Hip fracture is a common orthopaedic emergency in the elderly and is associated with high morbidity and mortality. Surgical reduction and fixation remain the definitive treatment, but patients frequently experience moderate to severe postoperative pain during the first 24 - 48 hours. Effective perioperative analgesia that minimizes opioid use and related side effects such as respiratory depression and delirium is essential for early rehabilitation and enhanced recovery. ¹ Regional anaesthesia plays a central role in multimodal analgesia for hip procedures including total hip arthroplasty (THA) and bipolar hemiarthroplasty. The femoral and obturator nerves are the main mediators of hip joint pain, while the lateral femoral cutaneous nerve (LFCN) contributes to the sensory innervation of the lateral thigh and surgical incision area. ² Compared with systemic analgesia, regional techniques offer superior pain relief and reduced opioid requirements. Commonly used approaches include lumbar plexus, femoral, and fascia iliaca blocks, while obturator and LFCN blocks can be employed selectively. ² Newer blocks, such as the quadratus lumborum and the pericapsular nerve group (PENG) block, show promise but require further validation. ³˒⁴ Among peripheral nerve blocks, the femoral nerve block, 3 in 1 block, and fascia iliaca block (FIB) are most frequently used, though the optimal technique remains uncertain. The fascia iliaca block provides superior analgesia to placebo in hip surgery, ⁵ and offers safety advantages by avoiding major vessels and the femoral nerve. However, even though the fascia iliaca block is a large volume block, it may not adequately block the obturator nerve. In addition, some studies noted a significant incidence of temporary quadriceps weakness with the use of this block potentially limiting early ambulation and physiotherapy. ² The anterior capsule of the hip—the most densely innervated region—receives sensory branches from the femoral (FN), obturator (ON), and accessory obturator (AON) nerves.⁴ Anatomical studies reveal that these branches are consistently located between the anterior inferior iliac spine (AIIS) and the iliopubic eminence (IPE), while the obturator branches course near the inferomedial acetabulum.⁴ Based on these findings, the PENG block was designed, with the aim to target these particular branches selectively. Giron Arango et al. first described the ultrasound guided PENG block in 2018, demonstrating effective analgesia in hip fractures.⁵ The technique deposits local anaesthetic between the psoas muscle and the superior pubic ramus, providing selective blockade of the articular branches of the FN, AON, and ON while minimizing motor involvement.⁶˒⁷ The PENG block thus offers an attractive alternative to the femoral and fascia iliaca blocks for hip fracture and arthroplasty analgesia. This study aimed to evaluate the postoperative analgesic efficacy of continuous PENG block compared with continuous suprainguinal fascia iliaca block (SFIB) in patients undergoing hip surgery.

This is a prospective, randomised, clinical trial. Approval was obtained from our Institutional review Committee [IEC-NRCH Institutional Ethics Committee. Northern Railway Central Hospital] under the following study number [Protocol No. DNB/ Protocol. /NRCH/2021/04] dated 03/02/2021. Before patient enrolment, the trial protocol was registered in the Clinical Trials Registry- India (CTRI) [Trial Registered Prospectively on: 19/03/2021] under the number CTRI/2021/03/032161 (Principal investigator: Wasim. Zafar). After a detailed explanation about the study rationale and details by the principal investigator, written informed consent was obtained, before proceeding to include eligible patients into the trial. This study follows the applicable CONSORT guidelines and was performed in accordance with the most recent version of the Helsinki Declaration. Data acquisition was carried out between 20/03/2021 and 20 /11 /2021 at Northern Railway Central Hospital, New Delhi. Patients aged 18 -85 years old, of American Society of Anaesthesiologists Physical Status grades [ASA] 1-3, who were scheduled for elective unilateral hip surgery were consecutively and prospectively considered as eligible for inclusion. Exclusion criteria were as follows refusal of the patient to participate, known allergy or intolerance to any of the drugs used in the study, hepatic or renal insufficiency, opioid dependency. coagulopathy, pre-existing neurologic or anatomic deficits in the lower extremities, severe psychiatric illness or receiving general anaesthesia. Computer-generated random number table method with randomized group information sealed in an opaque envelope, was numbered and used sequentially. The