title: A randomised RSA study of Peri-Apatite HA coating of a total knee prosthesis.
abstract: BACKGROUND
  In total knee replacement, sound early fixation of the prosthesis is crucial for achieving a good long-term result and for minimising the risk of loosening. Various types of prosthetic material, different surface textures and shapes and the incorporation of screws or pegs have been used to achieve good fixation, particularly in the uncemented knee. Hydroxyapatite (HA) coating of prosthetic joint components is another technique used to enhance early stability and so to improve the longevity of the prosthesis-bone fixation. HA ceramic coatings are mostly plasma sprayed onto the fixation surface of the implant. Plasma spraying is largely a 'line of sight' technique and as such there are difficulties involved when covering three-dimensional planes, such as porous beaded fixation surfaces typically found on several knee prostheses. The objective of this study was to assess the clinical performance of the solution-deposited HA coating, Peri-Apatite , with regard to its ability to stimulate an endurable and stable implant fixation.
  
  
  METHODS
  We randomised 60 patients into two groups; one group received the porous coated prosthesis with solution-deposited HA, and the other group received a prosthesis without HA. Radiostereometric examination was used as the primary tool for measuring migration in the prosthetic components.
  
  
  RESULTS
  There was a lower incidence of early subsidence in the Peri-Apatite group. At 24 months there were no differences in clinical scorings or maximal total point motion.
  
  
  CONCLUSIONS
  Addition of solution-deposited HA coating appears to provide better early stable fixation in a porous coated knee prosthesis.
authors.affiliation: Department of Orthopaedics, Lund University Hospital, 22185 Lund, Sweden. ulrik.hansson@med.lu.se
authors.forename: Ulrik
authors.initials: U
authors.lastname: Hansson
authors.forename: Leif
authors.initials: L
authors.lastname: Ryd
authors.forename: Sören
authors.initials: S
authors.lastname: Toksvig-Larsen
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D001672:Biocompatible Materials; D017886:Durapatite; D006801:Humans; D007720:Knee Prosthesis; D008422:Materials Testing; D020370:Osteoarthritis, Knee / Q000601:surgery; D010780:Photogrammetry; D011474:Prosthesis Design
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite