European Journal of Cardiovascular Medicine

Hip fracture is a common orthopedic emergency in the elderly & is associated with significant morbidity and mortality; surgical reductions and fixations are the definitive treatments in most patients. Hip Fixation is a common operative procedure to improve mobility and quality of life.

Traditionally, postoperative analgesia was provided by intravenous patient-controlled analgesia or epidural analgesia. Recently, peripheral nerve blockade has emerged as an alternative analgesic approach¹. Lately, ultrasound-guided fascia iliaca block (supra-inguinal approach) has emerged as a dependable analgesic option in hip surgeries with respect to positioning for spinal anesthesia, pain control, and opioid consumption^2,3,4.

Pericapsular nerve group (PENG) block has recently been recommended by Girón-Arango et al. in 2018; for use as postoperative analgesia in hip surgeries⁵. It is a new regional anesthesia method based on blocking the articular branches of the femoral nerve (FN) and accessory obturator nerve (AON) in the region between the anterior inferior iliac spine (AIIS) and iliopubic eminence (IPE).

These peripheral nerve block techniques have been found to be associated with improved early ambulatory outcomes and reduced motor blockade.

This randomised, double-blind, prospective controlled trial was undertaken following approval from the Institutional Ethics Committee (IEC) between November 2019 to October 2021 in the Department of Anaesthesiology, Lady Hardinge Medical College and Associated Hospitals, New Delhi. The trial is registered with the Clinical Trial Registry – India (CTRI) (trial registry number: Trial REF/2020/02/031294).

In total, 80 patients aged 18-60 years of either sex with American Society of Anaesthesiologists (ASA) physical status 1 and 2 undergoing hip fixation surgery under spinal anesthesia were included in the study. The exclusion criteria were the patient’s refusal to participate, any contraindications to SA or peripheral nerve blocks, and patients with significant cognitive impairment. Written informed consent was taken from each patient included in the study, explaining that each one will be followed up for a minimum of 48 hours after surgery.

Pre-anesthetic medication was administered in the form of alprazolam 0.25 mg orally on the night prior and on the morning of surgery. In the preoperative room, patients were explained about the Numerical Pain Rating Scale (NRS) for postoperative pain evaluation. Patients were randomly allocated into one of the two groups by using a computer-generated random numbers table. Allocation concealment was done by using sequentially numbered opaque envelopes; these were used to assign randomisation on the day of surgery. Anesthesiologists, surgeons, and patients were blinded to the patient allocation.

A total of 80 patients were randomly divided into two equal groups:

In Group 1 (n = 40), patients received ultrasound‑guided Pericapsular Nerve Group Block. In Group 2 (n = 40), patients received ultrasound‑guided fascia iliaca block.

PERFORMANCE OF NERVE BLOCKS

For all cases, a catheter-through-needle kit was used (Contiplex Tuohy, B. Braun Melsungeon, Germany) with a 10 cm long/18 G Tuohy introducer needle and a 0.45 × 0.85 × 1000 mm catheter. For group 1, the anatomical landmarks and techniques used were the same as the ones described by Girón-Arango et al. Once the introducer needle was placed in the plane between the iliopsoas tendon and periosteum and between the anterior inferior iliac spine (AIIS) and iliopubic eminence (IPE), the PENG block was performed. For group 2, the shadow of the bone of the iliac crest & iliacus muscle was seen then the 18 GUAGE Tuohy’s needle was introduced and was kept deep to the fascia iliaca and above the lateral part of the iliacus muscle.  by injecting 20 mL of the local anesthetic. The local anesthetic injected consisted of 20 ml of 0.25% bupivacaine. A flexible 19G Epidural style catheter was threaded and advanced 2-3 cm beyond the needle tip under direct visualization of the ultrasound. The needle was removed and the catheter was secured using adequate occlusive dressing.

NRS of all the patients was recorded after the application of the respective block and during the position for spinal anesthesia. All patients included in the study underwent sub-arachnoid block for intraoperative anesthesia with 0.5% bupivacaine with anhydrous dextrose (80mg/4ml).

