Within- and between-therapist agreement on personalized parameters for robot-assisted gait therapy: the challenge of adjusting robotic assistance.

BACKGROUND: Stationary robotic gait trainers usually allow for adjustment of training parameters, including gait speed, body weight support and robotic assistance, to personalize therapy. Consequently, therapists personalize parameter settings to pursue a relevant therapy goal for each patient. Previous work has shown that the choice of parameters influences the behavior of patients. At the same time, randomized clinical trials usually do not report the applied settings and do not consider them in the interpretation of their results. The choice of adequate parameter settings therefore remains one of the major challenges that therapists face in everyday clinical practice. For therapy to be most effective, personalization should ideally result in repeatable parameter settings for repeatable therapy situations, irrespective of the therapist who adjusts the parameters. This has not yet been investigated. Therefore, the aim of the present study was to investigate the agreement of parameter settings from session to session within a therapist and between two different therapists in children and adolescents undergoing robot-assisted gait training. METHODS AND RESULTS: Fourteen patients walked in the robotic gait trainer Lokomat on 2 days. Two therapists from a pool of 5 therapists independently personalized gait speed, bodyweight support and robotic assistance for a moderately and a vigorously intensive therapy task. There was a very high agreement within and between therapists for the parameters gait speed and bodyweight support, but a substantially lower agreement for robotic assistance. CONCLUSION: These findings imply that therapists perform consistently at setting parameters that have a very clear and visible clinical effect (e.g. walking speed and bodyweight support). However, they have more difficulties with robotic assistance, which has a more ambiguous effect because patients may respond differently to changes. Future work should therefore focus on better understanding patient reactions to changes in robotic assistance and especially on how instructions can be employed to steer these reactions. To improve the agreement, we propose that therapists link their choice of robotic assistance to the individual therapy goals of the patients and closely guide the patients during walking with instructions.

Prospective comparison of diffusion-weighted MRI and dynamic Gd-EOB-DTPA-enhanced MRI for detection and staging of hepatic fibrosis in primary sclerosing cholangitis.

PURPOSE: To assess the diagnostic value of multiparametric magnetic resonance imaging (MRI) including dynamic Gd-EOB-DTPA-enhanced (DCE) and diffusion-weighted (DW) imaging for diagnosis and staging of hepatic fibrosis in primary sclerosing cholangitis (PSC) using transient elastography as a standard reference. MATERIAL AND METHODS: Multiparametric MRI was prospectively performed on a 3.0-Tesla scanner in 47 patients (age 43.9±14.3 years). Transient elastography derived liver stiffness measurements (LSM), DCE-MRI derived parameters (hepatocellular uptake rate (Ki), arterial (Fa), portal venous (Fv) and total (Ft) blood flow, mean transit time (MTT), and extracellular volume (Ve)) and the apparent diffusion coefficient (ADC) were calculated. Correlation and univariate analysis of variance with post hoc pairwise comparison were applied to test for differences between LSM derived fibrosis stages (F0/F1, F2/3, F4). ROC curve analysis was used as a performance measure. RESULTS: Both ADC and Ki correlated significantly with LSM (r= -0.614; p<0.001 and r= -0.368; p=0.01). The ADC significantly discriminated fibrosis stages F0/1 from F2/3 and F4 (p<0.001). Discrimination of F0/1 from F2/3 and F4 reached a sensitivity/specificity of 0.917/0.821 and 0.8/0.929, respectively. Despite significant inter-subject effect for classification of fibrosis stages, post hoc pairwise comparison was not significant for Ki (p>0.096 for F0/1 from F2/3 and F4). LSM, ADC and Ki were significantly associated with serum-based liver functional tests, disease duration and spleen volume. CONCLUSION: DW-MRI provides a higher diagnostic performance for detection of hepatic fibrosis and cirrhosis in PSC patients in comparison to Gd-EOB-DTPA-enhanced DCE-MRI. KEY POINTS: • Both ADC and hepatocellular uptake rate (Ki) correlate significantly with liver stiffness (r= -0.614; p<0.001 and r= -0.368; p=0.01). • The DCE-imaging derived quantitative parameter hepatocellular uptake rate (Ki) fails to discriminate pairwise intergroup differences of hepatic fibrosis (p>0.09). • DWI is preferable to DCE-imaging for discrimination of fibrosis stages F0/1 to F2/3 (p<0.001) and F4 (p<0.001).

