AIIMS Delhi NO - 2017: Intraspinal medication is given in which IVD space?

AIIMS Delhi NO - 2017

Applied Anatomy

Easy

Appeared in: AIIMS Delhi NO - 2017

Explanation

The L4-L5 intervertebral space is the most common and safest location for administering intraspinal medication in adults.
This site is preferred because it is located well below the termination of the spinal cord (conus medullaris), which typically ends at the L1-L2 vertebral level.
Using the L4-L5 space significantly reduces the risk of iatrogenic spinal cord injury during the procedure.
Anatomically, an imaginary line connecting the superior aspects of the iliac crests (Tuffier's line) reliably intersects the L4 spinous process or the L4-L5 interspace, making it an easily identifiable landmark.

Option B: The L1-L2 space is an unsafe location for intraspinal injections in adults because the spinal cord (conus medullaris) terminates at this level. Inserting a needle here carries a high risk of causing direct, irreversible damage to the spinal cord.
Option C: The L6-L7 vertebrae do not exist in the normal human anatomy. The lumbar spine is composed of five vertebrae (L1 to L5), followed by the sacrum.
Option D: While the L2-L3 space can be used, it is less ideal and less safe than the L3-L4 or L4-L5 spaces. It is closer to the end of the spinal cord, increasing the risk of injury, especially if there is anatomical variation in the patient.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomical landmarks for intraspinal medication administration as background academic context rather than a clinical decision trigger.
Correct landmarking for lumbar puncture is a fundamental patient safety measure. A mistake can lead to serious neurological complications, including paralysis, sensory loss, and cauda equina syndrome.
Nurses are responsible for positioning the patient correctly (lateral decubitus or sitting, with maximal lumbar flexion) to open the interspinous spaces, assisting the provider, and monitoring the patient for complications post-procedure.
What if the patient is an infant? The spinal cord ends lower, around the L3 vertebra. Therefore, in infants and young children, the puncture is performed at an even lower level, typically L4-L5 or L5-S1, to ensure safety.

How to Approach the Question

First, identify the key concept of the question: the correct anatomical location for an 'intraspinal medication' injection, which is synonymous with a lumbar puncture.
Recall the critical anatomical fact about the adult spinal cord: it terminates at the level of the L1-L2 vertebrae (conus medullaris).
Based on this fact, reason that any injection must be performed well below this level to avoid injuring the spinal cord.
Evaluate the options: L1-L2 is too high and dangerous. L6-L7 is anatomically incorrect.
Compare the remaining options, L2-L3 and L4-L5. The L4-L5 space is lower and therefore significantly safer than L2-L3.
Select L4-L5 as the best and most common site, which is also easily located using the iliac crests as a landmark.

Concept Tested & Keywords

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E6 Anatomy Applied Ashalatha 4e p. 423-425

E6 Anatomy Grays 43e Vol 2 Part 2 p. 39-41