title: Factors influencing the stability of stems fixed with impaction graft in vitro.
abstract: Mechanical stability of the stem is believed to be an important factor in successful impaction grafting in revision THA. We asked whether particle size, femoral bone deficiencies, stem design, graft composition, and impaction technique influenced the initial stability of the stem in vitro using model femora and human bone particles. Bone particles made with a reciprocating blade-type bone mill contained larger particles with a broader size distribution than those made by a rotating drum-type bone mill and had higher stiffness on compression testing. The stiffness on torsional testing decreased as the degree of proximal-medial segmental deficiencies increased. The stiffness and maximum torque in a stem with a rectangular cross section and wide anteroposterior surface were higher in torsional tests. Adding hydroxyapatite granules to the bone particles increased the torsional stability. To facilitate compact bone particles, we developed a spacer between the guidewire and modified femoral packers. This spacer facilitated compacting bone particles from the middle up to the proximal and the technique increased the amount of impacted bone particles at the middle of the stem and also improved the initial stability of the stem. Stem design and degree of deficiencies influenced stiffness in the torsional test and the addition of hydroxyapatite granules enhanced torsional stiffness.
authors.affiliation: Department of Orthopaedic Surgery, Saiseikai Nakatsu Hospital, 2-10-39, Shibata, Kita-ku, Osaka, 530-0012, Japan. LU7H-OOHS@asahi-net.or.jp
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Ohashi
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsuura
authors.forename: Tsuneyuki
authors.initials: T
authors.lastname: Ebara
authors.forename: Yusaku
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Hironori
authors.initials: H
authors.lastname: Kou
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D018786:Bone Substitutes; D016025:Bone Transplantation; D005269:Femur / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D006882:Hydroxyapatites; D066298:In Vitro Techniques; D008422:Materials Testing; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D014182:Transplantation, Autologous
chemical_list: D018786:Bone Substitutes; D006882:Hydroxyapatites