Neutrophil-to-Lymphocyte Ratio as a Marker for Postoperative Stress in Robot-Assisted Total Knee Arthroplasty

BACKGROUND Robot-assisted total knee arthroplasty (rTKA) has gained popularity due to its potential to improve outcomes of manual TKA (mTKA). The neutrophil-to-lymphocyte ratio (NLR) serves as a marker of immune activation and inflammation. This study evaluated the effectiveness of NLR in measuring the acute postoperative stress response following rTKA. MATERIAL AND METHODS This retrospective study included 50 patients with an average age of 67.8 years, and analyzed preoperative and postoperative NLR levels to assess stress in rTKA patients. The primary outcome was that over 90% of patients had a postoperative day (POD) 1 NLR value above 3. The secondary outcome was reduction of the mean NLR value to 50% or less of the POD 1 mean value on POD 3. RESULTS We observed that only 2 of 50 patients had an NLR below 3, confirming the primary outcome. The secondary outcome was also achieved, with Day 3 NLR decreasing to below 50% of the POD 1 value (from 9.48 to 4.54) - the mean preoperative NLR was 2.37±1.34; the NLR values increased to 9.48±6.53 on Day 1, then decreased to 5.04±2.76 on POD 2 and 4.54±4.11 on POD 3 (the value after "±" indicates the observed standard deviation). CONCLUSIONS Our results indicate that NLR monitoring is a valuable tool for assessing the acute postoperative stress response following rTKA, providing insights into early pathological processes. Patients with persistently elevated NLR values may potentially benefit from enhanced postoperative care.