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PubMed2005

Silicone intubation with trans-sac fixation to prevent tube dislocation.

PURPOSE: To report a new technique for silicone tube fixation, after successful intubation for congenital nasolacrimal duct obstruction, to minimize its lateral dislocation. METHODS: Thirty patients (40 eyes) aged 20 months to 5 years (median, 28 months) were treated using the Ritleng bicanalicular lacrimal intubation system. After drawing the silicone stent out of the nose, a piece of 7-O Prolene suture was tied securely around one of its limbs. This limb was then pulled up, pulling the tied end of the Prolene suture to the medial canthal area. The same procedure was repeated with the other limb of the stent, pulling up the other Prolene suture end. This suture end was then un-tied. After adjusting the exposed silicone loop, the free end of the Prolene suture was tied securely to the corresponding part of the silicon stent. The nasally drawn two ends of silicone tube were tied in a single square knot. After 2 to 3 months, stents were removed in the medical office for all the patients. RESULTS: This technique was used successfully for all the patients. Of the 40 tubes in this study, 39 did not displace and one tube was displaced laterally due to loosely tied Prolene suture. On follow-up, the trans-sac suture was well tolerated and no complications were noted. CONCLUSION: The trans-sac fixation suture prevents lateral displacement of square-knotted silicone tube, which still can be removed easily at the physician's office.

Child, Preschool↗
PubMed2004

Controlled release of a model antibacterial drug from a novel self-lubricating silicone biomaterial.

There is considerable interest in developing medical devices that provide controlled delivery of biologically active agents, for example, to reduce the incidence of device-related infection. Silicone elastomers are one of the commonest biomaterials used in medical device production. However, they have a relatively high coefficient of friction and the resulting lack of lubricity can cause pain and tissue damage on device insertion and removal. Novel silicone cross-linking agents have recently been reported that produce inherently 'self-lubricating' silicone elastomers with very low coefficients of friction. In this study, the model antibacterial drug metronidazole has been incorporated into these self-lubricating silicone elastomers to produce a novel bioactive biomaterial. The in vitro release characteristics of the bioactive component were evaluated as a function of cross-linker composition and drug loading. Although conventional matrix-type release kinetics were observed for metronidazole from the silicone systems, it was also observed that increasing the concentration of the cross-linking agent responsible for the lubricious character (tetra(oleyloxy)silane) relative to that of the standard non-lubricious cross-linking agent (tetrapropoxysilane) produced an increase in the metronidazole flux rate by up to 65% for a specified drug loading. The results highlight the potential for developing lubricious silicone medical devices with enhanced drug release characteristics.

Anti-Bacterial Agents↗
PubMed2006

Hydrophobic acrylic and plate-haptic silicone intraocular lens implantation in diabetic patients: pilot randomized clinical trial.

PURPOSE: To compare the capsular and uveal reaction after implantation of a plate-haptic silicone intraocular lens (IOL) (C11UB, Chiron) and a hydrophobic acrylic (AcrySof MA60, Alcon) IOL in diabetic patients. SETTING: Moorfields Eye Hospital and St. Thomas' Hospital, London, United Kingdom. METHODS: Thirty-five diabetic patients were recruited consecutively and randomly assigned to have implantation of either of the 2 IOLs. The percentage area of posterior capsule opacification (PCO), anterior capsule contraction (ACC), and postoperative inflammatory indices (flare and cells) were assessed objectively at 2 to 3 weeks, 6 months, and 1 year. Between-group and within-group analyses were conducted using the Student t test or Mann-Whitney test and Friedmann test, respectively. RESULTS: Between-group analysis showed the percentage area of PCO was significantly greater in patients with plate-haptic silicone IOLs at 6 and 12 months (P = .002). At 6 months, ACC was significantly greater in the plate-haptic group (P = .04), but the difference was not significant at 12 months. There was higher flare in the hydrophobic acrylic IOL group than in the plate-haptic silicone IOL group at 2 to 3 weeks (P = .08). Within-group analysis showed that over the follow-up period, the plate-haptic silicone group, but not the hydrophobic acrylic group, had a progressive increase in PCO (P = .003). In the hydrophobic acrylic group, but not the plate-haptic silicone group, there was a significant reduction in the mean anterior chamber flare value (P = .01). There was no significant difference in visual acuity or contrast sensitivity at any postoperative visit. CONCLUSION: In diabetic patients, hydrophobic acrylic IOLs can lead to an increased flare in the early postoperative period but they seem to be more favorable than plate-haptic silicone IOLs because the latter lead to more PCO.

