title: 2-year follow-up report on micromotion of a short tibia stem. A prospective, randomized RSA study of 59 patients.
abstract: OBJECTIVE
  A shortened tibial stem could influence the early prosthetic fixation. We therefore compared the short stem to the standard-length stem using radiostereometric analysis (RSA) as primary outcome measure.
  
  
  METHODS
  60 patients were randomized to receive a cemented Triathlon total knee arthroplasty (TKA) with a tibial tray of either standard or short stem length. The patients were blinded regarding treatment allocation. The micromotion of the tibial component was measured by RSA postoperatively, at 3 months, and after 1 and 2 years; clinical outcome was measured with the American Knee Society score (AKSS) and the knee osteoarthritis and injury outcome score (KOOS).
  
  
  RESULTS
  The maximum total point motion (MTPM) for the standard stem was 0.36 (SD 0.16) mm at 3 months, 0.51 (SD 0.27) mm at 1 year, and 0.54 (SD 0.28) mm at 2 years. For the short stem, it was 0.42 (0.24) mm, 0.59 (0.43) mm, and 0.61 (0.39) mm. 4 short-stemmed components and 2 standard-stemmed components had more than 0.2 mm of migration between the first- and second-year follow-up, and were classified as continuously migrating.
  
  
  CONCLUSIONS
  The short-stemmed cemented tibial prosthesis showed an early prosthetic migratory pattern similar to that of the standard-stemmed cemented Triathlon knee prosthesis. The number of continuously migrating tibial plates in each group is predictive of a lower revision rate than 5% at 10 years.
authors: a Department of Orthopedics , Hässleholm Hospital, Hässleholm and Department of Clinical Sciences, Lund University, Sweden.
authors: Mats
authors: M
authors: Molt
authors: a Department of Orthopedics , Hässleholm Hospital, Hässleholm and Department of Clinical Sciences, Lund University, Sweden.
authors: Sören
authors: S
authors: Toksvig-Larsen
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D059869:Radiostereometric Analysis / Q000379:methods; D012720:Severity of Illness Index; D013977:Tibia; D016896:Treatment Outcome