Hip Prosthesis

In this chapter, an exhaustive literature review on the works reported in the area of hip prosthesis has been presented. Literatures available in the area of hip prosthesis are broadly classified into the following categories.
• Biomechanics of Hip Joint.
• Implant Materials and Its Biocompatibility.
• Variations in Femur Geometry.
• ISO 7206-4 Fatigue testing standard for hip implants.
• Experimental stress and fatigue testing of hip implants.
• Stress and Fatigue analysis of hip implants by Finite element method.
2.2 Biomechanics of Hip Joint.
A complex system of forces act at the hip joint, generated by the muscles and the inertial forces of the human body acting through the mechanical interfaces of the femur and the pelvis. There

Rydell (1966) determined peak loads of 1.59 and 1.76 times body weight for a subject with a weight of 735N and peak loads of 2.95 and 3.27 times body weight for a subject of 441N for level walking at speeds of 0.9 and 1.3m/s.
English and Kilvington (1979) used an instrumented femoral implant with strain gauges positioned in the neck to measure dynamic hip loads in vivo. For the one subject examined in the study a peak load of 2.56 times body weight was recorded when the subject was walking at 0.44m/s, 12 days post surgery.
One example of a telemetric proximal implant has been presented by a group from the Orthopaedic Engineering Laboratory, Case Western Reserve University Clevland U.S.A (Davy et al. 1988; Kotzar et al. 1991; Kotzar et al. 1995). Davy, Kotzar and co-workers have used an implant based on the geometry of the DF80 Zimmer implant. The neck of the implant has been modified to include an electronic cavity, a battery, board clip, oscillator board, transmitter board, hip cap, and the prosthesis

2001). One of the useful additions of the recent paper is that is also includes a CD containing the results (Bergmann 2001). The importance of the torsional moment in the transverse plane is again emphasized, with the author also stating that the other two components of the total moment are specific to the definition of the centre of rotation and are also of little significance.
The average peak magnitude of the resultant hip contact force was approximately 238% BW for walking at a speed of 4km/h. The –Fy component, which causes much of the implant torque is larger when going upstairs than for level walking. The –Fy component was found to be higher when going downstairs than for going upstairs; and was found to be very small when sitting down. The peak forces measured when standing on one leg were similar to the forces produced when walking.
Bergmann et al. [10] use instrumented hip implants on different patients and forces were recorded for various ‘Average peak loads’ and ‘high peak loads’