We retrospectively reviewed all 18 patients (18 knees) treated for reinfection after previous two-stage revision of infected TKA between January 1999 and January 2008. Twelve patients were women and six patients were men. Mean time from the original TKA until the initial revision was 7 months (range, 1.5–13 months) and from revision to rerevision was 5 months (range, 1–18 months). All knees were reinfected with the original organism(s). The infecting organisms included methicillin-resistant Staphylococcus aureus (11 patients, 11 knees), methicillin-resistant Staphylococcus epidermidis (two patients, two knees), methicillin-sensitive S aureus (two patients, two knees), and mixed Proteus mirabilis and Escherichia coli (three patients, three knees). All of the Staphylococcus organisms were sensitive to vancomycin in concentrations of 2 to 5 μg/mL, and the three E coli and P mirabilis organisms were sensitive to gentamicin in concentrations of 2 μg/mL. The minimum followup was 2.3 years (mean, 6.1 years; range, 2.3–12.0 years). No patients were lost to followup. No patients were recalled specifically for this study; all data were obtained from medical records.
We treated all knees with the same protocol that included extensive débridement, revision TKA with uncemented components, and direct antibiotic infusion. Surgical treatment included thorough removal of nonabsorbable sutures, complete synovectomy, and débridement of abscesses and popliteal cysts. Vascularized osteoperiosteal flap osteotomy was used to expose diaphyseal cement mantles that extended into the diaphysis and could not be removed from the open end of the bone, leaving the cement bed directly and completely visible for inspection. We meticulously removed cement using three-phase débridement of the bone surfaces starting with rongeurs followed by curettes and finishing with a high-torque reamer to burr away all surfaces exposed to cement. During débridement, hand-pump irrigation with a saline solution of vancomycin (1 g/L), polymyxin (30,000 U/L), and Bacitracin (50,000 U/L) was performed repeatedly. After the débridement was completed, the area was redraped, the surgical team regowned and gloved, and the instruments were washed and soaked in the same type of antibiotic solution used for irrigation. Tibial tubercle osteotomy was used for exposure in 13 knees. Seventeen knees required bivalve osteotomy of the femur, tibia, or both to expose the cement mantle and débride the endosteal surfaces. Five knees had necrosis of the quadriceps tendon, patella, and patellar tendon and had débridement and removal of a portion of the quadriceps tendon, the entire patella, and the patellar tendon. Seven knees, including all the knees that had patella and patellar tendon resection, had muscle flaps for closure of capsular and soft tissue defects. Novel muscle flaps, including lateral transfer of the vastus medialis and medial transfer of the vastus lateralis, were necessary in seven knees. In two knees, a medial gastrocnemius flap was sutured to the transferred vastus medialis muscle to achieve extensor continuity through the knee. Ten knees (56%) had one-stage revision (Fig. ). Five knees (28%) had débridement, cement spacer, and definitive revision arthroplasty 3 to 4 months later; and three knees (16%) had multiple extensive soft tissue reconstruction including tissue expanders to produce enough skin for closure and external fixators to achieve adequate limb length before their definitive revision arthroplasty. Two of the patients (two knees) required débridement of the edge of a muscle flap and repeat closure within the first week postoperatively. Three patients (three knees) had open drainage of hematoma and reclosure during the first 2 weeks postoperatively. If the bone and soft tissue quality had adequate circulation to sustain healing, and adequate soft tissue was available for closure, then we performed revision TKA using nonporous, fluted, diaphyseal-engaging titanium stems and porous-coated implants applied directly to available bone. No cement was used to fix the implants to bone, and no bone graft was used to fill bone defects. In cases in which bone stock and soft tissue were not deemed adequate for stable fixation of the implants and secure closure of the joint, implants were not inserted, Hickman catheters were inserted for delivery of antibiotics, and closure completed using available skin and muscle flaps, allowing the extremity to shorten if necessary. These patients were managed postoperatively to achieve bone healing of the osteotomies, restore leg length, and gain skin for closure. Three patients (three knees) underwent external fixation for gradual lengthening to regain limb length, and three patients (three knees) had subfascial soft tissue expanders to provide skin for closure. We used a Constavac (Stryker Corp., Kalamazoo, MI, USA) drain for 24 to 48 hours postoperatively, but the blood was not reinfused.
Lateral radiograph performed at 6 weeks after revision with uncemented implants and Hickman catheters for antibiotic infusion. The infection resolved, and the patient has progressed to full weightbearing.
