|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1996 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1995 : ¥600,000 (Direct Cost : ¥600,000)
The altered stiffness of the degenerated intervertebral disc (IVD) would affect a motion of the whole lumbar spine and be a cause of low back problems. An artificial intervertebral disc, being developed these days, will solve this problem, but the required surgery is as invasive as anterior interbody fusion operation. A substitute for nucleus pulposus can be an alternative treatment of degenerative lumbar disease. To obtain a basic information of the mechanical status of the degenerative lumbar spine, in this study, we examined the motion pattern of the whole lumbar spine using videofluoroscopy and measured intradiscal pressure during bending motion to know how much force is applied to the intervertebral disc in an actual motion.
Lumbar sagittal motion videos were recorded under a fluoroscope in volunteers (n=14 ; age 22.4) and patients with CLBP (n=13 ; age 46.3) and degenerative spondylolisthesis (n=8 ; age 63.5), while the subjects bent forward from a standing neutral position and th
en returned to the original position. The videos were converted to still images at 5 frames per second. Disk angles from L2-3 to L5-S1 were measured to estimate sagittal rotation. Disk degeneration was evaluated on T2 mid-sagittal MR image.
In the control group (volunteers), 9 exhibited sequentially spreading motion, one exhibited simultaneous motion, and 3 showed confused starting points. the anterior bending motion is usually spread from the upper segment to the lower one, but six of the patients with degenerative spondylolisthesis showed disordered patterns. Decreased motion, persistent flexion, and earlier extension in a certain segment were more frequently seen in the patients than in controls. The decreased stiffness of one segment would affect the segmental motion pattern, resulting in the altered motion pattern of the whole lumbar spine.
Before measuring the actual motion and the simulataneous change of the intradiscal pressure, we studied a validity of a transducer catheter. Five humane L3-L4 spinal unit obtained at autopsy was used. The intradiscal pressures did not change statistically at any site (anterior, posterior, lateral portion of the IVD) where the tip of the catheter was located. The pressure measured did not also change according to the direction of the tip of the catheter.
In vivo we measured the intradiscal pressure in three segments to be fused at an operation. The subject moved from the neutral standing position, bending forward, and bent backward cyclically. The pressure on standing was 600-1000mmHg. Just after beginning to bend forward, the pressure raised steeply up to 2000mmHg, while the angular motion was only 0.6 degrees. This increased pressure was thought to be from paravertebral muscle contraction. When the subject continued to bend backward, the intradiscal pressure got lower around the neutral position than that of the beginning.
Hydrogel is thought to be a ideal type of a high density polymer for a substitute of nucleus pulposus. However, materials with strong mechanical property did not exist as a hydrogel, and should be developed newly. This needs further advanced research. Less