Interleukin-6 serum concentration in the elderly undergoing total knee arthroplasty: A potential predictor of the early postoperative knee joint range of motion

PURPOSE: To analyze the relevance between serum IL-6 with the early postoperative (post-op) knee joint range of motion (ROM) in the elderly undergoing total knee arthroplasty (TKA). To evaluate the factors affecting early post-op knee joint ROM in the elderly after TKA. METHODS: One hundred and forty-three patients undergoing TKA were included. The patients' general data, perioperative knee joint ROM and serum IL-6, pre-op HSS, WOMAC, SF-36 scores and Wells scores were collected. Repeated data variance analyses were performed to analyze the relevance between serum IL-6 with post-op knee joint ROM. Correlative regression and regression analysis were performed to evaluate the multiple factors affecting knee joint ROM in the elderly undergoing TKA. RESULTS: The 2-week-post-op (2w-post-op) knee joint ROM was significantly higher in the low IL-6 serum concentration group (< 46.45 ng/L) than in the high group (>= 46.45 ng/L) (97.78 +/- 7.44 degrees VS 91.85 +/- 7.42 degrees, F = 16.860, P = 0.000). A significant negative correlation was found between 1d-post-op serum IL-6 concentration with 2w-post-op knee joint ROM (R = 0.513, P = 0.000). The factors influencing the 2w-post-op knee joint ROM included pre-op HSS scores, pre-op WOMAC scores and whether to retain PCL (posterior cruciate ligament) (R-2 = 0.451, P = 0.009). CONCLUSION: A higher 1d-post-op IL-6 serum concentration indicated a lower knee joint ROM in the elderly two weeks after TKA.