Hip fractures are among the most painful orthopedic injuries, particularly during movement or even minor positional changes before surgery. This intense pain not only compromises patient comfort but also activates the sympathetic nervous system, impacts hemodynamic stability, and complicates positioning for spinal anesthesia. Effective preoperative analgesia is therefore critical—not only to improve patient experience but also to optimize surgical conditions and reduce reliance on systemic opioids.

Peripheral nerve blocks (PNBs) have become an integral part of multimodal pain management strategies for hip fractures. They lower pain scores, reduce opioid consumption, and are especially beneficial in older patients, who face heightened risks of opioid-related side effects. Current guidelines recommend fascia iliaca compartment block (FICB), with the supra-inguinal approach (SIFICB) offering broader sensory coverage than the conventional infra-inguinal technique. The SIFICB covers the femoral nerve and lateral femoral cutaneous nerve (LFCN), with spread to the obturator nerve in some cases. This broad coverage makes SIFICB effective for both hip and lateral thigh pain.

More recently, the pericapsular nerve group (PENG) block has been introduced as a targeted option for hip analgesia. By blocking articular branches of the femoral, obturator, and accessory obturator nerves—responsible for innervating the anterior hip capsule—PENG aims to deliver potent pain relief while sparing quadriceps strength. This motor-sparing feature has led some clinicians to consider PENG superior to FICB, particularly in frail or elderly patients requiring early mobilization.

This randomized controlled trial directly compared the efficacy of PENG and SIFICB for managing dynamic pain in patients with hip fractures, providing substantial new evidence for clinical decision-making.

Study objective and methods

The primary objective of this study was to evaluate whether the PENG block provides greater reduction in dynamic pain (pain during passive hip flexion) compared to the SIFICB in patients with hip fractures. 

Study design

• Type: Prospective, single-center, randomized controlled trial.
• Population: 80 adults (ASA I–IV) with hip fractures and baseline NRS ≥4 for dynamic pain.
• Randomization: 1:1 allocation to PENG (n=40) or SIFICB (n=40). Final analysis: 79 patients.
• Blinding: Group allocation concealed with sealed opaque envelopes; outcomes assessed by a blinded investigator.

Interventions

• PENG block: Ultrasound-guided in-plane lateral-to-medial approach targeting the plane deep to the psoas tendon, 20 mL 0.3% ropivacaine.
• SIFICB: Ultrasound-guided parasagittal supra-inguinal approach beneath fascia iliaca near the deep circumflex iliac artery, 30 mL 0.3% ropivacaine.

Perioperative care

• All patients received spinal anesthesia ~ 30 minutes after the block. 
• Multimodal analgesia standardized: Acetaminophen plus rescue tramadol or hydromorphone.
• Postoperative patient-controlled analgesia (PCA) with fentanyl for breakthrough pain.

Outcome measures

• Primary: Reduction in numerical rating scale (NRS) dynamic pain scores at 30 minutes after block. Pain was measured during passive leg raise (> 30°).
• Secondary: Patient-reported analgesic response (Likert and PASS), pain during positioning for spinal anesthesia, postoperative pain at 6/24/48 hours (rest and dynamic), opioid use (24/48 hours), hemodynamic changes after block, motor function (Bromage), early recovery metrics (walk tests, time to ambulation, catheter removal, length of stay), cognitive changes (MMSE), and complications.

Key findings

1. Dynamic pain relief at 30 minutes: No difference

• PENG: Mean reduction 3.1 ± 2.4 NRS.
• SIFICB: Mean reduction 2.9 ± 2.5 NRS.
• Between-group: p = 0.75 (not significant).

Positioning pain for spinal anesthesia and categorical responses (Likert, PASS) were likewise similar. The proportion who could flex the hip after block, despite being unable before, was 57.5% (PENG) vs 48.7% (SIFICB), p = 0.43.

