AN IN-VIVO BIOMECHANICAL ANALYSIS OF THE SOFT TISSUE ENVELOPE OF OSTEOARTHRITIC KNEES

Abstract

A ligament tensioning device was used during total knee arthroplasty procedures to determine the effective stiffness of the soft tissue envelope around osteoarthritic knees. This information was used to calculate the resting forces on polyethylene components in well balanced knees. Various patient and implant factors were investigated to see if they correlated with the stiffness of the soft tissues around arthritic knees. The effective stiffness of the soft tissues was found to be higher when the posterior cruciate ligament was preserved compared to when it was sacrificed.

The purpose of this study was to determine, in vivo, the effective stiffness of the soft tissue envelope around the knee and to estimate the resting force on the implanted polyethylene component during total knee arthroplasty (TKA). A ligament tensioning device was used to measure displacement between the tibia and the femur versus load during eighty-six consecutive TKA procedures. A maximum of five measurements were made in both flexion and extension. The measurements were taken after bone cuts were made and soft tissue balancing was performed. The effective stiffness of the knee soft tissue envelope was determined in flexion and extension. Post- operative range of motion was measured while the patient was still under anesthetic. There was no significant difference in the average effective stiffness between men and women or between flex-ion and extension. Age did not appear to correlate with effective stiffness. The average effective stiffness was significantly higher in posterior cruciate retaining knees compared to those in which the posterior cruciate was sacrificed. There was no statistical significance between the average resting force on the polyethylene in men versus women, in flexion versus extension, or in posterior cruciate retaining knees versus posterior cruciate sacrificing knees. The immediate post-operative range of motion did not correlate with the resting force on the implanted polyethylene