Bone growth into glassy carbon implants. A rabbit experiment

Diffusion of strontium implanted in glassy carbon

Glassy carbon has properties making it attractive as a containment material for radioactive waste. In this study, the diffusivity of the radiological important fission product, strontium, is measured. Two hundred kiloelectronvolt strontium ions were implanted at room temperature. The implanted samples were either annealed isochronally for 1 h up to 900°C or by increasing the temperature linearly up to 648°C. The Sr profiles were determined by Rutherford backscattering spectrometry (RBS). The isochronally annealed samples showed Fickian diffusion at 300°C ( D  = 6.7 × 10 −19  m 2  s −1 ) with segregation occurring at the higher temperatures. Raman spectroscopy indicated a link between damage annealing and the onset of segregation. During increasing temperature, the system is dynamic with diffusion taking place. An equation to determine diffusion coefficients for ramped heating was derived. Fickian diffusion occurred with an activation energy of 1.97 eV for 414–454°C, and from 458 to 558°C, it was 0.184 eV. At higher temperatures, a segregation of the strontium towards the surface was observed. A calculation of the heat of segregation of Sr in carbon supports this segregation. The results show that the in situ RBS measurements with a linear increase in temperature give additional information compared with the conventional isochronal annealing.

Glassy carbon implant as a bone graft substitute: an experimental study on rabbits

The purpose of this experimental investigation was to study the incorporation of porous glassy carbon in bone. Cylinders of porous glassy carbon were implanted in drill holes in diaphyses and metaphyses of rabbits tibia for 1, 3, 6, 12 and 24 weeks. Bone ingrowth into the glassy carbon implants was examined by radiographic, histologic, fluorocrome and microradiographic methods. The material caused no pathological reaction. Tissue ingrowth into pores was seen by all examination methods. The amount of bone in the pores increases with time. The ingrowth was most distinctive in those areas where the implant was in close contact with cortical bone or trabeculae of the cancellous bone. Porous glassy carbon can be used as bone substitute, although the small size of implant available is at the present a limitation for its clinical use.

Carbon fibre reinforced epoxy implants for bridging large osteoperiosteal gaps

An experimental study was undertaken to evaluate the suitability or otherwise of carbon fibre reinforced epoxy (CFRE) implants for bridging large osteoperiosteal gaps, devoid of periosteum. Using the basic principles of composite mechanics and simple design criteria, CFRE implants were designed and developed. These implants were put in simulated osteoperiosteal gaps in the ulna of healthy mature rabbits. Ten wk postoperative results clearly demonstrated that implants made of CFRE induced callus bone formation (in the form of woven bone) which totally encapsulated the implant thereby providing reunion of the two bone segments. Further follow-up showed formation of lamellar bones and formation in the pores of the implant. Radiological and scanning electron microscopical evidence is presented.

A carbon chamber for vital microscopy of bone healing

We describe a carbon chamber implanted in the ulna of fowl. A window permitted daily microscopy of bone formation including observations of tetracyline labelling. The chamber could be heated to 5 degrees above body temperature by 600 kHz radio frequency.

Shear strength of loaded porous-glassy-carbon/bone interface--an experimental study on rabbits

The aim of the study was to measure the shear strength of bone/porous-glassy-carbon interface in rabbit. Glassy carbon pellets were implanted into drill holes made through the medial articular surface of the proximal tibia of 15 rabbits. Shear strengths grew statistically significantly from 1 to 6 weeks and reached a maximum of 4.6 MN/m2. Microscopical examination of the sheared surfaces revealed that at 1 and 2 weeks the shearing occurred through the tissue surrounding the implant, and at 3, 6 and 12 weeks through the porous coating of the implant. To diminish the fragility of the porous coating, its porosity should be adjusted to 40%. Results of shear strength studies on current implant materials are reviewed.