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Biomedical subjects

L Mawn

Publications and source records attributed to L Mawn.

8 recordsLinked to original sources
PubMed2000

The Molteno M-Sphere.

PURPOSE: To analyze a mammalian hydroxyapatite (HA) implant known as the Molteno M-Sphere, recently approved by the Food and Drug Administration of the United States. METHODS: The authors examined the implant macroscopically, with chemical analysis (x-ray powder diffraction, x-ray fluorescence spectrophotometry), and microscopically with scanning electron microscopy. Animal implantation of six Molteno M-Spheres was carried out in six adult male New Zealand albino rabbits. Implant vascularization was evaluated by means of magnetic resonance imaging and histopathologic sectioning. RESULTS: The M-Sphere was found to have multiple interconnected pores throughout with an average pore size of 300 microm to 600 microm. This implant was very light-weight (0.31 g) and fragile. It was made up of pure HA. Magnetic resonance imaging studies showed implant enhancement to its center by 4 weeks after implantation. Histopathologically, fibrovascularization occurred uniformly throughout the 4, 8, and 12-week rabbit implants. CONCLUSIONS: The M-Sphere is an alternative type of HA implant that recently has been reintroduced into the United States for use after enucleation, evisceration, or as a secondary implant. It has multiple interconnected pores allowing central fibrovascularization as early as 4 weeks in a rabbit model. Its light weight and fine trabecular framework, however, are associated with increased implant fragility when compared with other available HA implants (BioEye and FCI3 synthetic HA). The implant requires careful handling because routine handling may damage the implant. The implant is currently approved by the United States Food and Drug Administration.

Animals↗
PubMed2000

Brazilian hydroxyapatite implant.

PURPOSE: To evaluate a synthetic hydroxyapatite (HA) (manufactured in Brazil) in a rabbit model. METHODS: Nine New Zealand white rabbits underwent enucleation of one eye followed by implantation of either a 12-mm Brazilian synthetic HA implant or a 12-mm BioEye, wrapped in polyglactin 910 mesh. Magnetic resonance imaging was performed to assess fibrovascular ingrowth 4, 8, and 12 weeks after implantation. Three animals were killed at each of the times for histopathologic examination. The Brazilian implant was also examined chemically and by scanning electron microscopy. RESULTS: The Brazilian HA was found to be heavier than either the BioEye or synthetic FCI3 HA implants. It did not have a visible, regularly arranged interconnected porous architecture. Rather, it had randomly appearing channels apparent on its external and internal surface in addition to large cystic areas within the body of the implant. Scanning electron microscopy revealed the implant to have a microporous architecture in addition to the large channels and cystic cavities. Histopathologically, central vascularization occurred by 4 weeks and was also present at 8 and 12 weeks. In three Brazilian implants an unrecognizable, nonbirefringent material was identified. The cause of it was unclear. Chemical analysis confirmed the implant to consist of pure HA. CONCLUSION: The Brazilian implant is pure HA that appears solid but has randomly arranged channels as well as a microporous architecture that allows vascularization to its center. It is heavier than other available HA implants and has the presence of an unidentified foreign material within it. Although this implant is less expensive and does not require a costly manufacturing process, the structural characteristics of the material do not offer any theoretical or clinical advantages. The implant is only available in Brazil at this time.

Animals↗
PubMed1999

Complications associated with pegging hydroxyapatite orbital implants.

OBJECTIVE: Prior studies of hydroxyapatite orbital implant complications have primarily focused on complications of the implant itself with only occasional mention of the complications associated with the peg system. This in part may be because of a low rate of pegging and, thus, a small sample size to evaluate. Therefore, a full range of complications that can occur with pegging has not been presented. The objective of this study was to determine the complications associated with pegging and to discuss ways to manage them. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS/INTERVENTION: The authors analyzed all of the complications associated with pegging 165 of a possible 275 hydroxyapatite implants implanted by 2 surgeons over 7 years. MAIN OUTCOME MEASURES: The following data were recorded: type of surgery performed, size of implant used, type of hydroxyapatite used, peg system used, time of pegging, follow-up duration, problems encountered, and treatment. RESULTS: Sixty-two (37.5%) of the 165 patients who had pegged implants were found to have problems with their pegs. Twenty-one (33.8%) of the 62 patients with peg problems had more than 1 peg-related problem. Complications associated with pegging included discharge (37%; 23 of 62), pyogenic granulomas (30.6%; 19 of 62), peg falling out (29%; 18 of 62), poor transfer of movement (11.2%; 7 of 62), clicking (11.2%; 7 of 62), conjunctiva overgrowing peg (4.8%; 3 of 62), poor-fitting sleeve (4.8%; 3 of 62), part of sleeve shaft visible (4.8%; 3 of 62), peg drilled on an angle (4.8%; 3 of 62), hydroxyapatite visible around peg hole (3.2%; 2 of 62), peg drilled off-center (3.2%; 2 of 62), popping peg (3.2%; 2 of 62), and excess movement of peg (3.2%; 2 of 62). The most serious complication occurring in two individuals (3.2%) was implant infection requiring implant removal. CONCLUSION: There are several potential complications that can occur after pegging the hydroxyapatite implant. These problems are generally of a minor nature but often require additional patient visits that would not ordinarily have been required if the peg was not in place. The most serious peg problem is implant infection, which may necessitate implant removal. These potential peg problems should be reviewed with the patient before the procedure is performed.

