Compression strength and porosity of single-antibiotic cement vacuum-mixed with vancomycin

Effects of vancomycin and tobramycin on compressive and tensile strengths of antibiotic bone cement: A biomechanical study

Purpose

This study aims to compare the compressive and tensile strengths of bone cement mixed with various concentrations of vancomycin, tobramycin, and combinations of the two.

Methods

12 mm × 6 mm antibiotic bone cement samples were created by vacuum mixing 0-4 g of vancomycin, tobramycin, and combinations of the two in 0.5 g increments per one pouch (40 g) of Palacos LV cement. An Instron 3369 Universal Testing System was used to determine the compressive and tensile strengths.

Results

Compressive and tensile strengths of the bone cement without antibiotics were 118 ± 4 MPa and 30.3 ± 12 MPa, respectively. 4 g of vancomycin alone decreased the compressive strength to 108 ± 4 MPa (p-value 0.001) and decreased the tensile strength beginning at 2 g which yielded a strength of 28.1 ± 12 MPa (p-value 0.016). Tobramycin alone decreased the tensile strength beginning at 1.5 g yielding a strength of 27.7 ± 7 MPa (p-value 0.003). Although it decreased compressive strength at 1 g to 117 ± 7 MPa (p-value 0.002), it demonstrated variable effects with increasing concentrations. A combination of vancomycin and tobramycin decreased both the compressive (111 ± 5 MPa, p-value 0.014) and tensile (27.9 ± 8 MPa, p-value 0.007) strengths beginning at 1 g each.

Conclusions

Various combinations of vancomycin and tobramycin affect the compressive and tensile strengths of bone cement. Clinicians should be diligent when mixing these antibiotics in bone cement to prevent possible failure of the constructs.

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.

Composite Bone Cements with Enhanced Drug Elution

Antibiotic-loaded bone cement (ALBC) has become an indispensable material in orthopedic surgery in recent decades, owing to the possibility of drugs delivery to the surgical site. It is applied for both infection prophylaxis (e.g., in primary joint arthroplasty) and infection treatment (e.g., in periprosthetic infection). However, the introduction of antibiotic to the polymer matrix diminishes the mechanical strength of the latter. Moreover, the majority of the loaded antibiotic remains embedded in polymer and does not participate in drug elution. Incorporation of the various additives to ALBC can help to overcome these issues. In this paper, four different natural micro/nanoscale materials (halloysite, nanocrystalline cellulose, micro- and nanofibrillated cellulose) were tested as additives to commercial Simplex P bone cement preloaded with vancomycin. The influence of all four materials on the polymerization process was comprehensively studied, including the investigation of the maximum temperature of polymerization, setting time, and monomer leaching. The introduction of the natural additives led to a considerable enhancement of drug elution and microhardness in the composite bone cements compared to ALBC. The best combination of the polymerization rate, monomer leaching, antibiotic release, and microhardness was observed for the sample containing nanofibrillated cellulose (NFC).

Mechanical strength of antibiotic-loaded PMMA spacers in two-stage revision surgery

Background

Antibiotic-loaded polymethylmethacrylate (PMMA) bone cement spacers provide high local antibiotic concentrations and patient mobility during the interim period of two-stage revision for periprosthetic joint infection (PJI). This study compares mechanical characteristics of six dual antibiotic-loaded bone cement (dALBC) preparations made from three different PMMA bone cements. The study`s main objective was to determine the effect of time and antibiotic concentration on mechanical strength of dALBCs frequently used for spacer fabrication in the setting of two-stage revision for PJI.

Methods

A total of 84 dual antibiotic-loaded bone cement specimens made of either Copal spacem, Copal G + V or Palacos R + G were fabricated. Each specimen contained 0.5 g of gentamicin and either 2 g (low concentration) or 4 g (high concentration) of vancomycin powder per 40 g bone cement. The bending strength was determined at two different timepoints, 24 h and six weeks after spacer fabrication, using the four-point bending test.

