Design and fabrication of poly DL-lactic acid biodegradable fusion cage of the lumbar vertebrae / 中国组织工程研究

ABSTRACT

BACKGROUND:Metal vertebral fusion cage can induce some disadvantages and pseudoarticulation formation such as stress dodge,fusion cage subsidence,bone resorption,prolapse and bone collapse.Biodegradable absorbing material-made vertebral fusion cage can avoid disadvantages mentioned above.There are no studies on correlation of material function to design of absorbing fusion cage of lumbar vertebrae.OBJECTIVE:To design and fabricate the poly DL-lactic acid biodegradable fusion cage of lumbar vertebrae,and to analyze the material characteristics.DESIGN,TIME AND SETTING:The material in vivo experiment was performed at the Chengdu Institute of Organic Chemistry of Chinese Academy of Sciences from January 2003 to December 2006.MATERIALSTwenty dogs aged 12 months were obtained from Animal Laboratory of West China,Sichuan University.Poly DL-lactic acid biodegradable fusion cage of lumbar vertebrae was produced by the Chengdu Institute of Organic Chemistry of Chinese Academy of Sciences.METHODS:According to the anatomical characters and measured data of lumbar intervertebral disc,we designed the poly DL-lactic acid biodegradable fusion cage of lumbar vertebrae.The rectangle cage consists of two styles23 mm and 25 mm,13 mm in width,and 9,10,11 and 12 in depth(anterior wall).The depth was small half-moon shape from anterior to posterior,and the posterior wall was thinner than anterior wall about 1.5mm to accord with the shape of intervertebral discs.The depth of four walls of the fusion cage was 2.5 mm,with several 1-mm diameter holes on bilateral walls.The posterior wall had 3.5-mm diameter spiral hole,which was used for connecting with the implanted tool.Using precise shaping processing craft,the produce process was DL-lactic acid→raw material storage→lactide preparation→lactide purification→polymerization→drying package→product.After general anesthesia,bilateral thighs were incised in 20 dogs,and then a fusion cage was implanted into each dog to detect compressive strength and viscosity in the process of biodegradation.MAIN OUTCOME MEASURES:Preparation of fusion cage;compressive strength and viscosity in the process of biodegradation in vivo.RESULTS:The size of the products is 23 mm?13 mm?10 mm and the appearance of the products were saw tooth shape,which could prevent the slide,enhance the solid strength between fusion cage and the surface of vertebra.Small holes on the bilateral wall were beneficial for vascular growth and nutrient fluid exchange,resulting in bony fusion.Compressive strength and viscosity decreased at 3,6 and 9 months after implantation(r=0.961,P=0.009),but compressive strength and viscosity were good at 12 months(163 MPa and 0.66 dl/g).CONCLUSION:Poly DL-lactic acid biodegradable fusion cage has a big loading implanted bone mass and high stability.The integrity and supportive effect of the fusion cage can meet the requirement of bony fusion.