To improve the chances of maintaining intraarticular access for 6 weeks, we inserted two Hickman catheters (CR Bard Inc, Salt Lake City, UT, USA) in all patients. These catheters are silicone tubes with a fibrous cuff that allows fibrous tissue ingrowth to seal the entry point and prevent ingress and egress of fluid around the catheter. The catheters were inserted through the lateral thigh, penetrating the vastus lateralis muscle and entering the suprapatellar area of the knee (Fig. ). The fibrous cuff was placed approximately 5 mm deep to the dermis. We sutured each catheter to the skin surface with silk sutures on two sides, and the injection portals were taped to the surface of the skin. The external portals each were fitted with a Luer lock module and cap to allow injection with a syringe. The junctions were sealed with Betadine ointment. Postoperatively the patients received 1 g vancomycin or 80 mg gentamicin intravenously every 12 hours for at least 48 hours postoperatively. The intravenous antibiotics were discontinued after 48 hours if intraarticular administration was established. Intraarticular infusion of antibiotics began in the evening of the first day after surgery. We administered 100 mg vancomycin or 20 mg gentamicin in 3 mL saline daily as a test dose, and the concentration and volume were increased daily if the wound remained sealed and quiescent. When the wound was stable and dry, the dosage was increased to 500 mg vancomycin or 80 mg gentamycin in 8 mL saline. The dose was given every 12 or 24 hours depending on the patient’s ability to tolerate the antibiotic in the knee. If irritation and redness occurred, we decreased the volume and concentration. The injection was alternated between the two catheters to keep them open. The catheters were not flushed but were capped and clamped to maintain a reliable seal. Vancomycin is unstable in solution and must not be injected in the knee in concentrations greater than 100 mg/mL. To avoid precipitation of the concentration used in the knees, the dosage was limited to 50 mg/mL. Eight milliliters of the solution (500 mg vancomycin or 80 mg gentamicin) was injected once or twice daily for 6 weeks, and the serum peak and trough levels were measured twice weekly. We modified the frequency and dosage to maintain the serum trough levels between 3 and 10 μg/mL for vancomycin and 1 and 2 μg/mL for gentamicin.
Fig. 2 Illustration of the infusion system using Hickman catheters. This drawing illustrates the injection portals (a) that are outside the skin, the fibrous cuffs that are approximately 5 mm deep to the dermis (b), the catheters inside the synovial (more ...)
After 6 weeks of treatment, the Hickman catheters were removed surgically. Six of the 18 knees lost one of the catheters because of occlusion during the 6-week infusion interval. Two patients had removal of one of the two catheters for leakage. One knee had traumatic avulsion of both catheters 8 days after surgery and required general anesthesia to insert new catheters. None of the patients had breakage of the catheters, secondary infection, or chronic drainage or fistula formation from the catheters.
All knees were allowed full weightbearing after their final implants were inserted but were supported with a walker for 4 to 6 weeks. Supervised physical therapy was started the first day after surgery and continued through 6 weeks. Gentle active and passive ROM exercises and quadriceps strengthening were begun and progressed as soon as the patient could cooperate.
The patients were seen at 2 weeks for suture removal, at 6 weeks for removal of the Hickman catheters, and again 2 weeks later for suture removal from the tube site. They returned at 3 months for physical evaluation and radiographs and then at yearly intervals for physical evaluation and radiographs. We evaluated all knees for tenderness, erythema, and induration at 3 months postoperatively. Serum C-reactive protein (CRP) concentration and sedimentation rate were evaluated at 3 months. Because the patients were only 3 months postoperative from their revision surgery and had recently had catheter removal, we considered CRP level less than 25% above normal and sedimentation rate less than 50% elevated signs of resolved infection. Other signs of resolved infection included absence of erythema and tenderness and absence of radiographic signs of bone absorption. After 3 months, no additional laboratory tests were obtained by our office and the patients were followed with CRP and sedimentation rates by their infectious disease consultants. Knee scores were determined using the Knee Society Clinical Rating System [8
To evaluate the quality of the débridement postoperatively, one of us (LAW) evaluated AP, lateral, and skyline patellar radiographs immediately postoperatively and at 1-month and 3-month followup intervals. None had retained cement or debris on their followup radiographs. The same radiographs were scrutinized for evidence of migration or displacement of the bivalve osteotomies and tibial tubercle osteotomy, and fixation was evaluated by appearance of radiolucent lines at every followup visit. We identified and measured radiolucent lines with a ruler accurate to 0.5 mm. The tibial tubercle and fibular head were chosen as landmarks to measure tibial component migration, and the distances from the undersurface of the tibial baseplate to the top of the fibular head and to the tibial tubercle were measured on each radiographic examination. We chose the medial and lateral epicondyles as the femoral bone landmarks for femoral component migration. Femoral component position was measured relative to the femoral bone landmarks by drawing a line that joined the distal surface of the implant and measuring the distance between this line and the medial and lateral epicondyles. We defined radiographic signs of migration as a radiolucent line that increased by more than 1 mm on one side of a diaphyseal stem or greater than 1-mm change in distance relative to one of the bone landmarks on two successive radiographic examinations. We defined a stable arthroplasty as a total knee with no sign of migration of either the femoral or tibial implant over a period of 2 years.