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Gasless videoendoscopic implantation of aortobifemoral vascular prostheses via a transperitoneal approach--an animal experiment.

BACKGROUND: Standard approach for aortobifemoral vascular approach prostheses is the transperitoneal approach, following median laparotomy and bilateral inguinal incision. The goal of this animal experiment was the development of a new minimal-invasive surgical technique utilizing a less-traumatic approach for aortobifemoral bypass. METHODS: The gasless videoendoscopic implantation of 6 x 6 mm diameter aortobifemoral-bifurcation prostheses in transperitoneal approach was tested at the Surgical Department of the University of Cologne in 10 domestic pigs. Gasless videoendoscopic surgery is performed with a laparolift-laparfan-system. After videoendoscopic implantation of aortobifemoral prostheses, all 9 animals underwent laparotomy and resection of the aortobifemoral prosthetic segment. The quality of the endoscopically sutured aortic end-to-side anastomoses was examined under artificial in-vitro circulation of glycerol/ringer-lactate solution for evaluation of possible leakage and bursting pressures. Moreover, the anastomoses were compared to conventionally sutured end-to-side anastomoses of six-hour old porcine abdominal aortas and 6 mm diameter prostheses. The maximum bursting pressure of all endoscopically sutured anastomoses averaged 450 mmHg, whereby the minimum bursting pressure amounted to 100 mmHg mean pressure. RESULTS: Aortobifemoral prostheses were successfully implanted in 9 out of 10 animals, one animal dying during preparation for the surgery, succumbing to massive coronary infarctions. Surgical durations for the transperitoneal approach averaged four hours, whereby surgical durations were reduced with increasing experience to a minimum of 3 hours 30 minutes. Dissection of the infrarenal aorta until occlusion required 35 minutes. Average aortic occlusion duration amounted to 1 hour; iliacofemoral occlusion duration amounted to 1 hour for each side. The leakage per minute at the beginning achieved a maximum of 80 ml/min and systolic pressure values of 350 mmHg in consideration of all flow levels, 60 ml/min for systolic pressure values of 200 mmHg and 20 ml/min for systolic pressure values of 120 mmHg. The minimum level leakage per minute was less than 10 ml/min for systolic pressure values between 120-350 mmHg. CONCLUSION: Gasless videoendoscopic implantation of aortobifemoral vascular prostheses in transperitoneal approach is practicable in animal experiments. All endoscopically sutured aortic endo-side anastomoses were comparable to conventionally sutured anastomoses in in-vitro evaluation of bursting pressure and leakage per minute.

Animals↗

The behavior of different types of polytetrafluoroethylene (PTFE) prostheses in the reparative scarring process of abdominal wall defects.

Currently one of the most widely used prosthetic materials in the repair of abdominal wall defects, is expanded polytetrafluoroethylene (ePTFE). It has been suggested that its behavior with respect to the reparative process may depend on its structure. The aim of the present study was to evaluate the effect of the structure of 3 ePTFE prostheses on the scarring process in an abdominal-wall-defect experimental model. The prostheses employed were the Soft Tissue Patch (STP) which is laminar in structure, Mycro Mesh (MM) which is multilaminar with perforations, and the Dual Mesh (DM) prosthesis which has one non-porous surface. Abdominal wall defects (7 x 5 cm) were created in 36 New Zealand rabbits and repaired using fragments of STP, MM and DM. Follow-up periods were 14, 30, 60 and 90 days post-implant. At these times prostheses were macroscopically examined for the presence of infection and/or rejection and the formation of adhesions to abdominal viscera. Specimens were also taken for microscopic analysis (optical and scanning electron) and for immunohistochemical analysis using the rabbit macrophage-specific monoclonal antibody RAM-11. Labelled macrophage counts were performed at each follow-up session. No cases of infection or rejection were found. Loose adhesions between prosthesis and underlying viscera were observed in 2 of the STP, 4 of the MM and 2 of the DM implants. STP and DM implants were progressively encapsulated by organized connective tissue on both peritoneal and subcutaneous surfaces. Cellular colonization was observed on both STP surfaces and on the porous surface of the DM although no more than a third of the biomaterial was penetrated by cells in either case. Colonization was very slight at prosthesis anchorage points. MM implants differed only in the formation of connective tissue bridges in perforated areas, and cellular infiltration in interlaminar spaces. Macrophage response was similar in the 3 prostheses with a reduction in RAM-11 labelled cells (p < 0.05) between 14 and 90 days post-implant. We conclude: a) the 3 types of PTFE prosthesis induced low incidence of adhesion formation between biomaterial and viscera; b) integration mechanism of the 3 prostheses were similar and culminated with the encapsulation of the PTFE by the neoformed tissue; c) the macrophage response induced by the 3 prostheses was similar to that of any reparative process in the absence of biomaterial.

