Animal experimental implantation of an atrial septal defect occluder system.
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OBJECTIVE: To establish the implantation technique for the atrial septal defect occluder system (ASDOS) device in an experimental animal model and to determine long term mechanical stability of the device and its in vivo properties in terms of biocompatibility and tissue reaction. MATERIALS AND METHODS: An atrial septal defect was created and the device implanted in 17 pigs (mean weight 30 kg). The implantation technique was refined and modified because of initial technical and anatomical complications during nine acute pilot studies. The technique proved to be feasible in eight subsequent survival studies. Four pigs were electively killed three months after implantation (group 1). The remaining four pigs were killed six months after implantation (group 2). RESULTS: Necropsy showed all devices were embedded in soft tissue three months after implantation. Microscopic examination of atrial septal tissue showed an acute granulomatous inflammatory reaction in group 1 and fibrosis in group 2. The intensity of the inflammatory reaction around the device was clearly milder in group 2, indicating a decline in the inflammatory response with time. Clinical and biochemical investigations indicated acceptable biocompatibility of the device. CONCLUSION: The implantation technique for the ASDOS device in a chronic pig model has been established. Biocompatibility of the device was acceptable. (+info)
Transdermal photopolymerization for minimally invasive implantation.
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Photopolymerizations are widely used in medicine to create polymer networks for use in applications such as bone restorations and coatings for artificial implants. These photopolymerizations occur by directly exposing materials to light in "open" environments such as the oral cavity or during invasive procedures such as surgery. We hypothesized that light, which penetrates tissue including skin, could cause a photopolymerization indirectly. Liquid materials then could be injected s.c. and solidified by exposing the exterior surface of the skin to light. To test this hypothesis, the penetration of UVA and visible light through skin was studied. Modeling predicted the feasibility of transdermal polymerization with only 2 min of light exposure required to photopolymerize an implant underneath human skin. To establish the validity of these modeling studies, transdermal photopolymerization first was applied to tissue engineering by using "injectable" cartilage as a model system. Polymer/chondrocyte constructs were injected s.c. and transdermally photopolymerized. Implants harvested at 2, 4, and 7 weeks demonstrated collagen and proteoglycan production and histology with tissue structure comparable to native neocartilage. To further examine this phenomenon and test the applicability of transdermal photopolymerization for drug release devices, albumin, a model protein, was released for 1 week from photopolymerized hydrogels. With further study, transdermal photpolymerization potentially could be used to create a variety of new, minimally invasive surgical procedures in applications ranging from plastic and orthopedic surgery to tissue engineering and drug delivery. (+info)
Transcatheter closure of a mid-muscular ventricular septal defect with an amplatzer VSD occluder device.
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A 5 year old girl with a haemodynamically significant mid-muscular ventricular septal defect (VSD) had successful transcatheter closure using the Amplatzer VSD occluder. This device passes through a small diameter sheath and can be easily retrieved or repositioned. These properties may make it a suitable device for closure of large mid-muscular defects in small children. (+info)
Limb salvage surgery in bone tumour with modular endoprosthesis.
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Thirty-three patients with bone tumours were treated by resection of the growth and reconstruction with a Kotz modular endoprosthesis. The average follow-up was for 50 months, ranging from 14 to 79 months. At the last review, 12 patients (36%) had died due to the tumour and 9 others (27%) had metastases. All 4 patients with proximal tibial reconstruction had poor functional results, due to an extension lag or to knee stiffness. Four of the six tumours of the proximal femur were complicated by local recurrence or dislocation of the hip, and had poor or fair functional results. Of the patients with distal femoral reconstruction, 17 out of 22 had excellent or good functional results. Reconstruction with a modular prosthesis after resection of a tumour gives excellent or good functional results in more than three-fourths of the cases of distal femur reconstruction, but it should be used with caution in the proximal tibia and proximal femur. (+info)
Transcatheter closure of muscular ventricular septal defects with the amplatzer ventricular septal defect occluder: initial clinical applications in children.
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OBJECTIVES: The aim of this study was to close muscular ventricular septal defects (MVSDs) in children, with a new device, the Amplatzer ventricular septal defect occluder (AVSDO). BACKGROUND: The design of previously used devices for transcatheter closure of MVSDs is not ideal for this purpose and their use has been limited by several drawbacks. METHODS: Six patients, aged 3 to 10 years, with MVSDs underwent transcatheter closure using the AVSDO. The device is a modified self-centering and repositionable Amplatzer device that consists of two low profile disks made of Nitinol wire mesh with a 7-mm connecting waist. The prosthesis size (connecting waist diameter) was chosen according to the measured balloon stretched VSD diameters. A 6-F or 7-F sheath was used for the delivery of the AVSDO. Fluoroscopy and transesophageal echocardiography were utilized for optimal guidance. RESULTS: The location of the defect was midmuscular in five patients and beneath the pulmonary valve in one. The balloon stretched MVSD diameter ranged from 6 to 11 mm. Device placement was successful in all patients, and complete occlusion occurred in all six patients (95% confidence interval 54.06% to 100%). Two patients developed transient complete left bundle branch block. No other complications were observed. CONCLUSIONS: This encouraging initial clinical success indicates that the AVSDO is a promising device for transcatheter closure of MVSDs in children. Further clinical trials and longer follow-up are needed before the widespread use of this technique can be recommended. (+info)
Improved survival rates support left ventricular assist device implantation early after myocardial infarction.
