ARTIFICIAL NUCLEUS PULPOSUS FOR DEGENERATIVE LUMBAR SPINE

退行性椎间盘（IVD）的刚度改变会影响整个腰椎的运动，并成为腰背部问题的原因。目前正在开发的人工椎间盘将解决这个问题，但所需的手术与前路椎间融合手术一样具有侵入性。髓核替代物可作为退行性腰椎疾病的替代治疗方法。为了获得退行性腰椎力学状态的基本信息，在本研究中，我们使用视频透视检查了整个腰椎的运动模式，并测量了弯曲运动期间的椎间盘内压力，以了解在实际运动中椎间盘受到的力。在透视镜下记录了志愿者（n=14，年龄22.4）和CLBP患者（n=13，年龄46.3）和退行性椎体滑脱患者（n=8，年龄63.5）的腰椎矢状位运动视频，受试者从站立的中立位向前弯曲，然后恢复到原来的位置。这些视频以每秒5帧的速度被转换成静止图像。测量从L2-3到L5-S1的椎间盘角度来估计矢状面旋转。在T2中矢状位MR图像上评估椎间盘退变。在对照组（志愿者）中，9人表现出顺序扩散运动，1人表现出同步运动，3人表现出混淆的起点。前屈运动通常从上节段扩散到下节段，但6例退行性椎体滑脱患者表现出紊乱模式。与对照组相比，患者在某一节段运动减少、持续屈曲和早期伸展更常见。一个节段的僵硬度降低会影响节段的运动模式，导致整个腰椎的运动模式改变。在测量椎间盘内压力的实际运动和同步变化之前，我们研究了换能器导管的有效性。采用尸检时获得的5个人道L3-L4脊柱单元。在导管尖端所在的任何部位（IVD的前、后、外侧部分），椎间盘内压力没有统计学上的变化。测量的压力也没有根据导管尖端的方向变化。在体内，我们测量了手术中待融合的三个节段的椎间盘内压力。受试者从中立站立位置移动，向前弯曲，并循环向后弯曲。站立压力为600-1000mmHg。刚开始向前弯曲时，压力急剧上升至2000mmHg，而角运动只有0.6度。这种增加的压力被认为是由椎旁肌肉收缩引起的。当受试者继续向后弯曲时，中性位周围的椎间盘内压力比开始时低。水凝胶被认为是代替髓核的一种理想的高密度聚合物。然而，具有较强力学性能的材料并不像水凝胶那样存在，应该加以开发。这需要进一步的深入研究。少

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 … More 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