Abdominal Muscles↗

Amputation and prostheses in Khartoum.

One hundred and seventy patients with major lower limb amputation (MLLA) presenting to The National Prosthetic-Orthotic Centre (NPOC) in Khartoum over a 1-year period were studied. There were 141 males and 29 females giving a M:F ratio of 4.9: 1.0, with mean age of 37 years (range 5-72 years). Forty-one patients (24%) underwent amputation of diabetic septic foot, 30 patients (17.6%) underwent amputation as a result of trauma from road traffic accidents and Madura foot, and war injuries accounted for 29 amputations (17%). One hundred and eleven patients had below knee amputation (BKA), 52 had above knee amputation (AKA) and seven patients had Syme's amputation. Diabetic amputees had higher rate of revisional surgery compared with others because of sepsis and/or flap necrosis. Stump pain was reported by amputees with excessive scarring of the stump and those with undue prominence of bony ends. There are two types of prostheses provided by the NPOC for both BKA and AKA: the peg leg and the conventional prostheses. The Syme's amputees were fitted with either simple hoof or articulated prostheses with solid ankle cushion heel (SACH). The peg leg consists of a leather lined side bearing metal socket connected to a rocker base by side steels. It is used by the country natives as it suits different weather and job conditions, particularly farming, and it can be repaired locally. The urban population use the conventional prostheses which is lighter in weight, can be put on and taken off easily and is cosmetically acceptable. However, these prostheses are more expensive and require frequent repair or replacement. The functional outcome of patient's rehabilitation with the prostheses was significantly affected by the level and indication of amputation. Those with BKA and those amputated because of trauma or Madura foot experienced better functional outcome compared with the diabetics, independent of age. 50% of patients with the AKA and 19% of those with BKA reported poor functional outcome. Surgeons should be more involved with the long-term evaluation of functional outcome in such patients, to offer help if feasible and to modify their technique for future procedures.

Adolescent↗

[Review of applying implant-magnetic attachments to oral and maxillofacial prostheses].

In order to evaluate the applying effect of MDIC implant-magnetic attachments on oral and maxillofacial prostheses, 38 patients, whose oral and maxillofacial defects had been restored with implant-magnetic attachments prostheses, were followed up for 1-4 years. The effects were evaluated by the measurement of the retentive force of the prostheses, X-ray and clinical examination. The results show: the successful rate of the restoration was 94.7%; two sets implant-magnetic attachments could offer an average of 14.7 N retentive force for lower complete dentures, which could meet various functional needs of the prostheses, but magnetic retentive force decreased as the applying time goes on the magnetic retainers should be changed after two years; negative rate of bone absorption on implant-bone surface was 92.6%; negative rate of gingival inflammation was 91.3%. The implant-magnetic attachments offer realize reliable retention, don't transmit lateral force to implants. Patients can insert and remove the prostheses and clean the implants and defect cavities conveniently. The above advantages are benefit to tissue health and functions of the prostheses. So, implant-magnetic attachments can be used in the restoration of various oral and maxillofacial defects.