Results

Preparations made from Copal G + V showed the highest bending strength after incubation for 24 h with a mean of 57.6 ± 1.2 MPa (low concentration) and 50.4 ± 4.4 MPa (high concentration). After incubation for six weeks the bending strength had decreased in all six preparations and Palacos R + G showed the highest bending strength in the high concentration group (39.4 ± 1.6 MPa). All low concentration preparations showed superior mechanical strength compared to their high concentration (4 g of vancomycin) counterpart. This difference was statistically significant for Copal spacem and Copal G + V (both p < 0.001), but not for Palacos R + G (p = 0.09).

Conclusions

This study suggests that mechanical strength of antibiotic-loaded PMMA bone cement critically decreases even over the short time period of six weeks, which is the recommended interim period in the setting of two-stage revision. This potentially results in an increased risk for PMMA spacer fracture at the end of the interim period and especially in patients with prolonged interim periods. Finally, we conclude that intraoperative addition of 4 g of vancomycin powder per 40 g of gentamicin-premixed Palacos R + G (Group D) is mechanically the preparation of choice if a dual antibiotic-loaded bone cement spacer with high antibiotic concentrations and good stability is warranted. In any case the written and signed informed consent including the off-label use of custom-made antibiotic-loaded PMMA bone cement spacers must be obtained before surgery.

Influence of Tranexamic Acid on Elution Characteristics and Compressive Strength of Antibiotic-Loaded PMMA-Bone Cement with Gentamicin

PURPOSE

The topical application of tranexamic acid (TXA) into the joint space during total joint arthroplasty (TJA) with no increase of complications, has been widely reported. We investigated the influence of TXA on antibiotic release, activity of the released antibiotic against a clinical isolate of S. aureus, and compressive strength of a widely used commercially prepared gentamicin-loaded cement brand (PALACOS R + G).

METHOD

12 bone cement cylinders (diameter and height = 6 and 12 mm, respectively) were molded. After curing in air for at least 1 h, six of the cylinders were completely immersed in 5 mL of fetal calf serum (FCS) and the other six were completely immersed in a solution consisting of 4.9 mL of FCS and 0.1 mL (10 mg) of TXA. Gentamicin elution tests were performed over 7 d. Four hundred µL of the gentamicin eluate were taken every 24 h for the first 7 d without renewing the immersion fluid. The gentamicin concentration was determined in a clinical analyzer using a homogeny enzyme immuno-assay. The antimicrobial activity of the eluate, obtained after day 7, was tested. An agar diffusion test regime was used with Staphylococcus aureus. Bacteria were grown in a LB medium and plated on LB agar plates to get a bacterial lawn. Fifty µL of each eluate were pipetted on 12-mm diameter filter discs, which were placed in the middle of the agar gel. After 24 h of cultivation at 37 °C, the zone of inhibition (ZOI) for each specimen was measured. The compressive strength of the cements was determined per ISO 5833.

RESULTS

At each time point in the gentamicin release test, the difference in gentamicin concentration, obtained from specimens immersed in the FCS solution only and those immersed in the FCS + TXA solution was not significant (p = 0.055-0.522). The same trend was seen in each of the following parameters, after 7 d of immersion: (1) Cumulative gentamicin concentration (p < 0.297); (2) gentamicin activity against S. aureus (strongly visible); (3) ZOI size (mostly > 20 mm) (p = 0.631); and (4) compressive strength (p = 0.262).

CONCLUSIONS

For the PALACOS R + G specimens, the addition of TXA to FCS does not produce significant decreases in gentamicin concentration, in the activity of the gentamicin eluate against a clinical isolate of S. aureus, the zone of inhibition of S. aureus, and in the compressive strength of the cement, after 7 d of immersion in the test solution.

Does the Effectiveness and Mechanical Strength of Kanamycin-Loaded Bone Cement in Musculoskeletal Tuberculosis Compare to Vancomycin-Loaded Bone Cement

BACKGROUND

Antibiotic-loaded bone cement (ALBC) is used to deliver antimycobacterial agents into the focal lesion of musculoskeletal tuberculosis. Although kanamycin is currently used as an antimycobacterial agent for the treatment of multidrug-resistant tuberculosis, there is no information about its suitability in ALBC.

