What is the recommended approach for Quadratus lumborum (QL) block techniques?

Quadratus Lumborum Block Techniques: Clinical Comparison and Recommendations

Direct Answer

The anterior quadratus lumborum (QL) block is the most clinically relevant approach when a QL block is indicated, though current evidence remains limited with only one randomized controlled trial showing benefit at 24 hours for hip arthroplasty, and fascia iliaca block remains the preferred regional technique for most lower abdominal and hip procedures due to superior safety profile and more robust evidence. 1

Evidence Quality and Clinical Context

The evidence base for QL blocks is notably weak compared to other regional techniques:

• Only one RCT exists evaluating anterior QL block versus no block in hip arthroplasty, showing lower morphine consumption and pain scores at 24 hours but not at other time points 1
• The 2021 PROSPECT guidelines for hip arthroplasty explicitly state that anterior QL block is not recommended due to limited procedure-specific evidence 1
• For cesarean section, QL blocks provide similar analgesia to intrathecal morphine but do not demonstrate superiority when directly compared 2

Anatomical Spread Patterns of Different QL Approaches

QL1 (Lateral QL Block)

• Spreads primarily in the transversus abdominis plane (TAP) 3
• Most superficial approach with limited proximal spread 3
• Does not consistently reach paravertebral spaces 3

QL2 (Posterior QL Block)

• Spreads in the TAP and posterior aspect of QL muscle 3
• Intermediate depth with variable cranial extension 3
• Inconsistent thoracic paravertebral spread 3

QL3/Anterior QL Block (Transmuscular or Transverse Oblique Paramedian)

• Spreads in the anterior aspect of QL muscle between QL and psoas 3, 4
• Cadaveric studies show involvement of L1-L3 nerve roots and lumbar plexus branches (femoral, lateral femoral cutaneous, ilioinguinal, iliohypogastric nerves) 5, 4
• Does NOT consistently spread to thoracic paravertebral space despite earlier cadaveric suggestions 3
• No sacral plexus involvement (L5 or below) 4
• Provides T10-L3 dermatomal coverage in clinical cases 4

Clinical Algorithm for Regional Technique Selection

For Hip Arthroplasty:

1. First-line: Fascia iliaca block - recommended as preferred nerve block with no increased fall risk, lower pain scores, reduced morphine consumption, and shorter length of stay 1
2. Alternative: Local infiltration analgesia (LIA) - equivalent pain outcomes to fascia iliaca block 1
3. Avoid: Anterior QL block - insufficient evidence (single RCT only) 1
4. Avoid: Femoral nerve block - significant muscle weakness incidence affecting mobilization 1, 6
5. Avoid: Lumbar plexus block - deep block with potential risks including neuraxial spread and hematoma 1, 6

For Liver Surgery:

1. First-line: Continuous wound infiltration (CWI) with or without TAP blocks - lower complication rates and equivalent analgesia to epidural 1
2. Consider: QL blocks - one RCT (n=63) showed benefit in reducing opiate requirements 1
3. TAP blocks reduce opiate requirements in multiple RCTs including cirrhotic patients 1

For Cesarean Section:

1. If spinal anesthesia used: Intrathecal morphine - most practical and effective for majority of patients 2
2. If intrathecal morphine contraindicated or history of severe opioid side effects: QL block - provides similar analgesia with better early mobilization and gastrointestinal function 2
3. Do NOT add QL block to intrathecal morphine - no additional benefit 2

Critical Safety Considerations

Motor Block Concerns:

• Femoral nerve block causes significant motor weakness affecting quadriceps function and delaying mobilization 1, 6
• Lumbar plexus block has highest risk of neuraxial spread and deep hematoma formation 1, 6
• QL blocks appear to have motor-protective effects compared to lumbar plexus approaches 7

Technical Execution:

• Ultrasound guidance is essential for all QL block approaches to ensure proper fascial plane identification 3, 5
• The transverse approach (LQL-T) provides more consistent spread than longitudinal approach 8
• Injection site matters: anterior QL spread differs significantly from lateral or posterior approaches 3, 5

Common Pitfalls to Avoid

1. Assuming QL blocks reach thoracic paravertebral space: 3D-CT imaging in patients shows QL3 does NOT consistently spread to thoracic paravertebral areas despite cadaveric data suggesting otherwise 3

2. Using QL blocks when better-evidenced alternatives exist: For hip arthroplasty, fascia iliaca block has multiple meta-analyses supporting efficacy and safety, while QL block has only one RCT 1

3. Expecting sacral coverage: QL blocks do not provide L5 or sacral nerve coverage 4

4. Performing QL blocks after intrathecal morphine: Timing matters - QL blocks performed after cesarean section under spinal with intrathecal morphine do not improve outcomes 2

When QL Block May Be Appropriate

• Liver resection as part of multimodal analgesia when epidural is contraindicated 1
• Cesarean section when intrathecal morphine is contraindicated or patient has high risk for opioid-related side effects requiring early mobilization 2
• Abdominal surgery requiring T10-L3 coverage when TAP block alone is insufficient 5, 4