Use In Vertebroplasty Research Articles

METHODS FOR THE CHARACTERIZATION OF THE LONG-TERM MECHANICAL PERFORMANCE OF CEMENTS FOR VERTEBROPLASTY AND KYPHOPLASTY: CRITICAL REVIEW AND SUGGESTIONS FOR TEST METHODS

There is a growing interest towards bone cements for use in vertebroplasty and kyphoplasty, as such spine procedures are becoming more and more common. Such cements feature different compositions, including both traditional acrylic cements and resorbable and bioactive materials. Due to the different compositions and intended use, the mechanical requirements of cements for spinal applications differ from those of traditional cements used in joint replacement. Because of the great clinical implications, it is very important to assess their long-term mechanical competence in terms of fatigue strength and creep. This paper aims at offering a critical overview of the methods currently adopted for such mechanical tests. The existing international standards and guidelines and the literature were searched for publications relevant to fatigue and creep of cements for vertebroplasty and kyphoplasty. While standard methods are available for traditional bone cements in general, no standard indicates specific methods or acceptance criteria for fatigue and creep of cements for vertebroplasty and kyphoplasty. Similarly, a large number of papers were published on cements for joint replacements, but only few cover fatigue and creep of cements for vertebroplasty and kyphoplasty. Furthermore, the literature was analyzed to provide some indications of tests parameters and acceptance criteria (number of cycles, duration in time, stress levels, acceptable amount of creep) for possible tests specifically relevant to cements for spinal applications.

In vitro comparative assessment of the mechanical properties of PMMA cement and a GPC cement for vertebroplasty

AimsTo develop a Glass Polyalkenoate Cement that is suitable for vertebroplasty. MethodsTesting was carried out to assess the effect of gamma irradiation used for sterilisation, on the glass transition temperature as well as its mechanical properties, including compressive strength and biflexural strength in vivo as well as testing GPC and PMMA cements post injection in cadaveric human vertebral bone. ResultsThere was a trend to a higher failure load required for the GPC cement group compared to the current standard PMMA injected group but this was not statistically significant with this small sample size. ConclusionThe results are encouraging for future research to continue on GPC cements for use in vertebroplasty.

Software for radionuclide vertebroplasty

The problem of the software support for radionuclide vertebroplasty has been considered in general. Requirements to systems of preoperative preparation and postoperative analysis are described. The subject area (the vertebra operated on and its vicinity) is modeled using CT scans: a) precisely, based on voxel representation and b) approximately, for use in online interactive calculations. The voxel model is made in two versions: for dose and temperature calculation. The MCNP code is used for dose calculation. The emitter radionuclides were selected in serial calculations; and the best “candidates” have been identified for application in this procedure based on a set of characteristics. A code was developed for solving online both the “direct” problem (dose field calculation in the vicinity of the bone cement delivered with the preset radionuclide activity) and the “inverse” problem (calculation of the required radionuclide activity to be delivered in a specific localization close to the cement “kernel”). The temperature fields caused by polymerization of the bone cement have been calculated by means of thermal-hydraulic codes used in nuclear reactor design; these codes have been adapted for use in vertebroplasty based on the conducted problem-oriented experiments. Using internationally adopted methodologies for assessing the synergistic effects of radiation and heating on tissue, beam impact “enhancement ratios” have been obtained, and areas of radical and palliative therapeutic effects for the given vertebroplasty conditions have been defined. A beta-version of the code for the radionuclide vertebroplasty planning has been created based on calculated and experimental data.

Modification of dicalcium silicate bone cement biomaterials by using carboxymethyl cellulose

To ensure the operability of the clinical, the setting time is one of the most clinically vital factors. Sol–gel technique was used to prepare calcium silicate powders with different molar ratios of CaO/SiO2, and the calcium silicate bone cements (CSCs) were obtained in this study. Functional groups of powder and cements were analyzed by infrared spectroscopy (FT-IR). The doped cement was prepared using carboxymethylcellulose (CMC)-containing calcium silicate powder as solid phase and distilled water as liquid phase. Phase composition, morphology, setting time (St) and compressive strength (Cs) of the doped cement, after mixing with water, were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Gillmore needle and electronic universal material testing machine, respectively. In vitro mineralization of doped cement was investigated by SBF immersion test by soaking the samples individually in 10-ml of simulated body fluid (SBF) solution at 37°C for 0, 1, 3, 7 and 15days (d), respectively. The results indicated that the doped cement with 0.10% CMC possessed shorter setting time, higher compressive strength, and desirable bioactivity that makes it an attractive choice for use in vertebroplasty and bone filling surgery.

