Purpose: We analyzed perioperative parameters during the early postoperative period following total hip or knee arthroplasty (THA/TKA) to establish reasonable suspicion of prosthetic joint infection (PJI) before transitioning to a chronic phase where less invasive treatment methods are no longer effective. We investigated clinical, laboratory and radiological predictors for both low-grade and fulminant PJI in the first few postoperative days after primary THA/TKA.
Methods: We examined the internal registry of osteoarticular infections at the Valdoltra Orthopaedic Hospital between 2011–2021. An observational retrospective study with a control group included a cohort of 152 patients treated for PJI (32 low-grade PJI, 63 acute fulminant PJI, and 57 chronic fulminant PJI), all of whom underwent THA/TKA at the same institution. The control group size was predetermined at a ratio of at least 1 : 1 or more, based on the largest investigated PJI subgroup, and at a ratio of at least 2:1 based on the smallest investigated PJI subgroup. Non-parametric statistical tests were used to compare means of numerical and categorical demographic as well as surgeon-dependent variables (age, gender, BMI, malignancy, diabetes, inflammatory arthropathy, smoking, joint, implant, ASA, duration, intraarticular TXA, surgical drainage). The impact of laboratory and clinical parameters on the PJI risk in the early postoperative days after primary THA/TKA was studied using multivariate analysis for each PJI subgroup, controlling for confounding variables. Each laboratory parameter was systematically analyzed in a separate multivariate model for six different relationships (preoperative value, second postoperative day value, sum, difference, quotient, and product of preoperative value and second postoperative day value) alongside surgeon-dependent variables and prolonged wound discharge (PWD) as the sole predictive clinical parameter. Sensitivity and specificity for the PWD were analysed for each PJI subgroup for the first seven postoperative days, as well as for the product of preoperative leukocyte count and second postoperative day leukocyte count value for threshold values 70, 80, 90, 100, 110, 120, 130 and 140. We excluded the investigated radiological parameters from further analysis after a statistically non-significant basic statistical analysis.
Results: For each additional day of wound discharge, PWD increased the risk of PJI in the acute fulminant PJI subgroup with an odds ratio (OR) of 39.4 (p = 0.000, 95 % CI 1.171–1.661), and in the low-grade PJI subgroup with an OR of 26.0 (p = 0.045, 95 % CI 1.005–1.579), but not in the chronic fulminant PJI subgroup (OR 16.6, p = 0.142, 95 % CI 0.950–1.432). Following systematic analysis, the product of leukocyte count before surgery and on the second day after surgery >100 increased the risk of PJI in the acute fulminant PJI subgroup (OR 2.1, p = 0.025, 95 % CI 1.003–1.039) and in the chronic fulminant PJI subgroup (OR 2.0, p = 0.018, 95 % CI 1.003–1.036). A similar trend was observed in the low-grade PJI subgroup, but it was not statistically significant (OR 2.3, p = 0.061, 95 % CI 0.999–1.048). The most optimal predictive threshold value for PJI risk was observed solely in the acute fulminant PJI subgroup, where PWD exceeding three days after primary surgery was a significant risk factor for PJI with a sensitivity of 62.9% and specificity of 90.6%, while the product of preoperative leukocyte count and second postoperative day leukocyte count value exceeding 100 showed a specificity of 96.9 %. Basic statistical analysis of radiological parameters, glucose, erythrocytes, haemoglobin, platelets, and CRP values did not have statistically significant values in predicting early PJI risk.
Conclusions: The dynamics of laboratory and clinical parameters in the initial days after primary THA/TKA can predict low-grade and acute fulminant PJI. Prolonged wound discharge and leukocyte dynamics proved to be the most important predictors. With the analysis of radiological parameters, we were unable to demonstrate statistical significance in predicting early risk for PJI.
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