Reply to Dr Nielsen: Pericapsular Nerve Group (PENG) block for hip fracture

Pericapsular nervegroup (PENG) block—a scoping review

The obturator nerve and its accessory branch supplying the hip region, unlike the femoral nerve, are not adequately anaesthetized by conventional regional anaesthetic techniques targeting the hip region. With advancements in ultrasound-guided regional anaesthetic techniques, interests are revived in the field and efforts are being made to block them together. One such successful attempt is the novel peri-capsular nerve group (PENG) block. Consequently, further research on the PENG block began to explore its versatilities. The present study undertakes a scoping review of research on the PENG block in humans for any indication to determine the extent of the research done, the methodologies used, and other practical issues addressed in the research. This will help to identify potential research gaps that should be addressed in the future. PubMed, Google Scholar, Cochrane Library, KoreaMed, Latin American and Caribbean Health Science Literature, and the directory of open access journals were searched with the keyword “PENG block” and “pericapsular nerve group”. Manual search of electronically retrieved papers was also carried out. Among the 67 articles selected in our review, eighteen are case series; twenty-nine are case reports; two are randomized studies; one each of prospective cohort study, review, and cadaveric study; and 15 are editorials. However, only 64 articles were included later due to the retraction of three case reports. Data is insufficient to provide firm recommendations for or against different aspects of the block. The review encourages future work addressing different aspects of the PENG block.

Pericapsular Nerve Group Block and Iliopsoas Plane Block: A Scoping Review of Quadriceps Weakness after Two Proclaimed Motor-Sparing Hip Blocks

Iliopsoas plane (IP) is a fascial plane deep to the iliopsoas complex that can serve as a potential space for the injection of local anesthetics to selectively block the articular branches of femoral nerve and accessory obturator nerve to the anterior hip capsule. Two highly similar ultrasound-guided interfascial plane blocks that target the IP, pericapsular nerve group (PENG) block and iliopsoas plane block (IPB), were both designed to achieve motor-sparing sensory block to the anterior hip capsule. However, the most recent evidence shows that PENG block can cause 25% or more of quadriceps weakness, while IPB remains the hip block that can preserve quadriceps strength. In this scoping review of quadriceps weakness after PENG block and IPB, we first performed a focused review on the complicated anatomy surrounding the anterior hip capsule. Then, we systematically searched for all currently available cadaveric and clinical studies utilizing PENG block and IPB, with a focus on quadriceps weakness and its potential mechanism from the perspectives of fascial plane spread along and outside of the IP. We conclude that quadriceps weakness after PENG block, which places its needle tip directly deep to iliopsoas tendon (IT), may be the result of iliopectineal bursal injection. The incidental bursal injection, which can be observed on ultrasound as a medial fascial plane spread, can cause bursal rupture/puncture and an anteromedial extra-IP spread to involve the femoral nerve proper within fascia iliaca compartment (FIC). In comparison, IPB places its needle tip lateral to IT and injects just one-fourth of the volume of PENG block. The current evidence, albeit still limited, supports IPB as the true motor-sparing hip block. To avoid quadriceps weakness after PENG block, a more laterally placed needle tip, away from the undersurface of IT, and a reduction in injection volume should be considered. Future studies should focus on comparing the analgesic effects and quadriceps function impairment between PENG block and IPB.

Pericapsular nerve group block: an overview

INTRODUCTION

The PENG block is a recently described ultrasound-guided technique for the blockade of the sensory nerve branches to the anterior hip joint capsule. It was described as an analgesic block for the acute pain management after hip fracture, while subsequent studies expanded the original indication. The aim of this narrative review was to summarize the existing knowledge about the PENG block from the anatomical bases and to provide an up-to-date description of the technique, applications and effects.

EVIDENCE ACQUISITION

We reviewed the following medical literature databases for publications on PENG block: PubMed, Google Scholar, EMBASE, and Web of science until August 31st, 2020. Data regarding anatomy, indications, drugs and technique were also collected, reported and discussed.

EVIDENCE SYNTHESIS

From our search result we selected 57 relevant publications. Among them, 36 were case reports or case series and 12 publication were letters or correspondence; no RCT was identified. The main indication is the hip-related analgesia. The most commonly injected drug is a 20ml long-acting local anesthetic. There are some cases of femoral and obturator nerve block, but no major complication such as hematoma/bleeding or needle-related organ injury has been reported yet.

CONCLUSIONS

The PENG block is a promising technique. Randomized controlled trials of high methodological quality are required to further elaborate the role of this block.