Journal of Bioscience and BioengineeringVOL. 110 No. 2, 242–249, 2010
www.elsevier.com/locate/jbiosc
Novel implant for transcervical sterilization
Muhammad Rehan,1 James Coleman,2 and Abdul Ghani Olabi1,⁎
⁎ CorrespondE-mail add
1389-1723/$doi:10.1016/
School of Mechanical and Manufacturing Engineering, Dublin City University, Glasnevin, Dublin 9, Ireland1 and Alta Science, Trinitas House, 2012 OrchardAvenue, Citywest Campus, Citywest, Dublin 24, Ireland2
Received 29 October 2009; accepted 2 February 2010Available online 9 March 2010
Compared to laparoscopic surgery for interval tubal sterilization, the transcervical approach is an effectivemethod of femalesterilization which obviates the requirement of general anesthesia and surgical incision. However, current methods oftranscervical sterilization are unable to provide an instant occlusion. This paper focuses on the design, development and testingof a novel implant (James E., Coleman, Christy Cummins, 2009. Anastomosis Devices and Method. US Patent 20090105733A1) toachieve instant permanent female sterilization via the transcervical approach. The implant is designed to be deployed underhysteroscopic visualization into the ostium of the fallopian tube and relies on instant mechanical occlusion. The implantincludes two sets ofwings that penetrate into the ostium and uterinemuscle tissue and trap the tissue in between thus pluggingthe entrance of the fallopian tube. In order to design the shape of implant wings and to investigate the mechanical behavior ofthe implant, a three-dimensional (3D) model was developed and Finite Element Method (FEM) was used for simulations. Theimplantwas validated by anumber of successful deployments in bench testing, animal tissue and explanted humanuteri. Duringthe deployments in animal tissue and explanted uteri, itwas observed that the two sets ofwings completely trapped the tissue inbetween and the hydraulic pressure testing of the explanted uteri using saline solution and methylene blue proved the instantocclusion of the fallopian tubes. Initial results suggest that this novel implant provides a safe and effective method of femalesterilization. Further development work is ongoing in preparation for “first-in-man” clinical trials.
Female sterilization by laparoscopic occlusion of the fallopian tubesis a widely used method for family planning because of its provensafety and effectiveness (1). About 14 million couples per annum arerelying on female sterilization to avoid further pregnancies (2).Regardless of such an apparent demand for sterilization, there havebeen very few technological developments during the last decade insterilization methods either via the approach to the fallopian tubes orof tubal occlusion (3). Conventional and most common surgicalprocedures were the minilaparotomy and tubal ligation (2). Theadvent of fiber-optic laparoscopy opened the path for other techniquessuch as electrocoagulation or clip or ring application to the tubes (3).However, these approaches to female sterilization carry risksassociated with general anesthesia and on rare occasions can resultin vascular damage, injury to the bowel, bladder, or uterus andmay beassociated with postoperative pain (4).
The transcervical approach is an alternative to incisional proce-dures for interval tubal sterilization as it eliminates the need forsurgery and general anesthesia. Transcervical approach to occlude thefallopian tubes via the uterine cavity is not new and has been studiedfor more than 150 years (5). Transcervical sterilization can becategorized in to destructive and mechanical occlusive methods. Indestructive methods the research has mainly focused on chemicalcausticts, tissue adhesives, thermic induction and also the Nd:YAG
laser (6, 7). Contrary to the destructivemethods of burning, freezing orfibrosing, the tubal ostia can be occluded by mean of mechanicaldevices. Such intratubal devices are mostly applied by hysteroscopyand occlusion can be achieved either by placing a pre-formed plug ordevice in the uterotubal orifice or by formed-in-situ methods. Thetechnological developments in endoscopes, light transmissiondevices,optical resolution, catheters and tubal cannulation evolved some newtechnologies such as the Adiana and Essure devices (5). However, boththe Adiana (8, 9) and Essure (10–12) procedures relies on tissue in-growth from the surrounding tubal walls and sterilization requires3 months after device placement. This is inconvenient for the patient,who has to use an alternate contraception during this time, whichmeans an additional cost of contraception and the procedure todemonstrate tubal occlusion. Therefore, the requirement was todevelop a transcervical approach that can provide an instant occlusionof fallopian tube.
