Volume Of Polymethylmethacrylate Research Articles

Decreasing polymethyl methacrylate bone cement concentration extends working and setting times in vitro.

To determine setting and temperature properties of diluted polymethyl methacrylate (PMMA) bone cement in vitro to assess utility for vocal fold augmentation in horses. 4 dilutions of PMMA equivalent to volumes of 15 mL, 20 mL, 25 mL, and 30 mL PMMA powder (PMMAp) in 10 mL solvent. For each volume PMMAp, setting times (tset), peak temperatures (Tmax), and times to peak temperature (tmax) were determined using a temperature data logger in a 4-mL volume of PMMA. Injectability was assessed in vitro by documenting the force required to inject 0.2 mL PMMA through an 18-gauge 3.5-inch spinal needle attached to a 6-mL syringe at 1-minute intervals. Working time (twork) was calculated from a linear regression of injectability. Peak temperatures increased with increasing volume of PMMAp: 56 °C, 86 °C, 99 °C, and 101 °C. Times for tset, twork, and tmax were inversely proportional to PMMA concentrations, resulting in tset of 23, 21, 17, and 14 minutes; twork of 22.75, 12.25, 7, and 4 minutes; and tmax of 28, 24, 19, and 16 minutes, respectively, for 15, 20, 25, and 30 mL PMMAp. Pairwise comparisons for all analyses were significant apart from Tmax for 25 and 30 mL PMMAp (P = .96) and twork for 20 and 25 mL PMMAp (P = .06). Decreasing the concentration of PMMA bone cement resulted in longer working times and setting times; however, peak temperatures did not differ between the 2 strongest concentrations. Further research is warranted to quantify diluted PMMA properties for in vivo use for vocal fold augmentation in horses.

Polymethyl Methacrylate in Patient-Specific Implants: Description of a New Three-Dimension Technique.

Polymethyl methacrylate (PMMA), an easily moldable and economical synthetic resin, has been used since the 1940s. In addition, PMMA has good mechanical properties and is one of the most biocompatible alloplastic materials currently available. The PMMA can serve as a spacer and as a delivery vehicle for antibiotics. Prior studies have indicated that no significant differences in infection rates exist between autologous and acrylic cranioplasty. Although inexpensive, the free-hand cranioplasty technique often yields unsatisfactory cosmetic results. In the present study, the application of a recently developed, economic modality for the perioperative application, and molding of PMMA to ensure a precise fit in 16 patients using computer-aided design, computer-aided manufacturing, and rapid prototyping was described.The mean defect size was 102.0 ± 26.4 cm. The mean volume of PMMA required to perform the cranioplasty procedure was 51 mL. The cost of PMMA was approximately 6 Euro (&OV0556;) per mL. The costs of fabricating the implants varied from 119.8 &OV0556; to 1632.0 &OV0556; with a mean of 326.4 &OV0556; ± 371.6. None of the implants required removal during the follow-up period.

Biomechanical effects of osteoplasty with or without Kirschner wire augmentation on long bone diaphyses undergoing bending stress: implications for percutaneous imaging-guided consolidation in cancer patients

BackgroundOsteoplasty has been discouraged in long bones. However, despite a substantial lack of pre-clinical biomechanical tests, multiple clinical studies have implemented a wide range of techniques to optimise long bone osteoplasty. The aim of the present study is to evaluate the biomechanical properties of osteoplasty alone and in combination with Kirschner wires (K-wires) in a cadaveric human diaphyseal model undergoing 3-point bending stress.MethodsThirty unpaired human cadaveric hemi-tibia specimens were randomly assigned to receive no consolidation (group 1, n = 10), osteoplasty alone (group 2, n = 10), or K-wires augmented osteoplasty (group 3, n = 10). Specimens were tested on a dedicated servo-hydraulic machine using a 3-point bending test. Fracture load was calculated for each specimen; two-sample Wilcoxon rank-sum tests were used to assess differences between groups.ResultsMedian volume of polymethyl methacrylate injected was 18 mL for group 2 (25th–50th percentile 15–21 mL) and 19 mL for group 3 (25th–50th percentile 17–21). There were no significant differences in fracture load between groups 1 and 2 (z = − 0.793; p = 0.430), between groups 1 and 3 (z = − 0.944; p = 0.347), and between groups 2 and 3 (z = − 0.454; p = 0.650). Fractures through the cement occurred in 4 of 30 cases (13.3%); there were no K-wires fractures.ConclusionsOsteoplasty with or without K-wires augmentation does not improve the resistance of diaphyseal bone to bending stresses.

