Permeability of subcutaneous tissues surrounding long-term implants to oxygen

Certain types of implanted medical devices depend on oxygen supplied from surrounding tissues for their function. However, there is a concern that the tissue associated with the foreign body response to implants may become impermeable to oxygen over the long term and render the implant nonfunctional. We report oxygen flux recordings from electrochemical oxygen sensor devices with wireless telemetry implanted in subcutaneous porcine tissues. The devices remained implanted for up to 13 weeks and were removed with adjacent tissues at specified times for histologic examination. There are four main observations: (1) In the first few weeks after implantation, the oxygen flux to the sensors, or current density, declined to a sustained mean value, having unsynchronized cyclic variations around the mean; (2) The oxygen mass transfer resistance of the sensor membrane was negligible compared to that of the tissue, allowing for a sensitive estimate of the tissue permeability; (3) The effective diffusion coefficient of oxygen in tissues was found to be approximately one order of magnitude lower than in water; and (4) Quantitative histologic analysis of the tissues showed a mild foreign body response to the PDMS sensor membrane material, with capillaries positioned close to the implant surface. Continuous recordings of oxygen flux indicate that the tissue permeability changes predictably with time, and suggest that oxygen delivery can be sustained over the long term.

Head lice. Dimeticone is the pediculicide of choice

Infestation of the scalp by head lice, or pediculosis, is a common, unpleasant but harmless parasitosis. For patients with pediculosis, which topical treatment eradicates the parasites effectively while causing the least harm? We reviewed the available evidence using the standard Prescrire methodology. Lice can be eradicated by shaving the head or combing the hair several times a day for several weeks with a fine-toothed lice comb, although combing is only completely effective in about 50% of cases. Pyrethroids (permethrin, phenothrin and bioallethrin), often combined with piperonyl butoxide, are insecticides that are neurotoxic to lice. The lice eradication rates achieved in trials of these agents are highly variable, ranging from 13% to 75% depending on the country, probably due to the development of resistance. In five randomised trials, the organophosphorus insecticide malathion was more effective than permethrin or phenothrin, achieving eradication rates of 80% to 98%. Topical application of the insecticides ivermectin or spinosad was effective in 75% to 85% of patients in randomised trials. Insecticides have mainly local adverse effects: pruritus and irritation of the scalp. Cases of malathion poisoning have been reported following topical application or ingestion. The long-term toxicity of insecticides is unclear; it therefore appears preferable to minimise their use. Agents that kill lice through physical mechanisms have few known adverse effects. It seems unlikely that lice will develop resistance to them. Dimeticone, a silicone compound, is not absorbed through the skin and provokes very few adverse effects. It is one of the better evaluated agents: in three randomised trials, 70% to 97% of patients were lice-free after two weeks. Other agents with a physical action on lice have been evaluated, each in one randomised trial including a few dozen patients. One of these, 1,2-octanediol, applied in an alcoholic solution, seemed to eradicate lice effectively with no notable adverse effects. It is advisable to avoid aerosol formulations due to the risk of bronchospasm, products containing terpenes as these compounds can cause seizures in infants and young children, and products that lack a child-proof cap. In practice, as of early 2014, pyrethroids are no longer the first-choice treatment for head lice: they are losing effectiveness and may be toxic in the long-term. Dimeticone is a better choice, because it has few known adverse effects and proven efficacy.

The optimal filler: immediate and long-term results with emulsified silicone (1,000 centistokes) with cross-linked hyaluronic acid

BACKGROUND

Silicone is one of the oldest and longest lasting of the dermal fillers. Microdroplet silicone injections have proven to be safe and effective. This paper describes how to obtain microdroplet silicone (1,000 centistokes) in a consistent manner, including a discussion of its efficacy and safety.

METHODS AND MATERIALS

A simple, permanent method of tissue augmentation is described. U.S. Food and Drug Administration- approved liquid silicone (Silikon®) is emulsified with cross-linked hyaluronic acid through a Luer-Lok to Luer-Lok connector between two 3-cc syringes. This stable emulsion is injected through a 27G needle or through a 25G or 27G microcannula into the middermis, subcutaneous tissue, or periosteum.

RESULTS

The results of 95 cases are described. The emulsion is most beneficial for distensible acne valleys, nasolabial folds, glabellar frown lines, augmentation of the vermilion border of the lips, and projection of the nose, cheekbones, and chin. Exterior nasal deviations and soft tissue defects are also improved. Complications are minimal and include temporary bruising, erythema, and mild edema. Any temporary small nodules are easily leveled with massage. Occasionally, it takes a repeat session at 1 month to completely elevate depressions. The resulting elevations remain stable during the 2-year follow-up period. No silicone granulomas have developed.

CONCLUSIONS

This methodology has replaced many indications for temporary, semipermanent, or permanent fillers.

Comparision of biocompatibility and cytotoxicity of two new root canal sealers

The aim of this study was to investigate the remote organ toxicity and connective tissue reaction of two new root canal sealers ("GuttaFlow(®)" and "EndoREZ(®)") and to compare them with zinc oxide eugenol sealer using biochemical and histopathological parameters. A total of 60 white albino Wistar rats were used in the study. 0.1ml of GuttaFlow(®), EndoREZ(®) or Kerr Pulp Canal Sealer(®) were administered subcutaneously into the mid-dorsal thoracic region of rats (15 in each group). Control rats were given saline only. Rats were decapitated after 24h, on day 7 and on day 30 of the experiment and tissue samples from lung, liver, kidney and skin were removed for the determination of malondialdehyde (MDA) and glutathione (GSH) levels. In parallel, tissues were also examined histologically. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels, and creatinine and blood urea nitrogen (BUN), concentrations (BUN) were measured to assess liver and kidney functions, respectively. Tumor necrosis factor (TNF) and lactate dehydrogenase (LDH) were also assayed in serum samples. No statistical differences were found among the control and EndoREZ(®), GuttaFlow(®) and Kerr Pulp Canal sealers regarding tissue MDA, GSH levels or serum parameters (p>0.05) at all time points examined. Both of the new root canal sealers showed good compatibility and acceptable tissue toxicity.

