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Results for “Polymethyl Methacrylate”

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At least 271 records · Page 15Linked to original sources

PubMed1999

Efficacy of irrigation for removal of particulate debris after cemented total knee arthroplasty.

We studied the amount of particulate debris removed with pulsatile lavage irrigation before and after component implantation in 13 consecutive patients undergoing primary cemented total knee arthroplasty (TKA) done by a single surgeon. Before component implantation, the knees were copiously lavaged with 3 L of pressurized irrigant; all fluid was collected in 1 aliquot using standard wall suction canisters. After cementing the components in place, another 3 L of pressurized irrigant was used; this fluid was collected in 3 sequentially labeled 1-L aliquots. Collected fluids were centrifuged, and the residue was washed, recentrifuged, and dried. Residual particulate debris was quantitated by weight. An average of 537 mg/L (range, 16-1,406 mg/L) of debris were removed before implantation with 3 L of irrigation. An average of 217 mg/L (range, 31-999 mg/L), 52 mg/L (range, 0-189 mg/L), and 49 mg/L (range, 1-185 mg/L) of debris was removed after implantation with each of the additional liters. Using analysis of variance testing, there was a statistically significant difference between the amount of debris removed with 3 L and after 4 L (P = .02) and 5 L (P = .03) of irrigant. There was no statistical difference between irrigation with 5 L and 6 L of irrigation (P = .92). The residua particulate debris was also analyzed to determine the relative amounts of bone-soluable organics and polymethyl methacrylate (PMMA). Before implantation, the residual debris, by weight, consisted of 79% bone and 21% soluable organics. We found on average that after implantation of components the specimens contained 53% bone and 47% PMMA and soluable organics by weight. We believe that despite careful implantation and meticulous cement technique, large amounts of debris, including bone and PMMA, remain after TKA, which require at least several liters of pulsatile lavage to remove. Removal of this particulate debris may decrease third-body polyethylene wear.

Aged↗

PubMedDate not supplied

Spontaneous fracture of an implanted posterior chamber intraocular lens.

PURPOSE: Spontaneous fracture of an intraocular lens (IOL) haptic is a rare complication of cataract surgery. The authors report a case of spontaneous fracture of an implanted posterior chamber IOL. CASE: Five years ago, a 12-year-old patient underwent linear lens extraction, posterior capsulotomy, and anterior vitrectomy due to traumatic cataract and received a polymethyl methacrylate (PMMA) biconvex posterior chamber IOL implanted in ciliary sulcus. Five years later, IOL optic was found in anterior chamber with its haptics broken from the optic-haptic junction. DISCUSSION: The broken haptic was examined with scanning electron microscopy. The fracture site of the haptic was on the optic-haptic junction. The fractured surface had a regular appearance. CONCLUSIONS: To our knowledge, this is the fourth report of spontaneous fracture of an implanted posterior chamber IOL.

Anterior Chamber↗

PubMedDate not supplied

Design and fabrication technique for metal palates in maxillary complete dentures.

Polymethyl methacrylate exhibits excellent physical properties. Unfortunately, complete dentures fabricated from this material may still fracture. Maxillary complete dentures opposing natural dentition may have a tendency to develop recurrent midline fractures due to multiple reasons. A potential method of preventing this fracture is metal reinforcement of the palatal portion of the prosthesis. A technique will be presented describing a sequence that incorporates predictable design, fabrication and finishing of a metal palate for a maxillary complete denture.

Acrylic Resins↗

PubMed1998

Skin ulceration from tibial cement extrusion: case report and literature review.

Polymethyl methacrylate extrusion through a small tibial defect occurred during revision of a long-stemmed total knee arthroplasty. It caused necrosis and ulceration of the overlying skin. Resection of the protruding cement, debridement of the ulcer, and primary closure effected a cure. This is the first report of cement-induced skin necrosis and first report of tibial cement extrusion during revision of a total knee arthroplasty. Subcutaneous cement extrusion should be considered in the differential diagnosis of pretibial ulcers following total knee arthroplasty with cemented stems.

Aged↗

PubMed2005

Kyphoplasty-augmented short-segment pedicle screw fixation of traumatic lumbar burst fractures: initial clinical experience and literature review.

