The value of arthroscopic neosynovium biopsies to diagnose periprosthetic knee joint low-grade infection

Introduction

The diagnostic algorithm in cases of assumed low-grade infection after total knee arthroplasty is discussed controversial. The aim of this study was to evaluate the reliability of neosynovium biopsies via knee arthroscopies in predicting a periprosthetic knee joint infection (PJI).

Methods

From 2010 to 2015, 56 consecutive patients received a diagnostic arthroscopy of the knee joint by reason of an assumed PJI. In 34 cases, a revision arthroplasty was performed after the diagnostic arthroscopy. The microbiologic and histologic results from neosynovium biopsies were compared to intraoperative findings of the consecutively performed revision arthroplasty.

Results

The arthroscopic neosynovium biopsies had a sensitivity of 0.88 (0.47–1.0 95 % confidence interval), a specificity of 0.88 (0.7–0.98), a positive predictive value of 0.7 (0.35–0.93), and a negative predictive value of 0.96 (0.79–1.0). The accuracy was 0.88. We determined a higher sensitivity of neosynovium biopsies compared to C-reactive protein (p = 0.038) and white blood cell count (p < 0.001) in serum. The itemized evaluation of histologic results showed a significant higher sensitivity compared to microbiologic results (p = 0.045) and a higher accuracy.

Conclusions

The analysis of arthroscopic neosynovium biopsies can be helpful to verify or exclude a PJI in selected patients. Especially, histologic assessment showed a high accordance with final results.

Level of evidence IV, retrospective study.