METHODS

An in vitro experiment was conducted with cylindrical shape of 40 g of bone cement with 1, 2, and 3 g of kanamycin. Eluate (1 mL) was extracted from each specimen to measure the level of elution and antimycobacterial activity on days 1, 4, 7, 14, and 30. The quantity of kanamycin in eluates was evaluated by a liquid chromatography-mass spectrometry system, and the antimycobacterial activity of eluates against Mycobacterium tuberculosis H37Rv was calculated by comparing the minimal inhibitory concentration. The ultimate compression strength was conducted using a material testing system machine (Instron 3366; Instron, Norwood, MA) before and after elution.

RESULTS

Eluates from ALBC containing 2 and 3 g of kanamycin had effective antimycobacterial activity for 30 days, whereas eluates from ALBC containing 1 g of kanamycin were partially active until day 30. The pre-eluted compression strength of kanamycin-loaded cement and vancomycin-loaded cement was weaker as they contained a larger amount of antibiotics. There was no statistical difference between the strength of all kanamycin regimens and 1 g of vancomycin in the ultimate compression test. After 30 days of elution, the strength of all kanamycin-loaded cement and vancomycin-loaded cement cylinders was significantly lower than that of initial specimens (P < .05).

CONCLUSION

The antimycobacterial activity of ALBC containing more than 2 g of kanamycin was effective during a 30-day period. The ultimate compression strength of bone cement loaded with 1-3 g of kanamycin was comparable with 1 g of vancomycin while maintaining effective elution until day 30.

Antibiotic elution and compressive strength of gentamicin/vancomycin loaded bone cements are considerably influenced by immersion fluid volume

The effect of doubling the immersion fluid (eluate) volume on antibiotic concentrations and on mechanical stability from vancomycin and gentamicin loaded bone cements was investigated in vitro. Antibiotic loaded bone cements containing premixed 1.34% gentamicin antibiotic concentration in the cement powder (wt), premixed 1.19% gentamicin wt and 4.76% vancomycin wt and premixed 1.17% wt gentamicin additionally manually blended with 4.68% wt vancomycin were tested. Six specimens per group were immersed in 4 ml and 8 ml for 6 weeks while the eluate was exchanged every 24 h. The antibiotic concentrations were repeatedly measured. Then the specimens were tested for compressive strength. Doubling the eluate volume significantly decreased gentamicin and vancomycin concentrations from 6 h and 24 h on, except for the gentamicin concentration of the additionally manually blended formulation after 3 weeks. The additionally manually blended vancomycin formulation produced significantly higher gentamicin concentrations in 8 ml compared to the other formulations. The reduction ratios of the vancomycin concentrations were significantly smaller than the reduction ratios of the gentamicin concentrations for the manually blended vancomycin formulation. Vancomycin containing formulations showed significantly lower compressive strengths than the vancomycin free formulation after immersion. Doubling the eluate volume lead to significant compressive strength reduction of the vancomycin containing formulations. Eluate volume change influences antibiotic elution dependent on the antibiotic combination and loading technique. The reducing effect is higher on vancomycin than on gentamicin elution. Compressive strength of gentamicin/vancomycin loaded bone cements after immersion is eluate volume dependent.

Comparison of Elution Characteristics and Compressive Strength of Biantibiotic-Loaded PMMA Bone Cement for Spacers: Copal® Spacem with Gentamicin and Vancomycin versus Palacos® R+G with Vancomycin

Purpose

Copal® spacem is a new PMMA bone cement for fabricating spacers. This study compares elution of gentamicin, elution of vancomycin, and compressive strength of Copal® spacem and of Palacos® R+G at different vancomycin loadings in the powder of the cements. We hypothesized that antibiotic elution of Copal® spacem is superior at comparable compressive strength.

Methods

Compression test specimens were fabricated using Copal® spacem manually loaded with 0.5 g gentamicin and additionally 2 g, 4 g, and 6 g of vancomycin per 40 g of cement powder (COP specimens) and using 0.5 g gentamicin premixed Palacos® R+G manually loaded with 2 g, 4 g, and 6 g of vancomycin per 40 g of cement powder (PAL specimens). These specimens were used for determination of gentamicin and vancomycin elution (in fetal calf serum, at 22°C) and for determination of compressive strength both prior and following the elution tests.

