Continuing Education Activity

Hip and knee surgery is a common orthopedic surgery among the elderly. In 2010 the prevalence of total hip replacement at fifty years of age was 0.58% and increased to 5.26% at eighty years in the United States (US). This topic concerns the use of PENG Block in patients undergoing hip surgery. There are different regional anesthetic techniques for hip surgery, but this topic will focus on the use of PENG block for hip analgesia. This activity describes and explains the role of the interprofessional team in the management of pre and postoperative pain.

Objectives:

• Describe the technique when performing a pericapsular nerve group (PENG) block.
• Identify the indications for a pericapsular nerve group (PENG) block.
• Summarize the risks and benefits associated with the pericapsular nerve group (PENG) block.
• Outline some interprofessional team strategies that can be employed to ensure optimal outcomes for patients who need a pericapsular nerve group (PENG) block performed.

Introduction

Hip and knee surgery is a common orthopedic surgery among the elderly. In 2010 the prevalence of total hip replacement at fifty years of age was 0.58% and increased to 5.26% at eighty years in the United States (US).[1] A recent US study projected that compared to 2010, annual use of primary knee and hip total joint arthroplasty would increase by 210% (655K to 1375K) and 174% (293K to 512K) in 2020, respectively.[2]

In 2015 the prevalence of total hip arthroplasty was estimated as more than 2.5 million individuals in the entire United States population.[3]

Osteoporosis and osteoarthritis contribute significantly to the surgical indication.

There is a wide diversity in the patient population requiring hip surgery; children with congenital hip dysplasia, young athletic adults who undergo hip arthroscopy, and frail elderly patients with multiple medical problems who experience traumatic accidents following mechanical falls. 7 to 28% of operated patients develop chronic pain after a hip surgery.[4]

Regional anesthesia offers significant benefits in both pain control and recovery in patients undergoing total hip arthroplasties (THA). There is a wide range of regional anesthetic techniques. The most used in this anatomical area and the most supported by published literature are lumbar plexus block, femoral nerve block, and fascia iliaca block. Other techniques, such as selective obturator nerve infiltration and lateral femoral cutaneous nerve blocks, represent alternatives. New approaches have been described, such as quadratus lumborum block and local infiltration analgesia. However, these techniques require rigorous prospective studies.[5][6]

A recent anatomical study on hip innervation has made it possible to identify the relevant landmarks targeted on the hip joint branches from the femoral nerve and the accessory obturator nerve. A new regional anesthesia technique is thus discovered called pericapsular nerve group block (PENG), which targets the anterior capsule of the hip by blocking these nerves.[7]

The PENG block, first described by L Girón-Arango et al., is a novel regional analgesia technique to reduce pain after total hip arthroplasties (THA) while sparing motor function. This technique involves the deposition of the local anesthetic in the fascial plane between the psoas muscle and the superior pubic ramus. This is an interfascial plane block aiming to block articular branches supplied by femoral, obturator, and accessory obturator nerves, and is a promising regional anesthetic technique as an alternative to other regional nerve blocks such as femoral nerve block or an iliac fascia nerve block.[8][7][8]

Anatomy and Physiology

PENG block appears to be the suprainguinal version of the articular branches of the femoral nerve with the added benefit of blocking the accessory obturator nerve along with the obturator nerve. 

The femoral nerve, the longest branch of the lumbar plexus (from the ventral rami of L2-L4 spinal nerves), emerges from the lateral border of the psoas muscle to descend between the iliacus and psoas muscles split into two of its major divisions: anterior and posterior and give motor ( innervation of the flexors of the hip and the extensors of the knee) and sensory branches (innervation of the anteromedial part of the thigh and the medial sides of the leg and foot). The femoral nerve gives birth to a motor branch that it sends to the iliac before passing under the inguinal ligament.

The articular branches at the hip joint originate at a higher level along the course of the nerve. This explains why the femoral block or the fascia iliaca compartment block remains insufficient for hip analgesia.

The obturator nerve is formed from the lumbar plexus (anterior divisions of L2, L3, and L4), descends through the fibers of the psoas major and travels posteriorly to the common iliac arteries and laterally along the pelvic wall to divide into two branches in the obturator canal: anterior and posterior branches. The anterior branch pierces the fascia lata to become the cutaneous branch of the obturator nerve, which supplies the skin of the middle part of the medial thigh.