Biomechanical study of injectable hollow pedicle screws for PMMA augmentation in severely osteoporotic lumbar vertebrae: effect of PMMA distribution and volume on screw stability.

OBJECTIVEThe purpose of this study was to compare stability of injectable hollow pedicle screws with different numbers of holes using different volumes of polymethylmethacrylate (PMMA) in severely osteoporotic lumbar vertebrae and analyze the relationship between screw stability and distribution and volume of PMMA.METHODSForty-eight severely osteoporotic cadaveric lumbar vertebrae were randomly divided into 3 groups-groups A, B, and C (16 vertebrae per group). The screws used in group A had 4 holes (2 pairs of holes, with the second hole of each pair placed 180° further along the thread than the first). The screws used in group B had 6 holes (3 pairs of holes, placed with the same 180° difference in position). Unmodified conventional screws were used in group C. Each group was randomly divided into subgroups 0, 1, 2, and 3, with different volumes of PMMA used in each subgroup. Type A and B pedicle screws were directly inserted into the vertebrae in groups A and B, respectively, and then different volumes of PMMA were injected through the screws into the vertebrae in subgroups 0, 1, 2, and 3. The pilot hole was filled with different volumes of PMMA followed by insertion of screws in groups C0, C1, C2, and C3. Distributions of PMMA were evaluated radiographically, and axial pull-out tests were performed to measure the maximum axial pullout strength (Fmax).RESULTSRadiographic examination revealed that PMMA surrounded the anterior third of the screws in the vertebral bodies (VBs) in groups A1, A2, and A3; the middle third of screws in the junction area of the vertebral body (VB) and pedicle in groups B1, B2, and B3; and the full length of screws evenly in both VB and pedicle in groups C1, C2, and C3. In addition, in groups A3 and B3, PMMA from each of the screws (left and right) was in contact with PMMA from the other screw and the PMMA was closer to the posterior wall and pedicle than in groups A1, A2, B1, and B2. One instance of PMMA leakage was found (in group B3). Two-way analysis of variance revealed that 2 factors-distribution and volume of PMMA-significantly influenced Fmax (p < 0.05) but that they were not significantly correlated (p = 0.078). The Fmax values in groups in which screws were augmented with PMMA were significantly better than those in groups in which no PMMA was used (p < 0.05).CONCLUSIONSPMMA can significantly improve stability of different injectable pedicle screws in severely osteoporotic lumbar vertebrae, and screw stability is significantly correlated with distribution and volume of PMMA. The closer the PMMA is to the pedicle and the greater the quantity of injected PMMA used, the greater the pedicle screw stability is. Injection of 3.0 mL PMMA through screws with 4 holes (2 pair of holes, with the screws in each pair placed on opposite sides of the screw) produces optimal stability in severely osteoporotic lumbar vertebrae.

PRELIMINARY MECHANICAL TEST OF PROXIMAL FEMUR REINFORCEMENT WITH CEMENTED X-SHAPED PMMA.

ABSTRACTObjective:To evaluate the mechanical behavior of the proximal end of the femur submitted to the X-shaped polymethylmethacrylate (PMMA) reinforcement technique.Methods:Fifteen synthetic femurs, with a Nacional® density of 10 PCF, were divided into two groups: the DX group, with 5 units that were submitted to PMMA reinforcement, and the DP group, with 10 units, which were evaluated intact. The volume of PMMA required, the maximum load, and the absorbed energy to fracture were analyzed by means of a static mechanical bending test simulating a fall on the greater trochanter.Results:A mean of 6 ml of PMMA was used to model the X-reinforcement; it was observed that the DX group presented significantly higher maximum load (median = 1553 N, p = 0.005) and absorbed energy to fracture (median = 9.7 J; p = 0.050) than the DP group (median = 905 N and 6.6 J).Conclusion:X-reinforcement of the proximal end of synthetic femurs showed a statistically significant increase in the maximum load and absorbed energy to fracture in the mechanical assay when compared to the control group. Level of Evidence III, Experimental study.