Results

Cumulative gentamicin concentrations (p < 0.005) and gentamicin concentration after 28 days (p ≤ 0.043) were significantly lower for COP specimens compared to PAL specimens. Cumulative vancomycin concentrations were significantly higher (p ≤ 0.043) for COP specimens after the second day. Vancomycin concentrations after 28 days were not significantly higher for the Copal specimens loaded with 2 g and 4 g of vancomycin. Compressive strength was not significantly different between COP specimens and PAL specimens before elution tests. Compressive strength after the elution tests was significantly lower (p = 0.005) for COP specimens loaded with 2 g of vancomycin.

Conclusion

We could not demonstrate consistent superior antibiotic elution from Copal® spacem compared to Palacos® R+G for fabricating gentamicin and vancomycin loaded spacers. The results do not favor Copal® spacem over Palacos® R+G for the use as a gentamicin and vancomycin biantibiotic-loaded spacer.

Antibiotic Elution and Mechanical Strength of PMMA Bone Cement Loaded With Borate Bioactive Glass

Introduction: Local delivery of antibiotics using bone cement as the delivery vehicle is an established method of managing implant-associated orthopedic infections. Various fillers have been added to cement to increase antibiotic elution, but they often do so at the expense of strength. This study evaluated the effect of adding a borate bioactive glass, previously shown to promote bone formation, on vancomycin elution from PMMA bone cement.

Methods: Five cement composites were made: three loaded with borate bioactive glass along with 0, 1, and 5 grams of vancomycin and two without any glass but with 1 and 5 grams vancomycin to serve as controls. The specimens were soaked in PBS. Eluate of vancomycin was collected every 24 hours and analyzed by HPLC. Orthopedic-relevant mechanical properties of each composite were tested over time.

Results: The addition of borate bioactive glass provided an increase in vancomycin release at Day 1 and an increase in sustained vancomycin release throughout the treatment period. An 87.6% and 21.1% increase in cumulative vancomycin release was seen for both 1g and 5g loading groups, respectively. Compressive strength of all composites remained above the weight-bearing threshold of 70 MPa throughout the duration of the study with the glass-containing composites showing comparable strength to their respective controls.

Conclusion: The incorporation of borate bioactive glass into commercial PMMA bone cement can significantly increase the elution of vancomycin. The mechanical strength of the cement-glass composites remained above 70 MPa even after soaking for 8 weeks, suggesting their suitability for orthopedic weight-bearing applications.

The multidisciplinary treatment of osteosarcoma of the proximal tibia: a retrospective study

Background

Survival and reconstruction constitute important challenges in multimodal treatment of osteosarcoma of the proximal tibia. The purpose of this study was to assess the efficacy and prognosis of neoadjuvant chemotherapy and custom-designed endoprosthetic arthroplasty.

Methods

A total of 69 patients with osteosarcoma of the proximal tibia were evaluated, including 43 males and 26 females, treated with multidisciplinary limb-salvage remedy from October 2003 to December 2013. They were at least 12 years old (mean, 20 years; range, 12–57 years). The gap between tumor and main artery/nerve was showed in MRI. Mean follow up was 69.5 months (range, 9–144 months). Kaplan-Meier survival curves were generated to assess prognosis and relapse rate. The initial symptoms and disease duration for each patient were recorded. Correlation analyses were performed for the association of various parameters with prognosis. Functional outcomes were evaluated using the Musculoskeletal Tumor Society (MSTS) guidelines after 6 months postoperatively, to analyze the relation between bone excision size and function recovery.

Results

The resection lengths measured intraoperatively ranged from 80 to 230 mm, and contained 3 cm of normal bone around the tumor. A total of 3 courses of preoperative chemotherapy were administered to all cases. At final follow-up, 1 case showed recurrence. Meanwhile, 8 patients (11.6%) died from lung metastasis. Post-operative infection occurred in 3 patients; 1 case was maintained with revision surgery. Two cases underwent amputation. The mean MSTS system score was 21.6.

Conclusions

The multidisciplinary treatment result in an overall positive outcome, with improved function.

How Long Does Antimycobacterial Antibiotic-loaded Bone Cement Have In Vitro Activity for Musculoskeletal Tuberculosis?

