Ceramic bone graft substitute with equine bone protein extract is comparable to allograft in terms of implant fixation: A study in dogs

Background and purpose: We studied whether osseointegration and fixation of plasma-sprayed titanium implants grafted with β-TCP granules (Ossaplast) can be improved by adding an osteogenic signal (Colloss E). The results were compared to implants grafted with fresh frozen morselized allograft with and without the Colloss E device. Methods: 4 porous-coated Ti implants were placed in the proximal humeri in each of 10 dogs. All implants were surrounded by a 2.5-mm defect, which was grafted with: (A) β-TCP, (B) β-TCP+20 mg Colloss E, (C) allograft, or (D) allograft+20 mg Colloss E. The observation time was 4 weeks. Results: Mechanical testing showed that the β-TCP group with Colloss E was twice as well fixed as the control group grafted with β-TCP granules alone, and comparable to both allograft groups. We found that every control implant in the β-TCP grafted group was covered by a dense fibrous membrane. No fibrous tissue was seen in the β-TCP group augmented with Colloss. These implants were well osseointegrated, with new bone covering 10-25% of the implant surface. Both treated groups had increased graft resorption compared to their respective control groups. Colloss E had no effect on new bone formation or fibrous tissue reduction around the allografted implants. Interpretation: The Colloss E device improved early osseointegration of implants grafted with β-TCP granules and increased their mechanical implant fixation to the level of allografted implants. The experiment indicates that ceramic bone substitutes may be a viable alternative to allograft when combined with an osteogenic signal such as Colloss E.