Novel Method for Testing Cementless Tibial Components Using Micromotion and Impedance Vibration Analysis

INTRODUCTION: The initial mechanical stability of cementless implants is critical to achieve successful osseointegration through minimization of deleterious micromotion. Controversy exists regarding the most reliable and appropriate methodology for in vitro mechanical testing of implants used to guide design and performance of cementless total knee replacement. Mechanical testing methods vary within the literature, both with respect to the applied loads to simulate in vivo forces, as well as the devices used to assess the micromotion and stability. Established methodology involves the use of linear variable differential transducers (LVDT) to measure micromotion; however, LVDT’s are limited by varying specifications, mechanical quality, and difficulty constructing a test apparatus to accurately acquire data in three planes of motion. The objective of this study was to assess whether vibration analysis methods via structural impedance measurements are capable of identifying and characterizing initial mechanical stability of cementless tibial implants. A second objective was to establish a precise and clinically relevant method of assessing initial mechanical stability and micromotion of tibial implants in 6 degrees of freedom.