Total knee arthroplasty in the presence of large bony defects of the tibia and marked knee instability.

Twenty-six patients with severe tibial bone loss and secondary varus-valgus instability of greater than 20 degrees were treated by total knee arthroplasty using autogeneic bone as a graft in the defect. With proper filling of the resultant flexion and extension spaces, instability was corrected in 22 of the knees. Hospital for Special Surgery rating scores at one, two, and three years postsurgery were not statistically different from a matched group of total knee arthroplasty patients without bone grafts. There was no statistical difference in eventual motion or rating scores between those patients with a posterior cruciate-retaining and a posterior stabilized prosthesis. Four bone grafts demonstrated fragmentation and dissolution within the first year with implant subsidence. Needle biopsy performed one year postoperatively in nine knees in which the graft had not fragmented revealed osteocytes in the lacunae in only four grafts. In each of four further knees, there was a complete radiolucency between the graft and the tibial host bone. The overall success rate at five years was only 67%. This high failure rate has led the authors to reevaluate the use of prosthetic shims or wedges in large fragment defects but to continue to use bone grafting for smaller, circumscribed defects.