Two novel high performing composite PMMA-CaP cements for vertebroplasty: An ex vivo animal study

There is a growing body of the literature on new cement formulations that address the shortcomings of PMMA bone cements approved for use in vertebroplasty (VP) and balloon kyphoplasty (BKP). The present study is a contribution to these efforts by further characterization of two pre-mixed CaP filler-reinforced PMMA bone cements intended for VP; namely, PMMA-HA and PMMA-brushite cements. Each of these cements showed acceptable levels of various properties determined in porcine vertebral bodies. These properties included radiographic contrast, maximum exotherm temperature setting time, cement extravasation, stiffness change after fatigue loading, change of VB height after fracture following fatigue loading, and interdigitation. Each property value was comparable to or better than that for a PMMA bone cement approved for use in BKP. Thus, the results for the composite bone cements are promising.

Biocompatibility of calcium phosphate bone cement with optimized mechanical properties

The broad aim of this work was to investigate and optimize the properties of calcium phosphate bone cements (CPCs) for use in vertebroplasty to achieve effective primary fixation of spinal fractures. The incorporation of collagen, both bovine and from a marine sponge (Chondrosia reniformis), into a CPC was investigated. The biological properties of the CPC and collagen–CPC composites were assessed in vitro through the use of human bone marrow stromal cells. Cytotoxicity, proliferation, and osteoblastic differentiation were evaluated using lactate dehydrogenase, PicoGreen, and alkaline phosphatase activity assays, respectively. The addition of both types of collagen resulted in an increase in cytotoxicity, albeit not to a clinically relevant level. Cellular proliferation after 1, 7, and 14 days was unchanged. The osteogenic potential of the CPC was reduced through the addition of bovine collagen but remained unchanged in the case of the marine collagen. These findings, coupled with previous work showing that incorporation of marine collagen in this way can improve the physical properties of CPCs, suggest that such a composite may offer an alternative to CPCs in applications where low setting times and higher mechanical stability are important. © 2015 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. 104B:308–315, 2015.

Direct and interactive influence of explanatory variables on properties of a calcium phosphate cement for vertebral body augmentation

We used the response surface methodology to investigate the direct and interactive effects of three explanatory variables on three properties of a calcium phosphate cement (CPC) for use in vertebroplasty (VP) and balloon kyphoplasty (BKP). The variables were poly(ethylene glycol) content of the cement liquid (PEG), powder-to-liquid ratio (PLR), and the amount of Na2HPO4 added to an aqueous solution of 4 wt/wt% poly(acrylic acid) (as the cement liquid) (SPC). The properties were injectability (I), final setting time (F), and 5-day compressive strength (UCS). We found that (1) there was an interactive effect between the variables on I and F but not on UCS; (2) the maximum I (98%) was obtained with PEG = 20 wt/wt% and PLR = 2 g mL(-1); (3) F = 15 min (the proposed optimum value for a CPC for use in VP and BKP) was obtained with PEG = 4 wt/wt% and PLR = 2.9 g mL(-1); and (4) the maximum UCS (39 MPa) was obtained with SPC = 0 and PLR = 3.5 g mL(-1).

Bactericidal strontium-releasing injectable bone cements based on bioactive glasses

Strontium-releasing injectable bone cements may have the potential to prevent implant-related infections through the bactericidal action of strontium, while enhancing bone formation in patients suffering from osteoporosis. A melt-derived bioactive glass (BG) series (SiO2–CaO–CaF2–MgO) with 0–50% of calcium substituted with strontium on a molar base were produced. By mixing glass powder, poly(acrylic acid) and water, cements were obtained which can be delivered by injection and set in situ, giving compressive strength of up to 35 MPa. Strontium release was dependent on BG composition with increasing strontium substitution resulting in higher concentrations in the medium. Bactericidal effects were tested on Staphylococcus aureus and Streptococcus faecalis; cell counts were reduced by up to three orders of magnitude over 6 days. Results show that bactericidal action can be increased through BG strontium substitution, allowing for the design of novel antimicrobial and bone enhancing cements for use in vertebroplasty or kyphoplasty for treating osteoporosis-related vertebral compression fractures.

