Periprosthetic infection occurs in approximately 0.8% to 1.9% of all total knee arthroplasties (TKAs).1 The most common cause of infection in TKA is methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S aureus (MRSA).2 It is rare, however, to find a zoonotic bacterium involved with a prosthetic device. To the authors' knowledge, there has only been one reported case of Francisella tularensis infection found in a total joint occurring in Ottawa, Ontario, Canada, while another infection from F tularensis was found in a ventriculoperitoneal shunt infection in St. Louis, Missouri.3,4
Francisella tularensis is a highly virulent, gram-negative coccobacillus zoonotic bacterium responsible for tularemia.4–6 From 1990 to 2000, an average of approximately 120 cases of tularemia per year were seen in the United States.7 Common vectors for the disease include aerosol droplets, contaminated water, arthropods (ie, ticks, flies, and mosquitoes), and various mammals, with the most prevalent being rabbits.5,7,8 Symptoms of infection with tularemia typically involve fevers, chills, headaches, vomiting, anorexia, and fatigue; however, other findings have been reported.7,8 The current authors report what is believed to be the second documented case of a total joint infection with F tularensis in the world and the first documented case in the United States.
A 58-year-old man underwent a left TKA in 1994 and a right TKA in 1997 for severe primary bilateral knee osteoarthrosis. In 2015, he presented to the authors' clinic with knee pain after falling onto his left knee. He underwent a computed tomography scan to confirm the presence of polyethylene failure. The images suggested polyethylene wear and fracture, and the patient elected to proceed with a left TKA polyethylene exchange. During the operation, no periprosthetic osteolysis or evidence of infection was noted.
Five months postoperatively, he was healing uneventfully when he fell onto his left knee. After the fall, the range of motion in the patient's left knee was somewhat limited, but there were no findings to suggest the surrounding skin had been compromised. Eight months postoperatively, he developed a fluctuant, nontender mass overlying the lateral aspect of his left knee. This mass was planned to be aspirated at the same time he was scheduled to undergo a right knee polyethylene exchange due to significant wear of the medial polyethylene component.
Three weeks before surgery on his right knee, the patient presented with painful bilateral knee swelling. Moderate effusion was noted in both knees, and aspiration was performed. Two weeks later, he presented to the clinic requesting repeat aspirations for a recurrence of symptoms. Blood-tinged, nonpurulent, synovial fluid was aspirated from both knees in a sterile fashion with no evidence of infection. The patient underwent revision on the right knee and ganglion aspiration on the left knee. Intraoperatively, he had abundant synovitis, which was debrided, and the polyethylene liner was replaced.
The patient returned for his 1-week postoperative appointment with no complications or signs of deep infection, such as persistent wound drainage or hematoma.9,10 Of note, the left knee also had minimal swelling with no erythema, active drainage, or warmth, and there were no systemic signs of infection such as fevers, chills, nausea, or vomiting.
Five weeks postoperatively, the patient returned to the clinic for a wound check due to the possibility of cellulitis at the superior pole of his right knee incision. The patient was prescribed 500 mg of cephalexin to take at 6-hour intervals during a 7-day period. After 10 days, the superficial erythema had resolved, and there were no further signs of infection in the right knee.
More concerning was the amount of times the patient came into the office requesting knee aspirations. At 1½ weeks, 2 months, 2½ months, and 6 months following his surgery, the patient presented with persistent increased swelling and limited range of motion in either his left, right, or both knees. Radiographs obtained at his 2- and 6-month appointments demonstrated proper hardware alignment with no signs of infection. Aspirations were performed 1½ weeks, 2½ months, and 6 months following surgery, and the patient reported immediate pain relief following the aspirations. No identifiable evidence of infection was present in the aspirate or on physical examination at any follow-up appointment.
