Intrathecal ligaments and nerve root tension: possible sources of lumbar pain during spaceflight.
Lumbar intrathecal ligaments have recently been demonstrated to randomly bind dorsal nerve roots to the dura within the lumbar vertebral column. Lengthening of the vertebral column and associated lumbar back pain experienced by astronauts is common in microgravity. This study was designed to investigate the relationship of lumbar intrathecal ligaments in spinal lengthening as a possible mechanism for back pain.


METHODS
A two-part study was designed using 36 vertebral columns from embalmed cadavers. There were 12 vertebral columns studied in mid-sagittal section to demonstrate the possible movement of the spinal cord during lengthening of the vertebral column. The remainder were assessed for the amount of tension placed on a dorsal nerve root by the lumbar intrathecal ligament during lengthening of the vertebral column.


RESULTS
The spinal cord moves in a cephalic direction approximately 2.8 mm with 4 cm lengthening of the vertebral column. During lengthening, a loss of thoracic and lordotic curvature was noted with an increase in disk height. Tension was significantly increased on the dorsal nerve roots being tethered by the lumbar intrathecal ligaments in comparison to non-tethered nerve roots during lengthening of the vertebral column.


CONCLUSIONS
A significant amount of tension is placed on dorsal nerve roots tethered by intrathecal ligaments within the lumbar spine during spinal lengthening. These ligaments randomly bind dorsal nerve roots in the lumbar spine and may be involved in the back pain experienced by astronauts in microgravity.
Kershner
David
D
University of Nebraska Medical Center, Department of Genetics, Cell Biology, and Anatomy, Omaha, NE 68198-6395, USA. Kershner@medscape.com
Binhammer
Robert
R
D002908:Chronic Disease; D006801:Humans; D008022:Ligaments / Q000503:physiopathology*; D017116:Low Back Pain / Q000209:etiology*; D008161:Lumbosacral Region / Q000503:physiopathology*; D016273:Occupational Exposure; D011843:Radiculopathy / Q000503:physiopathology*; D013026:Space Flight; D013131:Spine / Q000503:physiopathology; D014893:Weightlessness / Q000009:adverse effects*