Comment on ‘Fascial layers influence the spread of injectate during ultrasound-guided infraclavicular brachial plexus block: a cadaver study’ (Br J Anaesth 2018; 121: 876–82)

Abstract

Editor—We read with interest the recent publication by Brenner and colleagues1Brenner D. Mahon P. Iohom G. Cronin M. Flynn C.O. Shorten G. Fascial layers influence the spread of injectate during ultrasound-guided infraclavicular brachial plexus block: a cadaver study.Br J Anaesth. 2018; 121: 876-882Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar in which they describe the influence of fascial layers during ultrasound-guided infraclavicular brachial plexus blockade in human cadavers. The authors speculate that fascial layers influence the distribution of local anaesthetics in the infraclavicular region, with possible consequences regarding block success. We have some remarks that should be considered as constructive additions. Even though not investigated in the present study, the authors start with a description of the axillary region. There is a clear anatomical border between the axillary and infraclavicular regions (pectoralis minor muscle). The authors state that the apex (or peak) of the axillary fossa is the deltopectoral fossa (the correct nomenclature would be the ‘deltopectoral triangle’), but the apex (peak) of the axillary fossa is the coracoid process.2Hafferl A. Obere Extremität.in: Hafferl A. Lehrbuch der Totographischen Anatomie. 3rd ed. Springer, Berlin, Heidelberg, New York1969: 712-741Google Scholar The deep deltopectoral triangle is divided into a superficial and deep space by the clavipectoral fascia, which is not mentioned in their paper. This clavipectoral fascia is a continuation of the prevertebral fascia, which is the deep layer of the deep cervical fascia.3Hollinshead W.H. Fascia and fascial spaces of the neck.in: Anatomy for surgeons: the head and neck. vol. 1. Lippincott JB, Philadelphia1968: 306-330Google Scholar The deep cervical fascia has three layers according to international terminology and two layers according to middle European terminology.4Feigl G. Fascia and spaces on the neck: myths and reality.Medicina Fluminensis. 2015; 51: 430-439Google Scholar The authors just mention the deep cervical fascia, but do not provide further details. The correct anatomical description is that the prevertebral fascia inserts in the muscular fascia of the subclavius muscle, continues as the deep layer of the clavipectoral fascia, and continues further as the deep axillary fascia (also not mentioned in their paper) in the axillary fossa (Fig. 1).5Hafferl A. Halsfaszien und- räume.in: Hafferl A. Lehrbuch der Topographischen Anatomie. 3rd ed. Springer, Berlin, Heidelberg, New York1969: 224-230Google Scholar, 6Grodinsky M. Holyoke E.A. The fasciae and fascial spaces of the head, neck and adjacent Regions.Am J Anat. 1938; 63: 367-408Crossref Google Scholar The axillary fossa has as a base the superficial axillary fascia, which is a so-called ‘fascia cribrosa’. This fascia is pierced by lymphatic vessels, veins, small arteries, and nerves (medial cutaneous branch of the arm and intercostobrachial nerve). By opening the fascia, a huge space is reached which contains lymph nodes, fat tissue, vessels, and nerves (thoracodorsal vessels and nerve, subscapular artery, lateral thoracic artery). This space is defined as the subfascial axillary space.7Feigl G. Aichner E. Mattersberger C. Zahn P.K. Avila Gonzalez C. Litz R. Ultrasound-guided anterior approach to the axillary and intercostobrachial nerves in the axillary fossa: an anatomical investigation.Br J Anaesth. 2018; 121: 883-889Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar Proximal and lateral, the deep axillary fascia is a fascial wall between the subfascial axillary space and the deep axillary space, which contains the brachial plexus and the axillary artery. The so called ‘neurovascular sheath’ derives, according to the authors, from the deep cervical fascia, which is not correct. The topographical anatomy of the prevertebral fascia is explained above.4Feigl G. Fascia and spaces on the neck: myths and reality.Medicina Fluminensis. 