Preparation Of Bone Cement Research Articles

Setting Properties along Bone Cement Preparation and its Effect on Material Properties

Bone cement is a material used in many orthopedic surgeries. Polymethyl Methacrylate (PMMA) is one of the acrylic-based bone cement materials. PMMA will be mixed with an activator (N, N-Dimethyl-p-toluidine (DMPT)), initiator (Benzoyl Peroxide (BPO)), radiopacifier / filler (BaSO4), and Methyl Methacrylate monomer. Once the materials were mixed, the activator react with the initiator to form radicals and activate the bulk polymerization reaction between the MMA monomer and PMMA molecules. The bulk polymerization reaction occurs exothermically and increases the bulk temperature. Barium sulfate (BaSO4) is an inorganic compound that can be acted as both radiopacifier and filler in bone cement. The specific objective of this study was to describe the effect of BaSO4 in bone cement composite formation. The solid material; PMMA, BPO, and BaSO4 were mixed firstly. The liquid portions; N, N-Dimethyl-p-toluidine (DMPT), and MMA were mixed and then poured into the solids one in a stainless-steel bowl. The bulk temperature was recorded after a one-minute mixing process. The samples were characterized by Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). The highest setting temperature and setting time were 107.3°C and 10.6 min which was obtained in BaSO4 content variables of 7% and 11%, respectively. The average molecular weight of the samples was 561.5-1,332.0 kDa. From the DSC result, the glass temperature of the samples was 119.17-119.87°C.

Application of the induced membrane technique of tibia using extracorporeal vs. intracorporeal formation of a cement spacer: a retrospective study

BackgroundThere were two ways of preparing the cement spacer: intracorporeal and extracorporeal formation. This study aimed to investigate the outcomes of extracorporeal vs. intracorporeal formation of a spacer using the induced membrane technique (IMT) for repairing bone defects of the tibia.MethodsSixty-eight patients with tibial defects treated with IMT were analyzed retrospectively. According to the mode of bone cement preparation, patients were divided into intracorporeal and extracorporeal groups (36 vs. 32 respectively). All patients were followed up for 12–48 months (average 18.7 months). The time interval between the first and second stages, the time required to remove the spacer, injury of the IM or bone ends, bone healing and infection control, as well as the functional recovery (Johner—Wruhs scoring), were compared.ResultsThere was no significant difference in the preoperative data between the two groups (P > 0.05). There was no significant difference in the time interval (12.64 ± 4.41vs. 13.22 ± 4.96 weeks), infection control (26/28 vs. 20/23), bone healing time (7.47 ± 2.13vs. 7.50 ± 2.14 mos), delayed union (2/36 vs. 2/32), nonunion (2/36 vs. 1/32), an excellent or good rate of limb functional recovery (30/36 vs. 26/32) between the intracorporeal and extracorporeal groups (P > 0.05). However, the time required to remove (3.97 ± 2.34 min) was longer and the injury of IM or bone ends (28/36) was greater in the intracorporeal group than those in the extracorporeal group (0.56 ± 0.38 min and 1/32, respectively), showing a significant difference (P < 0.05).ConclusionBoth approaches were shown to have similar effects on bone defect repair and infection control. However, intracorporeal formation had advantages in terms of additional stability, while extracorporeal formation had advantages in terms of removal. Therefore, the specific method should be selected according to specific clinical needs. We recommended the extracorporeal or the modified extracorporeal formation in most cases.

364 A Novel Preparation of Bone Cement for Vertebroplasty: Can Strontium Folate Improve the Mechanical and Biological Properties of Calcium Phosphate Cement?

Abstract Aim Bone cements currently used for vertebral body augmentation procedures lack biological properties that allow them to osseointegrate. Strontium folate (SrFo) has been shown to increase the viability of human osteoblast (HOb) cells. The potential of a novel preparation of calcium phosphate cement (CPC) with added SrFo is explored to investigate whether SrFo can increase its biocompatibility. Method Brushite-forming CPCs with 0% (negative control) and 5% and 10% weight-weight additions of SrR (positive control) and SrFo were formulated. Initial (Ti) and final (Tf) setting times were measured. Mechanical analyses included ultimate compressive strength and plane strain fracture toughness. Topography and distribution analyses occurred during materials characterisation and in vitro analysis using scanning electron microscopy (SEM). Results There was no significant difference in the Ti between the CPCs, but significantly greater Tf for all SrFo-CPCs. There was no significant difference in the compressive strength between the CPCs, but a significantly decreased fracture toughness in all SrFo-CPCs. SEM revealed non-homogeneous structures in all SrFo-CPCs. Whilst the pH of the HOb cell culture medium remained the same for all CPCs, the proportion of dead cells was significantly higher than that of alive cells. Conclusions The addition of SrFo did not produce any significant differences in the material characteristics of the cements, nor the in vitro properties, except for a prolonged setting time. Future studies should seek to determine the osteogenic nature of SrFo by altering the formulation of the CPCs to a non-toxic preparation, such as apatite-forming cements which are known to have superior mechanical properties.