Bone Resorption↗

19 mm sized bileaflet valve prostheses' flow field investigated by bidimensional laser Doppler anemometry (part II: maximum turbulent shear stresses)

The investigation of the flow field generated by cardiac valve prostheses is a necessary task to gain knowledge on the possible relationship between turbulence-derived stresses and the hemolytic and thrombogenic complications in patients after valve replacement. The study of turbulence flows downstream of cardiac prostheses, in literature, especially concerns large-sized prostheses with a variable flow regime from very low up to 6 L/min. The Food and Drug Administration draft guidance requires the study of the minimum prosthetic size at a high cardiac output to reach the maximum Reynolds number conditions. Within the framework of a national research project regarding the characterization of cardiovascular endoprostheses, an in-depth study of turbulence generated downstream of bileaflet cardiac valves is currently under way at the Laboratory of Biomedical Engineering of the Istituto Superiore di Sanita. Four models of 19 mm bileaflet valve prostheses were used: St Jude Medical HP, Edwards Tekna, Sorin Bicarbon, and CarboMedics. The prostheses were selected for the nominal Tissue Annulus Diameter as reported by manufacturers without any assessment of valve sizing method, and were mounted in aortic position. The aortic geometry was scaled for 19 mm prostheses using angiographic data. The turbulence-derived shear stresses were investigated very close to the valve (0.35 D0), using a bidimensional Laser Doppler anemometry system and applying the Principal Stress Analysis. Results concern typical turbulence quantities during a 50 ms window at peak flow in the systolic phase. Conclusions are drawn regarding the turbulence associated to valve design features, as well as the possible damage to blood constituents.

Aortic Valve↗

Histopathological studies in the long-term evaluation of Plastipore prostheses.

Polyethylene sponge (Plastipore TM) prostheses were clinically implanted in the middle ear for periods varying from 2 weeks to 6 years. Revision surgery allowed removal of 98 of these prostheses for histological examinations. Local foreign body reactions and/or microscopic breakdown of the polyethylene were found to varying degrees in 95 of the 98 prostheses. The remaining 3 prostheses showed only fibrous tissue ingrowth without other changes. We compared the histopathology present with the length of time of implantation, and found that the changes noted were more frequent and marked in those prostheses implanted for long periods of time.

Biocompatible Materials↗

Biocompatibility and ingrowth of Trevira prostheses following replacement of the cruciate ligaments.

Five of 97 cruciate ligament prostheses (5.15 per cent) implanted for an average of 3 years (8-53 months) in 70 patients with acute chronic cruciate ligament instability were removed due to failure after a mean of 9 (3-15) months. Investigation of the explanted polyethylene terephthalate (PET)-grafts by scanning electron and light microscopy showed not bony but fibrous tissue ingrowth in all parts of the prostheses. The extent of local host response in the interface region differed with the intensity of mechanical strain at the three parts of the prostheses (intra-articular, bone tunnel, cortical). Inflammatory cells and foreign body giant cells were abundant close to the rupture sites at the intra-articular entries of the bone tunnels and scarce at the intra-articular part of the prostheses and at the cortical anchoring. Evaluation of the reasons for early prostheses failure indicates that (1) non-ideal placement of bone tunnels and (2) inadequate strain were responsible for reoccurring instability and rupture after prosthetic cruciate ligament replacement.

Anterior Cruciate Ligament↗

Comparative animal study of three ligament prostheses for the replacement of the anterior cruciate and medial collateral ligament.

Three different ligament prostheses (Leeds-Keio, Gore-Tex and a prototype of Aramid) were implanted in sheep knee joints replacing the anterior cruciate ligament and the medial collateral ligament. After 1 yr the knees were explanted and their biomechanical properties were assessed by a drawer test and tensile tests of the implants. Additionally the ligament replacements, the synovial membrane and the lymph nodes were inspected histologically. For each type of prosthesis partial or total ruptures occurred. None of the operated joints regained normal stability and stiffness. Anterior knee stability was best for the Gore-Tex treated group and worst for those joints that received a Leeds-Keio implant. The stiffness and rupture strength were highest for the Gore-Tex prostheses. Histologically the strongest intra-articular inflammatory response was observed in the Gore-Tex treated joints. Inside the drill tunnels the severest foreign body reaction was found for the Aramid prostheses. Gore-Tex fibres often showed good bony integration. Wear particles formed from all prostheses and caused small granulomas and mild synovities. The results suggest that none of the tested materials represent an ideal solution for ligament replacement. Relatively good stability does not guarantee good biocompatibility and vice versa. This suggests that ligament prostheses should be applied only in salvage cases.

