title: The influence of patella height on soft tissue balance in cruciate-retaining and posterior-stabilised total knee arthroplasty.
abstract: OBJECTIVE
  Although the patella reduced or everted position has recently been recognised as an important factor influencing soft tissue balance during assessment in total knee arthroplasty (TKA), the influence of patella height on soft tissue balance has not been well addressed. Therefore, the relationship between soft tissue balance and patella height was investigated and differences between cruciate-retaining (CR) and posterior-stabilised (PS) TKA were compared.
  
  
  METHODS
  Forty consecutive patients blinded to the type of implant received, were randomised prospectively. Using lateral radiographs, pre-operative patella height was measured. Using an offset-type tensor designed to measure the soft tissue balance with a reduced patellofemoral (PF) joint and femoral component in place, soft tissue balance was intra-operatively assessed in CR TKA (n = 20) and PS TKA (n = 20) in osteoarthritic patients. The joint component gap and varus ligament balance at zero, ten, 45, 90 and 135° of knee flexion with the patella reduced were measured.
  
  
  RESULTS
  In PS TKA, the joint component gap positively correlated with patella height at 90 and 135° of knee flexion. However, there was no correlation between joint component gap and patella height at other flexion angles in PS TKA and any flexion angle in CR TKA. Varus ligament balance showed no significant correlation with patella height in either CR or PS TKA.
  
  
  CONCLUSIONS
  Analysis of soft tissue balance and patella height only showed a positive correlation in joint component gap at a high flexion angle (90 and 135°) in PS TKA but not in other parameters examined. Pre-operative measurement of patella height may be an important factor for predicting an intra-operative flexion gap in PS TKA.
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: Yuichiro
authors.initials: Y
authors.lastname: Nishizawa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Seiji
authors.initials: S
authors.lastname: Kubo
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Muratsu
authors.forename: Takehiko
authors.initials: T
authors.lastname: Matsushita
authors.forename: Shinya
authors.initials: S
authors.lastname: Oka
authors.forename: Kazunari
authors.initials: K
authors.lastname: Ishida
authors.forename: Tokio
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishida
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Akisue
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D010329:Patella / Q000601:surgery*; D016037:Single-Blind Method