Interaction between carbon composites and bone after intrabone implantation

Candidate carbon fiber reinforced carbon (CFRC) porous implant materials were evaluated for tissue compatibility in a rat model. Six different CFRCs of constant pore size (about 30 μm) were fabricated that had 9, 12, and 17% porosity with 2‐nm3 matrix crystallites and 6, 12, and 20% at 25 nm3. They were implanted as femoral transverse diaphyseal pins that were 1.5 mm in diameter. At 5 and 45 weeks, implant and bone histologic specimens were evaluated histologically and by a scanning electron microscope and an electron microprobe. Also, regional lymph nodes and spleens were examined. By 45 weeks, direct implant–bone contact was observed over most of the interface in most specimens. At the implant surface, there was partial replacement of CFRC with host tissue. However, the microprobe showed that the implant–bone interface was chemically abrupt with no cross‐diffusion of ionic species. Besides the surface effects, there was partial filling of the implant pores with tissue, including bone organized de novo deep within. This was observed histologically and confirmed by microprobe. Lymph nodes and spleens were histologically normal, and no carbon particles were found. None of the results were influenced by porosity or matrix crystallite size over the ranges studied. In summary, these porous CFRCs are partially degraded when in contact with bone and appear substantially tissue compatible. They may be useful as scaffolds for regrowth of bone. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 289–296, 1999