A 56-year-old woman presented with history of rheumatoid arthritis with progressive right hip pain and an inability to walk. She has a subcutaneous fluctuant mass with a sinus tract. Her anteroposterior radiograph is presented below. What would you do?
Gwo-Chin Lee, MD: Deep prosthetic infections following total hip arthroplasty (THA) can cause significant morbidity to the patient and pose significant challenges to the surgeon. Success in infection eradication and control depends on the organism, host factors, and requires a stepwise and systematic approach. What is your initial approach when a patient presents with a painful hip replacement?
Raymond H. Kim, MD: The workup should include taking a careful history, performing a detailed physical examination, obtaining radiographs, and obtaining laboratory work, including an erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), to rule out infection. Careful attention should be paid to extra-articular causes of hip pain, including lumbar spine pathology, abdominal pathology (including the presence of an inguinal hernia or gynecologic sources in women), and soft tissue etiologies including psoas tendonitis or hip bursitis.
Dr Lee: Are there particular things in the history and physical examination that can point to infection as the source of pain and dysfunction?
Bryan D. Springer, MD: The history and physical examination may be the most important aspects in the infection diagnosis. However, patients are often unaware of infection as a problem and may not offer important information unless asked. It is important to know whether patients had any issue with wound healing postoperatively and whether they were ever placed on antibiotics to treated a presumed infection. This helps determine whether they could be immunocompromised from medications or illness. In addition, the character of patients’ pain is important to ascertain. Patients who have constant pain, particularly at rest, or who did not have pain relief postoperatively should always raise the suspicion of infection.
Dr Lee: Are there any imaging tests, in addition to radiographs, that you would order to evaluate the patient with a painful THA?
Sebastién Lustig, MD: In France, we frequently obtain bone scan and leukocyte scans as part of the workup for a painful THA. Sometimes a computed tomography scan can be helpful in evaluating the hip for abcess, loose bodies, or osteolysis. For patients with metal-on-metal bearings, metal-suppression magnetic resonance imaging can be useful to look for fluid collections or pseudotumors.
Dr Springer: I rarely use bone or indium scans because they are costly and time consuming for the patients and lack specificity. The only time that I consider using them is if serological markers are elevated and we are unable to aspirate any fluid from the hip to make a definitive decision regarding infection. If I order nuclear imaging, I always order a combined test of a bone and indium scan and sulfur colloid scans. This combination has been shown to improve both the sensitivity and specificity of the test.
Dr Lee: Do you routinely aspirate painful THAs?
Dr Kim: An aspiration will be ordered if the ESR and CRP are elevated to confirm the presence of infection and to determine the type of organism and sensitivity to various antibiotics. Because of the possibility of a false–positive result, I will not order an aspiration in the setting of normal inflammatory markers.
Dr Lee: How do you interpret cell counts in the setting of metal-on-metal bearing surfaces?
Dr Springer: The metal-on-metal bearings have resulted in new issues with regard to hip aspiration. I have seen patients with adverse reactions to metal debris with a variable presentation and elevated cell counts that can often mimic infection. However, a predominance of lymphocytes as opposed to leukocytes in the aspirate is often seen in the differential. I have a lower threshold to aspirate a painful metal-on-metal THA, looking for signs of metal debris in the fluid.
Dr Lustig: In cases of metal-on-metal THAs, automated differential counts are often artificially elevated and unreliable. Therefore, a manual differential of the synovial fluid should be requested in this setting.
Dr Lee: Typically, how long do you require a patient to be off antibiotics prior to hip aspiration?
Dr Kim: A patient should be off antibiotics for a minimum of 2 weeks prior to aspiration to prevent a false–negative culture result. The longer the patient is off antibiotics, the more accurate the results are likely to be.
Dr Lee: Does the timing of infection affect your management?
Dr Springer: Looking at the recent results published in the literature, I think we all need to question the efficacy of irrigation and debridement as a treatment for acutely infected total joint replacements. This is regardless of the time from surgery (acute postoperative or late acute hematogenous) or the organism that is present. Although it is an attractive low-morbidity option, the literature would suggest at best a 50% to 60% success rate.1 I would most likely only perform an irrigation and debridement with liner and head exchange in patients with a true late acute hematogenous infection and < 1 week of symptoms, unless they have a resistant organism, such as Methicillin-resistant Staphylococcus aureus, where I would lean more toward a 2-stage exchange. In a patient with an early postoperative infection, single-stage exchange might be better performed before the components are ingrown, but more data are needed to evaluate this treatment modality.
