title: Stress distribution of the patellofemoral joint in the anatomic V-shape and curved dome-shape femoral component: a comparison of resurfaced and unresurfaced patellae.
abstract: OBJECTIVE
  Whether to resurface the patella in knee replacement remains a controversial issue. The geometrical design of the trochlear groove in the femoral component could play an important role in determining the stress distribution on the patellofemoral joint, but this has not been sufficiently reported on. This study attempted to determine the effect of implant design on contact mechanics by means of a finite element method.
  
  
  METHODS
  Two designs, an anatomical V-shape design (VSD) and a dome-shape design (DSD), for the anterior trochlear surface in a contemporary femoral component were chosen for examining the contact characteristics. The use and absence of patella resurfacing was simulated. The stress and strain distribution on the patellar bone and the polyethylene component were calculated for comparison.
  
  
  RESULTS
  Without patellar resurfacing, the maximal compressive strain in the patellar bone in the VSD model was about 20 % lower than the DSD model. On the other hand, with resurfacing, the maximal strain for the VSD model was 13.3 % greater than for DSD. Uneven stress distribution at the bone-implant interface was also noted for the two designs.
  
  
  CONCLUSIONS
  The femoral component with a V-shape trochlear groove reduced the compressive strain on the unresurfaced patella. If resurfacing the patella, the femoral component with a curved domed-shape design might reduce the strain in the remaining patellar bone. Uneven stress could occur at the bone-implant interface, so design modifications for improving fixation strength and medialization of the patellar button would be helpful in reducing the risk of peg fracture or loosening.
  
  
  METHODS
  III.
authors.affiliation: Biomechanics Research Laboratory, Mackay Memorial Hospital, No. 45, Mingsheng Rd, Tamshui District, New Taipei City, 25160, Taiwan.|Department of Physical Therapy and Assistive Technology, National Yang-Ming University, No. 155, Sec. 2, Li-Nung St., Taipei, 112, Taiwan.|Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Huang
authors.affiliation: Biomechanics Research Laboratory, Mackay Memorial Hospital, No. 45, Mingsheng Rd, Tamshui District, New Taipei City, 25160, Taiwan.
authors.forename: Lin-I
authors.initials: LI
authors.lastname: Hsu
authors.affiliation: Biomechanics Research Laboratory, Mackay Memorial Hospital, No. 45, Mingsheng Rd, Tamshui District, New Taipei City, 25160, Taiwan.|Department of Orthopaedic Surgery, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Ting-Kuo
authors.initials: TK
authors.lastname: Chang
authors.affiliation: Department of Orthopedic Surgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan.
authors.forename: Tai-Yuan
authors.initials: TY
authors.lastname: Chuang
authors.affiliation: Department of Physical Therapy and Assistive Technology, National Yang-Ming University, No. 155, Sec. 2, Li-Nung St., Taipei, 112, Taiwan.|Department of Orthopaedic Surgery, Zhong-Xing Branch of Taipei-City Hospital, Taipei, Taiwan.
authors.forename: Shih-Liang
authors.initials: SL
authors.lastname: Shih
authors.affiliation: Biomechanics Research Laboratory, Mackay Memorial Hospital, No. 45, Mingsheng Rd, Tamshui District, New Taipei City, 25160, Taiwan. yungchanglu@hotmail.com.|Department of Orthopaedic Surgery, Mackay Memorial Hospital, Taipei, Taiwan. yungchanglu@hotmail.com.|Mackay Junior College of Medicine, Nursing, and Management, Taipei, Taiwan. yungchanglu@hotmail.com.
authors.forename: Yung-Chang
authors.initials: YC
authors.lastname: Lu
authors.affiliation: Department of Physical Therapy and Assistive Technology, National Yang-Ming University, No. 155, Sec. 2, Li-Nung St., Taipei, 112, Taiwan. cschen@ym.edu.tw.
authors.forename: Chen-Sheng
authors.initials: CS
authors.lastname: Chen
authors.affiliation: Biomechanics Research Laboratory, Mackay Memorial Hospital, No. 45, Mingsheng Rd, Tamshui District, New Taipei City, 25160, Taiwan.|Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan.|Department of Orthopaedic Surgery, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Chun-Hsiung
authors.initials: CH
authors.lastname: Huang
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D020342:Finite Element Analysis; D006801:Humans; D007720:Knee Prosthesis; D008953:Models, Anatomic; D010329:Patella / Q000601:surgery*; D057071:Patellofemoral Joint / Q000503:physiopathology / Q000601:surgery*; D020959:Polyethylene; D011474:Prosthesis Design; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
chemical_list: D020959:Polyethylene
keywords: Contact characteristics; Knee replacement; Patellar resurfacing; Patellofemoral joint