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PubMed1998

Lipid infiltration as a possible biologic cause of silicone gel breast implant aging.

The cause of silicone gel implant aging and rupture is not known. Recent reports indicate the failure rate is higher than previously published, and implant aging and rupture may be due to progressive mechanical deterioration of the outer vulcanized silicone shell. It is known that lipids are absorbed by the hydrophobic silicone elastomer, and lipid infiltration causes mechanical attenuation and possible failure of the elastomer. The purposes of this article are to analyze the silicone envelope/gel of explanted prostheses and the silicone elastomer of other medical grade silicone devices for lipid content and to suggest its possible role in implant aging and rupture. We assayed 33 ruptured silicone breast implant shells (mean age 13.1 years; range 8 to 26 years) and 8 medical grade silicone elastomer devices (mean age 3.7 years; range 3 months to 12 years) for evidence of lipid infiltration using thin layer chromatography. These were compared with control group assays from two nonimplanted silicone gel implants and one unused Silastic catheter. Ninety-eight percent of implants and other previously implanted silicone devices were found to have evidence of lipid infiltration compared with none in nonimplanted controls (p < 0.005). We conclude that lipids infiltrate the outer silicone shell and may be a factor related to breast implant aging and rupture due to progressive mechanical weakening of the outer silicone shell.

Breast Implantation↗
PubMed2003

[Silicon forms and its role in infant food].

This paper presents an attempt to assess the total content of silicon and its potentially bioavailable forms to the baby body in milk nutrient and baby foods. The measurements of the total and bioavailable silicon were conducted with the use of two analytical methods. The method of atomic absorption spectroscopy (AAS) was used for the determination of total silicon content. Bioavailable silicon was determined by means of visible light spectroscopy (VIS) with ammonium molybdate. In the group milk products the largest amount of total silicon was found in Mlekovita milk -0.54 mg/l, and Humana 2 milk formula contained the largest amount of ionised silicon-0.24 mg/l. In baby foods manufactured by Gerber the total amount of silicon was high and the average content stood at 27 mg/kg in dry matter. The largest amount of total silicon was found in Vegetables and Ham-48.19 mg/kg in dry matter, as well as bioavailable silicon--4.13 mg/kg in dry matter. Compare level of silicon in milk nutrient and baby foods to silicon content in human milk 0.05 mg/l, it was found that large excess of silicon in this foodstuffs.

Animals↗
PubMed2005

[Histopathological and ultrastructural characteristics of oil-associated complications in silicone oil-filled human eyes].

OBJECTIVE: To observe morphological changes of oil-associated complications in silicone oil-filled human eyes, and to further explore their pathogenesis. METHODS: The morphology analysis and immunohistochemistrical study were performed in 25 specimens including 8 eyeballs, 1 ocular content, 4 preretinal membranes, 4 corneal buttons and 8 lens from human eyes with silicone oil tamponade. Two of preretinal membranes acquired freshly were also evaluated by transmission electron microscopy (TEM). RESULTS: Endothelium cell loss (90%) and band keratopathy (83%) were the most typical changes in silicone oil-associated keratopathy;while epithelial cell fibrosis was the most frequent histopathological features in silicone oil-associated cataract. In 8 eyeballs and 1 ocular content, it was found that damages to normal retinal layers and formation of preretinal or subretinal membrane with extensive silicone bubbles were obvious in the cases of silicone oil-associated retinopathy, which included loss and degeneration of neuron cells. Moreover, in 3 eyeballs with silicone oil for more than 60 months, retinas were completely replaced by fibril membranes, and the oil vacuoles were also found in sclerocorneal scar, trabecula, iris, ciliary body, choroid, optic nerve and its tunica vaginalis. These finding demonstrated that the longer the silicone oil was retained in eyeballs, the more severe its complications were. Different sizes of silicone bubbles in 2 preretinal membranes were noted easier by TEM than light microscopy. There were some macrophages marker (CD68) positive staining cells in the tissues filled with silicone bubbles, such as preretinal or subretinal membrane and optic nerve. Partial of the membranes surrounding the oil bubbles was positive for GFAP staining, and other part was positive stained for Vimentin. CONCLUSIONS: Intraocular silicone oil can damage the normal tissue structures and function if it is retained in eyeballs too long. This results suggest that silicone oil should be removed timely after the retinal reattachment stabilized and can not be used as a kind of long term intraocular tamponade.

