We read with great interest the article by Lunz et al. [1], in which the authors dealt with
the new Periprosthetic Joint Infection (PJI)-TNM classification that was recently published
by our group (Table 1) [2–4]. PJI represents one of the most feared complications in the
orthopedic field, resulting in impaired quality of life, repeated and prolonged hospital stays,
and significant morbidity and mortality in affected patients. Still, there is no commonly
used classification system that could facilitate the comparison of treatment strategies and
patient outcomes [5,6]. Therefore, we are delighted with the authors’ conclusions that
“clinicians and researchers should be familiar with the new PJI-TNM classification and start
implementing it into their routine practice” [1].
The work of Lunz et al. [1] retrospectively assessed 80 consecutive PJI patients treated
with a two-stage exchange and was the first to correlate the PJI-TNM classification to
surgical parameters and some clinical outcome parameters, such as need for revision
surgery after stage one surgery, the duration of the interim period, and mortality. In
addition, Lunz et al. [1] believed that the initial PJI-TNM publication from our group
could be improved through certain modifications to the TNM backbone, resulting in a
“pTNM” version. An additional “p-status” (type of prosthesis) was proposed to distinguish
between standard implants (p0), revision implants (p1), and megaprostheses (p2). Further
suggestions were to add an “x” in front of the “p-status” to indicate a loosened implant and
to limit the criteria parameters for p, T, N, and M to only 0 = least serious, 1 = moderate,
and 2 = most serious by eliminating the letters for the subclassifications of the 0, 1, and
2 categories of our initially proposed classification. They also proposed the replacement
of the CCI for the assessment of patients’ comorbidities with the American Society of
Anesthesiologists (ASA) Physical Status Classification System [7]
