Knee Aspiration
We recommend joint aspiration of patients being assessed for periprosthetic knee infections who have abnormal erythrocyte sedimentation rate AND/OR C-reactive protein results. We recommend that the aspirated fluid be sent for microbiologic culture, synovial fluid white blood cell count and differential.
STRONG RECOMMENDATION Rationale
Our systematic review of the literature suggests that ESR/CRP testing is valuable for screening (ruling out) of periprosthetic infection with extremely high sensitivity (>90%). These tests are not, however, specific for diagnosis of periprosthetic infection and may be elevated with any type of infection or inflammation. Hence, for patients with abnormal ESR/CRP who are being investigated for periprosthetic infection of the knee, the most appropriate next test is aspiration of the knee joint.
We recommend that the fluid obtained from the joint be sent for analysis of synovial fluid white blood cell count, percentage of neutrophils, and also culture for aerobic and anerobic organisms. Studies suggest either synovial fluid white blood cell count over 1700 cells/µl (range, 1100-3000) or neutrophil percentage greater than 65% (range 64%-80%) is highly suggestive of chronic periprosthetic infection.21, 33, 103 However, the threshold for cell count and neutrophil percentage indicative of acute periprosthetic joint infection (within six weeks of index arthroplasty) is yet to be determined and the values and ranges reported above may not be applicable when diagnosing acute periprosthetic infections.
We recommend that the fluid obtained from the joint be sent for analysis of synovial fluid white blood cell count, percentage of neutrophils, and also culture for aerobic and anerobic organisms. Studies suggest either synovial fluid white blood cell count over 1700 cells/µl (range, 1100-3000) or neutrophil percentage greater than 65% (range 64%-80%) is highly suggestive of chronic periprosthetic infection.21, 33, 103 However, the threshold for cell count and neutrophil percentage indicative of acute periprosthetic joint infection (within six weeks of index arthroplasty) is yet to be determined and the values and ranges reported above may not be applicable when diagnosing acute periprosthetic infections.
- (105) Trampuz A, Piper KE, Jacobson MJ et al. Sonication of removed hip and knee prostheses for diagnosis of infection. N Engl J Med 2007;357(7):654-663.
- (21) Della Valle CJ, Sporer SM, Jacobs JJ, Berger RA, Rosenberg AG, Paprosky WG. Preoperative testing for sepsis before revision total knee arthroplasty. J Arthroplasty 2007;22(6 Suppl 2):90-93.
- (31) Fink B, Makowiak C, Fuerst M, Berger I, Schafer P, Frommelt L. The value of synovial biopsy, joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements. J Bone Joint Surg Br 2008;90(7):874-878.
- (33) Ghanem E, Parvizi J, Burnett RS et al. Cell count and differential of aspirated fluid in the diagnosis of infection at the site of total knee arthroplasty. J Bone Joint Surg Am 2008;90(8):1637-1643.