Adolescent↗
PubMedDate not supplied

[Silicone oil in the surgical treatment of retinal detachment--indications and clinical experience].

Silicone oil is being used with increased frequency for retinal tamponade during vitreous surgery for complicated retinal detachments. Though it is now possible to reattach most detached retinas, the visual outcome of the silicone oil procedure is often disappointing. This is due to the well known complications of silicone oil (i.e. cataract, glaucoma, corneal opacification), and the necessity to remove the silicone oil in a second surgical procedure with a certain risk of redetachment. Possible toxicity to retina and optic nerve has not yet get been completely evaluated. An alternative method is the use of expanding gases for internal retinal tamponade. Expanding gases are not as effective as silicone oil in advanced stages of proliferative vitreoretinopathy (PVR), but are afflicted with much less complications. We reviewed the charts of our patients, operated on for retinal detachment, to analyse the anatomical and functional results with silicone oil versus gas tamponade. Regarding the last 421 consecutive surgical procedures for retinal detachment (368 eyes), silicone oil has been used in 5%, expanding gases in 14%. The silicone oil procedure was restricted to the most advanced cases of PVR. The anatomic success rate with silicone was 72%, with gas tamponade 87%. Visual acuity of 0.05 and better achieved 19% of the eyes treated with silicone oil versus 61% of the eyes with gas tamponade. These results confirm the findings of other investigators: despite of the high anatomic success rate with silicone oil, the functional results are poor. Because many complicated cases of retinal detachment can also be treated successfully with gas tamponade, silicone oil should remain the last step in retinal detachment surgery.

Humans↗
PubMed1991

[Possibilities of silicone oil removal after complex vitreoretinal surgery].

The question of the long-term risks and benefits of silicone oil removal after complex vitreoretinal surgery involving the use of silicone oil has not yet been answered. A consecutive series of 50 eyes from which silicone oil had been removed were therefore analyzed in a retrospective study. In all cases the retina was completely attached and seemed to be stabilized before silicone oil removal. The reasons for the original surgery were severe proliferative diabetic retinopathy (PDR) in 20 cases and proliferative vitreoretinopathy (PVR) in 30, in 2 of which PVR developed after perforating injuries. Silicone oil was removed because the retina was clinically stable and completely attached, and in some cases cataract or glaucoma was present. The complication rate after silicone oil removal in these situations varied widely in dependence on the form of disease. After PDR stable conditions were achieved in 70% of cases after silicone oil removal. After PVR with retinal detachment the situation remained stable in only 50%. The most frequent complication was retinal redetachment because of recurrent PVR, accounting for 80% of all failures. The success rate with silicone oil removal after PDR in this study was independent of the duration of tamponade, which had lasted for about 1 year in most cases. Following PVR, silicone oil removal seems to be more safer after long-term tamponade (22 months) than after a shorter duration (12 months). Secondary glaucoma during silicone oil tamponade could be influenced positively in 70% of all cases by silicone oil removal. Because of the relatively high rate of complications after silicone oil removal, especially in PVR, the indications for removal must be carefully considered.

Adolescent↗
PubMed1989

[Some properties of hydrophilic addition-type silicone impression materials].