OBJECT: Surgical intervention for thoracolumbar burst fractures is indicated for patients with neurological deficits and/or evidence of severe spinal instability. The goals of surgery are decompression, deformity correction, and stabilization. Nevertheless, the optimal surgical strategy to achieve these goals remains a subject of debate. Short-segment pedicle screw fixation is associated with a 20 to 50% incidence of pedicle screw failure and progressive spinal deformity. Initial biomechanical and clinical studies have shown that reinforcement of short-segment pedicle screw fixation with vertebroplasty improves spinal stability and decreases instrument failure rates. In this study, the authors describe their initial clinical experience with kyphoplasty used to augment short-segment pedicle screw fixation of traumatic lumbar burst fractures. METHODS: Five patients with traumatic burst fractures of the lumbar spine were included in this retrospective review of patients treated for this disorder at the University of California, San Diego and the University of California, San Francisco between 2002 and 2004. All patients underwent transpedicular kyphoplasty and short-segment pedicle screw fixation. The mean follow-up period was 10.6 months (range 6-18 months). All patients underwent short-segment pedicle screw fixation reinforced with polymethyl methacrylate kyphoplasty. The preoperative, postoperative, and follow-up plain x-ray films were evaluated. Radiographic analysis included measurements of kyphotic angulation, anterior vertebral body height, and evidence of bone fusion. Clinical evaluation was performed postoperatively and at follow-up review. CONCLUSIONS: Based on the authors' initial experience, kyphoplasty supplementation may improve the long-term integrity of short-segment pedicle screw constructs and allow for improved rates of fusion and better clinical outcomes in patients with traumatic lumbar burst fractures.

Adult↗

PubMed2006

Kinetics of in vitro lysozyme deposition on silicone hydrogel, PMMA, and FDA groups I, II, and IV contact lens materials.

We sought to compare the kinetics of in vitro lysozyme deposition on silicone hydrogel (SH), polymethyl methacrylate (PMMA), and FDA groups I, II, and IV contact lenses. Lenses were incubated in 125I-labeled lysozyme for time periods ranging from 1 hr to 28 days, and radioactive counts were determined. SH lenses and PMMA deposited less lysozyme than conventional hydrogel lenses (p < 0.05). Lysozyme accumulation on group IV lenses reached a maximum on the seventh day and then plateaued, whereas on groups I, II, and SH lenses, deposition continued to increase across all time periods, reiterating that kinetics of lysozyme deposition is highly material dependent.

Biocompatible Materials↗

PubMed2004

Wide-angle viewing lens for vitrectomy.

PURPOSE: To report a new wide-angle viewing contact lens for vitrectomy. DESIGN: New surgical instrument. METHODS: The new wide-angle viewing lens is made of glass and polymethyl methacrylate without a plastic rim. The diameter is reduced to 16.2 mm. In addition to a smaller diameter than the currently available lens, the new lens is partially cut to reduce the lens diameter. RESULTS: A smaller diameter makes it possible to eliminate contact between surgical instruments and the wide-angle lens. Instruments can be inserted through sclerotomies without removing the wide-angle lens. The optical properties are otherwise identical to the standard wide-angle lens. CONCLUSION: The new wide-angle viewing lens may be easier to use in vitreous surgery.

Contact Lenses↗

PubMed1997

Designing manufacturing and the clinic application of the prosthesis for the patients with large ocular defects.

PURPOSE: To design and manufacture the prosthesis of external type for patients with ocular large defects. METHODS: Silicon and polymethyl methacrylate (PMMA) were chosen the chief materials: The main procedures are: taking the impression, color mixture, making primitive form of the prosthesis, modification and fixation. RESULTS: Fifty patients with large ocular defects took the prosthesis, the cosmetic results are satisfactory. All the patients give satisfactory comments on the 5 main indexes: color 90%, stereo-feeling 100%, peripheral difference 86%, fidelity 98% and fixation 86%. CONCLUSIONS: To make ocular prosthesis, materials with good quality and complicated technology are needed. The prosthesis made by silicon combined with PMMA show good results. Among the procedures of making prosthesis, color mixture and fixation are the most important.

Eye Neoplasms↗

PubMed2004

[Indications for and clinical efficacy of continuous hemodiafiltration (CHDF) for severe acute pancreatitis].

It has been claimed humoral mediator network including pro-inflammatory cytokines plays a pivotal role in the pathophysiology of SAP. On the other hands, we have reported CHDF using polymethyl methacrylate (PMMA) membrane hemofilter could remove cytokines in blood of a patient continuously and effectively. Therefore, we applied CHDF to patients with SAP. CHDF was performed using a PMMA-hemofilter for removal of causative cytokines regardless of renal function 24 hours a day without interruption until IL-6 blood level became below 400 pg/ml. Selective digestive decontamination (SDD) was also given for prevention of bacterial translocation. Forty-two out of 45 patients (93%) receiving both CHDF and SDD survived. We conclude critical care with PMMA-CHDF and SDD is an effective treatment for SAP.

Acute Disease↗

PubMed2001

Dosimetric characteristics of 192Ir sources used in interstitial brachytherapy.