Fabrication of injectable and expandable PMMA/PAASf bone cements

The volume of polymethyl methacrylate (PMMA) bone cement shrank by 3.82%–7.08% during solidification. Such volume shrinkage generated a residual stress that induces minor cracking in bone–cement interface and affected the long-term stability and mechanical property of vertebral body. In this study, injectable and expandable PMMA/sodium polyacrylate short fiber (PAASf) composite bone cements were fabricated, and water absorption and swelling properties of PAASf were taken into account. Effects of PAASf volume fraction in PMMA/PAASf bone cements on absorption ratios of simulated body fluid (SBF) and volume expansion ratios were investigated. When the volume fraction of PAASf was lower than 30%, PMMA/PAASf bone cements were stable and did not fall apart after expansion in SBF, and the maximum volume expansion ratio was 33.4%. When PAASf content increased from 10 vol% to 30 vol%, solidification time of PMMA/PAASf bone cements increased and their injection and mechanical properties decreased, although the PMMA/PAASf bone cements (9:1) still satisfy the requirements for clinical application. The absorption expansion mechanism of PMMA/PAASf bone cements in SBF in the first stage of expansion (global expansion before solidification) and in the second stage of expansion (local surface expansion after solidification) was analyzed through micro-computed tomography and SEM. Cytotoxicity of PMMA bone cement and PMMA/PAASf bone cements were compared, and results suggested that their cytotoxicity did not significantly vary. These findings indicated that injectable and expandable PMMA/PAASf bone cements can be used in clinical treatments.

Injectable and biodegradable composite bone filler composed of poly(propylene fumarate) and calcium phosphate ceramic for vertebral augmentation procedure: An in vivo porcine study.

Despite its common usage in vertebral augmentation procedures (VAPs), shortcomings of commercial polymethylmethacrylate (PMMA) still remain. Accordingly, injectable and biodegradable composite cements, which are composed of poly(propylene fumarate)/α-tricalcium/hydroxyapatite (PPF/α-TCP/HAP) and PPF/tetracalcium phosphate/dicalcium phosphate (PPF/TtCP/DCP), were developed. A porcine model was used and cylindrical holes in critical size were created at the center of the lateral cortex of vertebral bodies of the lumbar spine. A fixed volume of testing materials and PMMA were randomly injected into the defects. Results showed that both composite groups had a comparable radiolucency as PMMA but a significantly lower setting temperature. Histological inspections revealed new bone formation and remodeling along the border of the two composite cements. New bone substitution and irregular sclerotic bone mantles were found along the composite cements but not in the PMMA group. Radiological and histological changes were observed in the two composite groups and these modifications were diminished along the block boundaries. These findings imply gradual substitution of decomposed composite by new bone formation, which could not be found around the PMMA block. Comparing PPF/α-TCP/HAP with the PPF/TtCP/DCP cement block, smaller particles that were spreading out were observed in the TtCP/DCP group, which represents rapid degradability. In conclusion, the composite cements have advantages such as a low setting temperature, radio-opacity, biodegradability, and osteoconductivity. The injectable PPF/calcium phosphate ceramic composite has the potential to be used in VAPs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2232-2243, 2017.

An index for staging facial lipoatrophy and evaluation of the efficacy of the treatment with polymethylmethacrylate in HIV/AIDS patients: a pilot study