Acrylic Resins↗
PubMed2005

High complication rate identified in sacrocolpopexy patients attributed to silicone mesh.

OBJECTIVES: To report on our experience using a preconfigured Y-shaped silicone-coated polyester mesh and polypropylene mesh for vaginal vault suspension. A variety of materials have been used for both open and laparoscopic sacrocolpopexy in the management of vaginal vault prolapse. Recently, a preconfigured Y-shaped silicone-coated polyester mesh was introduced to facilitate the vaginal cuff suspension to the sacrum. METHODS: We reviewed the data of 45 consecutive patients who underwent abdominal (n = 28) or laparoscopic (n = 17) sacrocolpopexy. Of the 45 patients, 21 underwent silicone mesh suspension of the vaginal cuff to the anterior sacrum, with a mean follow-up of 23 months (range 16 to 41). A comparative analysis was performed of 24 patients who underwent the same procedure with polypropylene mesh. RESULTS: Of the 21 patients in the silicone group, 5 (23.8%) have had a major complication (four vaginal mesh erosions and one mesh infection) after a median follow-up of 9.5 months (range 4 to 20). The presenting symptoms were persistent or new vaginal discharge and/or nonspecific pelvic pain. One patient underwent successful removal of the mesh transvaginally, but the rest required abdominal exploration. To date, the 24 patients who underwent vaginal cuff suspension with polypropylene mesh have had no vaginal mesh extrusions or infections, with a mean follow-up of 12 months (range 1 to 38). CONCLUSIONS: Silicone-coated polyester mesh has recently been associated with a high rate of vaginal erosion when used as a transvaginal suburethral sling. Our experience specifically with vaginal vault suspension corroborates this. We have abandoned the use of silicone mesh because of the unacceptably high extrusion rate and presently use polypropylene mesh.

Aged↗
PubMed1989

Results of silicone oil removal in advanced proliferative vitreoretinopathy.

We reviewed the results of silicone oil removal after vitreous surgery for recurrent retinal detachment with proliferative vitreoretinopathy in 55 eyes. The minimum follow-up period was six months. Retinal detachment recurred in five eyes (9%). Evidence of recurrent epiretinal membrane formation at the time of or after silicone oil removal was noted in 21 eyes (38%). Penetrating keratoplasty combined with silicone oil removal was successful in five of six patients. Mild corneal changes noted in ten eyes (18%) remained the same or cleared in seven eyes after silicone oil removal. Overall, postoperative visual acuity improved in 24 eyes (44%), remained the same in 18 eyes (33%), and decreased in 13 (24%). In 22 eyes without clinical evidence of silicone-associated complications at the time of silicone oil removal, postoperative visual acuity remained unchanged or improved in 20 (91%).

Cornea↗
PubMed1990

Magnetic resonance imaging in the evaluation of vitreoretinal disease in eyes with intraocular silicone oil.

Media opacification in eyes filled with silicone oil makes the evaluation of recurrent retinal detachment difficult. Ultrasonography through silicone oil is subject to significant imaging artifacts. We performed magnetic resonance imaging on six patients with unilateral intravitreal silicone oil to determine if the technique would detect detached retina and subretinal oil. All patients had undergone pars plana vitrectomy with silicone oil injection for proliferative vitreoretinopathy; five patients had encircling solid silicone scleral buckles. In five patients the media were clear, and ophthalmoscopic findings were correlated with magnetic resonance findings. Four patients had recurrence of inferior retinal detachment; magnetic resonance imaging demonstrated subretinal oil in three of these patients. One patient had a concentric, shallow, anterior retinal detachment; magnetic resonance scanning demonstrated a globular hyperintensity suggestive of subretinal oil. In the sixth patient, who had an opaque cornea, magnetic resonance imaging suggested that the retina was attached preoperatively; this was confirmed at subsequent surgery. A chemical shift artifact was helpful in defining the contour of retinal detachments and the presence of subretinal oil by outlining the silicone oil within the eye.

