Urethra model

Abstract

The present disclosure provides a urethra model system for testing catheter insertion, comprising a tube formed from a polymer material and configured to replicate anatomical features of a human urethra, the tube having a curved geometry that simulates a prostatic urethra with a lumen extending therethrough, a support structure configured to secure the tube in a predetermined orientation, and at least one force sensor positioned to contact an exterior surface of the tube and configured to measure forces applied during catheter insertion testing. The polymer material may comprise gelatin, silicone, or a multi-layer structure having an inner core and an outer shell. The curved geometry may include a bend of approximately 30 degrees, and the lumen may have an inner diameter of 5-7 mm. The system may further include a dye incorporated into the tube to indicate locations of potential injury.

Description

Attorney Docket No. 3400-0384.01 (845PCT)URETHRA MODELCROSS-REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of and priority to U.S. Provisional Application No. 63 / 729,505, filed December 9, 2024, which is hereby incorporated by reference in its entirety.FIELD OF DISCLOSURE

[0001] The present disclosure relates to biomechanical testing models for medical devices, and more particularly to an anatomically accurate urethra model with sensing capabilities for testing intermittent catheters and analyzing catheter-tissue interactions during insertion procedures.BACKGROUND

[0002] Intermittent catheterization is a widely used procedure for voiding the bladder in patients with neurogenic bladder, post-surgical recovery, and chronic retention. Despite improvements in catheter materials and design, complications persist, including iatrogenic injury, urethral trauma, strictures, false passages, and urinary tract infections (UTIs).

[0003] Current understanding of the biomechanical mechanisms underlying these injuries is limited due to practical constraints of in vivo studies. Existing benchtop models lack anatomical fidelity, material relevance, and quantitative feedback necessary to simulate real-world catheter-tissue interactions.

[0004] Mechanical testing standards (e.g., ISO 10555) focus on catheter properties but do not replicate the anatomical and material complexities of the urethra. Existing models, including hard rubber, ex vivo porcine tissue, and commercial anatomical trainers, fail to mimic the compliance, curvature, and frictional properties of human urethral mucosa while providing quantitative feedback on force application and tissue response.

[0005] Clinical and industry experts have identified the need for a model that: (1 ) accurately replicates anatomical features of the human urethra; (2) mimics the mechanical properties of urethral tissue; and (3) provides real-time feedback onAttorney Docket No. 3400-0384.01 (845PCT) force application to enable study of catheter-tissue interactions and injury mechanisms.

[0006] Therefore, a need exists for a biomechanical model that simulates urethral conditions during repeated catheter use and detects associated urethral traumas to better understand injury mechanisms.SUMMARY OF THE INVENTION

[0007] According to an aspect of the present disclosure, a urethra model system for testing catheter insertion is provided. The urethra model system comprises a tube formed from a polymer material and having a lumen extending therethrough. The tube is configured to replicate anatomical features of a human urethra. The urethra model system comprises a support structure configured to secure the tube in a predetermined orientation. The urethra model system comprises at least one force sensor configured to measure forces applied to the tube during catheter insertion testing.

[0008] According to other aspects of the present disclosure, the urethra model system may include one or more of the following features. The tube may have a curved or straight geometry. The polymer material may comprise gelatin. The gelatin may have a bloom strength ranging from 30 to 325. The polymer material may comprise one or more of collagen, alginate, agarose, chitosan, glycosaminoglycans (GAGs), cellulose, or sugars, or synthetic polymers such as silicone, styrenic block copolymers, polyurethane, methacrylate (e.g. Poly(2- hydroxyethyl methacrylate, PHEMA), polyacryates, or similar, or hybrid combinations of natural and synthetic polymers. The tube may comprise a multilayer structure having an inner core and an outer shell. The inner core may comprise gelatin and glycosaminoglycans, and the outer shell may comprise silicone. The curved geometry may include a bend of approximately 30 degrees to simulate the prostatic urethra. The lumen may have an inner diameter of 5-7 mm. The urethra model system may further comprise a dye incorporated into the tube to indicate locations of potential injury during catheter insertion. The dye may be a mechano-sensitive dye that changes color in response to applied force. The at least one force sensor may be configured to detect forces exceeding 5 Newtons. TheAttorney Docket No. 3400-0384.01 (845PCT) support structure may include a plurality of tube holders. Positions of the tube holders may be adjustable. The urethra model system may further include a stricture in the tube. The stricture may be formed by the support pinching the tube.