Addition-type silicone impression materials have the characteristic of low wetting by water; therefore, they are sometimes inconvenient in clinical use. However, hydrophilic addition-type silicone impression materials are said to be improved in this characteristic. In this study, the physical properties of two kinds of hydrophilic addition-type silicone impression materials, namely, Hydrophilic EXAFLEX and EXPRESS, were investigated and compared with the traditional addition-type silicone impression materials. Compression set, strain in compression, consistency, and contact angles of the salivary droplet on the these impression materials were measured in accordance with ADAS no. 19. The following results were obtained: 1. Each compression set of HEM, HEL, EPM, EPL, EPE (hydrophilic addition-type silicone impression materials), having superior property in compression recovering, was less than 0.1%, they were equivalent to one-seventh of that of the traditional addition-type silicone impression materials. 2. Strain in compression of HEM, HEL, EPM, EPF was bigger than that of the traditional addition-type silicone impression materials. 3. Consistency of HEM, HEL, EPM, EPL, EPF was smaller in fluidity than that of the traditional addition-type silicone impression materials. Among all impression materials in this study, only with HEM and HEL could a difference in consistency between wet films and dry films be recognized. 4. Contact angles of all hydrophilic addition-type silicone impression materials were smaller than those of the traditional addition-type silicone impression materials. They were equivalent to two-thirds of that of the traditional addition-type silicone impression materials, and improvement in wetting property of these hydrophilic addition-type silicone impression materials was observed.

Dental Impression Materials↗
PubMed1994

Intraocular silicone oil: in vitro and in vivo MR and CT characteristics.

PURPOSE: To describe the CT and MR characteristics of intraocular silicone oil (polydimethylsiloxane), which is used with increasing frequency to treat complicated retinal detachments. METHODS: CT was performed on a silicone oil/water phantom and on a patient with retinal detachments secondary to cytomegalovirus retinitis, treated by bilateral intraocular injections of silicone oil. CT appearance and CT number of silicone oil were evaluated. Proton MR spectroscopy was performed with a 200-MHz spectrometer on a sample of polydimethylsiloxane within a tube of deuterated water. MR imaging was performed on a silicone oil/water phantom and on two patients with retinal detachments treated with silicone oil injection. RESULTS: Silicone oil is relatively radiodense; its CT attenuation is approximately 130 HU. On spectroscopy, silicone oil gave a single peak at 0.33 ppm. Relative to water silicone oil was hyperintense on T1-weighted images and hypointense on spin-density and T2-weighted images. Estimated T1 and T2 were 716 msec and 68 msec, respectively. Chemical shift artifacts were seen on MR images and were exaggerated when a narrow sampling bandwidth was used. In clinical cases spectral saturation pulses normally used for lipid suppression could be adjusted to saturate only the silicone resonance; in this way, the chemical shift artifact was eliminated. CONCLUSION: Intraocular silicone oil has unique imaging characteristics with which radiologists must become familiar. These characteristics include high attenuation on CT and hyperintensity on T1-weighted MR, both of which may mimic hemorrhage. Elimination of the prominent chemical shift artifact on MR with selective saturation of the silicone resonance improves evaluation of the globe.

AIDS-Related Opportunistic Infections↗
PubMed1996

[Intraocular silicone oil tamponade. A clinico-pathologic study of 36 enucleated eyes].

BACKGROUND: Previous histological studies have shown that intraocular silicone oil induces irreversible changes in ocular tissues, especially the retina. The purpose of this study was to analyze, in a larger group of enucleated eyes, changes in intraocular tissue after silicone oil injection, dependent on intraocular pressure, how long the oil was in the eye, and the viscosity of intraocular silicone oil. PATIENTS AND METHODS: We did histological examinations on 36 enucleated globes with intraocular silicone oil after vitreoretinal surgery and compared them with 68 enucleated globes treated with buckle and encircling band using immunohistochemistry (n = 5) and electron microscopy (n = 7). For statistical evaluation we used the chi(2) test and analysis of variance. RESULTS: After silicone oil injection we observed a more pronounced reduction in corneal endothelial cells (58%), more frequent closed chamber angle (86%), atrophy of the ciliary body (80%) (P < 0.05), proliferative vitreoretinopathy (89%), and glaucomatous atrophy of the optic nerve (56%) (P < 0.01). The retinae showed independent of the use of silicone oil a loss of inner and outer segments of photoreceptors and of ganglion cells and thinning and rareficaton of all other retinal layers. Globes with silicone oil revealed vacuoles both free and incorporated by macrophages in all layers of the retina. Similar vacuoles were seen in the optic nerve, choroid, retinal pigment epithelium, ciliary body, iris, chamber angle and the corneal endothelium. Silicone oil vacuoles were seen in the retina and optic nerve by 1 month after surgery in two eyes with high intraocular pressure (42 mmHg). Six of eight eyes with normal intraocular pressure levels showed retinal vacuoles, 3 of them after 2 months. Vacuoles in the optic nerve were found in eight of nine eyes with intraocular instillation of 1000 mPa silicone oil. There was no clinicohistopathological correlation between the presence of vacuoles in the retina or optic nerve and the duration and viscosity of intraocular silicone oil. CONCLUSIONS: This study suggests that vacuoles in eyes with silicone oil instillation can be found in the retina after 4 weeks. The period of intraocular silicone oil should be limited to 3-6 months.

