Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections

Abstract

The comprehensive “PJI-TNM classification” for the description of periprosthetic joint infections (PJI) was introduced in 2020. Its structure is based on the well-known oncological TNM classification to appreciate the complexity, severity, and diversity of PJIs. The main goal of this study is to implement the new PJI-TNM classification into the clinical setting to determine its therapeutic and prognostic value and suggest modifications to further improve the classification for clinical routine use. A retrospective cohort study was conducted at our institution between 2017 and 2020. A total of 80 consecutive patients treated with a two-stage revision for periprosthetic knee joint infection were included. We retrospectively assessed correlations between patients’ preoperative PJI-TNM classification and their therapy and outcome and identified several statistically significant correlations for both classifications, the original and our modified version. We have demonstrated that both classifications provide reliable predictions already at the time of diagnosis regarding the invasiveness of surgery (duration of surgery, blood and bone loss during surgery), likelihood of reimplantation, and patient mortality during the first 12 months after diagnosis. Orthopedic surgeons can use the classification system preoperatively as an objective and comprehensive tool for therapeutic decisions and patient information (informed consent). In the future, comparisons between different treatment options for truly similar preoperative baseline situations can be obtained for the first time. Clinicians and researchers should be familiar with the new PJI-TNM classification and start implementing it into their routine practice. Our adjusted and simplified version (“PJI-pTNM”) might be a more convenient alternative for the clinical setting.

The PJI-TNM classification for periprosthetic joint infections

“…Future refinement of the PJI-TNM classification could consider simplification while balancing the need for detailed classification to enhance interobserver agreement. 30 In the present study, the use of the PJI-TNM educational app was comparable to the conventional classification method. Although an increase in interobserver reliability was expected due to increased support provided by the classification tool, the lack of improvement could be due to the persistent difficulties of the classification system, for example, in the preoperative assessment of implant stability or the assessment of morbidity, as mentioned above.…”

“…Finally, the present study does not allow conclusions to be drawn about whether the classification is useful for treatment decisions or predicting treatment success. Although Lunz et al 30 already described a predictive value regarding surgery (duration of surgery, blood loss, and bone loss during surgery), to determine the likelihood of reimplantation, and patient mortality during the first 12 months after diagnosis based on the PJI-TNM classification and its modified version, further studies are needed to support these results.…”

“…Future refinement of the PJI-TNM classification could consider simplification while balancing the need for detailed classification to enhance interobserver agreement. 30 …”

Making the diagnosis in prosthetic joint infection: a European view

“…Three variables were used, T: Tissue and implant conditions, N: Non-human cells (bacteria and fungi) and M: Morbidity of the patient. The PJI-TNM classification incorporates over 200 possible permutations although it has now been simplified in a condensed version, the pTMNr ( 69 ). The stated clinical application is to guide management into four possible treatment categories: DAIR (T0N0), implant removal (T1, T2, N1, N2), a ‘less aggressive’ operation (M3b) or non-operative management (M3a, M3c) ( 63 ).…”

Comment on Lunz et al. Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections. J. Clin. Med. 2023, 12, 1262

“…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 , 3 , 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.…”