Animals↗

Carcinogenicity of metal alloys in orthopedic prostheses: clinical and experimental studies.

Case reports of malignant tumors at sites of metal orthopedic implants in humans and domestic animals reviewed; results of carcinogenesis bioassays of implanted metal alloys and of nickel, chromium, cobalt, and titanium powders in rodents are summarized; mobilization of metals from implanted prostheses is discussed; and in vitro assays for morphological transformation of mammalian cells by metal compounds are surveyed. These considerations suggest that occurrence of sarcoma at the implantation site constitutes a complication, albeit rare, of implanted orthopedic prostheses. The author recommends (a) that orthopedic surgeons select prostheses with minimal susceptibility to metal corrosion and wear and, if feasible, replace implanted prostheses when there is evidence of corrosion or mechanical failure; (b) that epidemiological studies be undertaken to quantify cancer risks in patients with various types of metal implants; (c) that an international registry of implant-associated tumors be established; and (d) that research be focused on improved in vitro assays for carcinogenicity of alloys intended for use in orthopedic prostheses.

Alloys↗

Coated self-expanding metal stents versus latex prostheses for esophagogastric cancer with special reference to prior radiation and chemotherapy: a controlled, prospective study.

BACKGROUND: Self-expanding metal stents seem to be safer than conventional prostheses for palliation of malignant esophagogastric obstruction. However, recurrent dysphagia caused by tumor ingrowth in uncoated types remains a problem. In addition, prior radiation and/or chemotherapy may entail an increased risk of complications. METHODS: Seventy-five patients with an esophagogastric carcinoma were randomly assigned to placement of a latex prosthesis under general anesthesia or a coated, self-expanding metal stent under sedation. At entry, patients were stratified for location of the tumor in the esophagus or cardia and for prior radiation and/or chemotherapy. RESULTS: Technical success and improvement in dysphagia score were similar in both groups. Major complications were more frequent with latex prostheses (47%) than with metal stents (16%) (odds ratio 4.07: 95% CI [1.35, 12.50], p = 0.014). Recurrent dysphagia was not different between latex prostheses (26%) and metal stents (24%). Hospital stay was longer, on average, after placement of latex prostheses than metal stents (6.3 +/- 5.2 versus 4.3 +/- 2.3 days; p = 0.043). Only prior radiation and/or chemotherapy increased the risk of specific device-related complications with respect to the esophagus (12 of 28 [43%] versus 8 of 47 [17%]; odds ratio 3.66: 95% CI [1.24, 10.82], p = 0.029). CONCLUSIONS: Coated, self-expanding metal stents are associated with fewer complications and shorter hospital stay as compared with latex prostheses, and prior radiation and/or chemotherapy increases the risk of device-related complications with respect to the esophagus.

Aged↗

Speech-aid prostheses for neurogenic velopharyngeal incompetence.

STATEMENT OF PROBLEM: When surgical treatment is not considered an option, prosthetic management of velopharyngeal insufficiency is carried out by means of a speech-aid prosthesis, whereas velopharyngeal incompetence is traditionally managed by a palatal lift prosthesis. Varying degrees of treatment success have been attributed to palatal lift prostheses. PURPOSE: This study introduces the use of nasopharyngeal obturation instead of palatal elevation for the management of velopharyngeal incompetence. METHODS: Seven patients afflicted by neurogenic velopharyngeal incompetence were treated with wire-extension speech-aid prostheses constructed to circumvent the dysfunctional soft palate. The shape of the nasopharyngeal section was functionally molded in speech and swallowing and controlled by video-nasopharyngoscopic examinations. RESULTS: Effective nasopharyngeal obturation with notable improved speech was achieved in all patients. Even though all patients ultimately tolerated the prostheses well, 2 patients denied any improvement in speech with the finalized prostheses. CONCLUSION: Wire-extension speech-aid prostheses used by the patients were an effective treatment approach for velopharyngeal incompetence. Nasopharyngoscopic control is mandatory for maximizing the effect of velopharyngeal closure around the nasopharyngeal section of the prosthesis in function, yet it allows free nasal breathing. Velopharyngeally incompetent patients should be carefully tailored for prosthetic treatment because of contingent noncompliance.

