Bone remodeling associated with a flexible femoral intramedullary implant.

The tissue response and bone remodeling associated with a flexible femoral intramedullary implant was evaluated. The implant consisted of wafers of porous Co-Cr-Mo alloy and microporous LTI pyrolytic carbon. Six wafers of each material were assembled in a stack and held together using a central acrylic rod. Radiography and histology demonstrated that these implants were associated with gross bone remodeling changes in the femoral shaft. The bone remodeling consisted of endosteal surface bone resorption and periosteal surface bone deposition, most likely due to a loss of structural support from the reamed medullary canal. The periosteal surface bone deposition resulted in an increase in femoral shaft diameter of 5% - 140%. The bone-implant interface consisted of a fibrous connective tissue with limited areas of bone ingrowth or bone apposition.