BACKGROUND: Previous experiments demonstrated that low-temperature isotropic pyrolytic carbon has excellent biological features. However, the research regarding low-temperature isotropic pyrolytic carbon prosthesis in hip joints, especially the biological features following hemiarthroplasty are poorly understood. OBJECTIVE: Utilizing implantation experiment, the aim of this study was to investigate the biocompatibility, as well as the interface wear properties of carbon femoral head prosthesis, coated with low-temperature isotropic pyrolytic carbon (silicon). DESIGN, TIME AND SETTING: In vivo hemiarthroplasty, randomized controlled animal experiment. The experiment was performed at the Experimental Animal Center, the Second Military Medical University of Chinese PLA, from October 2008 to April 2009. MATERIALS: Carbon femoral head prostheses.were supplied by Jilin Central Hospital. The carbon femoral head prosthesis was coated with low-temperature isotropic pyrolytic carbon. METHODS: Carbon femoral head prostheses were implanted in 16 adult New Zealand white rabbits. The rabbits were sacrificed at weeks 6 (n=4), 11 (n=6), 21 (n=6), respectively. Rabbits in the 21-week group were induced to move from 18 weeks with 2 hours per day. MAIN OUTCOME MEASURES: The biocompatibility and the interface wear phenomena of the prostheses were investigated by general observation, X-ray observation and tissue slice observation. RESULTS: The carbon femoral head prostheses implanted in animals produced non-toxic side effects, without significant inflammatory response or foreign body reaction. Furthermore, new cartilage tissue around carbon prosthesis was found, while there was no obvious wear debris after sports experiments. CONCLUSION: The film coating carbon materials have excellent biocompatibility and good wear resistance as femoral head prosthesis. Thus, it is a kind of promising biomaterials in prosthesis manufacturing.

Objective: To evaluate the effect of core∶dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered IPS Empress Ⅱceramic composite specimens. Methods: IPS EmpressⅡ core ceramic, dentin porcelain and bilayered composite specimens with core∶dentin thickness ratio of 2∶1 and 1∶1 were tested in three-point flexure strength. Mean strengths and standard deviations were determined. The optical microscopy was employed for identification of the fracture mode and origin. Results: The flexure strength of dentin porcelain was the smallest (62.7 MPa), and the strength of bilayered composite specimens was smaller than single-layered core ceramic(190.2 MPa). The core∶dentin ratio did not influence the strength of bilayered composite specimens. The frequency of occurrence of bilayered specimen delaminations was higher in the group of core∶dentin thickness ratio of 1∶1 than in the group of 2∶1. Conclusion: IPS Empress Ⅱcore ceramic was significantly stronger than veneering dentin porcelain. Core∶dentin thickness ratio could significantly influence the fracture mode and origin, and bilayered IPS Empress Ⅱceramic composite specimens showed little influence in the fracture strength.

Total hip replacement is a very effective method to cure many kinds of hip joint illnesses. About a century ago, it was first used in clinic. Since then, total hip replacement has been well developed. Hip joints sustain the most load of body, so people pay great attention to the hip prothesis' mechanics property. Especially after the finite element analysis was widely used in biomechanics investigation, the stress distribution of different designs can be easily compared with each other, and the relatively better parameters of the design could be decided. The stress distribution of different materials with the same design also can be valued. However, studies have indicated that total hip joint replacement still has some disadvantages. Loosening of the hip prothesis is still the most likely cause of the failure of surgery, and generally this is believed to stem from either mechanical failure of the fixation in response to over high density stresses, or osteolysis of the surrounding bone stock responsing to particular wear debris. Many researchers on computational studies have considered the potential for the former one, but only a few have attempted to tackle the latter. The process of osteolysis of the bone is not yet completely known. Nowadays, in order to solve the problems of loosening, investigators are trying to find different methods. Some of them are working on improving the geometry parameters and the shape of the hip prothesises, some are trying to find new suitable biomaterials, and, at the same time, the fixation methods are under deliberation.
Arthroplasty, Replacement, Hip ; adverse effects ; Computer-Aided Design ; Finite Element Analysis ; Humans ; Prosthesis Design ; Prosthesis Failure ; Stress, Mechanical ; Weight-Bearing