BACKGROUND

Antibiotic-loaded bone cement is accepted as an effective treatment modality for musculoskeletal tuberculosis. However, comparative information regarding combinations and concentrations of second-line antimycobacterial drugs, such as streptomycin and amoxicillin and clavulanic acid, are lacking.

QUESTIONS/PURPOSES

(1) In antibiotic-loaded cement, is there effective elution of streptomycin and Augmentin^® (amoxicillin and clavulanic acid) individually and in combination? (2) What is the antibacterial activity duration for streptomycin- and amoxicillin and clavulanic acid -loaded cement?

METHODS

Six different types of bone cement discs were created by mixing 40 g bone cement with 1 or 2 g streptomycin only, 0.6 g or 1.2 g Augmentin^® (amoxicillin and clavulanic acid) only, and a combination of 1 g streptomycin plus 0.6 g amoxicillin and clavulanic acid and 2 g streptomycin plus 1.2 g amoxicillin and clavulanic acid. Five bone discs of each type were incubated in phosphate buffered saline for 30 days with renewal of the phosphate buffered saline every day. The quantity of streptomycin and/or amoxicillin and clavulanic acid in eluates were measured by a liquid chromatography-mass spectrometry system, and the antimycobacterial activity of eluates against Mycobacterium tuberculosis H37Rv, were calculated by comparing the minimal inhibitory concentration of each eluate with that of tested drugs using broth dilution assay on microplate.

RESULTS

Streptomycin was detected in eluates for 30 days (in 1 g and 2 g discs), whereas 1.2 g amoxicillin and clavulanate eluted until Day 7 and 0.6 g amoxicillin and clavulanate until Day 3. All eluates in streptomycin-containing discs (streptomycin only, and in combination with amoxicillin and clavulanic acid) had effective antimycobacterial activity for 30 days, while amoxicillin and clavulanate-only preparations were only active until Day 14. The antimycobacterial activity of eluates of 2 g streptomycin plus 1.2 g amoxicillin and clavulanate were higher than those of discs containing 1 g streptomycin plus 0.6 g amoxicillin and clavulanate until Day 3, without differences (Day 3, 1 g streptomycin plus 0.6 g amoxicillin and clavulanate: 17.5 ± 6.85 ug/mL; 2 g streptomycin plus 1.2 g amoxicillin and clavulanate: 32.5 ± 16.77 ug/mL; p = 0.109). After Day 7, however, values of the two combinations remained no different than that of Day 30 (Day 30, 1 g streptomycin plus 0.6 g amoxicillin and clavulanate: 0.88 ± 0.34 ug/mL; 2 g streptomycin plus 1.2 g amoxicillin and clavulanate: 0.59 ± 0.94 ug/mL; p = 0.107).

CONCLUSIONS

Streptomycin, in the form of antibiotic-loaded bone cement, had effective elution characteristics and antimycobacterial effects during a 30-day period, whereas amoxicillin and clavulanate only had effective elution and antimycobacterial characteristics during the early period of this study. The two drugs did not interfere with each other during the elution test.

CLINICAL RELEVANCE

This research revealed that combinations of streptomycin and amoxicillin and clavulanate mixed with bone cement are effective for 30 days. Further trials to determine various different combinations of drugs are necessary to improve the effectiveness of treatments for musculoskeletal tuberculosis.

Combination of modified mixing technique and low frequency ultrasound to control the elution profile of vancomycin-loaded acrylic bone cement

OBJECTIVES

The objective of this study was to determine if combining variations in mixing technique of antibiotic-impregnated polymethylmethacrylate (PMMA) cement with low frequency ultrasound (LFUS) improves antibiotic elution during the initial high phase (Phase I) and subsequent low phase (Phase II) while not diminishing mechanical strength.

METHODS

Three batches of vancomycin-loaded PMMA were prepared with different mixing techniques: a standard technique; a delayed technique; and a control without antibiotic. Daily elution samples were analysed using flow injection analysis (FIA). Beginning in Phase II, samples from each mix group were selected randomly to undergo either five, 15, 45, or 0 minutes of LFUS treatment. Elution amounts between LFUS treatments were analysed. Following Phase II, compression testing was done to quantify strength. A-priori t-tests and univariate ANOVAs were used to compare elution and mechanical test results between the two mix groups and the control group.

