title: Displacement of the hip center of rotation after arthroplasty of Crowe III and IV dysplasia: a radiological and biomechanical study.
abstract: To study the direction and biomechanical consequences of hip center of rotation (HCOR) migration in Crowe type III and VI hips after total hip arthroplasty, post-operative radiographs and CT scans of several unilaterally affected hips were evaluated. Using a three-dimensional model of the human hip, the HCOR was moved in all directions, and joint reaction force (JRF) and abductor muscle force (AMF) were calculated for single-leg stance configuration. Comparing to the normal side, HCOR had displaced medially and inferiorly by an average of 23.4% and 20.8%, respectively, of the normal femoral head diameter. Significant decreases in JRF (13%) and AMF (46.13%) were observed in a presumptive case with that amount of displacement. Isolated inferior displacement had a small, increasing effect on these forces. In Crowe type III and IV hips, the HCOR migrates inferiorly and medially after THA, resulting in a decrease in JRF, AMF, and abductor muscle contraction force.
authors.affiliation: Department of Orthopedic Surgery, Shafa Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mansour
authors.initials: M
authors.lastname: Abolghasemian
authors.forename: Saeid
authors.initials: S
authors.lastname: Samiezadeh
authors.forename: Davood
authors.initials: D
authors.lastname: Jafari
authors.forename: Habiba
authors.initials: H
authors.lastname: Bougherara
authors.forename: Allan E
authors.initials: AE
authors.lastname: Gross
authors.forename: Mohammad T
authors.initials: MT
authors.lastname: Ghazavi
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D011859:Radiography; D012399:Rotation