Adoptive tumor therapy with T lymphocytes enriched through an IFN-gamma capture assay.

Successful adoptive T-cell therapy has been demonstrated in viral disease and selected forms of cancer. However, it is limited by the difficulty to efficiently isolate and amplify autologous tumor-reactive T-cell clones. Tetramers of major histocompatibility complex (MHC) class I and peptide have facilitated the characterization of CD8+ T cells specific for tumor-associated antigens. However, for adoptive T-cell therapy, MHC-tetramers have limitations: they require knowledge of tumor antigens, which is often not available; they select T cells with a single specificity, thereby posing risk for selection of tumor escape variants; they do not select for function, so that T cells may be anergic when isolated from cancer patients; and they do not allow the isolation of CD4+ T cells that can be essential for tumor rejection. Because interferon (IFN)-gamma is essential for tumor rejection, we isolated live T cells based on their IFN-gamma production. IFN-gamma secreted by previously activated T cells is retained on the cell surface, allowing their specific isolation and expansion. We show here that IFN-gamma+ but not IFN-gamma- T cells from tumor-immunized mice are cytolytic and mediate tumor rejection upon adoptive transfer. Importantly, tumor-specific T cells can be enriched from lymphocytes infiltrating human renal cell carcinoma by the IFN-gamma capture assay.

B cells inhibit induction of T cell-dependent tumor immunity.

Cytotoxic T lymphocyte (CTL) mediated tumor immunity against major histocompatibility antigen (MHC) class I-positive but class II-negative tumors often requires help from CD4+ T cells. These CD4 cells are activated by MHC class II-positive cells that present tumor derived antigens. Considering that different antigen presenting cells, such as B cells, macrophages and dendritic cells compete for antigen and influence the outcome of an immune response, we analyzed tumor immunity in B cell-deficient mice. These mice appear normal with regard to T cell immunity and tolerance to some pure foreign antigens. We show here that the low immunogenicity of tumors is caused by B cells whose presence in the priming phase results in disabled CD4+ T cell help for CTL mediated tumor immunity. Instead, in the presence of B cells, a non-protective humoral immune response is induced. Our results may explain the enigmatic observation that tumor-reactive antibodies occur frequently in cancer patients.

Interleukin 4 gene-defective mice reconstituted with wild-type bone marrow fail to produce normal immunoglobulin E levels.

The ability to reconstitute interleukin (IL)-4-/- mice with bone marrow of IL-4+/+ mice was investigated. The absence of the IL-4-/- gene in donor or recipient cells did not impair the reconstitution. All immunoglobulin (Ig) subsets occurred at normal serum levels except for IgE and to some extent IgG1. IgE production did not recover in the reconstituted mice over prolonged time. However, these mice were competent for IgE production, because a single intrasplenic injection of IL-4 restored IgE levels, which then remained constant. Wild-type mice reconstituted with wild-type bone marrow constantly had IgE serum levels comparable to untreated animals. In wild-type mice reconstituted with IL-4-/- bone marrow, IgE levels dropped gradually and disappeared by week 12. We make three unrelated but nonetheless important conclusions: (a) (immunoregulation) the tightly regulated IL-4 gene should be expressed constantly in low amounts (and with apparent absence of antigen stimulation) to keep the normal threshold of IgE; (b) (ontogeny of the immune system) an early unidentified source of IL-4 must be postulated which is lost in adult mice; and (c) (bone marrow transfer/gene therapy) under certain circumstances, the genotype of the recipient influences the reconstitution.

Tumor rejection by disturbing tumor stroma cell interactions.

The stroma of solid tumors is a complex network of different cell types. We analyzed stroma cell interactions in two tumor models during cyclophosphamide (Cy)-induced tumor rejection. In growing tumors, tumor infiltrating macrophages (TIMs) produced interleukin (IL)-10. Beginning 6 h after Cy-treatment T cells in the tumor were inactivated and TIMs switched to interferon (IFN)-gamma production. Both, IL-10 production before and IFN-gamma production after Cy-treatment by TIMs required T cells. With the same kinetics as TIMs started to produce IFN-gamma the tumor vasculature was destroyed which required IFN-gamma receptor expression on host but not tumor cells. These events preceded hemorrhagic necrosis and residual tumor cell elimination by T cells. Together, T cells regulate the function of TIMs and tumor rejection can be induced by disturbing the stroma network.

