title: Alignment of the tibial component of the unicompartmental knee arthroplasty, assessed in the axial view by CT scan: does it influence the outcome?
abstract: BACKGROUND
  The ideal position of the unicompartmental knee arthroplasty (UKA) in the axial plane remains undefined the medical literature. The aim of this study was to observe how tibial components are placed in the axial plane and identify whether this could influence the postoperative clinical outcome.
  
  
  METHODS
  A retrospective transversal study of 101 UKA was performed in 88 patients by a single surgeon. Postoperative CT scans were performed at a mean follow-up period of 71 months (36 to 150), and clinical and functional outcomes were assessed by the WOMAC and the KSS scores. Patients were divided several times in two groups depending on a different WOMAC or KSS value each time, and differences in axial angulation were analyzed in every comparison. Distribution of data and influence on outcomes were also analyzed.
  
  
  RESULTS
  The tibial component was positioned with a mean angulation of 11.9° (-1 to 32) of external rotation (ER). A lower angle of ER was observed in all comparisons in the groups with better outcomes. Differences between groups were statistically significant when a good result was defined as a WOMAC score lower than 10.
  
  
  CONCLUSIONS
  Variability in axial positioning (33°) is higher than in other planes due to the free-hand technique. A trend towards better outcomes is observed when the tibial component is placed in a lower angle of ER. Rotational alignment in UKA should be investigated in subsequent studies with larger sample sizes.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Department of Orthopaedic Surgery, Centre Hospitalier de Saint Palais, Saint Palais, Pays Basque, France. Electronic address: ikeririberri@hotmail.com.
authors.forename: Iker
authors.initials: I
authors.lastname: Iriberri
authors.affiliation: Department of Orthopaedic Surgery, Fundació Hospital de l'Esperit Sant, Santa Coloma de Gramenet, Barcelona, Spain.
authors.forename: José Francisco
authors.initials: JF
authors.lastname: Aragón
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D010149:Postoperative Pain / Q000175:diagnosis; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods; D014102:Torsion Abnormality / Q000150:complications; D016896:Treatment Outcome
keywords: Axial alignment; CT scan; Clinical outcomes; Tibial component; Unicompartmental knee arthroplasty