Treatment of facial lipoatrophy of HIV/AIDS patients is mandatory by law in Brazil due to its negative impact on their quality of life. The index for facial lipoatrophy (ILA) is used as one of the inclusion criteria for patient treatment. To define a correct diagnosis and staging of facial lipoatrophy, by employing the ILA. This is an observational study of a series of case reports from patients submitted to facial lipoatrophy evaluation through ILA and treated with polymethylmethacrylate (PMMA) fillers. Facial lipoatrophy was classified in grades from I to IV, corresponding to mild, moderate, severe and very severe stage, according to ILA. Response to the treatment was defined as excellent (≥ 91%), good (71-90%), moderate (51-70%) and insufficient (≤ 50%). A total of 20 patients were included in this study: 18 men and two women. Median age was 49 years (35-61) and average ILA was 9.9 (7.2-16.8). Ten patients presented facial lipoatrophy grade II (moderate), 5 grade III (severe) and 5 grade IV (very severe). The average volume of PMMA used was 13 mL (5.5-22 mL). All patients showed good or excellent response, with a median of 86% (74-100%). The most typical adverse effect was local oedema but there were no late adverse effects. The ILA is an excellent method for evaluation of facial lipoatrophy and also for the assessment of the response to therapy. Facial filling with PMMA showed efficacy and safety in the treatment of facial lipoatrophy in HIV/AIDS patients.

The Analysis of Patterns and Risk Factors of Newly Developed Vertebral Compression Fractures after Percutaneous Vertebroplasty

ObjectiveThe purpose of this study was to investigate the patterns and the risk factors of newly developed vertebral compression fractures (VCFs) after percutaneous vertebroplasty (PVP).MethodsWe performed a retrospective review of the 244 patients treated with PVP from September 2006 to February 2011. Among these patients, we selected 49 patients with newly developed VCFs following PVP as the new VCFs group, and the remaining 195 patients as the no VCFs group. The new VCFs group was further divided into 2 groups : an adjacent fractures group and a nonadjacent fractures group. The following data were collected from the groups : age, gender, body weight/height, body mass index (BMI), bone mineral density (BMD) score of the spine and femur, level of initial fracture, restoration rate of anterior/middle vertebral height, and intradiscal cement leakage, volume of polymethylmethacrylate (PMMA).ResultsAge, gender, mean body height/weight, mean BMI and volume of PMMA of each of the group are not statistically significantly associated with fractures. In comparison between the new VCFs group and the no VCFs group, lower BMD, intradiscal cement leakage and anterior vertebral height restoration were the significant predictive factors of the fracture. In addition, new VCFs occurrence at the adjacent spines was statistically significant, when the initial fracture levels were confined to the thoracolumbar junction, among the subgroups of new VCFs.ConclusionLower spinal BMD, the greater anterior vertebral height restoration rate and intradiscal cement leakage were confirmed as risk factors for newly formed VCFs after PVP.

Value of intraosseous venography in percutaneous vertebroplasty for treatment of symptomatic vertebral hemangiomas

To evaluate the clinical efficacy of percutaneous vertebroplasty (PVP) in patients with symptomatic vertebral hemangiomas and determine whether prior intraosseous venography decreases extravertebral leakage of PMMA and improves clinical outcomes in these procedures. Retrospective review was conducted on 45 consecutive patients with 53 symptomatic vertebral hemangiomas associated with chronic pain (all cases) or paralysis caused by spinal cord compression (1 case) or vertebral compression fractures (3 cases) treated with PVP at our institution to define two populations. Group A consisted of 27 vertebral hemangiomas in 23 patients who underwent intraosseous venography before injection polymethylmethacrylate (PMMA). Group B consisted of 26 vertebrae in 22 patients who underwent injection PMMA without prior venography. CT was done 1 to 3 days after PVP to observe PMMA distribution in vertebrae and whether leakage. Clinical outcomes, included pain relief, leakage of PMMA, volume of PMMA injected, expense and X-ray exposure times in each vertebral body, were compared in the two groups by using χ(2) or t test. No significant difference was seen between the groups with respect to age, sex, the number of treated vertebrae, or preprocedural degrees of pain. The successful rate of technique of PVP was 100%. The mean volume of PMMA injected in each vertebra was 3.96 ml. CR, PR and NR was obtained respectively 84.5%, 13.3% and 2.2% during 6 months to 5 years of follow-up expect one case had unrelieved pain in group A. At 6 months after PVP, 22 cases (95.7%) in group A and 22 cases (100%) in group B achieved adequate pain relief (P = 0.323). 6 vertebrae (6/27) in group A and 2 vertebrae (2/26) in group B with asymptomatic leakage of PMMA were demonstrated by CT (P = 0.140). The mean volume of PMMA injected in each vertebra was 3.70 ml in group A and 4.23 ml in group B (P = 0.157). The mean expense of each vertebra was ¥7.24 × 10(3) in group A and ¥5.84 × 10(3) in group B (P = 0.000), the mean decreases were ¥1.4 × 10(3) in group B than group A. The mean X-ray exposure times on each vertebral body was 13.28 minutes in group A and 8.78 minutes in group B (P = 0.000), the mean decreases were 4.5 minutes in group B than group A. PVP is an effective and safe procedure for treating symptomatic vertebral hemangiomas. Prior intraosseous venography does not significantly improve the effectiveness or safety of PVP for vertebral hemangiomas performed by qualified, experienced operators, on the other hand, it increases the expense and X-ray exposure times of PVP.