The effect of gamma irradiation on physical-mechanical properties and cytotoxicity of polyurethane-polydimethylsiloxane microfibrillar vascular grafts

Poly(ether) urethane (PEtU)-polydimethylsiloxane (PDMS) based materials have been processed by a spray, phase-inversion technique to produce microfibrillar small-diameter vascular grafts; however the effect of sterilization upon these grafts is still unknown. This study investigated the effect of gamma irradiation on grafts made of PEtU-PDMS materials containing different PDMS concentrations. Sterilisation-induced changes in surface chemical structure and morphology were assessed by infrared spectroscopy, light and scanning electron microscopy. Tensile tests were used to examine changes in mechanical properties and the cytotoxicity evaluation was performed on L929 fibroblasts. The study demonstrated that physical-chemical and mechanical properties of PEtU-PDMS grafts, at each PDMS concentration, were not significantly affected by the exposure to gamma irradiation, moreover no sign of cytotoxicity was observed after sterilisation. Although in vitro experiments have been promising, further in vivo studies are necessary to evaluate the biodegradation behaviour of PEtU-PDMS graft after gamma irradiation, before any clinical application.

[Description of complications after injection laryngoplasty with polydimethylsiloxane]

The injection of polydimethylsiloxane for medialization of the vocal folds has been used for more than 15 years with satisfactory long-term results. However there is little in the literature with regard to the complications and their treatment. We present 2 cases (1 unilateral laryngeal paralysis and 1 bilateral vocal fold atrophy) with unsatisfactory results after PDMS injection. The first case had chronic granulomatous inflammation induced by the PDMS and the second a periprothetic fibrotic reaction causing cordal rigidity. A superior cordotomy and extraction of the PDMS was performed in the two patients. A significant improvement was observed in the first patient (with granuloma); on the other hand the PDMS removal in the second case couldn't modify the cordal rigidity and consequently the voice quality. In conclusion, PDMS injection laryngoplasty is an efficient intervention with possible complications: foreign body granuloma, periprothetic fibrosis. In case of chronic inflammation, an endoscopic removal is indicated. Where there is vocal fold rigidity due to fibrosis the surgical correction is more difficult. For this reason an injection in Reinke's space or an over-correction must be avoided.

Randomised, controlled, assessor blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation

BACKGROUND

Malathion 0.5% has been the most prescribed pediculicide in the United Kingdom for around 10 years, and is widely used in Europe and North America. Anecdotal reports suggest malathion treatments are less effective than formerly, but this has not been confirmed clinically. This study was designed to determine whether malathion is still effective and if 4% dimeticone lotion is a more effective treatment for head louse infestation.

METHODOLOGY/PRINCIPAL FINDINGS

We designed this study as an assessor blinded, randomised, controlled, parallel group trial involving 58 children and 15 adults with active head louse infestation. Each participant received two applications 7 days apart of either 4% dimeticone lotion, applied for 8 hours or overnight, or 0.5% malathion liquid applied for 12 hours or overnight. All treatment and check-up visits were conducted in participants' homes. Cure of infestation was defined as no evidence of head lice after the second treatment. Some people were found free from lice but later reinfested. Worst case, intention to treat, analysis found dimeticone was significantly more effective than malathion, with 30/43 (69.8%) participants cured using dimeticone compared with 10/30 (33.3%) using malathion (p<0.01, difference 36.4%, 95% confidence interval 14.7% to 58.2%). Per protocol analysis showed cure rates of 30/39 (76.9%) and 10/29 (34.5%) respectively. Irritant reactions were observed in only two participants, both treated with malathion.

CONCLUSIONS/SIGNIFICANCE

We concluded that, although malathion liquid is still effective for some people, dimeticone lotion offers a significantly more effective alternative treatment for most people.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN47755726.

Preventing lateral synechia formation after endoscopic sinus surgery with a silastic sheet

OBJECTIVES

To investigate whether the insertion of a Silastic sheet between the middle turbinate and lateral nasal wall can prevent lateral synechia formation when an unstable, floppy middle turbinate results from endoscopic sinus surgery (ESS).

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

Thirty patients who developed an unstable, floppy middle turbinate during ESS were allocated in order of occurrence as follows: group 1, 15 patients, 17 sides including 2 bilateral cases; group 2, 15 patients, 18 sides including 3 bilateral cases.

INTERVENTIONS

In group 1, a fan-shaped Silastic sheet was inserted between the middle turbinate and lateral nasal wall and secured to the caudal septum. In group 2, no specific procedure was performed except for meticulous postoperative care to prevent lateralization of the middle turbinate.

MAIN OUTCOME MEASURE

We observed the patients for 5 months and compared the occurrence rate of synechia formation between the 2 groups.

RESULTS

Synechiae developed in 1 of 17 sides (6%) in group 1 and 8 of 18 sides (44%) in group 2, for success rates of 94% and 56%, respectively. The success rates differed significantly. The middle turbinate was preserved in all patients in group 1.

CONCLUSION

The results of this study suggest that the insertion of a Silastic sheet in the middle meatus is a useful method for preventing lateral synechia formation and for preserving the middle turbinate.

Chronic orbital infection caused by migration of an orbital Silastic implant

A Silastic sheet was used for the repair of a lateral orbital wall defect in a 48-year-old man. Migration of this implant through the defect has caused recurrent episodes of orbital infection. Although migration of Silastic within the orbit has been reported previously, the absence of fixation together with further remodelling of the lateral orbital wall defect contributed to this phenomenon.

