title: Validation of statistical shape modelling to predict hip osteoarthritis in females: data from two prospective cohort studies (Cohort Hip and Cohort Knee and Chingford).
abstract: OBJECTIVE
  To prospectively investigate whether hip shape variants at baseline are associated with the need for future total hip replacement (THR) in women and to validate the resulting associated shape variants of the Cohort Hip and Cohort Knee (CHECK) cohort and the Chingford cohort.
  
  
  METHODS
  Female participants from the CHECK cohort without radiographic OA (Kellgren-Lawrence score <2) at baseline were included (1100 hips); 22 hips had a THR within 5 years of follow-up. For the Chingford cohort, with only female participants, hips without radiographic OA at baseline were selected and a nested case-control design was used, with 19 THR cases within 19 years of follow-up and 95 controls matched 5 to 1 for age and BMI. Hip shape on baseline anteroposterior pelvic radiographs was assessed by statistical shape modelling (SSM) using the same model for both cohorts.
  
  
  RESULTS
  In the CHECK and Chingford cohorts, the respective mean age was 55.8 (s.d. 5.1) and 53.6 (s.d. 5.4) and the BMI was 26.14 (s.d. 4.3) and 25.7 (s.d. 3.3), respectively. Multiple shape variants of the hip were significantly (P < 0.05) associated with future THR in both the CHECK (modes 4, 11, 15, 17 and 22) and Chingford (modes 2 and 17) cohorts. Mode 17 [odds ratio (OR) 0.51 (95% CI 0.33, 0.80) in the CHECK cohort], representing a flattened head-neck junction and flat greater trochanter, could be confirmed in the Chingford cohort [OR 0.41 (95% CI 0.23, 0.82)]. Modes 4 and 15 of the CHECK cohort also showed non-significant trends in the Chingford cohort.
  
  
  CONCLUSIONS
  Several baseline shape variants are associated with the future need for THR within a cohort. Despite differences in participant characteristics, radiographic protocol and follow-up time, we could validate at least one shape variant, suggesting that SSM is reasonably transferable between cohorts.
authors.affiliation: Department of Orthopaedics, Erasmus University Medical Centre, Rotterdam, The Netherlands, Arthritis Research UK Centre for Sports, Exercise and Osteoarthritis, r.agricola@erasmusmc.nl.
authors.forename: Rintje
authors.initials: R
authors.lastname: Agricola
authors.affiliation: Arthritis Research UK Centre for Sports, Exercise and Osteoarthritis, NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Leyland
authors.affiliation: Department of Orthopaedics, Erasmus University Medical Centre, Rotterdam, The Netherlands, Department of General Practice, Erasmus University Medical Centre, Rotterdam.
authors.forename: Sita M A
authors.initials: SM
authors.lastname: Bierma-Zeinstra
authors.affiliation: NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Geraint E
authors.initials: GE
authors.lastname: Thomas
authors.affiliation: Department of Orthopaedics, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Emans
authors.affiliation: Department of Twin Research and Genetic Epidemiology, King's College, London, UK.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Spector
authors.affiliation: Department of Orthopaedics and Department of Rheumatology, University Medical Centre Utrecht, Utrecht and Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Harrie
authors.initials: H
authors.lastname: Weinans
authors.affiliation: Department of Orthopaedics, Erasmus University Medical Centre, Rotterdam, The Netherlands.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Waarsing
authors.affiliation: Arthritis Research UK Centre for Sports, Exercise and Osteoarthritis, NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Nigel K
authors.initials: NK
authors.lastname: Arden
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D008875:Middle Aged; D015233:Models, Statistical; D009426:Netherlands; D015207:Osteoarthritis, Hip / Q000175:diagnosis* / Q000000981:diagnostic imaging* / Q000473:pathology; D017063:Outcome Assessment, Health Care; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011859:Radiography; D012984:Software; D006113:United Kingdom
keywords: active shape modelling; epidemiology; hip shape; morphology; osteoarthritis; radiography; statistical shape modelling; total hip replacement; validation