patient, surgeon and the anaesthetist who collected postoperative data were blinded to group assignment. was also blinded regarding the group assignment. PENG or SFIB catheter placement was performed by an unblinded experienced anaesthetist. Perioperative anaesthesia management was according to our hospital routine protocol. An 18/20-gauge IV cannula and standard monitoring (non-invasive blood pressure, electrocardiography, and pulse oximetry) was placed in all patients, routine spinal anaesthesia was administered using 12.5mg (2.5ml) Hyperbaric bupivacaine. In case of failure of SA with conversion to general anaesthesia, it was decided before enrolment to exclude data from these patients. After confirming that the patients were hemodynamically stable, the patients in the both groups received their respective blocks using ultrasound guidance. Pericapsular nerve group block (PENG) group: As described by Giron-Arango et al 5, a curvilinear 2-5MHz ultrasound probe was initially placed in a transverse plane over the anterior superior iliac spine and then aligned with the pubic ramus by rotating the probe counter clockwise approximately 45 degrees. In this view, the iliopubic eminence, the iliopsoas muscle and tendon, the femoral artery, and pectineus muscle was observed. A 22-gauge, 80-mm needle was inserted from lateral to medial in an in-plane approach to place the tip in the musculofascial plane between the psoas tendon anteriorly and the pubic ramus posteriorly. A PNB catheter was placed at this location [FIGURE 1]. A total volume of 20 ml of ropivacaine 0.20% was injected, in fractionated doses, followed by an infusion of 0.2% ropivacaine at 4ml /hr. The LFCN block was performed as described by Nielson et al.8 LFCN is typically visualized with ultrasound between the tensor fasciae lata and the sartorius muscles, 1 to 2 cm medial and inferior to the anterior superior iliac spine, as an oval hypoechoic small structure with a hyperechoic rim and was blocked at this location using 15 ml of 0.20% ropivacaine. Thus, all patients in the PENG group received a total of 35 ml of 0.20% ropivacaine followed by an infusion of ropivacaine 0.20% at 4ml/hr. Suprainguinal fascia iliaca compartment block (SFIB): A linear 6-13-MHz ultrasound probe was placed in the sagittal plane to obtain an image of the anterior superior iliac spine.as described by Desmet et al.9 The fascia iliaca and sartorius, iliopsoas, and oblique internal muscles was identified by sliding the probe medially. After identifying the "bow-tie sign" formed by the muscle fascias, a 22-gauge, 80-mm needle was introduced about 1 cm cephalad to the inguinal ligament. Using an in-plane approach, the fascia iliaca was penetrated and hydrodissected, separating the fascia iliaca from the iliac muscle. A PNB catheter was placed here. [FIGURE 2] A bolus of 35ml of ropivacaine 0.2% was injected in fractionated doses this was followed by an infusion of ropivacaine 0.2 % at 4ml /hr. In both groups catheters were removed after 36 hours. Patient were monitored in the PACU. When pain management in PACU was judged as inadequate, as defined by a numeric verbal rating scale nVRS >/=3 rescue analgesia of inj tramadol 1mg/kg was administered. If pain management with tramadol remained inadequate nVRS >/=3 after 30 minutes, an inj ketorolac 30mg was administered. Paracetamol 650mg orally was administered thrice daily, the first dose being administered as soon as the patient was permitted to intake orally - usually 6 hours after the administration of spinal anaesthesia. Parameters Noted: In the postoperative period, a blinded observer noted the total 36-hour analgesic consumption i.e the total amount of rescue analgesia. This was calculated as an equivalent dose of opioid in terms of morphine equivalents (tramadol 10mg=fentanyl 10mcg =Morphine 1mg). Postoperative pain at rest [static pain] was assessed by a numeric verbal rating scale nVRS score at 3, 6, 12, 24 and 36 hours, and postoperative pain at motion [dynamic pain] was assessed by nVRS score at 12, 24 and 36 hours, (time 0 was immediately after catheter placement). Comparison of quadriceps motor weakness or block in the two groups was carried out at 24 hours and 36 hours. Subjects were seated at the edge of the bed with the leg staying hanging. and then asked to slowly push the leg out towards examiner. The degree of the resistance was rated as follows indicating normal quadriceps strength if the leg could be straightened 900, moderate resistance indicating mild quadriceps weakness If the leg could be straightened 450 and poor resistance indicating severe quadriceps weakness if the leg could be straightened 150 or less. Grading of muscle power was done accordingly (0: complete paralysis, 1: flicker of contraction possible, 2: movement possible if gravity eliminated, 3: movement against gravity but not resistance, 4: movement possible against some resistance, 5: power normal). Comparison of Patient satisfaction after the first 36 hrs after surgery was recorded on a scale from Poor =1 Fair =2 Good =3 Excellent =4 Statistical Analyses The primary endpoint of the study was the comparison of the post operative analgesic consumption (in the first thirty-six hour post operative period) between Continuous ultrasound guided Pericapsular Nerve Group (PENG) block, and the standard treatment i.e Continuous Suprainguinal Fascia iliaca block (SFIB) after hip surgeries. Secondary endpoints were Comparison of Static pain at 3, 6, 12, 24 and 36 hours, and Comparison of Dynamic pain at 12, 24 and 36 hours, assessed by nVRS (numeric verbal rating score) pain score; Comparison of quadriceps motor weakness or block in the two groups at 24 hours and 36 hours; and patient satisfaction after the first 36 hrs after surgery recorded on a scale from Poor =1 Fair =2 Good =3 Excellent =4. All statistical analyses were performed using the Statistical Package for the Social Sciences. We performed an a priori sample size calculation basing our calculation on an average 24 hour morphine consumption of 6.95 mg ± 2.14 as assessed by Kumar et al ref [They had performed a randomised control study of Indian patients in the same geographical location who received SFICB after total hip arthroplasty]; We considered a 25 % decrease in 24 hour morphine consumption to be significant; 48 patients per group were needed to reach 80% power with a confidence level 95% . Normality of distributions were tested whenever required by using the Shapiro–Wilk test. For normally distributed data, the Student t test was used to compare the mean differences of variables between the groups. For variables with nonparametric distribution (age), the Mann–Whitney test was used to compare differences of the medians between the groups. Tests for significant differences between the groups was done with the x2 test for categorical data (ASA, sex). A P-value of less than 0.05 was was considered statistically significant. All data are presented as mean (± SD) / median (interquartile range) as appropriate.

After obtaining informed written consent, a total of 48 patients undergoing THA were enrolled and allocated randomly to the two groups. All subjects included in the final study, completed the study and were included for analysis. The demographic characteristics of the subjects are presented in Table-1. The two groups were demographically comparable in terms of gender, age and ASA grading. Both groups were well-matched in terms of age and sex; Most patients in both groups were classified as ASA II. The analgesic consumption, pain scores at different time intervals, quadriceps muscle weakness and patient satisfaction score are presented in Table-2. Compared to the SFIB group, the PENG group demonstrated a significantly lower total rescue analgesic consumption in terms of morphine equivalent in 36 hrs (group A 1.54 vs group B 5.52[ p<0.001]). The VAS scores between groups at rest [static nVRS] were compared at 3 hrs, 6 hrs, 12 hrs, 24hrs and 36 hrs. nVRS scores at rest were low overall; and were consistently lower in the PENG group. At no point of time did the nVRS score in the PENG group exceed that in the SFIB group. The VAS scores between groups in motion [Dynamic nVRS ] at 12 hrs, 24 hrs and 36 hrs were also compared between two groups. The dynamic nVRS scores were significantly different only in the first 12 hours of the post-operative period [1.710.55 in the PENG group vs 2.541.28 in the SFIB Group (P= 0.004)] but were similar in both groups thereafter.[ p= 0.347 at 24 hrs and p= 0.047at 36 hrs] It is notable that the pain scores in the Peng group remained at or below 2.0 for both rest and movement, at all time points, showing a consistent and prolonged analgesic effect. Quadriceps muscle weakness was assessed at 24 and 36 hours post operatively. No muscle weakness was detected in any patient in both the groups both at 24 hours and 36 hours post operative period. Therefore, the postoperative lower limb muscle strength was well preserved in both the groups. Finally patient satisfaction scores were also noted on a 4-point scale after 36 hours and was found to be statistically significantly higher in the PENG group [group A 3.3330.86 vs group B 2.7920.93, (p =0.043)]. FIGURE 1 Figure 2   TABLE-1: Comparison Of Demographic Characteristics PENG(n=24) SFIB(n=24) p-value Male 13 14 0.77 Female 11 10 0.77 Age (m/sd) 60.42(11.01) 64.83(9.8) 0.149 ASA GRADING 1 4 3 2 16 18 3 4 3 TABLE-2: Analgesic Consumption, Pain Scores at Different Time