RESUMEN

Effective treatment of orthopedic implant-associated infections (IAIs) remains a clinical challenge. The in vitro and in vivo studies presented herein evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) to titanium implants inoculated with preformed bacterial biofilms of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that combining vancomycin therapy (500 µg/mL) with application of CVCES at -1.75 V (all voltages are with respect to Ag/AgCl unless otherwise stated) for 24 h resulted in 99.98% reduction in the coupon-associated MRSA colony-forming units (CFUs) (3.38 × 103 vs. 2.14 × 107 CFU/mL, p < 0.001) and a 99.97% reduction in the planktonic CFU (4.04 × 104 vs. 1.26 × 108 CFU/mL, p < 0.001) as compared with the no treatment control samples. The in vivo studies utilized a rodent model of MRSA IAIs and showed a combination of vancomycin therapy (150 mg/kg twice daily) with CVCES of -1.75 V for 24 h had significant reductions in the implant associated CFU (1.42 × 101 vs. 1.2 × 106 CFU/mL, p < 0.003) and bone CFU (5.29 × 101 vs. 4.48 × 106 CFU/mL, p < 0.003) as compared with the untreated control animals. Importantly, the combined 24 h CVCES and antibiotic treatments resulted in no implant-associated MRSA CFU enumerated in 83% of the animals (five out of six animals) and no bone-associated MRSA CFU enumerated in 50% of the animals (three out of six animals). Overall, the outcomes of this study have shown that extended duration CVCES therapy is an effective adjunctive therapy to eradicate IAIs.

Asunto(s)

Staphylococcus aureus Resistente a Meticilina , Infecciones Relacionadas con Prótesis , Infecciones Estafilocócicas , Animales , Vancomicina/farmacología , Vancomicina/uso terapéutico , Infecciones Estafilocócicas/tratamiento farmacológico , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Biopelículas , Infecciones Relacionadas con Prótesis/tratamiento farmacológico , Infecciones Relacionadas con Prótesis/microbiología , Estimulación Eléctrica

RESUMEN

BACKGROUND: There are many options for glenosphere baseplate fixation commercially available, yet there is little biomechanical evidence supporting one type of fixation over another. In this study, we compared the biomechanical fixation of a reverse total shoulder glenoid baseplate secured with locking or non-locking peripheral screws. METHODS: Both a non-augmented mini baseplate with full backing support and an augmented baseplate were testing after implantation in solid rigid polyurethane foam. Each baseplate was implanted with a 30 mm central compression screw and four peripheral screws, either locking or non-locking (15 mm anterior/posterior and 30 mm superior/inferior). A 1 Hz cyclic force of 0-750 N was applied at a 60o angle for 5000 cycles. Throughout the test, the displacement of the baseplate was measured using a 3D Digital Image Correlation System. FINDINGS: The amount of migration measured in the both the non-augmented and augment cases shows no significant differences between locking and non-locking cases at the final cycle count (non-augment: 5.66 +/- 2.29 µm vs. 3.71 +/- 1.23 µm; p = 0.095, augment: 15.43 +/- 8.49 µm vs. 12.46 +/- 3.24 µm; p = 0.314). Additionally, the amount of micromotion measured for both sample types shows the same lack of significant difference (non-augment: 10.79 +/- 5.22 µm vs. 10.16 +/- 7.61 µm; p = 0.388, augment: 55.03 +/- 10.13 µm vs. 54.84 +/- 10.65 µm; p = 0.968). INTERPRETATION: The presence of locking versus non-locking peripheral screws does not make a significant difference on the overall stability of a glenoid baseplate, in both a no defect case with a non-augmented baseplate and a bone defect case with an augmented baseplate.

Asunto(s)

Artroplastía de Reemplazo de Hombro , Articulación del Hombro , Fenómenos Biomecánicos , Tornillos Óseos , Humanos , Escápula/cirugía , Articulación del Hombro/cirugía

RESUMEN

The mechanical stability and long-term success of an implant depends on the early healing phase and osseointegration of the bone around it. In addition, a healthy gingival tissue around the implant acts as a barrier that prevents bacteria and pathological byproducts from reaching the implant site. This study investigated the in-vitro attachment and spreading of human gingival fibroblasts (HGF) on bacterial grade polystyrene (PS) at different distances from radio-frequency glow-discharge (RFGD)-treated commercially pure titanium (cpTi) specimens. Controls included sterile cpTi specimens without RFGD treatment. A second set of experiments utilized media transferred to new bacterial grade polystyrene dishes (no cpTi) after the medium was conditioned by exposure to cpTi, either with or without RFGD treatment, for 24 hr. Surface characterization of the dishes was conducted through contact angle measurements and infrared spectroscopy. Cell numbers and surface areas were determined from Image J analysis of multiple microscopic images of fixed, stained cells. The results showed significantly greater numbers and surface areas on bacterial grade PS dishes at distances up to 15 mm from the RFGD-treated cpTi groups than for the controls. Moreover, a significant effect of the conditioned medium from RFGD-treated cpTi versus control cultures was shown on the numbers of fibroblasts attached to bacterial grade polystyrene dishes after 24 hr (p < 0.005) and 48 hr (p = 0.002) incubation. Surface areas of cells exposed to conditioned medium were not significantly different (p ≥ 0.05). Surface characterization of the PS dishes showed a higher value of the critical surface tensions of the treated group when compared to the control group.