Diabetic Retinopathy↗
PubMed1995

[Long-term outcome after silicone oil removal].

In order to reduce the incidence of postoperative complications in silicone-filled eyes, many authors recommend that silicone oil should be removed from the eye as soon as a stable retinal situation is achieved. Even in the eyes with completely attached retina and a clinically stable situation there is a risk of retinal redetachment and other complications after silicone oil removal. In a retrospective study we analyzed 324 cases after silicone oil removal regarding the postoperative redetachment rate and risk of complications from this procedure. The indication for primary surgery was retinal detachment with PVR in 167 (51.5%) cases, proliferative diabetic retinopathy in 87 cases (26.8%), complications of penetrating ocular injuries in 48 cases (14.8%), giant tear retinal detachment in 9 cases (2.7%) and retinal detachment with a central hole in 13 cases (4%). At the time of silicone oil removal retina was completely attached in 277 eyes. Local retinal redetachment central to the encircling band existed in 47 eyes at the time of silicone removal. Follow-up time ranged from 6-63 months. Silicone oil removal was combined with a cataract operation in 42 cases (12.9%), penetrating keratoplasty in 9 cases (2.8%) and membrane peeling in 54 eyes (16.7). In the postoperative period the retina detached in 39 (12%) eyes. In the eyes with preoperatively completely attached retinas, redetachment occurred in 23 eyes (8%), whereas in the group of eyes with an unstable preoperative retinal situation, the retina redetached in 16 eyes (34%). The duration of the silicone oil tamponade had no effect on the redetachment rate. In the group of eyes with an unstable preoperative retinal situation, preoperative laser photocoagulation at the cerelage buckle, as well as central to the local detachment, reduced the incidence of redetachment after silicone oil removal significantly (25% vs. 53%). In the group of eyes with a preoperatively stable retinal situation, this effect was not significant. Our results show that in eyes with completely attached retinas, the risk of complications and redetachment after silicone oil removal is relatively low. In selected cases, even in eyes with incompletely attached retinas, silicone oil could be removed. Nevertheless, a relatively high risk of postoperative complications has to be taken into consideration. In eyes with an incompletely attached retina, preoperative laser photocoagulation at the cerclage buckle, as well as central to the local redetachment significantly reduced the incidence of redetachment after silicone oil removal.

Adult↗
PubMed1999

Silicone oil removal using a self-sealing corneal incision under topical anesthesia.

BACKGROUND AND OBJECTIVE: To report the results of silicone oil removal from aphakic eyes using a self-sealing clear corneal incision under topical anesthesia. PATIENTS AND METHODS: Twenty-two eyes of 22 patients who had pars plana vitrectomy combined with silicone oil injection underwent silicone oil removal under topical anesthesia using a self-sealing clear corneal incision. Mean time between silicone oil injection and removal was 3.1+/-1.42 months. Fourteen eyes were filled with 1300 cs of silicone oil and 8 eyes were filled with 5700 cs of silicone oil. The removal was performed with passive washout in the eyes filled with 1300 cs of silicone oil and with active aspiration in the eyes filled with 5700 cs of silicone oil. RESULTS: All of the 22 silicone oil removal procedures performed under topical anesthesia had clear corneal incisions that did not require suturing at the end of surgery. Three cases that had 1300 cs of silicone oil required aspiration because of residual silicone oil bubbles. CONCLUSION: Silicone oil can be removed from the aphakic eye using a self-sealing corneal tunnel incision under topical anesthesia.

Adult↗
PubMed1990

Interactive effects of dietary silicon, copper, and zinc in the rat.

