BLOG: Common clinical scenario of PJI after TJA
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In this blog, Victoria Tam, PA-S, discusses the etiology, risk factors, diagnosis and treatment of PJI. She includes a clinical case study to demonstrate how a prosthetic joint infection is diagnosed and managed.
- Sam Dyer, PA, president of Physician Assistants in Orthopaedic Surgery
The prevalence and incidence of total joint arthroplasty in the United States is high – about 7 million Americans are living with hip and/or knee replacements and more than 1 million TJA procedures are performed annually. Although the procedure is often successful, there are potential postoperative complications, with infection being one of the most devastating and difficult to treat. Periprosthetic joint infection (PJI) is currently one of the top reasons for revision arthroplasty, with an incidence range of 0.25% to 2%. This blog uses a theoretical clinical scenario to guide a detailed review of diagnostic criteria for PJI and outlines the current indications for several common treatment methods, including debridement, antibiotics and implant retention (DAIR); a one-stage revision arthroplasty; and a two-stage revision arthroplasty.
Common clinical scenario
A 53-year-old woman with diabetes mellitus and morbid obesity presents to the orthopedic surgeon’s office 8 months after total knee arthroplasty. She states the knee is hot and red, and she has had increased pain in the knee for the last few weeks. The orthopedic physician assistant seeing the patient recommended blood work, including erythrocyte sedimentation rate (ESR), C-reactive protein and white blood cell (WBC) count to rule out infection. The bloodwork came back with an elevated ESR and CRP, and thus the physician assistant aspirated the knee and sent the fluid to the lab for examination. The fluid showed an elevated WBC count and neutrophil count, and two cultures grew Staphylococcus aureus. The patient then asked, “How do you know the knee is infected? What is the best treatment for me?”
Diagnosis
Any new onset of pain in a joint prosthesis should be considered a potential infection. A thorough physical examination of the joint should be performed, noting any draining sinuses, effusion or cellulitis. Secondary symptoms of infection including fever, chills, erythema, joint effusion, decreased range of motion and inability to bear weight, should be carefully considered as well. The clinical diagnosis of PJI is based on a standardized criteria determined by the Musculoskeletal Infection Society (MSIS) and the Infectious Diseases Society along with the patient’s presenting symptoms. According to the updated MSIS criteria as described by Parvizi and colleagues, the diagnosis of PJI can be made if the patient presents with one of two major criteria or a combination of six minor criteria. Major criteria include: “two positive cultures of the same organism and sinus tract with communication to the joint or visualization of the prosthesis.”
Patients satisfying one of the two major criteria are considered infected as in the clinical case above. Patients who do not satisfy the major criteria are scored using the minor criteria comprised of six laboratory serum and synovial tests: elevated serum CRP, elevated serum D-dimer, elevated synovial WBC or leukocyte esterase count, elevated alpha-defensin, elevated synovial polymorphonuclear neutrophil percentage and elevated synovial CRP. A score range between 1 and 3 is assigned to each minor criterion: A total score of 6 or higher is considered infected, a score between 2 and 5 is an inconclusive diagnosis, and a score of 0 to 1 is considered not infected. Patients scoring between 2 and 5 are tested intraoperatively for infection confirmation using a positive histology, presence of purulence, and a single positive intraoperative culture.
To further determine the best course of treatment, acuity of the infection should be considered. Clinically, a PJI is considered acute if infection symptoms occur within 3 weeks or is less than 30 days from index procedure. Acuity is confirmed using an ESR/CRP ratio with a cutoff value of 0.96 for acute (< 0.96) or chronic (> 0.96) PJI. Once a clinical diagnosis of a periprosthetic joint infection is made, treatment options include: DAIR, one-stage revision or two-stage revision.
Debridement, antibiotics and implant retention
Debridement, antibiotics and implant retention is the least invasive procedure in the face of infection. However, successful infection eradication is inconsistent, with success rates ranging from 12% to 80%, and is largely dependent on symptom duration, time from index surgery, and infecting organism. DAIR is indicated for acute infections and candidates must have a well-functioning joint with no instability or loosening, a known infecting bacteria with specific antibiotic sensitivity, and an intact soft-tissue envelope with no evidence of sinus tracts outside the wound.
