During a bone marrow biopsy of the iliac crest, which position allows access to the site?

• A. Lying flat on the back
• B. Prone
• C. Side-lying
• D. Standing

Answer: (B)

Positioning for a bone marrow biopsy from the iliac crest relies on exposing the posterior crest so landmarks are easy to feel and the needle can be directed straight into the bone. Being prone accomplishes this: with the patient lying face down, the gluteal muscles relax, the pelvis is stabilized, and the posterior iliac crest (where this biopsy is typically taken) sits closest to the skin, making it easy to locate the posterior superior iliac spine and insert the needle perpendicular to the bone. This setup also helps minimize movement and improves accuracy.

Lying on the back makes the posterior crest harder to access and landmarks less obvious, side-lying can complicate stabilization and landmark identification, and standing prevents a controlled, fixed approach.