Adult↗

Benefits and use of digital prostheses.

This study examines our clinical experience of fitting 136 digital prostheses in 90 patients. The careful selection of patients, especially concerning their expectations, is the single most important factor for successful prosthetic development for physically suitable candidates. Whether continued disability is due to physical loss or to its emotional impact, the socioeconomic consequences are similar, so attention to both is required. In a review of 30 patients fitted with digital prostheses after a minimum follow-up time of 2 years, it was found that 22 (73%) used their prostheses daily and another 7 (23%) used them intermittently according to the occasion. Thus, a total of 29 (97%) of those fitted with our digital prosthesis continued to use them after 2 years. Technical problems, such as loose fit and perspiration, resulted in 7 (23%) of the patients using the prostheses only occasionally. Fitting a prosthesis goes beyond aesthetics, and our study confirmed that digital prostheses, if of high quality, can alone or in conjunction with appropriate surgical reconstructions restore near normal appearance and form, substantially repair damaged body image, and simultaneously improve physical capability.

Adolescent↗

Integration of laser surface digitizing with CAD/CAM techniques for developing facial prostheses. Part 2: Development of molding techniques for casting prosthetic parts.

PURPOSE: This article presents a novel manufacturing approach that integrates laser surface digitizing/scanning and computer-aided design and manufacturing (CAD/CAM) to achieve automated fabrication of spatially and anatomically accurate extraoral facial prostheses. MATERIALS AND METHODS: Contrary to the approach in part 1 for fabricating positive replicas of prostheses, the approaches presented here are focused on designing and producing negative molds of the final prostheses using CAD, rapid prototyping, and rapid tooling techniques. The molds were applied directly to cast the final prostheses, thereby eliminating conventional flasking and investing procedures. RESULTS: Three different facial prostheses were produced to evaluate the proposed approach for prosthesis production. The advantages of this alternative manufacturing approach over the approach presented in part 1 and conventional techniques are discussed. The limitations encountered with the integrated manufacturing system are highlighted. CONCLUSION: With the new techniques, reduced patient discomfort, minimal dependence on the artistic skills of the prosthetist, and short turnaround times for prosthesis production can be expected.

Biocompatible Materials↗

[Effect of CO2 laser on prostheses used in middle ear surgery].

The use of CO2 laser is advocated in primary and revision stapes surgery. The aim of the study was to assess the effect of CO2 laser on stapes prostheses. CO2 laser was applied on several types of stapes prostheses and PORPs, with power settings suggested by the manufacturer (continuous wave, 2 W and 6 W; 0,05 s). Application of the laser on stainless steel or titanium prosthesis did not exert any effect on the structure of the prosthesis. The use of the laser on the Teflon piston caused superficial burning with power 2 W, and melting and holes in the piston with power settings at 6W. Similar plastipore prostheses were melting. Hydroxyapatite PORP shattered after application of the laser energy. Teflon and hydroxyapatite prostheses are easily damaged by the laser energy, therefore applying a laser on them should be avoided. CO2 laser can be used on stainless steel and titanium prostheses without risk of damaging them. However the possibility of transmission of heat to the vestibule has to be taken into consideration.

Carbon Dioxide↗

Platelet changes after placement of aortic prostheses in dogs. I. Biochemical and functional alterations.

