Comparison of Ultrasound-Guided Pericapsular Nerve Group Block Versus Intravenous Ketamine for Positional Pain Management Before Spinal Anesthesia in Patients Who Underwent Hip Fracture Surgery: A Randomized Controlled Trial

Introduction

Hip fracture is a common problem worldwide, affecting approximately 1.5 million elderly people each year [1]. In many developed societies, the incidence of hip fractures is expected to increase over the years due to population aging. The annual mortality rate due to hip fracture varies between 12% to 37% [2].

In the elderly population, pain management can become complicated by comorbidities, limited physiologic reserve, polypharmacy, and adverse effects of nonsteroidal anti-inflammatory drugs and opioid analgesics [3]. In patients with hip fractures, most of the pain that occurs, especially with movement, originates from the joint capsule [4]. Therefore, optimal pain management in the treatment of hip fracture patients will improve functional recovery, morbidity, and mortality outcomes [5].

Poor management of pain in surgical patients has been associated with delayed mobilization, cardiopulmonary complications, delirium, longer hospital stay, and lower quality of life. For hip surgery, the Procedure Specific Postoperative Pain Management (PROSPECT) 2021 guideline recommends several perioperative interventions to alleviate postoperative pain [4–6].

Anesthesiologists prefer spinal anesthesia to general anesthesia in hip fracture cases because of its positive effects such as decreased blood loss as a result of sympathetic blockade, increased blood flow in the lower extremities, support for analgesia in the postoperative period, decreased postoperative delirium, and fewer complications of pneumonia and deep vein thrombosis [5,7]. According to Enhanced Recovery After Surgery (ERAS) protocols, unilateral spinal anesthesia is recommended as the preferred anesthesia method [8]. In hip fracture patients, the success of subarachnoid blockade depends on proper patient positioning, which may be difficult due to severe pain [9]. During positioning, intravenous (i.v.) fentanyl, ketamine, femoral nerve block (FNB), fascia iliaca block (FICB), and the recently popularized pericapsular nerve group (PENG) block are used to control pain [7]. The opioids used have many adverse effects such as nausea, vomiting, constipation, sedation, and respiratory depression [3].

Ultrasound-guided lower-extremity peripheral nerve blocks contribute to postoperative analgesia by reducing perioperative opioid consumption in hip fracture patients. The PENG block, first described by Girón-Arango et al, is a new fascial plane block technique and is easy to perform. Studies have shown that PENG block reduces the need for opioids and dynamic pain scores in hip fracture patients [9]. PENG block aims to selectively involve the anterior aspect of the hip capsule by directly blocking the articular branch of the femoral nerve, the articular branch of the obturator nerve, and the accessory obturator nerve. This has the advantage of preserving the motor function of the quadriceps muscles [3,6].

Ketamine is used in postoperative analgesia as part of multimodal analgesia to reduce opioid consumption. In orthopedic surgery, low doses of ketamine show analgesic benefits with cardiac and respiratory stability [7]. While previous studies have compared PENG block with other regional techniques, no study to date has systematically evaluated its efficacy against intravenous ketamine for alleviating positioning pain during spinal anesthesia in hip fracture patients.

The hypothesis of this study was that ultrasound-guided PENG block would provide effective analgesia for positioning before spinal anesthesia. The primary objective of this study was to evaluate the dynamic (pre-position-during-post-position) NRS (numerical rating scale 0 to 10) pain scores at different time points of ultrasound-guided PENG block to provide analgesia during positioning before spinal anesthesia. Secondary objectives were postoperative NRS scores, need for additional rescue analgesia, patient satisfaction (QoR-15 score), and frequency of complications.

Material and Methods

STUDY DESIGN AND PATIENT POPULATION:

Our study was conducted with the approval of the Ethics Committee of Istanbul Medipol University (No: 2024/1059) between 10/1/2024 and 5/25/2025 in the Department of Anesthesiology, Istanbul Training and Research Hospital (ClinicalTrials.number NCT06813755).

