ABSTRACT:

OBJECTIVE To evaluate the technical reproducibility of a block of the pericapsular nerve group (PENG) of the hip aided or not by ultrasound in cadavers.
MATERIALS AND METHODS The present is a randomized, descriptive, and comparative anatomical study on 40 hips from 2 cadaver groups. We compared the PENG block technique with the method with no ultrasound guidance. After injecting a methylene blue dye, we verified the dispersion and topographical staining of the anterior hip capsule through dissection. In addition, we evaluated the injection orifice in both techniques.
RESULTS In the comparative analysis of the techniques, there were no puncture failures, damage to noble structures in the orifice path, or differences in the results. Only 1 hip from each group (5%) presented inadequate dye dispersion within the anterior capsule, and in 95% of the cases submitted to either technique, there was adequate dye dispersion at the target region.
CONCLUSION Hip PENG block with no ultrasound guidance is feasible, safe, effective, and highly reliable compared to its conventional counterpart. The present is a pioneer study that can help patients with hip pain from various causes in need of relief.

Keywords: analgesia; anesthesia; hip joint; nerve block; cadaver; peripheral nerve injuries.

RESUMO:

OBJETIVO Propor e avaliar a reprodutibilidade técnica do bloqueio do grupo de nervos pericapsulares (pericapsular nerve group, PENG, em inglês) do quadril sem o auxílio da ultrassonografia, em cadáveres, de forma comparativa à realização do bloqueio guiado pela ultrassonografia em outro grupo de cadáveres.
MATERIAIS E MÉTODOS Estudo anatômico randomizado, descritivo e comparativo, realizado em 40 quadris divididos em 2 grupos amostrais de cadáveres. Fez-se uma comparação da técnica do bloqueio do PENG à técnica não guiada por ultrassonografia injetando-se corante azul de metileno, seguida de dissecção para verificação da dispersão e da coloração topográfica da cápsula anterior do quadril, além de avaliação do pertuito das injeções entre as técnicas.
RESULTADOS Na análise comparativa das técnicas, não houve falha na punção, lesão de estruturas nobres no pertuito, ou diferença nos resultados. Não houve adequada dispersão do corante pela cápsula anterior somente em 1 quadril de cada grupo (5%), e em 95% dos casos submetidos a qualquer uma das técnicas observou-se dispersão adequada do corante pela região alvo.
CONCLUSÃO O bloqueio do PENG do quadril sem auxílio de ultrassonografia é factível, seguro, eficaz, e com alta confiabilidade quando comparado à sua realização guiada pelo aparelho de imagem. Este estudo é pioneiro, e pode ajudar muito os pacientes que têm dor no quadril por diversas causas e necessitam alívio.

Palavras-chave: analgesia; anestesia; articulação do quadril; bloqueio nervoso; cadáver; traumatismos dos nervos periféricos.

FIGURES

Citation: Hamra P, Sau AS, Ricioli Junior W, Rabelo NDA, Polesello GC. Block of the Pericapsular Nerve Group of the Hip with and without Ultrasound Guidance: Comparative Cadaveric Study*. 58(4):e646. doi:10.1055/s-0042-1758367
Financial Support: The authors declare that they have received no financial support for the research, authorship and/or publication of the present article.

Conflict of Interests: The authors have no conflict of interests to declare.
*Study performed at the Hip Group, Department of Orthopedics and Traumatology, Faculdade de Ciências Médicas, Santa Casa de Misericórdia de São Paulo (FCMSCSP), São Paulo, SP, Brazil.
Received: August 03 2022; Accepted: September 12 2022
 

INTRODUCTION

The anterior joint capsule of the hip receives most of the sensory innervation from the entire joint.1 Anatomical studies2,3,4 have revealed that this sensory innervation comes from branches of the femoral, obturator, and accessory obturator nerves.

In 2018, Girón-Arango et al.5 described, a technique to block the pericapsular nerve group (PENG) of the hip, which consists of the infusion of an anesthetic agent guided by ultrasound (US). Using someanatomical reference points and US images, this technique aims to reach the anterior capsule of the hip and its sensory nerve branches for anesthetic dispersion.1

The PENG block has been described for pain management, either for analgesia after proximal femur fractures, or pain control after hip surgeries. With a low cost and good outcomes, it prevents the use ofopioids and their side effects.5,6,7,8

Although originally aided by US to guide the injection and anesthetic infusion, one of the orthopedist’s challenges with the PENG block technique is the availability of the US equipment in all sectors and levels of care.

