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Assessing the TNM Classification for Periprosthetic Joint Infections of the Knee: Predictive Validity for Functional
Arne Kienzle1,2,3, Sandy Walter1,4, Paul Köhli1,2
1Center for Musculoskeletal Surgery, Clinic for Orthopedics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany.
Abstract:
Background: Periprosthetic joint infection (PJI) following knee arthroplasty can significantly compromise patient mobility and quality of life. The newly proposed TNM classification system, adapted from oncology, categorizes PJI severity but has not yet been correlated with both subjective and objective outcomes post PJI treatment. Objective: This study evaluates the applicability of the TNM classification system for predicting outcomes in knee PJI revision surgeries. Methods: We conducted a retrospective analysis of 108 patients who underwent revision surgeries for knee PJI at our institution from January 2012 to January 2023. We assessed the correlation between the TNM classification and postoperative outcomes using the Knee Society Score (KSS) function and knee score, as well as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Results: The TNM classification demonstrated that higher 'T' stages were significantly associated with worse functional and subjective outcomes. The 'N' classification had limited predictive value, likely due to treatment adjustments based on pathogen type. The 'M' classification correlated with functional outcomes but not with subjective scores, suggesting that patients with more severe preoperative comorbidities might adjust their expectations. Conclusions: While the TNM classification shows potential, its current form as a prognostic tool in PJI management is limited. Enhancing the 'T' component, coupled with the integration of a validated morbidity score such as the CCI could improve its prognostic value. Despite its shortcomings, the TNM system may still provide valuable prognostic insights for both patients and surgeons in tackling complex PJI.
Insights
The TNM classification shows promise for predicting outcomes after knee periprosthetic joint infection (PJI) revision surgery, with higher
Area of Science:
- Orthopedic Surgery
- Infectious Diseases
- Oncology
Background:
- Periprosthetic joint infection (PJI) after knee arthroplasty significantly impacts patient function.
- The TNM classification, adapted from oncology, is a novel system for grading PJI severity.
- Its predictive value for treatment outcomes in knee PJI revision remains unestablished.
Purpose of the Study:
- To evaluate the TNM classification system's applicability in predicting outcomes following knee PJI revision surgery.
- To correlate TNM staging with both subjective and objective patient outcomes post-treatment.
Main Methods:
- Retrospective analysis of 108 patients undergoing knee PJI revision surgery (January 2012 - January 2023).
- Assessment of TNM classification against postoperative outcomes using the Knee Society Score (KSS) and WOMAC index.
- Correlation analysis between TNM stages and functional/subjective scores.
Main Results:
- Higher TNM 'T' stages significantly correlated with poorer functional and subjective outcomes.
- 'N' classification showed limited predictive utility, potentially due to pathogen-specific treatment modifications.
- 'M' classification linked to functional outcomes but not subjective scores, possibly due to comorbidity-adjusted expectations.
Conclusions:
- The TNM classification demonstrates potential for PJI prognostication but requires refinement.
- Enhancing the 'T' component and integrating morbidity scores (e.g., CCI) could improve prognostic accuracy.
- The TNM system offers valuable insights for managing complex knee PJI, aiding both patients and surgeons.