Asunto(s)

Fibroblastos/metabolismo , Encía/metabolismo , Ondas de Radio , Titanio/química , Humanos

RESUMEN

BACKGROUND: Glenoid bone loss is commonly encountered in cases of rotator cuff tear arthropathy and can create challenges during reverse shoulder arthroplasty. In this study, we sought to investigate the biomechanical properties of a new treatment option for superior glenoid defect, an augmented reverse total shoulder baseplate. METHODS: Three conditions were examined: non-augmented baseplate without defect, non-augmented baseplate with defect, and augmented baseplate with defect. The augmented baseplates included a 30-degree half wedge which also matched the created superior defect. The samples were cyclically loaded at a 60° simulated abduction angle to mimic baseplate loosening. The migration and micromotion of the baseplate were measured on the superior edge using a 3D Digital Image Correlation System. RESULTS: The migration measured in the augmented baseplate showed no significant difference when compared to the no defect or defect cases. In terms of micromotion, the augmented baseplate showed values that were between the micromotions reported for the no defect and defect conditions, but not by a statistically significant amount. CONCLUSION: This study provides biomechanical evidence that augmented baseplates can reduce the amount of micromotion experienced by the RSA construct in the presence of significant superior glenoid bone deficiency, but do not fully restore stability to that of a full contact non-augmented baseplate.

RESUMEN

Osseointegrated (OI) prosthetic limbs have been shown to provide an advantageous treatment option for amputees. In order for the OI prosthesis to be successful, the titanium implant must rapidly achieve and maintain proper integration with the bone tissue and remain free of infection. Electrochemical methods can be utilized to control and/or monitor the interfacial microenvironment where the titanium implant interacts with the biological system (host bone tissue or bacteria). This review will summarize the current understanding of how electrochemical modalities can influence bone tissue and bacteria with specific emphasis on applications where the metallic prosthesis itself can be utilized directly as a stimulating electrode for enhanced osseointegration and infection control. In addition, a summary of electrochemical impedance sensing techniques that could be used to potentially assess osseointegration and infection status of the metallic prosthesis is presented.

RESUMEN

Periprosthetic joint infection (PJI) develops clinically, even with antibiotic treatment, and methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are predominant causes of these infections. Due to biofilm formation, antibiotic treatment for patients with PJI can perpetuate resistance, further complicating the use of noninvasive treatments. This study evaluated cathodic-voltage-controlled electrical stimulation (CVCES) of titanium, in combination with a clinically relevant antibiotic, to synergistically prevent MRSA and P. aeruginosa PJIs by inhibiting bacterial adherence or as a treatment for eradicating established biofilms. CVCES of -1.0 V, -1.5 V, or -1.8 V (versus Ag/AgCl), with or without vancomycin for MRSA or gentamicin for P. aeruginosa, was applied to sterile titanium incubated with cultures to evaluate prevention of attachment or eradication of preestablished biofilms. Treatments were 24 h long and included open-circuit potential controls, antibiotic alone, CVCES, and CVCES plus antibiotic. Biofilm-associated and planktonic CFU were enumerated. In general, CVCES at -1.8 V alone or with antibiotic completely eradicated biofilm-associated CFU for both strains, and these parameters were also highly effective against planktonic bacteria, resulting in a >6-log reduction in MRSA and no detectable planktonic P. aeruginosa All CFU were reduced ∼3 to 5 logs from controls for prevention CVCES plus antibiotics at -1.0 V and -1.5 V against MRSA. Remarkably, there were no detectable P. aeruginosa CFU following prevention CVCES at -1.0 V or -1.5 V with gentamicin. Our results suggest that CVCES in combination with antibiotics may be an effective approach for prevention and treatment of PJI.IMPORTANCE Periprosthetic joint infections (PJIs) develop clinically in the presence of antibiotic therapies and are responsible for increased patient morbidity and rising health care costs. Many of these infections involve bacterial biofilm formation on orthopedic hardware, and it has been well established that these biofilms are refractory to most antibiotic treatments. Recent studies have focused on novel methods to prevent and eradicate infection. Cathodic-voltage-controlled electrical stimulation (CVCES) has previously been shown to be effective as a method for prevention and eradication of Gram-positive and Gram-negative infections. The present study revealed that the utility of CVCES for prevention and eradication of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa is enhanced in the presence of clinically relevant antibiotics. The synergistic effects of CVCES and antibiotics are effective in a magnitude-dependent manner. The results of this study indicate a promising alternative method to current PJI mitigation techniques.

Asunto(s)

Antibacterianos/farmacología , Biopelículas/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Pseudomonas aeruginosa/efectos de los fármacos , Titanio/química , Adhesión Bacteriana/efectos de los fármacos , Estimulación Eléctrica , Electrodos , Humanos , Infecciones Relacionadas con Prótesis/tratamiento farmacológico , Infecciones Relacionadas con Prótesis/prevención & control , Infecciones por Pseudomonas/tratamiento farmacológico , Infecciones por Pseudomonas/prevención & control , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/prevención & control , Células Madre , Titanio/uso terapéutico

RESUMEN

Magnesium alloys hold great promise for developing orthopedic implants that are biocompatible, biodegradable, and mechanically similar to bone tissue. This study evaluated the in vitro and in vivo antimicrobial properties of magnesium-9%aluminum-1%zinc (AZ91) and commercially pure titanium (cpTi) against Acinetobacter baumannii (Ab307). The in vitro results showed that as compared to cpTi, incubation with AZ91 significantly reduced both the planktonic (cpTi = 3.45e8, AZ91 = 8.97e7, p < 0.001) colony forming units (CFU) and biofilm-associated (cpTi = 3.89e8, AZ91 = 1.78e7, p = 0.01) CFU of Ab307. However, in vivo results showed no significant differences in the CFU enumerated from the cpTi and AZ91 implants following a 1-week implantation in an established rodent model of Ab307 implant associated infection (cpTi = 5.23e3, AZ91 = 2.46e3, p = 0.29). It is proposed that the in vitro results were associated with an increased pH in the bacterial culture as a result of the AZ91 corrosion process. The robust in vivo buffering capacity likely diminished this corrosion associated pH antimicrobial effect. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 221-227, 2018.