This paper presents design, development and testing of a novelimplant for occlusion of fallopian tubes in order to provide a methodfor immediate and permanent transcervical female sterilization. Thisimplant is deployed into the tubal ostium under hysteroscopicvisualization and relies on instant mechanical occlusion to effecttubal occlusion. The implant includes two set of six slots on its mainbody. These slots transform into two set of six wings that penetratesinto the ostium and uterine muscle tissue and traps the tissue inbetween thus plugging the entrance of fallopian tube. In order toreduce the development time of the implant, FEA simulation along
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with experimental testing was used to achieve the design of theimplant. FEM was used to predict the profile of the slots and tosimulate the mechanical behavior of the implant during deployment.This predicted design of the slots and implant was then further testedand finalized with the help of prototyping and experimentation. Thisimplant was validated a number of times by successful deploymentson the bench, in animal tissue and in explanted human uterus. Duringthe deployments in animal tissue and explanted uteri, it was observedthat the two sets of wings completely trapped the tissue in betweenand the hydraulic pressure testing of the explanted uteri using salinesolution and methylene blue proved the instant occlusion of thefallopian tubes.
MATERIALS AND METHODS
The human fallopian tubes are paired, tubular, seromuscular organs whose courseruns medially from the cornua of the uterus and laterally toward the ovary. In additionto being the normal site of fertilization, the tubes act as ducts for sperm, oocyte andfertilized ovum transport. The intramural segment is contained in the wall of the uterusbeginning at the uterotubal ostium and ending at the uterotubal junction (UTJ) (13).
The novel implant presented in this paper is designed to be deployed into the uterotubal ostium as shown in Fig. 1. The un-deployed implant as shown in Fig. 2 comprisesof a guide tip at distal end, a slotted cylindrical body housing a core pin and releasesystem. The design of the delivery guide tip and the release mechanism of the implantwill be discussed in later publications.
The following characteristics should form part of the design of an ideal occlusionimplant: It should be deliverable through a small caliber hysteroscope, provide aninstant occlusion, have a low profiled shape during insertion, be capable of anchoring attarget location and be quick, easy and safe to both locate and deploy. In this study, aninnovative design based on a cylindrical implant having two set ofwings or prongs on itssurface was envisioned based on experienced physicians' feedback and study of uterusanatomy to qualify on these attributes. However, the most challenging task was todevice a design that can transform a cylindrical body into an implant capable ofanchoring into the tubal ostium and to provide an instant occlusion of fallopian tube.Designing such an implant through prototyping and experimental testing is timeconsuming and expensive. Therefore, FEA simulation in conjunction with experimentaltesting was used to achieve the optimum design of the implant. First, FEA simulationswere performed to evaluate the shape of slots, transformable into flat wings, capable toanchor, able to penetrate and trap the tissue in between. Second, the mechanicalbehavior of complete implant with these finalized slots was simulated and analyzed.Finally, the implant was fabricated and on bench tested to validate the deployment anddesign. Testing in animal tissue validated the deployment, anchoring and in-tissuetrapping. Further tests in the explanted uterus were performed to validate theplacement, deployment, anchoring of the implant and occlusion of fallopian tube.
The implant consists of an annealed SS-316LVM tube featuring two sets of six slotsat both the distal and proximal segments of the implant (Fig. 2). These slots determinethe implant final shape following deployment by formation of two set of six wings. Acomplete depiction of a deployed implant is shown in Fig. 3. These wings serve toanchor the implant and trap the tissue of the intramural section of the tube in betweento instantaneously occlude the fallopian tubes. The size of implant is chosen such that itcan be delivered transcervically through a 5-Fr (1.665 mm) operative channel of astandard hysteroscope. The implant is designed to be positioned optimally in the
FIG. 1. Deployed Implant at the left tubal ostium.
