title: The Evolution of Implant Design Decreases the Incidence of Lateral Release in Primary Total Knee Arthroplasty.
abstract: Appropriate balancing of the patellofemoral joint (PFJ) using a lateral release can help to prevent patellar instability in total knee arthroplasty (TKA). Contemporary total knee implant designs are characterized by enhanced trochlear geometry more similar to native knee anatomy to minimize instability and reduce utilization of a lateral release.
  
  
  
  We retrospectively reviewed consecutive TKA cases from a single senior surgeon's practice with 3 successive total knee designs: the Press-Fit Condylar (PFC), the Sigma, and the ATTUNE (DePuy, Warsaw, IN). We evaluated the use of lateral release with each implant type to determine if design changes have improved patellar stability, reducing the need for lateral release. We used multivariate analysis to determine the association between implant type and lateral release, adjusting for age, sex, preoperative alignment, and bearing type.
  
  
  
  We evaluated 1991 records of primary TKAs performed from 1980-2015. As compared with the ATTUNE, the adjusted odds of lateral release were greater for patients receiving PFC implants (Odds ratio [OR] 6.35, 95% confidence interval [CI] 3.85,10.49) and Sigma implants (OR 2.02, 95% CI 1.26, 3.23). In addition, fixed bearing implants were associated with greater adjusted odds of lateral release (OR 1.80, 95% CI 1.24, 2.62).
  
  
  
  We found that older knee implants were associated with higher use of lateral release, with successive designs the need for lateral release to balance the PFJ decreased. Continued design improvements to match the native knee anatomy may further improve the stability of the PFJ in future designs.
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Webb
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Heidi Y
authors.initials: HY
authors.lastname: Yang
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Jamie E
authors.initials: JE
authors.lastname: Collins
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts; Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital Harvard Medical School, Boston, Massachusetts; Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Elena
authors.initials: E
authors.lastname: Losina
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Thornhill
authors.affiliation: Department of Orthopedic Surgery, Orthopaedic and Arthritis Center for Outcomes Research, Brigham and Women's Hospital, Boston, Massachusetts; Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital Harvard Medical School, Boston, Massachusetts.
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Katz
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D015994:Incidence; D007593:Joint Instability / Q000601:surgery; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D010329:Patella / Q000601:surgery*; D057071:Patellofemoral Joint / Q000601:surgery; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
keywords: fixed bearing implants; implant design; lateral release; outcomes; patella; total knee arthroplasty