title: Accuracy of a computer-assisted navigation system for total knee replacement.
abstract: The object of this study was to develop a method to assess the accuracy of an image-free total knee replacement navigation system in legs with normal or abnormal mechanical axes. A phantom leg was constructed with simulated hip and knee joints and provided a means to locate the centre of the ankle joint. Additional joints located at the midshaft of the tibia and femur allowed deformation in the flexion/extension, varus/valgus and rotational planes. Using a digital caliper unit to measure the coordinates precisely, a software program was developed to convert these local coordinates into a determination of actual leg alignment. At specific points in the procedure, information was compared between the digital caliper measurements and the image-free navigation system. Repeated serial measurements were undertaken. In the setting of normal alignment the mean error of the system was within 0.5 degrees . In the setting of abnormal plane alignment in both the femur and the tibia, the error was within 1 degrees . This is the first study designed to assess the accuracy of a clinically-validated navigation system. It demonstrates in vitro accuracy of the image-free navigation system in both normal and abnormal leg alignment settings.
authors.affiliation: University of Auckland, and Department of Orthopaedics, Middlemore Hospital, 93311 Otahuhu, Auckland, New Zealand. RPitto@middlemore.co.nz
authors.forename: R P
authors.initials: RP
authors.lastname: Pitto
authors.forename: A J
authors.initials: AJ
authors.lastname: Graydon
authors.forename: L
authors.initials: L
authors.lastname: Bradley
authors.forename: S F
authors.initials: SF
authors.lastname: Malak
authors.forename: C G
authors.initials: CG
authors.lastname: Walker
authors.forename: I A
authors.initials: IA
authors.lastname: Anderson
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment / Q000503:physiopathology; D004867:Equipment Design; D005269:Femur; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D007866:Leg; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia