An approach to the design and the development of total artificial hip joint

number: 
879
English
Degree: 
Author: 
Hassanain A. L. Mossa
Supervisor: 
Dr. Albert E. Yousif
year: 
2004
Abstract:

Joint replacement is a very efficient surgical treatment for severe joint diseases, and it has the best cost / benefit ratio of all major surgical operations. One of the most common and successful processes in the orthopedics is the total hip arthroplasty, which is performed most often to reduce pain and restriction of movement of the human hip joints that have presented problems for a sizeable proportion of the population. Many designs, materials and technologies of prosthetic devices for the hip joint have decreased the risk and improved the long-term success of the total artificial hip joint. This study demonstrates how analytical and mathematical models may be used to evaluate prospective components for the design and development of total artificial hip joint, which is important to verify the immediate outcome of the hip replacement. These advances have detailed as describing the measurements of loading forces and temperature of the hip joint through the use of instrumented hip implants. A mathematical model to determine the contact forces and moments components acting from the acetabular cup to the femoral head of implant during different types of activity is presented. Also, it has described an electronic system for detecting the hip prosthesis loosening based on a mechanical vibration analysis. Although current artificial hip systems work quite well, reducing the slow rate of wear can further improve the success of this operation. The amount and type of wear produced in the prosthetic hip joint depends on the type of relative motion between the femoral head and acetabular cup. The wear of the acetabular cup, ( socket ), can limit the life of the implant, and it may cause a significant problem if the surface of the femoral head (ball) is damaged which resulting in loosening of the fixation of the implant, and this is the most frequent short-term failure mode of the prosthetic joints. A revision operation must be performed, but it is considered more difficult and expensive than the primary operation, and the results are generally not as good. Also, the study presents an analytical model to estimate the wear rate of the commonly existed material combinations of the articular surfaces based on a previous model in which the cup wear over a gait cycle was calculated under the simplifying assumption of an ideal rigid coupling. The contact pressure is evaluated ton the basis of Herzian theory of the elastic contact of two bodies with non-conforming geometrical shapes. The wear factor was taken from hip simulator wear tests. The wear volume was estimated mathematically from the measurements with reasonable accuracy. Studies on retrieved hip prostheses are currently performed in order to assess the wear mechanisms and the overall wear rate of such artificial joints.