DESIGN, ANALYSIS, AND FABRICATION OF A COMPOSITE SEGMENTAL BONE-REPLACEMENT IMPLANT

A composite material of polyetheretherketone and short, chopped E-glas s fibers was used to produce a segmental bone replacement implant. Pro blems with current metal implants include stress-shielding of the surr ounding bone and subsequent loosening of the implant. A better match b etween the bulk material properties of the implant and the bone it rep laces can decrease the occurrence of these problems. Composite materia ls were chosen because their properties can be tailored to match the r equirements. Material selection was done with the aid of modeling soft ware, which predicted the composite properties based on its compositio n and fiber directional parameters. A finite element model was develop ed to produce numerical results to illustrate the effect on bone cause d by a mismatch in elastic properties between the bone and the im plan t materials. Predicted stress gradients, through the bone, cement, and implant material layers, showed an obvious advantage of almost doubli ng the amount of load absorbed by the bone when using the less stiff c omposite implant than with the metal implant. Prototype parts, complet ed through a series of in-house molding and machining processes, were characterized both destructively and non-destructively to verify the i ntegrity of the material properties and processing techniques. Section s of the composite implant complete with an embedded metallic porous s urface, for bony ingrowth and fixation, were rested and measured a hig h strength of attachment.