Intervals, Quadriceps Muscle Weakness and Patient Satisfaction Score Comparison Table PENG(n=24) SFIB(n=24) P value Total analgesic consumption (morphine equivalents ME) 1.54 5.52 <0.001 Static pain score 3 hours 0.330.7 1.631.66 <0.001 6 hours 1.51.5 3.211.47 <0.001 12 hours 1.250.79 2.381.44 0.002 24 hours 0.580.72 1.331.13 0.009 36 hours 0.250.44 1.000.72 <0.001 Dynamic pain score 12 hours 1.710.55 2.541.28 0.004 24 hours 1.130.74 1.381.06 0.347 36 hours 0.50.51 0.880.74 0.057 Quadriceps muscle weakness 24 hours 5 5 NA 36 hours 5 5 NA Patient satisfaction score 3.330.868 2.7920.932 0.043 Values are presented as mean ± standard deviation (SD) or number (n.). P values were calculated using an independent t-test for continuous variables and a chi-square test for categorical variables as appropriate. PENG: Pericapsular nerve group; SFIB: Supra-inguinal fascia iliaca compartment block; ASA: American Society of Anesthesiologists

In this study, we compared the analgesic effectiveness of continuous ultrasound guided pericapsular nerve group (PENG) block and continuous suprainguinal fascia iliaca block (SFIB) for postoperative pain following hip surgery. Our results indicate that continuous PENG infusion significantly reduced opioid requirements and provided superior analgesia at rest during the first 36 hours postoperatively. These findings are broadly consistent with current literature, though some differences require further discussion. Kukreja et al. conducted a retrospective case series of 12 patients undergoing primary and revision total hip arthroplasty (THA) with PENG block and observed lower postoperative pain scores and oral morphine equivalent (OME) requirements, particularly in primary hip surgery cases10. They also noted that OME use was markedly lower than in historical studies using femoral or lumbar plexus blocks.10 Our results agree with these observations, confirming the opioid sparing effect of the PENG block. Aliste et al. compared single shot PENG and SFIB blocks in THA patients.11 They found no clinically significant difference in pain scores or opioid consumption at 24 and 48 hours but reported less quadriceps weakness and improved hip adduction at 3 hours with PENG. Their primary outcome was motor block rather than analgesic efficacy, and the single injection design with extensive multimodal therapy may have limited the ability to detect analgesic differences. In contrast, our continuous infusion method provided prolonged sensory coverage, likely explaining our more distinct pain and opioid outcomes. Desmet et al. performed a randomized controlled trial comparing high volume single shot SFIB to no block in THA, reporting significantly lower 24 hour morphine consumption (~10 mg OME) in the block group9. Although our SFIB group showed higher opioid consumption, this is likely due to differences in technique and continuous infusion in our study versus the single shot design used by Desmet et al, which was combined with greater use of multimodal analgesia. In our study, we used an active control instead of a placebo group, consistent with current ethical standards discouraging placebo use when effective treatments exist. The analgesic outcome—total opioid use in morphine equivalents—was chosen for direct comparison with other published work and to standardize quantification of multimodal analgesic regimens. Lin et al. compared single shot PENG and femoral nerve blocks (FNB) for hip fracture analgesia and reported higher 24 hour opioid consumption than in our population, reflecting the acute and often more painful nature of trauma surgery12. Their lack of continuous analgesic infusion further explains the discrepancy. Similarly, Allard et al. compared single injection PENG and FNB in 42 patients with femoral neck fractures, finding comparable analgesia and reduced quadriceps weakness with PENG but no difference in opioid use or pain scores over forty-eight hours.13 The higher morphine requirements in their elderly cohort (median age 80.5 years) and absence of perineural infusion likely account for the contrast with our results. Our PENG protocol incorporated a supplementary LFCN block, following a recommendation by Roy et al.14 that this combination enhances lateral thigh analgesia. Liang et al. subsequently confirmed that adding an LFCN block to PENG improved early postoperative mobility compared to SFIB, though postoperative pain reduction was statistically significant only at 48 hours.15 These findings mirror our data showing better early static pain relief in the PENG cohort. The absence of significant motor weakness in our SFIB group, despite continuous infusion, may be attributed to the use of low dose ropivacaine (0.2% at 4 mL/h) and limited sample size. Our