Debridement, antibiotics and implant retention in early periprosthetic joint infection after primary total hip arthroplasty : 88 percent survival after two years follow-up.

Treatment protocols and results of debridement, antibiotics, irrigation and retention of the prosthesis (DAIR) for early prosthetic joint infection (PJI) vary in literature. The purpose of this study was to analyze the results of DAIR with a multidisciplinary designed customized antibiotic protocol for early PJI after primary total hip replacement (THR). We retrospectively analyzed all patients with an early PJI between 2008 and 2012. When an infection was suspected, debridement of the prosthesis, and -collection of intraoperative cultures, was performed. -Patients were multidisciplinary discussed and treated with an appropriate antibiotic scheme for 12 weeks. Primary outcome was retention of the prosthesis after at least two years follow-up and without any signs of infection. We indentified 25 patients with early PJI. At a median follow-up time of 3.1 years (range 2.1-5.5 years), 88% had retention of the prosthesis and no signs of infection. This study suggests that DAIR with a multidisciplinary approach and an aimed antibiotic treatment for early PJI after THR is a reasonable treatment -option with 88% implant retention after two years follow-up.

Evaluation of infections of the locomotor system with indium-111-labeled human IgG scintigraphy.

UNLABELLED: Indium-111-labeled human nonspecific immunoglobin G (111In-IgG) is one of the newer agents suggested for scintigraphic evaluation of infection and inflammation. In this study, the utility of this agent was studied in routine clinical practice. METHODS: A dose of 75 MBq 111In labeled to 2 mg IgG (MacroScint) was administered intravenously in 226 patients with 232 possible foci of infection or inflammation. Imaging was performed 4, 24 and 48 hr postinjection. The results were verified by culture, obtained either surgically (42%) or via puncture (19%) and long-term clinical and roentgenological follow-up (39%). Follow-up data were used in patients of whom the vast majority had a negative work-up, including negative 111In-IgG scintigraphy. RESULTS: All infected total hip (THA) and total knee arthroplasties, focal osteomyelitis, diabetic foot infections, septic arthritis and soft-tissue infections were detected (61 foci). Only one patient with early, low-grade spondylodiscitis was false negative with 111In-IgG. Since 111In-IgG scintigraphy does not discriminate between infectious and sterile inflammation, careful interpretation is necessary in cementless THA up to 1 yr after insertion, uptake only around the neck of the femoral component of a THA, recent fractures and pseudarthrosis, in which uptake may be caused by sterile inflammation and not by infection (specificity for inflammation 100%, specificity for infection of 77%). CONCLUSION: Indium-111-IgG scintigraphy is a very sensitive tool for detection of infectious bone and joint disease. Moreover, when uptake patterns of 111In-IgG, which are characteristic for sterile inflammation, are excluded, infection can be ruled out with a high degree of certainty.

Scintigraphic evaluation of experimental chronic osteomyelitis.

UNLABELLED: Assessment of disease activity and disease extent in chronic osteomyelitis remains a difficult diagnostic problem. Radiography is not particularly sensitive. Scintigraphic techniques can be more helpful, but the routinely available agents lack specificity (99mTc-methylene diphosphonate [MDP], 67Ga-citrate) or are laborious to prepare (111In-leukocytes). We evaluated the performance of 2 new radiopharmaceuticals, 99mTc-polyethyleneglycol (PEG) liposomes and 99mTc-hydrazinonicotinamide (HYNIC)-immunoglobulin G (IgG), in an experimental model of chronic osteomyelitis. METHODS: Chronic osteomyelitis was induced in rabbits by inserting S. aureus into the right reamed and washed femoral canal. The canal was closed with cement. A sham operation was performed on the left femur. Routine radiographs were obtained immediately after surgery and before scintigraphy. Four weeks after surgery, each rabbit was injected with 37 MBq 99mTc-PEG liposomes, 99mTc-HYNIC-IgG, and 99mTc-MDP on 3 consecutive days and imaged up to 4 (MDP) or 22 (liposomes and IgG) h after injection. On day 4, rabbits received either 18 MBq 111In-granulocytes or 67Ga-citrate and were imaged up to 44 h after injection. Uptake in the infected femur was determined by drawing regions of interest. Ratios of infected-to-sham-operated femur were calculated. After the last image, the rabbits were killed, and the left and right femur were scored for microbiologic and histopathologic evidence of osteomyelitis. RESULTS: 99mTc-PEG liposomes and 99mTc-HYNIC-IgG correctly identified all 6 rabbits with osteomyelitis. 11In-granulocytes and 67Ga-citrate gave equivocal results in 1 infected rabbit. 99mTc-MDP missed 1 case of osteomyelitis. The uptake in the affected region did not differ significantly between the agents, although 99mTc-MDP tended to have higher values (MDP, 4.75 +/- 1.23 percentage injected dose per gram [%ID/g]; 67Ga, 2.05 +/- 0.54 %ID/g; granulocytes, 1.56 +/- 0.83 %ID/g; liposomes, 1.75 +/- 0.76 %ID/g, and IgG, 1.96 +/- 0.27 %ID/g). The ratios of infected-to-normal femur were also not significantly different for the respective radiopharmaceuticals. Radiography visualized only severe osteomyelitis. CONCLUSION: In this rabbit model, 99mTc-PEG liposomes and 99mTc-HYNIC-IgG performed at least as well as 111In-granulocytes and 67Ga-citrate in the localization of chronic osteomyelitis. The ease of preparation, the better image quality, and the lower radiation dose suggest that 99mTc-PEG liposomes and 99mTc-HYNIC-IgG might be suitable alternatives for 67Ga-citrate and 111In-granulocytes in the scintigraphic evaluation of osteomyelitis.

