We read with interest "Evaluation of Preoperative
Cultures Before Second-Stage Reimplantation of a Total Knee Prosthesis
Complicated by Infection. A Comparison-Group Study" (82-A: 1552-57,
Nov. 2000), by Mont et al.
It is unclear to us how the results of pre-reimplantation laboratory
tests and intraoperative frozen-section analysis determined the
decision to reimplant or redébride the affected knees.
Specifically, the authors state in the Materials and Methods
section that preoperative and postoperative radiographs, nuclear
medicine scans, laboratory findings, and culture results were reviewed.
In the Treatment subsection, the authors state that all patients
deemed free of infection with use of specimens (presumably frozen-section
specimens) at the time of reimplantation were not given antibiotics.
We think it is very important to utilize frozen-section analysis
and perioperative laboratory tests in the decision-making process,
and we have had success in doing so in our practice to avoid reimplantation
in the setting of persistent infection. Much of the data supporting
this approach has been published previously in The Journal.
Inconclusive or positive frozen-section analyses have led us to
redébride the joints and wait for the five-day culture results
prior to considering second-stage reimplantation of both hip and knee
prostheses.
It would be very helpful if Drs. Mont, Waldman, and Hungerford
could comment on subcategories within the two treatment groups in
regard to the use of frozen-section analysis and perioperative laboratory
tests. In light of their conclusion that "prerevision cultures, after
the discontinuation of antibiotic treatment, should be performed
in all patients treated with this procedure," this information
needs to be clarified.
M.A. Mont, B.J. Waldman, and D.S. Hungerford reply:
In answer to Dr. McGrory and Dr. Becker, as described in the
Study Groups and Treatment subsections of the article, two screening
methods that we recommend were used at the time of reimplantation
for Group-II patients. First, a culture of material obtained from
one knee-joint aspiration was performed four weeks after completion
of the antibiotic therapy. If the culture was positive, the patient
was managed with repeat irrigation and débridement. If
the culture was negative, the patient was scheduled for possible
reimplantation depending on the results of intraoperative gram stains
and frozen-section analysis, which constituted the second screening
for infection. If a knee was found to be free of infection (with
negative gram stains and specimens that were completely free of
polymorphonuclear leukocytes) at the time of reimplantation, no
antibiotics were given. If a knee had persistent infection (positive gram
stain or frozen section), the knee was débrided again and
another course of antibiotics was given, after which the patient
was re-entered into the protocol.
On the basis of this protocol for Group-II patients, thirty-one
of thirty-four had negative cultures as well as negative gram stains
and frozen sections. Of these patients managed with second-stage
total knee arthroplasty, thirty of the thirty-one were free of infection
and one patient had a recurrent infection caused by an organism
different from the initial infecting organism.
Three patients had positive cultures (as well as polymorphonuclear
leukocyte counts greater than ten cells per high-power field in
the frozen-section analysis), and they were treated with another six-week
course of intravenous antibiotics after more operative débridement. These
three patients subsequently had a negative culture and a successful
revision knee arthroplasty.
We hope that this clarifies our treatment algorithm for Dr. McGrory
and Dr. Becker, as well as for other readers, and shows how the
use of prerevision cultures can save knees from recurrent infection
that might otherwise have been reimplanted.