title: Clinical outcome of increased flexion gap after total knee arthroplasty. Can controlled gap imbalance improve knee flexion?
abstract: OBJECTIVE
  Increased range of motion (ROM) while maintaining joint stability is the goal of modern total knee arthroplasty (TKA). A biomechanical study has shown that small increases in flexion gap result in decreased tibiofemoral force beyond 90° flexion. The purpose of this paper was to investigate clinical implications of controlled increased flexion gap.
  
  
  METHODS
  Four hundred and four TKAs were allocated into one of two groups and analysed retrospectively. In the first group (n = 352), flexion gap exceeded extension gap by 2.5 mm, while in the second group (n = 52) flexion gap was equal to the extension gap. The procedures were performed from 2008 to 2012. The patients were reviewed 12 months postoperatively. Objective clinical results were assessed for ROM, mediolateral and sagittal stability. Patient-reported outcome measures were the WOMAC score and the Forgotten Joint Score (FJS-12).
  
  
  RESULTS
  After categorizing postoperative flexion into three groups (poor < 90°, satisfactory 91°-119°, good ≥ 120°) significantly more patients in group 1 achieved satisfactory or good ROM (p = 0.006). Group 1 also showed a significantly higher mean FJS-12 (group 1: 73, group 2: 61, p = 0.02). The mean WOMAC score was 11 in the first and 14 in the second group (n.s.). Increase in flexion gap did not influence knee stability.
  
  
  CONCLUSIONS
  The clinical relevance of this study is that a controlled flexion gap increase of 2.5 mm may have a positive effect on postoperative flexion and patient satisfaction after TKA. Neither knee stability in the coronal and sagittal planes nor complications were influenced by a controlled increase in flexion gap.
  
  
  METHODS
  III.
authors: Department of Orthopedic Surgery, University Hospital of Basel, Spitalstrasse 21, 4056, Basel, Switzerland.
authors: P
authors: P
authors: Ismailidis
authors: The University of Western Australia, 31 Outram Street, West Perth, WA, 6005, Australia.|Nedlands and PerthOrthopaedic and Sports Medicine Centre, 31 Outram Street, West Perth, WA, 6005, Australia.
authors: M S
authors: MS
authors: Kuster
authors: Department of Orthopaedic Surgery, Kantonsspital St. Gallen, Rorschacherstrasse 95, 9007, St. Gallen, Switzerland.
authors: B
authors: B
authors: Jost
authors: Department of Orthopaedic Surgery, Kantonsspital St. Gallen, Rorschacherstrasse 95, 9007, St. Gallen, Switzerland.
authors: K
authors: K
authors: Giesinger
authors: Department of Orthopaedic Surgery, Kantonsspital St. Gallen, Rorschacherstrasse 95, 9007, St. Gallen, Switzerland. henrik.behrend@kssg.ch.
authors: H
authors: H
authors: Behrend
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular; D016896:Treatment Outcome
keywords: Controlled gap imbalance; Patient-reported outcome; TKA; TKR; Total knee replacement