title: Effects of patellofemoral overstuffing on knee flexion and patellar kinematics following total knee arthroplasty: a cadaveric study.
abstract: OBJECTIVE
  The purpose of this study was to test the hypothesis that overstuffing the patellofemoral joint during total knee arthroplasty (TKA) would decrease passive knee flexion and alter patellar kinematics during knee flexion.
  
  
  METHODS
  Ten cadaveric knees were implanted with cruciate-retaining TKAs, and the patellofemoral joint was overstuffed in 2-mm increments with custom-augmented patellar prostheses (+2 mm through +8 mm). Changes to knee flexion, patellar shift, tilt and rotation were measured with an imageless optical-tracking computer navigation system.
  
  
  RESULTS
  Knee flexion decreased an average 1.2° with each additional 2 mm of patellar thickness. Compared with control TKA (+0 mm), no significant decrease in knee flexion was detected until the patellofemoral joint was overstuffed with the +8-mm patellar prosthesis. Kinematic tracking data showed significantly greater lateral shift of patella with the +6- and +8-mm prostheses and significantly greater lateral tilt with the +8-mm prosthesis. Overstuffing had no appreciable effect on patellar rotation.
  
  
  CONCLUSIONS
  Passive knee flexion after TKA is significantly reduced when overstuffing the patellofemoral joint by +8 mm, and patellofemoral kinematics are altered when overstuffing the joint by +6 mm. These results demonstrate the relatively modest effects of patellofemoral overstuffing on knee flexion and patellar tracking kinematics after TKA.
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Bracey
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Brown
authors.forename: Hoyt R
authors.initials: HR
authors.lastname: Beard
authors.forename: Sandeep
authors.initials: S
authors.lastname: Mannava
authors.forename: Omar F
authors.initials: OF
authors.lastname: Nazir
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Seyler
authors.forename: Jason E
authors.initials: JE
authors.lastname: Lang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000503:physiopathology / Q000601:surgery; D057071:Patellofemoral Joint / Q000503:physiopathology* / Q000601:surgery; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted