We present a series of 48 patients with infected total knee replacements managed by the use of articulating cement spacers and short-term parenteral antibiotic therapy in the postoperative period. All patients had microbiological and/or histological confirmation of infection at the first stage of their revision. They all underwent re-implantation and had a mean follow-up of 48.5 months (26 to 85). Infection was successfully eradicated in 42 of the 48 patients (88%). Six had persistent infection which led to recurrence of symptoms and further surgery was successful in eliminating infection in four patients. These rates of success are similar to those of other comparable series. We conclude that protracted courses of intravenous antibiotic treatment may not be necessary in the management of the infected total knee replacement. In addition, we analysed the microbiological, histological and serological results obtained at the time of re-implantation of the definitive prosthesis, but could not identify a single test which alone would accurately predict a successful outcome

Two-stage revision surgery for infected total knee replacement offers the highest rate of success for the elimination of infection. The use of articulating antibiotic-laden cement spacers during the first stage to eradicate infection also allows protection of the soft tissues against excessive scarring and stiffness. We have investigated the effect of cyclical loading of cement spacers on the elution of antibiotics. Femoral and tibial spacers containing vancomycin at a constant concentration and tobramycin of varying concentrations were studied in vitro. The specimens were immersed and loaded cyclically to 250 N, with a flexion excursion of 45°, for 35 000 cycles. The buffered solution was sampled at set intervals and the antibiotic concentration was established so that the elution could be calculated. Unloaded samples were used as a control group for statistical comparison. The elution of tobramycin increased proportionately with its concentration in cement and was significantly higher at all sampling times from five minutes to 1680 minutes in loaded components compared with the control group (p = 0.021 and p = 0.003, respectively). A similar trend was observed with elution of vancomycin, but this failed to reach statistical significance at five, 1320 and 1560 minutes (p = 0.0508, p = 0.067 and p = 0.347, respectively). However, cyclically loaded and control components showed an increased elution of vancomycin with increasing tobramycin concentration in the specimens, despite all components having the same vancomycin concentration. The concentration of tobramycin influences both tobramycin and vancomycin elution from bone cement. Cyclical loading of the cement spacers enhanced the elution of vancomycin and tobramycin

Aims. We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement. Methods. Gentamicin-loaded UHMWPE was prepared using phase-separated compression moulding, and its drug elution kinetics, antibacterial, mechanical, and wear properties were compared with those of conventional gentamicin-loaded bone cement. Results. Gentamicin-loaded UHMWPE tibial components not only eradicated planktonic Staphylococcus aureus, but also prevented colonization of both femoral and tibial components. The proposed spacer possesses far superior mechanical and wear properties when compared with conventional bone cement spacers. Conclusion. The proposed gentamicin-eluting UHMWPE spacer can provide antibacterial efficacy comparable with currently used bone cement spacers, while overcoming their drawbacks. The novel spacer proposed here has the potential to drastically reduce complications associated with currently used bone cement spacers and substantially improve patients’ quality of life during the treatment. Cite this article: Bone Joint J 2020;102-B(6 Supple A):151–157