Therefore, we propose a PENG block with no US guidance. Our objective was to analyze the outcomes of the PENG block based only on anatomical parameters and compare them to the conventional, US-guided technique.

A PENG block with no US guidance could be part of several strategies, including preoperative care, pain management, follow-up, and postoperative care with less need for special equipment.

 

MATERIALS AND METHODS

The present is a randomized, descriptive, and comparative anatomical study conducted at the Hip Group of a teaching hospital and performed in the Capital City’s Death Verification Service (Serviço de Verificação de Óbitos da Capital, SVOC, in Portuguese), of the City of São Paulo, Brazil. The study team is duly registered at SVOC under number 18/2022, and the study followed its guidelines. The institutional ethics committee approved the study (CAAE 58212220.9.0000.5479).

The present study included a sample of 20 cadavers, with 40 hips not preserved with formalin. We excluded four subjects with skeletal immaturity from the analysis.

Procedures

In a parallel study, Tran et al.9 performed a technical comparison of infusions of 10mL and 20 mL of methylene blue dye in cadaveric hips. They concluded that, although the dispersion of 20mL was more extensive, both injections stained the entire region between the iliopsoas and the anterior capsule of the hip, in which Gerhardt et al.1 identified nociceptive nerve branches.

In the present study, we used 20 mL of methylene blue dye to also mimic the anesthetic block originally described by Girón-Arango et al.5 Next, we performed an anatomical dissection to determine the appearance and dye dispersion within the anterior capsule region and compare both methods.

In group 1 (G1), which was randomly composed of the first 10 cadavers (20 hips), we followed the proposed anesthetic block technique,5 but taking as parameters only the local anatomical structures herein described, with no direct visualization of adjacent structures using a US equipment. In group 2 (G2), which was also composed of 10 cadavers (20 hips), we performed the conventional US-guided infiltration technique.

Infiltration Technique

We placed the cadaver in horizontal dorsal decubitus (HDD), with no traction, and the hip in a neutral position. The G1 underwent infiltration with no US guidance as follows:

  • Identification by palpation of the anterosuperior iliac spine (ASIS) and the pubic symphysis (PS), drawing a straight line between these points.
  • Segment division in three equal portions and marking of the midpoint of the lateral third as the needle entry point (►Fig. 1).
  • Positioning of a disposable needle for spinal anesthesia (0.7 × 88 mm, 22 G × 3.5”, Spinocan, B. Braun, Melsungen, Germany) at the demarcated point, approximately 1 cm from the medial edge of the ASIS. The needle was inclined at 70° in the inferior medial direction and towards the midpoint of the line connecting the ASIS to the PS (►Fig. 2).
  • The needle is introduced until it touches the bone.
  • Needle is receded for about 1 mm and slow, continuous infiltration of 20 mL of methylene blue is performed.
Fig. 1. Demarcated segment between the anterosuperior iliac spine (ASIS) and the pubic symphysis (PS).
Fig. 2. Needle insertion at a 70° of inclination at the midpoint of the lateral third.

The US-assisted technique, to which the G2 was submitted, consists of the following:

  • With the patient in HDD, we positioned a low-frequency (2-5 MHz) convex US probe (Sonosite Edge II, Fujifilm Healthcare, Lexington, MA, United States) over the midpoint of the lateral third of the segment marked in ►Fig. 1 in a transverse plane with 45° counterclockwise rotation of the PS (►Fig. 3).
  • Visualizing the iliopsoas tendon and muscle, and the femoral artery and vein, we inserted a needle with the same specification up to the plane between the iliopsoas structures anteriorly and the iliopubic branch, with the iliopectineal eminence posteriorly (►Fig. 4).
  • We infused 20 mL of methylene blue in the region.
  • We dissected the region and analyzed the correlation and distance between the needle and local significant structures in both techniques.
Fig. 3. Probe positioning in the midpoint of the demarcated segment, with the PS at 45° of inclination.
Fig. 4. Ultrasonographic image of the needle path (arrow). Abbreviations: ASIS, anteroinferior iliac spine; FA, femoral artery; FV, femoral vein; IPB, iliopubic branch; PT, iliopsoas muscle tendon.

