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 a relatively short hospital stay with early rehabilitation in
the community. Reductions in length of stay also may explain the decrease in
mortality over the past three decades.
We would like to thank Professor Moran so much for his letter regarding our
article. Beginning in 1969, with the first total hip arthroplasty performed at
our institution, Dr. Mark Coventry (then chair of the Department of Orthopedic
Surgery here at Mayo) initiated a Total Joint Registry. Since that time, we
have prospectively gathered information on all patients undergoing hip
arthroplasty (and, subsequently, other total joint arthroplasties) at the time
of the index procedure and at regular follow-up intervals subsequent to the
operation. Details on this more-than-three-decade-long endeavor were recently
documented in an article by Berry et
al.1 As a result of
these early and continuing efforts, each and every patient is followed at six
to twelve weeks after surgery; at one, two, five, ten, and fifteen years after
surgery; and at five-year intervals thereafter. We now have patients with more
than thirty years of follow-up after procedures performed in the early 1970s.
Each follow-up interval represents an opportunity to track the patient and to
determine whether he or she has died since an earlier contact or appointment.
When patients are lost to follow-up, extensive efforts are undertaken by our
regular staff who are employed full-time in the endeavor to find them. If
there is no contact at their last known residence, then telephone contact is
made with county courthouses and other public sources of information regarding
residences and deaths in the area of the patient's last known address. Because
of this effort, we are confident about the data regarding mortality on our
patients during the first thirty days after an arthroplasty and indeed over
the ensuing years after the procedure.
The ability to generate reliable follow-up information from a large, single
institutional database has helped to serve as the basis for earlier
publications from our group on perioperative mortality following both hip and
knee arthroplasty and the effect of patient characteristics on
risk2,3.
In interpreting the data from our recent study of acute fracture patients,
it is important to note that, despite a substantial referral practice, a large
portion of our patients, and especially those with fractures, are drawn from
the nearby upper Midwest region. This area of the United States has a low
number of indigent patients and an under-representation of minority
populations when compared with the demographic characteristics in other areas
of the United States as well as in large urban centers both here and abroad.
These factors may result in a difference in observed mortality over the first
thirty days after hip arthroplasty for the treatment of acute fracture when
compared with other institutions serving a very different patient
demographic.
The authors wish to thank Professor Moran for his interest, and questions
such as these have helped to bring out several important points of potential
interest to other readers.
Berry DJ, Kessler M, Morrey BF.
Maintaining a hip registry for 25 years. Mayo Clinic experience. Clin
Orthop.1997;344:
61-8.34461
1997
[CrossRef]
Parvizi J, Johnson BG, Rowland C, Ereth
MH, Lewallen DG. Thirty-day mortality after elective total hip arthroplasty.
J Bone Joint Surg Am.2001;83:
1524-8.831524
2001
[PubMed]
Parvizi J, Sullivan TA, Trousdale RT,
Lewallen DG. Thirty-day mortality after total knee arthroplasty. J Bone
Joint Surg Am.2001;83:
1157-61.831157
2001