Introduction. Infection remains as one of the major challenges of total joint surgery. One-stage irrigation, debridement and reimplantation, or two-stage revision surgery with a temporary implantation of antibiotic eluting bone cement spacer followed by reimplantation are two methods often used to treat infected patients with mixed outcomes. Like bone cement, ultra-high molecular weight polyethylene (UHMWPE) can also be used as a carrier for antibiotics. Recently, we demonstrated that vancomycin and rifampin can be delivered from UHMWPE implants at therapeutic levels to eradicate Staphylococcus aureus biofilm in a lupine animal model. There are regulatory challenges in translating these types of combination devices to clinical use. Last year, at this meeting, we presented the preliminary pre-clinical testing for a temporary UHMWPE spacer containing gentamicin sulfate as a first step towards clinical use. Since then, we carried out a survey among the Knee Society membership about their preference for spacer use in two-stage revision surgery and found that 43% prefer to use a CoCr femoral component on an all-poly cemented tibial insert, 22% prefer bone cement spacers molded in the OR, 20% prefer static bone cement spacers, and 14% prefer pre-formed bone cement spacers. We modified our implant design based on the majority's preference for a total knee system, rather than bone cement spacers, in the temporary two-stage approach. In this study, we explored the effect of gentamicin sulfate (GS) elution from UHMWPE/GS tibial inserts on bacterial colonization on CoCr surfaces. Methods. We characterized the gentamicin sulfate (GS) particles with scanning electron microscopy (SEM). We molded UHMWPE/GS powder blends and characterized the morphology using SEM and Energy Dispersive X-Ray Spectroscopy (EDS). We submerged samples of molded UHMWPE/GS in buffered phosphate solution (PBS) at 37°C and quantified the extent of GS elution into PBS with a method described by Gubernator et al. using o-phthaladehyde (OPA) [1]. Under basic conditions, OPA reacts with primary amino groups to form fluorescent complexes. Since gentamicin is the only source of such amino acids in our elution samples, the number of fluorescent complexes formed is directly proportional to the amount of gentamicin in the sample. Using this method, we could quantify gentamicin elution by measuring sample fluorescence post OPA-reaction. We used a plate reader to excite the fluorescent complexes formed in the OPA reaction and measured the resulting emission at wavelengths of 340 nm and 455 nm, respectively. We also quantified the effect of the standard cleaning protocol (heated sonication in alkaline water and alcohol) used to clean UHMWPE implants on subsequent GS elution from UHMWPE/GS samples using the OPA method. We used agar diffusion tests to characterize antibacterial properties of UHMWPE/GS samples after cleaning. For these tests, we collected eluents collected from UHMWPE/GS and gentamicin-impregnated bone cement (BC/GS) following 1, 2, 3, and 4 weeks of elution, and tested against S. aureus (ATCC 12600). We used the “daughter cells” method developed by Bechert et al. to assess anticolonizing properties of UHMWPE/GS [2,3]. We also characterized the colonization of bacteria on CoCr surfaces in the presence of GS eluting from UHMWPE/GS test samples. For this we modified a Pin-on-Disc (PoD) wear tester: An UHMWPE/GS pin and UHMWPE pin (control) articulated against an implant-finish CoCr disc with Tryptic Soy Broth containing S. Aureus as the lubricant. After 18 hrs, we rinsed the articular surfaces of the pin and disc and stamped them onto Agar gel to transfer any adherent bacteria. We incubated the Agar plate overnight such that adherent bacteria proliferated and became visible. Results. SEM characterized the GS particles as hollow spheres (Fig 1a). These formed small groups of agglomerated domains at the virgin resin boundaries of UHMWPE after molding (Fig 1b). Sulfur signature from the EDS analysis identified the agglomerated domains as GS particles (Fig 2). Elution of GS started with an initial burst and was followed by steady elution up to 12 weeks (Fig 3). Cleaning reduced the initial burst GS elution; and the elution remained unchanged after 2 days (Fig 4). The agar diffusion test showed simmilar inhibition zones for the eluents collected from UHMWPE/GS and BC/GS, suggesting that these samples yield similar antibacterial activity against S. aureus (Fig 5). UHMWPE/GS demonstrated pronounced anticolonizing properties, effectively mitigating the proliferation of S. aureus “daughter” cells. Anticolonizing activity of Palacos R+G was not significantly different when compared with UHMWPE/GS. The PoD test showed little-to-no colonization of CoCr surfaces in the presence of UHMWPE/GS pins, indicative of excellent antibacterial properties of UHMWPE/GS against S. aureus. Conclusion. SEM and EDS has allowed us to visualize domains of gentamicin sulfate particles in UHMWPE. Our OPA method has greater precision than traditional agar-well diffusion methods of measuring gentamicin concentration and showed that gentamicin sulfate-loaded UHMWPE elutes at the same rate as Palacos R+G. Pin-on-disc experiments and the daughter cell method both confirmed that these two materials have similar anticolonization abilities. We also found that using the standard cleaning protocol for UHMWPE orthopedic implants decreased the burst of gentamicin eluting from UHMWPE, but after 2 days, it had no effect compared to uncleaned UHMWPE/GS. Finally, we found that UHMWPE/GS can reduce the colonization of bacteria on CoCr. UHMWPE/GS continues to be a promising material for treating PJI. 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This review summarises the opinions and conclusions reached from a symposium on infected total knee replacement (TKR) held at the British Association of Surgery of the Knee (BASK) annual meeting in 2011. The National Joint Registry for England and Wales reported 5082 revision TKRs in 2010, of which 1157 (23%) were caused by infection. The diagnosis of infection beyond the acute post-operative stage relies on the identification of the causative organism by aspiration and analysis of material obtained at arthroscopy. Ideal treatment then involves a two-stage surgical procedure with extensive debridement and washout, followed by antibiotics. An articulating or non-articulating drug-eluting cement spacer is used prior to implantation of the revision prosthesis, guided by the serum level of inflammatory markers. The use of a single-stage revision is gaining popularity and we would advocate its use in certain patients where the causative organism is known, no sinuses are present, the patient is not immunocompromised, and there is no radiological evidence of component loosening or osteitis. It is our opinion that single-stage revision produces high-quality reproducible results and will soon achieve the same widespread acceptance as it does in infected hip arthroplasty