intramural section of the fallopian tube. The implant is inserted in low profiledcylindrical form, through the working channel of the hysteroscope bymean of a flexibleguide tube and inner guide wire. Since the implant requires torque and compression fordeployment, these guide tube and wire therefore also serves the purpose of torquetransmission and compression to the implant. The deployment of implant is achieved inthree phases. In the first phase, a counter-clockwise torque followed by a compressionforce transforms the distal slots into six fully formed wings. The second phasecomprises of a clockwise torque and compression to achieve deployment of the secondset of six proximal wings. Finally, the third phase completes the deployment process bydispensing the implant from the guide wire and consequently the delivery tube.
Model geometry The 3D model of the implant was generated using ComputerAided Design (CAD) software. The 3D parametric model of the implant generated usingCAD software Pro/EngineerWildfire 3.0 (Pro/E) is shown in Fig. 4. The implant consistsof annealed SS-316LVM tube having an outer diameter of 1.535 mm, thickness 0.1 mmand length 6.5 mm. It includes an inner release system which includes a core pin andrelease tube. The core pin is hardened SS-316LVM solid shaft, whose one end is conicaland laser welded to the distal end of the implant and other end attached to the guidewire. The cylindrical shaped implant has two sets of slots at the distal and proximalsegments and axial straight splines on the proximal end as shown in Fig 4. Each set ofslots comprises of six “S” shaped cutouts and both set of slots have a bilateral symmetry(mirror symmetry). The transformation from these slots into wings occurs by a twostep procedure; first torque followed by compression. Torque and compression aretransmitted to the implant by a delivery actuator through a combination of flexibleguide tube and wire. The details of the delivery actuator, guide tube and wire will bediscussed in future papers. The flexible guide tube is coupled with the implant throughthe straight splines and guide wire is connected to the inner tube. Hence, distal end ofimplant is held by guide wire and proximal end by flexible guide tube. Application oftorque initiates the formation of wings by radially expanding the slots as shown in Fig. 5and compression concludes their formation by plastically deforming them to a finalshape as shown in Fig. 6. As both sets of slots have bilateral symmetry, therefore onlyone set of wings can be formed by applying torque in one direction. To deploy thesecond set of wings a torque in opposite direction followed by compression is required.
FIG. 3. Implant post-deployment.
FIG. 4. 3D model of the un-deployed implant.
FIG. 6. Wings formation post-compression.
244 REHAN ET AL. J. BIOSCI. BIOENG.,
The axial straight splines at the proximal end of the implant are used to couple theimplant with the flexible guide tube and consequently to the delivery system. This 3Dmodel of implant was further used for FEA simulation and generating Computer andNumerically Controlled (CNC) program for laser cutting machine.
FEA simulations Finite Element Analysis (FEA) software ANSYS Workbench(WB) was used for FE simulations and analysis. The parametric model generated inPro/E was integrated with ANSYS WB for FEA simulations (14, manuscript submitted).The first objective of these simulations was to predict and investigate the slots profile.Therefore, it was unnecessary to simulate the whole implant only for the evaluation ofslots profile. Due to bilateral symmetry considerations, half of the whole model havingone set of six slots was considered for simulations. Non-linear analysis was performedin ANSYS WB in order to cope with large deflections and plastic deformations in theimplant during its deployment. To simulate implant deployment, a bilinear isotropichardening rule was adapted to describe the mechanical properties of the material.Material properties of annealed SS-316LVM were assigned in the ANSYS WBenvironment. Young's modulus E used for this material was 193 GPa, Poisson ratio υwas 0.3, yield strength σy was 286 MPa and the tangentional modulus Et for the plastichardening phase was 2.5 GPa. As mentioned in the “model geometry” section, theimplant houses a core pin and a release tube. The core pin serves two purposes; first, itis an interface between the implant, release system and guide tip. Second, it provides asliding surface to the implant during deployment and only permits the translation androtation along and about X-axis, which prevents the implant from buckling. Boundaryconditions were applied to simulate the actual conditions in which fixed displacementwas applied at the proximal end of implant. As the implant can only slide and rotateabout the core pin, the translational and rotational displacement of UY, UZ, RY and RZwere constrained at the proximal end. The load was applied in two load sets at thedistal end. First, clockwisemomentwas applied in six load steps. Second, a compressionforce was applied in fifteen load steps to deal with the maximum plastic strain andsolution convergence during each step. Mesh density was tested and the default meshwas refined by defining the element size. The volume of the implant was meshed with
FIG. 5. Radial expansion of slots on torque application.
