Evaluation of the Effect of Ciprofloxacin and Vancomycin on Mechanical Properties of PMMA Cement; a Preliminary Study on Molecular Weight

Effect of using nano-particles of magnesium oxide and titanium dioxide to enhance physical and mechanical properties of hip joint bone cement

In this work, the effect of adding Magnesium Oxide (MgO) and Titanium Dioxide (TiO2) nanoparticles to enhance the properties of the bone cement used for hip prosthesis fixation. Related to previous work on enhanced bone cement properties utilizing MgO and TiO2, samples of composite bone cement were made using three different ratios (0.5%:1%, 1.5%:1.5%, and 1%:0.5%) w/w of MgO and TiO2 to determine the optimal enhancement ratio. Hardness, compression, and bending tests were calculated to check the mechanical properties of pure and composite bone cement. The surface structure was studied using Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FE-SEM). Setting temperature, porosity, and degradation were calculated for each specimen ratio to check values matched with the standard range of bone cement. The results demonstrate a slight decrease in porosity up to 2.2% and degradation up to 0.17% with NP-containing composites, as well as acceptable variations in FTIR and setting temperature. The compression strength increased by 2.8% and hardness strength increased by 1.89% on adding 0.5%w/w of MgO and 1.5%w/w TiO2 NPs. Bending strength increases by 0.35% on adding 1.5% w/w of MgO and 0.5% w/w TiO2 NPs, however, SEM scan shows remarkable improvement for surface structure.

Statistical distribution of micro and macro pores in acrylic bone cement- effect of amount of antibiotic content

Aseptic loosening due to mechanical failure of bone cement is considered to be a leading cause of revision of joint replacement systems. Detailed quantified information on the number, size and distribution pattern of pores can help to obtain a deeper understanding of the bone cement's fatigue behavior. The objective of this study was to provide statistical descriptions for the pore distribution characteristics of laboratory bone cement specimens with different amounts of antibiotic contents. For four groups of bone cement (Palacos) specimens, containing 0.3, 0.6, 1.2 and 2.4 wt/wt% of telavancin antibiotic, seven samples per group were micro computed tomography scanned (38.97 μm voxel size). The images were first preprocessed in Mimics and then analyzed in Dragonfly, with the level of threshold being set such that single-pixel pores become visible. The normalized pore volume data of the specimens were then used to extract the logarithmic histograms of the pore densities for antibiotic groups, as well as their three-parameter Weibull probability density functions. Statistical comparison of the pore distribution data of the antibiotic groups using the Mann-Whitney non-parametric test revealed a significantly larger porosity (p < 0.05) in groups with larger added antibiotic contents (2.4 and 0.6 wt/wt% vs 0.3 wt/wt%). Further analysis revealed that this effect was associated with the significantly larger frequency of micropores of 0.1-0.5 mm diameter (p < 0.05) in groups with larger antibiotic content (2.4 wt/wt% vs and 0.6 and 0.3 wt/wt%), implying that the elution of the added antibiotic produces micropores in this diameter range mainly. Based on this observation and the fatigue test results in the literature, it was suggested that micropore clusters have a detrimental effect on the mechanical properties of bone cement and play a major role in initiating fatigue cracks in highly antibiotic added specimens.

Efficacy of Cefazolin Versus Vancomycin Antibiotic Cement Spacers

OBJECTIVE

Cefazolin is a heat-labile antibiotic that is not usually added to polymethylmethacrylate (PMMA) cement spacers because it is believed to be inactivated by the high polymerization temperatures. The purpose of this study was to compare cefazolin versus vancomycin high-dose antibiotic cement spacers.

METHODS

High-dose antibiotic PMMA spacers with either cefazolin or vancomycin were fabricated. Setting time, compressive strength, and compression modulus of spacers were measured. Spacers were emerged in saline, and the eluent was tested on days 1, 2, 3, 7, 14, and 30 to determine the zone of inhibition of methicillin-sensitive Staphylococcus aureus and estimate the cumulative antibiotic released.

