title: A procedure to estimate the origins and the insertions of the knee ligaments from computed tomography images.
abstract: The estimation of the origin and insertion of the four knee ligaments is crucial for individualised dynamic modelling of the knee. Commonly this information is obtained ex vivo or from high resolution MRI, which is not always available. Aim of this work is to devise a method to estimate the origins and insertions from computed tomography (CT) images. A reference registration atlas was created using a set of 16 bone landmarks visible in CT and eight origins and insertions estimated from MRI and in vitro data available in the literature for three knees. This atlas can be registered to the set of bone landmarks palpated on any given CT using an affine transformation. The resulting orientation and translation matrices and scaling factors can be used to find also the ligament origin and insertions. This procedure was validated on seven pathological knees for which both CT and MRI of the knee region were available, using a proprietary software tool (NMSBuilder, SCS srl, Italy). To assess the procedure reproducibility and repeatability, four different operators performed the landmarks palpation on all seven patients. The average difference between the values predicted by registration on the CT scan and those estimated on the MRI was 2.1±1.2 mm for the femur and 2.7±1.0 mm for the tibia, respectively. The procedure is highly repeatable, with no significant differences observed within or between the operators (p>0.1) and allows to estimate origins and insertions of the knee ligaments from a CT scan with the same level of accuracy obtainable with MRI.
authors.affiliation: Department of Mechanical Engineering, The University of Sheffield, Sheffield UK; INSIGNEO Institute for in silico Medicine, The University of Sheffield, Sheffield UK. Electronic address: dascani1@sheffield.ac.uk.
authors.forename: Daniele
authors.initials: D
authors.lastname: Ascani
authors.affiliation: Department of Mechanical Engineering, The University of Sheffield, Sheffield UK; INSIGNEO Institute for in silico Medicine, The University of Sheffield, Sheffield UK.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mazzà
authors.affiliation: Medacta International SA, Castel San Pietro, Switzerland.
authors.forename: Angelo
authors.initials: A
authors.lastname: De Lollis
authors.affiliation: Medacta International SA, Castel San Pietro, Switzerland.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Bernardoni
authors.affiliation: Department of Mechanical Engineering, The University of Sheffield, Sheffield UK; INSIGNEO Institute for in silico Medicine, The University of Sheffield, Sheffield UK.
authors.forename: Marco
authors.initials: M
authors.lastname: Viceconti
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008023:Ligaments, Articular / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012399:Rotation; D012984:Software; D014057:Tomography, X-Ray Computed
keywords: Affine registration; Knee ligaments; Osteometric scaling; Procrustes analysis