Aims

Fungal periprosthetic joint infections (PJIs) are rare, but their diagnosis and treatment are highly challenging. The purpose of this study was to investigate the clinical outcomes of patients with fungal PJIs treated with two-stage exchange knee arthroplasty combined with prolonged antifungal therapy.

We retrospectively reviewed 30 two-stage revision procedures in 28 patients performed for fungal peri-prosthetic joint infection (PJI) after a primary total knee replacement. Patients were followed for at least two years or until the infection recurred. The mean follow-up for patients who remained free of infection was 4.3 years (2.3 to 6.1). Overall, 17 patients were assessed as American Society of Anesthesiologists grade 3 or 4. The surgical protocol included removal of the infected implant, vigorous debridement and insertion of an articulating cement spacer. This was followed by at least six weeks of antimicrobial treatment and delayed reimplantation in all patients. The mean interval between removal of the prosthesis and reimplantation was 9.5 weeks (6 to 24). After reimplantation, patients took antifungal agents orally for a maximum of six months. Two knees became reinfected at one and two months post-operatively, respectively: one of these subsequently required arthrodesis because of uncontrolled infection. Fungal PJIs can be treated successfully by removal of all infected material, appropriate antimicrobial treatment and delayed reimplantation

Aims

Periprosthetic joint infection (PJI) is a challenging complication of any arthroplasty procedure. We reviewed our use of static antibiotic-loaded cement spacers (ABLCSs) for staged management of PJI where segmental bone loss, ligamentous instability, or soft-tissue defects necessitate a static construct. We reviewed factors contributing to their failure and techniques to avoid these complications when using ABLCSs in this context.

Infection remains as one of the major challenges of total joint surgery. One-stage irrigation, debridement and reimplantation or two-stage revision surgery with a temporary implantation of antibiotic eluting bone cement spacer followed by reimplantation are two methods often used to treat infected patients with mixed outcomes. Like bone cement, ultra-high molecular weight polyethylene (UHMWPE) can also be used as a carrier for antibiotics. Recently, we demonstrated that vancomycin and rifampin can be successfully delivered from UHMWPE implants at therapeutic levels to eradicate Staphylococcus aureus biofilm in a lupine animal model. There are regulatory challenges in translating these types of combination devices in to clinical use. One approach is to follow a stepwise strategy, with the first step of seeking clearance for a temporary UHMWPE spacer containing gentamicin sulfate. In this study, we explored the effect of gentamicin sulfate (GS) content in UHMWPE on GS elution rate and antimicrobial activity against methicillin-sensitive S. aureus(MSSA). We also assessed the effect of spacer fabrication on the activity of gentamicin sulfate. We prepared and consolidated UHMWPE/GS blends in varying concentrations. After consolidation, we fabricated test samples with surface area (350mm2) to volume (300mm3) ratio of 1.2 for elution in 1.5ml phosphate buffered saline at body temperature for up to six months and quantified eluted GS content using liquid chromatography – mass spectrometry (LCMS). We assessed the antibacterial activity of the obtained samples in vitro against various concentrations of MSSA (103–106 CFU/ml). Furthermore, we quantified the probability of bacterial colonization of UHMWPE impregnated with GS compared to GS containing bone cement. We assessed any detectable changes in activity of eluted GS caused by spacer fabrication by screening m/z peaks of GS isomers in mass spectra obtained from LC-MS. Gentamicin sulfate activity was not compromised by the elevated temperature and pressure used during spacer fabrication. Elution rate of GS increased with increasing GS content in the blends studied. At comparable elution rates, the GS-loaded UHMWPE was either equivalent or better in terms of antibacterial and anticolonization properties when compared with gentamicin containing bone cement. GS-impregnated UHMWPE is a promising material for temporary spacers

