Magnetic resonance imaging of in vivo kinematics after total knee arthroplasty.

Purpose: To improve the quality of magnetic resonance imaging (MRI) on knees after total knee arthroplasty (TKA) by minimizing image artifacts caused by metallic implants, and to establish a method determining in vivo kinematics of TKA knees using MRI.

Materials And Methods: Two knee implants made of cobalt-chrome and oxidized zirconium were tested with different pulse sequences and imaging parameters. Then, in vivo kinematic MRI was performed on five well-functioning TKAs under simulated weight-bearing conditions. Kinematic measurements were made and a linear correlation test was run between the tibio- and patellofemoral measurements.

Results: The best images with minimum metallic artifacts were observed using oxidized zirconium implants, a fast spin echo sequence (FSE), thin slice thickness, and high readout gradient. TKA kinematics exhibited a large deviation from the normal kinematics and considerable patient-to-patient variability. However, significant linear correlations between tibiofemoral and patellofemoral kinematics were observed (R = -0.96, 0.92, 0.88).

Conclusion: Metallic artifacts due to orthopedic implants can be reduced in MR images for some materials, appropriate pulse sequence, and imaging parameters selection, enabling MR quantification of knee kinematics. Tibiofemoral kinematics appears to affect patellofemoral position after total knee arthroplasty.