Normal sequential changes in neutrophil CD64 expression after total joint arthroplasty

BACKGROUND Neutrophil CD64 has been reported to be a sensitive and specific infection marker. Its measurement is thus considered to be useful in early diagnosis of post-operative periprosthetic infection. However, even its normal sequential changes after non-infectious total joint arthroplasty have remained ambiguous. Accordingly, we analyzed 2-week sequential neutrophil CD64 expression changes after total joint arthroplasty in order to clarify its normal postoperative kinetics. PATIENTS AND METHOD From 41 patients who underwent primary total joint arthroplasties, peripheral blood samples were obtained at 1 day before (baseline) and 1, 3, 5, 7, and 14 days after surgery, and CD64 expression per cell was quantitatively measured. C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR) and white blood cell count (WBC) were simultaneously measured. RESULTS No cases of postoperative local infection were observed. Levels of CD64 significantly elevated from day 1, peaked at day 3, and decreased significantly following day 5. Statistical analysis confirmed that significant differences existed between the baseline level and the levels at days 1 and 3, while no significant differences existed between the baseline level and those at days 5, 7 or 14. In 17 patients, CD64 peaked at over 2,000 molecules/cell, the level reported to be a cutoff value for distinguishing infection. Multiple regression analysis showed that the sole parameter of baseline CD64 level significantly explained the peak CD64 level. Postoperative CD64 peaks ranged from 1.6 to 2.7 times (median 1.9) the baseline levels. CRP, ESR and WBC also showed rapid elevations and all but WBC remained significantly higher than baseline at day 14. CONCLUSION CD64 levels rise significantly, peaking within about 3 days following normal total joint arthroplasty, but decrease rapidly to near baseline within about 5 days. The data obtained can be expected to form a possible basis for early diagnosis of postoperative periprosthetic infection.