A highly radiopaque vertebroplasty cement using tetraiodinated o-carborane additive

Bone cements for vertebroplasty must have a much better radiocontrast level than cements for knee or hip arthroplasty. This is generally accomplished by adding a relatively large portion of BaSO4, although this affects the physical-mechanical and biological properties of the cement. This prompted us to develop an alternative radiopaque cement, on the basis of unique highly radiopaque methacrylic microspheres. These contain iodine in two modalities: (i) covalently linked to the methacrylic polymer, and (ii) as constituent of the stable tetraiodocarborane 8,9,10,12-I4-1,2-closo-C2B10H8. The total iodine content in these particles exceeded 30% by mass. These radiopaque microspheres as well as the cement made thereof were characterized extensively, e.g., by scanning electron microscopy, X-ray contrast measurements, X-ray photoelectron spectroscopy, measurements of compressive strength, infrared spectroscopy, and solid state 11B{1H} NMR spectroscopy. Furthermore, the new cement was subjected to several biocompatibility tests in vitro. The results show that the new bone cement fulfills all physico-chemical criteria for use in vertebroplasty. Further data on the cement’s biocompatibility (in vitro), as well as on the handling parameters and doughviscosity, indicate that this material has a potential to become an alternative to vertebroplasty cements with a high BaSO4 content. The new cement provides two significant advantages: (i) controlled viscosity in the dough phase, which facilitates precise injection during the vertebroplasty procedure; (ii) excellent structural stability, which precludes leaching of contrast post-implantation.

An ex vivo exothermal and mechanical evaluation of two-solution bone cements in vertebroplasty

Background context Previous ex vivo studies showed that the properties of commercial cements modified for use in vertebroplasty are not optimal and are associated with several drawbacks, including high exothermic reaction, low cement viscosity and consequent extravasation, and unpredictable wait time after cement preparation. Additionally, strength and stiffness restoration are controversial varying with the cement type, volume injected, and technique used. Purpose To investigate maximum polymerization temperatures and mechanical performance of novel two-solution bone cement (TSBC) modified by the addition of cross-linked poly(methyl methacrylate) nanospheres (η-TSBC) and microspheres (μ-TSBC) in a cadaver vertebroplasty model in comparison to a commercially available cement (KyphX). To study the viability of application of these novel cement formulations in the treatment of vertebral compression fractures. Study design/setting Ex vivo biomechanical and exothermal evaluation of TSBCs using cadaveric vertebral bodies (VBs). Methods Thirty-one cadaveric vertebrae (age, 74±2 years; T score, −1.5±0.5) were disarticulated. Thirteen vertebrae were assigned into three groups and instrumented with thermocouples positioned midbody along the intersection of the midsagittal and midcoronal axes, as well as along the intersection of the midsagittal axis and posterior VB wall. After equilibration at 37°C, 5 mL of cement was injected and temperatures were recorded for 1 hour. The groups were injected with η-TSBC, μ-TSBC, or KyphX. The remaining 18 vertebrae were biomechanically tested. After randomization into three groups, each specimen was fractured in compression and stabilized with 5 mL of each cement type. Each specimen was then retested in axial compression. Results Temperatures in the central region of the vertebrae were significantly lower (p<.05) when injected with η-TSBC (44°C) in comparison to KyphX (75°C) and μ-TSBC (64°C). A significant difference was not detected between the pre- and postcementing strength (p>.05) of the three groups. There was no significant difference between the average values of stiffness among the cements (p>.05), however there was a significant difference between intact and treated stiffness (p<.05). Conclusions The TSBC cements decreased the local temperature within the VB while providing similar mechanical strength when compared with vertebrae treated with KyphX.

Evaluation of two novel aluminum-free, zinc-based glass polyalkenoate cements as alternatives to PMMA bone cement for use in vertebroplasty and balloon kyphoplasty

Vertebroplasty (VP) and balloon kyphoplasty (BKP) are now widely used for treating patients in whom the pain due to vertebral compression fractures is severe and has proved to be refractory to conservative treatment. These procedures involve percutaneous delivery of a bolus of an injectable bone cement either directly to the fractured vertebral body, VB (VP) or to a void created in it by an inflatable bone tamp (BKP). Thus, the cement is a vital component of both procedures. In the vast majority of VPs and BKPs, a poly(methyl methacrylate) (PMMA) bone cement is used. This material has many shortcomings, notably lack of bioactivity and very limited resorbability. Thus, there is room for alternative cements. We report here on two variants of a novel, bioactive, Al-free, Zn-based glass polyalkenoate cement (Zn-GPC), and how their properties compare to those of an injectable PMMA bone cement (SIMPL) that is widely used in VP and BKP. The properties determined were injectability, radiopacity, uniaxial compressive strength, and biaxial flexural modulus. In addition, we compared the compression fatigue lives of a validated synthetic osteoporotic VB model (a polyurethane foam cube with an 8 mm-diameter through-thickness cylindrical hole), at 0-2300 N and 3 Hz, when the hole was filled with each of the three cements. A critical review of the results suggests that the performance of each of the Zn-GPCs is comparable to that of SIMPL; thus, the former cements merit further study with a view to being alternatives to an injectable PMMA cement for use in VP and BKP.