Eye↗
PubMed1999

Silicone soft socket system: its effect on the rehabilitation of geriatric patients with transfemoral amputations.

OBJECTIVE: To report the effect of supplying new transfemoral amputee patients with a prosthesis with a silicone suspension/interface system. PATIENTS AND DESIGN: Fifty-eight new transfemoral amputee patients were supplied with a contoured adducted trochanteric-controlled alignment method (CAT-CAM) socket (CCS) with a silicone suspension/interface system. This system is called the Icelandic roll-on silicone socket, or the ICEROSS system (IRS). A second group of 18 new amputee patients were supplied with an unlined CCS (uCCS), ie, without silicone sleeve suspension. MEASURES: The IRS group was followed up at 1 year, the uCCS group at 9 months. Ambulatory capacity was investigated by first categorizing patients' prosthetic mobility into four different groups based on the distances patients were able to ambulate: 0 m (wheelchair ambulation only), <100 m, 100 to 500 m, and >500 m. The change in distance ambulated was then determined for each group for the three time intervals between admission, discharge, and follow-up. RESULTS: Between discharge and follow-up patients with the IRS had a significantly greater improvement (p<.001) in distance traversed than patients supplied with the uCCS. Distance traversed had been longer in the uCCS group before they were supplied with the prostheses (p<.05). Inpatient stay in the rehabilitation center was 5 days less in the group supplied with IRS (p<.05). Adjustments to the new socket had to be carried out for 67% of the uCCS group during the observation period, compared with only 21% for those using the IRS system. Satisfaction, average duration of daily use, and the use of assistive devices for gait did not differ significantly. CONCLUSIONS: New patients with transfemoral amputations fitted with a silicone suction socket showed greater gains in distances ambulated, and adjustments to their prostheses were significantly fewer. Therefore, it is preferable to provide these sockets to geriatric amputee patients rather than CAT-CAM sockets without silicone suspension sleeves.

Aged↗
PubMed1996

Patient satisfaction following insertion of silicone breast implants.

Because of allegations linking silicone implants with cancer and connective tissue diseases and mounting media coverage, women with silicone breast implants are extremely concerned, despite the lack of evidence showing a link between silicone gel-filled breast implants and connective tissue diseases or cancer. To assess whether or not this group of women were satisfied with their operations, we sent all women who had silicone breast implants inserted in the south-east of Scotland between 1982 and 1991 a quality of life questionnaire. One hundred and two breast augmentation and 212 breast reconstruction patients replied. Not everyone answered every question. The majority of women in our study, 84% (79/94) and 91.8% (192/209) of augmented and reconstructed patients, respectively, stated that they were satisfied with their operations, although only about half were very satisfied. Although 91.2% (270/296) of all the women were aware of the allegations with 29.7% (88/296) concerned, only 3% (9/296) of all the women felt that there was cause for concern. It would appear that, although most women with silicone breast implants are aware of the accusations regarding silicone and systemic illnesses, the adverse publicity has only given a small number of them a cause for concern and the majority are satisfied with the outcome of their operation and perceive the benefits to outweigh the risks.

Adolescent↗
PubMed1998

Determination of silicon in urine by inductive coupled plasma-optical emission spectroscopy.

We describe an inductive coupled plasma-optical emission spectroscopic method to determine silicon in spot urine specimens. A 6-fold standard addition series of the urine specimen ranging from 0 to 356 micromol/l silicon was applied, and the method meets the requirement of matrix compensation in a frequently changing environment. The inter-assay variation was +/-3.0%, intra-assay variations for three specimens were +/-1.7%, +/-1.1% and +/-0.84%. To compensate for physiological variations of urine density, the silicon concentrations in urine were related to urinary creatinine which was measured in parallel by reversed-phase HPLC. Urinary silicon concentrations were examined in 43 healthy controls from the local population. The 5th-95th percentile was 12.6-237 micromol/mmol creatinine. A follow-up of three people over a period of 14 days showed that intra-individual variations of urinary silicon concentrations were smaller than variations between individuals, especially when silicon is related to creatinine.

Chromatography, High Pressure Liquid↗
PubMed1996

Intraocular silicone oil for retinal detachment in AIDS: CT and MR appearances.

AIM: To describe the CT and MR features of intraocular silicone oil which is used to treat complex retinal detachments in patients with acquired immune deficiency syndrome (AIDS). PATIENTS AND METHODS: Seven male patients with AIDS were treated by pars plana vitrectomy and intraocular silicone oil injection for complex retinal detachments due to biopsy proven cytomegalovirus retinitis. Two patients had bilateral therapy. RESULTS: Silicone oil was hyperdense to muscle on CT with attenuation values of 106-139 HU (mean 115, SD 4.5). On MR, when compared with normal vitreous, intraocular silicone oil appeared hyperintense on T1-, proton density, and T2-weighted spin-echo sequences. A chemical shift artifact was seen on all MR images, being most marked on the T2-weighted images. CONCLUSION: The high attenuation value of silicone oil on CT and its hyperintensity on T1 weighted MR images my cause diagnostic confusion with haemorrhage. These entities can be distinguished at CT by directly measuring the attenuation number (silicone oil > 100 HU; blood < 90 HU), and at MR by the presence of a chemical shift artifact.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Lipid uptake by silicone enteral access feeding devices.

BACKGROUND/PURPOSE: Deterioration of long-term enteral access devices remains a significant patient care and financial problem. Because it is known that lipids, particularly medium-chain triglycerides oil (MCT oil), can soften and break certain types of polymeric materials, the authors evaluated the effect of liquid enteral feeding formulas containing different amounts of MCT oil on silicone feeding tubes. METHODS: Commercially available and widely used gastrostomy silicone catheters of two sizes (20F and 15F) were sectioned in 5-cm-long samples and cleaned. Five groups of five pieces were immersed for 8 weeks in pure MCT oil and in four commercial formulas having similar protein, carbohydrate, and fat contents. These formulas were chosen because they contained similar percentages of fat (37% to 45%), although they contained differing amounts of MCT oil. Sodium azide 0.05% was added as a bactericide. Samples were maintained at 37 degrees C in an incubator-shaker. After incubation, specimens were rinsed, dried, and weighed. Selected samples were extracted with a chloroform-methanol solution (2:1). Super-critical fluid chromatography (SFC) and infrared (IR) spectroscopy were performed. A tensile tester was used to generate force-elongation curves for the remaining samples. A statistical analysis (ANOVA, alpha = .05) was conducted to compare data from test groups with results from 20 samples of control silicone material. RESULTS: Data demonstrate that silicone is significantly affected by liquid formulas and pure MCT oil. SFC and IR findings indicated that fractions of MCT oil, corn oil, and canola oil were absorbed by the material. The most dramatic weight gain (3.7%) was observed for specimens immersed in pure MCT oil. An average increase (9.6%) of silicone compliance was measured along with oil migration in the tubing. CONCLUSIONS: Lipid uptake contributes significantly to deterioration of the silicone tested, leading to device failure. Surface damage can create a potential nidus for microorganisms, particularly fungi. Lipid type and rate of administration should be taken into account when long-term enteral feedings are given. These data contribute to the understanding of the causes of the physico-chemical deterioration of long-term enteral feeding devices and provide helpful information for the design and manufacture of improved products.

Enteral Nutrition↗
PubMed1999

Color stability of facial silicone prosthetic polymers after outdoor weathering.