Patient-perceived outcomes in the treatment of stress urinary incontinence: focus on urethral injection therapy

Intervention for stress urinary incontinence (SUI) is generally focused on minimizing urinary leakage. However, the overall impact of SUI therapy on patients' quality of life is, arguably, more important than leakage outcomes. We performed a literature search to investigate the effect of urethral injection therapy on quality of life. Significant quality-of-life improvements have been observed with a number of injectable agents, while there is a distinct lack of correlation between subjective and objective outcomes. Two studies comparing urethral injection therapy with surgical intervention found superior objective efficacy with surgery, but no significant differences in quality-of-life improvements. Personal goals of patients undergoing urethral injection are yet to be explored, but there may be willingness to trade a lower success rate in favor of a more minor treatment procedure. In conclusion, quality-of-life improvements after urethral injection appear significant and comparable to those obtained with surgery. Further study of patients' own perceptions, pre- and posttreatment, would be valuable.

A silastic sheet found during endoscopic transnasal dacryocystorhinostomy for acute dacryocystitis

Purpose

To report the case of a silastic sheet that was found during an endoscopic transnasal dacryocystorhinostomy for treatment of acute dacryocystitis with necrosis of the lacrimal sac.

Methods

A thirty-two year old male presented with painful swelling on the nasal side of his left lower lid two weeks prior to visiting this clinic. Fourteen years ago, the patient was involved in a traffic accident and underwent surgery to reconstruct the ethmoidal sinus. Lacrimal sac massage showed a regurgitation of a purulent discharge from the left lower punctum. Therefore, the patient was diagnosed with acute dacryocystitis and an endoscopic transnasal dacryocystostomy was performed the next day.

Results

The surgical finding showed severe necrosis around the lacrimal sac and a 20 × 15-mm sized silastic sheet was found crumpled within the purulent discharge. The sheet was removed, the lacrimal sac was irrigated with an antibiotic solution, and a silicone tube was intubated into the lacrimal pathway. After surgery, the painful swelling on the nasal side of left lower lid resolved gradually, and there were no symptomatic complications three months later.

Conclusions

We report the first case where a silastic sheet applied during a facial reconstruction had migrated adjacent to the lacrimal sac resulting in severe inflammation.

Liquid injectable silicone for soft tissue augmentation

Liquid injectable silicone is a unique soft tissue augmenting agent that may be effectively utilized for the correction of specific cutaneous and subcutaneous atrophies. Although historical complications have occurred, resulting likely from the presence of adulterants and impurities, modern purified silicone products approved by the Food and Drug Administration for injection into the human body may be employed with minimal complications when strict protocol is followed. In this article the present authors review the history and controversy regarding silicone as well as describe the appropriate indications, patient selection, instrumentation, treatment protocol, and anticipated complications involved with the use of liquid injectable silicone for soft tissue augmentation. Although its use is controversial, the present authors maintain that liquid injectable silicone is an important and effective augmenting agent for the long-term correction of scars and facial contour defects such as HIV facial lipoatrophy. Furthermore, it is a treatment modality deserving of continued investigation.

Inflammatory nasal polyps: an unusual late complication of Silastic sheet repair of orbital floor fracture

Silastic implants are very widely used in surgical practice and are considered to be relatively inert. They do however present with complications, including infection, local foreign body inflammatory response, calcification, migration and failure of repair of the defect, which sometimes may necessitate explantation. Head and neck implants do present a special case, as complications can cause obstruction and disruption of function in small cavities. A pertinent history, clinical review and computed tomography scan are usually invaluable in obtaining a diagnosis. We present a rare case of migrated Silastic orbital sheet, presenting as a nasal polyp and causing maxillary antral pain and infection. A detailed search of the medical literature revealed no other such case.

Misplaced Macroplastique injection presenting as a vaginal nodule and a bladder mass

We describe a very unusual presentation of misplaced Macroplastique injection. This incidentally showed up as bladder lesion and vaginal nodule during a tension-free vaginal tape surgery.

Long-term outcomes after total alloplastic temporomandibular joint reconstruction following exposure to failed materials

PURPOSE

Total alloplastic temporomandibular joint (TMJ) reconstruction is often necessary because of the significant bony destruction resulting from failed Proplast-Teflon (Vitek, Houston, TX) and/or Silastic (Dow Corning, Arlington, TX) foreign body inflammatory reactions. Multiply operated and functionless, TMJ patients likewise have undergone total alloplastic reconstruction. Many of these patients were also exposed to failed TMJ implant materials. It was the purpose of this study to evaluate a population representative of both these groups of patients reconstructed with the Techmedica (now, TMJ Concepts, Ventura, CA) Total TMJ System to determine whether the long-term subjective and objective outcomes were affected by either the presence of the previously failed TMJ implant materials, the number of prior procedures, or both.

PATIENTS AND METHODS

One hundred ninety-eight patients who had been implanted with 332 Techmedica System total joints between 1990 and 1994 where divided into 4 groups based on their prior exposure to failed TMJ implant materials: group I, Proplast-Teflon (82 patients, 135 joints); group II, Silastic (28 patients, 46 joints); group III, both Proplast-Teflon and Silastic (25 patients, 46 joints); and group IV, no prior exposure to Proplast-Teflon or Silastic (63 patients, 105 joints). The mean follow-up was 60.2 +/- 40.3 months (range, 2 to 120 months). To determine whether exposure to either or both failed implant materials affected the long-term subjective and objective outcome variables, the groups were compared statistically using multivariate mixed modeling with age, sex, number of prior operations, years with TMJ problem, prior implant type, and implant sides as independent variables, and the relevant baseline measure as covariates.

RESULTS

For the subjective variables, patients exposed to Proplast-Teflon or Silastic had significantly higher mean pain scores long-term. The type of prior failed TMJ implant material was not statistically significant with regard to function. Patients exposed to Proplast-Teflon reported poorer diet consistency scores long-term. Objectively, patients with 5 or fewer prior TMJ surgeries exposed to neither failed implant or Silastic reported better long-term mean maximum interincisal opening than did those patients exposed to Proplast-Teflon or both failed materials. However, for patients with 6 or more prior TMJ surgeries, those exposed to Proplast-Teflon or both failed materials reported less decrease in mean maximum interincisal opening over time.

