Anatomic localization of lumbar spinal nerve root and the determination of compression in rats

Objective To investigate the anatomic lumbar nerve root localization and to measure the degree of compression induced by silastic tube implantation in rats. Methods Eighteen pure New Zealand rabbits, weighing from 2.5 kg to 3.0 kg, were randomly allocated into 2 groups:group A ( n =6), in which the animals were dissected according to the geometrical principles to localize the lumbar spinal nerve roots, and the length of spinal nerve, the angle to the dura matter, and the anatomical characteristics such as the diameter of the spinal nerve at the external intervertebral foramen and the sagittal area of the foramen were measured; group B ( n =12), from which the extent of compression of intervertebral foramen was measured by using the sectional anatomic techniques after the artificial implantation of a silastic tube was performed. Results The length of lumbar intervertebral canal, the angle and area of intervertebral foramen varied at various lumbar intervertebral spaces; the length of the spinal nerve root was 5.83 ±1.18mm at L 5～6 and 8.94±1.64mm at L 6～7 , its angles to the dura matter were 55.2±11.1° and 29.6± 4.2° , respectively, on condition that the measured sectional area of the silastic tube was 20% of the sagittal area of the intervertebral canal and 50% of the area of the external intervertebral foramen. Conclusion The animal models of spinal nerve root compression established in this experimental study is similar to that seen in clinical settings. It is suggested that high successful intubation rate and slim possibility of injury to the spinal cord can be expected if it is manipulated in the way described above.