Asunto(s)

Acinetobacter baumannii/crecimiento & desarrollo , Aleaciones/farmacología , Antiinfecciosos/farmacología , Implantes Experimentales/microbiología , Magnesio/farmacología , Aleaciones/química , Animales , Antiinfecciosos/química , Ratas , Ratas Long-Evans

RESUMEN

Three Mg alloys, Mg-1.34% Ca-3% Zn (MCZ), Mg-1.34% Ca-3% Zn-0.2% Sr (MCZS), and Mg-2% Sr (MS), were examined to understand their bio-corrosion behavior. Electrochemical impedance spectroscopy and polarization scans were performed after 6 days of immersion in cell culture medium, and ion release and changes in media pH were tracked over a 28 day time period. Scanning electron microscopy (SEM) of alloy microstructure was performed to help interpret the results of the electrochemical testing. Results indicate that corrosion resistance of the alloys is as follows: MCZ > MCZS > MS.

RESUMEN

BACKGROUND: Superior wear of the glenoid bone is common in patients with rotator cuff arthropathy. This can become a treatment challenge for patients who require shoulder arthroplasty. In reverse shoulder arthroplasty (RSA), glenoid bone loss may affect the stability of baseplate fixation. The primary purpose of this biomechanical laboratory study was to assess the initial fixation stability of RSA glenosphere baseplates in the presence of variable amounts of superior glenoid bone loss. MATERIALS AND METHODS: High-density solid rigid polyurethane foam (30 pounds/cubic foot) was machined to model the glenoid with variable superior defects that provided different levels of support (100%, 90%, 75%, and 50%) for the glenosphere baseplate. The samples were cyclically loaded (0-750 N at 1 Hz for 5000 cycles) at a 60° glenohumeral angle. The micromotion and migration of the baseplate were calculated from displacement data captured during the loading tests with an array of 3 linear variable differential transformers mounted around the baseplate. RESULTS: Micromotion was significantly greater in samples with 50% defects compared with those with smaller defects. Migration was significantly greater after testing for all defect sizes. CONCLUSIONS: Initial fixation of RSA glenosphere baseplates was significantly reduced in models with 50% bone loss on the superior edge compared with models with less bone loss in this high-density bone foam model.

Asunto(s)

Artroplastía de Reemplazo de Hombro , Inestabilidad de la Articulación/prevención & control , Escápula/patología , Fenómenos Biomecánicos , Humanos , Modelos Biológicos , Manguito de los Rotadores/cirugía , Escápula/cirugía , Prótesis de Hombro

RESUMEN

Antibiotic resistance of bacterial biofilms limits available treatment methods for implant-associated orthopaedic infections. This study evaluated the effects of applying cathodic voltage-controlled electrical stimulations (CVCES) of -1.5V and -1.8V (vs. Ag/AgCl) to coupons of commercially pure titanium (cpTi) incubated in cultures of methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii (A. baumannii) as a method of preventing bacterial attachment. Stimulations were applied for 2, 4, and 8h and coupon-associated and planktonic colony-forming units (CFU) were enumerated following stimulation. Compared to open circuit potential (OCP) controls, CVCES for 4h at -1.8V significantly reduced coupon-associated MRSA CFU by 99.9% (1.30×104vs. 4.45×107, p=0.047) and A. baumannii coupon-associated CFU by 99.9% (1.64×104vs. 5.93×107, p=0.001) and reduced planktonic CFU below detectable levels for both strains. CVCES at -1.8V for 8h also reduced coupon-associated and planktonic CFU below detectable levels for each strain. CVCES at -1.5V for 4 and 8h, and -1.8V for 2h did not result in clinically relevant reductions. For 4 and 8h stimulations, the current density was significantly higher for -1.8V than -1.5V, an effect directly related to the rate of water and oxygen reduction on the cpTi surface. This significantly increased the pH, a suspected influence in decreased CFU viability. The voltage-dependent electrochemical properties of cpTi likely contribute to the observed antimicrobial effects of CVCES. This study revealed that CVCES of titanium could prevent coupon-associated and planktonic CFU of Gram-positive MRSA and Gram-negative A. baumannii from reaching detectable levels in a magnitude-dependent and time-dependent manner. STATEMENT OF SIGNIFICANCE: Periprosthetic joint infection is a devastating outcome of total joint arthroplasty and has led to increased patient morbidity and rising healthcare costs. Current treatments are limited by the growing prevalence of antimicrobial resistant biofilms. Therefore, there is a growing interest in the prevention of bacterial colonization of implants. Previous work has shown that cathodic voltage-controlled electrical stimulation (CVCES) of titanium is effective both in vitro and in vivo as an antimicrobial strategy to eradicate established implant-associated biofilm infections. The present study revealed that CVCES of titanium coupons also has utility in preventing coupon-associated and planktonic colony-forming units of Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative Acinetobacter baumannii from reaching detectable levels in a magnitude-dependent and time-dependent manner.

