Determining relevance of a weight-bearing ovine model for bone ingrowth assessment

A weight-bearing ovine model was used to quantify cancellous bone ingrowth and remodeling in porous-coated implants over 6, 12, and 24 weeks in situ. The null hypothesis for the investigation was that there would be no significant difference between the amount of cancellous bone ingrowth and rate of remodeling in this ovine model compared to a reported human bilateral implant model. Bone ingrowth progressed from 20.1 +/- 8.2% at 6 weeks in situ to 23.8 +/- 7.9% at 12 weeks, and 30 +/- 5.1% at 24 weeks. Fluorochrome analysis demonstrated a mineral apposition rate of 1.07 +/- 0.28 microm/day for bone at the porous-coating interface, whereas host bone remodeling at 0.89 +/- 0.23 microm/day. Histological analysis showed no adverse tissue or inflammatory response. The null hypothesis was supported in that regression analysis demonstrated that the amount of cancellous bone ingrowth over time (p = 0.545) and mineral apposition rate over time (p = 0.089) in this ovine model was not significantly different than reported human bilateral knee data. The results of this study appear to validate the ovine model for use in understanding skeletal attachment of porous-coated implants to cancellous bone in humans.