CONCLUSION

These data confirm what has been observed clinically, that in the population studied, multiply operated patients previously exposed to failed Proplast-Teflon alone or both failed Proplast-Teflon and Silastic have poorer reported long-term outcomes with alloplastic reconstruction. However, the total alloplastic TMJ reconstruction devices used in this study remained functional.

The treatment of male stress urinary incontinence with polydimethylsiloxane in compliant bladders following spinal cord injury

STUDY DESIGN

Retrospective analysis.

OBJECTIVES

To evaluate the safety and efficacy of polydimethylsiloxane (PDS, Macroplastique) submucosal injections, in the treatment of male genuine stress urinary incontinence secondary to spinal cord injury (SCI).

SETTING

London Spinal Injuries Unit, Stanmore, UK and Institute of Urology and Nephrology, London, UK.

PATIENTS AND METHODS

A retrospective analysis identified 14 patients treated with PDS for stress urinary incontinence secondary to SCI between 1997 and 2001. A single surgeon at a specialist spinal injuries unit managed all patients. A total of 13 patients had suffered a traumatic SCI (T11:n=2; T12:n=5; L1:n=5; L2:n=1), while one developed stress incontinence after spinal surgery. The mean age was 41 years (range 26-69 years) and the mean duration of injury was 9.6 years (range 1.5-48 years). The preoperative investigations included video cystometrogram (VCMG) confirming the presence of urodynamically proven stress incontinence without evidence of urge incontinence. Complete cure was defined as a cessation of pad usage with no evidence of leakage on VCMG. Incomplete cure with improvement was defined as a >50% reduction in the number of pads used, with incontinence present on VCMG.

RESULTS

The follow-up ranged from 12 to 58 months (mean 34.7 months). Five patients (36%) reported complete success, confirmed by VCMG. Three patients (21%) reported improvement with >50% reduction in the use of pads. The procedure failed completely in six patients (43%). No immediate or late complications were noted with the procedure.

CONCLUSIONS

The use of PDS is a safe and minimally invasive treatment for genuine stress urinary incontinence in males following SCI with a stable compliant bladder. We achieved complete cure in 36% of our patients with confirmation on VCMG. A further 21% reported greater than 50% reduction in usage of pads; however, on VCMG stress incontinence was demonstrated in these patients. We suggest that PDS can be used as the first line of treatment in this difficult group of patients with complex problems.

Compromised production of extracellular matrix in mice lacking secreted protein, acidic and rich in cysteine (SPARC) leads to a reduced foreign body reaction to implanted biomaterials

SPARC (secreted protein, acidic and rich in cysteine), a matricellular glycoprotein, modulates the interaction of cells with the extracellular matrix (ECM). Recently, accelerated cutaneous wound closure and altered deposition of collagen were reported in SPARC-null mice. Herein we asked whether SPARC might influence the foreign body reaction to biomaterial implants. Polydimethylsiloxane (silicone rubber) disks and cellulose Millipore filters were implanted into wild-type and SPARC-null mice. In wild-type animals, significant levels of SPARC were observed in the cells and the ECM comprising the capsules around the implants. After 4 weeks, SPARC-null mice exhibited a significant decrease in the thickness of the foreign body capsule, as compared to that observed in wild-type mice. A significant reduction in capsular vascular density was also associated with the silicone implants in the SPARC-null animals. Electron microscopy revealed that collagen fibers in the capsules produced by SPARC-null mice were smaller and more uniform in size than those in wild-type animals. Furthermore, staining with picrosirius-red showed that the collagen fibers were less mature in SPARC-null than in wild-type mice. The altered ECM resulting in decreased capsular thickness, indicative of an altered foreign body reaction in SPARC-null mice, implicates SPARC as an important modulator of the encapsulation of implanted biomaterials.

Subureteral polydimethylsiloxane injection versus extravesical reimplantation for primary low grade vesicoureteral reflux in children: a comparative study

PURPOSE

We compare the outcome of extravesical ureteral reimplantation to endoscopic polydimethylsiloxane (Macroplastique, Uroplasty, Inc., Minneapolis, Minnesota) subureteral injection for primary low grade vesicoureteral reflux in children.

MATERIALS AND METHODS

Between 1997 and 2000, 180 patients underwent polydimethylsiloxane injection (74, 108 ureters) or extravesical ureteral reimplantation (106, 166 ureters) for low grade vesicoureteral reflux. Low grade reflux was defined as grades I to III. Outcome analysis included success rates, de novo hydronephrosis, voiding efficiency, urinary tract infections and complications.

RESULTS

Mean patient age at surgery for the injection and surgery groups was 60 and 77 months, and mean followup was 12 and 15 months, respectively. Of the patients who underwent single injection 80.6% were cured of reflux at 3 months and 91.6% were cured at last followup. Success rate after reimplantation was 95.8% at 3 months which improved to 98.8% 1 year later. The success rate was significantly different between the injection and reimplantation groups at 3 and 12 months (p <0.01). Postoperative complications in the reimplantation group included transient urinary retention after bilateral surgery in 2 patients (3.3%), suprapubic fluid collections in 2 and wound seroma in 1. No complications occurred in the polydimethylsiloxane group.

CONCLUSIONS

Extravesical ureteral reimplantation has near perfect success with a low but definite complication rate. Polydimethylsiloxane offers high success rates for reflux in an ambulatory setting with no short-term complications. Currently, endoscopic polydimethylsiloxane injection is our preferred mode of therapy for low grade vesicoureteral reflux in children when surgical correction is indicated.

Long-term study of temporomandibular joint surgery with alloplastic implants compared with nonimplant surgery and nonsurgical rehabilitation for painful temporomandibular joint disc displacement

PURPOSE

The purpose of this study was to determine the long-term objective and subjective outcomes of temporomandibular joint (TMJ) implant surgery for the treatment of painful TMJ disc displacement using temporary Silastic (Dow Corning Corporation, Midland, MI), permanent Silastic, or Proplast (Vitek, Houston, TX) implants to replace the disc. These cases were compared with other cases of the same diagnosis treated with either nonsurgical rehabilitation or nonimplant surgery involving discectomy or disc repair procedures.