Effects of hydrosyapatite coating on Ti-6A1-4V implant-site infection in a rabbit tibial model.

To investigate the effect of implant type after direct contamination, a hydroxyapatite-coated or noncoated Ti-6A1-4V implant was inserted into both tibiae of 32 New Zealand White rabbits. Prior to implantation, the left tibia was contaminated with increasing concentrations of Staphylococcus aureus (10(2)-10(5) colony-forming units), ranging from very low (10(2)) to relatively high (10(5)). Four weeks after implantation, half of the tibial bone adjacent to the implant was harvested for bacteriological examination. Bacterial counts were quantified by plating serial dilutions. For the histological evaluation, sections of the implant with the remaining tibia were examined by semiquantitative scoring of infection parameters. The bacteriological data showed the inoculum dose and implant type to have a significant effect on the culture outcome: more bacteria were retrieved from the hydroxyapatite-coated implants than from the noncoated titanium implants. Histological evaluation showed an increased score for the infected left tibiae compared with their contralateral control. In addition, with increasing inoculum dosage, the difference between the two types of implant increased. We demonstrated that infections can occur with biocompatible, noncemented implants and that they are related to the dose of the original inoculum. Bacteria were more likely to grow onto or next to the hydroxyapatite implants than on titanium implants and resulted in a more severe histopathological characterization of infection.

Prophylaxis of implant-related staphylococcal infections using tobramycin-containing bone cement.

In a rabbit model, premixed tobramycin-containing bone cement was studied for its efficacy to prevent infections with two frequently encountered staphylococcal species in arthroplasty surgery. After intramedullary inoculation with staphylococci, either standard or premixed tobramycin-containing Simplex-P bone cement was injected in the right femur of 120 rabbits. Development of infection was examined by culture of femoral bone after 7 or 28 days. Loss of body weight and elevated erythrocyte sedimentation rate in the control rabbits inoculated with Staphylococcus aureus were seen in the first postoperative week, returning to normal in 28 days. Inoculation with Staphylococcus epidermidis resulted only in a low-grade infection. All rabbits receiving premixed tobramycin-containing bone cement were free of signs of infection, and all their cultures were negative. Culture yield from Staphylococcus aureus controls increased with time and inoculum dose. Staphylococcus epidermidis controls needed higher inoculum doses to establish an infection, while culture yield decreased in time. These differences in mode of prosthesis-related infection are explained by differences in virulence factors.

Release of tobramycin from tobramycin-containing bone cement in bone and serum of rabbits.

Tobramycin release from tobramycin-containing bone cement was studied in vivo in a rabbit model. After insertion of cement into the right femur, tobramycin concentration as a function of time for up to 28 days was measured in serum and bone of rabbits. Tobramycin release in the femoral cortex adjacent to the cement was found to exceed the minimal inhibitory concentration for Staphylococcus aureus Wood 46. Serum tobramycin concentrations were below the systemic toxicity threshold.

