Pulsatile Lavage Improves Tibial Cement Penetration and Implant Stability in Medial Unicompartmental Arthroplasty: A Cadaveric Study.

Cemented unicompartmental knee arthroplasty (UKA) shows good survivorship and function. However, implant failure, causing the need for revision, can occur. Aseptic loosening is still among the most common reasons for revision. The purpose of this study was to assess the influence of preimplantation lavage technique on tibial cement penetration depth, tibial cement volume, and load to fracture in the tibial component of mobile-bearing UKA. In 10 pairs of fresh frozen human tibiae, cemented UKA was implanted by an experienced surgeon. Tibial components were then implanted, left and right tibiae were randomly allocated to group A or B. Prior to implantation, irrigation was performed with either syringe lavage or pulsatile jet lavage in a standardized manner. Cement surface was 4170.2 mm2 (3271.6-5497.8 mm2) in the syringe lavage group, whereas the jet lavage group showed 4499.3 mm2 (3354.3-5809.1 mm2); cement volume was significantly higher as well (4143.4 mm3 (2956.6-6198.6 mm3) compared with 5936.9 mm3 (3077.5-8183.1 mm3)). Cement penetration depth was 2.5 mm (1.7-3.2 mm) for the jet lavage, and 1.8 mm (1.2-2.4 mm) for the syringe lavage. The mean fracture load was 4680 N in the jet lavage group and 3800 N in the syringe lavage group (p = 0.001). Subsidence was significantly higher for syringe lavage. This study suggests a correlation of cement penetration depth and cement volume to implant failure in the tibial component of a UKA using a cadaveric model. The type of bone lavage most likely influences these two key parameters.

An optotracer-based antibiotic susceptibility test specifically targeting the biofilm lifestyle of Salmonella.

Antimicrobial resistance is a medical threat of global dimensions. Proper antimicrobial susceptibility testing (AST) for drug development, patient diagnosis and treatment is crucial to counteract ineffective drug use and resistance development. Despite the important role of bacterial biofilms in chronic and device-associated infections, the efficacy of antibiotics is determined using planktonic cultures. To address the need for antibiotics targeting bacteria in the biofilm lifestyle, we here present an optotracing-based biofilm-AST using Salmonella as model. Our non-disruptive method enables real-time recording of the extracellular matrix (ECM) components, providing specific detection of the biofilm lifestyle. Biofilm formation prior to antibiotic challenge can thus be confirmed and pre-treatment data collected. By introducing Kirby-Bauer discs, we performed a broad screen of the effects of antibiotics representing multiple classes, and identified compounds with ECM inhibitory as well as promoting effects. These compounds were further tested in agar-based dose-response biofilm-AST assays. By quantifying the ECM based on the amount of curli, and by visualizing the biofilm size and morphology, we achieved new information directly reflecting the treated biofilm. This verified the efficacy of several antibiotics that were effective in eradicating pre-formed biofilms, and it uncovered intriguing possible resistance mechanisms initiated in response to treatments. By providing deeper insights into the resistances and susceptibilities of microbes, expanded use of the biofilm-AST will contribute to more effective treatments of infections and reduced resistance development.

A semi high-throughput method for real-time monitoring of curli producing Salmonella biofilms on air-solid interfaces.

Biofilms enable bacteria to colonize numerous ecological niches. Bacteria within a biofilm are protected by the extracellular matrix (ECM), of which the fibril-forming amyloid protein curli and polysaccharide cellulose are major components in members of Salmonella, Eschericha and Mycobacterium genus. A shortage of real-time detection methods has limited our understanding of how ECM production contributes to biofilm formation and pathogenicity. Here we present optotracing as a new semi-high throughput method for dynamic monitoring of Salmonella biofilm growth on air-solid interfaces. We show how an optotracer with binding-induced fluorescence acts as a dynamic fluorescent reporter of curli expression during biofilm formation on agar. Using spectrophotometry and microscopic imaging of fluorescence, we analyse in real-time the development of the curli architecture in relation to bacterial cells. With exceptional spatial and temporal precision, this revealed a well-structured, non-uniform distribution of curli organised in distally projecting radial channel patterns. Dynamic monitoring of the biofilm also showed defined regions undergoing different growth phases. ECM structures were found to assemble in regions of late exponential growth phase, suggesting that ECM forms on site after bacteria colonize the surface. As the optotracer biofilm method expedites screening of curli production, providing exceptional spatial-temporal understanding of the surface-associated biofilm lifestyle, this method adds a new technique to further our understanding of bacterial biofilms.

Wear and damage in retrieved humeral inlays of reverse total shoulder arthroplasty-where, how much, and why?

