The purpose of this study is to investigate the effect of HA (hydroxyapatite)-coated implant on strain distribution of long bone along the mechanical axis. A plasma-sprayed hydroxyapatite thin layer (about 50 micro, 50 m) was coated on the cylindrical implants (70mm in length and 4.76mm in diameter) of Ti-6Al-4V and Co-Cr-Mo rods. The implants were respectively harvested in the distal femur of mongrel dogs intramedullarly after immediate and twelve weeks' implantations. The whole femora were prepared for mechanical tests. Electrical-resistance strain rosettes were adhered on the four positions (anterior, posterior, medial and lateral) of femur at five levels. Mechanical tests were performed using material testing system (SINTECH 1/S. MTS) with the load of 65% body weight at the rate of 0.001 mm/sec along the mechanical axis of femur. Comparisons of strains at the anterior on the femoral surfaces and posterior sides revealed similar strain distributions, so do those at the medial and lateral sides. The strain values of immediate post-implanation were not smaller than those of the pre-implanation ones. The strain values on the implanted femur were higher than those on the intact femur. As bone ongrowth on implant surface after twelve weeks, femoral bending rigidity increased, the strains along the mechanical axis reduced and at the top of rod increased, especially for Co-Cr-Mo stem. According to this phenomenon, there would have more seriously stress shielding with time on Co-Cr-Mo stem than that on Ti-6Al-4V rod.
|Number of pages||5|
|Journal||Biomedical Engineering - Applications, Basis and Communications|
|Publication status||Published - 1994 Jan 1|
All Science Journal Classification (ASJC) codes
- Biomedical Engineering