New injectable and radiopaque antibiotic loaded acrylic bone cements

The use of antibiotic loaded bone cements (ALBCs) has become a common clinical practice in the prevention and treatment of prosthesis-related infections. However, due to antibiotic resistance, there is a general interest in broadening the antibacterial spectrum of currently used drugs. The aim of this work is to formulate ALBCs for specific use in vertebroplasty and kyphoplasty, and to study the effect of the addition of ciprofloxacin alone and in combination with vancomycin on some properties of the cement. The cements were formulated using bismuth salicylate as the radiopacifier. The setting properties, residual monomer content, release of antibiotics, rheological behavior, injectability, and mechanical properties of these formulations were studied. They showed long setting times and low curing temperatures. From the release studies, antibacterial properties are assumed because the concentration of released antibiotic was higher than the minimum effective. Although the experimental cements had slightly reduced mechanical properties, the other alterations shown were negligible.

In Vitro Biomechanical Testing of Two Injectable Materials for Vertebroplasty in Different Synthetic Bones

Two different injectable materials, intended for use in vertebroplasty (VP) treatments of fractured vertebras, were tested in an in vitro bone model. The materials tested were an experimental bioceramic material based on calcium aluminate manufactured by Doxa AB, and Vertebroplastic, a PMMA based material manufactured by DePuy Acromed. The model was earlier developed by others and has been found valid for testing of materials intended for PVP. The model offers alternative data to traditional compressive and diametral tensile testing by adding the infiltration of material into synthetic cancellous bone. Five different synthetic bones with different porosity and pore structure were tested. The results show that for the PMMA the infiltration pattern of the different bones tested seems to have no influence. The material deforms plastically and displays about the same strength in all bones tested. For the bioceramic, linear elastic, material however there is a difference. In the more porous bones, where the material infiltrate the pores and creates a test body with a large amount of crack initiation points, the material displays lower strength compared to that of the more solid bones.

The biocompatibility and osteoconductivity of a cement containing β–TCP for use in vertebroplasty

A new composite bone cement designated "G2B1" was developed for percutaneous transpedicular vertebroplasty. G2B1 contains beta tricalcium phosphate particles and methylmethacrylate-methylacrylate copolymer as the powder components, and methylmethacrylate, urethane dimethacrylate, and tetrahydrofurfuryl methacrylate as the liquid components. Biocompatibility and osteoconductivity were evaluated using scanning electron microscopy, contact microradiography, and Giemsa surface staining 4, 8, 12, 26, and 52 weeks after implantation into rat tibiae. To evaluate osteoconductivity, affinity indices (%) were calculated. Scanning electron microscopy and contact microradiography revealed that bone contact with G2B1 was attained within 4 weeks (affinity index: 50.2 +/- 11.8 at 4 weeks) and at most of the margin within 26 weeks (affinity index: 87.4 +/- 7.2 at 26 weeks). Specifically, G2B1 contacted bone via a wide calcium-phosphate-rich layer, and its degradation started within 8 weeks, mainly in the marginal area. Giemsa surface staining showed that there was almost no inflammatory reaction around the G2B1. These results indicate that G2B1 is a biocompatible and osteoconductive bone cement.

The biomechanical evaluation of calcium phosphate cements for use in vertebroplasty

The authors evaluate the biomechanical properties of vertebral bodies (VBs) stabilized with calcium phosphate (CaP) cements for use in vertebroplasty in comparison with polymethylmethacrylate (PMMA). In the first phase of the study, 73 VBs (T3-L2; thoracic region [T3-8] and thoracolumbar region [T9-L2]) were collected from seven fresh human cadavers. Compression tests were performed before and after vertebroplasty using PMMA (compression strength 80 MPa) and three kinds of CaP cements-CaP1 (5 MPa), CaP2 (20 MPa), and CaP3 (50 MPa). The authors compared the maximal compression loads (MCLs) and stiffness before and after vertebroplasty in each of the four cement groups. In the second phase of the study, 18 paired spinal units (PSUs) were collected from three fresh human cadavers, and the authors injected two types of cement selected from the first phase of the study into the lower level of six PSUs. They compared the MCLs of the untreated and two treated groups (there were six PSUs in each type of group) to analyze the tendency of inducing compression fractures in the upper level of the PSUs. The MCLs of the PMMA-injected vertebrae were significantly increased after vertebroplasty. The MCL levels of the CaP3-injected vertebrae and the CaP2-injected thoracolumbar vertebrae were decreased from those of untreated vertebrae without being significant. The MCLs of CaP1-injected vertebrae and CaP2-injected thoracic vertebrae were significantly decreased after vertebroplasty. The stiffness of all cement groups was decreased after vertebroplasty compared with initial stiffness, significantly so in all three thoracic CaP groups. In the second compression test with PSUs, the MCLs of the CaP2- and CaP3-injected PSUs were not significantly different from those of the untreated control PSUs. The CaP3-injected vertebrae restored the MCLs of human vertebrae closer to their initial levels than the PMMA-injected vertebrae did. The CaP2- and CaP3-injected PSUs showed no tendency to induce compression fractures in adjacent VBs.

Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty

For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (T(max)), a setting time (t(set)) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, T(max), t(set), complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 microm) to the small ones (of mean diameter 69.7 microm) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable.

Injectable bone cements for use in vertebroplasty and kyphoplasty: State‐of‐the‐art review

Vertebroplasty (VP) and kyphoplasty (KP) are minimally invasive surgical procedures that have recently been introduced for the medical management of osteoporosis-induced vertebral compression fractures. The aim of VP is to stabilize the fractured vertebral body, while the goals of KP are to stabilize the fractured vertebral body and to restore its height to as near its prefracture level as possible. Both procedures involve injection of the setting dough of an injectable bone cement (IBC) into the fractured vertebral body, thereby highlighting the indispensable role that the IBC plays. Although there is a very large literature on IBCs, no detailed critical review of it has been published. Such a review is the subject of the present work, which is in seven parts. The review opens with a succinct introduction to VP and KP. The topics covered in the parts that follow are: (1) a listing of the 18 most desirable properties of an IBC (e.g., easy injectability, high radiopacity, and a resorption rate that is neither too high nor too low); (2) descriptions of the four classes of IBCs (calcium phosphates, acrylic bone cements, calcium sulfates, and composites); (3) concerns that have been raised with regard to the use of IBCs (such as the potential for thermal necrosis of tissue at the peri-augmentation site, when an acrylic bone cement is used); (4) explicative summaries of the main findings of literature studies on the influence of nine factors (such as powder particle size, powder-to-liquid ratio, and the method used to mix the powder and the liquid) on the values of various properties of IBCs; (5) explicative summaries of the main findings of literature studies on five fundamental matters, such as the aging mechanism of the powder, the thermokinetics of a setting dough, and the influence of the type of IBC used on various ex vivo biomechanical performance measures of VP- and KP-augmented vertebral bodies; and (6) descriptions of topics in six areas for future research, such as the determination of an overall index of the fatigue performance of an IBC and the development of internationally recognized standardized testing protocols to employ when a synthetic cancellous bone void model is used in the rapid in vitro screening of IBCs. The review ends with a summary of the most salient points and observations made.

Vertebroplasty for osteoporotic vertebral compression fractures

Vertebroplasty for osteoporotic vertebral compression fractures is a minimally invasive procedure which could provide immediate pain relief by injecting PMMA into the vertebral body percutaneously. Kyphoplasty, which is designed to restore the vertebral height by inflating balloon, has recently been developed and the excellent early clinical results were reported. Calcium phosphate cement may have potential advantages over the PMMA for the use in vertebroplasty or kyphoplasty.

Biomechanical evaluation of a new bone cement for use in vertebroplasty.

Comparative ex vivobiomechanical study. To determine the strength and stiffness of osteoporotic vertebral bodies subjected to compression fractures and subsequently stabilized via bipedicular injection of one of two bone cements: one is a commercially available polymethylmethacrylate (Simplex P) and one is a proprietary glass-ceramic-reinforced BisGMA/BisEMA/TEGDMA matrix composite that is being developed for use in vertebroplasty (Orthocomp). Osteoporotic compression fractures present diagnostic and therapeutic challenges for the clinician. Vertebroplasty, a new technique for treating such fractures, stabilizes vertebral bodies by injection of cement. Little is known, however, about the biomechanics of this treatment. Five vertebral bodies (L1-L5) from each of four fresh spines were harvested from female cadavers (age, 80 +/- 5 years), screened for bone density using DEXA (t = -3.4 to -6.4), disarticulated, and compressed in a materials testing machine to determine initial strength and stiffness. The fractures then were repaired using a transpedicular injection of either Orthocomp or Simplex P and recrushed. For both cement treatments, vertebral body strength after injection of cement was significantly greater than initial strength values. Vertebral bodies augmented with Orthocomp recovered their initial stiffness; however, vertebral bodies augmented with Simplex P were significantly less stiff than they were in their initial condition. Augmentation with Orthocomp results in similar or greater mechanical properties compared with Simplex P, but these biomechanical results have yet to be substantiated in clinical studies.