title: The effect of bone growth onto massive prostheses collars in protecting the implant from fracture.
abstract: Limb-sparing distal femoral endoprotheses used in cancer patients have a high risk of aseptic loosening. It had been reported that young adolescent patients have a higher rate of loosening and fatigue fracture of intramedullary stems because the implant becomes undersized as patients grow. Extracortical bone growth into the grooved hydroxyapatite-coated collar had been shown to reduce failure rates. The stresses in the implant and femur have been calculated from Finite Element models for different stages of bone growth onto the collar. For a small diameter stem without any bone growth, a large stress concentration at the implant shoulder was found, leading to a significant fracture risk under normal walking loads. Bone growth and osseointergration onto the implant collar reduced the stress level in the implant to safe levels. For small bone bridges a risk of bone fracture was observed.
authors.affiliation: Department of Mechanical Engineering, University College London, Torrington Place, WC1E 7JE London, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Fromme
authors.affiliation: Institute of Orthopaedics and Musculo-Skeletal Science, Division of Surgery & Interventional Science, University College London, Royal National Orthopaedic Hospital, Stanmore HA7 4LP, UK. Electronic address: g.blunn@ucl.ac.uk.
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Blunn
authors.affiliation: Royal National Orthopaedic Hospital, Brockley Hill, Stanmore HA7 4LP, UK.
authors.forename: William J
authors.initials: WJ
authors.lastname: Aston
authors.affiliation: Department of Mechanical Engineering, University College London, Torrington Place, WC1E 7JE London, UK.
authors.forename: Tasneem
authors.initials: T
authors.lastname: Abdoola
authors.affiliation: Institute of Orthopaedics and Musculo-Skeletal Science, Division of Surgery & Interventional Science, University College London, Royal National Orthopaedic Hospital, Stanmore HA7 4LP, UK.
authors.forename: Jacob
authors.initials: J
authors.lastname: Koris
authors.affiliation: Institute of Orthopaedics and Musculo-Skeletal Science, Division of Surgery & Interventional Science, University College London, Royal National Orthopaedic Hospital, Stanmore HA7 4LP, UK.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Coathup
mesh_terms: D000293:Adolescent; D001846:Bone Development; D002648:Child; D017886:Durapatite; D055119:Elastic Modulus; D005269:Femur / Q000254:growth & development*; D020342:Finite Element Analysis; D006801:Humans; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical
chemical_list: D017886:Durapatite
keywords: Bone growth; Finite Element Analysis; HA collar; Orthopaedics; Prostheses