Asunto(s)

Infecciones por Acinetobacter/prevención & control , Acinetobacter baumannii/fisiología , Biopelículas/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/fisiología , Infecciones Estafilocócicas/prevención & control , Titanio/farmacología , Infecciones por Acinetobacter/microbiología , Acinetobacter baumannii/efectos de los fármacos , Acinetobacter baumannii/crecimiento & desarrollo , Recuento de Colonia Microbiana , Estimulación Eléctrica , Electricidad , Técnicas Electroquímicas , Electrodos , Concentración de Iones de Hidrógeno , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Staphylococcus aureus Resistente a Meticilina/crecimiento & desarrollo , Infecciones Estafilocócicas/microbiología

RESUMEN

Stainless steel alloys, including 316L, find use in orthopaedics, commonly as fracture fixation devices. Invasive procedures involved in the placement of these devices will provoke a local inflammatory response that produces hydrogen peroxide (H2O2) and an acidic environment surrounding the implant. This study assessed the influence of a simulated inflammatory response on the corrosion of 316L stainless steel. Samples were immersed in an electrolyte representing either normal or inflammatory physiological conditions. After 24h of exposure, electrochemical impedance spectroscopy (EIS) and inductively coupled plasma mass spectroscopy (ICPMS) were used to evaluate differences in corrosion behavior and ion release induced by the inflammatory conditions. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) were used to evaluate surface morphology and corrosion products formed on the sample surface. Inflammatory conditions, involving the presence of H2O2 and an acidic pH, significantly alter the corrosion processes of 316L stainless steel, promoting aggressive and localized corrosion. It is demonstrated that particular consideration should be given to 316L stainless steel implants with crevice susceptible areas (ex. screw-head/plate interface), as those areas may have an increased probability of rapid and aggressive corrosion when exposed to inflammatory conditions.

Asunto(s)

Peróxido de Hidrógeno/metabolismo , Modelos Biológicos , Acero Inoxidable/efectos adversos , Animales , Corrosión , Humanos , Inflamación/inducido químicamente , Inflamación/metabolismo , Inflamación/patología , Acero Inoxidable/química

RESUMEN

BACKGROUND: Cathodic voltage-controlled electrical stimulation (CVCES) of titanium implants, either alone or combined with a short course of vancomycin, has previously been shown to reduce the bone and implant bacterial burden in a rodent model of methicillin-resistant Staphylococcus aureus (MRSA) implant-associated infection (IAI). Clinically, the goal is to achieve complete eradication of the IAI; therefore, the rationale for the present study was to evaluate the antimicrobial effects of combining CVCES with prolonged antibiotic therapy with the goal of decreasing the colony-forming units (CFUs) to undetectable levels. QUESTIONS/PURPOSES: (1) In an animal MRSA IAI model, does combining CVCES with prolonged vancomycin therapy decrease bacteria burden on the implant and surrounding bone to undetectable levels? (2) When used with prolonged vancomycin therapy, are two CVCES treatments more effective than one? (3) What are the longer term histologic effects (inflammation and granulation tissue) of CVCES on the surrounding tissue? METHODS: Twenty adult male Long-Evans rats with surgically placed shoulder titanium implants were infected with a clinical strain of MRSA (NRS70). One week after infection, the rats were randomly divided into four groups of five: (1) VANCO: only vancomycin treatment (150 mg/kg, subcutaneous, twice daily for 5 weeks); (2) VANCO + 1STIM: vancomycin treatment (same as the VANCO group) coupled with one CVCES treatment (-1.8 V for 1 hour on postoperative day [POD] 7); (3) VANCO + 2STIM: vancomycin treatment (same as the VANCO group) coupled with two CVCES treatments (-1.8 V for 1 hour on POD 7 and POD 21); or (4) CONT: no treatment. On POD 42, the implant, bone, and peripheral blood were collected for CFU enumeration and histological analysis, where we compared CFU/mL on the implants and bone among the groups. A pathologist, blinded to the experimental conditions, performed a semiquantitative analysis of inflammation and granulation tissue present in serial sections of the humeral head for animals in each experimental group. RESULTS: The VANCO + 1STIM decreased the implant bacterial burden (median = 0, range = 0-10 CFU/mL) when compared with CONT (median = 5.7 × 10(4), range = 4.0 × 10(3)-8.0 × 10(5) CFU/mL; difference of medians = -5.6 × 10(4); p < 0.001) and VANCO (median = 4.9 × 10(3), range = 9.0 × 10(2)-2.1 × 10(4) CFU/mL; difference of medians = -4.9 × 10(3); p < 0.001). The VANCO + 1STIM decreased the bone bacterial burden (median = 0, range = 0-0 CFU/mL) when compared with CONT (median = 1.3 × 10(2), range = 0-9.4 × 10(2) CFU/mL; difference of medians = -1.3 × 10(2); p < 0.001) but was not different from VANCO (median = 0, range = 0-1.3 × 10(2) CFU/mL; difference of medians = 0; p = 0.210). The VANCO + 2STIM group had implant CFU (median = 0, range = 0-8.0 × 10(1) CFU/mL) and bone CFU (median = 0, range = 0-2.0 × 10(1) CFU/mL) that were not different from the VANCO + 1STIM treatment group implant CFU (median = 0, range = 0-10 CFU/mL; difference of medians = 0; p = 0.334) and bone CFU (median = 0, range = 0-0 CFU/mL; difference of medians = 0; p = 0.473). The histological analysis showed no deleterious effects on the surrounding tissue as a result of the treatments. CONCLUSIONS: Using CVCES in combination with prolonged vancomycin resulted in decreased MRSA bacterial burden, and it may be beneficial in treating biofilm-related implant infections. CLINICAL RELEVANCE: CVCES combined with clinically relevant lengths of vancomycin therapy may be a treatment option for IAI and allow for component retention in certain clinical scenarios. However, more animal research and human trials confirming the efficacy of this approach are needed before such a clinical recommendation could be made.