hexahedron elements and there were 114374 nodes and 31143 elements in the model.The FEmesh, von-Mises stress distributions at the conclusion of each load step and totaldeformation at the final step are shown respectively in Figs. 7a, b, c and d. As there wasno pre-defined design of the slots or implant, a primitive geometry (a “C” shaped slot)was selected as a starting point for slot design. An optimum profile of the slots that cantransform the implant into the desired wing shape was then achieved through variousiterations by manually modifying the slot profiles by interpreting the deformed shapeobtained by the FEA results. A range of the slots profiles and combinations of momentand compression were attempted to achieve the desired profile of slots andconsequently shape of implant wings. Fig. 8 shows some of the slot profiles simulatedin order to arrive at the finalized design.
In order to simulate the deployment of whole implant and to investigate itsmechanical behavior, the complete model of implant, including two sets of six slots wasused. A sequence comprising of four load sets was adopted to simulate the deploymentphases:
Load Set 1: counter-clockwise moment to achieve an out-of-plane displacement indistal slots.Load Set 2: compression to transform displaced slots into fully deployed distalwings.Load Set 3: clockwise moment to achieve an out-of-plane displacement in proximalslots.Load Set 4: compression to transform displaced slots into fully deployed distalwings.
These load sets were applied in 42 load steps at the distal end of the implant. Themodel was constrained in the same way as described previously for the half model.However, surface-to-surface frictional contacts were defined in between the slotsurfaces to prevent model penetration. A coefficient of friction 0.74 for SS316 was usedfor these contacts (15). Mesh density was refined by redefining the element size. Thevolume of the implant was meshed with hexahedron elements and there were 231292nodes and 64322 elements in the model. The von-Mises stress distributions at the endof each load step are shown in Figs. 9a–d.
The axial straight splines at proximal end were analyzed independently to simplifythe analysis and to reduce computation time. The parametric models of the implantsplines and corresponding splines of the guide tube were generated in Pro/E. Thewhole coupling assembly was integrated with ANSYS WB for linear contact analysis.Frictional contact was defined in between implant and guide tube splines. As bothcomponents were of SS-316, a coefficient of friction 0.74 was used for this contact.Fixed displacement was applied on the opposite end of the implant splines. Acylindrical support boundary condition was applied at the inner surface of guide tubeand a moment of 16 N-mm was applied on the opposite end of guide tube splines.Fig. 10 shows the von-Mises stress distribution in splines of implant after linear contactanalysis.
Development Due to the miniature size of the implant including features thathave dimensions of micron level, it was impossible to manufacture it with standardmechanical manufacturing techniques. It proved also intricate to machine because ofthe softness of the light walled annealed SS-316LVM tubing. In view of this, a laser(light amplification by stimulated emission of radiation) cutting system providedfabrication alternative down to micron level. Therefore, a specialized laser cuttingmachine (LPL Stent Cutter) was used for cutting profile of the implant. This machineuses pulsed Nd:YAG (neodymium:yttrium aluminium) beam source for precision
FIG. 7. FE simulations of half implant for evaluation of slot profile (a) FE Mesh (b) von-Mises stress distribution at end of Load Step 1 (c) von-Mises Stress distribution at end of LoadStep 2 (d) total deformation at end of Load Step 2.
FIG. 8. Some slot profiles simulated prior to final design.
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FIG. 9. von-Mises Stress distribution in whole implant at the end of (a) Load Step 1 (b) Load Step 2 (c) Load Step 3 (d) Load Step 4.