STATEMENT OF PROBLEM: Color deterioration of silicone prosthetic elastomers affects the life expectancy of facial prostheses in a service environment. PURPOSE: This study investigated the color stability of 3 nonpigmented silicone elastomers (Silskin 2000, Elastosil M3500, Ideal) exposed to outdoor weathering for 1 year. MATERIAL AND METHODS: A tristimulus colorimeter was used to evaluate the color differences (DeltaE*) of the silicone elastomers every 2 months. Ten disk-shaped specimens for each material were tested. Data were analyzed with a repeated measures ANOVA and Student-Newman-Keuls test at a significance level of alpha = .05. RESULTS: All silicone elastomers showed visually detectable, mean color differences (DeltaE* > 2.0), that ranged from 2.13 to 3.98. Silskin 2000 showed greater color differences (P <.05) compared with Elastosil M3500 and Ideal, which showed similar behavior (P >.05). CONCLUSION: Outdoor exposure of silicone facial elastomers for 1 year resulted in visually detectable color differences. Duration of exposure and silicone elastomer were significant factors that affected color stability. Silskin 2000 was significantly less color stable than Elastosil M3500 and Ideal, which were not statistically significantly different from each other.

Analysis of Variance↗
PubMed2002

In vitro and in vivo antimicrobial activity of covalently coupled quaternary ammonium silane coatings on silicone rubber.

Biomaterial-centered infection is a dreaded complication associated with the use of biomedical implants. In this paper, the antimicrobial activity of silicone rubber with a covalently coupled 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride (QAS) coating was studied in vitro and in vivo. Gram-positive Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis HBH, 102, and Gram-negative Esherichia coli O2K2 and Pseudomonas aeruginos AK1 were seeded on silicone rubber with and without QAS-coating, in the absence or presence of adsorbed human plasma proteins. The viability of the adherent bacteria was determined using a live/dead fluorescent stain and a confocal laser scanning microscope. The coating reduced the viability of adherent staphylococci from 90% to 0%), and of Gram-negative bacteria from 90% to 25% while the presencc of adsorbed plasma proteins had little influence. The biomaterials were also subcutaneously implanted in rats for 3 or 7 days, while pre- or postoperatively seeded with S. aureus ATCC 12600. Preoperative seeding resulted in infection of 7 out of 8 silicone rubber implants against 1 out of 8 QAS-coated silicone rubber implants. Postoperative seeding resulted in similar infection incidences on both implant types, but the numbers of adhering bacteria were 70% lower on QAS-coated silicone rubber. In conclusion, QAS-coated silicone rubber shows antimicrobial properties against adhering bacteria, both in vitro and in vivo.

Adsorption↗
PubMed2002

Immobilization of RGD to < 1 1 1 > silicon surfaces for enhanced cell adhesion and proliferation.

The ability of biomaterial surfaces to regulate cell behavior requires control over surface chemistry and microstructure. One of the greatest challenges with silicon-based biomedical microdevices such as those recently developed for neural stimulation, implantable encapsulation, biosensors, and drug delivery, is to improve biocompatibility and tissue integration. This may be achieved by modifying the exposed silicon surface with bioactive peptides. In this study, Arg-Gly-Asp (RGD) peptide conjugated surfaces were prepared and characterized. The effect of these surfaces on fibroblast adhesion and proliferation was examined over 4 days. Silicon surfaces coupled with a synthetic RGD peptide, as characterized with X-ray photoelectron spectroscopy and atomic force microscopy, display enhanced cell proliferation and bioactivity. Results demonstrate an almost three-fold greater cell attachment! proliferation on RGD immobilized surfaces compared to unmodified (control) silicon surfaces. Modulating the biological response of inorganic materials such as silicon will allow us to design more appropriate interfaces for implantable diagnostic and therapeutic silicon-based microdevices.

Animals↗
PubMed2003

Neutron powder diffraction studies of silicon-substituted hydroxyapatite.

