title: The contribution of intraoperative medial compartment stability to post-operative knee flexion angle in unicompartmental knee arthroplasty.
abstract: OBJECTIVE
  Given the knee kinematics and soft tissue balance in unicompartmental knee arthroplasty (UKA), it was hypothesised that intraoperative medial compartment stability will result in good functional outcome. The purpose of this study was to test the influence of soft tissue balance on post-operative knee flexion in UKA.
  
  
  METHODS
  The influence of soft tissue balance on post-operative knee flexion in UKA was first examined retrospectively by using a newly developed tensor device in 30 consecutive patients diagnosed with either isolated medial compartmental osteoarthritis or idiopathic necrosis. The intraoperative component gap of the medial compartment was measured by using the tensor while applying a 20-lb joint distraction force at 0°, 10°, 30°, 45°, 60°, 90°, 120°, and 135° of knee flexion, with calculation of the joint looseness. Correlations between the soft tissue parameters and post-operative knee flexion angles were analysed 1 year after surgery.
  
  
  RESULTS
  The post-operative knee flexion angle was negatively correlated with the component gap at 45°, 60°, and 90° of flexion (R = -0.41, P < 0.05; R = -0.44, P < 0.05; and R = -0.44, P < 0.05, respectively). Furthermore, the post-operative knee flexion angle was negatively correlated with joint looseness at 45°, 60°, and 90° of flexion (R = -0.40, P < 0.05; R = -0.41, P < 0.05; and R = -0.36, P < 0.05, respectively).
  
  
  CONCLUSIONS
  The intraoperative medial compartment stability of knee flexion in midrange resulted in increasing post-operative knee flexion angle in UKA. Medial soft tissue release should be minimised, and assessment of soft tissue balance using a tensor can be performed to predict the post-operative knee flexion angle during surgery for UKA.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Tokio
authors.initials: T
authors.lastname: Matsuzaki
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan. matsun@m4.dion.ne.jp.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedic Surgery, Steel Memorial Hirohata Hospital, Himeji, Hyogo, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Muratsu
authors.affiliation: Department of Orthopaedic Surgery, Kobe Kaisei Hospital, Kobe, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Ishida
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Takayama
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Kanto
authors.initials: K
authors.lastname: Nagai
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Nakano
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Kyohei
authors.initials: K
authors.lastname: Nishida
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, 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 / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011184:Postoperative Period; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Component gap; Knee flexion angle; Offset-type tensor; Soft tissue balance; Unicompartmental knee arthroplasty