Cell Count and Differential of Aspirated Fluid in the Diagnosis of Infection at the Site of Total Knee Arthroplasty

Ghanem, Elie; Parvizi, Javad; Burnett, R. Stephen J.; Sharkey, Peter F.; Keshavarzi, Nahid; Aggarwal2, Ajay; Barrack, Robert L.
August 2008
Journal of Bone & Joint Surgery, American Volume;Aug2008, Vol. 90-A Issue 8, p1637
Academic Journal
Background: Although there is no absolute diagnostic test for periprosthetic infection, the synovial fluid leukocyte count and neutrophil percentage have been reported to have high sensitivity and specificity. However, the cutoff values for these tests are not agreed upon. We sought to identify definite cutoff values for both the fluid leukocyte count and the neutrophil percentage that may help to diagnose infection at the site of a prosthetic joint. Methods: We analyzed synovial fluid that had been aspirated preoperatively from 429 knees that had undergone revision arthroplasty at three different academic institutions; 161 knees were found to be infected, and 268 knees were not. Using receiver operating characteristic curves, we determined cutoff values for the fluid leukocyte count and neutrophil differential with an optimal balance of sensitivity and specificity for the diagnosis of periprosthetic infection. The sensitivity, specificity, and predictive values were calculated for those cutoff values. The erythrocyte sedimentation rate and C-reactive protein level cutoff values of 30 mm/hr and 10 mg/L, respectively, were combined with the cutoff values for the fluid leukocyte count and neutrophil percentage. Results: The cutoff values for optimal accuracy in the diagnosis of infection were >1100 cells/10-3 cm³ for the fluid leukocyte count and >64% for the neutrophil differential. When both tests yielded results below their cutoff values, the negative predictive value of the combination increased to 98.2% (95% confidence interval, 95.5% to 99.5%), whereas when both tests yielded results greater than their cutoff values, infection was confirmed in 98.6% (95% confidence interval, 94.9% to 99.8%) of the cases in our cohort. Similarly, when both the neutrophil percentage and the C-reactive protein level were less than the cutoff values of 64% and 10 mg/L, respectively, the presence of periprosthetic infection was very unlikely. Conclusions: The synovial fluid leukocyte count and differential are useful adjuncts to the erythrocyte sedimentation rate and the C-reactive protein level in the preoperative workup of infection at the site of a total knee arthroplasty. The present study identified cutoff values for the leukocyte count (>1100 cells/10-3cm³) and neutrophil percentage (>64%) that can be used to diagnose infection. Combining the peripheral blood tests with the synovial fluid cell count and differential can improve their diagnostic value. Level of Evidence: Diagnostic Level III. See Instructions to Authors for a complete description of levels of evidence.


Related Articles

  • A circumferentially flanged tibial tray minimizes bone–tray shear micromotion. Barker, D. S.; Tanner, K. E.; Ryd, L. // Proceedings of the Institution of Mechanical Engineers -- Part H;Nov2005, Vol. 219 Issue 6, p449 

    Aseptic loosening of the tibial component is the major complication of total knee arthroplasty. There is an association between early excessive shear micromotion between the bone and the tray of the tibial component and late aseptic loosening. Using non-linear finite element analysis, whether a...

  • Towards a standard in assessment of bone cutting for total knee replacement. Barrera, O. A.; Haider, H.; Garvin, K. L. // Proceedings of the Institution of Mechanical Engineers -- Part H;Jan2008, Vol. 222 Issue 1, p63 

    Arthroplasty outcome is influenced by the ‘quality’ of bone preparation for implant insertion. Surgeons face increasing choices of technique and instrumentation, yet clinical scoring methods assess the overall outcome and patient satisfaction but not the bone cuts directly....

  • The History of Mobile-bearing Total Knee Replacement Systems. Hamelynck, Karel J. // Orthopedics;Sep2006 Supplement, Vol. 29, pS7 

    The use of a mobile-bearing knee system is routine in modern total knee arthroplasty (TKA). There are indications for use of a mobile-bearing TKA for a growing number of patients. The design, however, was not always well appreciated. Fears of perioperative difficulties and lack of understanding...

  • Trends in Total Knee Arthroplasty. Dennis, Douglas A. // Orthopedics;Sep2006 Supplement, Vol. 29, pS13 

    The success of total knee arthroplasty (TKA) over the past two decades of use has resulted in the implantation of TKA into younger patients who have increased functional requirements and demand increased implant longevity. Improved functional performance requires enhanced range of motion,...

  • Rationale for the Posterior-stabilized Rotating-platform Knee. Maniar, Rajesh // Orthopedics;Sep2006 Supplement, Vol. 29, pS23 

    The nonposterior-stabilized mobile-bearing knee and the posterior-stabilized fixed-bearing design have been successfully used for the past three decades. Lessons learned from their use have culminated in the design of a posterior-stabilized mobile-bearing knee that incorporates beneficial...

  • The P.F.C. Sigma RP-F Total Knee Arthroplasty: Designed for Improved Performance. Ranawat, Amar S.; Gupta, Sanjay K.; Ranawat, Chitranjan S. // Orthopedics;Sep2006 Supplement, Vol. 29, pS28 

    The new P.F.C. Sigma RP-F (rotating-platform high-flexion) knee has been designed to permit 155° of flexion after total knee arthroplasty (TKA) without compromising wear, polyethylene contact stresses, patellofemoral tracking, or stability. The purpose of this article is to describe the...

  • Clinical Results of Primary Low Contact Stress Cementless Total Knee Arthroplasty. Sorrells, R. Barry; Capps, Susan G. // Orthopedics;Sep2006 Supplement, Vol. 29, pS42 

    The published clinical and radiographic outcomes data for primary cementless low-contact stress (LCS) total knee arthroplasty (TKA) were examined. The majority of patients (92.6%) were pain free or had only mild pain, and excellent or good knee scores (99.1%) at follow-up. Patella difficulties...

  • The P.F.C. Sigma RP-F TKA Designed for Improved Performance: A Matched-pair Study. Gupta, Sanjay K.; Ranawat, Amar S.; Shah, Vineet; Zikria, Bashir A.; Zikria, Joseph F.; Ranawat, Chitranjan S. // Orthopedics;Sep2006 Supplement, Vol. 29, pS49 

    The press fit condylar P.F.C. Sigma RP-F (rotating-platform, high flexion) knee is designed to provide a range of motion (ROM) of 155° without compromising wear, polyethylene contact stresses, patellofemoral tracking, or stability. The first 50 TKA surgeries using the Sigma RP-F knee...

  • Management of the Severe Varus and Valgus Knee Using the Low Contact Stress Rotating Platform. Beverland, David // Orthopedics;Sep2006 Supplement, Vol. 29, pS60 

    Many surgeons feel the use of an unconstrained mobile-bearing knee is contraindicated in cases of severe varus and valgus deformity. In the author's opinion the Sigma LCS rotating-platform knee system can be used in virtually every primary knee irrespective of deformity. The key is to maintain...

  • Surgical Technique Tips and Pearls in Rotating-platform Knee Arthroplasty. Scott, Richard D. // Orthopedics;Sep2006 Supplement, Vol. 29, pS64 

    Rotating-platform mobile-bearing knee arthroplasties have potential advantages over fixed-bearing knee prostheses that may lead to better long-term wear of the polyethylene articulation. Their potential disadvantages include bearing spin-out that is usually the result of a tight posterior...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics