title: Roentgen stereophotogrammetric analysis: an effective tool to predict implant survival after an all-poly unicompartmental knee arthroplasty-a 10 year follow-up study.
abstract: OBJECTIVE
  The main purpose of the present study was to determine long-term implant fixation of 15 unicompartmental knee arthroplasty (UKAs) with an all-poly tibial component using Roentgen stereophotogrammetric analysis (RSA) at a mean 10-year follow-up. The secondary purpose was to investigate whether the progressive loss of implant's fixation correlates with a reduction in Knee society score (KSS).
  
  
  METHODS
  Fifteen non-consecutive patients with primary knee osteoarthritis received a UKA with an all-poly tibial component were assessed using KSS scores pre-operatively and post-operatively and RSA on day 2 after surgery, then at 3, 6, and 12 months and yearly thereafter. The mean last follow-up was 10 years.
  
  
  RESULTS
  An increase in maximum total point motion (MTPM) values from 6 months to 1 year post-operatively was found respect to post-operative reference. Implants' displacement values were always <2 mm during the first 6 months, and then, two different trends were noticed in revised and non-revised implants. MTPM increase between 1 and 2 years of follow-up in non-revised UKAs was always <0.2 mm, whereas it was >0.2 mm in revised UKAs. A linear and negative correlation with statistical significance was found between MTPM and both clinical and functional KSS scores (p < 0.001).
  
  
  CONCLUSIONS
  Also in a long-term follow-up evaluation, RSA is an effective tool to predict functional results after an all-poly UKA providing also a relevant predictive value at 1 year follow-up, and this can be very useful for both patients and surgeons.
  
  
  METHODS
  Diagnostic studies, Level III.
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. d.bruni@biomec.ior.it.
authors.forename: Danilo
authors.initials: D
authors.lastname: Bruni
authors.affiliation: Dipartimento di Scienze Biomediche e Neuromotorie (DIBINEM), Univeristà di Bologna, Bologna, Italy. l.bragonzoni@biomec.ior.it.
authors.forename: Laura
authors.initials: L
authors.lastname: Bragonzoni
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. michele.gagliardi4@studio.unibo.it.
authors.forename: Michele
authors.initials: M
authors.lastname: Gagliardi
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. m.bontempi@biomec.ior.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Bontempi
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. ibrahim.akkawi@studio.unibo.it.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Akkawi
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. giovi.ras@hotmail.it.
authors.forename: Giovanni Francesco
authors.initials: GF
authors.lastname: Raspugli
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. f.iacono@biomec.ior.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Iacono
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. s.patella@biomec.ior.it.
authors.forename: Silvio
authors.initials: S
authors.lastname: Patella
authors.affiliation: Biomechanics and Technological Innovation Laboratory, Codivilla-Putti Research Center, Rizzoli Orthopaedic Institute, Bologna University, Via Di Barbiano 1-10, 40136, Bologna, Italy. m.marcacci@biomec.ior.it.
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D016896:Treatment Outcome
keywords: All-poly tibial component unicompartmental knee arthroplasty; Implant fixation; Maximum total point motion; Roentgen stereophotogrammetric analysis