Asunto(s)

Antibacterianos/administración & dosificación , Terapia por Estimulación Eléctrica/métodos , Húmero/cirugía , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Diseño de Prótesis , Infecciones Relacionadas con Prótesis/tratamiento farmacológico , Infecciones Estafilocócicas/tratamiento farmacológico , Titanio , Vancomicina/administración & dosificación , Animales , Carga Bacteriana/efectos de los fármacos , Terapia Combinada , Modelos Animales de Enfermedad , Esquema de Medicación , Terapia por Estimulación Eléctrica/instrumentación , Electrodos , Húmero/microbiología , Masculino , Staphylococcus aureus Resistente a Meticilina/crecimiento & desarrollo , Infecciones Relacionadas con Prótesis/diagnóstico , Infecciones Relacionadas con Prótesis/microbiología , Ratas Long-Evans , Infecciones Estafilocócicas/diagnóstico , Infecciones Estafilocócicas/microbiología , Factores de Tiempo

RESUMEN

This study investigated the corrosion of artificially aged T6 heat-treated Mg-9%Al-1%Zn (AZ91) for biomedical applications. Corrosion tests and surface analysis were completed both with and without a monolayer of mouse preosteoblast MC3T3-E1 cells cultured on the sample. Electrochemical impedance spectroscopy (EIS) and inductively coupled plasma mass spectroscopy (ICPMS) were used to explore the corrosion processes after either 3 or 21 days of AZ91 incubation in cell culture medium (CCM). The EIS showed both the inner layer resistance (Rin ) and outer layer resistance (Rout ) were lower for samples without cells cultured on the surface at 3 days (Rin = 2.64 e4 Ω/cm(2) , Rout = 140 Ω/cm(2) ) compared to 21 days (Rin = 3.60 e4 Ω/cm(2) , Rout = 287 Ω/cm(2) ) due to precipitation of magnesium and calcium phosphates over time. Samples with preosteoblasts cultured on the surface had a slower initial corrosion (3 day, Rin = 1.88 e5 Ω/cm(2) , Rout = 1060 Ω/cm(2) ) which was observed to increase over time (21 day, Rin = 2.99 e4 Ω/cm(2) , Rout = 287 Ω/cm(2) ). Changes in the corrosion processes were thought to be related to changes in the coverage provided by the cell layer. Our results reveal that the presence of cells and biological processes are able to significantly influence the corrosion rate of AZ91.

Asunto(s)

Aleaciones , Aluminio , Magnesio , Osteoblastos/metabolismo , Gases em Plasma , Zinc , Aleaciones/química , Aleaciones/farmacología , Aluminio/química , Aluminio/farmacología , Animales , Línea Celular , Corrosión , Magnesio/química , Magnesio/farmacología , Ensayo de Materiales , Ratones , Osteoblastos/citología , Zinc/química , Zinc/farmacología

RESUMEN

Magnesium (Mg) and its alloys, including Mg-9%Al-1%Zn (AZ91), are biodegradable metals with potential use as temporary orthopedic implants. Invasive orthopedic procedures can provoke an inflammatory response that produces hydrogen peroxide (H2O2) and an acidic environment near the implant. This study assessed the influence of inflammation on both the corrosion and mechanical properties of AZ91. The AZ91 samples in the inflammatory protocol were immersed for three days in a complex biologically relevant electrolyte (AMEM culture media) that contained serum proteins (FBS), 150 mM of H2O2, and was titrated to a pH of 5. The control protocol immersed AZ91 samples in the same biologically relevant electrolyte (AMEM & FBS) but without H2O2 and the acid titration. After 3 days all samples were switched into fresh AMEM & FBS for an additional 3-day immersion. During the initial immersion, inflammatory protocol samples showed increased corrosion rate determined by mass loss testing, increased Mg and Al ion released to solution, and a completely corroded surface morphology as compared to the control protocol. Although corrosion in both protocols slowed once the test electrolyte solution was replaced at 3 days, the samples originally exposed to the simulated inflammatory conditions continued to display enhanced corrosion rates as compared to the control protocol. These lingering effects may indicate the initial inflammatory corrosion processes modified components of the surface oxide and corrosion film or initiated aggressive localized processes that subsequently left the interface more vulnerable to continued enhanced corrosion. The electrochemical properties of the interfaces were also evaluated by EIS, which found that the corrosion characteristics of the AZ91 samples were potentially influenced by the role of intermediate adsorption layer processes. The increased corrosion observed for the inflammatory protocol did not affect the flexural mechanical properties of the AZ91 at any time point assessed.