The accessory obturator nerve is present in 10% to 30% of patients originated from the third and fourth lumbar nerves (derived from the L2 to L4 ventral rami), often innervates the hip joint and adductor longus. The accessory obturator nerve was found to innervate the medial capsule, which has sensory fibers.[9][10]

An anatomic study by Short et al. demonstrated that high branches of both the femoral and obturator nerves (and accessory obturator nerve) provide innervation to the anterior hip capsule because the anterior hip capsule receives the major sensory innervation, whereas the posterior and inferior capsules have no sensory fibers. The hip capsule is divided into 2 parts: anterior and posterior, with nociceptive fibers mostly present on the anterior part while the posterior part has mechanoreceptors.[11]

Their anatomical path through the fibers of the psoas major and the relationship of the articular branches from these three nerves to the inferomedial acetabulum and the space between the anterior inferior iliac spine and iliopubic eminence may suggest potential sites for regional analgesia.

This implies that the deposition of local anesthetics in the fascial plane between the psoas muscle and the upper pubic branch will contribute to anesthesia of these three nerves and, therefore, to analgesic coverage for hip surgery.[12]

Indications

The Pericapsular nerve group (PENG) block is a novel regional analgesia technique that can be used to reduce pain after hip surgery and hip fractures and demonstrated better analgesia compared to other peripheral blocks administered for this type of surgery. It is typically used to provide analgesia following injuries or surgeries of the hip or thigh (e.g., acetabular fractures, femoral neck or mid-shaft fractures, hip replacement, hip arthroscopy, knee surgery)

In a recent report, the author demonstrated effective surgical anesthesia with a PENG block for a medial thigh lesion.[13]

In other studies, the authors describe the use of the block in vascular operations, such as stripping, because the ligation and stripping area was in both the FN and ON dermatomes.[14]

It should be noted that PENG block cannot be offered as the only anesthesia for hip surgery due to the innervation of the posteromedial hip capsule deriving from branches of the sacral plexus and sciatic nerve.[15]

Contraindications

The contraindications for PENG block include:

• Patient refusal
• Infection at the site of injection
• Allergy to local anesthetics
• Systemic anticoagulation (INR >1.5 or inadequate time since cessation of anticoagulant per ASRA guidelines)

Equipment

The peng block is performed under ultrasound guidance and requires the following equipment:

• Ultrasound guidance with the low-frequency curvilinear probe, sterile sleeve, and gel
• One 23 to 25 gauge needle for skin infiltration
• 20 mL of local anesthetic
• Needle size: 80mm B-bevel nerve block needle
• 1 pack of gauze 4-inch x 4-inch
• Chlorhexidine gluconate solution for skin asepsis
• Sterile gloves
• Marking pen

Personnel

The peng block is a regional anesthesia technique that should only be performed by trained physicians. Sedation is recommended for patient comfort. The assistance of a nurse trained in regional anesthesia is beneficial in helping with the performance of the block and administering sedation to the patient.

Preparation

Before the regional nerve block, a preoperative evaluation must be carried out according to WHO guidelines. This evaluation should include medical history, physical examination, airway assessment, and analysis of preoperative tests. The current treatment should also be noted, including the consumption of analgesics along with anticoagulants to minimize the risk of bleeding.

The patient should be informed about the risks and benefits of the PENG block. This involves a detailed description of the procedure to obtain informed consent.

Finally, this procedure should be performed in a clinical center equipped with appropriate monitoring equipment.

Technique or Treatment

The PENG Block is performed only under ultrasound guidance with the low-frequency probe. We distinguish two techniques according to the authors:

Out-of-plane Technique

After adequate premedication, the patient is placed in the supine position, and hip extended. After sterile preparation, an injection of 3 ml of 2% lidocaine at the insertion site using a hyperechoic needle (designed for regional anesthesia) is performed under ultrasound guidance with the low-frequency probe suitable for this type of block. At the level of the anterior superior iliac spine (ASIS), The probe is placed parallel to the inguinal fold, and scanning is performed with a gradual movement of the probe head. When the lower anterior inferior iliac spine (AIIS) is seen, the probe is rotated slightly median until a continuous hyperechoic shadow of the upper pubic ramus is visible. This maneuver allows us to identify The psoas muscle with a prominent tendon just above the pubic ramus. The target is located in the plane between these two structures. The pubic ramus should be aligned in the center of the image to target the pubic ramus just inside the AIIS. A 100 mm nerve block needle can be introduced, and 20 mL with a local anesthetic is administered using the ultrasound-guided out-of-plane technique.[16]