Infiltration Analysis

We determined the reliability of the injection per the number of puncture attempts to reach the expected location of the needle at the iliopectineal eminence of the iliopubic branch.

We dissected the anterior region of the hip using a quadrangular skin flap whose apex is on the line from the ASIStothe PS andthebase is betweentheinferior gluteal fold and the midline of the thigh, extending along the antero-lateral aspect of the hip (►Fig. 5). After dissection, we identified the ASIS, the anteroinferior iliac spine (AIAI), the inguinal ligament, the femoral neurovascular bundle, the joint capsule, and the iliopsoas tendon and muscle.

Fig. 5. Quadrangular skin flap for dissection.

After identifying the aforementioned anatomical structures, we evaluated the integrityof the neurovascular bundle due to potential lesions related to a path error and their correlations with the orifice. In addition, we determined the dispersion of the methylene blue dye within the desired plane and the anterior capsule staining to compare the effectiveness of both techniques (►Fig. 6).

Fig. 6. Rectus femoris (RF) muscle retracted for better visualization of the methylene blue dispersion and anterior capsule staining..

Results

The G1 consisted of 8 male (80%) and 2 female (20%) cadavers with a mean age of 70 years and 2 months, a mean weight of 59 Kg, and a mean height of 168cm. ►Table 1 shows the data from this analysis (►Figs. 7 and 8).

Table 1. Anthropometric data from the group submitted to the technique with no ultrasound guidance
Identification Gender Age (years) Height (meters) Weight (kilosg)
C1 Male 70 1.73 46
C2 Female 77 1.44 44
C3 Male 69 1.76 85
C4 Male 93 1.63 49
C5 Male 64 1.68 55
C6 Female 62 1.73 60
C7 Male 48 1.66 69
C8 Male 52 1.7 71
C9 Male 78 1.76 68
C10 Male 89 1.7 43

Abbreviation: C, cadaver.

Table 1. Anthropometric data from the group submitted to the technique with no ultrasound guidance
Fig. 7. Right hips from the group submitted to the technique with no ultrasound guidance, showing all capsules stained. Abbreviations: C1 to C10, cadavers 1 to 10.
Fig. 8. Left hips from the group submitted to the technique with no ultrasound guidance, showing all capsules stained. Abbreviations: C1 to C10, cadavers 1 to 10.

The G2 consisted of 6 male (60%) and 4 female (40%) cadavers with a mean age of 68 years and 6 months, a mean weight of 72.6 Kg, and a mean height of 169cm. ►Table 2 shows the data from this analysis (►Figs. 9 and 10).

Table 2. Anthropometric data from the group submitted to the technique with ultrasound guidance
Identification Gender Age (years) Height (meters) Weight (kilos)
C11 Male 70 1.72 69
C12 Female 94 1.55 45
C13 Male 45 1.77 57.6
C14 Male 71 1.77 102
C15 Female 79 1.67 87
C16 Male 82 1.75 75
C17 Male 49 1.71 74
C18 Female 50 1.71 72
C19 Male 65 1.71 81
C20 Female 81 1.55 64

Abbreviation: C, cadaver.

Table 2. Anthropometric data from the group submitted to the technique with ultrasound guidance
Fig. 9. Right hips from the group submitted to the technique with ultrasound guidance, showing no capsule staining. Abbreviations: C11 to C20, cadavers 11 to 20.
Fig. 10. Left hips from the group submitted to the technique with ultrasound guidance, showing no capsule staining. Abbreviations: C11 to C20, cadavers 11 to 20.

In the comparative analysis of the dissections, 1 hip from each group (5%) did not show adequate dye dispersionwithin the anterior capsule. Both techniques led to the expected location of the needle next to the iliopectineal eminence in the first puncture. There was no lesion, transfixion, or dye staining in neurovascular structures adjacent to the anterior capsule. ►Tables 3 and 4 show the data from this analysis.