Finally, 9 months postoperatively, the patient continued to have bilateral knee swelling with ballotable fluid located on the lateral aspect of each knee. Thus, 30 cc of straw-colored serous fluid was aspirated from the left knee and was sent for culture and sensitivities. No cell counts or other laboratory studies such as crystal analysis were ordered. The following day, laboratory results indicated a negative Gram stain, no rare polymorphonuculear white cells, and no organisms. However, between 24 and 48 hours, aerobic culture demonstrated 4+ quantity of growth of F tularensis. These results were confirmed with repeat culture of the original specimen and polymerase chain reaction analysis at the Colorado Department of Public Health and Environment.
Subsequently, repeat bilateral knee aspirations were performed using ultrasound guidance; 25 mL of yellowish fluid was aspirated from both knees and sent to the laboratory for repeat analysis. The analysis found F tularensis (2+) in the left knee; the right knee was negative for any growth. Each culture was held for 14 days on a blood agar medium. Although no growth was observed in the right knee, it was believed lower levels of the bacteria were present based on the persistent, symmetrical swelling. No antibody titer was conducted. The patient was prescribed doxycycline to be taken daily for chronic suppression rather than subsequent revision as it was believed suppression would be better tolerated because of his age, the bilateral involvement, and his current asymptomatic nature. Although bilateral knee swelling continues to occur, the patient has not noted any specific complications other than occasional mild joint discomfort from the swelling.
In searching for possible sources of bacterial introduction, the patient reported no distinct interactions with ticks, rabbits, or other animals that are common risk factors. However, he is a farmer with a large amount of crop land, and he stated there were instances when he could have encountered rabbit carcasses when mowing his hay fields both before and after his bilateral total knee revisions. His infectious disease physician hypothesized that after exposure to a rabbit carcass when mowing, the F tularensis bacterium entered his body either from a small superficial abrasion on his hands or from a bacterium present within hay dust that was inhaled and then spread systemically to the left knee prosthesis.
As the rate of total joint implantation continues to increase, with 3.5 million procedures projected to be performed annually by 2030 compared with 450,000 procedures in 2005,11 it is likely that the prevalence of zoonotic infection will increase as well. After reviewing the current patient's case, in the face of persistent swelling within a knee joint replacement despite no cardinal signs of infection, the authors recommend synovial aspiration be performed and tested for zoologic bacterium as well for other more common bacteria. It should be restated alongside the first reported case in 1999, which was titled, “Chronic Prosthetic Device Infection With Francisella tularensis,” that a patient's interaction with both domesticated and undomesticated animals, field exposure, outdoor activity, and occupation should be considered when diagnosing an infection in a total joint replacement.3
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- Pittman T, Williams D, Friedman AD. A shunt infection caused by Francisella tularensis. Pediatr Neurosurg. 1996;24(1):50–51. doi:10.1159/000121014 [CrossRef]
- Brown VR, Adney DR, Bielefeldt-Ohmann H, et al. Pathogenesis and immune responses of Francisella tularensis strains in wild-caught cottontail rabbits (Sylvilagus spp.). J Wildl Dis. 2015;51(3):564–575. doi:10.7589/2015-02-030 [CrossRef]
- Maurin M, Gyuranecz M. Tularaemia: clinical aspects in Europe. Lancet Infect Dis. 2016;16(1):113–124. doi:10.1016/S1473-3099(15)00355-2 [CrossRef]
- Sjöstedt A. Tularemia: history, epidemiology, pathogen physiology, and clinical manifestations. Ann N Y Acad Sci. 2007;1105(1):1–29. doi:10.1196/annals.1409.009 [CrossRef]
- Parola P, Raoult D. Ticks and tickborne bacterial diseases in humans: an emerging infectious threat. Clin Infect Dis. 2001;32(6):897–928. doi:10.1086/319347 [CrossRef]
- Weiss AP, Krackow KA. Persistent wound drainage after primary total knee arthroplasty. J Arthroplasty. 1993;8(3):285–289. doi:10.1016/S0883-5403(06)80091-4 [CrossRef]
- Saleh K, Olson M, Resig S, et al. Predictors of wound infection in hip and knee joint replacement: results from a 20 year surveillance program. J Orthop Res. 2002;20(3):506–515. doi:10.1016/S0736-0266(01)00153-X [CrossRef]
- Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg. 2007;89(4):780–785.