Objective: The objective of this study was to compare the influence of different hyperthemic processes (autoclave and microwave oven) on the morphologic and thermodynamic properties of collagen.
Summary and Background Data: The current thinking regarding the treatment of human bone tumors is a radical excision, attempting to preserve the function of the limb. An acceptable method for limb preservation is reimplantation of the affected bone after the debridement of gross tumor tissue and sterilization by means of autoclave. This hyperthermic processing technique provides a perfectly sized graft, but it is associated with a decline in the mechanical and biological properties of the bone. A previous study demonstrated that sterilization using a microwave kills all viable cells with a minimal decrease in the mechanical and biological properties of the bone. Possible explanation of this phenomenon is preservation of matrix protein such as collagen. The current study’s goal was to investigate the effect of different hyperthermic treatments on native collagen.
Materials and Methods: In this study we used Heilistat-absorbable collagen sponge (American biomaterials corporation, Plainsboro, NJ 08536). This collagen was divided into three study groups. The first group was processed in the autoclave, the second in a microwave oven and the third which served as the control group received no thermal treatment. The thermodynamic properties of these three groups were checked by Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis (TGA). The morphological structure was examined by Scanning Electron Microscope (SEM), Phillips. Accelerating Voltage 30 KV.
Results: Thermodynamic properties: The peak temperature and the amount of energy invested showed similar results in the control group and in the microwave group, and differed from the results of the group treated by autoclave. The graphs of TGA, which represent the weight decrease as a function of heating, were also similar in the microwave group and the control group.
The morphological structure of the collagen, namely, the architectural structure of the material and single fibers, as shown by the SEM in various magnifications (100, 1200, 2500 and 5000), was much more similar when comparing between the control group and the microwave group than in the autoclave processed group.
Conclusion: Hyperthermic treatment using a microwave oven has minimal effect, if any, on the native collagen of bone, causing only minimal damage to the morphological and thermodynamic properties of bone. This observation may explain the biological superiority of the microwave treatment over autoclave treatment of bone.