RESULTS

The delayed technique showed a significant increase in elution on day one compared with the standard mix technique (p < 0.001). The transition point from Phase I to Phase II occurred on day ten. LFUS treatments significantly increased elution amounts for all groups above control. Delayed technique resulted in significantly higher elution amounts for the five-minute- (p = 0.004) and 45-minute- (p < 0.001) duration groups compared with standard technique. Additionally, the correlations between LFUS duration and total elution amount for both mix techniques were significant (p = 0.03). Both antibiotic-impregnated groups exhibited a significant decrease in offset yield stress compared with the control group (p < 0.001), however, their lower 95% confidence intervals were all above the 70 MPa limit defined by International Standards Organization (ISO) 5833-2 reference standard for acrylic bone cement.

CONCLUSION

The combination of a delayed mix technique with LFUS treatments provides a reasonable means for increasing both short- and long-term antibiotic elution without affecting mechanical strength.Cite this article: Dr. T. McIff. Combination of modified mixing technique and low frequency ultrasound to control the elution profile of vancomycin-loaded acrylic bone cement. Bone Joint Res 2016;5:26-32. doi: 10.1302/2046-3758.52.2000412.

Evaluation of Elution and Mechanical Properties of High-Dose Antibiotic-Loaded Bone Cement: Comparative "In Vitro" Study of the Influence of Vancomycin and Cefazolin

Use of antibiotic-loaded bone cements is one of the most effective methods for the prevention and treatment of prosthetic joint infection. However, there is still controversy about the optimal combination and doses of antibiotics that provide the maximum antimicrobial effect without compromising cement properties. In this study, vancomycin and cefazolin were added to a bone cement (Palacos R+G). Antibiotic release, fluid absorption, and mechanical properties were evaluated under physiological conditions. The results show that the type of antibiotic selected has an important impact on cement properties. In this study, groups with cefazolin showed much higher elution than those containing the same concentration of vancomycin. In contrast, groups with cefazolin showed a lower strength than vancomycin groups.

The effects of different mixing speeds on the elution and strength of high-dose antibiotic-loaded bone cement created with the hand-mixed technique

We evaluated the effects of the mixing speed of hand-mixed bone cement and the different phases of antibiotic mixing on the elution, mechanical properties, and porosity of antibiotic-loaded bone cement. Vancomycin-loaded Palacos LV bone cement was prepared at two hand-mixing speeds, normal and high-speed, and with antibiotic addition during three phases (directly mixing with the PMMA powder, in the liquid phase, and in the dough phase). The cumulative antibiotic elution over 15 days in the high-speed group was increased by 24% compared with the normal-speed group (P < 0.001). The delayed antibiotic addition produced higher vancomycin elution (P < 0.05), but no difference was observed between the liquid and dough phases (P > 0.05). Our study demonstrated that bone cement prepared with high-speed hand mixing and delayed antibiotic addition can exhibit increased vancomycin release.

Not all approved antibiotic-loaded PMMA bone cement brands are the same: ranking using the utility materials selection concept

In the literature on in vitro characterization of approved antibiotic-loaded poly(methyl methacrylate) bone cement brands, there is no information on the basis for selection of a given brand for use in cemented arthroplasties. This shortcoming is addressed in the present study. It involved determining four key properties (fatigue limit, fracture toughness, polymerization rate, and phosphate buffered saline diffusion coefficient) for six brands and then using the mean property values, in conjunction with a materials selection methodology, called the utility concept, to rank the brands. It is emphasized that the present work is an illustration of a rational approach to selection of a cement brand and, as such, the study findings are not intended to be recommendations regarding clinical use or otherwise of a brand.

