title: Revision of unicompartmental knee arthroplasty: implants used and causes of failure.
abstract: OBJECTIVE
  to determine the causes of unicondylar knee arthroplasty failures, as well as identify the implants used and the need of bone grafting in patients undergoing revision UKA in Center of Knee Surgery at the Instituto Nacional de Traumatologia e Ortopedia (INTO) in the period between January 1990 and January 2013.
  
  
  METHODS
  a retrospective analysis of the medical documentation and imaging, determining the cause of failure of UKA and the time of its occurrence, as well as prosthetic components implanted during the review and the need for bone grafting.
  
  
  RESULTS
  in this study, 27 UKA failures in 26 patients were included. Collapse of one or more components was the main cause of failure, occurring in 33% of patients. Aseptic failure was identified in 30% of cases, progression of osteoarthrosis in 15%, infection and pain 7% each, and osteolysis and polyethylene failure in 4% each. Early failure occurred in 41% of all revisions of UKA and late failure in 59%. 23 patients have undergone revision of UK.
  
  
  CONCLUSIONS
  in 35% of revisions the use of bone grafting was needed in tibial area; in 3 cases we needed allograft from Tissue Bank. We did not use metal increase in any of the revision. In one patient we used implant constraint for instability.
authors.affiliation: Knee Surgery Center, Instituto Nacional de Traumatologia e Ortopedia (Into), Rio de Janeiro, RJ, Brazil.
authors.forename: Alan de Paula
authors.initials: Ade P
authors.lastname: Mozella
authors.affiliation: Knee Surgery Center, Instituto Nacional de Traumatologia e Ortopedia (Into), Rio de Janeiro, RJ, Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: Borges Gonçalves
authors.affiliation: Knee Surgery Center, Instituto Nacional de Traumatologia e Ortopedia (Into), Rio de Janeiro, RJ, Brazil.
authors.forename: Jansen
authors.initials: J
authors.lastname: Osterno Vasconcelos
authors.affiliation: Knee Surgery Center, Instituto Nacional de Traumatologia e Ortopedia (Into), Rio de Janeiro, RJ, Brazil.
authors.forename: Hugo Alexandre
authors.initials: HA
authors.lastname: de Araújo Barros Cobra
keywords: Arthroplasty, replacement, knee; Bone graft; Revision