An electronic infusion pump (Perfusor ® compact plus – B. Braun) was started after the induction of spinal anesthesia. The infusion was set initially at the rate of 8ml/hr of 0.125% bupivacaine and continued for the next 48 hours.

Pain assessments were done at 0,4,8,12 and 24 hours postoperatively using NRS scores both at rest and on movement. The pain at rest (static pain) was defined as pain in the patient’s chosen position for best comfort while the pain on movement (dynamic pain) was defined as pain on a passive elevation of the operated leg to approximately 15 degrees.

POST-OPERATIVE ANALGESIC REGIMEN

Patients were instructed to ask for rescue opioid analgesics if they report pain of NRS 4 or more with IV tramadol 2mg/kg. Any additional opioid used post-operatively was noted.

Any complications (nausea, vomiting, pruritis, catheter displacement, or hematoma at the site of injection) were noted.

The nerve block catheters were removed under all aseptic precautions after completion of post-operative 48 hrs.

PRIMARY OBJECTIVES

Our primary objective was to study postoperative analgesia using Numerical Rating Scale (NRS) at rest and in movement in patients with Fascia Iliaca block and PENG block undergoing hip fixation surgery at 0,4, 8, 12, and 24 hours.

SECONDARY OBJECTIVES

The secondary objective was the assessment of the mean difference in NRS at positioning for spinal anesthesia after the administration of nerve blocks. The objectives also included the calculation of the total analgesic requirement postoperatively for 24 hours as well as the evaluation of any catheter-related or drug-related complications.

SAMPLE SIZE DETERMINATION

 According to the study by Shariat et al.⁴; the reduction in NRS scores occurred from 7.2 ± 2.5 to 4.8 ± 2.4 in 24 hours post fascia iliaca block Considering the alpha error of 0.5 and power of study as 84%, the sample size according to the formula

                              N=[Z(1-α/2) + Z(1-β)]²  x [(SD₁) + (SD₂)]² / (Δμ)² 

Where;

N is the sample size, α is an alpha error, 1-β signifies the power of the study, SD is the standard deviation and Δμ is the difference in means

                                                            N= 32.68 per block

33 comes out to be the minimum sample size per block therefore we will enroll 40 patients in each group

STATISTICAL ANALYSIS

The categorical variables were presented in the form of numbers and percentages (%). On the other hand, the quantitative data were presented as the means ± SD as the median with 25th and 75th percentiles (interquartile range). The following statistical tests were applied to the results:

1. The comparison of the variables which were quantitative in nature were analysed using an independent t-test. Paired t-test was used for the comparison of NRS across follow-up.

2. The comparison of the variables which were qualitative in nature were analysed using the Chi-Square test. If any cell had an expected value of less than 5, Fisher’s exact test was used. The data entry was done in the Microsoft EXCEL spreadsheet and the final analysis was done with the use of Statistical Package for Social Sciences (SPSS) software, IBM manufacturer, Chicago, USA, version 21.0. For statistical significance, a p-value of less than 0.05 was considered statistically significant.

CONSORT flow diagram. PENG, pericapsular nerve group block; FIB, Fascia iliaca block.

Out of 100 patients assessed for inclusion, 80 were enrolled in the study and 20 were excluded. 40 in each group were randomized. Demographic characteristics and surgical duration are presented in Table 1.

                              Table 1: Demographic characteristics and surgery duration

The mean pre-operative NRS in group 1 was 8.8 ± 0.9 which got reduced to a mean of 1.2 ± 0.94 during positioning for spinal anesthesia. Similarly, the mean pre-operative NRS in group 2 was 9.05 ± 0.81 that got reduced to a mean of 3.025 ± 0.86 during positioning for spinal anesthesia. Thus, the mean difference in NRS after 15 minutes of block in group 1 was 7.6 ± 1.34 and in group 2 was 6.025 ± 1.1. The total mean difference in NRS was 6.81 ± 1.45 and the difference between the two groups is statistically significant (p-value <0.0001)..

The mean NRS in group 1 at 24 hours of receiving a continuous infusion of 0.125% bupivacaine at 8ml/hr was 0.08 ± 027 at rest and 0.65 ± 0.66 on movement whereas in Group 2 the mean NRS was 0.8 ± 0.65 at rest and was 2.38 ± 0.84 on movement. Thus, ultrasound-guided PENG block resulted in a better analgesic efficacy than FIB at 24 hours postoperatively both at rest and at movement (p-Value <0.001).

