title: Histology of the bone-cement interface in retrieved Oxford unicompartmental knee replacements.
abstract: BACKGROUND
  Radiolucent lines (RLL) are commonly seen at the cement-bone interface of knee replacements, yet are poorly understood. Although thin RLL are not associated with implant loosening or poor patient outcome there is still concern that they indicate sub-optimal fixation. The primary study aim is to characterise the histology at the cement-tibia interface in Oxford unicompartmental knee replacement (UKR). The second aim is to assess whether a correlation exists between the presence of a RLL and the type of tissue that predominates at the interface.
  
  
  METHODS
  The radiology and histology of retrieved specimens of the interface from around firmly fixed tibial trays in ten patients undergoing revision between 1 and 19 years after Oxford UKR were studied.
  
  
  RESULTS
  Pre-revision radiographs showed the presence of both full and partial RLL. On contact radiographs of 5mm thick sections of the interface the total percentage of radiolucency ranged from 0 to 90% between patients. There was no consistent pattern for the distribution of radiolucency. Histological assessment demonstrated that under every tibial component there were areas where there was direct contact and interdigitation between bone and cement. The amount of direct bone-cement contact was between 19% and 95% of the tibial tray surface area. The remaining tissue was mainly fibrocartilage but there was also fibrous tissue. The presence of radiolucency was strongly inversely correlated with the percentage of cement-bone contact.
  
  
  CONCLUSIONS
  This study demonstrates that even with partial or complete RLL seen on radiographs there is still cement-bone contact, thus indicating that there is stable fixation.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford, OX3 7LD, UK. ben.kendrick@ndorms.ox.ac.uk
authors.forename: B J L
authors.initials: BJ
authors.lastname: Kendrick
authors.forename: A R
authors.initials: AR
authors.lastname: James
authors.forename: H
authors.initials: H
authors.lastname: Pandit
authors.forename: H S
authors.initials: HS
authors.lastname: Gill
authors.forename: A J
authors.initials: AJ
authors.lastname: Price
authors.forename: G W
authors.initials: GW
authors.lastname: Blunn
authors.forename: D W
authors.initials: DW
authors.lastname: Murray
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D016723:Bone Remodeling / Q000502:physiology; D002484:Cementation; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D011474:Prosthesis Design; D011475:Prosthesis Failure / Q000209:etiology*; D012086:Reoperation; D013977:Tibia / Q000473:pathology*