246 REHAN ET AL. J. BIOSCI. BIOENG.,
cutting. It has longer focal length lens for excellent beam quality, which minimizestaper in the cut (LPL Systems, Inc.). This assures a high cutting quality, which ischaracterized by narrow cuts and near parallel gap edges. The other advantage of thisfabrication method is that it is gentle on the extremely fragile tube of annealed SS-316LVM with a small wall thickness. Therefore, the implant fabricated by this lasermachine was extremely precise within a linear accuracy of 2.54 μm and angularaccuracy of 0.028°.
Prior to processing, CAD data of the implant with the desired configuration wasgenerated. In order to generate the CNC program for laser cutting, the coordinate pointsof the profile of the implant and its slots were imported from Pro/E. For the cuttingprocess, the SS-316LVM tube (outer diameter d=1.535 mm and thickness t=0.1 mm)was gripped in the laser machine with a single collate and supported by a bush insert.The width of implant slots was 0.06 mm and therefore the width of laser beam wasadjusted to the same value. The focal point of the beam was centered on the tube andverified by a charged coupled device (CCD) attached to the laser head. Straightness ofthe tube was also ensured using this CCD vision system by gradually turning and
FIG. 10. von-Mises stress distribution in splines.
linearly moving the tube. Optimized parameters used for laser cutting process of the316LVM tubes are illustrated in Table 1. The CNC program for the implant was loadedinto the software of the laser cutting machine. During operation of the machine, thelaser power and the chiller (cooling system for laser lamp) were switched on andoxygen gas with a pressure of 6–8 bars was pumped in from a cylinder. The CNCprogram was run and the implant was cut with an interpolation of rotary and linearmovement of the tubing relative to the laser. Fig. 11 illustrates the fabricated implanton the laser cutting machine. Fabricated implant was inspected and measured by videoinspection probe (Deltronic Inc.). The critical dimensions were compared with actualgeometry and reviewed. The profile of the implants wings was traced and thecoordinates of the measured points were exported from the video inspection probe tothe Pro/E for generation of the outer profile.
Bench testing The finalized design of the implant was evaluated a number oftimes (nN50) in the laboratory. The evaluations include deployments of the implant inair on the test bench and in vitro. The bench-top and in vitro testing were one of themain sources for design verification and developmental work. Bench-top airdeployments involved the manual deployments of the implants to validate the resultsof FEA simulations and evaluate the functionality and mechanical behaviour of theimplant. These deployments were done under microscope to examine the wingsformation and shape. The values of rotary displacement about the longitudinal axis andtranslatory displacements along the same axis, required for deployment of implant,were obtained from FEA simulations. These displacements were precisely applied tothe implant for a perfect deployment. Fig. 12 shows the isometric view of the implantwings deployed in air. Implant deployments were performed using a delivery actuatorattached to a guide wire and guide tube. This delivery actuator provided the entirerotary and translatory motions precisely in a particular sequence to deploy the implant.The forces involved during the deployment were also measured. The torque required toexpand the wing slots to the requisite out-of-plane displacement was measured by
TABLE 1. Laser cutting parameters.
Voltage (V) 220Frequency (Hz) 50Current (A) 15Average power (W) 50Pulse energy (mJ) 130Pulse frequency (Hz) 1000Pulse interval (ms) 11Pulse width (ms) 0.1Spot size of beam (micron) 6
FIG. 11. Implant fabricated on laser cutting machine. FIG. 13. Porcine tissue trapped in between implant wings.
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deploying the implant using a torque meter. Therefore, instead of the actuator, theguide wire was held in the torque meter and torque was applied on the implant using amanual handle. The peak value of the torque was recorded and then compared withpredicted values from FEA simulations. Finally, the compression force required to formthe wings was measured using a tensile testing machine (Lloyd Inc.). For thismeasurement, a semi deployed implant which was gone through slot expansion onlywas laser welded to two pins at both proximal and distal ends. These welded pins werethen clamped into the jaws of the tensile testing machine for application ofcompression force through the load cell. The compression force achieved during thisstudy was compared with the values of FEA simulations. In vitro bench testing (n=10)was carried out on both porcine tissue and fallopian tubes. These tests were performedto validate the deployment of the implant inside tissues against external loads, i.e. theloading exerted by tissue on the implant. An implant deployed into porcine tissue isshown in Fig. 13.