Compared with FIB, the PENG block resulted in a lower NRS score at all time intervals.

Table 2: Comparison of pre-op and post-op NRS between two groups

Patients who were administered PENG block consumed lesser total opioids than those who were administered FIB (9.75 mg morphine equivalents v/s 18.25 mg morphine equivalents; P value<0.0001).

No complications were encountered in any of the patients in group 1 while 17.5% of patients in Group 2 complained of nausea and vomiting during the observation period.

Pain management is a key component for hip fracture patients. Opioids are often used in hip fracture surgery and provide adequate analgesia but they are associated with nausea, constipation, and delirium^6,7. Regional blockade techniques such as femoral nerve block, and fascia iliaca block are usually utilized for pain control in these patients; due to an opioid-sparing effect are relatively safer⁸. Motor weakness is a major limitation associated with these methods. PENG block is a new approach to hip analgesia whose effectiveness has not been instituted yet⁵. Therefore, the current study was constructed to assess the usefulness of the PENG block in the control of hip fracture pain as well as to compare the PENG block with the fascia iliaca block with respect to analgesia and side effects. Our results showed that the PENG block significantly diminished pain scores in hip fracture patients and has more efficacy in pain management compared with the FIB.

The hip joint and the overlying skin have an extensive nerve supply that includes Femoral Nerve (FN), Obturator Nerve (ON), Accessory Obturator Nerve (AON), and laterally Lateral Femoral Cutaneous Nerve (LFCN)^9,10. The posterior hip capsule is innervated by the Sciatic nerve. The nociceptor density is more on the anterior aspect of the hip joint¹¹. Histologically, the anterior capsule has predominantly nociceptive fibres¹² while the posterior capsule is largely made up of mechanoreceptors¹³ and has no sensory fibres.

In this randomized controlled trial, we found that compared to scoring before blocking, continuous PENG block reduced the NRS pain scores by 8 points at 24 hours post-surgery (movement) while continuous FIB reduced it by almost 6 points at the same time periods.

The results suggested that patients who received PENG block had demonstrated significantly lower NRS scores and less opioid consumption during and after surgery than those who received FIB. Positioning the patient for the sub-arachnoid blockade was easier in patients who received PENG block as they showed better NRS scores compared to those who received FIB.

Fascia iliaca block (FIB) caused a nominal reduction in the pain scores in patients following THA in a study by Shariat et al.³ and most of the patients experienced the pain of moderate intensity in the immediate post-block period and at 24-hour intervals. In contrast to the results of Shariat et al., in another study by Desmet et al.⁴ significant reduction in pain scores, in patients following THA, was reported at 0, 1, 2,4, and 24 hours post-operatively when 40ml of 0.5% ropivacaine was injected underneath fascia iliaca via supra inguinal approach. Azizoglu M et al.¹⁴ also reported S-FIB (25-40 ml 0.25% bupivacaine) provided better analgesia than PCA after hip surgeries in elderly patients. The pain scores were significantly lower in the fib group at all intervals till 24 hours. Yu B et al.¹⁵ demonstrated that ultrasound-guided continuous FIB provided better analgesia as compared to ultrasound-guided FNB (p<0.05) at 6 hours post-operative intervals.

The first published study to evaluate the efficacy of the PENG Block after THA by Pascarella G et al.¹⁶ displayed lower pain scores in the PENG block group as compared to the control group at all time points (P<0.001). A comparative trial between the PENG block and FN block by Lin D.Y et al.¹⁷ demonstrated significantly lower pain scores at the 4-hour interval in the recovery room in the PENG group (p=0.04). Single-shot PENG block has been studied adequately as an alternative technique for analgesia in hip fractures but the literature is scarce to date on the placement of peripheral nerve catheters for continuous PENG block. To date, only a few case series have been published on continuous PENG block for the management of postop analgesia after hip fracture surgery. Buono R et al.¹⁸ in their initial experience with continuous PENG block in 10 cases of hip fracture surgeries reported a good pain relief post-blockade with significantly low NRS scores at 12 and 24 hours. Similar findings were also observed by Wyatt K et al.¹⁹, in which continuous PENG block resulted in optimal analgesia of a 9yr old female who underwent surgical fixation for transcervical hip fracture. Continuous PENG block has also been used in patients undergoing THA and has been found to provide effective analgesia in the postoperative period both at rest and during movement²⁰.