A factorial rat experiment using two dietary concentrations each of copper, zinc, and silicon was conducted to identify areas in which interrelationships involving silicon may exist. The concentrations used were (mg/kg of diet): copper, 1 and 5; zinc, 2 and 12; and silicon, 5 and 270. An antagonism between silicon and zinc, whereby increases in dietary levels of either one resulted in a reduction in blood plasma concentrations of the other, was demonstrated. The depressing effect of silicon on plasma concentrations of zinc and on alkaline phosphatase occurred only in zinc-deficient rats. However, silicon had no effect on growth. Effects on aortic composition, interpreted as beneficial, accompanied increases in the silicon content of copper-deficient diets. Silicon-dependent increases in the chloroform-methanol extractable fraction of aorta closely approximated a similar response to copper. High dietary silicon increased aortic elastin in copper-deficient rats when dietary zinc was adequate. The aortic effects of silicon, while mimicking the gross effects of copper, occurred in the absence of any silicon-related changes in blood copper concentrations. Interrelationships of silicon with other elements, particularly copper and zinc, may warrant consideration in future nutritional and metabolic studies.

Journal Article↗
PubMed2003

Silicon-induced changes in viscoelastic properties of sorghum root cell walls.

Silicon is deposited in the endodermal tissue in sorghum (Sorghum bicolor L. Moench) roots. Its deposition is thought to protect vascular tissues in the stele against invasion by parasites and drying soil via hardening of endodermal cells. We studied the silicon-induced changes in mechanical properties of cell walls to clarify the role of silicon in sorghum root. Sorghum seedlings were grown in nutrient solution with or without silicon. The mechanical properties of cell walls were measured in three separated root zones: basal, apical and subapical. Silicon treatment decreased cell-wall extensibility in the basal zone of isolated stele tissues covered by endodermal inner tangential walls. The silicon-induced hardening of cell walls was also measured with increases in elastic moduli (E) and viscosity coefficients (eta). These results provided new evidence that silicon deposition might protect the stele as a mechanical barrier by hardening the cell walls of stele and endodermal tissues. In contrast to the basal zone, silicon treatment increased cell-wall extensibility in the apical and subapical zones with concomitant decrease in E and eta. Simultaneously, silicon promoted root elongation. When root elongation is promoted by silicon, one of the causal factors maybe the silicon-enhanced extensibility of cell walls in the growing zone.

Algorithms↗
PubMed1998

Static-electric field induction by a silicone cushion for the treatment of hypertrophic and keloid scars.

Silicone gel and silicone occlusive sheeting are widely used at present for the treatment of hypertrophic and keloid scars, without any scientific explanation as to their mode of action. In a recent paper the possibility was raised that static electricity generated by friction-activated silicone sheeting could be the reason for this effect, and that it can, with time, cause involution of hypertrophic and keloid scars. The objective of this study was to test this hypothesis and to observe whether a continuous and also an increased negatively charged static-electric field will shorten the treatment period. A device to implement these requirements gradually evolved over a 5-year period. A number of prototypes were tested until the final product was attained. Some of the patients in this study were treated initially with a silicone sponge inserted in the cushion. Later this version was changed to the final design described herein. A silicone cushion was developed with the purpose of increasing a negative static-electric charge to accelerate the regression process. The cushion is custom-made using a silicone occlusive sheeting envelope of 0.75-mm thickness, which does not deteriorate with use, and is partially filled with high viscosity silicone oil. Its edges are sealed, and its size is designed to extend a little beyond the scarred area. Static electricity readings, generated by activating the cushion by pumping action with the fingers, stretching or deforming the cushion, are invariably much higher when compared with those obtained with silicone occlusive sheeting and silicone gel sheeting. The interaction between the negatively charged ions of the cushion and the ionic charges of the tissue fluids may be the critical factor in achieving hypertrophic and keloid scars involution. Of the 30 patients enrolled in the study, 3 patients dropped out. Treatment with the silicone cushions yielded 63.3 percent cessation of itching and burning followed by pallor and flattening of the scar, some markedly so, over a few weeks to 6-month period. An additional 26.6 percent had their scars resolved in up to 12 months of treatment. Good contact of the cushion over the scar has been shown to be important in this clinical trial, and much creativity is needed for making elastic strap bindings that ensure this contact. The clinical trials extended over a 12-month period. Ten patients (33.3 percent) who had recalcitrant scars with little response to the use of the silicone cushion were given intralesional corticosteroid injections, in addition to the continued use of the cushion, resulting in a fairly rapid resolution of these scars over a period of months to a year.

