Explore the vast range of titles available.

The popularity of ultrasound-guided nerve blocks has impacted the practice of regional anesthesia in profound ways, improving some techniques and introducing new ones. Some of these new nerve blocks are based on the concept of fascial plane blocks, in which the local anesthetic is injected into a plane instead of around a specific nerve. Pectoralis muscles (PECS) and serratus blocks, most commonly used for post op analgesia after breast surgery, are good examples. Among the nerves targeted by PECS/serratus blocks are different branches of the brachial plexus that traditionally have been considered purely motor nerves. This unsubstantiated claim is a departure from accepted anatomical knowledge and challenges our understanding of the sensory innervation of the chest wall. The objective of this Daring Discourse is to look beyond the ability of PECS/serratus blocks to provide analgesia/anesthesia of the chest wall, to concentrate instead on understanding the mechanism of action of these blocks and, in the process, test the veracity of the claim. After a comprehensive review of the evidence we have concluded that (1) the traditional model of sensory innervation of the chest wall, which derives from the lateral branches of the upper intercostal nerves and does not include branches of the brachial plexus, is correct. (2) PECS/serratus blocks share the same mechanism of action, blocking the lateral branches of the upper intercostal nerves, and so their varied success is tied to their ability to reach them. This common mechanism agrees with the traditional innervation model. (3) A common mechanism of action supports the consolidation of PECS/serratus blocks into a single thoracic fascial plane block with a point of injection closer to the effector site. In a nod to transversus abdominus plane block, the original inspiration for PECS blocks, we propose naming this modified block, the serratus anterior plane block.

Correspondence to Dr Carlo D Franco, Anesthesiology, John H Stroger Jr Hospital of Cook County, Chicago, IL 60612, USA; carlofra@aol.com We would like to thank Dr Hongye et al for their interest in our article1; however, we would like to clarify that we did not suggest that pecoralis muscles/serratus blocks fail to provide some degree of sensory analgesia/anesthesia of the chest wall. [...]this does not refute our argument since the results of such studies do not distinguish whether the observed effect comes from a block of the pectoral nerves or from spread to other targets. [...]we did not say that ‘muscle pain likely stems from C fibers containing sensory afferent fibers’.

Correspondence to Dr Carlo D Franco, Anesthesiology, John H Stroger Jr Hospital of Cook County, Chicago, IL 60657, USA; carlofra@aol.com We have read with interest the letter by Dr Altinpulluk et al 1 concerning our recent publication2 in which we made an attempt to determine the mechanism of action for PECS/serratus block according to the most widely used model of sensory innervation of the chest wall. In this scenario, the dermatomal map of the chest would resemble more a geographic map, with different patches representing individual roots of the brachial plexus. [...]every time we determine a spinal level by using for example the nipple line to ascertain a T4 spread, we are implicitly accepting the traditional innervation model, the only one ever proposed, of the chest wall. [...]we wanted to demonstrate that such success is likely the result of spread of local anesthetic to the line of emergence of the lateral branches of upper intercostal nerves and, in that context, we proposed to move the injection site closer to it.

Background and ObjectivesChronic knee pain is common in all age groups. Some patients who fail conservative therapy benefit from radiofrequency neurotomy. Knowledge of the anatomy is critical to ensure a successful outcome. The purpose of this study was to reanalyze the innervation to the anterior knee capsule from the perspective of the interventional pain practitioner.MethodsThe study included a comprehensive literature review followed by dissection of 8 human knees to identify the primary capsular innervation of the anterior knee joint. Photographs and measurements were obtained for each relevant nerve branch. Stainless-steel wires were placed along the course of each primary innervation, and radiographs were obtained.ResultsLiterature review revealed a lack of consensus on the number and origin of nerve branches innervating the anterior knee capsule. All dissections revealed the following 6 nerves: superolateral branch from the vastus lateralis, superomedial branch from the vastus medialis, middle branch from the vastus intermedius, inferolateral (recurrent) branch from the common peroneal nerve, inferomedial branch from the saphenous nerve, and a lateral articular nerve branch from the common peroneal nerve.Nerve branches showed variable proximal trajectories but constant distal points of contact with femur and tibia. The inferolateral peroneal nerve branch was found to be too close to the common peroneal nerve, making it inappropriate for radiofrequency neurotomy.ConclusionsThe innervation of the anterior capsule of the knee joint seems to follow a constant pattern making at least 3 of these nerves accessible to percutaneous ablation. To optimize clinical outcome, well-aligned radiographs are critical to guide lesion placement.

Background and ObjectivesThe “stoplight” sign is a frequently described image during ultrasound-guided interscalene block, referring to 3 hypoechoic structures found between the anterior and middle scalene muscles.This study was designed to establish the ultrasound-anatomy correlation of this sign and to find any other anatomical features within the roots that could help with the interpretation of the ultrasound images obtained at the interscalene level.MethodsWe performed 20 dissections of the brachial plexus in 10 embalmed human cadavers and systematically analyzed and measured the roots of C5 to C7 and then correlated these findings with ultrasonographic images on file.ResultsWe found that the C5 root is significantly smaller than either C6 or C7 (P < 0.0001). We also found that C6 and C7, but not C5, frequently present macroscopic evidence of intraroot splitting visible to the naked eye. We also found that the roots of C5 and C6, but not of C7, present frequent variations in their relationship with the scalene muscles.ConclusionsOur results provide the anatomic basis to define the stoplight sign as one made of, from cephalad to caudal, the root of C5, the upper fascicle(s) of C6, and the lower fascicle(s) of C6 without contribution from C7. The important clinical implication is that an injection attempted between what is commonly perceived as the gap between C6 and C7 would indeed be an intraneural injection at C6, which could potentially spread toward the neuraxial space.