The study was designed in accordance with the CONSORT guidelines, all participants gave written informed consent for participation in the study, and the study was conducted in accordance with the Declaration of Helsinki.

ASA II–III patients aged 35 to 90 years who were scheduled to undergo hip fracture surgery under spinal anesthesia were included in the study.

Exclusion criteria were as follows: Presence of contraindications for spinal anesthesia or PENG block (infection at the injection site, low ejection fraction, coagulopath), dementia or cognitive dysfunction, use of analgesics within the last 12 hours, multitrauma, presence of additional problems causing chronic pain, and patients who did not give written informed consent.

GROUPING, RANDOMIZATION AND BLINDING:

Patients were randomly allocated to the PENG block and control group by a randomized procedure using opaque, sequentially numbered sealed envelopes, kept by a research assistant not involved with patient care. The envelopes were opened 1 hour before surgery by the anesthesiologist performing the intervention, after eligibility confirmation and written informed consent. Each participant was assigned an identification number to be used throughout the study period. Patients were not informed of their group allocation.

The anesthesiologist (Gul Cakmak: GC), who had sufficient experience in this technique, performed all PENG blocks but was not involved in randomization, outcome assessment, or data collection. Prior to surgery, all participants were transferred to the block room and subsequently to the operating theater. An independent evaluation team (Abdurrahman Tunay: AT, Veysel Erden: VE), blinded to group allocation, was responsible for collecting and analyzing data on spinal anesthesia positioning pain, postoperative NRS scores, and opioid requirements. Postoperative follow-up was conducted jointly by surgeons and anesthesiologists, without interfering with the procedural preferences of the physicians. Patients were instructed to contact the ward nurse for pain relief if they experienced discomfort after surgery. The timing of the first tramadol administration, subsequent doses, and cumulative amounts were obtained from nursing observation records.

Postoperative complications, including hypotension, nausea, vomiting, sedation, dizziness, delirium, hallucinations, urinary retention, respiratory depression, and neurological complications, were monitored and recorded by anesthesiologists and ward nurses during the first 24 hours postoperatively. Delirium and hallucinations were identified based on direct clinical observation and documentation in the nursing records. Patient data collected included age, height, body weight, body mass index (BMI), sex, American Society of Anesthesiologists (ASA) physical status classification, type of surgery, duration of surgery, postoperative NRS scores, time to first tramadol request, total tramadol use in the postoperative 24 hours, vital signs recorded at preoperative and intraoperative period, and patient satisfaction. Information on timing to first request and total tramadol consumption was documented on the nurse observation form and pain follow-up form.

ANESTHESIA MANAGEMENT AND SURGICAL TECHNIQUE:

All participants were positioned in the lateral decubitus position with the fractured side facing upward. Standard monitoring (heart rate, non-invasive blood pressure, and SpO₂) was performed, and oxygen was delivered via nasal cannula. Intravenous access was established through the non-dominant hand. For sedation, all patients received 1 mg i.v. midazolam.

Patients in the control group additionally received 0.2 mg/kg i.v. ketamine 5 minutes before spinal anesthesia. The dose was chosen based on previous studies demonstrating that low-dose ketamine provides effective analgesia and hemodynamic stability in elderly orthopedic patients, while minimizing the risk of psychomimetic adverse effects [7]. This allowed for a clinically relevant comparison with the PENG block, as both interventions aimed to facilitate patient positioning for spinal anesthesia by reducing pain.

A 25G spinal needle was inserted through the L3–L4 or L4–L5 interspace, and 10 to 12.5 mg isobaric bupivacaine was injected intrathecally. After the injection, patients were placed in the supine position, and surgery was initiated following confirmation of adequate block with the pinprick test.

SURGICAL TECHNIQUE:

Patients undergoing proximal femur nailing and partial hip replacement surgeries were included, while those undergoing total hip replacement, femoral shaft surgery, and distal femur surgery were excluded.

