Abstract
Background
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.
Methods
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.
Results
No statistically significant decrease of the initial density was observed after compaction for BL and PC. In CB a statistical significant decrease of the initial density by 10% was observed, while PG decreased its initial density after compaction by 13%. Considering the density at the yield limit before and after compaction BL showed a statistically significant decrease of 13% and PG of 14%. In CB and PC no statistically significant decrease of the density at the yield limit could be observed. All groups showed a statistical significant difference when comparing the yield limit before and after compaction. BL and PC showed a ∼35% higher yield limit after compaction, while in the groups with the activation liquid CB and PG the yield limit increased by 15% for CB and 20% for PG.
No statistically significant difference between groups was found for the density at the yield limit before compaction (p=0.157), for the initial density (p=0.523), the density at the yield limit (p=0.681) and the yield limit itself (p=0.423) after compaction. A statistically significant difference between the groups under investigation was found for the initial density before compaction (p=0.041) and for the yield limit before compaction (p=0.041). BL had a statistically significant lower initial density than PG (p=0.048). All other pairwise comparisons between groups did not reach statistically significance for the initial density before compaction.
Conclusion
Adding blood, PRP or PC in allografts has shown in different studies to enhance bone ingrowth. The authors recommend to chemical clean allografts for large defects, optimize their grain size distribution and add platelet concentrate or platelet rich plasma for enhancing as well primary stability as well bone ingrowth. The recommended processing procedure has to be tested in an in-vivo study.
