Needling depth at BL52 in 13 cadavers.

BACKGROUND BL52 is located 3 cun lateral to the lower border of the spinous process of the L2 vertebra. The needling pathway includes the skin, subcutaneous tissue, latissimus dorsi muscle, intrinsic muscles of the back, quadratus lumborum muscle, the dorsal branches of the second lumbar artery and vein, and the lateral branches containing fibres from the second lumber spinal nerve. Deep perpendicular needle insertion at this location in the lower back risks damage to the kidneys, which are located in the dorsal region of the abdominal cavity within the retroperitoneal space.