BACKGROUND: Polyethylene (PE) wear and material degradation have been reported as complications in reverse total shoulder replacements (rTSAs). In this regard, scapular notching is associated with more clinical complications. Therefore, the purposes of the study were to quantify the linear and volumetric wear, as a measure for the amount of removed material, and to qualitatively assess the PE damage modes to describe the material degradation in retrieved rTSA humeral PE inlays that contribute to failure of shoulder replacements. Furthermore, this study aimed to evaluate the effect of scapular notching on PE wear and rim damage of the humeral components. METHODS: The total study population of 39 humeral inlays contains 2 cohorts that were used for the damage mode analysis and for the wear analysis, respectively. The extent and presence of wear damage modes in 5 defined zones were assessed by a grading system for all PE joint replacements. For quantitative wear analysis the most frequent design (n = 17) was chosen. Using a coordinate-measuring machine and postprocessing software, volumetric wear measurements for the retrieved humeral PE inlays were undertaken. Furthermore, prerevision radiographs were analyzed for scapular notching. Finally, retrieval findings were correlated with clinical and radiographic data to consider the effect of notching and to identify risk of failures for these prostheses. RESULTS: Damage on the rim of the humeral PE inlays was more frequent and severe than on the intended articulation surface. Irrespective of the damage mode, the inferior rim zone sustained the greatest amount of wear damage followed by the posterior zone. Burnishing, scratching, pitting, and embedded particles are most likely to occur in the articular surface area, whereas surface deformation, abrasion, delamination and gross material degradation are predominantly present in the inferior and posterior rim zones. The retrieved inlays exhibited a mean volumetric wear rate of 296.9 mm³/yr ± 87.0 mm³/yr. However, if the notched and non-notched components were compared, a significant higher volumetric wear rate (296.5 ± 106.1 mm³/yr) was found for the notched components compared to the non-notched group (65.7 ± 7.4 mm³/yr). Generally, there was a significantly greater incidence of damage and greater amount of wear if scapular notching occurred. CONCLUSION: The notched components showed a 5-fold increase in PE wear rate. Therefore, scapular notching has a strong effect on PE damage and wear. If scapular notching can be clinically avoided, the PE wear performance is in a similar magnitude as found for hip and knee replacements.

Can intraoperative measurement of bone quality help in decision making for cementless unicompartmental knee arthroplasty?

BACKGROUND: In uncemented total hip arthroplasty (THA), low bone mineral density (BMD) is associated with aseptic loosening. BMD is usually assessed via dual-energy X-ray absorptiometry (DXA) or quantitative computed tomography, which takes time and exposes patients to radiation. Due to its low risk profile, intraoperative measurement of the trabecular stability might be a useful alternative to DXA. METHODS: In 24 human femora, BMD was analysed using DXA at the femoral necks and the knees. Performing the standard Oxford Unicompartmental Knee Arthroplasty (OUKA) implantation procedure, a wingblade (DensiProbe) coupled to a torque probe was used to evaluate the trabecular peak torque. The standard procedure was modified: before the completion of the central peg drill hole, the DensiProbe was inserted into the pre-drilled hole and then turned until a loss of resistance was achieved. The obtained data was then correlated with BMD at the femoral neck as well as the knee. RESULTS: In all tested regions, a higher peak torque was observed in correlation with a higher BMD. CONCLUSIONS: As demonstrated, the DensiProbe can be a helpful tool to assess the bone quality intraoperatively in OUKA. It can be a valuable decision guidance when faced with choosing between a cemented and a cementless implant. Due to the fact that the central peg hole of the OUKA can be used for the procedure, no additional risk for the patient exists, while the additional work for the surgeon is minimal.

Fretting and Corrosion in Modular Shoulder Arthroplasty: A Retrieval Analysis.

Tribocorrosion in taper junctions of retrieved anatomic shoulder arthroplasty implants was evaluated. A comparison of the tribocorrosion between cobalt-chromium and titanium alloy stems was conducted and the observations were correlated with the individual's clinical data. Adverse effects caused by metal debris and subsequent elevated serum metal ion levels are frequently reported in total hip arthroplasty. In total shoulder arthroplasty, to date only a small number of retrieval analyses are available and even fewer address the issue of tribocorrosion at the taper junctions. A total of 36 retrieved hemiarthroplasties and total shoulder arthroplasties were assessed using the modified Goldberg score. The prevalence of fretting and corrosion was confirmed in this cohort. Titanium stems seem to be more susceptible to damage caused by tribocorrosion than cobalt-chromium stems. Furthermore, stemless designs offered less tribocorrosion at the taper junction than stemmed designs. A weak correlation between time to revision and increased levels of tribocorrosion was seen. Whether or not tribocorrosion can lead to adverse clinical reactions and causes failure of shoulder arthroplasties remains to be examined.