Abstract
The longevity of hip prostheses is contingent on the stability of the implant within the cavity of the femur bone. The cemented fixation was mostly adopted owing to offering the immediate stability from cement-stem and cement-bone bonding interfaces after implant surgery. Yet cement damage and stress shielding of the bone were proven to adversely affect the lifelong stability of the implant, especially among younger subjects who tend to have an active lifestyle. The geometry and material distribution of the implant can be optimized more efficiently with a three-dimensional realistic design of a functionally graded material (FGM). We report an efficient numerical technique for achieving this objective, for maximum performance stress shielding and the rate of early accumulation of cement damage were concurrently minimized. Results indicated less stress shielding and similar cement damage rates with a 2D-FGM implant compared to 1D-FGM and Titanium alloy implants.
Highlights
Titanium and Titanium alloys were the preferred materials for orthopedic implants owing to their biocompatibility, excellent corrosion resistance, and their reliable mechanical performance as replacement for hard tissues [1]
Eighteen (NL = 18) lengthwise slices were produced over the graded section of each implant model and the number of crosswise slices varied from the distal to the proximal end according to the scheme in Table 1; a total of one hundred five slices were accumulated by the end of this procedure
Several optimal configurations were identified following the optimization of the implant geometry and material stiffness distribution; the values of the stress shielding and accumulated cement damage coefficients were not identical between designs
Summary
Titanium and Titanium alloys were the preferred materials for orthopedic implants owing to their biocompatibility, excellent corrosion resistance, and their reliable mechanical performance as replacement for hard tissues [1]. The lack of integration into the bone tissue in addition to implant-host stiffness incompatibility often leads to implant failure [2,3,4,5]. One of the primary causes of failure is the aseptic loosening due to poor bonding and lack of firm fixation of the implant biomaterial to the bone; in this respect, novel cemented fixations and cementless but improved implant designs that incorporate osseointegration with enhanced bioactivity were proven to increase the short- and long-term implant stability and interface bonding strength [6,7,8,9,10]. Stress shielding of the bone owing to stiffness mismatch with the material of the implant is important and can adversely affect the longterm durability and fixation of the bone-implant construct. Whether cemented or uncemented fixations were used, the stiffer implant shields the load and carrying capacity from the bone leading to reduction in bone density, bone thinning, and bone fracture [11,12,13,14,15,16]
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