The use of resorbable implants has always been attractive to surgeons because there is no need to remove implant ai'ter fracture fixation. Other advantages include decreased load sharing, multi-taskirv ancl no metal toxicity. But the strength and stiffness of resorhable implants are less than those of metallic implants. Therefore, these implants are suitahle for fixation of particular fractwre sites such as cancellous bone and epiphyscs in which shear loads comprise the major strains. The purpose of this experimental study was to determine whether there are changes in mechanical properties and tissue reactions in the polylactic acid (PLA) rod hy surface moditication using plasma coating or hexafluoropropylene (CF3CF=CF2). PLA rods were inserted into the subcutaneous tissue of back and distal femur in rabbits. Rods in subcutaneous tissue were retrieved for material characterization and those in distal femur were ohtained for histologic observation at postoperative 2, 5, 12 and 16 weeks. The results were as follows; 1. The hydrophobicity of PLA surface was successfully ohtained by plasma coating of hexatluoropropylene gas. 2. Thcre is no significant change in tissue reaction. between controi and plasma coating PLA group. 3. The diametral strength and 3-points bending strength of plasma coating groups were higher than those of control group until postoperative 12 wks, but, diminished at postoperative 16 weeks. In conclusion, the plasma coating of PLA rod using fluorocarbon is a reasonable technique to incrcase the surface hydrophohicily and a promising method to delay the reduction of the strength of PLA rod. Further study on thicker plasma coating and Jong term effect including degradation, nsetaholism and excretion of cotated fluorocarhon will be needed.
Femur ; Fracture Fixation ; Hydrophobic and Hydrophilic Interactions* ; Plasma* ; Rabbits ; Subcutaneous Tissue