Table 3. Puncture data and dissection analysis from the group submitted to the technique with no ultrasound guidance
Identification Bone reached at first puncture Neurovascular bundle hit Right anterior capsule staining Left anterior capsule staining
C1 Yes No Yes Yes
C2 Yes No Yes Yes
C3 Yes No Yes Yes
C4 Yes No Yes Yes
C5 Yes No Yes Yes
C6 Yes No Yes Yes
C7 Yes No Yes Yes
C8 Yes No Yes Yes
C9 Yes No Yes Yes
C10 Yes No Yes No

Abbreviation: C, cadaver.

Table 3. Puncture data and dissection analysis from the group submitted to the technique with no ultrasound guidance
Table 4. Puncture data and dissection analysis from the group submitted to the technique with ultrasound guidance
Identification Bone reached at first puncture Neurovascular bundle hit Right anterior capsule staining Left anterior capsule staining
C11 Yes No Yes Yes
C12 Yes No No Yes
C13 Yes No Yes Yes
C14 Yes No Yes Yes
C15 Yes No Yes Yes
C16 Yes No Yes Yes
C17 Yes No Yes Yes
C18 Yes No Yes Yes
C19 Yes No Yes Yes
C20 Yes No Yes Yes

Abbreviation: C: cadaver.

Table 4. Puncture data and dissection analysis from the group submitted to the technique with ultrasound guidance

There was no difference between the techniques regarding these parameters. We obtained an adequate dye dispersion at the expected region in 95% of the cases in each group.

 

DISCUSSION

The proposed technique with no US guidanceshowed similar results to the PENG block technique aided by US, with no variations between them.

The failure in staining a single anterior capsule in each group occurred in the specimens with the lowest weight (43 Kg and 45 Kg) and oldest ages (89 and 94 years) among the remaining cadavers. This finding may result from the tissue atrophy inherent to advanced age and the smaller space between tissue planes in subjects with lower weights, which impair the effectiveness of the block using a liquid anesthetic dispersion.3

The pioneer study can help patients with hip pain of various causes in need of relief. It is worth mentioning that the technique with no US guidance is technically easy and cheap. Since it can be performed with basic hospital materials and supplies, it constitutes a viable alternative in situations with limited access to US equipment in different sectors and levels ofcare. In addition, it may be a good option for analgesia, preventing theuse oforalopioids andtheir side effects.5,6

The limitation of the present study is the use of cadaveric specimens, which may present tissue and anatomical plane changes despite the recent post-mortem period.

 

CONCLUSION

The proposed methodof hip PENGblock withno US guidance is reproducible, safe, effective, and highly reliable when compared with the US-guided technique.

 

REFERENCES

1
Gerhardt M, Johnson K, Atkinson R, et al. Characterisation and classification of the neural anatomy in the human hip joint. Hip Int 2012;22(01 ):75-81
2
Wertheimer LG. The sensory nerves of the hip joint. J Bone Joint Surg Am 1952;34-A(02):477-487
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Birnbaum K, Prescher A, Hessler S, Heller KD. The sensory innervation of the hip joint-an anatomical study. Surg Radiol Anat 1997;19(06):371-375
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Gardner E. The innervation of the hip joint. Anat Rec 1948;101 (03):353-371
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Girón-Arango L, Peng PWH, Chin KJ, Brull R, Perlas A. Pericapsular Nerve Group (PENG) Block for Hip Fracture. Reg Anesth Pain Med 2018;43(08):859-863
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Acharya U, Lamsal R. Pericapsular nerve group block: an excellent option for analgesia for positional pain in hip fractures. Case Rep Anesthesiol 2020;2020:1830136
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GuayJ, Kopp S. Peripheral nerve blocks for hip fractures in adults. Cochrane Database Syst Rev2020;11(11):CD001159
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Beaudoin FL, Haran JP, Liebmann O. A comparison of ultrasound-guided three-in-one femoral nerve block versus parenteral opioids alone for analgesia in emergency department patients with hip fractures: a randomized controlled trial. Acad Emerg Med 2013;20(06):584-591
9
Tran J, Agur A, Peng P. Is pericapsular nerve group (PENG) block a true pericapsular block? [published online ahead of print, 2019 Jan 11]Reg Anesth Pain Med 2019;•••:rapm-2018-100278