PERICAPSULAR NERVE GROUP BLOCK:

In the PENG group; participants were monitored before the block, oxygen was administered via nasal cannula, and a non-dominant hand vascular access was established. One mg i.v. midazolam, as already administered preoperatively, was given for sedation. PENG block was performed 20 minutes before spinal anesthesia.

All blocks were performed by the same anesthesiologist (GC) with ultrasound guidance in the block room.

PENG block was performed on the hip fracture side using convex/linear USG probe (Esaote, Europe B.V., Maastricht, the Netherlands) using an 80 mm, 20 G block needle (Pajunk, SonoPlex STIM, Geisingen, Germany) with in-plane technique after skin antisepsis. Local infiltration analgesia with 2% lidocaine was applied before block application.

The ultrasound probe was positioned in probe orientation at the level of the anterior superior iliac spine (ASIS). The anterior inferior iliac spine (AIIS) was delineated through manipulation of the probe in a caudal direction. A sonographic representation covering the femoral artery, femoral nerve, iliac muscle, psoas tendon, iliopubic eminence, and anterior inferior iliac spine was obtained. The needle was inserted between the iliopsoas tendon (IPT) and the periosteum, traveling in a lateromedial vector (Figure 1). Hydrodissection was initially performed using 1 to 2 mL of saline. Consequently, 20 mL of a 0.25% solution of bupivacaine was administered. Each 5 mL was tested with a negative aspiration after administration. Successful block placement was confirmed by visualizing the spread of local anesthetic between the iliopsoas tendon and the iliopubic eminence under ultrasound guidance.

POSTOPERATIVE ANALGESIA MANAGEMENT AND OUTCOMES:

Pain intensity was assessed using the Numerical Rating Scale (NRS, 0–10; 0=no pain, 10=worst pain imaginable).

Assessment time points were as follows:

All patients routinely received 1 g i.v. paracetamol immediately after surgery and every 6 hours thereafter. If the NRS score was ≥4 at rest, 50 mg i.v. tramadol was administered as rescue analgesia. Thus, tramadol administration was titrated according to NRS scores and was not administered indiscriminately. The timing of the first i.v. tramadol administration, subsequent doses, and cumulative 24-hour consumption were obtained from nursing observation records.

Vital signs, including heart rate, non-invasive blood pressure, and peripheral oxygen saturation, were continuously monitored during the perioperative period and recorded at predefined intervals to evaluate the safety and clinical stability of the interventions. Patient satisfaction was evaluated at 24 hours postoperatively using the validated Quality of Recovery-15 (QoR-15) questionnaire.

PRIMARY OUTCOME:

Pain during positioning for spinal anesthesia, measured with the Numerical Rating Scale (NRS, 0–10).

STATISTICAL ANALYSIS:

The sample size for this study was calculated using G*Power software (V.3.1.9) [10]. The primary objective was to compare NRS scores during positioning between the groups. In a preliminary analysis involving 8 patients per group, the NRS scores during positioning were 4.2 in the control group and 3.0 in the PENG group, with standard deviations (SDs) of 1.3 and 1.2, respectively. Based on an α error of 0.05 and a β error of 0.10, the required sample size per group was determined to be 29, providing a statistical power of 95%. To account for potential drop-outs, a minimum of 30 patients per group was planned. Taking into account drop-outs from follow-up, and secondary outcomes, it was decided that each cohort would include 30 participants.

All statistical analyses were performed using SPSS version 26.0 (SPSS, Inc., Chicago, IL, USA). The normality of continuous variables was assessed using the Kolmogorov-Smirnov test. Continuous variables were expressed as mean±standard deviation for normally distributed data and as median (25^th–75^th percentiles) for non-normally distributed data. Between-group comparisons of continuous variables were performed using the independent samples t test or the Mann-Whitney U test, depending on the data distribution. Categorical variables were compared using the chi-square test or Fisher’s exact test, as appropriate. Pain scores (NRS) measured at various time points (eg, preoperative, during positioning, postoperative 0^th, 3^rd, 6^th, 12^th, and 24^th hours) were compared between groups using the Mann-Whitney U test, as these data were non-normally distributed. All randomized patients who completed the study protocol (n=62) were included in the final analysis; therefore, there were no missing data and no imputation was required. No formal adjustment for multiple comparisons was made, as the primary outcome (positioning pain NRS) was predefined a priori, whereas secondary outcomes were analyzed in an exploratory manner. A P value of <0.05 was considered statistically significant.