Treatment of Extraspinal Painful Bone Metastases with Percutaneous Cementoplasty: A Prospective Study of 50 Patients

The aim of this study was to assess the efficacy of percutaneous cementoplasty (PC) with polymethylmethacrylate (PMMA) in painful extravertebral lytic bone metastases not responding to conventional therapy. Fifty patients (25 females), mean age 64.7 +/- 11.2 years, underwent PC after giving informed consent. Procedures were performed under fluoroscopy (1/50) or combined fluoroscopy-CT (49/50) guidance in local anesthesia or under deep sedation in 7 patients with large metastases who underwent radiofrequency thermoablation (RFA) in the same session. Seventy lesions were treated (1-6 per patient; average, 1.4 +/- 0.9), arranging in size from 1 to 10 cm (average, 3.6 +/- 2.1 cm). Mean volume of PMMA per lesion was 5.9 +/- 3.2 ml (range, 1.5-15.0 ml). Pain was prospectively evaluated on an 11-point visual analog scale (VAS) before and after the procedure (follow-up, 15 to 36 months). Mean VAS score dropped from 9.1 +/- 1.2 (range: 6-10) to 2.1 +/- 2.5 (range: 0-9). Mean VAS difference was 7.0 +/- 2.3 (range, 1-10; p \ 0.0001, Wilcoxon signed rank test). Forty-seven of the 50 patients (94%) suspended narcotic drugs, in 22 (44%) pain was controlled with a nonsteroidal anti-inflammatory drug, in 25 (50%) analgesic therapy was suspended, and 13 of 50 (26%) had complete pain regression. In 3 of the 50 patients (6%) pain was not improved. No statistical difference between osteoplasty and osteoplasty plus RFA was found (p = 0.8338, Mann-Whitney test). No complications arose during the procedure. Two patients with metastases in the femoral diaphysis reported a fracture 1 month after treatment. PC is effective to obtain pain regression in painful bone metastases not responding to conventional analgesic therapy; bone consolidation cannot be obtained in the diaphysis of long weight-bearing bones.

Percutaneous vertebroplasty in patients with osteoportic vertebral body fractures

Percutaneous vertebroplasty in patients with osteoportic vertebral body fractures

Pain Relief by Percutaneous Vertebroplasty for Osteoporotic Compression Fractures: An Evaluation of Polymethylmethacrylate Injection Volume

Percutaneous vertebroplasty may provide pain relief in the treatment of patients with severe osteoporotic compression fracture. A retrospective study was done to determine the relationship between injection volume and therapeutic benefits. Methods and Results: Polymethylmethacrylate (PMMA) was injected into 79 compression fractures in a total of 70 patients. The amounts of PMMA injected ranged from 2 to 9 milliliters. We divided our patients into two groups according to the volume of PMMA injected. Group A had the volume injected ranging from 2 to 5 milliliters whereas Group B, 6 to 9mL. The injection of bone cement was stopped immediately whenever a backflow opacification was observed in the posterior third of the vertebral body in order to prevent iatrogenic spinal cord compression. In Group A patients, the mean postoperative pain score was decreased to 1.28. The mean decreased pain score was 3.28. In Group B patients, the mean postoperative pain score decreased to 1.09. The mean decreased pain score was 3.39. There was no significant difference between these two groups in the decreased pain score (P=0.52) and postoperative pain status (P=0.14). Conclusions: The author found no correlation between the injection volume and its therapeutic benefit. Greater amount of PMMA injected will not give a better clinical outcome to patients with osteoporotic compression fracture. The injection of PMMA should be stopped immediately whenever a backflow opacification is observed in the posterior third of the vertebral body in order to prevent epidural leakage. The presence of PMMA epidural leakage may decrease the pain relief benefit after percutaneous vertebroplasty.