[0009] According to another aspect of the present disclosure, a method of testing catheter insertion forces is provided. The method comprises providing a model urethra comprising a polymer tube that replicates a urethra. The method comprises positioning at least one force sensor in contact with the polymer tube. The method comprises inserting a catheter through a lumen of the polymer tube. The method comprises measuring forces applied to the polymer tube during the catheter insertion using the at least one force sensor.

[0010] According to other aspects of the present disclosure, the method may include one or more of the following features. The tube may have a curved or straight geometry. The polymer tube may comprise gelatin. The gelatin may have a bloom strength ranging from 30 to 325. The polymer tube may comprise one or more of collagen, alginate, agarose, chitosan, glycosaminoglycans (GAGs), cellulose, or sugars, or synthetic polymers such as silicone, styrenic block copolymers, polyurethane, methacrylate (e.g. Poly(2-hydroxyethyl methacrylate, PHEMA), polyacryates, or similar, or hybrid combinations of natural and synthetic polymers. The tube may comprise a multi-layer structure having an inner core and an outer shell. The inner core may comprise gelatin and glycosaminoglycans, and the outer shell may comprise silicone. The curved geometry may include a bend of approximately 30 degrees. The method may further comprise a step of detecting when the measured forces exceed 5 Newtons. The method may further comprise a step of analyzing the measured forces to identify locations of potential urethral trauma.

[0011] According to another aspect of the present disclosure, a mold for fabricating a model urethra is provided. The mold comprises a mold first half and a mold second half that together define a mold cavity when assembled. The mold cavity is configured to form a curved tubular structure. The mold comprises a core pin configured to extend through the mold cavity to define an internal lumen in the tubular structure.Attorney Docket No. 3400-0384.01 (845PCT)

[0012] According to other aspects of the present disclosure, the mold may include the following feature. The core pin may have a curved configuration that includes a bend of approximately 30 degrees to replicate the anatomical curvature of a prostatic urethra.BRIEF DESCRIPTION OF THE FIGURES

[0013] FIG. 1 is a perspective view of a urethra model with a support structure, according to aspects of the present disclosure.

[0014] FIG. 2 is a perspective view of the urethra model of FIG. 1 , according to aspects of the present disclosure.

[0015] FIG. 3 is a top view of three tubes arranged in parallel, according to aspects of the present disclosure.

[0016] FIG. 4 is an exploded perspective view of a mold for fabricating a model urethra, according to aspects of the present disclosure.

[0017] Fig. 5 illustrates a graph showing stress-strain relationships for different gelatin-glycerol-water ratios, according to aspects of the present disclosure.

[0018] FIG. 6 illustrates a sensor with attached wiring, according to aspects of the present disclosure.

[0019] FIG. 7 is a perspective view of a urethra model with a cross-sectional detail, according to aspects of the present disclosure.DESCRIPTION

[0020] The present disclosure provides a biomechanical urethra model system designed to replicate the anatomical and mechanical properties of human urethral tissue for testing intermittent catheters and analyzing catheter-tissue interactions. The model system comprises three integrated subsystems that work together to provide anatomical accuracy, mechanical relevance, cost-effectiveness, and ease of maintenance. These subsystems include a tube that mimics the geometry and material properties of native tissue, sensing components that detect and quantify mechanical and physical interactions during catheter insertion, and a structural support framework that maintains proper positioning and orientation of the tubeAttorney Docket No. 3400-0384.01 (845PCT) during testing procedures. Each subsystem may be fabricated using various manufacturing techniques, including three-dimensional printing, molding, casting, or other suitable fabrication methods.