Osteosarcoma around the knee treated with neoadjuvant chemotherapy and a custom-designed prosthesis

This article describes a novel approach using high-dose neoadjuvant chemotherapy with wide tissue resection and a specially designed artificial joint in 104 patients with stage IIB osteosarcoma near the knee. Sixty-four lesions were located at the distal femur, 39 at the proximal tibia, and 1 invaded the proximal tibia from the distal femur. Pathological fracture was present in 9 patients. Three courses of high-dose methotrexate, doxorubicin, and ifosfamide were administered preoperatively, and 6 courses were administered postoperatively. Preoperative radiographs and magnetic resonance images were obtained to determine the required tumor resection range and prosthesis size. Osteotomy of 3 cm of normal bone outside the tumor and wide resection of normal peripheral soft tissue were performed. Reconstruction with a rotary hinge or simple hinge prosthesis, as appropriate, was then performed. The Musculoskeletal Tumor Society 93 scoring system was used to evaluate limb function 6 months postoperatively. At final follow-up, recurrence, complication, survival, and amputation rates were 4%, 18%, 85%, and 4%, respectively. No recurrences were observed at the ends of amputated bones. Complications included infection (6%), nerve injury (3%), and prosthesis-related events (2% dislocation, 3% breakage, and 1% dislocation-related). Mean Musculoskeletal Tumor Society 93 score was 28 points, which indicated an excellent functional outcome. The low recurrence rate is attributed to the efficacy of the chemotherapy and the accuracy of the margin of resection.Effective chemotherapy reduces the risk of tumor metastasis and clarifies the tumor margin. Accurate identification of the resection margin reduces the risk of local recurrence.

Increasing the elution of vancomycin from high-dose antibiotic-loaded bone cement: a novel preparation technique

BACKGROUND

Antibiotic bone cement is commonly used in staged revision arthroplasty as well as the treatment of open fractures. Multiple factors affect antibiotic elution from bone cement. This study was performed to investigate the effect of two variables, the quantity of liquid monomer and the timing of antibiotic addition, on the ultimate elution of antibiotic from bone cement.

METHODS

Vancomycin-loaded Simplex P and SmartSet MV bone cement was prepared with three different methods: a common surgical technique, a mixing technique that doubled the amount of liquid monomer, and a novel technique that delayed antibiotic addition until after thirty seconds of polymerization. Cylinders of a standardized size were created from each preparation. The elution profiles of five cylinders from each preparation were measured over six weeks with use of high-performance liquid chromatography. Cylinders were tested in compression to quantify strength.

RESULTS

Delayed antibiotic addition resulted in significantly greater cumulative elution over six weeks (p < 0.0001), with minimal reduction in strength, compared with the other groups. Doubling the liquid monomer significantly reduced cumulative elution over six weeks compared with either of the other techniques (p < 0.0001). Vancomycin elution from Simplex P was 52%greater and vancomycin elution from SmartSet MV was 25% greater in the delayed-antibiotic-addition groups than it was in the corresponding standard surgical technique groups. The majority of the antibiotic was released over the first week in all groups. : High-dose-antibiotic bone cement prepared with delayed antibiotic addition increased vancomycin elution compared with the standard surgical preparation. Incorporating additional liquid monomer decreased vancomycin elution from high-dose-antibiotic cement. We recommend preparing high-dose-antibiotic bone cement with the delayed-antibiotic addition technique and not incorporating additional liquid monomer.

CLINICAL RELEVANCE

Both the relative volume of liquid monomer and the timing of antibiotic addition have substantial effects on the elution of antibiotic from bone cement.

Characterization of daptomycin-loaded antibiotic cement

Antibiotics are commonly mixed with polymethylmethacrylate (PMMA) cement to suppress severe periprosthetic infections associated with total joint arthroplasty. The relationship between antibiotic concentration and the resulting elution kinetics remains unclear. The purpose of this study was to characterize the release of daptomycin from PMMA cement and the subsequent effects on mechanical properties.Varying concentrations of daptomycin and tobramycin were vacuum mixed in commercially available PMMA and subjected to an in vitro elution period. High-performance liquid chromatography was used to quantify the concentration of the amount of daptomycin eluted at predetermined time points. Samples were subjected to compressive loading to analyze the effect of antibiotic concentration on cement mechanical properties. Daptomycin elution increased when initial tobramycin concentration was increased. Furthermore, the addition of antibiotics increased the compressive strength of the cement in the postelution period. The binary addition of tobramycin with daptomycin antibiotics modifies the elution and mechanical properties of PMMA bone cement. Based on the findings of our study, 2 g of daptomycin and 3.6 g of tobramycin per 40-g packet of cement should be used to promote daptomycin elution without sacrificing PMMA mechanical properties.