study was powered for the primary endpoint—opioid consumption—rather than for detecting rare motor complications. Nonetheless, the preservation of quadriceps function in both groups supports the motor sparing nature of the chosen concentration and infusion rate. This contrasts with the study by, Aliste et al. who observed substantially higher early quadriceps weakness rates after SFIB compared to PENG, with incidences of 90% vs 45% at 3 hours and 85% vs 25% at 6 hours post block. They did not assess at later time points. We selected 24 and 36 hour evaluations, which we believe are more relevant to rehabilitation timelines relevant to our institutional protocol - where physiotherapy typically begins after the first postoperative day. Rescue analgesic requirements in both our groups were comparable with published data for SFIB, validating the consistency of our control group. The PENG group, however, required less morphine equivalent overall, establishing its superior opioid sparing potential when administered as a continuous infusion. Regarding static pain, nVRS scores in our PENG group were significantly lower at 3, 6, 12, 24, and 36 hours, corroborating results from Lin et al., where a majority of PENG patients reported minimal or no pain in the recovery room compared to their FNB counterparts. This pronounced reduction in rest pain likely reflects more complete blockade of the articular branches of the hip capsule provided by the PENG technique. Dynamic pain control—important for early physiotherapy and mobilization—was improved in our PENG group at 12 hours but similar between both groups by 24 and 36 hours. The convergence of pain scores over time may reflect catheter dilution from continuous low flow infusions or a genuine equilibration of analgesic effect once systemic multimodal therapy became established. Patient satisfaction was slightly higher in the PENG group, reflecting greater comfort and mobility during the early postoperative period. Lin et al. similarly observed that more patients in the PENG group expressed willingness to receive the same block again for future procedures, suggesting improved tolerance and perceived benefit. Overall, our data demonstrate that continuous PENG block provides more consistent pain relief at rest and requires lower opioid supplementation than continuous SFIB, with comparable safety and no significant motor impairment. These findings, in combination with supportive results from recent comparative studies, highlight the PENG block’s potential as an effective, motor sparing component of multimodal analgesia for hip surgery. Nevertheless, several factors require further consideration. The inclusion of an LFCN block in the PENG group may have influenced the superior analgesia observed, though this approach reflects evolving recommendations for comprehensive coverage of hip incision sites. Differences in multimodal drug regimens and surgical variability could also confound pain assessment, despite standardized anaesthetic protocols. Moreover, as our sample size was calculated for analgesic consumption, the study may have been underpowered to detect less common outcomes such as transient neuropathy or catheter related complications. Despite these limitations, the study adds to emerging evidence supporting the PENG block’s utility in hip surgery. By combining targeted sensory blockade with preserved quadriceps strength, continuous PENG infusion can facilitate early mobilization and enhance rehabilitation outcomes, aligning with enhanced recovery after surgery (ERAS) protocols. In summary, our results show that continuous PENG block provides superior early postoperative analgesia and lower opioid consumption than continuous SFIB for hip surgery without compromising motor function. These findings corroborate existing evidence and suggest that the PENG approach, particularly when combined with an LFCN block, offers an effective and safe alternative within modern perioperative pain management strategies.

From our study we observed that total analgesic consumption was lower in the PENG group than the SFIB group. Static and early dynamic pain scores in the postoperative period in the PENG group A were lower than group B[SFIB]. No quadriceps muscle weakness reported in both the groups after the operation. Patient satisfaction score was overall higher with the PENG block. Based on these results, the use of the continuous PENG Block appears superior in preference to the continuous Suprainguinal fascia iliaca block for postoperative pain relief after hip surgeries. These findings may be further confirmed by larger studies that are adequately powered to detect rare side effects of these blocks.

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