Monitoring femoral component installation using vibration testing

With emerging minimally invasive surgical techniques in total hip arthroplasty, there has been anecdotal evidence of an increase in fractures associated with the insertion of the prosthesis into the femur. The diminished visibility associated with minimally invasive surgical techniques necessitates a greater emphasis on the surgeon's tactile and auditory senses. These senses are used to ascertain the femoral component position of maximum stability and interference fit, as well as to prevent further component impaction and subsequent fracture of the femur. The work described herein attempts to identify a means to supplement the surgeon's tactile and auditory senses by using damage identification techniques normally used in civil and mechanical structures to monitor the insertion process of the prosthesis. It is hypothesized that vibration characteristics of the impact process may be used intraoperatively to determine at what position the femoral component has reached appropriate interference fit and stability in the femur. Such information may be used to prevent further impaction of the femoral component past a threshold that could result in a periprosthetic fracture. A piezoelectric accelerometer and impact hammer will be used to monitor the impact process. The acceleration time history data were analyzed by using low and high pass filters to allow frequency analysis of the time history signals. This paper will summarize features derived from the measured data that will be used to develop an insertion process termination indicator.