title: Early functional outcome after lateral UKA is sensitive to postoperative lower limb alignment.
abstract: OBJECTIVE
  The predictive role of patient-specific characteristics and radiographic parameters on medial unicompartmental knee arthroplasty (UKA) outcomes is well known, but knowledge of these predictors is lacking in lateral UKA. Therefore, purpose of this study was to assess the predictive role of these parameters on short-term functional outcomes of lateral UKA.
  
  
  METHODS
  In this retrospective cohort study, Western Ontario and McMaster Universities Arthritis Index scores were collected at 2-year follow-up (median 2.2 years, range 2.0-4.0 years) in 39 patients who underwent lateral UKA. Patient-specific characteristics included age, BMI and gender, while radiographic parameters included osteoarthritis severity of all three compartments and both preoperative and postoperative hip-knee-ankle alignment.
  
  
  RESULTS
  BMI, gender, age and preoperative valgus alignment were not correlated with functional outcomes, while postoperative valgus alignment was correlated with functional outcomes (0.561; p = 0.001). Postoperative valgus of 3°-7° was correlated with better outcomes than more neutral (-2° to 3° valgus) alignment (96.7 vs. 85.6; p = 0.011). Postoperative alignment was a predictor when corrected for patient-specific characteristics (regression coefficient 4.1; p < 0.001) and radiological parameters (regression coefficient 3.8; p = 0.002).
  
  
  CONCLUSIONS
  Postoperative valgus alignment of 3°-7° was correlated with the best short-term functional outcomes in lateral UKA surgery, while patient-specific parameters and preoperative alignment were not correlated with functional outcomes. Based on these findings, a surgeon should aim for valgus alignment of 3°-7° when performing lateral UKA surgery for optimal functional outcomes.
  
  
  METHODS
  Prognostic study, Level II.
authors.affiliation: Computer Assisted Surgery Center, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA. jpjvanderlistmd@gmail.com.
authors.forename: J P
authors.initials: JP
authors.lastname: van der List
authors.affiliation: Computer Assisted Surgery Center, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: H
authors.initials: H
authors.lastname: Chawla
authors.affiliation: Computer Assisted Surgery Center, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Villa
authors.affiliation: Department of Orthopaedic Surgery, Spaarne Hospital, Hoofddorp, The Netherlands.
authors.forename: H A
authors.initials: HA
authors.lastname: Zuiderbaan
authors.affiliation: Computer Assisted Surgery Center, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 E. 70th Street, New York, NY, 10021, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Pearle
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D056304:Genu Valgum / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Alignment; Lateral UKA; Patient-reported functional outcomes; Predictors; Unicompartmental knee arthroplasty