Explant studies In order to understand the limitations of the implant inconditions very similar to in vivo implementation, in vitro experiments were conductedusing explanted uteri. These uteri were removed at hysterectomy for various benignindications. Explanted uteri were chosen as the test model as this is mostrepresentative model of the in vivo situation. These in vitro deployments of theimplant into explanted human uteri were performed according to routine hospitalpolicy at the University Hospital, Mullingar, Ireland. These studies (n=5) wereperformed to validate the functionality, deliverability and effectiveness of the implantfor instant closure of human fallopian tubes. The implant was deployed bilaterally intothe tubal ostia. A small caliber hysteroscope with 5-French (F) operating channel wasused to deliver the implant into the ostium tissue. The hysteroscope was attached to alight source and camera to enable video recordings to be captured. The uterine cavitywas distended with normal saline to obtain a panoramic view. It was confirmed visuallythat the fallopian tubes were unobstructed as shown in Fig. 14. The hysteroscope wasintroduced under direct vision into the uterine cavity to locate the uterotubal ostia.Once located, the implant was introduced through the hysteroscope into the tubalostium and placed optimally. It was deployed using the delivery actuator. After
FIG. 12. Isometric view of in-air deployed implant.
deployment, the implant was detached from the guide wire and subsequently the guidetube. The procedure was repeated on the contra-lateral tube. After successfuldeployment of the implants in both tubes, hydraulic pressure test of the uterus wasperformed to validate the occlusion of fallopian tubes. In this test, saline solution andmethylene blue were introduced into the uterus at a pressure of 300 mm Hg. Thepressure was held for 5 minutes to ensure the blockage of the fallopian tubes. Finally,the ostium and tubes were dissected to examine the placement and deployment of theimplant in the intramural section of the ostium. The implant along with some tissuewas extracted to further examine the wing shape, deployed implant and tissue trapped.
RESULTS AND DISCUSSION
The paper presents design, development and testing of a novelimplant for transcervical sterilization using hysteroscopic delivery.The designing of implant, 3D modeling and FEA simulations wereperformed using CAD and FEA software. The 3D model generated inPro/E was integrated with ANSYS WB for FEA simulations. Thedeployment phases of implant were simulated using non-linearanalysis in ANSYS WB in order to deal with large deflections andplastic deformations. In order to generate the outer profile of implantwing, the nodal coordinates of deformed shape were exported fromANSYS WB using UPCOORD command. Following the UPCOORDcommand, CDWRITE was executed from the preprocessor to writeout a node file with the deformed nodal coordinates. These nodalcoordinates were imported into Pro/E to generate the outer profile ofthe wings.
The implant was fabricated using laser cutting machine. Pro/Emodel was used to generate CAD data required in generation of CNCprogram for laser cutting machine. Implant was inspected on videoinspection probe and critical dimensions showed that fabricated
FIG. 14. Explanted human uterus prior to implant deployment.
FIG. 15. Front view of deployed implant showing wings profile.
FIG. 17. Explanted human uterus under pressure testing following deployment.
248 REHAN ET AL. J. BIOSCI. BIOENG.,
implant was exact representative of CAD model having an accuracy ofless than 2.6 μm. The fabricated implant was deployed undermicroscope and its mechanical behavior was studied. Fig. 15 showsshape of implant wings deployed in air on test bench. The wing profileof these deployed implants was measured using video inspectionprobe. The coordinates obtained from the video inspection probewere imported into Pro/E and plotted. This experimentally measuredprofile of the wings was superimposed on the profile obtained fromFEA simulations, using Pro/E as shown in Fig. 16. It was observed withthis comparison that the FEA results are comparable with experi-mentation. The standard error of mean of the difference ofexperimental and simulated profile was 0.003543 and the maximumpercent error was 3.129%.