MATERIALS AND METHODS

A cross-sectional study was conducted among 466 patients who received treatment for unilateral or bilateral TMJ disc displacement before January 1, 1990. The 5 treatment groups noted above were compared for long-term outcomes. Objective outcome measurements for jaw function were performed using a calibrated examiner and the Craniomandibular Index (CMI). Subjective (self-reported) outcomes were obtained relative to jaw function (Mandibular Function Impairment Questionnaire [MFIQ]), symptom severity (Symptom Severity Index [SSI]), and the impact of pain (Global Pain Impact [GPI] scale).

RESULTS

The results, adjusted for gender, baseline tomogram score, and baseline symptom scores, showed that the nonsurgical rehabilitation group (n = 159) and the group having TMJ surgery without implants (n = 149) had statistically better results than the group who underwent surgery with a Proplast implant (n = 94). These between-group differences included both objective signs (CMI), and subjective reports of jaw function (MFIQ), symptom severity (SSI), and global pain impact (GPI). The MFIQ score associated with the nonsurgical rehabilitation group was also statistically better than for the Silastic implant groups, including both the temporary (n = 31) and permanent (n = 33) implants. Clinical differences between groups were slight.

CONCLUSION

This study suggests that the use of interpositional disc implants in TMJ surgery is not associated with improved outcomes when compared with nonimplant surgery or nonsurgical rehabilitation.

Toxicology of polymers for implant contraceptives for women

This article reviews the toxicology of polymers that are used in contraceptive implants. The two main classes of synthetic, nondegradable polymers used in the delivery of female contraceptives are silicone elastomers (e.g., Silastic) and ethylene co-vinyl acetate (EVA; ELVAX). The controversies surrounding the silicone breast implants have prompted several studies to evaluate the toxicity of silicones. The epidemiologic data obtained thus far have overwhelmingly concluded that no correlation exists between certain chronic symptoms, such as arthritis, in patients and silicone prosthesis. This conclusion has been echoed by the expert panel report by the Institutes of Medicine. Although the IOM report focused on the safety of silicone breast prosthesis, data emerging from the joint reconstruction area also suggests that Silastic is safe for in vivo use. The toxicological studies on EVA are few, and the conclusion thus far is that they elicit no adverse local or systemic response over extended periods in vivo. In conclusion, the prognosis for Silastic and ELVAX as of now is excellent. However, any future implant development using these polymers should place an emphasis on processing parameters to minimize potential small molecule leachants and establish safety as a function of both site and duration of implantation.

Surgical treatment of TMJ ankylosis: our experience (60 cases)

Limitation of mouth opening can be caused by bony or fibrous ankylosis of the temporomandibular joint as sequela to trauma, infection, autoimmune disease, or failed surgery. Various procedures have been reported for treatment of temporomandibular joint (TMJ) ankylosis; this article aims to describe the diagnostic protocol and the surgical procedures adopted at the department of Maxillo-Facial Surgery of Rome University "La Sapienza". Between 1980 and 2000, 123 patients affected by TMJ ankylosis came under our observation; 60 of them (25 females and 35 males of 30 years average age) underwent surgery; bilateral TMJ ankylosis was observed in 21 cases, right-sided in 20 cases, left-sided in 19 cases. In 12 cases coronoid processes were involved. Etiopathogenesis was traumatic in 48 cases, septic in 5 cases, auto-immune (RA and seronegative spondyloarthropathies) in 5 cases; after block removing, arthroplasty was performed with pedunculated flap of temporal muscle (10 cases), Silastic material (11 cases), or lyophilized dura mater (2 cases). Simple condylar shaving was used in the remaining 36 cases. All patients under treatment showed a distinctive improvement both in articular functionality and symptoms; secondary surgery was necessary in seven cases due to the onset of articular complications from previous surgery. Silastic removal was necessary in five cases due to its inducement of foreign body granuloma. Follow-up was performed at 12, 24, and 48 months and 5 years postoperatively. In our opinion the gold standard surgery of TMJ ankylosis today is represented by shaving of articular surfaces and subsequent arthroplasty with or without temporal muscle myofascial flap interposition, whereas the use of Silastic as alloplastic material could be associated to an increased persistence of the local symptoms and a higher risk of foreign body granuloma and it may favor ankylosis relapse and hinder rehabilitation.

Polymeric transdermal drug penetration enhancer. The enhancing effect of oligodimethylsiloxane containing a glucopyranosyl end group

Oligodimethylsiloxanes (ODMSs) containing a beta-D-glucopyranosyl group at one chain end (Glc-ODMSs) with various molecular weights were prepared to develop a silicone-based polymeric transdermal penetration enhancer with a non-ionic polar end group. Glc-ODMSs were prepared by hydrosilylation of hydrosilyl-terminated ODMS with 1-allyl-beta-D-glucose tetraacetate in the presence of bis(benzonitrile)platinum dichloride as the catalyst, followed by hydrolysis of the acetyl groups with sodium methoxide. The enhancing effect in the drug penetration was evaluated by in vitro experiments using a two-chamber diffusion cell. Antipyrine was used as a model drug, and the amount of drug permeating through the rat abdominal skin with or without Glc-ODMS was determined by HPLC. These enhancers were effective for the penetration of antipyrine. On the other hand, the enhancing effects were influenced by the concentration of Glc-ODMS coexisted regardless of its ODMS chain length. The enhancing effect was also observed by the pretreatment of the skin with Glc-ODMS before the drug permeation, the results of which suggested that the induction periods to appear the enhancing effects were different between Glc-ODMSs with the short and the long ODMS chain lengths. Furthermore, according to the Draize test, Glc-ODMSs exhibited no irritation to the skin regardless of the ODMS chain length.

Prospective comparative evaluation of stapled versus transected silastic ring gastric bypass: 6-year follow-up

BACKGROUND

The effect of transecting vs. stapling the stomach in continuity in the banded gastric bypass (GBP) operation was studied.

