title: The comprehensive cohort model in a pilot trial in orthopaedic trauma.
abstract: BACKGROUND
  The primary aim of this study was to provide an estimate of effect size for the functional outcome of operative versus non-operative treatment for patients with an acute rupture of the Achilles tendon using accelerated rehabilitation for both groups of patients. The secondary aim was to assess the use of a comprehensive cohort research design (i.e. a parallel patient-preference group alongside a randomised group) in improving the accuracy of this estimate within an orthopaedic trauma setting.
  
  
  METHODS
  Pragmatic randomised controlled trial and comprehensive cohort study within a level 1 trauma centre. Twenty randomised participants (10 operative and 10 non-operative) and 29 preference participants (3 operative and 26 non-operative). The ge range was 22-72 years and 37 of the 52 patients were men. All participants had an acute rupture of their Achilles tendon and no other injuries. All of the patients in the operative group had a simple end-to-end repair of the tendon with no augmentation. Both groups then followed the same eight-week immediate weight-bearing rehabilitation programme using an off-the-shelf orthotic. The disability rating index (DRI; primary outcome), EQ-5D, Achilles Total Rupture Score and complications were assessed ed at two weeks, six weeks, three months, six months and nine months after initial injury.
  
  
  RESULTS
  At nine months, there was no significant difference in DRI between patients randomised to operative or non-operative management. There was no difference in DRI between the randomised group and the parallel patient preference group. The use of a comprehensive cohort of patients did not provide useful additional information as to the treatment effect size because the majority of patients chose non-operative management.
  
  
  CONCLUSIONS
  Recruitment to clinical trials that compare operative and non-operative interventions is notoriously difficult; especially within the trauma setting. Including a parallel patient preference group to create a comprehensive cohort of patients has been suggested as a way of increasing the power of such trials. In our study, the comprehensive cohort model doubled the number of patients involved in the study. However, a strong preference for non-operative treatment meant that the increased number of patients did not significantly increase the ability of the trial to detect a difference between the two interventions.
  
  
  BACKGROUND
  ISRCTN: ISRCTN29053307.
authors.affiliation: Warwick Orthopaedics, Clinical Sciences Building, University of Warwick, Coventry, CV2 2DX, UK.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Kearney
authors.forename: Juul
authors.initials: J
authors.lastname: Achten
authors.forename: Nick R
authors.initials: NR
authors.lastname: Parsons
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Costa
mesh_terms: D000125:Achilles Tendon / Q000293:injuries* / Q000502:physiology / Q000601:surgery*; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D009989:Orthotic Devices; D010865:Pilot Projects; D016896:Treatment Outcome; D016474:Weight-Bearing