The forces required to deploy implants were validated experi-mentally on test bench. On application of 16.0 N-mm moment inANSYS WB simulations, a 0.353-mm out-of-plane displacement inimplant slots was obtained at the end of load set 1. A comparable 15.4N-mm was measured experimentally using torque meter when sameamount of radial expansion (from Ø1.535 mm to Ø2.241 mm) inimplant slots was achieved. In order to plastically deform theseexpanded implant slots, a force of 25.4 N was measured from tensiletesting machine which is comparable to a force of 25 N obtained fromthe FEA simulations. In-house in vitro and mechanical bench testingvalidated the mechanical behavior and functional aspects of the
FIG. 16. Comparison of FEA simulated and experimentally measured wings profile.
implant. In vitro testing of the implant in porcine tissues and fallopiantubes was successful. After dissection of tissues, it was found thattissue was trapped in between the wings. In vitro deployments of theimplant into human explanted uteri were performed. These studiesshowed that the implant deployed successful in the entire 5 explanteduteri. As expected, the implant had successfully occluded the fallopiantubes in all uteri. Immediately after the bilateral deployment ofimplant in the uteri, the hydraulic pressure tests using saline waterand methylene blue at pressure of 300 mm Hg were performed. It isapparent from Fig. 17 that there was no leakage during thesehydraulic pressure testing. These uteri were dissected after hydraulicpressure testing and the implant along with some tissue wasexamined under microscope to further investigate the implantwings shape, deployed implant and tissue trapped as shown in Fig.18. The blue colour of tissue indicates the presence of methylene blue.It can be seen from Fig. 18 that there is no indication of methyleneblue just after distal wings of the implant. This shows that the implantis capable of instantly occluding the fallopian tubes even at a pressureof 300 mm Hg.
The statistical methods used to analyze and report the results ofexplants studieswere statistical summaries of results and tabulation ofthe data. Each occlusion of fallopianwas treated as an individual eventrepresenting 0 or 1 for “no” or “yes” occlusion respectively. Bilateraldeployments of the implant were attempted in 5 explant studies.Successful instant occlusion was achieved in 10 of 10 (100%) fallopian
FIG. 18. Deployed implant within dissected human uterus.
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tubes. Since there were zero failures among 5 explanted uteri,statistical significance was not established because of zero numeratorproblems. However, these effective in vitro tests are important in thedevelopment of device as they provide clear indication of the device'scapabilities and weaknesses prior to commencing in vivo verificationand validation activities.
This study demonstrates that this novel implant is a new prospectfor transcervical sterilization, which uses inherent body channel anddoes not necessitate general anesthesia or incision in body. Contraryto current available devices of hysteroscopic sterilization, this implantprovides an immediate occlusion of the fallopian tubes. The implant'ssize and low profiled shape allows deploying it transcervically in thetubal ostia using a small caliber hysteroscope with a 5 F operatingchannel. Using these hysteroscopes can avoid cervical dilation thatallows the implant usage in clinical setup. The in vitro hydraulicpressure test using saline solution and methylene blue demonstratedan instant and total occlusion of the fallopian tubes. This study detailsthe design and development of implant using CAD, FEA simulationsand experimental testing. The bench and in vitro testing proved thatthe FEA simulations are ideally suited for evaluating the design andmechanical behavior of the implant. The results obtained using FEAsimulations agree reasonably well with the experimental results. Datagenerated from investigations in explanted uteri verified the efficacyof the implant as well as minimizing the risk to subjects participatingin in vivo clinical studies. Further development work is underway inpreparation for “first-in-man” clinical trials. As an overall conclusion,this implant is effective, consistent and feasible for hysteroscopicocclusion of fallopian tubes.
ACKNOWLEDGMENTS
The authors thank Vasorum /Alta Science team for their support.The authors thank Dr. Michael Gannon from the Midlands RegionalHospital, Mullingar, Ireland for the arrangement and performing in
vitro studies in human uteri. The authors also thank Enterprise Irelandfor the financial support for this project.
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