Impact of cobalt incorporation on the mineralization of calcium phosphate

Calcium phosphate in the presence of cobalt ions were mineralized using gel technique. The presence of cobalt in the gel medium enhances the growth of di-calcium phosphate crystals and it is found to be concentration dependent of the dopant. The crystals were modified from platy to dendritic on increasing the cobalt concentration. The XRD pattern confirms the phase of the crystals to be DCPD with variation in the peak intensity. The FT-IR spectrum confirms the presence of functional groups such as stretching and bending vibrations P-O. The presence of cobalt in the gel medium promoted the formation of apatite like structures on the surface of the DCPD crystals. The presence of elements (Ca, P, O and Co) in the crystals was confirmed through EDX analysis. The formation of apatite in an additives free medium like SBF solution suggests that cobalt incorporated DCPD is highly bioactive and could be suitable for the preparation of bone cements.

RADIOACTIVE CEMENT OF PMMA AND HAP-Sm-153, Ho-166, OR RE-188 FOR BONE METASTASIS TREATMENT.

ABSTRACTPolymethylmetacrylte (PMMA) is used in the fields of dentistry and biomedicine as a constituent of bone cements. Hydroxyapatite (HAp) is a bioceramic produced naturally in the bones. PMMA and HAp are fundamental constituents in the preparation of bone cements. Bisphosphonates have also been used as radiopharmaceutical in dental implants and nuclear medicine, or as palliative systemic treatment for pain reduction in bone metastasis. Vertebroplasty and kyphoplasty are bone cement-based techniques used in orthopedics, being minimally invasive procedures with low risks of infections, applied in osteoporosis and high-impact fractures. Recently, Núcleo de Radiações Ionizantes da Universidade Federal de Minas Gerais proposed a synthetic composite of M-HAp with a metallic nuclide M. After irradiation, M-HAp was added to PMMA, compounding a radioactive bone cement that can recover bone body stabilization, pasting microfractures and recomposing the anatomy and functionality of the affected parts by the compression of bone metastases, with possible pain reduction through quick radiation-induced decompression. Computational dosimetric models, and the synthesis and characterization of bioceramics that incorporate Re-188, Ho-166, or Sm-153 have demonstrated the benefits of these biometrics as promising alternative therapies, mainly from their ability to maintain the ionization in the bone structure, thereby sparing the spinal cord. This article presents a review on this topic. Level of Evidence V, Expert Opinion.

Masquelet technique: The effect of altering implant material and topography on membrane matrix composition, mechanical and barrier properties in a rat defect model

The Masquelet technique is a surgical procedure to regenerate segmental bone defects. The two-phase treatment relies on the production of a vascularized foreign-body membrane to support bone grafts over three times larger than the traditional maximum. Historically, the procedure has always utilized a bone cement spacer to evoke membrane production. However, membrane formation can easily be effected by implant surface properties such as material and topology. This study sought to determine if the membrane’s mechanical or barrier properties are affected by changing the spacer material to titanium or roughening the surface finish. Ten-week-old, male Sprague Dawley rats were given an externally stabilized, 6 mm femur defect which was filled with a pre-made spacer of bone cement (PMMA) or titanium (TI) with a smooth (∼1 μm) or roughened (∼8 μm) finish. After 4 weeks of implantation, the membranes were harvested, and the matrix composition, tensile mechanics, shrinkage, and barrier function was assessed. Roughening the spacers resulted in significantly more compliant membranes. TI spacers created membranes that inhibited solute transport more. There were no differences between groups in collagen or elastin distribution. This suggests that different membrane characteristics can be created by altering the spacer surface properties. Surgeons may unknowingly effecting membrane formation via bone cement preparation techniques.

