title: Validation of three-dimensional model-based tibio-femoral tracking during running.
abstract: The purpose of this study was to determine the accuracy of a radiographic model-based tracking technique that measures the three-dimensional in vivo motion of the tibio-femoral joint during running. Tantalum beads were implanted into the femur and tibia of three subjects and computed tomography (CT) scans were acquired after bead implantation. The subjects ran 2.5m/s on a treadmill positioned within a biplane radiographic system while images were acquired at 250 frames per second. Three-dimensional implanted bead locations were determined and used as a "gold standard" to measure the accuracy of the model-based tracking. The model-based tracking technique optimized the correlation between the radiographs acquired via the biplane X-ray system and digitally reconstructed radiographs created from the volume-rendered CT model. Accuracy was defined in terms of measurement system bias, precision and root-mean-squared (rms) error. Results were reported in terms of individual bone tracking and in terms of clinically relevant tibio-femoral joint translations and rotations (joint kinematics). Accuracy for joint kinematics was as follows: model-based tracking measured static joint orientation with a precision of 0.2 degrees or better, and static joint position with a precision of 0.2mm or better. Model-based tracking precision for dynamic joint rotation was 0.9+/-0.3 degrees , 0.6+/-0.3 degrees , and 0.3+/-0.1 degrees for flexion-extension, external-internal rotation, and ab-adduction, respectively. Model-based tracking precision when measuring dynamic joint translation was 0.3+/-0.1mm, 0.4+/-0.2mm, and 0.7+/-0.2mm in the medial-lateral, proximal-distal, and anterior-posterior direction, respectively. The combination of high-speed biplane radiography and volumetric model-based tracking achieves excellent accuracy during in vivo, dynamic knee motion without the necessity for invasive bead implantation.
authors.affiliation: University of Pittsburgh, Department of Orthopaedic Surgery, Orthopaedic Research Laboratories, 3820 South Water Street, Pittsburgh, PA 15203, USA. anderst@pitt.edu
authors.forename: William
authors.initials: W
authors.lastname: Anderst
authors.forename: Roger
authors.initials: R
authors.lastname: Zauel
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bishop
authors.forename: Erinn
authors.initials: E
authors.lastname: Demps
authors.forename: Scott
authors.initials: S
authors.lastname: Tashman
mesh_terms: D001696:Biomechanical Phenomena; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000502:physiology; D008954:Models, Biological; D019919:Prosthesis Implantation; D012420:Running; D012680:Sensitivity and Specificity; D013635:Tantalum; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology* / Q000601:surgery; D014057:Tomography, X-Ray Computed
chemical_list: D013635:Tantalum