Background

Knee arthroplasty is a highly effective surgical procedure that significantly improves patient quality of life by providing symptom relief, restoration of limb or joint function, improved mobility and independence. Periprosthetic joint infection (PJI) remains one of its most serious complications. In the recent years, neutrophil to lymphocyte ratio (NLR) has emerged in the field of orthopedics as a marker to indicate subclinical inflammation in patients with septic arthritis.

Purpose

The aim of the study is to determine relationship of NLR to presence or absence of PJI in patients who underwent secondary surgery after total knee arthroplasty (TKA).

Methodology

This is a cross sectional study utilizing chart review. A list of all patients who underwent knee arthroplasty procedures was made and those who underwent secondary knee procedures were identified. These patients were classified as infected and non-infected based on intraoperative cultures from the prosthetic knee joint. Relationship of NLR with PJI was analyzed using Chi square as univariate analysis with odds ratio (OR) as outcome.

Results

A total of 685 knee arthroplasty cases were performed. Twelve were excluded from the study and analysis was conducted on 673 knees. There were 642 knees that underwent primary TKA and 31 were subjected to secondary knee arthroplasty procedures. PJI was noted in 16 knees (2.49%) based on positive intraoperative culture. When the cut off value of NLR was taken as 2.708 with a sensitivity of 87.5% (64-96.5, 95%CI) and specificity of 80% (54.8-93, 95%CI), there was a significant relationship of NLR and PJI with a p value of 0.0003 with OR of 28 (3.99-196, CI95%).

Conclusion

With NLR being significantly related to PJI, this readily available low cost marker may be maximized by initiating early diagnosis, that may contribute to timely treatment and reduction of morbidity and mortality.

Keywords:
Neutrophil to lymphocyte ratio, periprosthetic joint infection, infected total knee arthroplasty