PENG Block 

Author: Jonathan P. Kline, MSNA, CRNA 

INTRODUCTION
The quest for a single shot regional technique that provides adequate analgesia for hip fracture, and subsequent surgery has captivated a generation of new frontier anesthesia providers for well over a decade. While the introduction of fascia iliaca block brought new life in to this seemingly impossible task, it has certain clinical facets that have made it considerably less desirable to routinely deploy. However, the fascia iliaca block has the undesirable side effect of possibly causing a femoral nerve motor block. This can inhibit mobility and participation in rehabilitation activities as well as ADLs. The PENG block, introduced in late 2018, takes a novel approach to this complex problem, and has reignited interest into this valuable new possibility. The new PENG block technique avoids the problems associated with the fascia iliaca block, is relatively easy to perform, does not require large volumes of high concentration local anesthetic, and seems to be relatively low risk.

REVIEW OF THE LITERATURE
As of this writing, there is not a great deal of literature on this novel technique. The PENG block, which stands for Pericapsular Nerve Group, was first introduced in late 2018, by a group of well known regionalists primarily from Canada. In fact, its curious that the technique name shares its name with one of the authors, Phillip Peng, an anatomist from the university of Toronto. In their small group of 5 patients, the investigators demonstrated lower pain scores on patients with recent hip fractures in both static, and 15 degree movement requests (1). The original article utilized a curvilinear probe, placed originally over the femoral artery, similar to a femoral block technique. The probe was then pivoted allowing a view of the anterior pelvic ring, highlighting the iliopubic eminence and posts tendon attachment. Later that year, a report surfaced as a letter to the editor appeared already using the PENG block. The authors reported that they had slightly modified the technique by using a linear probe, with favorable results (2). Lastly, Dr Peng was involved in the original research into a recent remapping of the innervation to the anterior hip. The groups efforts revealed the importance of a previously under represented presence of the obturator accessory nerve in about half of the specimens (3). This may explain why, despite a well placed fascia iliaca block, some patients may still experience a great deal of pain as this technique does not concentration local to the obturator accessory nerve, especially on those patients with this nerves dominance to the hip. Unlike other techniques targeting major nerves that have some peripheral contribution to the hip and femur, the PENG block targets a traditionally overlooked nerve, that contributes sensory innervation to the hip itself, called the obturator accessory nerve. This nerve runs along the anterior pelvic ramus and is relatively superficial. According to the original article, the nerve has been shown to directly innervate the periosteum of the anterior hip.

TECHNIQUE
The originating article describes the use of a curvilinear probe, however, other reports have been successful with a linear probe. The technique begins with obtaining transverse view of the femoral triangle to visualize the femoral artery, vein and nerve. The lateral portion of the probe is anchored and medial portion of the probe is pivoted inferiorly to include the view of the femoral triangle structures and view of the pelvic rim, specifically the junction of the ilium and pubis, know as the iliopubic eminence (IPE). Following sterile skin preparation, a block needle is introduced from lateral to inferior medial direction, keeping them needle in plane. The needle is then introduced from superior lateral to inferior medial. The needle is directed deep to the psoas tendon, which lies on the anterior pelvis rim, near the iliopubic eminence (IPE). Local anesthetic is then deposited beneath the psoas tendon, and directed along the anterior surface of the pelvic rim. The published local is at the 20 ml volume, however the volume and concentrations should be considered on a case by case basis. This is the relative location of the obturator accessory nerve, providing sensation to the anterior rim of the hip, and femoral head. Both of which are frequent fracture sites.

Figure 1. Probe and needle placement for the PENG Block.

 

Figure 2. Graphic illustration for probe and needle placement for the PENG block.

Figure 3. Actual PENG block with needle at the IPE. Not the hypoechoic local anesthetic pushing the psoas tendon arteriorly.

 

CONCLUSION
Hip fracture pain may arise from a variety of innervations, and is complex based on patient to patient variability and fracture location making a single shot analgesic technique highly desirable. The PENG block technique offers relative ease in placement, reduction in target vascularity, and superficial location of the target nerve group a viable option for hip fracture pain. Initial reports indicate stable confidence in alleviating most pain arising from hip fracture pain. While in its infancy, the PENG block deserves further study to substantiate its initial findings. Special thanks to Jon Wilton DNP, CRNA and Stefan Swecker, CRNA for images.

REFERENCES

  1. Girón-Arango L, Peng PWH, Chin KJ, Brull R, Perlas A. Pericapsular Nerve Group (PENG) Block for Hip Fracture. Reg Anesth Pain Med. 2018 Nov;43(8):859-863. doi: 10.1097/AAP.0000000000000847.

  2. Mistry T, Sonawane KB, Kuppusamy E PENG block: points to ponder Regional Anesthesia & Pain Medicine Published Online First: 11 January 2019. doi: 10.1136/rapm-2018-100327

  3. Short AJ, Barnett JJG, Gofeld M, Baig E, Lam K, et al. (2018) Anatomic study of innervation of the anterior hip capsule: Implication for image-guided intervention. Reg Anesth Pain Med 43: 186-192.