A COMPUTER AIDED MEASURING SYSTEM FOR CONTACT PRESSURE DISTRIBUTION IN ARTIFICIAL KNEE JOINT

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The replacement surgery of artificial knee joint is usually indicated for the severely damaged knee. Although many kinds of artificial knee joints have been developed and utilized in clinical treatment, a reoperation is needed . in some cases to treat such complications as loosening of prosthesis due mainly to technical failure.A microcomputer aided measuring system was newly developed, which allows the measurement of contact pressure distribution in artificial femoro-tibial joint during operation in order to prevent the eccentric load in the knee. The system was composed of a measuring apparatus where twelve pressure sensors are buried in the trial of tibial component and a microcomputer for analyzing pressure and displaying visually the changes in pressure distribution. A knee actuator with another microcomputer system was also designed and developed so as to give. continuously various patterns of both quantitative knee-motion(joint angle) and loading(foot force) to the knee joint as walking, standing up from a chair, stepping up and down the stairs, and so on.By combining the contact pressure measuring system and the knee actuator, the experimental investigations were made using cadaveric knee joints. The results strongly suggested that the conventional method for evaluating success or failure of the replacement of artificial knee using plain roentogenogram has a certain limitation and the dynamic three dimensional evaluation for the positioning of the prostheses presented herein is quite important.Conclusively, the microcomputer aided measuring system appears to be useful and helpful for evaluating the positioning of the prosthesis during replacement surgery.