IMPACT OF AGE AND COMORBIDITY ON THE MORTALITY WITHIN 90 DAYS FOLLOWING THE PRIMARY TOTAL HIP REPLACEMENT: A NATIONWIDE DANISH FOLLOW-UP STUDY

Abstract

Aim: We determined 90 days mortality following primary total hip replacement (THR) and examined the impact of age and level of comorbidity.

Methods: We used data from the nationwide population based Danish Hip Arthroplasty Registry between 1 January 1995 and 31 December 2004. Each THR patient was matched according to gender and age on the time of surgery with 3 persons from the general population randomly sampled using the Danish Civil Registration system, resulting in a total of 44 818 THA patients and 120 883 controls. We used a Cox regression analyses to computed age and comorbidity specific mortality rates (MR) and mortality rate ratio (MRR) with 95% Confidence Intervals (CI) for THR patients compared with the general population, as well as Number Needed to Harm (NNH).

Results: The MRs for THR patients relative to those for the general population were highest in the patients younger than 60 years, corresponding to an adjusted MRR of 3.6 (95% CI: 2.2–5.5). Similar, an adjusted MRR was 1.2 (95% CI: 1.0–1.4) in patients aged 80 years and over. The THR patients younger than 60 years had more comorbidity than the controls, whereas distribution of comorbidity was equal in all other age groups. MRRs increase with comorbidity level for both THR patients and controls in all age groups. MRR for THR patients vs. controls within high comorbidity level aged below 60 years and aged 80 years and over was 3.5 (1.3–9.8) and 0.7 (0.5–0.9), respectively. However, hospitalisation with particularly cardio–og cerebrovasculaar disease before surgery increase mortality risk for both age groups, whereas hospitalisation with cancer increase mortality risk for patients younger than 60 years and decrease it for patients aged 80 years and over.

Conclusions: Overall mortality of THR patients relative to those in the general population was higher 90 days after surgery. Our findings apply particularly for THR patients aged 10 to 59 and 80 years and over. Although THR patients aged 80 years and over with high comorbidity level had lower mortality than corresponding persons from the general population, some particular groups of medical condition prior to surgery is associated with increased mortality risk whereas other medical conditions are associated with decreased mortality risk. We should be careful in making clinical decisions based on the Charslon comorbidity index; subgroups analyses may be necessary.

Further, we will present data on 90 days cause of death following primary THR and predictors for death, including age, gender and comorbidity (analyses are not finished yet).