title: A novel multi-planar radiography method for three dimensional pose reconstruction of the patellofemoral and tibiofemoral joints after arthroplasty.
abstract: Determining the 3D pose of the patella after total knee arthroplasty is challenging. The commonly used single-plane fluoroscopy is prone to large errors in the clinically relevant mediolateral direction. A conventional fixed bi-planar setup is limited in the minimum angular distance between the imaging planes necessary for visualizing the patellar component, and requires a highly flexible setup to adjust for the subject-specific geometries. As an alternative solution, this study investigated the use of a novel multi-planar imaging setup that consists of a C-arm tracked by an external optoelectric tracking system, to acquire calibrated radiographs from multiple orientations. To determine the accuracies, a knee prosthesis was implanted on artificial bones and imaged in simulated 'Supine' and 'Weightbearing' configurations. The results were compared with measures from a coordinate measuring machine as the ground-truth reference. The weightbearing configuration was the preferred imaging direction with RMS errors of 0.48 mm and 1.32 ° for mediolateral shift and tilt of the patella, respectively, the two most clinically relevant measures. The 'imaging accuracies' of the system, defined as the accuracies in 3D reconstruction of a cylindrical ball bearing phantom (so as to avoid the influence of the shape and orientation of the imaging object), showed an order of magnitude (11.5 times) reduction in the out-of-plane RMS errors in comparison to single-plane fluoroscopy. With this new method, complete 3D pose of the patellofemoral and tibiofemoral joints during quasi-static activities can be determined with a many-fold (up to 8 times) (3.4mm) improvement in the out-of-plane accuracies compared to a conventional single-plane fluoroscopy setup.
authors.affiliation: University of British Columbia, Vancouver, British Columbia, Canada. shahramiri@gmail.com
authors.forename: Shahram
authors.initials: S
authors.lastname: Amiri
authors.forename: David R
authors.initials: DR
authors.lastname: Wilson
authors.forename: Bassam A
authors.initials: BA
authors.lastname: Masri
authors.forename: Gulshan
authors.initials: G
authors.lastname: Sharma
authors.forename: Carolyn
authors.initials: C
authors.lastname: Anglin
mesh_terms: D000465:Algorithms; D001178:Arthroplasty / Q000379:methods; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D002138:Calibration; D004581:Electronics; D004867:Equipment Design; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology*; D005471:Fluoroscopy / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000502:physiology; D008953:Models, Anatomic; D009038:Motion; D010329:Patella / Q000000981:diagnostic imaging / Q000502:physiology*; D019047:Phantoms, Imaging; D011859:Radiography / Q000379:methods*; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*