Processing of allografts, which are used to fill bone defects in orthopaedic surgery, includes chemical cleaning as well as gamma irradiation to reduce the risk of infection. Viable bone cells are destroyed and denaturing proteins present in the graft the osteoconductive and osteoinductive characteristics of allografts are altered. The aim of the study was to investigate the mechanical differences of chemical cleaned allografts by adding blood, clotted blood, platelet concentrate and platelet gel using a uniaxial compression test. The allografts were chemically cleaned, dried and standardized according to their grain size distribution. In group BL 4 ml blood, in CB 4 ml blood and 480 μl of 1 mol calcium chloride to achieve clotting, in PC 4 ml of concentrated platelet gel, in PG 4 ml of concentrated platelets and 666 μl of 1 mol calcium chloride were added. Uniaxial compression test was carried out for the four groups before and after compating the allografts.Background
Methods
Allografts are used to compensate for bone defects resulting from revision surgery, tumor surgery and reconstructive bone surgery. While it is well known that the reduction of fat content of allografts increases mechanical properties, the content of liquids were not assessed with known grain size distribution so far. The aim of the study was to compare the mechanical properties of dried allografts (DA) to allografts mixed with a saline solution (ASS) to allografts mixed with blood (AB) having a similar grain size distribution. Fresh-frozen morsellized bone chips were cleaned chemically, sieved and reassembled in specific portions with known grain size distribution. A uniaxial compression was used to assess the yield limit of the three groups before and after compaction with a fall hammer apparatus. No statistically significant difference could be found between all three groups for the yield limit (p=0.339) before compaction. After compaction no statistically significant difference could be found between DA and ASS (p=0.339) and between ASS and AB (p=0.554). AB showed a statistically significant higher yield limit than DA (p=0.022). At the yield limit 3 outliers were removed in DA, 1 in ASS and 1 in AB before compaction and 2 in DA and 1 in AB after compaction. Excluding the effect of the grain size distribution on the mechanical properties it was shown that allografts have a lower yield limit, when lipids are present. The liquid content of allografts seems to play an inferior role as no statistically significant difference could be found between DA and ASS. It is suggested in accordance with other studies to chemical clean allografts before implantation to reduce the contamination risk and the fat content. An optimum liquid level still remains to be defined. The considerations here described are relevant for filling up bigger bone defects, while in smaller defects the differences between different preparation methods may be less prominent.
BAG-S53P4 has similar mechanical properties as cortical bone tissue and can be used as an additive to bone allografts. The aim of this study was to evaluate the effect of adding BAG-S53P4 to chemically treated allografts with controlled grain size distribution. Allografts were prepared and chemically cleaned under sterile conditions. 30 samples were mixed with BAG-S53P4 additive (BG) and compared to a control group (CG) with similar grain size distribution and composition in weight. All samples underwent a uniaxial compression test after compaction with a dropped weight apparatus. The yield limit was determined by a uniaxial compression test and density was recorded. The two groups were tested for statistical differences with the student's t-Test.Introduction
Methods
