TNF-α concentrations in pre-operative synovial fluid for predicting early post-operative function and pain after fast-track total knee arthroplasty.

BACKGROUND

Tumor necrosis factor-alpha (TNF-α) helps regulate neuroinflammation and anxiety and could conceivable predict early post-operative pain and function after fast-track total knee arthroplasty (TKA).

METHODS

In patients with severe osteoarthritic knees undergoing TKA, we assessed: the correlations between pre-operative concentrations of TNF-α in synovial fluid; pre- and six-week post-operative knee function and pain; pre- and post-operative anxiety; pre- and post-operative synovial fluid concentrations of cartilage oligomeric matrix protein (COMP); age and body mass index (BMI).

RESULTS

Of 100 enrolled patients, 78 had evaluable TNF-α data, and 58 had evaluable COMP data. Pre-operative TNF-α concentrations were inversely correlated with post-operative pain scores during walking (r=-0.26, P=0.03) and with change of pain at rest during six weeks after TKA (r=-0.28, P=0.03) and were directly correlated with a higher post-operative Knee Society score (KSS) (r=0.43, P<0.001) and with greater increases in this score during six weeks after TKA (r=0.33, P=0.001). Mean TNF-α concentrations were higher in the 39 patients reporting any pre-operative pain at rest than in 36 patients reporting no pre-operative pain (P=0.015) and were the only independent predictor of pre-operative pain at rest (OR=13, P=0.02). Independent predictors of better post-operative knee function were higher log-transformed TNF-α concentrations (β=0.38, P=0.002) and male sex (β=0.28, P=0.02).

CONCLUSIONS

High levels of pre-operative TNF-α concentrations could be used as an independent predictor of better knee function at six weeks of follow-up. In patients with lower pre-operative TNF-α concentrations, post-operative pain management may improve the early outcome of the operated joint.