The incorporation of a small amount of silicon in the hydroxyapatite (HAp) lattice is known to improve the bioactivity of the material. The effect of silicon substitution was studied by comparing samples of pure and 0.4wt% silicon-substituted HAp prepared by an aqueous precipitation method. High-resolution neutron powder diffraction and Rietveld refinement methods were used to investigate the effect of silicon substitution on the crystal structure parameters of the HAp lattice from room temperature down to 20K. Small structural changes in the lattice constants, interatomic distances, site occupancies and distortion of the phosphate tetrahedron were found. Modifications of the Fourier transform infrared spectra as well as appearance of new modes were observed in the silicon-substituted sample. Heat treatment and silicon substitution also affected the morphology and crystallinity of this bioapatite.

Biocompatible Materials↗
PubMed1999

Sol-gel modification of silicone to induce apatite-forming ability.

Silicones formed with silanol groups on their surfaces were prepared by partial hydrolysis and polycondensation of tetraethoxysilane (TEOS) dispersed in silicones in molecular scale. Although the silanol-modified silicones thus prepared formed no apatite in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma within 21 d, they formed a bone-like apatite layer in situ on their surfaces in a solution (1.5 SBF) with ion concentrations 1.5 times the SBF within 7 d. This indicates that the silanol groups formed on the silicones by the present method can induce the apatite nucleation in 1.5 SBF and hence, apatite-coated silicones can be fabricated by a biomimetic process. Apatite-silicone composites thus prepared could exhibit mechanical properties analogous to the natural bone as well as bioactivity.

Apatites↗
PubMed2003

Foreign body episcleral granulomas complicating intravitreal silicone oil tamponade: a clinicopathological study.

PURPOSE: To report two patients with lipid granulomas of the episclera complicating vitrectomy and silicone oil tamponade. DESIGN: Two observational case reports. INTERVENTION: Patient 1, a 41-year-old woman, underwent vitrectomy with silicone oil tamponade for proliferative diabetic retinopathy. Four weeks later, she sought treatment for inflamed episcleral nodules adjacent to one of the sclerostomy sites. The oil was removed and the episcleral nodules were excised. Patient 2, a 33-year-old man, underwent vitrectomy and silicone oil tamponade for tractional retinal detachment. He experienced a painful blind eye with episcleral nodule that required enucleation. MAIN OUTCOME MEASURES: On histopathological analysis, both specimens demonstrated episcleral granulomas caused by silicone oil. CONCLUSIONS: Episcleral nodules adjacent to vitrectomy entry sites with silicone oil tamponade may represent lipid granulomas, probably caused by silicone oil leakage from scleral entry ports.

Adult↗
PubMed1996

Silicone frontalis slings for the correction of blepharoptosis: indications and efficacy.

PURPOSE: To determine the efficacy of silicone rod frontalis sling ptosis repair in selected patients. METHODS: The authors retrospectively studied 35 consecutive patients who underwent silicone sling ptosis repairs in 6 lids at the University of California, San Francisco. RESULTS: Preoperative diagnoses included congenital ptosis causing developmental delay or possible amblyopia in children younger than 3 years of age, chronic progressive external ophthalmoplegia, third-nerve palsy, myasthenia gravis, and ocular restriction secondary to glaucoma filtering valves. With a mean follow-up of 22 months, good-to excellent final lid height was achieved in all 61 lids. Recurrence of the ptosis occurred in four lids (7%), requiring replacement of the silicone rod in two lids and revision of the original sling in two lids to reach the final lid height. Chronic exposure keratopathy without corneal infection occurred postoperatively in 9 (15%) of 61 eyes, all in patients with an inadequate or absent Bell phenomenon. Chronic corneal problems did not develop in any of the children. Extrusion of the sling with or without infection occurred in three foreheads (5%) in two patients younger than 15 years of age. CONCLUSION: Silicone rod is an effective material for use in frontalis suspension in treating severe ptosis with poor levator function. Children younger than 3 years of age with congenital ptosis and developmental delay or possible amblyopia can undergo silicone frontalis suspension to achieve good visual results. The elasticity and ease of adjustment of the silicone rod are ideal characteristics for a suspensory material used to correct severe ptosis associated with a minimal or absent Bell phenomenon, such as in chronic progressive external ophthalmoplegia, myasthenia gravis, or third-nerve palsy.

Adolescent↗