新型椎內與椎間固定器

Abstract

「模組脊柱積木（MSB）」係微創椎骨組裝新型「椎體內固定器」，可部分取代「椎體成型術」、「椎體後凸矯正術」，治療脊椎壓迫性骨折。以三維非線性有限元素模型分析（FEA）二種MSB結構設計與四種植入方法在脊椎力分佈。得知MSB對椎間活動之應力作用小，不產生額外負載於鄰椎間盤。以MSB植入豬體內，研究新骨MSB內形成狀況，得知MSB對骨整合具積極作用。評估微型豬去卵巢、限鈣飲食對骨質密度影響，得知其骨質密度繼續上升，人造骨質疏鬆豬模型是無效的。 「脊柱混合彈性(SHE)桿」使用鎳鈦諾內棒（NS）、聚碳酸酯聚氨酯外套（PS），為半剛性通用桿之新型「椎體間固定器」，可部分取代「後脊柱融合術」、「動態穩定系統」，矯正脊椎之退化性或變形。構建含植入椎弓螺釘、SHE棒組成之腰椎FEA，分析椎間力學效應。研究四種外徑相同SHE桿、相異NS直徑／PS厚度比例，得知SHE桿系統皆可提供足夠脊柱支撐、且溫和增加相鄰節段壓力，最佳NS／PS比為3.5／2.0毫米。若NS桿於下方1/3斷裂之最壞情況下，得知SHE桿系統仍能提供約一半脊柱支撐能力。

The modular spine block (MSB) is a novel "intravertebral fixator" that is minimally invasively implanted into the vertebrae. It is intended for use in vertebral compression fracture and will partially replace the currently commonly used "vertebroplasty" or "kyphoplasty". A three-dimensional nonlinear finite element analysis (FEA) of the osteoporotic L3 implanted with MSB was constructed. The force distribution was analyzed with 2 types of structural designs and 4 kinds of implantation methods at the adjacent segments. The MSB has little stress shielding effect on the intervertebral ROM and creates no additional loading to the adjacent disks. MSB were implanted in pigs to prove the ability of new bone formation within MSB in a porcine model. These findings suggest that MSBs have a similar positive effect on osseointegration. Meanwhile, it was also assessed whether the osteoporosis created by combined ovariectomy and calcium-restricted diets in the miniature pigs. The results demonstrated it is ineffective in achieving an artificial osteoporotic porcine model based on assessments of bone mineral density. The spinal hybrid elastic (SHE) rod is a novel "intervertebral fixator" that is a semi-rigid pedicle screw-based universal rod using an inner nitinol stick (NS) and outer polycarbonate urethane shell (PS). It is intended for use in spinal degenerative diseases and deformities and will partially replace the currently used "posterior fusion" or "dynamic stabilization systems". A 3-dimensional nonlinear FEA composed of pedicle screws, NS and PS was constructed to investigate the intervertebral biomechanical effects. Four groups had the same SHE rod diameter, but different NS diameter/PS thickness ratios. The SHE rod system provided sufficient spinal support and increased gentle adjacent-segment stress. The optimal NS diameter/PS thickness ratio is 3.5/2.0 mm. The SHE rod system affords nearly half spine support after lower third rod fracture in a worst-case scenario of the thinnest PS of the SHE rod system.