Thirty-Day Mortality Following Hip Arthroplasty

To The Editor: I read with great interest the article entitled “Thirty-Day Mortality Following Hip Arthroplasty for Acute Fracture” (2004; 86:1983-8), by Drs. Parvizi, Ereth, and Lewallen. I would be grateful for some more detail on the calculation of thirty-day mortality. Thirty-day mortality should only be calculated when the status (i.e., dead or alive) is known for each patient in the cohort or population thirty days after the index event. Complete follow-up of the entire cohort is required for this calculation. A thirty-day mortality of 2.4% is remarkably low for a population of elderly patients with hip fractures, particularly as the background mortality (death by natural causes) is 0.8% per month. Were the authors calculating inhospital mortality, rather than true thirty-day mortality? This is an important issue if mortality rates are to be compared between institutions as the low mortality rate quoted by the authors could have been due to … Corresponding author: David G. Lewallen, MD Department of Orthopedics Mayo Clinic 200 First Street S.W. Rochester, MN 55905 lewallen.david{at}mayo.edu