Adolescent↗
PubMedDate not supplied

Interaction of intraocular lenses with various concentrations of silicone oil: an experimental study.

The aim of this study was to evaluate the interaction between various widely used intraocular lenses (IOLs) and silicone oils of different viscosities. Four groups of IOLs, including monoblock foldable hydrophilic acrylic IOLs (Morcher, type 92s); monoblock hydrophobic acrylic IOLs (Acrysof-SA60AT, Alcon); single-piece rigid polymethylmethacrylate (PMMA) IOLs (Intraocular Optical International-IOI-65130) and a three-piece foldable silicone optic IOL (CeeOn Edge 911A, Pharmacia UpJohn) were analyzed in vitro to determine the percentage adherence 1,000-centistoke, 1,300-centistoke or 5,000-centistokes silicone oil on the IOL optic. For each IOL type, there was no statistically significant difference in the mean silicone oil coverage (MSC) of the IOL optics for the different viscosities of silicone oil. Silicone IOLs had the highest MSC percentage (79.9%) whereas hydrophilic acrylic IOLs were the least silicone-covered IOLs (7.8%) compared to the other IOL types tested in this study. It is not the concentration of silicone oil that affects silicone oil coverage. When performing small-incision cataract surgery in patients who may require silicone oil injection, foldable hydrophilic acrylic or hydrophobic acrylic lenses should be preferred over standard foldable silicone lenses.

Acrylic Resins↗
PubMed1994

Subchronic 10 day immunotoxicity of polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice.

Millions of people have been exposed to silicones because of the widespread use in consumer products such as cosmetics and toiletries, food products, household products and paints. Silicones have wide use in medical practice, including lubricants in tubing and syringes, and as implantable devices. The most prevalent silicone in medical use is polydimethylsiloxane. This study was undertaken to determine the subchronic immunotoxicologic potential of the principal constituents of breast implants: silicone fluid, silicone gel and silicone elastomer. An alternative covering for devices containing silicone gels, polyurethane, was also included in the study. Silicone fluid and gel were injected subcutaneously into female B6C3F1 mice (1 ml/mouse) and 6 mm disks of silicone elastomer or polyurethane were implanted subcutaneously. There were no treatment-related deaths or overt signs of toxicity. None of the tested materials had notable effects on body or organ weights, erythrocytes or leukocytes in the blood, blood chemistries such as alanine aminotransferase, urea nitrogen, glucose, albumin or total protein. The cellularity of the bone marrow and responses to CSF-GM and CSF-M were normal. The tested silicones did not alter the distribution of B cells and T cells in the spleen, but polyurethane perturbed the distribution of CD4+CD8+ and CD4-CD8- T cells. The antibody response to sheep erythrocytes was not markedly altered, nor were proliferative responses to concanavalin A, phytohemagglutinin, lipopolysaccharide or allogeneic cells. Reticuloendothelial function was normal, but polyurethane evoked an enhanced phagocytosis of Covaspheres by adherent peritoneal cells. Natural killer cell activity and serum complement were not altered. All silicone materials afforded modest protection to a challenge with Listeria monocytogenes that killed 40 to 58% of control mice. Host resistance to Streptococcus pneumoniae or the B16F10 tumor was not affected by any of the treatments. There is a pattern indicative of some perturbation of T cell differentiation in mice implanted with a polyurethane disk.

Animals↗
PubMed1997

Adjuvancy effect of different types of silicone gel.