T helper cell type 1-associated and cytotoxic T lymphocyte-mediated tumor immunity is impaired in interleukin 4-deficient mice.

It is widely accepted that cellular immune responses are induced by CD4(+) T helper 1 (Th1) cells secreting interleukin (IL)-2 and interferon (IFN)-gamma. Tumor immunity is often mediated by cytotoxic T lymphocytes (CTLs) whose activation is supported by Th1 cytokines. Since IL-4 directs Th2 development and has been shown to inhibit Th1-dominated responses, we assumed that IL-4-deficient (IL-4(-/-)) mice would develop vigorous CTL-mediated tumor immunity compared with IL-4-competent (IL-4(+/+)) mice. Surprisingly, IL-4(-/-) mice were severely impaired to develop tumor immunity to both a mammary adenocarcinoma line and a colon carcinoma line. The lack of tumor immunity in IL-4(-/-) mice was associated with reduced IFN-gamma production, diminished levels of tumor-reactive serum IgG2a, and undetectable CTL activity, indicating a defective Th1 response in the absence of endogenous IL-4. Anti-IL-4 monoclonal antibody blocked tumor immunity in IL-4(+/+) mice when administered at the time of immunization but not at the time of challenge. Additionally, tumor immunity could be induced in IL-4(-/-) mice, if IL-4 was provided by gene-modified cells together with immunizing tumor cells. These results demonstrate that tumor immunity requires IL-4 in the priming phase for the generation of effector cells rather than for their maintenance and exclude secondary, developmental defects in the "knockout" strain. Together, our results demonstrate a novel and previously unanticipated role of IL-4 for the generation of Th1-associated, CTL-mediated tumor immunity.

Generation of tumor-associated cytotoxic T lymphocytes requires interleukin 4 from CD8(+) T cells.

Activation of tumor-associated CD8(+) cytotoxic T lymphocytes (CTLs) often requires antigen representation, e.g., by dendritic cells (DCs), and CD4(+) T cell help. Previously, we showed that CTL-mediated tumor immunity required interleukin 4 (IL-4) during the immunization but not effector phase. To determine the source and target cells of IL-4, we performed adoptive T cell transfers using CD4(+) and CD8(+) T cells from IL-4(-/-) and IL-4R(-/-) mice and analyzed CTL generation. Even though necessary for CTL generation, CD4(+) T cells did not need to express IL-4 or IL-4R. Surprisingly, CTL generation required IL-4 but not IL-4R expression by CD8(+) T cells. As IL-4 (a) was expressed by naive CD8(+) T cells within 24 h after antigen encounter, (b) IL-4 induced DC maturation, and (c) CTL development was impaired in T cell-reconstituted IL-4R(-/-) mice, CD8(+) T cell-derived IL-4 appears to act on DCs. We conclude that CD4(+) and CD8(+) T cells provide different signals for DC activation during CTL generation.

A randomized, double-blind trial to compare shock wave frequencies of 60 and 120 shocks per minute for upper ureteral stones.

PURPOSE: Recent evidence demonstrates that decreasing shock wave frequency from the previous standard of 120 to 60 shocks per minute results in improved fragmentation of stones located within the renal collecting system. We report the first randomized trial to our knowledge to examine the effect of a slower shock wave frequency for shock wave lithotripsy on stones located in the proximal ureter. MATERIALS AND METHODS: A total of 163 patients with a previously untreated radiopaque calculus in the upper ureter measuring at least 5 mm underwent stratified block randomization according to stone size, and shock wave lithotripsy at 60 or 120 shocks per minute. Stone-free status at 3 months was confirmed with noncontrast computerized tomography or a plain abdominal x-ray and ultrasound study. RESULTS: Of the patients 77 were randomized to 60 shocks per minute and 86 were randomized to 120 shocks per minute. The groups were similar in gender, age, body mass index and initial stone area. At 3 months the 60 shocks per minute group had a higher overall stone-free rate (64.9% vs 48.8%, p = 0.039). Significantly fewer shocks were administered to patients treated at 60 shocks per minute (mean 2,680 vs 2,940, p <0.001). However, mean treatment times were longer (44.3 vs 24.5 minutes, p <0.001). Patients treated with 60 shocks per minute required fewer auxiliary procedures (29.9% vs 45.4%) (p = 0.031). CONCLUSIONS: Decreasing the rate of shock wave administration from 120 to 60 shocks per minute results in improved stone-free rates. A slower treatment rate of proximal ureteral stones reduces the need for additional shock wave lithotripsy or more invasive treatments to render patients stone-free, without any increase in morbidity, and with an acceptable increase in treatment time.