In-plane Technique

The low-frequency curvilinear transducer is placed in the transverse plane over the anterior inferior iliac spine (AIIS) and moved inferiorly to visualize the pubic ramus. The femoral artery and iliopubic eminence are visualized, and then, using an in-plane technique, a 100 mm nerve block needle is advanced from lateral to medial through the skin wheal at a 30-degree to 45-degree angle toward the ultrasound beam, and 20 mL of local anesthetic is deposited between the psoas tendon anteriorly and pubic ramus posteriorly.[12]

Complications

Regional anesthesia techniques require a thorough knowledge of the potential complications associated with a given procedure. The complications associated with peripheral nerve blocks include infection, bleeding, nerve damage, and local anesthetic toxicity. Systemic toxicity of local anesthetics is related to either intravascular injection or an excessive dose beyond the toxic dose limits. Treatment in this emergency includes the immediate administration of intravenous intralipid and hemodynamic supportive measures.

The Second American Society of Regional Anesthesia and Pain Medicine Practice Advisory on Neurologic Complications Associated With Regional Anesthesia and Pain Medicine sheds particular light on the complications associated with mechanical, ischemic, or neurotoxic lesions of the peripheral nervous system.

Since the PENG block is a new regional anesthesia technique, we do not have enough epidemiological studies to describe the main specific complications of this type of block.

Thanks to the practice of PENG block only under the ultrasound-guided technique, the risk of femoral nerve damage or vascular damage (with hematoma) remains extremely rare at the current time. The incidence of long-term peripheral nerve damage represents 2 to 4 cases per 10,000 peripheral nerve blocks of all types.[17]

Clinical Significance

The PENG block is a new and alternative regional analgesic technique for hip surgery that can be used in combination with other regional anesthesia techniques to effectively target the anterior hip capsule by blocking the articular branches of the femoral nerve and accessory obturator nerve and also used as an alternative to femoral nerve block or lumbar plexus block to prevent quadriceps weakness and thus allow early postoperative revalidation.

It is currently well described that the use of multimodal analgesia combined with regional analgesia, including nerve blocks and periarticular infiltration techniques, is associated with the decreased postoperative use of opioids and improved by reducing morbidity and length of hospital stay.

To evaluate the efficacy of PENG block for hip surgery, a review was carried out using the Joanna Briggs Institute framework; adult and pediatric studies were included, database searches identified 345 articles, but the author concluded that current evidence of using PENG block for hip surgery or hip pain is limited to case reports and case series only. Regarding analgesic efficacy and adverse effects, double-blind, randomized controlled trials are required to better understand the PENG block.[8]

In a retrospective review that compares the analgesic benefit of adding PENG block to Local infiltration anesthetic after primary total Hip arthroplasty, the authors (Kiran Mysore MD et al.) identified 123 patients who met the inclusion criteria; 47 received and 76 did not receive PENG block. They find that the PENG block was associated with a reduction in 24-hour hydromorphone consumption.[18]

Following Girón et al.'s publication, which was the first author to discover this block, Ueshima and Otake documented their clinical experience using the PENG technique in four patients for the management of perioperative pain after reduction of hip dislocation and hip replacement; they concluded that in their successful experience, the PENG block technique could cover both the femoral and obturator nerves and could be used as an effective analgesic method for hip surgery.[19][20]

Enhancing Healthcare Team Outcomes

The preoperative, intraoperative, and postoperative management of acute pain following hip surgery involves interprofessional and multidisciplinary teams.  

An anesthesiologist with a specialization in regional anesthesia typically performs the PENG block with a nurse's assistance. Communication in this setting is essential for providing optimal care for the patient. Time out should be performed confirming the patient's name, the procedure that is being performed, and the surgical site should be marked prior to beginning the procedure. Sterile technique should be maintained, along with preparation in the event of an emergency.

All involved team members should be familiar with emergency situations that can occur during these procedures and should be able to assist in the event an emergency arises.

Postoperatively, the training of the nursing and surgical team for the assessment of pain (VAS, NRS, etc.) and pain control strategies is essential for the patient's recovery.

Nursing, Allied Health, and Interprofessional Team Interventions

A nursing team qualified for the operating room, and postoperative pain management is necessary and required to perform regional anesthetic procedures safely.

Nursing, Allied Health, and Interprofessional Team Monitoring

The PENG block must be performed like the practice of any regional anesthetic procedure. The ideal location is within a hospital center equipped with cardiovascular and respiratory monitoring equipment to ensure optimal monitoring of vital parameters and to be able to properly resuscitate in the rare event that it is needed.