Women with silicone gel-filled breast implants (SBIs) are likely to be at a slightly higher risk of developing an autoimmune-like syndrome. This risk, although small, may be associated with the immunological adjuvancy property of the silicone gel. However, not all silicone gels are chemically formulated exactly the same and their adjuvancy behavior may vary. This study compared, in rats, the adjuvant effect of three different lots of silicone gel using ovalbumin (OVA) as the test antigen. Test bleeds were taken at 21, 48, 62, and 84 days post immunization and the rat sera were analyzed for anti-OVA antibodies by enzyme linked immunosorbent assay (ELISA). A delayed type hypersensitivity (DTH) test was performed on all the treated rats beginning at 14 post-immunization days. The results showed that silicone gel #3 (McGhan lot #S0400488) produced the highest mean anti-OVA antibody titer followed by silicone gel #1 (DC lot #HH019581) and silicone gel #2 (McGhan lot #DP9339). The DTH results showed that rats treated with silicone gel #1 and #3 had a clear positive response, whereas silicone gel #2 caused only a minimal response. These results demonstrate the immunological adjuvancy difference among three types of silicone gel. The chemical composition of each of these silicone gels, that would help explain these results, is yet to be determined.

Adjuvants, Immunologic↗
PubMed2001

Silicone rubber tubulization in peripheral sensory nerve reconstruction: an experimental study in rabbits.

Silicone rubber (polydimethyl siloxane) tubes are used clinically in peripheral nerve reconstruction. A disadvantage of this procedure is that the material often has to be removed owing to its mechanical properties. The aim of our study was to investigate the healing of reconstructed sensory nerves tubulized by silicone rubber in an animal model. In our experiments, we reconstructed the saphenous nerves in 27 rabbits. In series 1 (n = 12), silicone rubber tubes were slid over a nerve suture without a gap. In series 2 (n = 12), silicone rubber tubes were slid over a 10-mm nerve gap. In series 3 (n = 12), conventional suturing was performed in the collateral saphenous nerves of the animals of the series 1. Epineurial suturing was performed. Three other collateral nonoperated saphenous nerves served as controls. The healing was studied after 3, 6, and 12 months. Morphometric analysis of the regenerating axons was performed by using our new method for quantification of nerve fibers in cross sections stained by immunohistochemistry and using confocal laser scanning microscopy. Data analysis was carried out using a software program especially developed for this purpose. Our results showed in the silicone procedures that at 12 months significantly fewer axons per fascicle area were present compared with conventional suturing. However, mean axon diameters in the distal nerve stump of the silicone procedures did not differ significantly compared with the conventional suturing procedure. The ratio of total axon area to total fascicle area in the distal nerve stumps of the silicone procedure without gap was significantly smaller compared with the conventionally sutured nerve. The percentage outgrowing axons from the proximal nerve stump into the distal one in the silicone rubber procedure without gap was 57%. This was significantly higher than in the silicone rubber procedure with 10-mm gap (48%). However, in conventional suturing, the percentage of outgrowing axons (99%) was significantly higher than in both tubulization procedures. It appeared that tubulization by silicone rubber of sutured nerves without gap did not enhance axon regeneration. Conventional suturing gave significantly better results. If a gap was present, the use of a silicone rubber tube was preferable to non-suturing.

Animals↗
PubMedDate not supplied

Ultrasound biomicroscopy following the intraocular use of silicone oil.

We evaluated the ultrasound biomicroscopy findings and the amount and location of silicone oil residue in anterior structures of the eye before and after silicone oil removal. We examined the anterior structures in 40 silicone oil 1000 cs-filled eyes at the end of silicone oil tamponade time (mean silicone oil tamponade duration 5.1 months), and in the same eyes after silicone oil removal. High resolution ultrasound biomicroscopy, 50 MHz transducer, 50 microns of resolution, was used. Silicone oil droplets--often not ophthalmoscopically visible--appeared as highly reflective images with after ringing effect. They were present in the anterior structures of the eye in up to 95% of eyes with silicone oil in the vitreous cavity, and in up to 87.5% after careful silicone oil removal. With ultrasound biomicroscopy it was possible to identify small silicone oil droplets with a typical morphological appearance. Once silicone oil is used in vitreoretinal surgery, its complete removal from the anterior structures of the eye is very difficult to achieve later on.

Adolescent↗