Intraosseus pressure in the lumbar spine is defined as the hydrostatic pressure of venous blood in the trabecular sinusoids of cancellous bone. Measurements of it in the lumbar vertebrae and the inferior vena cava confirm that the intraosseus pressure in the lumbar spine is identical to, and dependent upon, the pressure in the inferior vena cava. With Valsalva maneuver in the decubitus position, the pressure reaches levels of 90 mm Hg in the inferior vena cava and intraosseus space of lumbar spine.