Magnetic three-dimensional dynamic tracking of total knee arthroplasty can detect rotational movements within one degree accuracy in most configurations: new principles for medical imaging.

Authors

Abstract

The laboratory-based study aimed to evaluate the utility and accuracy of a device in tracking the rotation of total knee arthroplasty (TKA) implants. The Kneematics device has two sensor units, comprising an emitter and four detector coils, positioned medially and laterally on a brace. Alternating magnetic fields generate eddy currents on the metallic implant surfaces, inducing a secondary magnetic field. Detectors convert these into a voltage output that varies with changes in implant pose. A neural network estimated the kinematics of the implants from voltage readouts, using an experimental setup comprising two robotic arms, the Kneematics device, and implants. Sensitivity was tested by shifting the knee from its trained central position in multiple directions and by substituting the largest implant size with the smallest. Device accuracy was reported as the number and proportion of outliers (±1°) for each degree of freedom. The accuracy was 94-98% and 97-99% for femoral rotations, and 94-99% and 91-99% for tibial rotations, using the largest and smallest components positioned centrally, respectively. When the TKA was positioned in five different positions, the accuracy was 94-99% for femoral rotations and 83-99% for tibial rotations. The Kneematics device reliably tracked all three rotational degrees of freedom of the femur and tibia within 1° accuracy in over 90% of configurations. This laboratory validation demonstrates the Kneematics device's efficacy and robustness for multiple implant sizes and positions, which provides a basis for continued development and translation to clinical use. Level V.

Tags

Topics