Effect of process variables on the preparation of artificial bone cements

The present work concerns the preparation of bone cements based on poly(methyl methacrylate) (PMMA), used mainly for prosthesis fixation and cavity filling for correction of human bone failures. A typical bone cement recipe contains methyl methacrylate, which polymerizes in situ during cement application. An inherent problem of this reaction is the large amount of heat released during the cement preparation, which may lead to irreparable damage of living tissues. Optimization of PMMA-based bone cement recipes is thus an important step towards safe and reliable clinical usage of these materials. Important process variables related to the reaction temperature profile and the mixing of the recipe constituents were studied in order to allow for the adequate production of bone cements. It is shown that the average molar mass and size of the PMMA particles used in the production of the bone cement, as well as incorporation of radiopaque contrast, co-monomers and fillers into the bone recipe play fundamental roles in the course of the polymerization reaction. Furthermore, the injection vessel geometry may interfere dramatically with the temperature profile and the time for its occurrence. Finally, it has been observed that the morphology of the PMMA particles strongly affects the mixing of the bone cement components.

Grafting of nanospherical PMMA brushes on cross-linked PMMA nanospheres for addition in two-solution bone cements

Poly(methyl methacrylate) (PMMA) brushes were grafted to the surface of cross-linked PMMA nanospheres for use as the polymer phase in the preparation of the two-solution bone cement. PMMA chains grafted on the core of the cross-linked PMMA nanostructures were hypothesized to impart viscosity to the cement mixture, while providing entanglements with the matrix chains formed during cement cure. The first goal of this study was to develop a novel synthetic strategy to decorate the surface of nanoparticles with functional groups that allowed for grafting of PMMA brushes via radical polymerization. The grafting reactions were performed at specific combinations of monomer and initiator to produce a range of molecular weights adequate for the preparation of bone cements. The second goal was to investigate the ability of this novel methodology to produce high graft densities on the core surface from the analysis of the hydrodynamic properties of brushes. The synthetic pathway discussed enabled the synthesis of brushes with high graft densities and molecular weights tuned to provide optimal viscosities for preparation of brush-containing two-solution bone cements.

Pre-Packed Vacuum Bone Cement Mixing Systems. A Further Step in Reducing Methylmethacrylate Exposure in Surgery

Polymethylmethacrylate bone cements are widely used in orthopaedic and trauma surgery as well as in dentistry. The toxic side effects of inhaled methylmethacrylate (MMA) fumes generated during mixing have been well studied. Vacuum cement mixing systems have been shown to reduce the risk of airborne MMA significantly compared to handmixing. In an effort to further reduce MMA exposure, the latest generation of mixing devices are pre-packed with the ingredients and thus allow preparation in nearly closed circuits. Until now, there has been no study proofing the efficacy of those systems in protecting theatre staff from MMA vapours. A pre-packed vacuum mixing system (Optipac®) was compared with two standard systems (Palamix® and Easymix®) regarding MMA emission. The latter systems require loading with the bone cement compounds prior to mixing. Following a standardized procedure, 10 mixes were performed with each system and the emission of MMA vapours in the breathing zone was recorded using photoionization detection over a period of 3 min. The mean MMA exposure was reduced when using the pre-packed system compared to the devices that require filling with the components. The highest emission peaks were recorded during the mixing and preparation steps in all systems. Modern pre-packed vacuum mixing systems further help to reduce the occupational hazards created by bone cement preparation. However, MMA fumes can still be detected using this technique. Although this is an important step in reducing MMA exposure in the operating theatre, further technical effort has to be taken to eliminate the continuous leakage of monomer from the devices while mixing and to minimize necessary manipulation for final delivery.

A-mode ultrasound-based intra-femoral bone cement detection and 3D reconstruction in RTHR

Due to the difficulty of determining the 3D boundary of the cement-bone interface in Revision Total Hip Replacement (RTHR), the removal of the distal intra-femoral bone cement can be a time-consuming and risky operation. Within the framework of computer- and robot-assisted cement removal, the principles and first results of an automatic detection and 3D surface reconstruction of the cement-bone boundary using A-mode ultrasound are described. Sound propagation time and attenuation of cement were determined considering different techniques for the preparation of bone cement, such as the use of a vacuum system (Optivac®, Biomet). A laboratory setup using a rotating, standard 5-MHz transducer was developed. The prototype enables scanning of bisected cement-prepared femur samples in a 90° rotation range along their rotation axis. For system evaluation ex vivo, the distal femur of a human cadaver was prepared with bone cement and drilled (Ø 10 mm) to simulate the prosthesis cavity in a first approximation. The sample was cut in half and CT scanned (0.24 mm resolution; 0.5 mm distance; 0.5 mm thickness), and 3D voxel models of the manually segmented bone cement were reconstructed, providing the ground truth. Afterwards, 90° segments of each ex-vivo sample were scanned by the A-mode ultrasound system. To obtain better ultrasound penetration, we used coded signal excitation and pulse compression filtering. A-mode ultrasound signal detection, filtering and segmentation were accomplished fully automatically. Subsequently, 3D voxel models of each sample were calculated. Accuracy evaluation of the measured ultrasound data was performed by ICP matching of each ultrasound dataset (∼8000 points) to the corresponding CT dataset and calculation of the residual median distance error between the corresponding datasets. Prior to each ICP matching, an initial pre-registration was calculated using prominent landmarks in the corresponding datasets. This method yielded a median distance error in the region of 0.25 mm for the cement-bone interface in both femur halves.