Dr Lee: How do you manage chronically infected THAs?
Dr Lustig: For chronic infections, we recommend resection and removal of the implants, placement of antibiotic spacer (nonarticulating), treatment using culture-specific antibiotics, and reimplantation when the inflammatory markers have normalized. In cases with femoral and acetabular bone loss, we use a unipolar spacer to maintain the relationship between the acetabulum and the femur to facilitate subsequent reconstruction.
Dr Kim: Typically, I would use an articulating spacer, which provides the advantage of increased mobility for the patient after the first stage. In the setting of either severe femoral or acetabular bone loss (as in the patient whose radiograph was provided for this column), I would use a nonarticulating antibiotic cement spacer and have the patient minimize weight bearing. This patient’s preoperative radiographs (Figure) are concerning for a possible pelvic discontinuity, and other imaging studies are required to evaluate this (Judet views or computed tomography scan).
Dr Lee: What concentration and mixture of antibiotics do you use in your cement?
Dr Lustig: I use Palacos Bone Cement (Zimmer, Warsaw, Indiana) with pre-mixed gentamycin for our cemented spacers. Provided adequate debridement and removal of the components, cement, and other hardware is performed, I do not feel it necessary to add additional antibiotics.
Dr Springer: High-dose antibiotic cement spacers are the key to successful treatment. I use a high-viscosity cement that has shown excellent elution properties. I typically use 2.4 g of tobramycin and 2 g of vancomycin per pack of cement when making a spacer for the hip joint. For a lower viscosity cement, I would double the amount of antibiotics.
Dr Kim: I typically use 4 g of vancomycin and 4.8 g of to-bramycin per batch of cement. Atypical infections (fungal or mycobacterium) may require organism-specific antimicrobials for the cement.
Dr Lee: What is your infection protocol? How long do you treat patients with intravenous antibiotics? When do you proceed with reimplantation?
Dr Springer: The length of antibiotic treatment is determined in conjunction with an infectious disease specialist. This is generally a 6-week course of intravenous antibiotics. If serological markers are not trending down, this treatment may be extended. Then, I prefer a 6-week antibiotic course to observe patients clinically and follow their serological markers.Although I would like to see the ESR and CRP normalize prior to reimplantation, this does not happen in the majority of patients. However, the trend is important, and I must see it trending toward normal prior to reimplantation. If it does not, then antibiotic treatments can be lengthened, or often a repeat debridement with spacer exchange is performed.
Dr Lustig: We keep our patients nonweight bearing and give culture-specific antibiotics for a minimum of 6 weeks. Once the ESR and CRP have normalized, we proceed with reimplantation surgery without a period off antibiotics and continue intravenous antibiotics for another 6-week course to complete a total of 3 months. However, if the ESR and CRP have not normalized, we perform another spacer exchange and restart the process over again.
Dr Lee: Dr Lustig, are there any other differences between how infections are managed in the United States compared with France?
Dr Lustig: There is a strong tendency to centralize revison arthroplasty surgery for infections in big centers specialized in that sort of surgery. For example, in France, there are 8 such centers, 1 for each region of our country. Furthermore, primary exchange surgery is gaining popularity in our country and throughout Europe. For these cases, the regimen involves identifying the infected organism preoperatively, starting intravenous antibiotics for 2 weeks leading to the surgery, and proceeding with a single-stage exchange using preferably uncemented hip implants.
Dr Lee: As we can see, although some differences are found in approaches among surgeons, as well as differences between how infection are managed in the United States compared with other parts of the world, the principles of treatment are similar. The American Academy of Orthopaedic Surgeons has developed guidelines for the diagnosis, workup, and management of patients with prosthetic infections. Using these guidelines and taking a systematic approach to the patient with an infected THA will help optimize outcomes.
- Sherrell JC, Fehring TK, Odum S, et al. the Periprosthetic Infection Consortium. The Chitranjan Ranawat Award: fate of two-stage reimplantation after failed irrigation and débridement for periprosthetic knee infection. Clin Orthop Relat Res. 2011;469(1):18–25. doi:10.1007/s11999-010-1434-1 [CrossRef]