METHOD

50 patients, 25 in each group, were enrolled into a prospective study to determine if transecting the stomach vs. stapling it in continuity in performing GBP for obesity decreases the incidence of gastro-gastric fistula formation without increased morbidity.

RESULTS

The patient profiles in the 2 groups were very similar. The peri-operative complications included 1 splenic capsular injury in each group, controlled without a splenectomy. There was 1 anastomotic leak in the stapled and 1 bleeding from the cut edge of the bypassed stomach in the transected group, both requiring re-operations in the immediate postoperative period. There was no peri-operative mortality. The percent follow-up after 6 years was 80% and 88% in the stapled and transected groups respectively. The incidence of late complications of solid food intolerance, ventral incisional hernia, cholelithiasis and small bowel obstruction was similar in both groups. There were 8 gastro-gastric fistulas in the stapled group and 1 in the transected group. The reduction in body mass index and percent excess weight loss (66%) were similar in both groups.

CONCLUSION

The incidence of gastro-gastric fistula may be reduced in GBP procedures by transecting the stomach as opposed to stapling it in continuity, without an increase in morbidity or mortality or any loss in the effectiveness of the operation.

Textured polydimethylsiloxane elastomers in the human larynx: safety and efficiency of use

For the treatment of unilateral laryngeal paralysis with glottic insufficiency injection laryngoplasty is a popular modality of treatment. This procedure augments the volume of the paralyzed vocal fold by endoscopic injection. However, the ideal substance has not yet been found for that purpose. We report for the first time the systematic application and long-term results of vulcanized polydimethylsiloxane (PDMS) particles in the treatment of glottic insufficiency in the human larynx. Of 10 patients treated with PDMS in the early 1990s, 7 patients could be retrieved for reevaluation. Laryngeal function was assessed by videostroboscopy, expert rating, and further characterized by the objective parameters of voice profile and maximum phonation time. In a standardized questionnaire, all patients were asked for their personal impression of the results. Mean follow-up time was 88.4 months (range 69-102 months). Glottic closure was complete in 5 of 7 patients. There were no signs of granuloma formation or other pathologic changes of the injected vocal folds. In 4 cases, voices were rated normal or near-normal; 2 voices were rated as fair; 1 usable. All the patients reported significant and lasting voice improvement. None of the patients reported any problems related to PDMS. PDMS particles provide permanent augmentation of human vocal fold volume without complications. Their use is a valuable and safe alternative when a definitive one-step procedure seems advantageous. However, further studies are needed to assess voice improvement in comparison to other materials.

Silicone granuloma on the entry points of acupuncture, venepuncture and surgical needles

We describe a case of epithelioid granuloma on the entry points of needles used for acupuncture, venepuncture and for taking skin biopsy. The acupuncture needles used at each session were silicone coated. Silicon was detected in the vacuoles of macrophages and multiple nucleated giant cells by X-ray microanalysis. To our knowledge, this is the first case of silicone granuloma arising on the entry points of acupuncture, venepuncture and surgical needles.

Foreign-body reaction to silastic burr-hole covers with seroma formation: case report and review of the literature

Because silastic material is one of the most commonly used biomaterials in modern medicine, the biocompatibility of these implants is still a source of long standing controversy. Though several studies have established silastic material as biologically inert, numerous authors have repeatedly described characteristic pathological tissue responses to silicone and its elastomeres. We report a case of foreign-body reaction to silastic burr-hole cover with successive formation of a seroma following resection of an olfactory groove meningioma. Within 30 days postoperatively, the patient developed a marked bulge in the glabbelar region. Histopathological examination revealed a seroma-like lesion obviously caused by a chronic inflammatory allergic reaction to the silastic burr-hole cover. Although the silicone-induced tissue damage clinically shows a wide variability and a conclusive model of pathogenesis is presently not available, the histopathological findings in some patients, in the form of granulomatous lesions and inflammatory cell response, might partly be due to an immunological reaction. Such a reaction has been previously described both clinically and experimentally, as detected in our patient. In addition, a review of the literature is given.

PDMS-based polyurethanes with MPEG grafts: synthesis, characterization and platelet adhesion study

Polyurethane (PU), based on poly(dimethyl siloxane) (PDMS) as a soft segment, with monomethoxy poly(ethylene glycol) (MPEG) grafted onto it, was synthesized as a new polymeric biomaterial for coating PDMS-based biomedical devices. Two different chain extenders, ethylene glycol (EG) and diethyl bis(hydroxymethyl) malonate (DBM), were used for the synthesis of PDMS-based PUs and then MPEG was grafted onto them by allophanate and esterification reactions, respectively. Their molecular structures were confirmed qualitatively and quantitatively using FT-IR and 1H-NMR measurements. PDMS-based PU was more hydrophobic than Pellethane, which is a commercial biomedical-grade poly(ether urethane), due to the PDMS-rich phase at the polymeric surface. However, the incorporation of MPEG in PDMS-based PU induced an increase in hydrophilicity. Analyses of their morphology using dynamic mechanical analysis and differential scanning calorimetry showed that the degree of phase separation increased with the content of hard segments. It also showed that MPEG is compatible with a hard segment consisting of 4,4'-diphenylmethane diisocyanate (MDI) and DBM, while being incompatible with one consisting of MDI and EG. Platelet adhesions with PDMS-based PUs were significantly reduced when compared with Pellethane. It was also observed from a platelet adhesion experiment that the incorportion of MPEG further reduced platelet adhesion. PDMS-based PUs with MPEG grafts, which have few hard segments and a distinct PEG phase, exhibited the least platelet adhesion among the polymer samples tested.

Lens refilling with injectable silicone in rabbit eyes

PURPOSE

To evaluate the technique of refilling the lens capsule with injectable silicone and assess the postoperative findings.

SETTING

Jinshikai Medical Foundation, Nishi Eye Hospital, Osaka, Japan.