The spread of LA after the PENG block has been studied in cadaveric studies. Ciftci B et al. ²¹ showed the spread of dye below the tensor fascia lata, throughout the iliopsoas, vastus medialis, and gluteus medius muscles when 30ml of the dye was given below the psoas tendon. The spread over tensor facia lata explained the blockade of LFCN and consequently analgesia at the surgical site incision. Altinpulluk et al.²² in a cadaveric study, upon administering incremental volumes of dye below the psoas tendon concluded that the dye reached cranially to the iliopsoas muscle and caudally up to the iliofemoral ligament laterally, the pubofemoral ligament medially and the iliopsoas tendon and his bursa anteriorly and progressively extended down to its insertion on the lesser trochanter and reached the joint space getting accumulated in the lower joint recess. The injectate also advanced to the posterior aspect of the hip joint and thus the part of the sciatic nerve can be covered. Thus, the high analgesic power of this block can be explained as it reaches the joint space and the posterior aspect of the hip joint. Ahiskalioglu A et al.²³ administered 30 ml of LA via PENG block and concluded that sensory loss occurred in the region supplied by LFCN.

The findings of our study could be explained by the above-mentioned studies. FIB resulted in only moderate pain relief for hip surgery and thus leading to higher NRS pain scores while positioning for spinal anesthesia. The reason for that lies in both magnetic resonance and autopsy studies confirming that FIB could not cover the obturator nerve. In contrast, PENG targets the obturator nerve and accessory obturator nerve specifically, as was demonstrated in a cadaveric study. The lowering of postop NRS pain scores in both groups can be explained on account of continuous infusion of 8 ml/hr of 0.125% bupivacaine; which must have acted as a large volume block; was started before the incision and was continued in the postoperative period. PENG block resulted in superior analgesia and lower post-operative opioid consumption as A PENG block targets the nerves that supply the hip joint and the surrounding tissues, whereas a FIB targets the nerves that supply the hip joint, the thigh, and the lower leg. Another difference is the location of the injection. A PENG block is performed closer to the hip joint, whereas a FIB is performed more proximally, targeting the nerves before they enter the hip joint.

The major strength of our study was a prospective double-blinded randomised trial design with two-arm parallel intervention. Also, no attrition was noted after randomisation. However, the study had a few limitations. First, the sample size was calculated using an arbitrary study, as during the beginning of this trial there was no standard one-on-one trial (PENG v/s FIB) on similar surgery. Second, the sample size of this study was relatively small, and not powered to observe some rare complications. Third, adductor strength, hip joint functional recovery and length of hospital stay data were not collected. While cadaveric studies provide valuable insights into the anatomy and technique of nerve blocks, it's important to note that the results may not fully reflect the outcomes in living patients. Clinical studies in living patients are needed to fully evaluate the safety and efficacy of the PENG block for pain management during hip surgery.

Placing an ultrasound-guided continuous catheter via either FIB or PENG block provides adequate analgesia at a 24-hours post-operative period both during rest and on movement. However, the pain at rest was of mild intensity in both the blocks but on movement, the pain in the FIB group was of a greater intensity than the PENG block group. Therefore, the PENG block provides superior analgesia both during rest as well as on movement. While positioning the patient for spinal anesthesia, both the blocks reduced the pain score significantly, still; the PENG block is more efficacious than the FIB. Opioid consumption and related side effects occurred more in the FIB group.

Henceforth, PENG is a feasible analgesic technique and it provides greater analgesia in patients following hip fixation surgery. Thus, PENG should be considered as a primary modality of analgesic approach in patients with proximal hip fractures.

Future studies should be directed towards a comparison of these two types of blocks along with their effects on quadriceps muscle strength and on the assessment of dynamic NRS pain scores while looking at the rotational movement of the hip.

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