Adolescent↗
PubMed1998

Necrotizing fasciitis caused by group A streptococcus infection after laser blepharoplasty.

PURPOSE: To describe a patient who developed early signs of necrotizing fasciitis after undergoing laser blepharoplasty. METHODS: A 36-year-old woman developed wound discharge, wound dehiscence, and facial swelling 66 hours postblepharoplasty. Cloxacillin was administered but changed to high-dose intravenous penicillin G and clindamycin when the eyelid cultures grew group A streptococcus (an organism capable of causing necrotizing fasciitis organism). RESULTS: The patient was treated with intravenous antibiotics for 10 days followed by 3 weeks of oral medications. The wounds healed spontaneously with an excellent result. CONCLUSIONS: Infection postblepharoplasty is rare. When it occurs, tissue destruction can be potentially devastating. Prompt diagnosis, intravenous antibiotics, and close follow-up are essential.

Administration, Oral↗
PubMed1998

The synthetic hydroxyapatite implant: a report on 65 patients.

Sixty-five patients receiving the FCI synthetic hydroxyapatite implant (FCI3, FCI, Issy-Les-Moulineaux, France) after enucleation, evisceration, or as a secondary implant were studied under human trial guidelines established by Health and Welfare Canada. The implant is chemically identical to the original coralline Bio Eye (Integrated Orbital Implants Inc., San Diego, CA, U.S.A.), is easy to work with, and was implanted without difficulty using a wrap of polygalactin 910 (Vicryl mesh, Ethicon, Inc.) in the majority of patients. Postoperative drilling was carried out at approximately 6 months and found to be much easier than drilling of the Bio Eye. The implant could be hand drilled using drill bits rolled between the thumb and index finger. Postoperatively, patients were followed-up from 7 to 24 months and did not have any problems different from those associated with the original hydroxyapatite implant derived from sea coral (Bio Eye). One case of conjunctival dehiscence occurred at 4 weeks and required a temporalis fascia patch graft to repair. One implant became infected after drilling and had to be removed. The motility obtained with the third-generation FCI implant (FCI3) was similar to that seen with the Bio Eye, in comparable patients. That is, those receiving implants after an evisceration, on the whole, had better motility than those receiving an implant after primary enucleation or secondary implantation. The FCI3 hydroxyapatite implant is a viable alternative to the original Bio Eye hydroxyapatite implant. It's advantages are: 1) reduced cost, and 2) ease of drilling (a motorized drill is not required). The implant was given Health and Welfare approval in Canada on February 26, 1997.

Biocompatible Materials↗
PubMed1997

Juvenile pilocytic astrocytoma masquerading as amblyopia.

PURPOSE: A healthy 13-year-old girl, previously diagnosed with amblyopia in her right eye, was seen in consultation after her vision continued to decrease. METHODS: A complete ophthalmologic examination including visual field testing and optic nerve photography was performed in the neuro-ophthalmologic clinic. Magnetic resonance imaging study was also obtained. RESULTS: Visual sensory deficits and pale optic nerves were noted on clinical examination. Visual field testing showed a chiasmatic junctional defect. Magnetic resonance imaging verified a large chiasmatic mass, histologically proven to be a juvenile pilocytic astrocytoma. CONCLUSION: Early recognition of signs and symptoms of chiasmatic lesions is essential for preventing visual loss.

Adolescent↗
PubMed1994

Mean of the ten largest nucleoli, microcirculation architecture, and prognosis of ciliochoroidal melanomas.

BACKGROUND: Cytomorphometric measurements and the architecture of the microcirculation in tissue sections of eyes removed for ciliary body or choroidal melanomas have been identified independently as prognostically significant factors for survival. The relative significance of these two histologic features is addressed in this study. METHODS: The same 234 cases used to assess the prognostic significance of the microcirculatory patterns of choroidal and ciliary body melanomas were examined by two independent observers who measured the largest diameter of melanoma cell nucleoli from digitized images at a high magnification (x 3000) using the laser scanning confocal microscope. The mean of the ten largest nucleoli was calculated for each tumor according to previously published methods. Intraobserver and interobserver reproducibility was assessed for these measurements. Several Cox multiple regression models were constructed which included this cytomorphometric variable with and without the inclusion of the microcirculatory patterns. RESULTS: There is a high degree of intraobserver reproducibility but only a weak degree of interobserver reproducibility in measuring the mean of the ten largest nucleoli. Using multiple Cox regression models, the mean of the ten largest nucleoli from each observer failed to exert any effect on outcome after enucleation, regardless of whether the presence of networks of closed vascular loops was considered in the statistical formulation. The presence of networks of closed vascular loops was found to be the most statistically dominant histologic prognostic characteristic. CONCLUSION: The authors have not been able to confirm the use of the mean of the ten largest nucleoli as a significant prognostic factor in the outcome of patients whose eyes have been removed for ciliary body or choroidal melanomas. Further investigation of this cytomorphometric technique by other laboratories is warranted.

Adult↗