Sexual transmission and propagation of SIV and HIV in resting and activated CD4+ T cells.

In sexual transmission of simian immunodeficiency virus, and early and later stages of human immunodeficiency virus-type 1 (HIV-1) infection, both viruses were found to replicate predominantly in CD4(+) T cells at the portal of entry and in lymphoid tissues. Infection was propagated not only in activated and proliferating T cells but also, surprisingly, in resting T cells. The infected proliferating cells correspond to the short-lived population that produces the bulk of HIV-1. Most of the HIV-1-infected resting T cells persisted after antiretroviral therapy. Latently and chronically infected cells that may be derived from this population pose challenges to eradicating infection and developing an effective vaccine.

Image-plate sensitivity to x rays at 2 to 60 keV.

The sensitivity of Fuji SR and MS image plates (IPs) used in x-ray spectrometers on OMEGA and the National Ignition Facility has been measured using two techniques. A set of radioisotopes has been used to constrain image-plate sensitivity between 6 and 60 keV, while a Manson source has been used to expose image plates to x rays at energies between 1.5 and 8 keV. These data have shown variation in sensitivity on the order of 5% for a given IP type and scanner settings. The radioisotope technique has also been used to assess IP fading properties for MS-type plates over long times. IP sensitivity as a function of scanner settings and pixel size has been systematically examined, showing variations of up to a factor of 2 depending on the IP type. Cross-calibration of IP scanners at different facilities is necessary to produce a consistent absolute sensitivity curve spanning the energy range of 2-60 keV.

Molecular interactions of the type 1 human immunodeficiency virus transregulatory protein Tat with N-methyl-d-aspartate receptor subunits.

We investigated the effect of type 1 human immunodeficiency virus (HIV-1) regulatory protein Tat on N-methyl-d-aspartate (NMDA) receptors expressed in Xenopus oocytes by voltage-clamp recording and its role in NMDA-mediated neurotoxicity using cultured rat hippocampal neurons. Tat (0.01-1muM) potentiated NMDA-induced currents of recombinant NMDA receptors. However, in the presence of Zn(2+), the potentiating effect of Tat was much more pronounced, indicating an additional Zn(2+)-related effect on NMDA receptors. Consistently, Tat potentiated currents of the particularly Zn(2+)-sensitive NR1/NR2A NMDA receptor with a higher efficacy, whereas currents from a Zn(2+)-insensitive mutant were only marginally augmented. In addition, chemical-modified Tat, deficient for metal binding, did not reverse Zn(2+)-mediated inhibition of NMDA responses, demonstrating that Tat disinhibits NMDA receptors from Zn(2+)-mediated antagonism by complexing the cation. We therefore investigated the interplay of Tat and Zn(2+) in NMDA-mediated neurotoxicity using cultures of rat hippocampal neurons. Zn(2+) exhibited a prominent rescuing effect when added together with the excitotoxicant NMDA, which could be reverted by the Zn(2+)-chelator tricine. Similar to tricine, Tat enhanced NMDA-mediated neurotoxicity in the presence of neuroprotective Zn(2+) concentrations. Double-staining with antibodies against Tat and the NR1 subunit of the NMDA receptor revealed partial colocalization of the immunoreactivities in membrane patches of hippocampal neurons, supporting the idea of a direct interplay between Tat and glutamatergic transmission. We therefore propose that release of Zn(2+)-mediated inhibition of NMDA receptors by HIV-1 Tat contributes to the neurotoxic effect of glutamate and may participate in the pathogenesis of AIDS-associated dementia.

Expression of Cdcrel-1 (Pnutl1), a gene frequently deleted in velo-cardio-facial syndrome/DiGeorge syndrome.

