Experimental Study Of Self-Harding And Low Compressive Strength Bone Cement

Objective: Traditionally,PMMA was used in vertebroplasty to deal wi th spinal compression fracture caused by osteoporosis, bone tumor and tra uma.It got significantly clinical effect,meanwhile it also brought many pro blems. ,On the one hand ,during the period of its coagulation the surroun ding tissues would be hurt as heat emission.,on the other hand the toxifer ous methacrylic monomer would cause systemic acute reactions.PMMA is a inert material without the bility of biodegradation,so it would hinder theintervertebral fusion.Otherwise it would increase the fracture risk of adjac ent segments.As the particular semi-block cellular structure of cancellous bone in centrum of a vertebra,it is filled with blood,it is hard to hematischesis du ring the process of osteotomy.We attempt to use PMMA to padding the b lood sinus so as to decrease the loss of blood.But the compressive strengt h of PMMA is too hard to ectomize.In this experiment,we change the liq uid-to-powder ratio of PMMA,using SDS to change the porosity and com pressive strength of a-TCPsamples.The purpose is to search a material with low compressive strength and fine histocompatibility. Its physical structure and mechanical characters is similiar to cancellous bone.Methods: liquid-to-powder ratios of PMMA were changed ,the settingtime and compressive strength of samples were measured. The a—triacal cium phosp hate power were mixed with calcium sulphate dehydrate as a n accelerant. Liquid -to-powder ratio was used: 0.32 mL/g. Various conce ntrations of sodium dodecy lsulphate as an air-entraining agent were adde d to the liquid phase.All dataes were analyzed with SPSS software.Results: As the liquid-to-powder ratio increasing,the compressive strength of PMMA decreased,but it was still much higher than cancellous bone. Meanw hile the setting time extended along with it. The SDS did not affect either initial setting time and the final setting time. The compressive strength decreased as the SDS concentration increased.,but the porosity increased.There is a threshold at the concentration of 20mM.Comclusions: a-TCP bone cement with low compressive strength and good bone conduction is similar to cancellous bone in physical structure and mechanical characters.It is the best choice to take the place of PMMA in vertebroplasty and spine osteotomy.