Contraindications to this procedure include a compromised immune system, Staphylococcus infections, multidrug-resistant or fungal infections, sinus tracts traveling outside the incision and poor soft tissue envelope. Samples should be obtained prior to the start of the surgery to confirm the causative organism of the infection. The procedure involves aggressive irrigation and debridement of the scar and surrounding tissue; modular components (polyethylene liner and/or femoral head) should be exchanged for sterile ones whenever possible. Antibiotic beads or other adjunct antibiotic therapy may be placed in the joint cavity per surgeon discretion prior to closure. Patients are prescribed an extended course of oral or IV antibiotics after surgery and are closely followed by infectious disease specialists. In certain cases, patients are given lifelong suppressive antibiotics after discussing with the infectious disease and surgical teams.
If the infected joint in question does not meet the criteria for DAIR or has failed the procedure, a one- or two-stage revision arthroplasty should be considered. A one-stage and two-stage are similar in that both require implant removal and eventual reimplantation. However, a one-stage revision is done within a single surgical event, while a two-stage protocol requires two surgeries: an implant removal and placement of antibiotic-impregnated cement spacer, and reimplantation of the prosthesis after infection eradication.
One-stage revision arthroplasty
A one-stage revision arthroplasty is not a commonly performed operation in the United States but has a low reinfection rate of 7.6%. The procedure is an option for patients who have an infected total hip arthroplasty, good soft tissue, a preoperatively identified antibiotic sensitive organism, availability of antibiotic-impregnated bone cement for implantation and healthy bone stock. Contraindications include organisms with high antibiotic resistance, polymicrobial infections, unidentified bacteria at time of procedure, chronic or reinfection, host immunosuppression, septic patients, poor soft tissue envelope and significant bone loss.
The one-stage revision procedure begins with removal of the prosthesis and any remaining cement in the bone cavity. Sinus tracts, if present, are excised and the infected scar, soft tissue and bone canals are aggressively irrigated and debrided. The wound is then chemically debrided with an aqueous povidone-iodine solution (with or without hydrogen peroxide) that is allowed to settle and then rinsed with a pulsatile lavage solution of sodium chloride to clear out any remaining debris. The wound is packed with povidone-iodine-soaked gauze and the incision is temporarily closed. The patient is re-draped with new drapes, contaminated surgical instruments are replaced with sterile ones, and the surgical team re-preps with new surgical gowns.
The patient is reimplanted with a new prosthesis that is secured into the joint with antibiotic-laden cement. After the procedure, patients are started on a standard rehabilitation protocol for revision arthroplasty and an antibiotic regime for at least 6 weeks.
Two-stage revision arthroplasty
A two-stage revision is currently considered the gold standard for treatment of a PJI with an infection-free survival rate of up to 95%. Indications for a two-stage procedure include chronic infection, poor soft tissue, difficult-to-treat bacteria or prior failed two-stage exchange. Contraindications include medically infirmed patients, multiply reinfected patients or multiple failed two-stage revisions, presence of necrotizing fasciitis, severe bone loss or failure of soft tissue coverage. During the first segment of the two-stage protocol, the prosthesis is explanted, and bone and soft tissue are thoroughly debrided. The patient is implanted with an antibiotic-impregnated static or articulated spacer, depending on the extent of bone loss, ligament laxity and tissue compromise. The cement spacer is kept in the joint for an extended amount of time while the infection is treated. A 6-week course of antibiotics is prescribed, and serial ESR, CRP and WBC markers are drawn to confirm infection eradication. The inflammatory markers are continually tested for another 2 to 4 weeks after the antibiotic course has been completed to optimize timing of the reimplantation. The revision arthroplasty is performed when all clinical symptoms of infection have subsided, and inflammatory markers are trending downward.
Conclusion
Periprosthetic joint infections require extensive workup to diagnose properly and are often challenging to treat. The optimal course of treatment is largely based on the timing from index surgery, infection duration, infecting microorganism and host immune factors.
In our common clinical scenario, the orthopedic team scheduled a two-stage revision for the patient based on her past medical history of a TKR more than 30 days old and a Staphylococcus infection. When presented with an acute infection with antibiotic-sensitive microorganisms, DAIR is an attractive course of treatment and can be successful under specific parameters outlined in the review.
Chronic or antibiotic-resistant PJI should be treated using a one-stage or a two-stage revision. Indications and contraindications should be carefully considered to maximize the success rate of the revision procedures.
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Collapse
Maradit Kremers H, Larson DR, Crowson CS, et al. J Bone Joint Surg Am. 2015;doi:10.2106/JBJS.N.01141.