi.org/10.1002/ca.23323Crossref Scopus (7) Google Scholar, 4Tomaszewski K.A. Graves M.J. Vikse J. et al.Superficial fibular nerve variations of fascial piercing: a meta-analysis and clinical consideration.Clin Anat. 2017; 30: 120-125Google Scholar, 5Reiman R. Accessory peroneal nerves in the human.Anat Anz. 1984; 155: 257-267Google Scholar, 6Adkison D.P. Bosse M.J. Gaccione D.R. Gabriel K.R. Anatomical variations in the course of the superficial peroneal nerve.J Bone Jt Surg Am. 1991; 73: 112-114Crossref PubMed Scopus (127) Google Scholar, 7Canella C. Demondion X. Guillin R. Boutry N. Peltier J. Cotten A. Anatomic study of the superficial peroneal nerve using sonography.Am J Roentgenol. 2009; 193: 174-179Crossref PubMed Scopus (57) Google Scholar, 8Pacha D. Carrera A. Llusa M. Permanyer E. Molona O. Morro R. Clinical anatomy of the superficial peroneal nerve in the distal leg.Eur J Anat. 2003; 7: 15-20Google Scholar which identified variation in the course and structure of the SPN. They were then asked to re-scan the legs of the same volunteers to assess for more than one branch of the SPN emerging through the deep fascia. The SPN was identified in all limbs, and the mean ratio of distances (LM-intersecting line:LM-HF) was 0.44 (standard deviation 0.1, 95% confidence interval 0.40–0.48). On the first scan, the SPN was identified as emerging through the deep fascia at a single point in all cases. On the second scan, when variant anatomy was specifically assessed, accessory branches of the SPN were found piercing the deep fascia in a different location to the main branch in five of 32 legs (15.6%). These data support existing evidence that one can identify structural anatomical variation of peripheral nerves on ultrasound (in this case multiple points of emergence of the SPN).7Canella C. Demondion X. Guillin R. Boutry N. Peltier J. Cotten A. Anatomic study of the superficial peroneal nerve using sonography.Am J Roentgenol. 2009; 193: 174-179Crossref PubMed Scopus (57) Google Scholar Such variation may already be described in anatomical literature, to differing extents for different nerves. These data are consistent with our hypothesis that this knowledge is not effectively transferred to the anaesthesia literature or clinical practice. Thus, regional anaesthetists may fail to account for variant structure(s) when performing peripheral nerve blocks and so may not target all of the nerves or branches. Even the correct nerves or branches may not be targeted, as small superficial nerves can be difficult to identify on ultrasound. The results of this small study could also be interpreted as initial incorrect identification of the nerve structures. These factors could reduce the efficacy of regional anaesthetic techniques. Although structural variation was noted in this study, the authors recognise that this particular example may not necessarily result in a clinically significant difference in outcome during blockade of the SPN. Nonetheless, these data suggest that clinical anaesthetists should be aware of such information when performing UGRA. The authors note the difference in ratios between our first3Bowness J. Turnbull K. Taylor A. et al.Identifying the emergence of the superficial peroneal nerve through deep fascia on ultrasound and by dissection: implications for regional anesthesia in foot and ankle surgery.Clin Anat Adv. 2018; (Access published on December 10)https://doi.org/10.1002/ca.23323Crossref Scopus (7) Google Scholar and second study: 0.31 (0.07) and 0.44 (0.1), respectively. This could reflect a true difference in the two populations studied. However, some of the volunteers scanned were the same as in our previous study cohort, so may reflect the fact that different anaesthetists scanned volunteers in the two studies and that sonoanatomy interpretation is subjective. This in itself may contribute to perceived variation and ultimately regional anaesthesia failure. We feel more should be done to consolidate peripheral nerve anatomical knowledge, establish more robust systems of ultrasound assessment and sonoanatomy interpretation, and transfer this information to clinical practice. We would encourage anaesthetists to lead in investigation of this area rather than accept incomplete accounts of the relevant anatomy. The authors would like to thank the participants who volunteered for this study and the Clinical Skills Department at St Andrews University School of Medicine for access to and use of facilities and ultrasound equipment. The authors declare that they have no conflicts of interest.

