PENG Block vs Fascia Iliaca Block for Hip Surgery
For hip arthroplasty and proximal femur fracture repair, PENG block provides superior postoperative analgesia with better motor sparing compared to fascia iliaca compartment block, though fascia iliaca block remains the guideline-recommended standard due to more extensive evidence and coverage of the surgical incision site.
Guideline Recommendations
Current guidelines favor fascia iliaca block as the preferred peripheral nerve block for hip surgery. The PROSPECT 2021 guidelines for total hip arthroplasty specifically recommend fascia iliaca block over femoral nerve block, citing three meta-analyses showing lower pain scores, reduced morphine consumption, and shorter hospital stays without increased fall risk 1. The Association of Anaesthetists 2021 hip fracture guidelines state that femoral or fascia iliaca blocks should be used, but note that PENG blocks have not been compared with either fascia iliaca or femoral nerve blocks in trials to date, and do not provide analgesia to the surgical incision site 1.
Key Technical Differences
Sensory Coverage
- PENG block: Targets articular branches of the femoral nerve, obturator nerve, and accessory obturator nerve between the psoas tendon and pubic ramus, providing focused hip joint analgesia 2, 3, 4
- Fascia iliaca block: Provides broader coverage including the femoral nerve, lateral femoral cutaneous nerve, and potentially obturator nerve branches, covering both hip joint and anterior thigh/incision site 1, 5, 6
Motor Sparing
PENG block demonstrates significantly better quadriceps muscle preservation. Multiple studies show PENG block maintains superior quadriceps strength compared to fascia iliaca block (P = 0.001 at 24 hours) 3, 4. This motor sparing advantage does not delay mobilization in either technique 7.
Comparative Analgesic Efficacy
Recent research evidence suggests PENG block provides superior postoperative pain control, though this contradicts guideline recommendations based on older evidence.
Pain Scores
- PENG block showed significantly lower pain scores at movement at 1 hour (P = 0.035) and 4 hours (P = 0.001) compared to fascia iliaca block 2
- At 24 hours, PENG block maintained lower visual analog scale scores at movement (P = 0.018) 3
- PENG block provided better ease of positioning for spinal anesthesia (P < 0.0001) 8
Opioid Consumption
- Total opioid consumption was 28.5% in PENG group versus 71.4% in fascia iliaca group over 24 hours (P = 0.03) 3
- Time to first rescue analgesia was significantly longer with PENG block (8.17 ± 3.13 hours) versus fascia iliaca block (4.00 ± 1.48 hours) 2
- PENG plus lateral femoral cutaneous nerve block resulted in less PRN opioid use (0 vs 60 mg morphine equivalents, P = 0.001) 7
Clinical Algorithm for Block Selection
Choose PENG block when:
- Posterior surgical approach is planned (where incisional coverage is less critical) 1
- Early mobilization is paramount and motor sparing is prioritized 3, 4
- Primary concern is hip joint pain rather than incisional pain 2, 8
Choose fascia iliaca block when:
- Anterior or anterolateral surgical approach is used (requiring incisional analgesia) 1
- Following established guideline protocols for quality metrics 1
- Institution lacks experience with PENG block technique 5, 6
Consider combining PENG with lateral femoral cutaneous nerve block to provide both joint analgesia and anterior thigh coverage, potentially offering advantages of both techniques 7.
Technical Considerations
Dosing
- Fascia iliaca block: 30-40 mL of 0.25% bupivacaine with epinephrine 1:200,000 for single-shot 5, 6
- PENG block: 20-30 mL of 0.25% levobupivacaine (studies used 30 mL) 2, 4
- Both blocks benefit from ultrasound guidance to improve accuracy 1, 5, 6
Safety Profile
Both blocks demonstrate excellent safety profiles with minimal complications when performed under ultrasound guidance 5, 2, 3. Neither technique increases fall risk or significantly delays mobilization 1, 7.
Important Caveats
The critical limitation of PENG block is inadequate coverage of the surgical incision site 1. For anterior or anterolateral approaches to the hip, this may result in inadequate incisional analgesia despite excellent joint pain control. The guideline evidence base for fascia iliaca block is substantially more robust, with multiple meta-analyses supporting its efficacy 1, 5. However, the most recent high-quality comparative studies (2021-2024) consistently demonstrate PENG block superiority for postoperative analgesia and motor sparing 2, 3, 4, 8, 7.
Both blocks should be integrated into multimodal analgesia including acetaminophen, NSAIDs, and consideration of local infiltration analgesia 1, 6.