Control of Methyl Methacrylate During the Preparation of Orthopedic Bone Cements

The use of methyl methacrylate (MMA) bone cement during orthopedic procedures has been seen as a potential exposure hazard to health care professionals. However, that assessment is based on a number of investigations with problems in experimental design, analysis, and data interpretation. The current investigation quantified differences in MMA vapors produced during the preparation of competing bone cements using various methods of preparation. Unlike previous investigations, this effort employs modern validated sampling and analytical methods, and considers the affect of censored results. Measurements of sufficient quality and number were collected to allow for a statistical treatment of the data. The ability of two controlled preparation techniques to reduce MMA emissions were compared with a traditional open container. The results confirmed that the preparation of bone cement releases MMA vapors into the breathing zone of the preparer. One preparation technique (Stryker Bowl) controlled emissions during mixing and curing and affected a 73% reduction in measured MMA concentrations. In addition to mixing and curing, the second technique (UltraMix System) also controlled the MMA during pouring of the monomer and affected a 90% reduction in MMA concentrations. An ANOVA test of interaction indicates that the reductions are attributable to the preparation technique regardless of the type of cement being used. Both a Fisher's PLSD and Games/Howell post hoc test of the results indicate that the mean differences between the uncontrolled open container and the controlled preparation techniques are significant (p < 0.05).

A-mode ultrasound-based intra-femoral bone cement detection and 3D reconstruction in RTHR

Due to the difficulty of determining the 3D boundary of the cement-bone interface in Revision Total Hip Replacement (RTHR), the removal of the distal intra-femoral bone cement can be a time-consuming and risky operation. Within the framework of computer- and robot-assisted cement removal, the principles and first results of an automatic detection and 3D surface reconstruction of the cement-bone boundary using A-mode ultrasound are described. Sound propagation time and attenuation of cement were determined considering different techniques for the preparation of bone cement, such as the use of a vacuum system (Optivac®, Biomet). A laboratory setup using a rotating, standard 5-MHz transducer was developed. The prototype enables scanning of bisected cement-prepared femur samples in a 90° rotation range along their rotation axis. For system evaluation ex vivo, the distal femur of a human cadaver was prepared with bone cement and drilled (Ø 10 mm) to simulate the prosthesis cavity in a first approximation. The sample was cut in half and CT scanned (0.24 mm resolution; 0.5 mm distance; 0.5 mm thickness), and 3D voxel models of the manually segmented bone cement were reconstructed, providing the ground truth. Afterwards, 90° segments of each ex-vivo sample were scanned by the A-mode ultrasound system. To obtain better ultrasound penetration, we used coded signal excitation and pulse compression filtering. A-mode ultrasound signal detection, filtering and segmentation were accomplished fully automatically. Subsequently, 3D voxel models of each sample were calculated. Accuracy evaluation of the measured ultrasound data was performed by ICP matching of each ultrasound dataset (∼8000 points) to the corresponding CT dataset and calculation of the residual median distance error between the corresponding datasets. Prior to each ICP matching, an initial pre-registration was calculated using prominent landmarks in the corresponding datasets. This method yielded a median distance error in the region of 0.25 mm for the cement-bone interface in both femur halves.

Modeling Methyl Methacrylate (MMA) Polymerization for Bone Cement Production

AbstractBone cements based on poly(methyl methacrylate) (PMMA) have been widely used in orthopedic surgeries for fixation of prostheses and filling of bone defects. Bone cements are produced through in situ and in vivo free radical bulk polymerizations, which are highly exothermic and are subject to strong gel and glass effects. As a consequence, high temperatures may be reached during application. Furthermore, residual monomer usually remains unreacted inside the body and may cause aseptic loosening and tissue damages.1 In a companion work in this volume, it was shown that usual free‐radical polymerization models might effectively describe the bone cement preparation2 and therefore be used for quantitative analysis of the bone cement synthesis. In this work, a theoretical investigation based on a multicell reactor model is performed to study the bone cement production and allow for future optimization of the preparation procedure. It is shown that the degree of solubility of the pre‐polymer powder in the liquid monomer is the most important variable during the bone cement preparation and that this variable should be manipulated for design and control of the operation in real applications.