Tobramycin-containing bone cement and systemic cefazolin in a one-stage revision. Treatment of infection in a rabbit model.

The efficacy of tobramycin-containing bone cement with that of systemic cefazolin for treatment of infection in a one-stage revision model is compared. In addition, the value of detecting bacterial DNA after antibiotic treatment was investigated. An implant was inserted into the right tibia of rabbits after inoculation with Staphylococcus aureus. At 28 days, the implant was removed. Subsequently, either plain bone cement with or without systemic administration of cefazolin, or tobramycin-containing bone cement was injected into the medullary canal. The tibiae were cultured 14 days after revision (Day 42), and showed a significant decrease in bacterial counts for both antibiotic groups compared with the control group (p

Prevention of infection with tobramycin-containing bone cement or systemic cefazolin in an animal model.

We investigated in an animal model the efficacy of tobramycin-containing bone cement and systemic cefazolin for infection prophylaxis. In 18 female rabbits, the femoral cavity was inoculated with Staphylococcus aureus before injection of bone cement. The first group of six rabbits received tobramycin-containing Simplex-P bone cement. Two other groups of six rabbits received plain Simplex-P bone cement. Preoperatively, in one of the two latter groups cefazolin was administered intravenously. The other group served as untreated controls. The rabbits were monitored for clinical signs of infection. At 7 days' follow-up, the femora were harvested and cultures from the bone adjacent to the cement plug were quantified. Cultures from the rabbits which received antibiotic prophylaxis (either cefazolin systemically or tobramycin-containing bone cement) were all negative. In contrast, all rabbits in the untreated control group had positive cultures. These rabbits also had other signs of infection such as an elevated erythrocyte sedimentation rate and loss of body weight. Culture results were confirmed by the absence of bacterial DNA in the polymerase chain reaction hybridization assay. In conclusion, we found that both tobramycin-containing bone cement and systemic cefazolin are effective in preventing implant bed infection in rabbits up to 7 days after contamination with S. aureus.

Hip and knee arthroplasty infection. In-111-IgG scintigraphy in 102 cases.

We studied indium-111-labeled immunoglobulin G (In-111-IgG) scintigraphy for evaluation of total hip and knee arthroplasty infection in 100 patients (102 arthroplasties) where infection was suspected (85 total hip and 17 total knee replacements, 23 of which proved to be infected, all but 2 late infections). The sensitivity of In-111-IgG scintigraphy for infection was 1.0, for hip and knee arthroplasties the specificities were 0.8 and 0.5, respectively. False-positive results for infection occurred in cementless total hip arthroplasties up to 14 months after implantation. Aseptic inflammation due to formation of ectopic ossification and foreign-body response, following wear of the polyethylene socket, was responsible for false-positive results. The images should be read in conjunction with radiographs, which reduces the rate of false-positive results. In-111-IgG is a highly sensitive and fairly specific tool for detecting of late infection of total hip and total knee arthroplasties.

Osseointegration of hydroxyapatite-coated and noncoated Ti6Al4V implants in the presence of local infection: a comparative histomorphometrical study in rabbits.

A study was designed to investigate the osseointegration of titanium implants, either noncoated or coated with hydroxyapatite (HA), into rabbit tibiae in the presence of local infection compared with osseointegration in the absence of local infection. HA-coated or noncoated Ti cylinders were implanted into both tibiae of 32 rabbits (New Zealand Whites). Before implantation the left tibia was contaminated with different quantities of Staphylococcus aureus (10(2)-10(5) CFU). Four weeks after surgery the tibiae were explanted and prepared for microbiological and histomorphometrical examination. Histomorphometrical data, as a representation of implant fixation, were obtained by measuring the percentage of bone around the implants (within a radius of 1 mm from the outer diameter of the implants) and the percentage of the circumference of the implant that was in direct contact with bone. Histomorphometry revealed, in particular for the HA implants, a relationship between the inoculum concentration and/or the presence or absence of infection with the bone contact at the distal implant side. This confirms a relationship between peri-implant infection and bone contact or remodeling. HA-coated implants developed, in the presence of bacteria, more easily a more severe infection than noncoated Ti implants, and we show in the present study that local infection will influence histomorphometrical parameters (bone-implant contact) that determine implant fixation. Precautions to prevent contamination (asepsis) and/or infection (perioperative antibiotics) are even more important for the highly biocompatible HA-coated implant.