title: Bilateral tibial components of different cementless designs and materials. Microradiographic, backscattered imaging, and histologic analysis.
abstract: Postmortem evaluation was conducted on two cementless knee prostheses considered clinically successful. The two retrieved uncemented porous-coated tibial components of different designs, and materials were evaluated by microradiography, backscattered electron (BSE) imaging, and light microscopy. The right prosthesis, in place for 25 months, was a Porous-Coated Anatomic (PCA) implant with double-layered, sintered, cobalt-chromium alloy beads. The left prosthesis was a Natural-Knee (N-K) implant with a porous coating of cancellous-structured pure titanium implanted for 19 months. A quantitative microradiographic index, the appositional bone index (ABI), was developed to indicate the probability of bone ingrowth occurring into the porous coating. The ABI is a ratio of bone in apposition with porous coating divided by the total amount of porous coating available. The PCA had an average ABI of 9%, and the N-K, 67%. BSE images of the PCA demonstrated no bone within the porous coating. BSE images of the N-K implant showed bone ingrowth into 22% of the pore volume when porous coating was in apposition to host bone. Histology of the PCA revealed fibrous connective tissue throughout the porous coating and between the porous coating-bone interface. Histology of the N-K implant revealed bone ingrowth and osteoblastic activity along the bone within the porous coating.
authors.affiliation: Department of Veterans Affairs Medical Center, Bone and Joint Research Laboratory, Salt Lake City, Utah 84148.
authors.forename: R D
authors.initials: RD
authors.lastname: Bloebaum
authors.forename: D M
authors.initials: DM
authors.lastname: Rhodes
authors.forename: M H
authors.initials: MH
authors.lastname: Rubman
authors.forename: A A
authors.initials: AA
authors.lastname: Hofmann
mesh_terms: D000368:Aged; D001842:Bone and Bones / Q000648:ultrastructure; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D007720:Knee Prosthesis; D008297:Male; D008852:Microradiography; D008855:Microscopy, Electron, Scanning / Q000379:methods; D016062:Porosity; D011474:Prosthesis Design