title: Patellar morphology and femoral component geometry influence patellofemoral contact stress in total knee arthroplasty without patellar resurfacing.
abstract: OBJECTIVE
  The objective of this study was to determine the effect of patellar morphology and implant design on patellofemoral contact stress in total knee arthroplasty (TKA) without patellar resurfacing.
  
  
  METHODS
  Radiographic investigation: One hundred and fifty-seven knees of 127 patients were included in the study. Implants used in the present series were Low Contact Stress (LCS), Genesis II and NexGen. The relationship between the pre-operative patellar facet angle and newly identified post-operative osteosclerosis was assessed. Finite element analysis: Using patient-specific patellar three-dimensional finite element models, the relationship between the patellar facet angle and mean von Mises stress within the patella was calculated at flexion angles of 15°, 45°, 75° and 105°.
  
  
  RESULTS
  Radiographic investigation: Post-operative osteosclerosis was observed with decreasing patellar facet angle in the Genesis II (odds ratio = 0.72; 95% confidence interval, 0.55-0.93; P = 0.012) and NexGen implants (odds ratio = 0.87; 95% confidence interval, 0.77-0.99; P = 0.029). Patients treated with the Genesis II had significantly more advanced osteosclerosis than those treated with the other two implants. Finite element analysis: A negative correlation was found between the patellar facet angle and the mean von Mises stress for all three implants. The Genesis II showed significantly higher von Mises stress than the other two implants at flexion angles of 15°, 45° and 105°.
  
  
  CONCLUSIONS
  Both patellar morphology and femoral component geometry influence patellofemoral contact stress in total knee arthroplasty without patellar resurfacing.
  
  
  METHODS
  Case control study, Level III.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takahashi
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sano
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ohnuma
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kashiwaba
authors.forename: Daisuke
authors.initials: D
authors.lastname: Chiba
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kamimura
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sugita
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000503:physiopathology*; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D010329:Patella / Q000033:anatomy & histology* / Q000503:physiopathology; D011474:Prosthesis Design; D013314:Stress, Mechanical
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