What is the benefit of using an oblique angle of 5-10 degrees when placing an interlaminar (between the laminae of the vertebrae) epidural (outside the dura mater) steroid injection at the L5/S1 (fifth lumbar and first sacral) level?

Benefits of 5-10 Degree Oblique Angle for L5/S1 Interlaminar Epidural Steroid Injection

Using a 5-10 degree oblique angle for L5/S1 interlaminar epidural steroid injections improves visualization of the needle tip and relevant anatomical landmarks, leading to more accurate placement and better ventral epidural spread of medication compared to traditional midline approaches.

Advantages of Oblique Angle Approach

The oblique approach offers several significant benefits:

1. Superior Visualization

   • The contralateral oblique (CLO) view provides better visualization of the needle tip and relevant radiological landmarks compared to the lateral view 1
   • This improved visualization allows for more precise needle placement and reduces the risk of complications

2. Better Ventral Epidural Spread

   • The parasagittal interlaminar (PIL) approach with slight obliquity results in significantly higher ventral epidural spread (89.7% vs 31.7% with midline approach) 2
   • Ventral epidural spread is crucial as the pathology (herniated disc, inflammation) is typically located in the ventral epidural space

3. Improved Clinical Outcomes

   • The oblique approach leads to higher rates of effective pain relief (68.4% vs 16.7% with midline approach at 6 months) 2
   • Patients receiving injections via oblique approaches require fewer total injections for pain management 2

Technical Considerations

When performing L5/S1 interlaminar epidural injections with an oblique angle:

• Optimal Angle: While studies on cervical injections suggest approximately 45-50 degrees for transforaminal approaches 3, the 5-10 degree oblique angle for interlaminar L5/S1 injections represents a more subtle adjustment that balances improved visualization with safety

• Fluoroscopic Guidance: Fluoroscopic guidance is essential for accurate needle placement, as recommended by the 2025 BMJ guideline for chronic spine pain associated with disc herniation (strong recommendation) 4

• Needle Trajectory: The oblique angle allows better plotting of the cranio-caudad needle trajectory, improving the efficiency of epidural access 1

Clinical Applications

The oblique approach is particularly beneficial for:

• Patients with radicular pain from disc herniation (strong recommendation) 4, 5
• Cases where precise medication delivery to the ventral epidural space is crucial
• Situations where anatomical landmarks are difficult to visualize with standard AP or lateral views

Safety Considerations

While the oblique approach improves visualization and accuracy, proper technique remains essential:

• Fluoroscopic guidance should always be used to confirm proper needle position before medication injection 5
• Non-particulate corticosteroids are recommended to minimize the risk of neurological complications 5
• The procedure should only be performed by experienced providers with appropriate training 4, 5

Common Pitfalls to Avoid

1. Excessive Obliquity: Angles greater than 10 degrees may increase the risk of vascular or neural structures injury

2. Inadequate Confirmation: Always confirm epidural placement with contrast before injecting medication

3. Improper Patient Selection: Ensure patients have failed conservative management and have imaging findings that correlate with clinical symptoms 5

The 5-10 degree oblique approach represents a technical refinement that significantly improves the accuracy, safety, and efficacy of L5/S1 interlaminar epidural steroid injections by enhancing visualization and optimizing medication delivery to the target pathology.