Calcium phosphate sol–gel-derived thin films on porous-surfaced implants for enhanced osteoconductivity. Part II: Short-term in vivo studies

Osseointegration rates of porous-surfaced Ti6Al4V implants with control (unmodified sintered coatings) were compared to porous-surfaced implants modified through the addition of either an Inorganic or Organic Route-formed-Ca–P film. Implants were placed in distal femoral rabbit condyle sites and, following a 9-day healing period, implant fixation strength was evaluated using a pull-out test. Three groups of ten rabbits each were evaluated. Inorganic Route Ca–P-coated implants were compared with control implants in Group I. Organic Route Ca–P-coated implants with control implants in Group II, and Inorganic- with Organic Route-Ca–P-coated implants in Group III. Maximum pull-out force and interface stiffness were compared while selected extracted implants were examined by SEM to characterise failure surfaces. Both types of Ca–P coatings significantly enhanced the early rate of bone ingrowth and fixation as evidenced by higher pull-out force and interface stiffness compared with controls. However, there was no significant difference between Ca–P-coated implants prepared using the two different methods. The enhanced osteoconductivity observed with the Organic Route-formed films despite the absence of any obvious new surface topographic features introduced with the films suggests that the increased rate of bone ingrowth was due primarily to altered surface chemistry rather than changes in topography, at least for these sintered porous-surfaced implants.