Posterolateral Approach of Percutaneous Vertebroplasty in Thoracolumbar Fractures

Objective: Transpedicular percutaneous vertebroplasty has been widely used for the treatment of osteoporotic vertebral compression fractures. The authors introduce a novel method of approach by the posterolateral route for percutaneous vertebroplasty. Materials and Methods: A retrospective review was conducted on 30 consecutive patients with 42 vertebrae of acute osteoporotic thoracolumbar compression fractures treated from Mar. 2002 to May 2003 with percutaneous vertebroplasty using this approach. Pain response, volume of polymethylmethacrylate (PMMA), epidural leakage of PMMA, distribution of PMMA in vertebral body and complications were investigated. Results: Among 30 patients, 27 had marked to complete pain relief, 2 moderate pain relief and 1 no significant change during follow up period. A mean volume of PMMA injected by this unilateral approach was 5.8cc. Epidural leakage of PMMA was noted on 28 vertebrae(66.7%) on postoperative CT scan. All vertebrae except one injected by this method showed bilateral distribution of PMMA on postoperative CT scan. Minor complication (transient radicular pain) occured in 2(6.7%) patients. Conclusion: Unilateral posterolateral approach of percutaneous vertebroplasty was a safe and effective method for the treatment of acute osteoporotic thoracolumbar compression fractures.

Dose-dependent epidural leakage of polymethylmethacrylate after percutaneous vertebroplasty in patients with osteoporotic vertebral compression fractures.

The use of polymethylmethacrylate (PMMA) cement by percutaneous injection in cases requiring vertebroplasty provides pain relief in the treatment of osteoporotic vertebral compression fractures. A retrospective study was performed to assess what caused PMMA cement to leak into the epidural space and to determine if this leakage caused any changes in its therapeutic benefits. Polymethylmethacrylate was injected into 347 vertebral compression fractures in 159 patients. The cement leaked into the epidural space in 92 (26.5%) of 347 treated vertebrae in 64 (40.3%) of the 159 patients, as demonstrated on postoperative computerized tomography scanning. Epidural leakage of PMMA cement occurred more often when injected above the level of T-7 (p = 0.001) than below. The larger the volume of PMMA injected the higher the incidence of epidural leakage (p = 0.03). Using an injector also increased epidural leakage (p = 0.045). The position of the needle tip within the vertebral body and the pattern of venous drainage did not affect epidural leakage of the cement. Leakage of PMMA into the epidural space reduced the pain relief expected after vertebroplasty. The immediate postoperative visual analog scale scores were higher (and therefore reflective of less pain relief) in patients in whom epidural PMMA leakage occurred (p = 0.009). Three months postoperatively, the authors found the highest number of patients presenting with pain relief, including those in the group with epidural leakage, and at this follow-up stage there were no significant differences between the two groups. The authors found that epidural leakage of PMMA after percutaneous vertebroplasty was dose dependent. The larger amount of injected PMMA, the higher the incidence of leakage. Injecting vertebral levels above T-7 also increased the incidence of epidural leakage. Epidural leakage of PMMA may attenuate only the immediate therapeutic effects of vertebroplasty.

Dielectric-relaxation studies in polymethyl methacrylate-mica composites

Dielectric properties have been studied in polymethyl methacrylate (PMMA) and composites of PMMA containing different weight ratios of mica at different temperatures and different frequencies. It has been observed that the dielectric constant (ɛ′) and dielectric loss (ɛ″) increase with the increasing amount of mica in the composites up to a certain percentage of mica. The activation energy values have been calculated. The results have been explained on the basis of the space charge effect, dipolar orientation and increase in the free volume of PMMA with the addition of mica in it.