Aims

Achievement of accurate microbiological diagnosis prior to revision is key to reducing the high rates of persistent infection after revision knee surgery. The effect of change in the microorganism between the first- and second-stage revision of total knee arthroplasty for periprosthetic joint infection (PJI) on the success of management is not clear.

Aims

In cases of severe periprosthetic joint infection (PJI) of the knee, salvage procedures such as knee arthrodesis (KA) or above-knee amputation (AKA) must be considered. As both treatments result in limitations in quality of life (QoL), we aimed to compare outcomes and factors influencing complication rates, mortality, and mobility.

Aims

Endoprosthetic reconstruction with a distal femoral arthroplasty (DFA) can be used to treat distal femoral bone loss from oncological and non-oncological causes. This study reports the short-term implant survivorship, complications, and risk factors for patients who underwent DFA for non-neoplastic indications.

Aims

This study aimed to describe the use of revision knee arthroplasty in Australia and examine changes in lifetime risk over a decade.

Aims

Periprosthetic joint infection (PJI) occurs in approximately 1% to 2% of total knee arthroplasties (TKA) presenting multiple challenges, such as difficulty in diagnosis, technical complexity, and financial costs. Two-stage exchange is the gold standard for treating PJI but emerging evidence suggests 'two-in-one' single-stage revision as an alternative, delivering comparable outcomes, reduced morbidity, and cost-effectiveness. This study investigates five-year results of modified single-stage revision for treatment of PJI following TKA with bone loss.

Aims

One of the main causes of tibial revision surgery for total knee arthroplasty is aseptic loosening. Therefore, stable fixation between the tibial component and the cement, and between the tibial component and the bone, is essential. A factor that could influence the implant stability is the implant design, with its different variations. In an existing implant system, the tibial component was modified by adding cement pockets. The aim of this experimental in vitro study was to investigate whether additional cement pockets on the underside of the tibial component could improve implant stability. The relative motion between implant and bone, the maximum pull-out force, the tibial cement mantle, and a possible path from the bone marrow to the metal-cement interface were determined.

Aims

Our purpose was to describe an unusual series of 21 patients with fungal osteomyelitis after an anterior cruciate ligament reconstruction (ACL-R).

Aims

The integrity of the soft tissue envelope is crucial for successful treatment of infected total knee arthroplasty (TKA). The purpose of this study was to evaluate the rate of limb salvage, infection control, and clinical function following microvascular free flap coverage for salvage of the infected TKA.

Aims

The aim of this study was to assess the effects of transferring patients to a specialized arthroplasty centre between the first and second stages (interstage) of prosthetic joint infection (PJI) of the knee.

Aims

Our objective is to describe our early and mid-term results with the use of a new simple primary knee prosthesis as an articulating spacer in planned two-stage management for infected knee arthroplasty. As a second objective, we compared outcomes between the group with a retained first stage and those with a complete two-stage revision.

Aims

Metaphyseal cones with cemented stems are frequently used in revision total knee arthroplasty (TKA). However, if the diaphysis has been previously violated, the resultant sclerotic canal can impair cemented stem fixation, which is vital for bone ingrowth into the cone, and long-term fixation. We report the outcomes of our solution to this problem, in which impaction grafting and a cemented stem in the diaphysis is combined with an uncemented metaphyseal cone, for revision TKA in patients with severely compromised bone.