title: Patellar component design influences size selection and coverage.
abstract: BACKGROUND
  Patellofemoral (PF) complications following total knee arthroplasty continue to occur. Outcomes are influenced by implant design, size and alignment in addition to patient factors. The objective of this study was to assess the effect of implant design, specifically round versus oval dome patellar components, on size selected and bony coverage in a population of 100 patients.
  
  
  METHODS
  Intraoperative assessments of patella component size were performed using surgical guides for round and oval designs. Digital images of the resected patellae with and without guides were calibrated and analyzed to measure bony coverage. Lastly, the medial-lateral location of the median ridge was assessed in the native patella and compared to the positioning of the apex of the patellar implants.
  
  
  RESULTS
  In 82% of subjects, a larger oval implant was selected compared to a round. Modest, but statistically significant, differences were observed in selected component coverage of the resected patella: 82.7% for oval versus 80.9% for round. Further, positioning of the apex of oval patellar components reproduced the median ridge of the native patella more consistently than for round components.
  
  
  CONCLUSIONS
  These findings characterized how implant design influenced size selection and coverage in a population of patients. The ability to "upsize" with oval dome components led to increases in bony coverage and better replication of the median ridge compared to round components. Quantifying the interactions between implant design, sizing and coverage for a current implant system in a population of patients supports surgical decision-making and informs the design of future implants.
authors.affiliation: Colorado Joint Replacement, Centura Health Porter Adventist Hospital, 2535 South Downing Street, Suite 100, Denver, CO 80210, USA.
authors.forename: Charlie C
authors.initials: CC
authors.lastname: Yang
authors.affiliation: Colorado Joint Replacement, Centura Health Porter Adventist Hospital, 2535 South Downing Street, Suite 100, Denver, CO 80210, USA; Center for Orthopaedic Biomechanics, University of Denver, 2390 South York Street, Denver, CO 80208, USA.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Dennis
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, 2390 South York Street, Denver, CO 80208, USA.
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Davenport
authors.affiliation: Colorado Joint Replacement, Centura Health Porter Adventist Hospital, 2535 South Downing Street, Suite 100, Denver, CO 80210, USA; Center for Orthopaedic Biomechanics, University of Denver, 2390 South York Street, Denver, CO 80208, USA.
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Kim
authors.affiliation: Colorado Joint Replacement, Centura Health Porter Adventist Hospital, 2535 South Downing Street, Suite 100, Denver, CO 80210, USA.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Miner
authors.affiliation: Denver-Vail Orthopedics, 8101 Lowry Blvd #260, Denver, CO 80230, USA.
authors.forename: Derek R
authors.initials: DR
authors.lastname: Johnson
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, 2390 South York Street, Denver, CO 80208, USA. Electronic address: plaz@du.edu.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Laz
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000601:surgery*; D011474:Prosthesis Design
keywords: Bony coverage; Implant design; Implant size; Patellar component; Patellofemoral; Total knee replacement