Study of soft tissue ingrowth into canine porous coated femoral implants designed for osteosarcomas management.

The objective of this project was to characterize soft tissue bonding to porous coated implants such as those that would be used for resection-reconstruction of osteosarcoma cases. We were interested in determining conditions which would provide both mechanical attachment of the implant to the surrounding tissue and produce a vascularized interface. In a bilateral canine implant model, both femoral mid-shafts were replaced with a porous coated cobalt-chrome segmental implant fabricated with average pore sizes of 300 microns or 900 microns. Twelve implants, six of each pore size, were used in six dogs. Two dogs were sacrificed at 2, 4, and 6 months after implantation. The soft tissue-implant interface was characterized mechanically with peel tests and histologically using light microscopy and immunohistochemistry. At all periods, a nonvascularized fibrous membrane surrounded the smaller pore size implants, without ingrowth or mechanical bonding. In contrast, a vascularized membrane developed within and around the larger pore size implants; the attachment strength increasing with implantation time. The vascularity increased in size and quantity with time. This study demonstrates the feasibility of obtaining vascularized soft tissue attachment to tumor replacement implants with appropriate porous coated implant design.