The murine Cdcrel-1 (Pnutl1) gene belongs to the family of septins, which are thought to be involved in cytokinesis in yeast, Drosophila and vertebrates. Recent studies implicate Cdcrel-1 in the regulation of vesicle transport in neurons of the adult brain. The human homologue, hCDCREL-1 maps to chromosome 22q11.2, a region commonly deleted in patients displaying velo-cardio-facial syndrome (VCFS) or DiGeorge syndrome (DGS). During development, Cdcrel-1 transcripts are expressed from E10.5 on in the nervous system such as the dorsal root ganglia and the cranial ganglia as well as the lateral layer of the neural tube, the area where terminally differentiated neurons are located. Low level expression is found in the mesenchyme of the frontonasal mass and the limb bud mesenchyme of E11.5 and E13.5 murine embryos. At E15.5, expression is detected in the nervous tissue and in the neural layer of the eye. Based on the expression pattern as well as clinical data, Cdcrel-1 may be involved in the etiology of VCFS/DGS.

A true singles list-mode data acquisition system for a small animal PET scanner with independent crystal readout.

We present a unique data acquisition system designed to read out signals from the MADPET-II small animal LSO-APD PET tomograph. The scanner consists of 36 independent detector modules arranged in a dual-radial layer ring (phi 71 mm). Each module contains a 4 x 8 array of optically isolated, 2 x 2 mm LSO crystals, coupled one-to-one to a 32 channel APD. To take full advantage of the detector geometry, signals from each crystal are individually processed without any data reduction. This is realized using custom designed mixed-signal ASICs for analogue signal processing, and FPGAs to control the digitization of analogue signals and subsequent multiplexing. Analogue to digital converters (ADCs) digitize the signal peak height, time to digital converters (TDCs) time stamp each event relative to a system clock and two 32 bit words containing the energy, time and position information for each singles event are multiplexed through three FIFO stages before being written to disk via gigabit Ethernet. Every singles event is processed and stored in list-mode format, and coincidences are sorted post-acquisition in software. The 1152 channel data acquisition system was designed to be able to handle sustained data rates of up to 11 520 000 cps without loss (10 000 cps/channel). The timing resolution of the TDC was measured to be 1 ns FWHM. In addition to describing the data acquisition system, performance measurements made using a 128-channel detector prototype will be presented.

Potential side effects of insect-resistant transgenic plants on arthropod natural enemies.

Engineering genes encoding insecticidal proteins into crop plants offers numerous benefits to agriculture. However, like many conventional insecticides, this new technology has the potential to disrupt natural biological control through both direct and indirect side effects of the plants on the fitness or behaviour of arthropod predators and parasitoids. Interactions between transgenic plants and these beneficial insects are being assessed to avoid incompatibility.

Presentation by scanning electron microscopy of the life cycle of microsporidia of the genus Encephalitozoon.

This paper presents, for the first time, documentation by detailed scanning electron microscopy of the life cycle of microsporidia of the genus Encephalitozoon. Phase 1 is represented by the extracellular phase with mature spores liberated by the rupture of host cells. To infect new cells the spores have to discharge their polar filament. Spores with everted tubes show that these are helically coiled. When the polar tubules have started to penetrate into a host cell they are incomplete in length. The infection of a host cell can also be initiated by a phagocytic process of the extruded polar filament into an invagination channel of the host cell membrane. After the penetration process, the tube length is completed by polar tube protein which passes through the tube in the shape of swellings. A completely discharged polar tube with its tip is also shown. The end of a polar tube is normally hidden in the cytoplasm of the host cell. After completion of the tube length the transfer of the sporoplasm occurs and phase 2 starts. Phase 2 is the proliferative phase, or merogony, with the intracellular development of the parasite that cannot be documented by scanning electron microscopy. The subsequent intracellular phase 3, or sporogony, starts when the meronts transform into sporonts, documented as chain-like structures which subdivide into sporoblasts. The sporoblasts finally transform directly into spores which can be seen in their host cell, forming bubble-like swellings in the cell surface.

Isolation of lactate dehydrogenase-elevating viruses from wild house mice and their biological and molecular characterization.

