Diagnosis and Treatment of Acute Post-Operative Infections Following Primary Total Knee Arthroplasty
Craig J. Della Valle, MD
Infection is among the most feared complications following primary total knee arthroplasty (TKA). Diagnosis can be extremely difficult in the early post-operative period secondary to normal post-operative pain, edema and peri-incisional erythema that make the appearance of the wound and normal cues to diagnosis extremely difficult.
Treatment is equally difficult as there is a paucity of literature on the topic, and the reported rates of success are variable without a clear consensus on appropriate treatment.
Diagnosis of Infection in the Early Post-Operative Period
While the ESR and CRP have been found to be useful in the diagnosis of chronic periprosthetic joint infection, there is minimal data on their utility in the early post- operative period where one would expect they would be elevated and thus traditional cut- off values (30mm/hr for the ESR and 10-15mg/L for the CRP).
Similarly, while the synovial fluid WBC count has been shown to be useful for the diagnosis of chronic PJI in several studies, there is only recent literature on the utility of this test within the first few weeks where large amounts of blood would be expected to be around the hip joint and some inflammation would be expected.
- It has been our concern that if the values commonly used for the diagnosis of chronic PJI were utilized (~1,100 to 3,000 WBC/uL) with a differential of 60- 80% PMN were utilized at this early time point, we would be over diagnosing infection and unnecessary procedures would be performed
- Are these same tests useful and what optimal cut off points?
Retrospective review of 11,964 primary TKA at (2) centers (Jefferson, Rush)
- 146 Patients underwent re-operation or aspiration within first 6 wks post-op (1.2%)
- Aspirated at a mean of 16.5 days (range 2 to 42 days)
- 19 Diagnosed with PJI based on (+) operative cultures, 127 not infected
Mean Values for Patients with and without Acute Post-Operative Infection
|Infected (N=19)||Not Infected (N=127)||P-V alue|
|ESR (mm/hr)||80 (38-140)||75 (1-140)||0.46|
|CRP (mg.L)||171 (29-490)||88 (4-382)||0.004|
|Synovial Fluid WBC Count (per uL)||92,600
|4,200 (0-41,000)||< 0.001|
|Differential (% PMN)||90% (6-99)||77% (5-100)||0.0341|
ESR: Not found to be helpful
CRP: Helpful! Optimal threshold (balance sensitivity/specificity) 95 mg/L (nl 8 mg/L)
- 100 mg/L easier to remember
- Useful in equivocal situations; if > or somewhere near 100 mg/L aspirate the joint!
Synovial Fluid WBC Count: Helpful! In fact the most helpful test!
- If < 10,700 WBC/uL excellent rule out test
- If > 27,800 excellent rule out test
- Much higher than the threshold we typically use (1,100-3,000 WBC/uL)!
Differential (%PMN): Helpful!
- Optimal threshold 89% (90% easier to remember!)
Bottom Line: If you are unsure if you should aspirate, get a CRP; if >100 mg/L aspirate!
- If synovial fluid WBC count < 10,000 WBC/uL it is probably not infected!
- If synovial fluid WBC count > 27,800 WBC/uL it is infected
- If unsure, look at the differential; if > 90% PMN, it is probably infected!
- If still unsure, admit, start IV abx and wait for culture results
- Relatively easy to remember; CRP > 100mg/L, WBC > 10,000, differential > 90%
We have similar date for hips too! As of yet unpublished...
Treatment of Infection in the Early Post-Operative Period
Not a lot of literature to look to for guidance; most series are small, all are retrospective and the endpoints are variable and success is not uniformly defined. Most common treatment is an irrigation and debridement with exchange of the modular bearing surface (if present). Many have recently questioned the value of this intervention.
Irrigation and Debridement
Perform a full synovectomy and bearing surface exchange if possible (allows for better exposure particularly posteriorly) followed by six weeks of IV antibiotics (although again little data to support this precise time period of treatment) followed by a variable course of oral antibiotics ranging from no oral antibiotic treatment to lifelong suppression. Most studies suggest a success rate of ~50%
- Several studies have suggested that infections with resistant organisms (such as MRSA) do worse (harder to eradicate and harder to find an effective oral agent for longer term treatment)
- Similarly studies suggest that infections with Staphylococcal organisms do worse
- More recent studies show that results are poor regardless of the organism and timing of the debridement
- One recent study also suggested that a failed debridement MAY compromise your ability to eradicate the infection later (patients treated with a 2-stage exchange had a higher failure yet if they had a prior I+D)
- Should we perform multiple debridements? Antibiotic beads as interim adjunct?
One Stage Exchange: More recent interest in exploring this technique.
- Experience from Europe has been encouraging but requires removal of well fixed often times cemented components (not technically easy) and requires a stem?
- No data available on its utility in the early post-operative period
Two-Stage Exchange: A “conservative” option?
- No data on this option in the early postoperative period.
- Not easy to remove components as above. Necessary? Timing between stages?
Bottom Line: I+D is still what I do as my first option, however...
- Patients are counseled that the chance of success is 50% at best
- Low threshold to proceed to a 2-Stage exchange if therapy appears to be failing
- Clearly an area where further research is required to determine optimal treatment
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2. Bradbury T, Fehring TK, Taunton M, et. al. The fate of acute methicillin-resistant staphylococcus aureus periprosthetic knee infections treated with open debridement. J Arthroplasty. 2009 Sep;24(6 Suppl):101-4.
3. Deirmengian C, Greenbaum J, Stern J, Braffman M, Lotke PA, Booth RE Jr, Lonner JH. Open debridement of acute gram positive infections after total knee arthroplasty. Clin Orthop Relat Res. 2003 Nov;(416):129-34.
4. Della Valle C, Parvizi J, Bauer TW, et al. AAOS clinical practice guideline on the diagnosis of PJI. J Bone Joint Surg Am. 2011 Jul 20;93(14):1355-7.
5. Della Valle CJ, Sporer SM, Jacobs JJ, et. al. Perioperative testing for sepis prior to revision total knee arthroplasty. J Arthroplasty. 22: suppl 2, 90-93, 2007.
6. Sherrell JC, Fehring TK, Periprosthetic Infection Consortium. Fate of 2-Stage Exchange after Failed Debridement for Periprosthetic Knee Infection. Clin Orthop Relat Res. 2011 Jan;469(1):18-25.
7. Odum SM, Fehring TK, Periprosthetic Infection Consortium.Irrigation and Debridement for Periprosthetic Joint Infection. Does the Organism Matter? J Arthroplasty. 2011 Sep;26(6 Suppl):114-8.