抄録
The experiment was conducted on forty-one lower lumbar intervertebral discs of 21 freshly autopsied mature sheep and 10 lower lumbar intervertebral discs from five fresh human cadavers.
The results are summarized below.
1) In both the sheep and human cadavers the specimens consisting of one unit of vertebradisc-vertebra combination without a posterior metal fixation, the highest intradiscal pressure was noted with anterior loading (flexion) of the vetebral body, followed by posterior loading (extension) and then by neutral loading, in that decreasing order.
2) In the sheep specimens which consisted of four vertebrae and three connecting discs without a posterior fixation, the magnitude of the intradiscal pressure produced by the load on the upper and middle discs was in the following descending order according to the site of loading : vertebral arch>lateral portions>anterior portion>posterior portion>central portion. In the lower disc the order was : vertebral arch>lateral portion>posterior portion>central portion>anterior portion.
A study of the magnitude of intradiscal pressure according to the level of discs revealed that the pressure produced by either central or posterior loading was highest in the lower disc, followed by the middle and the upper discs in that descending order. With anterior loading or loading of the vertebral arch the order was : upper disc>middle disc?lower disc.
3) A study of the stress distribution against the compressive load showed that 50 to 60% of the load was born by the nucleus pulposus.
4) The intradiscal pressure produced was proportional to the amount of load applied.
5) Both in sheep and humans the intradiscal pressure produced by any type of eccentric loading was lower with a posterior metal plate fixation than without it.
6) With any type of eccentric loading the discs adjacent to the fixed disc showed an intradiscal pressure value of about 10% (average : 6%) lower than a value for a disc without fixation.
