Effect of intramedullary polymethylmethacrylate and autogenous cancellous bone on healing of frozen segmental allografts

This study was designed to compare bone mineral density, periosteal callus production, new bone formation, bone porosity, histologic appearance, and union of mid-diaphyseal segmental allografts of the femur stabilized with an interlocking nail technique in a canine model 6 months after the procedure. An in vivo study was performed to compare the effects of augmenting interlocking nail fixation with an interlocking nail alone, intramedullary polymethylmethacrylate, intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host- allograft junction, autogenous cancellous bone applied to the endosteal surface of the allograft, autogenous cancellous bone applied to the periosteal surface of the host-allograft junction, and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the allograft. There were no differences among treatments for bone mineral density at any time interval. Callus area 4 weeks after the procedure was greater along the lateral and cranial surfaces for treatments with periosteal cancellous bone (p < 0.05). New bone within the allograft segment did not differ among treatments and was reduced compared with the host-allograft junctions (p < 0.05). The amount and quality of bone tissue at the host-allograft junctions were greatest with treatments of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and of autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the allograft (p < 0.05). The rate of bone union was lower, and there was a greater gap (non-bone tissue) remaining between host and allograft bone with treatment involving just intramedullary polymethylmethacrylate than with other treatments (p < 0.05). The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that a combination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface or of cancellous bone within the medullary canal and at the periosteal surface improves the quality of healing at 6 months.