Asunto(s)

Aleaciones/química , Materiales Biocompatibles Revestidos/química , Técnicas Electroquímicas/métodos , Inflamación/metabolismo , Magnesio/química , Corrosión , Peróxido de Hidrógeno/química

RESUMEN

This study explored how periodic cathodic polarization of commercially pure titanium (cpTi) alters its electrochemical properties and biocompatibility. MC3T3-E1 preosteoblast cells were cultured directly on cpTi samples and maintained at open circuit potential (OCP) for 24 h followed by an additional 24-h sequence of periodic cathodic polarization to -1000 or -750 mV (vs. Ag/AgCl) for 1 s followed by a 5-s recovery at OCP. Control experiments were performed where the samples were maintained at OCP throughout the entire test. Subsequent electrochemical impedance spectroscopy revealed both of the periodic cathodic polarization conditions significantly reduced the polarization resistance (Rp ), while only the -1000 mV condition significantly increased the capacitance (C) as compared to the controls. Scanning electron micrographs showed that the cells were fragmented and balled up on the samples periodically shifted to -1000 mV as compared to the cells that were well spread on the controls and samples periodically shifted to -750 mV. Additionally, live/dead fluorescence microscopy revealed that periodic polarizations to -1000 mV reduced cell viability to around 12% as compared to the greater than 95% cell viability observed on the controls and samples periodically polarized to -750 mV. This work showed that periodic cathodic potential shifts can notably alter the electrochemical behavior of cpTi and the viability and morphology of cells seeded directly onto its surface. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1591-1601, 2016.

Asunto(s)

Técnicas Electroquímicas , Ensayo de Materiales , Osteoblastos/metabolismo , Titanio , Animales , Línea Celular , Electrodos , Ratones , Osteoblastos/citología , Titanio/química , Titanio/farmacología

RESUMEN

BACKGROUND: Effective treatments for implant-associated infections are often lacking. Cathodic voltage-controlled electrical stimulation has shown potential as a treatment of implant-associated infections of methicillin-resistant Staphylococcus aureus (MRSA). QUESTIONS/PURPOSES: The primary purpose of this study was to (1) determine if cathodic voltage-controlled electrical stimulation combined with vancomycin therapy is more effective at reducing the MRSA bacterial burden on the implant, bone, and synovial fluid in comparison to either treatment alone or no treatment controls. We also sought to (2) evaluate the histologic effects of the various treatments on the surrounding bone; and to (3) determine if the cathodic voltage-controlled electrical stimulation treatment had an effect on the mechanical properties of the titanium implant as a result of possible hydrogen embrittlement. METHODS: Thirty-two adult male Long-Evans rats (Harlan Laboratories, Indianapolis, IN, USA) with surgically placed shoulder titanium implants were infected with a clinical strain of MRSA (NRS70). One week after infection, eight animals received a treatment of cathodic voltage-controlled electrical stimulation at -1.8 V versus Ag/AgCl for 1 hour (STIM), eight received vancomycin twice daily for 1 week (VANCO), eight received the cathodic voltage-controlled electrical stimulation and vancomycin therapy combined (STIM + VANCO), and eight served as controls with no treatment (CONT). Two weeks after initial infection, the implant, bone, and synovial fluid were collected for colony-forming unit (CFU) enumeration, qualitative histological analysis by a pathologist blinded to the treatments each animal received, and implant three-point bend testing. RESULTS: The implant-associated CFU enumerated from the STIM + VANCO (mean, 3.7 × 10(3); SD, 6.3 × 10(3)) group were less than those from the CONT (mean, 1.3 × 10(6); SD, 2.8 × 10(6); 95% confidence interval [CI] of difference, -4.3 × 10(5) to -9.9 × 10(3); p < 0.001), STIM (mean, 1.4 × 10(6); SD, 2.0 × 10(6); 95% CI of difference, -2.1 × 10(6) to -1.8 × 10(3); p = 0.002), and VANCO (mean, 5.8 x 10(4); SD, 5.7 × 10(4); 95% CI of difference, -6.4 × 10(4) to -1.7 × 10(4); p < 0.001) group. The bone-associated CFU enumerated from the STIM + VANCO group (6.3 × 10(1); SD, 1.1 × 10(2)) were less than those from the CONT (mean, 2.8 × 10(5); SD, 4.8 × 10(5); 95% CI of difference, -9.4 × 10(4) to -5.0 × 10(3); p < 0.001) and STIM (mean, 2.6 × 10(4); SD, 2.5 × 10(4); 95% CI of difference, -4.1 × 10(4) to -1.6 × 10(3); p < 0.001) groups. The VANCO group (4.3 × 10(5); SD, 6.3 × 10(2)) also had lower bone-associated CFU as compared with the CONT (mean 95% CI of difference, -9.3 × 10(4) to -4.5 × 10(3); p < 0.001) and STIM (95% CI of difference, -4.0 × 10(4) to -1.5 × 10(3); p < 0.001) groups. In comparison to the synovial fluid CFU enumerated from the CONT group (mean, 3.3 × 10(4); SD, 6.0 × 10(4)), lower synovial CFU were reported for both the STIM + VANCO group (mean, 4.6 × 10(1); SD, 1.2 × 10(2); 95% CI of difference, -4.9 × 10(3) to -3.0 × 10(2); p < 0.001) and the VANCO group (mean, 6.8 × 10(1); SD, 9.2 × 10(1); 95% CI of difference, -4.9 × 10(3) to -2.8 × 10(2); p = 0.007). The histological analysis showed no discernable deleterious effects on the surrounding tissue as a result of the treatments. No brittle fracture occurred during mechanical testing and with the numbers available, no differences in implant flexural yield strength were detected between the groups. CONCLUSIONS: In this rodent model, cathodic voltage-controlled electrical stimulation combined with vancomycin is an effective treatment for titanium implant-associated infections showing greater than 99.8% reduction in bacterial burden on the implant, surrounding bone, and synovial fluid as compared with the controls and the stimulation alone groups. CLINICAL RELEVANCE: Cathodic voltage-controlled electrical stimulation combined with vancomycin may enable successful treatment of titanium orthopaedic implant-associated infections with implant retention. Future studies will focus on optimization of the stimulation parameters for complete eradication of infection and the ability to promote beneficial host tissue responses.

