Study of discovering the effect of instrumentation after open reduction internal fixation on knee contact pressures was conducted with sawbones. Four sawbones were utilized, although only two of those, #3172 and #3181, were analyzed for this study because the other two lacked data to compare with the control. For sample #3172, uniaxial loading with average body weight of women and 2.5 times the body weight was done in two conditions: before fixation and with fixation. The process was repeated with sample #3181, which also employed the two types of loading to account for the load variability on knee while walking. In comparison to sample #3172, additional measurements were taken for sample #3181 after removing the plate, to examine if the contact pressure restored its value after the removal. Peak cartilage pressures and the histograms in different conditions were compared to observe the change in pressure with changing conditions. The results of sample #3172 were capricious and ambiguous to conclude whether the fixation had an impact on the contact pressure. Nevertheless, comparison of the pressure of sample #3181 at initial condition with that after the fixation showed a clear increase in contact pressure. With body weight force, the maximum pressure of medial pressure increased from 2.4 MPa to 3.48 MPa. Also, an extra increase in pressure after removal of the plate was noted, which was not as expected. With body weight force, the maximum contact pressure increased from 3.48 MPa to 4.03 MPa. This shows that instrumentation of hardware increases stress on the knee, and retention of hardware does not restore back the pressure. Some sources of error include damage in the sensors, inconsistent location of the sensors, and discrepancy in contact surfaces between the condyles during instrumentation.

Document Type

Final Report

Author's School

McKelvey School of Engineering

Author's Department

Mechanical Engineering and Materials Science

Class Name

Mechanical Engineering and Material Sciences Independent Study

Date of Submission