Clinical observation of bone graft impaction on posterior intervertebral body fusion for lumbar spondylolisthesis

Objective To investigate the clinical effect of bone graft impaction on posterior intervertebral fusion for lumbar spondylolisthesis.Methods From January 2001 to July 2008,36 patients with lumbar spondylolisthesis were treated by

Selection of allografts for impaction bone grafting for bone defect reconstruction on the acetabular side

Objective To review the choices of allografts for bone defect reconstruction in acetabular revision surgery using the technique of impaction bone grafting.Data sources The data cited in this review were mainly obtained from articles listed in PubMed that were published from January 1993 to July 2009. The search terms were ＂impaction bone grafting＂, ＂particle size＂, ＂mechanical property＂and ＂biological behavior＂.Study selection Articles relevant to the choices of allografts and their results for bone defect reconstruction on the acetabular side were selected.Results Different choices of allografts, including the particle size, process of irradiation or fat reduction, composition and particle grade, are made to improve the survival rate of a prosthesis in acetabular revision surgery. This review,which compares both mechanical and biological factors, summarizes the experimental and clinical results for different techniques.Conclusions Fresh frozen cancellous allografts with particle sizes ranging from 7 to 10 mm are a favorable choice for reconstruction of bone defects of American Academy of Orthopedic Surgeons （AAOS） types Ⅱ （cavitary defect） and Ⅲ（combined cavitary and segmental defect） on the acetabular side. A fat-reducing procedure with saline or solvent/detergent is controversial. Adding autologous marrow into irradiated allografts, which provides reliable mechanical stability and biological safety, may be a substitute for fresh frozen allografts. Cortical bone can be a supplementary material in cases of insufficiency of cancellous allografts. Cartilage should be excluded from the graft material. Further research is required to demonstrate the best particle grade, and randomized controlled trials in clinical practice are required to obtain more information about the selection of allografts.

Effect of impaction on gene-modified cells seeded on granular bone allografts in vitro and in vivo

Background While attempting to restore bone stock, impaction bone grafting employed during revision joint surgery may result in slow and limited allograft incorporation into host bone. A new approach including gene-modified bone marrow stromal cells （BMSCs） in combination with impaction bone grafting may effectively restore bone stock and improve allograft incorporation. This study aimed to investigate the effect of impaction on gene-modified BMSCs seeded on granular bone allografts in vitro and in vivo.Methods Deep-frozen, granular, cancellous bone allografts from canines were prepared to serve as cell delivery scaffolds and were seeded with green fluorescent protein （GFP） genetically-modified BMSCs to construct cell-allograft composites. The composites were impacted in a simulative, in vitro impaction model and cultured for further analysis under standard conditions. Four Beagle dogs, treated with bilateral, uncemented proximal tibial joint hemiarthroplasty with a prosthesis, were implanted with autologous GFP gene-modified cell-allograft composites to repair the bone cavity around each prosthesis.Results A significant reduction in cell viability was observed after impaction by fluorescence microscopy in vitro.However, there remained a proportion of GFP-positive cells that were viable and functionally active, as evidenced by the secretion of GFP protein in vitro and in vivo.Conclusions Gene-modified BMSCs seeded on granular allografts were able to withstand the impaction forces and to maintain their normal functions in vitro and in vivo, in spite of a partial loss in cell viability.