Experimental Study Of Porous Carbonated Hydroxyapatite Bone Cement

Carbonated hydroxyapatite (CHA) bone cement, which is capable of self-setting and forming the component similar with the mineral phase of natural bone, was firstly reported by constanz in 1995, and known as revolutionary progress in the orthopaedic biomaterial field. The orthopaedic department of the PLA general hospital in China and Institution of Chemistry of China Academy of Science followed the international frontier research and begun to study the CHA bone cement under the support of National Nature Science Fund Project in China in 1996. The research and a series of examination of CHA bone cement have been finished since that time and now some results have been used in the clinic. Although the CHA bone cement is similar to the mineral phase of natural bone, it is compact in structure and short of cavity. So that it leads to limit the growth of new bone into CHA bone cement and delays reconstruction from CHA bone cement to normal bone. To solve the problem, the porous carbonated hydroxyapatite (PCHA) was investigated to keep in situ setting ability and increase the degrading which would benefit the growth of natural bone.PurposeTo investigate a new method of preparing the PCHA bone cement, and to test its physicochemical properties, and to evaluate its degrading, osteogenous ability and compressive strength.Materials and Methods1. The preparation of PCHA bone cement: the vesicants were selected to adopt CHA setting ability and the PCHA was prepared. The prescription of PCHA, which suit to the growth of normal bone, was selected according to the results of porosity, diameter and connecting pore examined by scanning electron microscope, dyeing of pore and experiment impressed with hydrargyrum.2. The physicochemical examination of PCHA: comparing the property of PCHA with CHA by examine the setting time, PH, hardening strength, X-ray diffraction and fouriery transformed infrared spectroscopy.3. The toxicity and the osteogenous ability on the surface of PCHA: the toxicity was examined by coculture with PCHA to record growth of cells with MTT method. The osteogenous ability was investigated by observation of the formation and growth of cells on the surface of PCHA bone cement.4. The biodegrading experiment of PCHA: The columnar specimens (diameter, 8mm; length 14mm) were prepared from self-making PCHA. Some specimens were soaked in simulated body fluid, and the others were implanted into the back muscle of rabbits. The biodegrading ofspecimens was clarified by examination of the weight loss and histological analysis.5. The osteogenous experiment of PCHA: Bone defect models in the distal femurs of rabbits were used in this study, osteogenous rules, rate and quantification were investigated by the bone ingrowths of PCHA with the methods of X-ray, soft X-ray, fluorescence tag, histological section, and computer-aided image analysis procedure.6. The mechanical experiment of PCHA: Strength changes of PCHA in different situation were compared with CHA by experiments of soaking in simulated body fluid, implanting into back muscle of rabbits and implanting into host bone with the MTS858 mechanical machine.Results1. The preparation of PCHA bone cement: the porous rate was 36%, most of pores were distributed between the diameter of 158-394 u m and 90.23% beyond the diameter of 70 u m.2. The physicochemical proportions of PCHA: the PH was 8.6 in the setting processing. The setting time was 15 minutes. The ratio of calcium and phosphor was 1.64.3. The toxicity and the osteogenous ability on the surface of PCHA: Cytotoxicity tests demonstrated that PCHA has excellent biocompajibility, and cells grow normally on the surface of PCHA.4. The degrading experiment of PCHA: the weight loss of PCHA were increased about two times than CHA soaking in simulated body fluid, and four times implanting into back muscle of rabbits.1. The osteogenous experiment of PCHA: new bones graduall...