Asunto(s)

Antibacterianos/farmacología , Artroplastia de Reemplazo/efectos adversos , Artroplastia de Reemplazo/instrumentación , Terapia por Estimulación Eléctrica/instrumentación , Cabeza Humeral/efectos de los fármacos , Prótesis Articulares , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Infecciones Relacionadas con Prótesis/terapia , Infecciones Estafilocócicas/terapia , Vancomicina/farmacología , Animales , Carga Bacteriana , Recuento de Colonia Microbiana , Terapia Combinada , Modelos Animales de Enfermedad , Electrodos , Diseño de Equipo , Cabeza Humeral/microbiología , Cabeza Humeral/patología , Cabeza Humeral/cirugía , Masculino , Staphylococcus aureus Resistente a Meticilina/patogenicidad , Diseño de Prótesis , Infecciones Relacionadas con Prótesis/microbiología , Infecciones Relacionadas con Prótesis/patología , Ratas Long-Evans , Infecciones Estafilocócicas/microbiología , Infecciones Estafilocócicas/patología , Líquido Sinovial/microbiología , Factores de Tiempo , Titanio

RESUMEN

Effective treatment options are often limited for implant-associated orthopedic infections. In this study we evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) of -1.8 V (vs. Ag/AgCl) to commercially pure titanium (cpTi) substrates with preformed biofilm-like structures of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that as compared to the open circuit potential (OCP) conditions, CVCES of -1.8 V for 1 h significantly reduced the colony-forming units (CFU) of MRSA enumerated from the cpTi by 97% (1.89 × 106 vs 6.45 × 104 CFU/ml) and from the surrounding solution by 92% (6.63 × 105 vs. 5.15 × 104 CFU/ml). The in vivo studies, utilizing a rodent periprosthetic infection model, showed that as compared to the OCP conditions, CVCES at -1.8 V for 1 h significantly reduced MRSA CFUs in the bone tissue by 87% (1.15 × 105 vs. 1.48 × 104 CFU/ml) and reduced CFU on the cpTi implant by 98% (5.48 × 104 vs 1.16 × 103 CFU/ml). The stimulation was not associated with histological changes in the host tissue surrounding the implant. As compared to the OCP conditions, the -1.8 V stimulation significantly increased the interfacial capacitance (18.93 vs. 98.25 µF/cm(2)) and decreased polarization resistance (868,250 vs. 108 Ω-cm(2)) of the cpTi. The antimicrobial effects are thought to be associated with these voltage-dependent electrochemical surface properties of the cpTi.

Asunto(s)

Electricidad , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Prótesis e Implantes , Infecciones Relacionadas con Prótesis/tratamiento farmacológico , Infecciones Relacionadas con Prótesis/microbiología , Titanio/farmacología , Titanio/uso terapéutico , Animales , Ensayo de Unidades Formadoras de Colonias , Espectroscopía Dieléctrica , Capacidad Eléctrica , Estimulación Eléctrica , Electrodos , Masculino , Ratas Long-Evans

RESUMEN

PURPOSE: This study was conducted to assess whether a single-row suture anchor repair of a bony Bankart lesion comprising 19% of the glenoid length restores peak translational force and glenoid depth compared with the intact shoulder. METHODS: Nine thawed adult cadaveric shoulders were dissected and mounted in 45° of abduction and 30° of external rotation. A bony Bankart lesion was simulated with an anterior longitudinal osteotomy, parallel to the superoinferior axis of the glenoid, equivalent to 19% of the glenoid length. The humeral head was displaced 10 mm anteriorly at a speed of 2 mm/s with a 50-N compressive load applied. Testing was performed with the glenoid intact, a simulated lesion, and the lesion repaired with 3 single-row suture anchors. Median (interquartile range [IQR]) peak translational force and glenoid depth were reported. The Friedman test and post hoc comparisons with the Wilcoxon signed rank test were used for between-group analyses. RESULTS: Peak translational force decreased after osteotomy (13.7 N; IQR, 9.6 to 15.5 N; P = .01) and increased after the repair (18.3 N; IQR, 18.3 to 20.6 N; P = .01) compared with the intact shoulder (23.7 N; IQR, 16.4 to 29.9 N). Glenoid depth significantly decreased after the osteotomy (0.2 mm; IQR, -0.6 to 0.7 mm) compared with baseline (1.7 mm; IQR, 1.3 to 2.0 mm; P = .01) and increased after repair (0.8 mm; IQR, 0.1 to 1.0 mm; P = .03) compared with the osteotomized shoulder. The glenoid depth of the repair was less than the baseline value (P = .01). CONCLUSIONS: Repair of an anterior bony Bankart lesion equivalent to 19% of the glenoid length with 3 suture anchors restored the peak translational force needed to anteriorly displace the humerus relative to the glenoid; however, this technique failed to restore the natural glenoid depth in a laboratory setting. CLINICAL RELEVANCE: Our findings describe the inability of a single-row suture anchor repair to provide anatomic fixation of the bony Bankart lesion equivalent to 19% of the glenoid length.

