title: The beneficial effect of hydroxyapatite lasts: a randomized radiostereometric trial comparing hydroxyapatite-coated, uncoated, and cemented tibial components for up to 16 years.
abstract: OBJECTIVE
  In contrast to early migration, the long-term migration of hydroxyapatite- (HA-) coated tibial components in TKA has been scantily reported. This randomized controlled trial investigated the long-term migration measured by radiostereometric analysis (RSA) of HA-coated, uncoated, and cemented tibial components in TKA.
  
  
  METHODS
  68 knees were randomized to HA-coated (n = 24), uncoated (n = 20), and cemented (n = 24) components. All knees were prospectively followed for 11-16 years, or until death or revision. RSA was used to evaluate migration at yearly intervals. Clinical and radiographic evaluation was according to the Knee Society system. A generalized linear mixed model (GLMM, adjusted for age, sex, diagnosis, revisions, and BMI) was used to take into account the repeated-measurement design.
  
  
  RESULTS
  The present study involved 742 RSA analyses. The mean migration at 10 years was 1.66 mm for HA, 2.25 mm for uncoated and 0.79 mm for the cemented group (p < 0.001). The reduction of migration by HA as compared to uncoated components was most pronounced for subsidence and external rotation. 3 tibial components were revised for aseptic loosening (2 uncoated and 1 cemented), 3 for septic loosening (2 uncoated and 1 cemented), and 1 for instability (HA-coated). 2 of these cases were revised for secondary loosening after a period of stability: 1 case of osteolysis and 1 case of late infection. There were no statistically significant differences between the fixation groups regarding clinical or radiographic scores.
  
  
  CONCLUSIONS
  HA reduces migration of uncemented tibial components. This beneficial effect lasts for more than 10 years. Cemented components showed the lowest migration. Longitudinal follow-up of TKA with RSA allows early detection of secondary loosening.
authors.affiliation: Bio Imaging Group, Department of Orthopaedics, Leiden University Medical Center, the Netherlands. b.g.c.w.pijls@lumc.nl
authors.forename: Bart G
authors.initials: BG
authors.lastname: Pijls
authors.forename: Edward R
authors.initials: ER
authors.lastname: Valstar
authors.forename: Bart L
authors.initials: BL
authors.lastname: Kaptein
authors.forename: Marta
authors.initials: M
authors.lastname: Fiocco
authors.forename: Rob G H H
authors.initials: RG
authors.lastname: Nelissen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001843:Bone Cements; D017886:Durapatite; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery; D016896:Treatment Outcome
chemical_list: D001843:Bone Cements; D017886:Durapatite