RESULTS

Cefazolin, compared with vancomycin-loaded spacers, had significantly shorter setting time [mean difference (MD) -1.8 minutes, 95% confidence interval (CI), -0.6 to -3.0], greater compressive strength (MD 20.1 megapascal, CI, 15.8 to 24.5), and compression modulus (MD 0.15 megapascal, CI, 0.06 to 0.23). The zone of inhibition of eluent from PMMA-C spacers was significantly greater than PMMA-V spacers at all time points, an average of 11.7 ± 0.8 mm greater across time points. The estimated cumulative antibiotic released from cefazolin spacers was significantly greater at all time points ( P < 0.0001).

CONCLUSIONS

Cefazolin was not inactivated by PMMA polymerization and resulted in spacers with superior antimicrobial and biomechanical properties than those made with vancomycin, suggesting that cefazolin could play a role in the treatment of infected bone defects with high-dose antibiotic PMMA spacers.

Meropenem-loaded Cement Is Effective in Preventing Gram-negative Osteomyelitis in an Animal Model

BACKGROUND

Low-dose antibiotic-loaded acrylic cement is routinely used for preventing skeletal infection or reimplantation in patients with periprosthetic joint infections. However, few reports about the selection of antibiotics in acrylic cement for antigram-negative bacteria have been proposed.

QUESTIONS/PURPOSES

(1) Does the addition of antibiotics (tobramycin, meropenem, piperacillin, ceftazidime, ciprofloxacin, and aztreonam) to acrylic cement adversely affect compressive strength before and after elution? (2) Which antibiotics have the highest cumulative release within 28 days? (3) Which antibiotics showed antimicrobial activity within 28 days? (4) Does meropenem-loaded cement improve body weight, temperature, and other inflammatory markers compared with control unloaded cement?

METHODS

This is an in vitro study that assessed the mechanical strength, antibiotic elution, and antibacterial properties of antibiotic-loaded cement, combined with an animal study in a rat model that evaluated key endpoints from the animal study. In the in vitro study, we added 2 g of tobramycin (TOB), meropenem (MEM), piperacillin (PIP), ceftazidime (CAZ), ciprofloxacin (CIP), and aztreonam (ATM) to 40 g of acrylic cement. The compressive strength, elution, and in vitro antibacterial properties of the antibiotic-loaded cement were detected. Thirty male rats were randomly divided into two groups: CON (antibiotic-unloaded cement) and MEM (meropenem-loaded cement, which had the most stable antibacterial properties of the six tested antibiotic-loaded cements in vitro within 28 days). The right tibia of all rats underwent arthroplasty and was implanted with the cement, followed by inoculation with Pseudomonas aeruginosa in the knee. General status, serum biomarkers, radiology, microbiological assay, and histopathological tests were assessed over 14 days postoperatively.

RESULTS

The compressive strength of all tested antibiotic cement combinations exceeded the 70 MPa threshold (the requirement established in ISO 5833). The cumulative release proportions of the raw antibiotic in cement were 1182.8 ± 37.9 µg (TOB), 355.6 ± 16.2 µg (MEM), 721.2 ± 40.3 µg (PIP), 477.4 ± 37.1 µg (CAZ), 146.5 ± 11.3 µg (CIP), and 372.1 ± 14.5 µg (ATM) within 28 days. Over a 28-day period, meropenem cement demonstrated antimicrobial activities against the four tested gram-negative bacteria ( Escherichia coli , P. aeruginosa , Klebsiella pneumoniae , and Proteus vulgaris ). Ciprofloxacin cement inhibited E. coli growth, ceftazidime and aztreonam cement inhibited K. pneumonia growth, and tobramycin cement inhibited P. aeruginosa . Only meropenem demonstrated antimicrobial activity against all gram-negative bacteria on agar diffusion bioassay. Rats treated with meropenem cement showed improved body weight (control: 280.1 ± 4.2 g, MEM: 288.5 ± 6.6 g, mean difference 8.4 [95% CI 4.3 to 12.6]; p < 0.001), improved knee width (control: 13.5 ± 0.3 mm, MEM: 11.8± 0.4 mm, mean difference 1.7 [95% CI 1.4 to 2.0]; p < 0.001), decreased inflammatory marker (control: 316.7 ± 45.0 mm, MEM: 116.5 ± 21.8 mm, mean difference 200.2 [95% CI 162.3 to 238.2]; p < 0.001), decreased radiographic scores (control: 17.7 ± 2.0 mm, MEM: 10.7± 1.3 mm, mean difference 7.0 [95% CI 5.4 to 8.6]; p < 0.001), improved bone volume/total volume (control: 8.7 ± 3.0 mm, MEM: 28.5 ± 5 .5 mm, mean difference 19.8 [95% CI 13.3 to 26.2]; p < 0.001), decreased Rissing scale scores of the knee gross pathology (control: 3.3 ± 0.5, MEM: 1.1 ± 0.7, mean difference 2.2 [95% CI 1.7 to 2.7]; p < 0.001), decreased Petty scale scores of knee synovium (control: 2.9 ± 0.4 mm, MEM: 0.7 ± 0.7 mm, mean difference 2.1 [95% CI 1.7 to 2.5]; p < 0.001), and decreased bacterial counts of the bone and soft tissues and negative bacterial cultures of cement (p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively).

CONCLUSION

In this current study, MEM cement had the most stable in vitro antimicrobial activities, effective in vivo activity while having acceptable mechanical and elution characteristics, and it may be an effective prophylaxis against skeletal infection caused by gram-negative bacteria.

CLINICAL RELEVANCE

Meropenem-loaded acrylic cement is a potentially effective prevention measure for skeletal infection caused by gram-negative bacteria; however, more related clinical research is needed to further evaluate the safety and efficacy.

Clinical study on orthopaedic treatment of chronic osteomyelitis with soft tissue defect in adults

To investigate the clinical application value of different flap transfer and repair techniques in adult patients with chronic osteomyelitis of limbs complicated with soft tissue defects. According to the characteristics and defects of 21 cases, different plastic surgery was applied, including debridement, negative pressure device, and tissue flap to cover wound. Among 21 cases of chronic osteomyelitis complicated with local soft tissue defect, 15 patients were repaired with sural neurotrophic musculocutaneous flap transfer, 2 patients were repaired with medial plantar skin flap transfer, 2 patients were repaired with ilioinguinal skin flap transfer, 1 patient was repaired with z‐forming wound, and 1 patient was repaired with soleus muscle flap combined with full‐thickness skin graft. All the 21 patients underwent bone cement implantation after dead bone osteotomy. Among them, 19 patients underwent bone cement replacement with 3D prosthesis within 6 months to 1 year after surgery, and 2 patients carried bone cement for a long time. Early intervention, thorough debridement, removal of necrotic or infection, and then selecting the appropriate wound skin flap coverage are important means of guarantee slow osteomyelitis wound healing and for providing a possible way to permanent prosthesis implantation subsequently.

Preparation of bioactive and antibacterial PMMA-based bone cement by modification with quaternary ammonium and alkoxysilane

Bone cement based on poly(methyl methacrylate) (PMMA) powder and methyl methacrylate (MMA) liquid is a very popular biomaterial used for the fixation of artificial joints. However, there is a risk of this cement loosening from bone because of a lack of bone-bonding bioactivity. Apatite formation in the body environment is a prerequisite for cement bioactivity. Additionally, suppression of infection during implantation is required for bone cements to be successfully introduced into the human body. In this study, we modified PMMA cement with γ-methacryloxypropyltrimetoxysilane and calcium acetate to introduce bioactive properties and 2-(tert-butylamino)ethyl methacrylate (TBAEMA) to provide antibacterial properties. The long-term antibacterial activity is attributed to the copolymerization of TBAEMA and MMA. As the TBAEMA content increased, the setting time increased and the compressive strength decreased. After soaking in simulated body fluid, an apatite layer was detected within 7 days, irrespective of the TBAEMA content. The cement showed better antibacterial activity against Gram-negative E. Coli than Gram-positive bacteria; however, of the Gram-positive bacteria investigated, B. subtilis was more susceptible than S. aureus.