Multiple medical interventions require percutaneous instrumentation of the anterior abdominal wall, all of which carry a potential for vascular trauma. We assessed the presence, position, and size of the anterior abdominal wall superior and inferior (deep) epigastric arteries to determine the safest site with respect to vascular anatomy of the rectus sheath. In a review of 100 arterial phase, contrast‐enhanced abdominal computed tomography scans, anterior abdominal wall arteries were assessed bilaterally at three axial planes: transpyloric, umbilicus, and anterior superior iliac spine (ASIS). The mean age of patients was 69.2 years (SD ± 15), with 62 male and 38 female. An artery was visible least frequently at the transpyloric plane (5%), compared with the umbilicus (72–79%) and ASIS (93–96%), on the left ( χ 2 (4) = 207.272; P < 0.001) and right ( χ 2 (4) = 198.553; P < 0.001), with a moderate strength association (Cramer's V = 0.588 (left) and 0.575 (right)). The arteries were most commonly observed within the rectus abdominis muscle at the level of the umbilicus and ASIS on both sides (62–68%). The inferior epigastric artery was observed to be larger in diameter, start more laterally, and move medially as it travelled superiorly. These data suggest that the safest site to instrument the rectus sheath, with respect to vascular anatomy, is at the transpyloric plane. This information on anatomical variation of the anterior abdominal wall vasculature may be of particular interest to anesthetists performing rectus sheath block and surgeons during laparoscopic port insertion. Clin. Anat. 33:350–354, 2020. © 2019 Wiley Periodicals, Inc.

Regional anesthesia relies on a sound understanding of anatomy and the utility of ultrasound in identifying relevant structures. We assessed the ability to identify the point at which the superficial peroneal nerve (SPN) emerges through the deep fascia by ultrasound on 26 volunteers (mean age 27.85 years ± 13.186; equal male: female). This point was identified, characterized in relation to surrounding bony landmarks (lateral malleolus and head of the fibula), and compared to data from 16 formalin‐fixed human cadavers (mean age 82.88 years ± 6.964; equal male: female). The SPN was identified bilaterally in all subjects. On ultrasound it was found to pierce the deep fascia of the leg at a point 0.31 (±0.066) of the way along a straight line from the lateral malleolus to the head of the fibula (LM‐HF line). This occurred on or anterior to the line in all cases. Dissection of cadavers found this point to be 0.30 (±0.062) along the LM‐HF line, with no statistically significant difference between the two groups (U = 764.000; exact two‐tailed P = 0.534). It was always on or anterior to the LM‐HF line, anterior by 0.74 cm (±0.624) on ultrasound and by 1.51 cm (±0.509) during dissection. This point was significantly further anterior to the LM‐HF line in cadavers (U = 257.700, exact two‐tailed P < 0.001). Dissection revealed the nerve to divide prior to emergence in 46.88% (n = 15) limbs, which was not identified on ultrasound (although not specifically assessed). Such information can guide clinicians when patient factors (e.g., obesity and peripheral edema) make ultrasound‐guided nerve localization more technically challenging. Clin. Anat. 32:390–395, 2019. © 2019 Wiley Periodicals, Inc.

The superficial peroneal nerve (SPN) provides cutaneous innervation to the distal anterolateral leg and dorsum of foot.1 Knowing the position where the SPN penetrates the deep fascia, to become superficial, is useful in clinical practice (e.g. ankle blocks and internal fixation of distal fibular fractures). However, there is variability in the literature as to where the SPN penetrates the deep fascia as well as the methodology to identify it with no standardised guidelines. Our primary aim was to identify this point and create a methodology protocol that could be implemented in clinical practice. The study involved sonography of living healthy adult volunteers and dissection of formalin-fixed cadavers with no past history of pathology or surgery affecting the SPN. During sonography, the bony prominences of the fibular head and lateral malleolus were identified and marked with a straight line. A 6-12 MHz linear array ultrasound probe was positioned anterior to the lateral malleolus and moved proximally to identify the location where the SPN penetrates the deep fascia to lie in a superficial plane. The lateral malleolus-fibular head (length of fibula) and lateral malleolus-SPN distances were measured. The distance of emergence from the deep fascia of the SPN anterior or posterior to the length of fibula was measured (fig 1). In the cadavers, a skin incision was made from the tibial tuberosity to the anterior intermalleolar line and the skin reflected laterally to a line posterior to fibula. The superficial fascia was explored to identify the SPN and branches (fig 2). The same bony landmarks/measurements as in the sonography were marked and measured to allow for comparison with the sonographic methodology. We successfully developed a protocol that can provide standardisation for identifying the SPN. This can reduce incorrect identification and improve success rates of clinical procedures, though individual variation must be considered. Reference: 1. STANDRING, S (Editor) 2008. Gray’s Anatomy The Anatomical Basis of Clinical Practice (Fortieth Edition). London: Churchill Livingstone ELSEVIER, page 1427. Acknowledgements: For their help and support in this study, we would to thank the volunteers, the anatomy technical staff, and the clinical skills suite manager from the University of St Andrews Medical School.