Dosimetric quantities of 192Ir seed (5 mm length) and wire (10 mm length) brachytherapy sources have been determined. The quantities were measured based on the protocol introduced by the Radiation Therapy Committee of the American Association of Physicists in Medicine (AAPM) Task Group 43. Quantities such as dose rate constant, (lambda), radial dose function, g(r), and anisotropy function, F(r, theta) were experimentally determined and the geometry function, G(r, theta), was calculated. TLD measurements were made in a polymethyl methacrylate (PMMA) phantom of dimensions 25 cm x 20 cm x 5 cm by means of LiF:Mg,Ti (TLD-100) dosimeters for distances of 1-10 cm for g(r), and the same distances at angles of 0-180 degrees for F(r, theta). Dose rate constant for 192Ir seed and wire were found to be 1.196+/-5 and 1.082+/-5% cGy h(-1) U(-1), respectively (1 U = unit of air Kerma strength = 1 microGy m2 h(-1) = 1 cGy cm2 h(-1)). The obtained results for g(r), G(r, theta) and F(r, theta) are also presented and discussed.

Algorithms↗

PubMed1998

Radio-opaque markers for stereotactic imaging of uveal melanoma.

In in vitro and in vivo studies, episclerally sutured radio-opaque markers were evaluated as localizers for better determination of the clinical tumour volume prior to stereotactic radio-therapy of uveal melanoma. Four different types of markers were studied in vitro: tantalum marker, 2.5 mm in diameter; ring-shaped markers custom-designed in polymethyl methacrylate (PMMA), 2.6 mm and 3.0 mm in diameter; and barium-impregnated silicone rubber spheres, 2 mm in diameter. In vivo PMMA markers 3.0 mm in diameter and barium-impregnated silicone rubber spheres 2 mm in diameter were used. The best results were obtained with the barium-impregnated silicone rubber spheres both in vitro and in vivo. For the CT-delineation of selected uveal melanomas with either a flat discoid shape or flat tumour extensions or when adjacent serous retinal detachment is present, small episclerally sutured barium-impregnated silicone rubber spheres are useful as localizers for determining the clinical tumour volume.

Humans↗

PubMedDate not supplied

[Bone marrow hematopoiesis in polymer composite implants in long-term bone marrow cultures].

The morphological composition of cells on implants made of different composition materials was studied on the model of long-term bone marrow cultures at cultivation for 28 days. Three samples of materials were investigated: polymethyl methacrylate (PMMC), PMMC with hydroxyapatite (HA) and PMMC with HA and subsequent processing with supercritical carbon dioxide. A gradual rise in total number of cells was observed on the implants for 4 weeks as well as increasing number of stromal and hemopoietic cells. With increasing time of cultivation the share of stromal cells was growing while the percent of hemopoietic cells fell. The greater number of hemopoietic cells was observed on the samples of the implants made from composites containing HA vs implants made from the initial PMMC.

Animals↗

PubMed2005

Anterior spinal column augmentation with injectable bone cements.

A vertebral fracture, whether originating from osteoporosis or trauma, can be the cause of pain, disability, deformation and neurological deficit. The treatment of vertebral compression fractures has, for many years until the advent of vertebroplasty, consisted of bedrest and analgesics. Vertebroplasty is a percutaneous technique during which bone cement is injected in a vertebral body to provide immediate pain relief by stabilization. Inflatable bone tamps can, prior to the injection of cement, be used to create a void in the vertebral body, in which case the technique is known as balloon vertebroplasty (or kyphoplasty). The chance of extracorporal cement leakage is smaller for balloon vertebroplasty than for vertebroplasty. Some authors also claim to have gained some correction in vertebral body height or angulation. Both interventions can be used for several indications, including osteoporotic compression fractures and osteolytic lesions of the vertebral body such as myeloma, hemangioma or metastasis, and also for traumatic burst fractures in combination with pedicle screw instrumentation. Polymethyl methacrylate cement is the bone void filler that is used most frequently, although the application of calcium phosphate cements has been studied widely in vitro, in vivo and also in small-scale clinical series. The clinical results of (balloon-) vertebroplasty are favorable with 85-95% of all patients experiencing immediate and long-lasting relief of pain. Serious complications are relatively rare but include neurological deficit and pulmonary embolism. In this paper, both vertebroplasty and balloon vertebroplasty and their respective indications, techniques and results are described in relation with the application and limitations of permanent and resorbable injectable bone cements.

Absorbable Implants↗

PubMed2005

High-speed separation of proteins by microchip electrophoresis using a polyethylene glycol-coated plastic chip with a sodium dodecyl sulfate-linear polyacrylamide solution.