METHODS

The lens capsules in the eyes of 16 rabbits weighing 1.5 to 2.0 kg were refilled with 0.2 mL of silicone polymer (about 66% bag volume) after endocapsular phacoemulsification through an upper minicircular capsulorhexis 1.5 to 1.8 mm in diameter. The capsule opening was sealed with a silicone plug to prevent leakage of the injected silicone. Main outcome measures were surgical success rate, inflammation, endothelial cell loss, refractive change after pilocarpine 4% instillation, and capsule opacification.

RESULTS

The lens capsule could be refilled in 10 eyes. The failures were caused by capsule rupture during phacoemulsification (n = 3) and profuse leakage of the injected silicone. Silicone that leaked minimally during surgery was easily washed away. Silicone that leaked and polymerized in the anterior chamber postoperatively (n = 3) was easily removed by surgery the following day. Mean endothelial cell loss was 10.2% 1 month after surgery. Aqueous flare intensity was significantly lower on days 2 and 4 than after conventional intraocular lens implantation in a control group. The respective mean preoperative and postoperative refractions were 0.7 diopters (D) +/- 1.0 (SD) and 19.1 +/- 1.0 D and the mean change (difference between the refractions before and after topical application of pilocarpine 4%), -0.4 +/- 0.6 and 1.1 +/- 0.4 D (P < .01). Posterior capsule opacification (PCO) was noted after 3 weeks in all eyes.

CONCLUSIONS

Lens capsule refilling and capsular plug use to prevent silicone leakage was shown to be feasible and avoided complications caused by leakage. Refractive changes suggest that the procedure could yield accommodation in primates> Although neodymium: YAG laser capsulotomy did not cause herniation of the injected silicone, PCO prevention is an essential issue in lens refilling because the capsulotomy may annul the attained accommodation.

MR imaging of the augmented breast

Mammographic evaluation of the augmented breast is challenging, since breast implants obscure significant amount of breast tissue while diminishing the effect of compression. Posttherapeutic scarring can make mammographic interpretation even more difficult. MRI has thus evolved into the modality of choice for diagnosing implant complications as well as detection of primary or recurrent breast cancer in these patient population. The present article attempts to give an overview of the MR findings of different breast augmentation and reconstruction techniques, i. e. prosthetic breast implants, breast reconstruction with autogenous tissue, free silicone injections and fat grafts, and their complications.

[Patient information: advancements in jurisprudence. The example of silicone]

Medical procedures are performed in the context of a contract between the physician and the patient. Failure to comply with this contract may engage the physician's responsibility. For a long time, the physician's responsibility was engaged because of technical errors or, more rarely, lack of information or consent, which had to be proved by the patient. In the case of litigation, a recent decision by the Court of Appeal (25 February 1997) requires physicians to demonstrate that they have effectively and validly informed the patient. This article studies the content of this information. It suggests a method which, set up under the authority of scientific societies, would allow, in our discipline, the proposal of information forms designed to inform our patients and to preserve our responsibility. Finally, this approach is illustrated by the study of tolerability of materials containing silicone.

[Analysis of the failure of endoscopic treatment of vesico-renal reflux in children using injections of teflon and collagen and the preliminary results of injections of Macroplastic]

This study of 785 cases of vesicorenal reflux in 494 children treated endoscopically over a 7-year period was designed to evaluate the results obtained with three products used successively: Teflon, collagen and Macroplastic. Following Teflon injection, despite a 90% short-term success rate, recurrent reflux was subsequently observed in 16.71% of the ureters reviewed. The failure rate was 52.63% after collagen injection and 11.77% after Macroplastic. After one or two injections, complete resolution of reflux was obtained in 48% of children treated with collagen, versus 85.72% with Teflon and 93.33% with Macroplastic. In one half of cases, failure was related to the quality of the product and its modifications after injection. The marked resorption of collagen accounts for the poor results despite the large doses injected. Apart from one case of partial resorption of Teflon paste, the failures with this product were due to lateralisation or secondary elimination of the product from the injection site due to its fluidity. Macroplastic, due to its higher viscosity and absence of retraction, currently provides the best results with doses of less than 0.20 ml in children.

Antibody to silicone and native macromolecules in women with silicone breast implants

Silicone implants have been associated with the development of multiple organ system abnormalities, including rheumatic disorders, nervous system, pulmonary dysfunction associated with autoantibodies and abnormalities of cellular immunity. In this regards a number of case reports and series of articles have been described. We hypothesized that an immune reaction to silicone breast implants would include the host reactivity against silicone and the macromolecules within the microenvironment of the implant, and these autoantibodies may react with other tissue antigens far from the site of the implant. To test this hypothesis 520 Symptomatic women with Silicone Implants which have developed Silicone related Immunological disorders and have typically complained of breast pain, Myalgia-Arthralgia, fatigue, or generalized pain, were examined by their physician. Blood samples were obtained and examined for the presence of Silicone antibodies, Myelin Basic Protein and human serum albumin antibodies. These samples were then compared to 520 matched controls without implants. At least at the level of two standard deviation silicone specific antibodies, IgG, IgA IgM, IgE and IgG+IgA+IgM antibodies were detected above the mean of normal controls. When these antibodies were classified based on the specialty of the examining physician, the % of patients with Silicone Antibodies were varied; general practice 51.6, Rheumatology 58.7, and Plastic Surgery 83.3, which may relate to the severeness of the disease. Being that a large % of patients demonstrated very high levels of Myelin Basic Protein Antibodies, possible cross reactive antibodies were sought. However, absorption of highly positive sera for Silicone Antibodies with MBP did not change the levels of Silicone Antibodies. On the other hand, Silicone-HSA was able to reduce the antibody values significantly. This reduction in antibody levels by Silicone is the best indication for the specificity of these antibodies. Moreover when data for silicone antibodies and MBP antibodies was analyzed in patients some with high and others with medium or low levels of silicone antibodies, MBP antibodies did not correspond to the silicone antibody levels. Similarly human serum albumin antibodies which was significantly higher in patients with silicone implants did not correlate with levels of silicone antibodies. These results indicate that immune reaction to silicone and different tissue antigens do occur and they are initiated through different mechanisms. And since predominant antibody class against silicone, MBP and HSA was IgM, clonal activation of IgM is possible which certainly warrants further investigation.

