title: Postoperative Knee Flexion Angle Is Affected by Lateral Laxity in Cruciate-Retaining Total Knee Arthroplasty.
abstract: BACKGROUND
  Although many studies have reported that postoperative knee flexion is influenced by preoperative conditions, the factors which affect postoperative knee flexion have not been fully elucidated. We tried to investigate the influence of intraoperative soft tissue balance on postoperative knee flexion angle after cruciate-retaining (CR) total knee arthroplasty (TKA) using a navigation and an offset-type tensor.
  
  
  METHODS
  We retrospectively analyzed 55 patients with osteoarthritis who underwent TKA using e.motion-CR (B. Braun Aesculap, Germany) whose knee flexion angle could be measured at 2 years after operation. The exclusion criteria included valgus deformity, severe bony defect, infection, and bilateral TKA. Intraoperative varus ligament balance and joint component gap were measured with the navigation (Orthopilot 4.2; B. Braun Aesculap) while applying 40-lb joint distraction force at 0° to 120° of knee flexion using an offset-type tensor. Correlations between the soft tissue parameters and postoperative knee flexion angle were analyzed using simple linear regression models.
  
  
  RESULTS
  Varus ligament balance at 90° of flexion (R = 0.56; P < .001) and lateral compartment gap at 90° of flexion (R = 0.51; P < .001) were positively correlated with postoperative knee flexion angle. In addition, as with past studies, joint component gap at 90° of flexion (R = 0.30; P < .05) and preoperative knee flexion angle (R = 0.63; P < .001) were correlated with postoperative knee flexion angle.
  
  
  CONCLUSIONS
  Lateral laxity as well as joint component gap at 90° of flexion is one of the most important factors affecting postoperative knee flexion angle in CR-TKA.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Nakano
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedic Surgery, Steel Memorial Hirohata Hospital, Himeji, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Muratsu
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Takayama
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D008022:Ligaments / Q000502:physiology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D016119:Posterior Cruciate Ligament / Q000502:physiology*; D011184:Postoperative Period; D016059:Range of Motion, Articular; D012189:Retrospective Studies
keywords: cruciate-retaining; knee flexion angle; soft-tissue balance; tensor; total knee arthroplasty; varus ligament balance