title: Surgeon's experience influences UKA survivorship: a comparative study between all-poly and metal back designs.
abstract: OBJECTIVE
  Concerns exist regarding prosthetic positioning and post-operative limb alignment in unicompartmental knee arthroplasty (UKA). In this study, we hypothesized deviations of the post-op anatomical femoro-tibial angle (aFTA) and the tibial component alignment to be factors influencing UKA survivorship. Moreover, by a comparison between all-poly and metal back UKAs, we hypothesized that prosthetic design plays a role in implant survivorship.
  
  
  METHODS
  One hundred ninety-five medial UKAs were performed on 176 patients by two experienced surgeons and one low-UKA user. One hundred and forty-seven UKAs were included in the study: 72 all-poly and 75 metal back. Measurements were performed on radiographs: mechanical femoro-tibial angle, Cartier angle, aFTA and tibial posterior slope (PS) on pre-op radiographs; femoral and tibial component varus/valgus, aFTA and tibial component PS on post-op radiographs.
  
  
  RESULTS
  At an average follow-up of 61 months (min. 30, max. 107), 147 UKAs were evaluated: The reported survivorship rate was 93.1 %. Eleven implants underwent revision: ten all-poly and one metal back. No differences were reported between the two groups in the radiographic measurements. Significant radiographic differences were reported between revised and not revised UKAs: Revised UKAs were associated with overcorrection of the pre-op Cartier angle and under correction of pre-op aFTA. Most of revised UKAs were performed by the low-volume UKA surgeon.
  
  
  CONCLUSIONS
  Surgeon's experience is essential to achieve good results in UKA: Preserving the tibial epiphyseal axis and avoiding excessive or insufficient corrections of the pre-operative limb alignment are predictor of successful replacement, while prosthetic designs, models and fixation geometry do not affect UKA outcome.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Azienda Ospedaliero-Universitaria Policlinico di Modena, University of Modena and Reggio-Emilia, Via del Pozzo 71, 41124, Modena, Italy, francesco.zambianchi@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Zambianchi
authors.forename: V
authors.initials: V
authors.lastname: Digennaro
authors.forename: A
authors.initials: A
authors.lastname: Giorgini
authors.forename: G
authors.initials: G
authors.lastname: Grandi
authors.forename: F
authors.initials: F
authors.lastname: Fiacchi
authors.forename: R
authors.initials: R
authors.lastname: Mugnai
authors.forename: F
authors.initials: F
authors.lastname: Catani
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D002983:Clinical Competence; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008670:Metals; D011095:Polyethylenes; D011474:Prosthesis Design; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery
chemical_list: D008670:Metals; D011095:Polyethylenes