Evaluation of polydimethylsiloxane as an alternative in the endoscopic treatment of vesicoureteral reflux

Endoscopic correction of vesicoureteral reflux is an attractive alternative to open repair. In terms of effectiveness and long-term successful results polytetrafluoroethylene (Polytef) is the most reliable injectable product. However, legitimate concerns regarding particle migration still exist for polytetrafluoroethylene. Polydimethylsiloxane (Macroplastique) was evaluated as an alternative to polytetrafluoroethylene. Seven mongrel female dogs underwent endoscopic suburothelial injections of 0.35 to 0.50 cc polydimethylsiloxane paste by the O'Donnell technique to a unilateral nonrefluxing ureteral orifice. To facilitate migratory surveillance the paste was mixed with 57carbon monoxide radiolabeled 80 microns. microspheres and injected in 5 of the 7 animals. Animals were sacrificed at 1, 3 and 6-month intervals. All major organs were retrieved and processed. After intensive histological evaluation the remaining tissue underwent dissolution and centrifugation in sodium hypochlorite. The resulting insoluble pellet was further analyzed. In dogs injected with radiolabeled paste tissue samples and insoluble pellets of each organ system were analyzed for gamma counts. Smears of the insoluble pellets of all animals were examined on light and phase contrast microscopy. At autopsy no gross abnormalities were noted. Tissue reaction at injection sites revealed a well encapsulated foreign body reaction with predominantly giant cells, fibroblasts and collagen deposition. Limited local migration of polydimethylsiloxane particles into the periureteral lymphatics of 1 animal sacrificed at 1 month was noted and a single particle visually indistinguishable from polydimethylsiloxane also was found within the splenic capsule. The endoscopic procedure in this animal was complicated in that 2 separate injections were required and histological evaluation confirmed that the injections were performed uniquely deep into the bladder muscularis. Radioactive counts and dissolution of all major organ systems demonstrated no migration in the remaining 6 animals. Endoscopic subureteral injection of polydimethylsiloxane is technically feasible, and it may prove to be biocompatible and without risk of distant migration if injected correctly.

Magnetic resonance study of virgin and explanted silicone breast prostheses. Can proton relaxation times be used to monitor their biostability?

The development of sensitive and non invasive magnetic resonance (MR) techniques for monitoring the fate of silicones in breast prostheses in vivo requires detailed knowledge of the MR properties of these silicones. To characterize changes in the proton dynamics, relaxation time measurements (T1 and T2) were obtained on virgin and explanted breast prostheses using both spectroscopic and imaging techniques in a magnetic field of 1.5 Tesla. Averaged transverse relaxation times (T2) were observed to depend neither on the measurement technique employed (virgin silicone, T2 = 160 +/- 5 msec with imaging and 154 +/- 9 msec spectroscopically) nor on the effect of being implanted in the body for various periods of time ranging from 4 months to 17 years (explanted silicone, T2 = 164 +/- 16 msec with imaging and 159 +/- 25 msec spectroscopically). Average longitudinal relaxation times (T1) were also found to be similar for virgin and explanted prostheses (virgin silicone T1 = 899 +/- 32 msec, explanted silicone T1 = 879 +/- 75 msec, measured with imaging), but appeared to depend on the measurement technique employed (virgin silicone T1 = 764 +/- 17 msec, explanted silicone T1 = 765 +/- 23 msec, measured spectroscopically). Although the measured relaxation times did not reveal any differences between virgin and explanted prostheses, marginal differences were detected between the relaxation times of explanted prostheses from different manufacturers. More reference data on standard silicone products may be required before changes in implanted silicone can be assessed using proton magnetic relaxation times.

Human immune response to polydimethylsiloxane (silicone): screening studies in a breast implant population

Although initially it was thought that polydimethylsiloxane (silicone) was biologically inert, recent published studies have demonstrated varying levels of IgG antibody reactive with this structure in humans. The objective of our study was to determine whether silicone implanted in humans results in a measurable immune response directed against a 3700 mol wt hydroxyl terminated silicone molecule and whether that response could be correlated with the level of presumed silicone exposure as inferred by clinical history. In a blind study, sera from 111 patients, with and without breast implants, were sent to a laboratory using an enzyme-linked immunosorbent assay to determine specific anti-silicone IgG antibody levels. Test results showed that patients with implants demonstrated statistically significant elevation in anti-silicone antibodies compared with the unimplanted control groups. The highest anti-silicone antibody levels were measured in implanted women with either frank implant ruptures or leakage of their silicone gel implants.

Injected silicone: radiologic appearance

The authors describe the radiologic appearance of fluid silicone in the soft tissues of the gluteal area in a transsexual man. Thickening and striation of the soft tissues was observed in the trochanteric area in plain films. Serpiginous hyper-attenuated bands infiltrating the subcutaneous fat were seen with computed tomography. The patient was asymptomatic in the gluteal area.

Silicone fluid-induced pulmonary embolism

Silicone fluid injection for mammary augmentation is a well-known illegal procedure. It has been associated with many complications, including local tissue granulomatous reaction, chronic infection, and sclerosis, but pulmonary involvement in human beings has been documented in only six cases. We describe three more such cases of pulmonary embolism. These three patients were all female, young, and previously healthy. They received the procedures only for cosmetic reasons. Unfortunately, one of them died and another lived with the sequelae of pulmonary fibrosis. The mortality rate of the nine total patients with pulmonary embolism induced by silicone fluid, including our three cases, is 33%. Because of this high mortality rate and long-term sequelae of pulmonary fibrosis, no silicone fluid injection should be given for cosmetic reasons, especially in mammary augmentation in which a large volume of silicone fluid is more likely to be used, and the early use of corticosteroid therapy may be helpful.