The Role of Chitosan and Graphene Oxide in Bioactive and Antibacterial Properties of Acrylic Bone Cements

Acrylic bone cements (ABC) are widely used in orthopedics for joint fixation, antibiotic release, and bone defect filling, among others. However, most commercially available ABCs exhibit a lack of bioactivity and are susceptible to infection after implantation. These disadvantages generate long-term loosening of the prosthesis, high morbidity, and prolonged and expensive treatments. Due to the great importance of acrylic bone cements in orthopedics, the scientific community has advanced several efforts to develop bioactive ABCs with antibacterial activity through several strategies, including the use of biodegradable materials such as chitosan (CS) and nanostructures such as graphene oxide (GO), with promising results. This paper reviews several studies reporting advantages in bioactivity and antibacterial properties after incorporating CS and GO in bone cements. Detailed information on the possible mechanisms by which these fillers confer bioactive and antibacterial properties to cements, resulting in formulations with great potential for use in orthopedics, are also a focus in the manuscript. To the best of our knowledge, this is the first systematic review that presents the improvement in biological properties with CS and GO addition in cements that we believe will contribute to the biomedical field.

Use of Deep Learning Networks and Statistical Modeling to Predict Changes in Mechanical Parameters of Contaminated Bone Cements

The purpose of the study was to test the usefulness of deep learning artificial neural networks and statistical modeling in predicting the strength of bone cements with defects. The defects are related to the introduction of admixtures, such as blood or saline, as contaminants into the cement at the preparation stage. Due to the wide range of applications of deep learning, among others in speech recognition, bioinformation processing, and medication design, the extent was checked to which it is possible to obtain information related to the prediction of the compressive strength of bone cements. Development and improvement of deep learning network (DLN) algorithms and statistical modeling in the analysis of changes in the mechanical parameters of the tested materials will enable determining an acceptable margin of error during surgery or cement preparation in relation to the expected strength of the material used to fill bone cavities. The use of the abovementioned computer methods may, therefore, play a significant role in the initial qualitative assessment of the effects of procedures and, thus, mitigation of errors resulting in failure to maintain the required mechanical parameters and patient dissatisfaction.

Fracture Behavior of Two Biopolymers Containing Notches: Effects of Notch Tip Plasticity

This paper analyzes the notch effect on the fracture behavior of two biomaterials (a brittle bone cement and a ductile dental material) under mode I loading. U-notched Brazilian disk (UNBD) specimens of both materials were tested under remote compression, determining the corresponding fracture loads and load-displacement curves. Additionally, cracked rectangular and semicircular bend (SCB) specimens were tested under symmetric three-point bending in order to determine the fracture toughness of the two materials. Then, fracture loads were derived theoretically by applying the maximum tangential stress (MTS) and the mean stress (MS) criteria. Due to the brittle linear elastic behavior of the bone cement material, the MTS and MS criteria were directly applied to this material; however, given the significant nonlinear behavior of the dental material, the two fracture criteria were combined with the Equivalent Material Concept (EMC) for the fracture analyses of the dental material specimens. The results reveal a very good accuracy of both the MTS and the MS criteria for the fracture analysis of bone cement notched specimens. In the case of the dental material, very good results are also obtained when combining the MTS and the MS criteria with the EMC. The proposed approach can be useful for the fracture analysis of a wide range of biopolymers, from brittle to ductile behavior.