title: Does patella position influence ligament balancing in total knee arthroplasty?
abstract: OBJECTIVE
  In vivo comparative gap measurements were performed in three different patella positions (reduced, subluxated and everted) using offset-type-force-controlled-spreader-system.
  
  
  METHODS
  Prospectively, 50 knees were operated by total knee arthroplasty using a navigation-assisted gap-balancing technique. The offset-type-force-controlled-spreader-system was used for gap measurements. This commercially available instrument allows controllable tension in patella-reduced position. The mediolateral gaps of knee extension (0°) and flexion (90°) angle were recorded in three different patella positions; reduced, subluxated and everted. Any gap differences of more than 3 mm were considered as a meaningful difference. Correlation between the difference with the demographic data, preoperative radiologic alignment and intraoperative data was analysed. For statistical analysis, ANOVA and Pearson's correlation test were used.
  
  
  RESULTS
  The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Statistically significant difference was observed for the lateral gap of patella eversion compared to gap of patella reduction in knee flexion position (p < 0.05). There were notable cases of variability in knee flexion position. Significant portion of 12 (24 %) knees of patella subluxation and 33 (66 %) knees of patella evertion demonstrated either increased or decreased gaps in knee flexion position compared to the gaps of patella reduction position.
  
  
  CONCLUSIONS
  The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Therefore, the intraoperative patellar positioning has influence on the measurement of the joint gap. Keeping the patella in reduced position is important during gap balancing.
  
  
  METHODS
  I.
authors: Department of Orthopaedic Surgery, Veterans Health Service Medical Center, 6-2 Dunchon Dong, Kangdong Ku, Seoul, Republic of Korea.
authors: Jung-Ro
authors: JR
authors: Yoon
authors: Kwang-Jun
authors: KJ
authors: Oh
authors: Joon Ho
authors: JH
authors: Wang
authors: Jae-Hyuk
authors: JH
authors: Yang
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001837:Body Weights and Measures; D005260:Female; D056305:Genu Varum / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D010329:Patella / Q000601:surgery*; D017847:Patellar Ligament / Q000601:surgery; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted