人工椎体的发展与应用

Development and application of artificial vertebral body

人工椎体在治疗脊柱肿瘤、结核、骨折等疾病方面取得了较好的效果。目前人工椎体种类繁多、各有利弊,总体分为融合型与可动型2类,融合型根据高度能否调节及自稳性强弱分为支撑固定型、可调固定型、自固定型3三类,自固定型又因轴套螺纹旋转结构有高度能否调节之分;可动型因球窝关节或镂空结构等可动装置的存在代替了椎间盘的功能,一定程度上保留了脊柱的活动度。人工椎体的制作材料目前包括金属、陶瓷、生物材料及高分子复合材料等多种材料,金属以钛合金为主导,至今已发展至第3代,但仍存在表面生物活性不佳等缺陷;陶瓷以羟基磷灰石复合材料、磁性生物陶瓷、多晶氧化铝陶瓷等为代表,但是存在着加工复杂、力学性能参差不齐等缺陷;生物材料主要以异种骨为主,其结构与性能与人体骨最为接近,但是存在韧性低、制作复杂等缺陷;高分子复合材料因生物学特性总体分为生物降解型与非降解型,分别以聚乙交酯与聚乙烯为代表,各有利弊。假体的设计及制作材料虽取得了较大进步,但尚难以完全满足脊柱内置物的苛刻要求,有待进一步优化。3D打印技术使假体复杂结构的加工以及个体化定制成为可能,具有广阔的发展前景,但制作周期长、成本高等缺陷有待克服。虽然人工椎体在治疗脊柱疾病方面疗效显著,但不乏假体松动、移位的报道,加之评价标准不统一,随访时间短,其确切疗效有待进一步观察。

Artificial vertebral body has achieved good results in treating spinal tumors,tuberculosis,fracture and other diseases. Currently,artificial vertebral body with variety of kinds and pros and cons,is generally divided into two types：fusion type and movable type. The former according to whether the height could be adjusted and strength of self-stability is divided into three types：support-fixed type,adjust fixed type and self-fixed type. Whether the height of self-fixed type could be adjusted is dependent on structure of collar thread rotation. The latter is due to mobile device of ball and socket joints or hollow structures instead of the disc which retains the activity of the spine to some extent. Materials of artificial vertebral body include metals,ceramics,biomaterials,polymer composites and other materials. Titanium with a dominant role in the metal has developed to the third generation,but there are still defects such as poor surface bioactivity; ceramics with the representative of hydroxyapatite composite,magnetic bioceramics,polycrystalline alumina ceramics and so on,which have the defects of processing complex and uneven mechanical properties;biological material is mainly dominated by xenogeneic bone,which is closest to human bone in structure and properties,but has defects of low toughness and complex production;polymer composites according to biological characteristics in general consists of biodegradable type and non biodegradable type which are respectively represented by poly lactide and polyethylene,each with advantages and disadvantages. Although the design and materials of prosthesis have made great progress,it is difficult to fully meet requirements of spinal implants and they need be further optimized. 3 D printing technology makes process of the complex structure of prosthesis and individual customization possible and has broad development prospects. However,long production cycles and high cost of defect should be overcome. Although artificial vertebral body has achieved curative effect in treating spinal disease,there were reports of implant loosening or displacement. Combining with evaluation standards not unified,short follow-up time,its exact effect needs further observation.