title: Fixed Flexion Deformity After Unicompartmental Knee Arthroplasty: How Much Is Too Much.
abstract: The detrimental impact of postoperative fixed flexion deformity (FFD) after unicompartmental knee arthroplasty (UKA) is manifold. This study aims to define the amount of postoperative FFD that is clinically relevant after UKA.
  
  
  
  Between 2005 and 2012, 803 patients who underwent a primary UKA at a tertiary hospital were prospectively followed up. They were categorized into 3 groups based on the amount of postoperative FFD: (1) 0° (control); (2) 1°-10° (mild FFD); and (3) >10° (severe FFD).
  
  
  
  There were 26 patients (3%) with severe FFD at 2 years after UKA. The Knee Society Function Score and Knee Score in the severe FFD group were 10 ± 4 and 10 ± 2 points lower than in the control group, respectively (P = .017 and P = .001). Similarly, the Oxford Knee Score and Physical Component Score in the severe FFD group was 5 ± 1 and 7 ± 2 points lower than in the control group, respectively (P = .033 and P < .001).
  
  
  
  This study suggests that postoperative FFD of >10° after UKA is associated with significantly poorer functional outcomes.
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Jerry Yongqiang
authors.initials: JY
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Bryan
authors.initials: B
authors.lastname: Loh
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Yew Lok
authors.initials: YL
authors.lastname: Woo
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Shi-Lu
authors.initials: SL
authors.lastname: Chia
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Ngai Nung
authors.initials: NN
authors.lastname: Lo
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, Singapore.
authors.forename: Seng Jin
authors.initials: SJ
authors.lastname: Yeo
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007717:Knee / Q000503:physiopathology* / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000523:psychology / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies; D011788:Quality of Life; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D062606:Tertiary Care Centers; D016896:Treatment Outcome
keywords: fixed flexion deformity; functional outcome; minimally clinically important difference; quality of life; unicompartmental knee arthroplasty