Asunto(s)

Fracturas del Hombro/cirugía , Lesiones del Hombro , Anclas para Sutura , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Cadáver , Femenino , Humanos , Cabeza Humeral , Inestabilidad de la Articulación/etiología , Inestabilidad de la Articulación/cirugía , Masculino , Persona de Mediana Edad , Osteotomía/métodos , Rotación , Luxación del Hombro/cirugía , Fracturas del Hombro/fisiopatología , Articulación del Hombro/cirugía

RESUMEN

This study evaluated the influence of simulated inflammation and cathodic polarization on the electrochemical properties of commercially pure titanium (CpTi) and titanium-6%aluminum-4%vanadium (Ti6Al4V). Normal conditions immersed the metals in phosphate buffered saline at open circuit potential (OCP). Inflammatory conditions immersed the metals in a 150 mM hydrogen peroxide titrated to pH = 5.0 at OCP. Cathodic inflammatory conditions immersed the metals in the inflammatory electrolyte at -1 V versus Ag/AgCl. Cathodic polarization scans revealed a more electropositive corrosion potential (Ecorr ) and an increased corrosion current density (Icorr ) for both metals after incubation at inflammatory conditions (CpTi: Ecorr = 171 mV, Icorr = 147 nA/cm(2) and Ti6Al4V: Ecorr = 241 mV and Icorr = 413 nA/cm(2) ) as compared to normal conditions (CpTi: Ecorr = -249 mV, Icorr = 19 nA/cm(2) and Ti6Al4V: Ecorr = -263 mV and Icorr = 11 nA/cm(2) ). Electrochemical impedance spectroscopy showed the polarization resistance (Rp ) decreases and constant phase element (CPE) magnitude increases for both metals when comparing normal (CpTi: Rp = 3.5 MΩ cm(2) , CPE = 35 µS s(α) /cm(2) and Ti6Al4V: Rp = 6.5 MΩ cm(2) and CPE = 30 µS s(α) /cm(2) ) to inflammatory (CpTi: Rp = 79 kΩ cm(2) , CPE = 55 µS s(α) /cm(2) and Ti6Al4V: Rp = 230 kΩ cm(2) and CPE = 56 µS s(α) /cm(2) ) to cathodic inflammatory (CpTi: Rp =24 kΩ cm(2) , CPE = 290 µS s(α) /cm(2) and Ti6Al4V: Rp = 12 kΩ cm(2) and CPE = 250 µS s(α) /cm(2) ) conditions. These observed changes are consistent with the formation of a thin and defective oxide film. Inductively coupled plasma mass spectroscopy revealed that inflammatory conditions increased dissolution of both metals and that the addition of cathodic potential significantly increased the dissolution of the beta phase elements of Ti6Al4V.

Asunto(s)

Técnicas Electroquímicas , Modelos Biológicos , Titanio/química , Aleaciones , Inflamación/inducido químicamente , Inflamación/metabolismo , Titanio/farmacología

RESUMEN

BACKGROUND: A novel biomechanical test method was implemented to compare the mechanical performance of two femoral fixation anchors (AperFix(r), Cayenne Medical, Scottsdale, AZ, USA or the AppianFx(r), KFx Medical, Carlsbad, CA, USA) that were utilized in anterior cruciate ligament reconstruction. METHODS: Anterior cruciate ligament reconstructions were performed in 20 porcine femurs by using bovine extensor tendon grafts secured with 9 mm femoral anchors (AperFix(r) or AppianFx(r)). 10 specimens were tested for each anchor type. Infrared position sensors determined the repair construct displacements during conditioning (20 cycles at 5-50 N at 0.25 Hz), cyclic loading (1500 cycles at 50-200 N at 1 Hz), and ultimate loading (150 mm/min). Outcomes included tendon elongation, anchor displacement, stiffness, maximum load, yield load, and load at 5mm of anchor displacement. It was hypothesized that there would be no differences in the outcomes of these two devices. Independent measure t-tests compared the performance of the devices (p<0.05). FINDINGS: The performance of the two anchors was comparable during the cyclic loading. During ultimate loading, a statistically higher yield load (p<0.01) and a load at 5mm of anchor displacement (p<0.01) were demonstrated for the AppianFx(r) as compared to AperFix(r). Maximum load and stiffness were not significantly different. INTERPRETATION: Given the good clinical track record of the AperFix(r), the comparable, and in some cases superior, the biomechanical data presented here for the AppianFx(r) are encouraging for their clinical implementation. This study also introduced a novel test method that directly tracks the relevant construct displacements during cyclic and ultimate loading tests of the anterior cruciate ligament reconstructions.

Asunto(s)

Reconstrucción del Ligamento Cruzado Anterior/instrumentación , Reconstrucción del Ligamento Cruzado Anterior/métodos , Fémur , Anclas para Sutura , Animales , Fenómenos Biomecánicos/fisiología , Bovinos , Fémur/cirugía , Estrés Mecánico , Porcinos