2015; 51: 430-439Google Scholar However, septa that are visible and identifiable by ultrasonography, are produced by the epineural sheath (which is a continuation of the dura) of each ventral branch of the brachial plexus segments and splits whenever a nerve or nerve branch arises from any part of the plexus at various levels. Consequently, the number of detectable septa increases from proximal to distal. Distinct fascial tunnels are formed in the infraclavicular and axillary regions. The brachial plexus does not enter the medial intermuscular septum of the arm, as stated in the paper. This septum is located between the muscular compartment of the arm and shows a high variability. Some of the nerves have no relation to the septum (in particular the radial and axillary nerves) because they run too proximal, or the nerve is too far away (in particular the median, and medial cutaneous nerves of the arm and forearm). The only nerve that might pierce the septum is the ulnar nerve. Brenner and colleagues1Brenner D. Mahon P. Iohom G. Cronin M. Flynn C.O. Shorten G. Fascial layers influence the spread of injectate during ultrasound-guided infraclavicular brachial plexus block: a cadaver study.Br J Anaesth. 2018; 121: 876-882Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar illustrate in Fig. 1 of their publication, the neurovascular bundle underneath the pectoralis minor muscle as a circular structure. This is incorrect because of to the absence of a dorsal wall where the space including the brachial plexus extends into the thoracoscapular gliding gap (alias scapulothoracic joint). The images in the results section do not really show a septum. The injection of latex and ink, as described in their methods section, makes a correct dissection and subsequent interpretation of the results difficult. Ink will spread in all directions once the fascial tunnels are damaged. Even if this is not described in the literature, the uncontrolled spread of ink is based on observations of many anatomical institutes and more than 50 yr of experience. Finally, we have concerns that no anatomical textbook appears in the list of references to support their anatomical descriptions. Useful anatomical textbooks such as Hafferl,2Hafferl A. Obere Extremität.in: Hafferl A. Lehrbuch der Totographischen Anatomie. 3rd ed. Springer, Berlin, Heidelberg, New York1969: 712-741Google Scholar, 5Hafferl A. Halsfaszien und- räume.in: Hafferl A. Lehrbuch der Topographischen Anatomie. 3rd ed. Springer, Berlin, Heidelberg, New York1969: 224-230Google Scholar Hollinshead,3Hollinshead W.H. Fascia and fascial spaces of the neck.in: Anatomy for surgeons: the head and neck. vol. 1. Lippincott JB, Philadelphia1968: 306-330Google Scholar or other publications4Feigl G. Fascia and spaces on the neck: myths and reality.Medicina Fluminensis. 2015; 51: 430-439Google Scholar, 6Grodinsky M. Holyoke E.A. The fasciae and fascial spaces of the head, neck and adjacent Regions.Am J Anat. 1938; 63: 367-408Crossref Google Scholar, 7Feigl G. Aichner E. Mattersberger C. Zahn P.K. Avila Gonzalez C. Litz R. Ultrasound-guided anterior approach to the axillary and intercostobrachial nerves in the axillary fossa: an anatomical investigation.Br J Anaesth. 2018; 121: 883-889Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar should be included in such a manuscript to support all anatomical details with adequate scientific background. PM is as board member of the British Journal of Anaesthesia. GF declared no conflicts of interest. Fascial layers influence the spread of injectate during ultrasound-guided infraclavicular brachial plexus block: a cadaver studyBritish Journal of AnaesthesiaVol. 121Issue 4PreviewFascial layers of the neurovascular sheath containing the brachial plexus influence distribution of local anaesthetic, hence increasing the risk of block failure when performing infraclavicular brachial plexus block (ICB). Full-Text PDF Open ArchiveResponse to ‘Comment on ‘Fascial layers influence the spread of injectate during ultrasound-guided infraclavicular brachial plexus block: a cadaver study’ (Br J Anaesth 2019; 122: e54–5)’British Journal of AnaesthesiaVol. 122Issue 3PreviewEditor—We thank Feigl and Marhofer1 for their comments on our study published in the British Journal of Anaesthesia2 in which they criticised the anatomical terminology used. Although we strongly agree that the use of correct terminology is extremely important, the challenge of using a universally understood and accepted terminology for anatomical features is well recognised.3 The terminology we used to describe the axilla is based on accounts provided in respected texts such as those of Williams4 and Szentágothai. Full-Text PDF Open Archive