Optical Absorption Coefficient, Time of Thermal Relaxation, Time of Surface Threshold, and Time of Heat Incubation for PMMA Samples at the CO2Laser-Beam Wavelength of 10.6 µm

This paper discusses in detail the mathematical identification of the optical absorption alpha (cm(1)) of Beer's law, a crucial parameter to study the development of laser beam craters into dry poly(methyl methacrylate) (PMMA) samples exposed to steady CO(2) laser beams emitting radiation at lambda = 10.6 microm in continuous- wave (CW) mode. Three additional time-dependent coefficients have been determined as well. In clinical applications, these results are important in order to precisely quantify and forecast the ablation capabilities of the CO(2) laser beam, to optimize its usage in the operating room, and to address the safety issues related to surgical interventions on human tissue. Currently, the data available in the literature do not allow the identification of the numerical value of alpha (cm(1)) for PMMA at lambda = 10.6 microm with enough, and therefore satisfactory, accuracy. Additionally, the correct identification of the optical absorption of PMMA would allow the isolation, with better accuracy, of other key time-dependent coefficients, such as relaxation time, surface threshold time, and heat incubation time, which are all described in the literature in a qualitative rather than quantitative fashion. Correct bone cement preparation depends on the value of alpha (cm(1)) of the PMMA in order to avoid unwanted complications in patients during cement removal via laser techniques. The laser in use was configured in different combinations with the following parameters: transverse electromagnetic modes (TEMnm), output power (I0), exposure times (te), and focal lengths (fk). Several PMMA blocks (1 cm x 4 cm x 4 cm) were exposed to CW radiation of three commercially available CO(2) medical laser devices showing a TEM11 mode. Each block was exposed to the beam on a horizontal and well-polished surface of each sample. Four focal lengths (2.5", 5", 7.5", and 15.75" [400 mm]) were used to focus the beam on the well-polished and dry surface of the PMMA samples. The resulting dimensions of the craters were measured after each exposure, which has been kept at a 10-Watt CW beam. Exposure time ranged from 0.5 to 2 sec. The value of alpha = 502 (cm(1)) for PMMAat 10.6 microm was identified, matching other results reported in the literature for similar compact media in the absence of water content, such as PMMA. The time of thermal relaxation was 9.358 x 10(4) sec, the time of surface threshold was 9.365 x 10(4) sec, and the time of heat incubation was 3.6 x 10(7) sec (all three for PMMAat 10.6 microm for any exposure). Using the calculated value of alpha, one of the practical clinical recommendations would be, for instance, to reduce or to abolish the utilization of colorant dopants in the preparation of the bone cement mixture and therefore reduce the danger of bone damage possible during the removal of bone cement via laser techniques. Other examples refer to other clinical bone and dental treatments.

The preparation of bone cement.

The hip joint is subjected to large, repetitive loads. It is therefore clear that the bone cement, which allows the transfer of load across the new joint, must be able to withstand the everyday loads that it will be subjected to. Improving the mechanical properties of the cement to withstand high stresses, fatigue and creep loading will reduce the chances of failure, ultimately increasing the longevity of the joint replacement. To date, work in this area has concentrated on improving the mechanical properties of bone cement through improved bone cement mixing techniques. In the next issue we will be covering the effect that the design of the mixer and vacuum mixing has on improving the mechanical properties, such as the strength, fatigue and creep resistance, of the bone cement.

The formation of propylene fumarate oligomers for use in bioerodible bone cement composites

AbstractPoly(propylene fumarate) (PPF) oligomers were synthesized by step polymerization using bis(2‐hydroxypropyl fumarate) or propylene bis(hydrogen maleate) as starting materials. Oligomers possessing identical degrees of polymerization (DP), but varying in their end group character (either hydroxyl or carboxyl) were first prepared and characterized, then used as part of a bone cement preparation consisting of oligomer, tricalcium phosphate, calcium carbonate, and methyl methacrylate. Compressive strength of the resulting composite appeared to be dependent on both the degree of polymerization of the PPF, and the nature of the oligomers' end groups.