Cirrhosis is a risk factor for total hip arthroplasty for avascular necrosis: A Danish nationwide cohort study

Deleuran, Thomas; Overgaard, Søren; Vilstrup, Hendrik; Jepsen, Peter

We identifi ed all Danish residents with a fi rst-time hospital discharge diagnosis of alcoholic cirrhosis (ICD-10: K70.3, K70.4) or unspecifi ed cirrhosis (ICD-10: K74.6) between 1994 and 2011. Biopsy or clinical evaluation had confi rmed 85% of diagnoses for cirrhosis in the NPR in a previous validation study (Vestberg et al. 1997) . We defi ned the "index date" as the date of the fi rst cirrhosis diagnosis. To study the association between cirrhosis and a total hip arthroplasty for AVN, we excluded cirrhosis patients if they had a previous diagnosis of avascular necrosis (ICD-10: M87.0), if they had previously undergone total hip arthroplasty, or if they were diagnosed with hip fracture (ICD-8: 820.xx, 821.xx, 822.xx, 823-xx; ICD-10: S72.0, S82.0, S82.1, S83.x) before the index date. We matched these cirrhosis patients 1:5 on the basis of age, sex, and birth date to reference individuals without cirrhosis from the general Danish population, using risk-set sampling (Langholz and Goldstein 1996) . The reference individuals were given the same index date as the corresponding cirrhosis patient. We excluded reference individuals according to the same criteria as cirrhosis patients; this exclusion resulted in a situation whereby not all cirrhosis patients were matched 1:5.