title: Modified metaphyseal-loading anterolaterally flared anatomic femoral stem: five- to nine-year prospective follow-up evaluation and results of three-dimensional finite element analysis.
abstract: We have designed a proximal-fitting, anterolaterally flared, arc-deposit hydroxyapatite-coated anatomical femoral stem (FMS-anatomic stem; KYOCERA Medical, Osaka, Japan) for cementless total hip arthroplasty (THA) for Japanese patients with dysplastic hip osteoarthritis, using a nonlinear three-dimensional finite element analysis simulating loading conditions. The Anatomic Fit stem was modified in the region of the arc-sprayed surface, to allow more proximal appearance of spot welds. The aim of the present study was to analyze the clinical and radiographic outcomes of patients who underwent THA using this stem. We reviewed 73 consecutive patients (79 hips; 13 men 16 hips; 60 women 63 hips; age at surgery, 57.6 years, range, 35-78) who underwent cementless THA using the Anatomic Fit stem, at a follow-up period of 7.1 years (range, 5.1-9.4). Harris Hip score improved from 40.7 ± 17.1 before surgery to 91.0 ± 5.2 points at follow-up. The 7.1-year stem survival rate was 100%. Radiographs at follow-up confirmed the stability of the femoral stems within the femoral canal in all cases, with sufficient bone ingrowth. None of the patients had subsidence of the stem exceeding 2.0 mm within the femoral canal or changes in varus or valgus position of more than 2.0°. The Anatomic Fit stem provided excellent results. The nonlinear three-dimensional finite element analysis demonstrated that the stem-bone relative motion was 10 µm at the proximal end of the stem and proximal load transfer. Our analysis confirmed reduced radiolucency around the stem, minimal subsidence, appropriate stress shielding, and promising medium-term stability within the femoral canal.
authors.affiliation: Department of Orthopaedics and Rehabilitation Medicine, Faculty of Medical Sciences Department of Human and Artificial Intelligent Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan. kokubo@u-fukui.ac.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kokubo
authors.forename: Kenzo
authors.initials: K
authors.lastname: Uchida
authors.forename: Hisashi
authors.initials: H
authors.lastname: Oki
authors.forename: Kohei
authors.initials: K
authors.lastname: Negoro
authors.forename: Kouki
authors.initials: K
authors.lastname: Nagamune
authors.forename: Shogo
authors.initials: S
authors.lastname: Kawaguchi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Takeno
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yayama
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nakajima
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sugita
authors.forename: Ai
authors.initials: A
authors.lastname: Yoshida
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Baba
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D020099:Coated Materials, Biocompatible; D017076:Computer-Aided Design; D017886:Durapatite; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D020342:Finite Element Analysis; D005500:Follow-Up Studies; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D016348:Osseointegration; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome; D016474:Weight-Bearing
chemical_list: D020099:Coated Materials, Biocompatible; D017886:Durapatite