title: Validation of hip joint center localization methods during gait analysis using 3D EOS imaging in typically developing and cerebral palsy children.
abstract: Localization of the hip joint center (HJC) is essential in computation of gait data. EOS low dose biplanar X-rays have been shown to be a good reference in evaluating various methods of HJC localization in adults. The aim is to evaluate predictive and functional techniques for HJC localization in typically developing (TD) and cerebral palsy (CP) children, using EOS as an image based reference. Eleven TD and 17 CP children underwent 3D gait analysis. Six HJC localization methods were evaluated in each group bilaterally: 3 predictive (Plug in Gait, Bell and Harrington) and 3 functional methods based on the star arc technique (symmetrical center of rotation estimate, center transformation technique and geometrical sphere fitting). All children then underwent EOS low dose biplanar radiographs. Pelvis, lower limbs and their corresponding external markers were reconstructed in 3D. The center of the femoral head was considered as the reference (HJCEOS). Euclidean distances between HJCs estimated by each of the 6 methods and the HJCEOS were calculated; distances were shown to be lower in predictive compared to functional methods (p<0.0001). Contrarily to findings in adults, functional methods were shown to be less accurate than predictive methods in TD and CP children, which could be mainly due to the shorter thigh segment in children. Harrington method was shown to be the most accurate in the prediction of HJC (mean error≈18mm, SD=9mm) and quasi-equivalent to the Bell method. The bias for each method was quantified, allowing its correction for an improved HJC estimation.
authors.affiliation: Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, University of Saint-Joseph, Beirut, Lebanon; Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech, Paris, France; Gait Laboratory, SESOBEL, Beirut, Lebanon. Electronic address: ayman.assi@gmail.com.
authors.forename: Ayman
authors.initials: A
authors.lastname: Assi
authors.affiliation: Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech, Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Sauret
authors.affiliation: Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, University of Saint-Joseph, Beirut, Lebanon; Gait Laboratory, SESOBEL, Beirut, Lebanon.
authors.forename: Abir
authors.initials: A
authors.lastname: Massaad
authors.affiliation: Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, University of Saint-Joseph, Beirut, Lebanon.
authors.forename: Ziad
authors.initials: Z
authors.lastname: Bakouny
authors.affiliation: Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech, Paris, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Pillet
authors.affiliation: Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech, Paris, France.
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
authors.affiliation: Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, University of Saint-Joseph, Beirut, Lebanon; Gait Laboratory, SESOBEL, Beirut, Lebanon; Hôtel-Dieu de France Hospital, Beirut, Lebanon.
authors.forename: Ismat
authors.initials: I
authors.lastname: Ghanem
mesh_terms: D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D002547:Cerebral Palsy / Q000503:physiopathology*; D002648:Child; D005260:Female; D005684:Gait; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D011859:Radiography; D015203:Reproducibility of Results
keywords: Cerebral palsy; Children; EOS biplanar X-rays; Gait analysis; Hip joint center