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OBJECTIVES: Implantation of left ventricular assist devices (LVADs) early after acute myocardial infarction (MI) has traditionally been thought to be associated with high mortality rates due to technical limitations and severe end-organ dysfunction. At some experienced centers, doctors have refrained from earlier operation after MI to allow for a period of hemodynamic and end-organ stabilization. METHODS: We retrospectively investigated the effect of preoperative MI on the survival rates of 25 patients who received a Thermocardiosystems Incorporated LVAD either <2 weeks (Early) (n = 15) or >2 weeks (Late) (n = 10) after MI. Outcome variables included perioperative right ventricular assistance (and right-sided circulatory failure), hemodynamic indexes, percent transplanted or explanted, and mortality. RESULTS: No statistically significant differences were demonstrated between demographic, perioperative or hemodynamic variables between the Early and Late groups. Patients in the Early group demonstrated a lower rate of perioperative mechanical right ventricular assistance, but had a higher rate of perioperative inhaled nitric oxide use. In addition, 67% of patients in the Early group survived to transplantation and 7% to explantation, findings comparable to those in the Late group (60% and 0% respectively). CONCLUSIONS: This clinical experience suggests that patients may have comparable outcomes whether implanted early or late after acute MI. These data therefore support the early identification and timely application of this modality in post-MI LVAD candidates, as this strategy may also reveal a subgroup of patients for whom post-MI temporary LVAD insertion may allow for full ventricular recovery. (+info)
Artificial disc replacement with the modular type SB Charite III: 2-year results in 50 prospectively studied patients.
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The Modular Type SB Charite disc prosthesis has been developed as a device for artificial disc replacement (ADR) in patients with symptomatic discopathies. Here, we report on our first series of 50 (out of 350) patients, who had a satisfactory clinical result in 70% of cases (2 years' follow-up). Subgroup analysis revealed that patients with an isolated discopathy without previous spinal operations or other pathology at the same or other spinal level benefitted more from the surgery. However, this technique was associated with some problems: a 13% rate of permanent side-effects and/or complications was observed caused by the anterior approach. Four percent were related to poor implantation technique. There were no problems related to the material of the prosthesis. Twelve patients needed re-operation, but this was beneficial in only three of them. In one patient we had to convert to an interbody fusion. We conclude that in patients with severe isolated symptomatic discopathies that are resistant to conservative treatment, a mobile disc prosthesis is worth considering as a real alternative to a spondylodesis. However, accurate patient selection is imperative. With these criteria we were encouraged by our results to continue the implantation of this artificial disc. (+info)
Long-term histological and electrophysiological results of an inactive epiretinal electrode array implantation in dogs.
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PURPOSE: Short-term pattern electrical stimulation of the retina via multielectrode arrays in humans blind from photoreceptor loss has shown that ambulatory vision and limited character recognition is possible. To develop an implantable retinal prosthesis that would provide useful vision, these results need to be sustained over a prolonged period of retinal electrical stimulation. As a first step toward this goal, the biocompatibility and the feasibility of surgically implanting an electrically inactive electrode array onto the retinal surface was tested. METHODS: A 5 x 5 electrode array (25 platinum disc-shaped electrodes in a silicone matrix) was implanted onto the retinal surface using retinal tacks in each of the 4 mixed-breed sighted dogs. Color fundus photography, fluorescein angiography, electroretinography, and visual evoked potentials were obtained preoperatively, at 1-week intervals for 2 weeks postoperatively, then at 2-week intervals up to 2 months postoperatively, and thereafter at 1-month intervals. One dog was killed at 2 months after implantation and a second dog after 3 months of implantation. Histologic evaluation of the retinas was performed. The remaining two dogs continue to be followed beyond 6 months after the implantation surgery. RESULTS: No retinal detachment, infection, or uncontrolled intraocular bleeding occurred in any of the animals. Retinal tacks and the retinal array remained firmly affixed to the retina throughout the follow-up period. Hyperpigmentation of the retinal pigment epithelium was observed only around the site of retinal tack insertion. No fibrous encapsulation of the implant or intraocular inflammation was visible. A- and b-wave amplitudes of the electroretinogram were depressed at the first postoperative week testing but recovered over the ensuing 1 week and were not statistically different from the normal unoperated fellow eye throughout the postoperative period. N1 and P1 wave amplitudes of the visual evoked potentials were not significantly different from the normal fellow eyes at any of the postoperative test intervals. Fluorescein angiography showed that the entire retina including the area under the electrode array remained well perfused. Similarly, histologic evaluation revealed near total preservation of the retina underlying the electrode array. CONCLUSIONS: Implantation of an electrode array on the epiretinal side (i.e., side closest to the ganglion cell layer) is surgically feasible, with insignificant damage to the underlying retina. The platinum and silicone arrays as well as the metal tacks are biocompatible. With the success of implanting an electrically inactive device onto the retinal surface for prolonged periods, the effects of long-term retinal electrical stimulation are now ready to be tested as the next step toward developing a prototype retinal prosthesis for human use. (+info)