Changes in circulating platelets were observed after placement of woven Dacron aortic prostheses in dogs. Platelets had increased sensitivity to aggregating agents for up to 6 months postoperatively, during which period platelet survival was maximally shortened. Platelet survival gradually lengthened but remained less than preoperative values, even at 18 months. Platelet 5HT, consistently reduced after placement of aortic prostheses, closely paralleled changes in platelet survival. Studies with platelets labeled simultaneously with 14C-5HT and 51Cr suggested in vivo platelet release and reutilization of 5HT. In vitro platelet uptake of 14C-5HT, however, was depressed. Urinary excretion of 5HIAA increased slightly, but not significantly, after placement of aortic prostheses. These findings suggested that platelet interaction with the prosthetic surface led to partial release of platelet storage granule contents. Reutilization of released 5HT occurred but was limited because of impaired platelet uptake or storage of 5HT. Platelet damage was suggested by 51Cr-platelet cross-transfusion experiments. Platelets from normal dogs had normal recovery and reduced survival when cross-transfused into animals with aortic prostheses. When platelets from dogs with aortic prostheses were cross-transfused into normal animals, recovery was strikingly reduced and survival very short. Taken together, these studies suggest that, in dogs, platelet interaction in thrombosis on prosthetic surfaces is, in part, a reversible process, with platelets re-entering the circulation in an altered state.

Adenosine Diphosphate↗

Capsular contracture after breast augmentation--a comparison between gel- and saline-filled prostheses.

Capsular contracture around the breast prostheses remains the major drawback to the otherwise very satisfying operation of breast augmentation. The possible aetiology of this complication is discussed and local aggravating factors are implicated. The two major types of modern breast prostheses are the Silastic gel-filled and the inflatable. A short-term retrospective clinical study was conducted on 79 augmented breasts to compare the contracture rate when using the gel-filled and the inflatable prostheses--90,7% of the gel-filled prostheses developed capsular contracture (the majority grade III), compared with 22,2% of the inflatables (the majority grade II). On the basis of this trial, we now only use inflatable prostheses for breast augmentation.

Breast↗

Effect of dairy products on the lifetime of Provox2 voice prostheses in vitro and in vivo.

BACKGROUND: Reduction of biofilm formation on tracheoesophageal voice prostheses by certain dairy products might extend their clinical lifetime. The purpose of this study was to determine the influence of certain dairy products on voice prosthetic biofilms and lifetimes in vitro and in vivo. METHODS: The in vitro results were accomplished using an artificial throat. The lifetimes of Provox2 prostheses were evaluated in a patient group that daily consumed the evaluated products. RESULTS: Buttermilk and Yakult Light fermented milk decreased the amount of bacteria on voice prostheses but stimulated yeast prevalence in vitro. Concurrently, lifetimes of voice prostheses in patients consuming buttermilk were not significantly different, whereas patients consuming Yakult Light fermented milk drink had a significantly (p < .01) increased prosthesis lifetime by a factor of 3.76. CONCLUSION: Yakult Light fermented milk drink reduced biofilm formation on Provox2 prostheses in vitro and in vivo and significantly increased prosthesis lifetime. In vivo, no significant effects were observed for patients consuming buttermilk.

Aged↗

Endothelial cells on Dacron vascular prostheses: adherence, growth, and susceptibility to neutrophils.

Human umbilical vein endothelial cells (HUVEC) on knitted and woven Dacron prostheses were compared with HUVEC on smooth surfaces (tissue culture polystyrene, PET film, and Natrix) with regard to adherence, growth, and susceptibility to injury by neutrophils (PMN). These are properties of importance for successful seeding or coating of prostheses. For prosthetic material of given macroscopic dimensions, more endothelial cells (EC) adhered than to smooth surfaces. However, the prostheses had a greater effective surface area as determined by the number of EC at confluency. When this parameter was taken into account, fewer EC were found adherent to prosthetic material per unit effective surface area than for the smooth surface substrates. Growth on prostheses was clearly inferior to that on smooth surfaces, and EC on prostheses were more susceptible to attack by activated PMN than on smooth surfaces. These differences may reflect the topographic differences in cells attached to fibers where they assume more distorted shapes by stretching to span fibers.

Antibodies, Monoclonal↗