title: The influence of comorbidity scores on re-operations following primary total hip replacement: comparison and validation of three comorbidity measures.
abstract: While an increasing amount of arthroplasty articles report comorbidity measures, none have been validated for outcomes. In this study, we compared commonly used International Classification of Diseases-based comorbidity measures with re-operation rates after total hip replacement (THR). Scores used included the Charlson, the Royal College of Surgeons Charlson, and the Elixhauser comorbidity score. We identified a nationwide cohort of 134 423 THRs from the Swedish Hip Arthroplasty Register. Re-operations were registered post-operatively for up to 12 years. The hazard ratio was estimated by Cox's proportional hazards regression, and we used C-statistics to assess each measure's ability to predict re-operation. Confounding variables were age, gender, type of implant fixation, hospital category, hospital implant volume and year of surgery. In the first two years only the Elixhauser score showed any significant relationship with increased risk of re-operation, with increased scores for both one to two and three or more comorbidities. However, the predictive C-statistic in this period for the Elixhauser score was poor (0.52). None of the measures proved to be of any value between two and 12 years. They might be of value in large cohort or registry studies, but not for the individual patient.
authors.affiliation: Danderyd Hospital, Division of Orthopaedics, Department of Clinical Sciences, Karolinska Institute, Danderyds Sjukhus, SE-182 88 Stockholm, Sweden. max@gforge.se
authors.forename: M
authors.initials: M
authors.lastname: Gordon
authors.forename: A
authors.initials: A
authors.lastname: Stark
authors.forename: O G
authors.initials: OG
authors.lastname: Sköldenberg
authors.forename: J
authors.initials: J
authors.lastname: Kärrholm
authors.forename: G
authors.initials: G
authors.lastname: Garellick
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data*; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000453:epidemiology / Q000601:surgery*; D011446:Prospective Studies; D012042:Registries; D012086:Reoperation / Q000706:statistics & numerical data; D017678:Sex Distribution; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors
keywords: Charlson index; Comorbidity; Elixhausers index; RCS Charlson index; Total hip arthroplasty