Lactate dehydrogenase-elevating virus (LDV) was first identified as a contaminant of transplantable mouse tumors that were passaged in laboratory mice. It has been assumed that these LDVs originated from LDVs endemic in wild house mouse populations. In order to test this hypothesis and to explore the relationships between LDVs from wild house mice among each other and to those isolated from laboratory mice, we have isolated LDVs from wild house mice and determined their biological and molecular properties. We have screened for LDV tissues of 243 wild house mice that had been caught in various regions of North, Central and South America between 1985 and 1994. We were able to isolate LDVs from the tissues of four mice, three had been caught in Baltimore, MD and one in Montana. We demonstrate that the phenotypic properties (ability to establish a long-term viremic infection, low immunogenicity of the neutralization epitope, high resistance to antibody neutralization and lack of neuropathogenicity) of the four wild house mouse LDVs are identical to those of the primary LDVs isolated from transplantable tumors (LDV-P and LDV-vx), which are distinct from those of the neuropathogenic LDV-C. Furthermore, ORF 5 and ORF 2 and their protein products (the primary envelope glycoprotein VP-3P, and the minor envelope glycoprotein, respectively) of the wild house mouse LDVs were found to be closely related to those of LDV-P and LDV-vx. The LDVs caught in Baltimore, MD were especially closely related to each other, whereas the LDV isolated in Montana was more distantly related, indicating that it had evolved independently. The ectodomain of VP-3P of all four wild house mouse LDVs, like those of LDV-P and LDV-vx, possess the same three polylactosaminoglycan chains, two of which are lacking in the VP-3P ectodomain of LDV-C. These results further strengthen the conclusion that the three polylactosaminoglycan chains are the primary determinants of the phenotypic properties of LDV-P/vx.

Surgical irrigation with pooled human immunoglobulin G to reduce post-operative spinal implant infection.

A multiple-site, nonlethal rabbit surgical model of spinal implant infection was used to assess the efficacy of a spinal wound lavage to reduce post-operative infection from methicillinresistant Staphylococcus aureus (MRSA). Multiple aqueous lavages of isotonic saline were compared to the same procedure using 1wt% pooled human immunoglobulin G (IgG) applied directly to the surgical implant sites. Visually observed clinically relevant signs of infection (e.g. , swelling, erythema, pus) were supported by bacterial enumeration from multiple biopsied tissue and bone sites post-mortem at 7 and 28 days post-challenge. Clinical signs of infection were significantly reduced in IgG-lavaged infected spinal sites. Bacterial enumeration also exhibited statistically significant reductions in soft tissues, bone and on K-wire spinal implants using IgG lavage compared with saline. Complete healing of all surgical wounds was seen after 28 days, although isolated fibrosed abscesses were observed in autopsied sites treated with both IgG and saline lavages. Local use of IgG wound lavage is proposed as supplementary infection prophylaxis against antibiotic resistant implant-centered or surgical wound infection.

A novel spinal implant infection model in rabbits.

STUDY DESIGN: A new spinal implant model was designed to study device-centered infection with methicillin-resistant Staphylococcus aureus in multiple noncontiguous surgical sites in the lumbar spine region of a rabbit. OBJECTIVE: To develop a multiple-site spinal implant device-centered infection model in rabbits. SUMMARY OF BACKGROUND DATA: Results in many recent studies show that postoperative wound infection after spinal implant surgery and the increase in antibiotic-resistant bacteria are a concern. Anti-infection strategies must be tested in relevant animal models that will lead to appropriate clinical studies. METHODS: Eight anesthetized New Zealand White rabbits underwent completely isolated partial laminectomy and subsequent stainless steel Kirschner wire implantation directly into the transverse processes of vertebrae T13, L3, and L6. The middle sites (L3) were used as sterile control sites, and the outer sites (T13, L6) were challenged with different amounts of methicillin-resistant Staphylococcus aureus. Rabbits were killed after 7 days, and biopsies were performed to provide evidence for device-centered infection. Bacterial growth on the implant surfaces and in surrounding tissues and bone was assayed. RESULTS: Overall device-centered infection was established after 7 days in 100% of the sites challenged with 10(3) colony-forming units methicillin-resistant Staphylococcus aureus or higher. No infection was seen in any of the control sites located between infected vertebrae. Multiple blood and liver samples showed that the separate localized infections did not become systemic after 7 days. CONCLUSIONS: This new animal model demonstrates that multiple biomaterial implants can be evaluated in the same animal and provides a technique for investigating postoperative device-centered infection of the spine. Infection was demonstrated in noncontiguous lumbar sites of the spine, whereas adjacent control sites remained sterile. Because there was no cross contamination or systemic spread of the infection, multiple anti-infection strategies or implant materials can now be tested for efficacy in a single animal to combat dramatic and costly postoperative implant infections.