Is hydroxyapatite cement an alternative for allograft bone chips in bone grafting procedures? A mechanical and histological study in a rabbit cancellous bone defect model

Abstract

To evaluate in vivo performance of hydroxyapatite cement (HAC) as a porous bone graft substitute, HAC was mixed (1:1 ratio) with either porous calcium-phosphate granules (80% tricalcium phosphate, 20% hydroxyapatite) or defatted morsellized cancellous bone (MCB) allograft and implanted bilaterally in cylindrical drill holes in distal femurs of rabbits. Groups with empty defects and impacted MCB were used for reference. After 8 weeks, one femur from each pair was examined histologically. All contralateral specimens and Time-0 specimens were used for mechanical indentation tests. Histology showed that some empty defects were filled with newly formed osteopenic bone after 8 weeks. The impacted MCB showed remodeling into new vital bone. Incorporation of the HAC/MCB composite was incomplete, whereas minimal new bone ingrowth was found in the HAC/granule composites. Though not different from each other, both composites were significantly stronger than empty defects, incorporated impacted MCB, and intact cancellous bone. At Time 0, the mechanical behavior of impacted MCB was similar to both HAC composites. In conclusion, composites of HAC and porous biomaterials can maintain relatively high strength over 8 weeks in vivo, but their incorporation into a new bony structure is slower than impacted MCB. The HAC/MCB composite showed favorable incorporation behavior.

In vivo micro-CT scanning of a rabbit distal femur: Repeatability and reproducibility

“…Rabbits are also advantageous compared to rats because they exhibit a predictable cessation of longitudinal bone growth after five to six months (Kaweblum et al, 1994) and should not require special processing of images to account for growth as seen with rats (Waarsing et al, 2004a). In vivo micro-CT scanning of rabbits will also complement studies involving bone graft incorporation, implant bone interfaces, and skeletal assessment which commonly use the rabbit femur model (Laffargue et al, 1999;Orr et al, 2001;Ohsawa et al, 2004;Voor et al, 2004;Bourne and van der Meulen, 2004;Saha and Wehrli, 2004;Pihlajamaki et al, 2006a;Pihlajamaki et al, 2006b;Dallari et al, 2006;Fellah et al, 2006;Takahashi et al, 2006;Wang et al, 2006;van der Meulen et al, 2006).…”

The fluid phase of morsellized bone: Characterization of viscosity and chemical composition

“…If the process is successful, the allograft forms a scaffold for new bone formation, (Eldridge et al, 1997;Kärrholm et al, 1999;Tägil and Aspenberg, 2004) enabling packed in the femur cavity, it forms a porous matrix filled with air, water and fat. Due to the particulate moist nature, models aiming at giving an understanding of the mechanical behaviour of the morsellized bone have traditionally been based on soil mechanical theory (Brewster et al, 1999;Brodt et al, 1998;Dunlop et al, 2003;Fosse et al, 2005Fosse et al, , 2006aGiesen et al, 1999;Phillips et al, 2006;Ullmark and Nilsson, 1999;Voor et al, 2000Voor et al, , 2004a. Soil mechanics is based on an effective medium approach (Biot, 1941) to develop the basic equations of poroelastic theory.…”

Clinical and radiological results of non-cement impaction bone-graft method of total hip arthroplasty for rheumatoid arthritis

“…5,6 The use of a new form of artifi cial bone such as hydroxyapatite is a recent phenomenon, but the incorporation of the granules of hydroxyapatite may need a longer period when compared with auto-bone grafting. 7,8 To avoid the use of allograft and artifi cial bone, we performed total hip arthroplasty using the non-cement impaction auto-bone-grafting method with the resected femoral head for acetabular protrusion that is not combined with the destruction of the acetabular rim or dysplasia of the hip joint. In this article, we report the detailed surgical technique and the short-term results of our cases.…”