Results

A total of 66 patients were evaluated for eligibility. Four patients were excluded and the remaining 62 patients were randomly divided into 2 groups. In the final analysis, 30 patients in the PENG group and 32 patients in the control group were evaluated (Figure 2).

PENG Group: 11 patients underwent partial hip replacement and 19 patients underwent proximal femoral nailing (PFN).

Control Group: 10 patients underwent partial hip replacement and 22 patients underwent PFN.

There was no significant difference between the groups in terms of types of surgery (P>0.05).

The mean age was 76.7±7.1 years in the PENG group and 75.3±5.9 years in the control group, with no significant difference between them (P>0.05). No significant difference was found between the groups in terms of sex, body weight, height, and body mass index (BMI) (Table 1).

The duration of spinal anesthesia administration was significantly shorter in the PENG group compared to the control group (4.7±0.4 min vs 5.2±0.3 min, P<0.001) (Table 2).

The quality of patient positioning was also rated significantly higher in the PENG group (P<0.001) (Table 2).

Hemodynamic parameters (heart rate, blood pressure, SpO2, respiratory rate) remained stable in both groups, with no significant intergroup differences (Table 3).

Pain scores at baseline (preoperative) were similar (P=0.948). However, compared with the control group, the PENG group demonstrated significantly lower NRS scores before positioning, during positioning, and after spinal anesthesia (all P<0.001) (Table 4). Postoperatively, pain scores were significantly lower in the PENG group at 3, 6, and 12 hours, but no difference was observed at 24 hours (Table 4, Figures 3, 4).

In terms of analgesic requirements, the time to first tramadol administration was significantly longer in the PENG group (10.5±2.7 vs 5.6±0.9 hours, P<0.001), and total tramadol consumption in the first 24 hours was significantly lower (P<0.001). Furthermore, patient satisfaction, as assessed by postoperative QoR-15 scores, was significantly higher in the PENG group (107±9.1 vs 98.1±4.7, P<0.001) (Table 5).

Discussion

LIMITATION:

First, the sample size was small and the study was conducted in a single center, which may limit generalizability to other institutions or populations. Although the study was adequately powered to detect differences in the primary outcome, results should be interpreted with caution when extrapolated to different clinical settings. Second, the block was applied as a single injection, so the potential benefits of continuous catheter infusion remain unknown. Future studies should also investigate different volumes, concentrations, and dermatomal spread. Another limitation is the heterogeneity of the surgical population, as both proximal femoral nail fixation and partial hip replacement were included. Although their distribution was comparable, differences in surgical technique and pain mechanisms may have affected outcomes. Finally, PENG block mainly provides anterior capsule analgesia, while posterior capsule pain may persist, especially in partial hip replacement cases. Thus, the analgesic effect may not be fully comprehensive, and intraoperative peri-capsular injection could be considered in future studies.

Conclusions

In patients undergoing hip fracture surgery, particularly elderly and frail individuals, performing a PENG block before spinal anesthesia significantly reduced positioning pain and postoperative opioid requirements compared with intravenous ketamine. By minimizing opioid exposure, this approach may help decrease opioid-related adverse effects and facilitate safer perioperative care. This study provides a novel systematic comparison of PENG block and intravenous ketamine for this indication, underscoring its value as a practical and safe component of multimodal analgesia. Future multicenter trials with larger cohorts are warranted to confirm these findings and to further evaluate the broader applicability of PENG block in this patient population.