title: Future projections of total hip and knee arthroplasty in the UK: results from the UK Clinical Practice Research Datalink.
abstract: OBJECTIVE
  To estimate the future rate of primary total hip (THR) or knee (TKR) replacement in the UK to 2035 allowing for changes in population demographics and obesity.
  
  
  METHODS
  Using age/gender/body mass index (BMI)-specific incidence rates from a population-based cohort study of 50,000 THR and 45,609 TKR patients from the UK Clinical Practice Research Datalink (CPRD) between 1991 and 2010, we projected future numbers of THR and TKR using two models: a static, estimated rate from 2010 applied to population growth forecasts to 2035, and a log-linear rate extrapolation over the same period. Both scenarios used population forecast data from the UK Office for National Statistics (ONS).
  
  
  RESULTS
  Assuming rates of THR and TKR for 2010, and given projected population changes in age, gender and BMI, the number of THRs and TKRs performed in the UK in 2035 is estimated to be, respectively: 95,877 and 118,666. By comparison, an exponential extrapolation of historical rates using a log-linear model produces much higher estimates of THR and TKR counts in 2035 at 439,097 and 1,219,362 respectively. Projected counts were higher for women than men. Assuming a changing (rather than fixed) future BMI distribution increases TKRs by 2035 but not THRs.
  
  
  CONCLUSIONS
  Using historical rates and population forecasts we have projected the number of THR/TKR operations in the UK up to 2035. This study will inform policymakers requiring estimates of future demand for surgery. Incorporating future forecasts for BMI into projections of joint replacement may be more relevant for TKR rather than THR.
authors.affiliation: Faculty of Medicine, University of Southampton, Tremona Road, Southampton SO16 6YD, UK; NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK.
authors.forename: D
authors.initials: D
authors.lastname: Culliford
authors.affiliation: Public Health Sciences and Medical Statistics, Faculty of Medicine, University of Southampton, Tremona Road, Southampton SO16 6YD, UK.
authors.forename: J
authors.initials: J
authors.lastname: Maskell
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, SO16 6YB, UK.
authors.forename: A
authors.initials: A
authors.lastname: Judge
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, SO16 6YB, UK.
authors.forename: C
authors.initials: C
authors.lastname: Cooper
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, SO16 6YB, UK; GREMPAL Research Group, Idiap Jordi Gol Primary Care Research Institute, Universitat Autònoma de Barcelona, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Prieto-Alhambra
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, SO16 6YB, UK. Electronic address: nigel.arden@ndorms.ox.ac.uk.
authors.forename: N K
authors.initials: NK
authors.lastname: Arden
mesh_terms: D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data / Q000639:trends*; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data / Q000639:trends*; D035843:Biomedical Research / Q000706:statistics & numerical data*; D015992:Body Mass Index; D015331:Cohort Studies; D016208:Databases, Factual / Q000706:statistics & numerical data*; D005260:Female; D005544:Forecasting; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015207:Osteoarthritis, Hip / Q000453:epidemiology* / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000601:surgery; D012189:Retrospective Studies; D012737:Sex Factors; D006113:United Kingdom / Q000453:epidemiology
keywords: Arthroplasty; Hip; Knee; Osteoarthritis; Projection