2. Postoperative pain and opioids: Similar profiles

Dynamic and resting pain at 6, 24, and 48 hours showed no significant differences. Cumulative IV morphine equivalents at 0–24 h and 24–48 h were comparable (all p > 0.17). Time to first rescue analgesic did not differ.

3. Hemodynamic tolerance: Stable

No between-group differences in > 20% changes in mean arterial pressure or heart rate 30 minutes after block.

4. Motor function and early mobilization: Comparable

Bromage scores at 6, 24, and 48 hours did not differ. Early recovery metrics (10- and 30-ft walk tests at 24 h, times to wheelchair use and self-ambulation, catheter removal, hospital stay) were also similar. Rates of delirium, respiratory events, acute kidney injury, and other complications did not differ. MMSE change and the proportion with postoperative cognitive dysfunction were comparable.

5. Why “no difference” makes sense in this protocol

The trial deliberately used 0.3% ropivacaine for both techniques to support postoperative analgesia while minimizing motor block. Prior studies that favored PENG for motor-sparing often used higher concentrations (0.5–0.75%) capable of causing greater quadriceps weakness, potentially magnifying technique differences. By using a lower concentration and adequate volumes (20 mL for PENG; 30 mL for SIFICB, consistent with volume-dependent spread), this study may have equalized clinical performance for the endpoints tested.

Conclusion

In adults with hip fractures and significant dynamic pain before surgery, PENG and SIFICB produced clinically meaningful and statistically indistinguishable reductions in movement-evoked pain at 30 minutes. Postoperative pain, opioid use, motor function, and early recovery metrics were likewise similar under a 0.3% ropivacaine regimen. Practically, this means both techniques are reasonable, effective options for pre-operative analgesia and positioning in the hip fracture pathway; the final choice can hinge on anatomy, incision pattern, team familiarity, and ultrasound windows rather than expectation of superior dynamic analgesia with one block over the other.

Future research

• Optimize dosing/volume: Define the best concentration and spread patterns for each block.
• Match block to incision: Study outcomes by surgical approach, especially where LFCN coverage matters.
• Onset efficiency: Compare faster-acting agents or block room strategies to minimize OR delays.
• Functional outcomes: Measure positioning ease, spinal success, ambulation, and discharge readiness.
• Safety monitoring: Prospectively track LFCN irritation and quantify true motor-sparing effects.

Clinical implications

This study demonstrates that both PENG and SIFICB are effective, safe, and clinically equivalent options for reducing dynamic pain and facilitating positioning in hip fracture patients when performed with low-concentration ropivacaine. For anesthesiologists, this means either block can be confidently used in the emergency setting. The choice should depend on the surgical incision site, expected pain generators, and operator expertise rather than the expectation of superior analgesia from one block. PENG may be favored when anterior capsule pain is predominant and motor-sparing is desired, while SIFICB may be advantageous when lateral thigh coverage is essential, such as in surgeries involving longer lateral incisions. Importantly, using 0.2–0.3% ropivacaine minimizes motor block while still providing meaningful analgesia, aligning well with enhanced recovery goals. These findings support flexible, patient-tailored decision-making rather than a one-size-fits-all approach to hip fracture analgesia.

Clinical pearls

• Both blocks cut dynamic pain ≈ 3 NRS points by 30 minutes.
• No differences in postoperative pain or opioid use to 48 h.
• Motor function preserved with 0.3% ropivacaine in both groups.
• Patient-acceptable pain relief metrics were similar.
• Technique selection can be tailored to anatomy and incision.

Practical tip: Choose PENG for anterior capsule pain and SIFICB for lateral thigh coverage—both are equally effective for hip fracture analgesia.

For more detailed information, refer to the full article in RAPM. 

Koh WU et al. Comparison of analgesic effect of pericapsular nerve group block and supra-inguinal fascia iliaca compartment block on dynamic pain in patients with hip fractures: a randomized controlled trial. Reg Anesth Pain Med. 2025 Aug 5;50:635-640.

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