title: Incidence, indications, outcomes, and survivorship of stems in primary total knee arthroplasty.
abstract: OBJECTIVE
  The indications, incidence, outcomes, and survivorship of stems in primary total knee arthroplasty (TKA) are lacking in the contemporary literature. Our hypothesis is stems in primary TKA would result in worse outcomes and survivorship.
  
  
  METHODS
  All primary TKAs between 2007 and 2011 with 2-year follow-up were identified. Revision TKA or UKA conversion was excluded. Demographic information (age, sex, race, BMI, primary diagnosis, and Charlson-Deyo comorbidity index), outcome measures including KOOS and WOMAC, and any revisions were identified from the registry. A 2:1 matched cohort of non-stemmed/stemmed primary TKA patients was created to compare revision rates and outcomes at baseline and 2 years post-TKA. Subgroup analyses of long versus short stems, 1 versus 2 stems, and cemented versus hybrid stem fixation were completed. Two-sample t tests and Chi-square tests were used to compare conventional and stemmed TKA groups.
  
  
  RESULTS
  The registry review included 13,507 conventional TKA and 318 stemmed TKA resulting in an incidence of 2.3 % in primary TKA. The mean follow-up was approximately 49 months in both groups. No difference was found in revision rates between stemmed TKA (2.5 %) and conventional TKA (2.2 %). Patients with post-traumatic arthritis had an odds ratio of 10.5 (95 % CI 1.2-15.3) of receiving stems. Stem length did not affect revision rates. Patients with two stems had worse KOOS and WOMAC scores at baseline which equalized to single-stem patients at 2 years.
  
  
  CONCLUSIONS
  The use of stems may provide a survival benefit in complex primary TKA over the short term and no adverse effect on patient outcomes or satisfaction.
  
  
  METHODS
  III.
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Barlow
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA. oik@hss.edu.
authors.forename: Kathryn K
authors.initials: KK
authors.lastname: Oi
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Yuo-Yu
authors.initials: YY
authors.lastname: Lee
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Amethia D
authors.initials: AD
authors.lastname: Joseph
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Alexiades
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007595:Joint Prosthesis; D007719:Knee Joint / Q000601:surgery; D008297:Male; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000601:surgery*; D017060:Patient Satisfaction; D011474:Prosthesis Design; D012042:Registries; D012086:Reoperation; D016896:Treatment Outcome
keywords: KOOS; Outcomes; Primary total knee arthroplasty; Stems incidence; Stems indications; Survivorship; WOMAC