What is the PENG Block?
The pericapsular nerve group (PENG) block is an ultrasound-guided regional anesthesia technique that targets the articular branches of the femoral nerve, obturator nerve, and accessory obturator nerve to provide analgesia specifically to the anterior hip joint capsule. 1
Anatomical Target and Mechanism
The PENG block was first described in 2018 as a novel approach based on anatomical studies of hip innervation 1. The technique specifically targets:
- Articular branches of the femoral nerve 2, 1
- Obturator nerve branches 2, 1
- Accessory obturator nerve branches 2, 1
These nerves innervate the anterior capsule of the hip joint, which is the primary source of pain in hip fractures and certain hip surgeries 2, 1.
Clinical Applications
Hip Fracture Analgesia
The PENG block has been most extensively studied for acute pain management in hip fractures 3, 4, 5. Evidence demonstrates:
- Significantly lower dynamic pain scores at 30 minutes, 1 hour, and 3 hours post-block compared to sham block 3
- Reduced 24-hour opioid consumption (median 10 mg vs 15 mg oral morphine equivalent) 3
- Effective analgesia for acute traumatic hip pain 3
Hip Surgery
The block has been described for various hip surgical procedures, though evidence remains limited to case reports and case series 4, 5.
Current Guideline Position
Important Limitations
The Association of Anaesthetists (2021) explicitly states that pericapsular nerve group blocks have NOT been compared with either fascia iliaca or femoral nerve blocks in trials to date, and critically, do NOT provide analgesia to the surgical incision site. 2
This is a critical distinction because:
- Femoral or fascia iliaca blocks remain the recommended first-line peripheral nerve blocks for hip fracture analgesia 2
- PENG blocks target only the hip joint capsule, not the surgical field 2
- For hip fracture surgery, incisional analgesia is essential for mobilization and recovery 2
Emerging Recognition
Despite guideline caution, the PENG block is recognized as a "promising new regional anaesthesia technique" that "merits attention" and "deserves further investigation" 2. Since its 2018 introduction, over 50 articles have been published on the technique 2.
Technical Considerations
- Ultrasound-guided placement is required 1
- Typical injectate volume: 20 mL of long-acting local anesthetic 5
- Motor-sparing: Transient motor side effects occur only when local anesthetic is deposited in unintended locations 4
- Safety profile: No major complications (hematoma, bleeding, or needle-related organ injury) reported in available literature 5
Evidence Quality and Gaps
Current evidence is limited exclusively to case reports and case series 4, 5. No randomized controlled trials have been published comparing PENG block to established techniques like femoral or fascia iliaca blocks 2, 4, 5.
The most robust study to date is a single-center double-blind RCT of 57 patients comparing PENG to sham block, which demonstrated efficacy but did not compare to standard-of-care nerve blocks 3.
Clinical Bottom Line
For hip fracture analgesia, femoral or fascia iliaca blocks remain the evidence-based standard of care 2. The PENG block represents an anatomically-targeted alternative that provides effective hip joint analgesia but does not address surgical incision pain 2. It may have a role when hip joint pain is the primary concern without need for incisional coverage, but requires further comparative trials before routine clinical adoption 2, 4.
Observational and experimental studies comparing PENG block directly to established techniques are urgently needed to determine its true effectiveness, efficacy, and optimal clinical role 4.