In this paper, we describe a method for size-based electrophoretic separation of sodium dodecyl sulfate (SDS)-protein complexes on a polymethyl methacrylate (PMMA) microchip, using a separation buffer solution containing SDS and linear polyacrylamide as a sieving matrix. We developed optimum conditions under which protein separations can be performed, using polyethylene glycol (PEG)-coated polymer microchips and electrokinetic sample injection. We studied the performance of protein separations on the PEG-coated PMMA microchip. The electrophoretic separation of proteins (21.5-116.0 kDa) was completed with separation lengths of 3 mm, achieved within 8 s on the PEG-coated microchip. This high-speed method may be applied to protein separations over a large range of molecular weight, making the PEG-coated microchip approach applicable to high-speed proteome analysis systems.

Acrylic Resins↗

PubMed2002

Steady state and time-resolved spectroscopic studies of 7-hydroxyquinoline in various polymeric matrices.

The photophysical behavior of 7-hydroxyquinoline (7HQ) is studied in four polymer matrices, viz. polymethyl methacrylate (PMMA), cellulose acetate (CA), polyvinyl alcohol (PVA) and Nafion-117, at ambient temperature using both steady state and time-domain measurements. The study reveals both ground as well as excited state tautomerization in the case of PVA. In PMMA and CA, the intermolecular hydrogen bond to the host polymer results in proton transfer. Edge excitation red shift (EERS) and excitation and emission wavelength dependent decays are observed for normal emission in PMMA and CA matrices. These results are attributed to the trapping of a normal molecule in different geometries. In Nafion, the results show the presence of 7HQ cationic species trapped in the polymer.

Cellulose↗

PubMed2004

A procedure and criterion for bone cement fracture toughness tests.

Nowadays, two procedures, based on the recommendation of two American standards (ASTM E399 and ASTM D5045), are used to determine the fracture toughness, KIc, of bone cement. However, there is a lack of knowledge about the equivalence of the two testing methods applied to bone cement. Additionally, in spite of the recommendation of several authors to introduce a rejection criterion for specimens based on the size of defects found in the fracture surface, no data are available about the effect of porosity within the material on the KIc of bone cement. The aims of this study were to verify whether the KIc values calculated for bone cement using the two procedures are comparable and whether macroporosity within the tested samples affects the KIc value of bone cement, and, if so, to establish a rejection criterion for specimen selection. Samples of pure polymethyl methacrylate (PMMA) were tested by both procedures. Additionally, samples showing defects (macroporosity) of different sizes and located in different positions within the specimen were tested. The KIc value determined following the ASTM E399 procedure was 13 per cent lower than that calculated following the ASTM D5045 procedure. In the first series a lower data scatter was observed. Also, the presence of macroporosity on the fracture surface of the specimen affected the KIc value of bone cement. Therefore, the mechanical behaviour of samples was affected by defects within the material. Since it is possible to mould specimens without macroporosity, it seems recommendable to reject specimens with macroporosity on the fracture surface before calculating the KIc value of bone cement.

Bone Cements↗

PubMed2006

Closure of persistent cyclodialysis cleft using the haptics of the intraocular lens.

PURPOSE: To evaluate a technique for ab-interno repair of cyclodialysis cleft in conjunction with placement of an intraocular lens (IOL). DESIGN: Interventional case reports. METHODS: setting: Clinical practice. patients: Two eyes of two patients, one phakic and one aphakic, present with hypotony secondary to traumatic cyclodialysis cleft. intervention: A single piece all-polymethyl methacrylate intraocular lens (PMMA IOL) 13.5 mm in diameter was placed in the ciliary sulcus with the haptics placed in the area of cyclodialysis cleft during cataract surgery and secondary placement of IOL. main outcome measures: Intraocular pressure (IOP). RESULTS: Hypotony resolved in both patients on the first postoperative day and the IOP was maintained above 10 mm Hg for more then 36 months postoperatively. CONCLUSIONS: In the setting of hypotony from a traumatic cyclodialysis cleft, the haptics of an IOL can be used as an internal cerclage during cataract or secondary IOL surgery to effectively close the cleft by direct apposition of the ciliary body to the overlying sclera.

Adult↗

PubMed2000

Effect of mixing technique on the properties of acrylic bone-cement: a comparison of syringe and bowl mixing systems.

Syringe mixing systems have been introduced, but few data exist regarding the mechanical performance of cement they produce. We compared the properties of polymethyl methacrylate cement produced by these systems with that produced by a multiaxial bowl. Mixtures of cement were prepared using the Optivac, Cemvac, and Summit syringes and the Summit bowl. The mixtures were cured in molds to create casts that were radiographed and analyzed for void content, then cut into strips, weighed, measured, and tested to failure in 4-point bending. Syringe-mixed cement was of greater density, bending modulus, and bending strength than bowl-mixed cement (Mann-Whitney, P < .01) and contained fewer microvoids and macrovoids (Mann-Whitney, P < .01). No significant differences between the syringes were found for these variables (Kruskall-Wallis, P > .05).

Bone Cements↗