EFFECT OF INTRAMEDULLARY POLYMETHYLMETHACRYLATE AND AUTOGENOUS CANCELLOUS BONE ON HEALING OF FROZEN SEGMENTAL ALLOGRAFTS

This study was designed to compare bone mineral density, periosteal ca llus production, new bone formation, bone porosity, histologic appeara nce, and union of mid-diaphyseal segmental allografts of the femur sta bilized with an interlocking nail technique in a canine model 6 months after the procedure. An in vivo study was performed to compare the ef fects of augmenting interlocking nail fixation with an interlocking na il alone, intramedullary polymethylmethacrylate, intramedullary polyme thylmethacrylate and autogenous cancellous bone applied to the periost eal surface of the host-allograft junction, autogenous cancellous bone applied to the endosteal surface of the allograft, autogenous cancell ous bone applied to the periosteal surface of the host-allograft junct ion, and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the all ograft. There were no differences among treatments for bone mineral de nsity at any time interval. Callus area 4 weeks after the procedure wa s greater along the lateral and cranial surfaces for treatments with p eriosteal cancellous bone (p < 0.05). New bone within the allograft se gment did not differ among treatments and was reduced compared with th e host-allograft junctions (p < 0.05). The amount and quality of bone tissue at the host-allograft junctions were greatest with treatments o f 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 wi th other treatments (p < 0.05). The results suggest that augmenting in terlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that a combination of intramedullary p olymethylmethacrylate and cancellous bone at the periosteal surface or of cancellous bone within the medullary canal and at the periosteal s urface improves the quality of healing at 6 months.