[0021] Referring to FIGS. 1 and 2, a urethra model 100 may be provided for testing catheter insertion. The urethra model 100 may comprise a tube 102 formed from a polymer material, such as gelatin, and configured to replicate anatomical features of a human urethra. The tube 102 may have a curved geometry that simulates a prostatic urethra with a lumen extending therethrough. In some cases, the curved geometry may include a bend of approximately 30 degrees to simulate the prostatic urethra. The tube 102 may have any desired length. In one alternative, tube 120 has a length greater than 20 cm to replicate the full length of the male urethra. The tube 102 has an inlet opening 102a and an outlet opening 102b. A catheter is inserted into the inlet opening 102a of tube 102 and is advanced through the lumen of the tube 102.

[0022] The urethra model 100 may further comprise a support 104 configured to secure the tube 102 in a predetermined orientation. The support 104 may include a vertical support 106 and a base 108. The vertical support 106 may feature a perforated surface with multiple mounting holes arranged in a grid pattern, providing adjustable attachment points for various components, such as a peg board. The base 108 may provide a stable foundation for the assembly and may include recessed channels and mounting features.

[0023] A tube support 1 10 may be attached to the vertical support 106. Multiple tube holders 112 may be positioned along the tube support 1 10 to secure and maintain the tube 102 in a proper anatomical or any other desired orientation. The tube holders 1 12 may be attached to a rail 1 14 extending along the tube support 110. The rail 114 may provide a mounting track for positioning the adjustable and repositionable tube holders 1 12. The tube holders 112 may be positioned and / or repositioned as desired.

[0024] Each tube holder 1 12, optionally, may include a rod 116 that may be attached to the rail 1 14. The tube holders 112 may be adjustable clamps that have clamping or gripping structures to hold or grip the tube. In the illustrated embodiment, theAttorney Docket No. 3400-0384.01 (845PCT) tube holder includes clamp screws 1 18, enabling secure and adjustable attachment of the tube 102 to the tube holders 112. The clamp screws 1 18 may allow for adjustment and positioning of the tube 102 within the tube holders 1 12.

[0025] The urethra model 100 may include at least one sensor 134, which may be force sensors, pressure sensors, strain sensors, displacement sensors, temperature sensors, friction sensors, or combinations thereof to measure various characteristics during catheter insertion including applied forces, internal pressure changes, material deformation, catheter displacement, thermal effects from friction, and surface friction coefficients. In one alternative, the urethra model 100 may include a force sensing system, which allows for real-time measurement of the forces exerted on the urethra during catheter insertion. This sensing system may help understand how different catheter designs affect the risk of iatrogenic injury. In one embodiment, at least one sensor(s) 134 is / are integrated at desired points along the model, which may be what are considered critical points, for example, at the bend of the prostatic urethra. The sensors 134 may be secured to the tube support 110 and may be configured to detect and measure characteristics, such as forces exerted on the tube 102 during catheter insertion procedures. An example of a force sensor 134 is shown in Fig. 6, the force sensor 134 may include wires may extend from each sensor 134 to provide electrical connections for data transmission to a data acquisition system or the force sensor 134 may be wireless and wireless transmit data to the data acquisition system. For example, the sensors 134 may collect data using Arduino software for real-time measurement during catheter insertion. The Arduino-based data acquisition system may process the electrical signals from the sensors and convert the signals into force measurements that can be monitored and recorded during testing procedures. The real-time data collection capability may allow for immediate feedback regarding the forces being applied to the urethra model 100 system during catheter insertion.

[0026] When at least one force sensor is used, the sensors allow localization and quantification of the force applied during catheter insertion and assess if the forces exceed the injury threshold of 5 N. In one alternative, the sensors make contact with the exterior of the molded model urethra and permit force data to be collected by a processor / software, such as Arduino software or any other suitable processorAttorney Docket No. 3400-0384.01 (845PCT) and / or software. The data may be used to evaluate whether different catheters generate forces within 5 Newtons to prevent iatrogenic injuries that commonly occur at forces outside this range. The force sensors may be any suitable force sensors and may vary in flexibility, depending on the model. Additionally, the force sensors may be associated with the tube in any suitable manner. For example, the force sensors may be embedded in the tube wall or may be on the inner surface of the tube wall.

[0027] During use of the model, measured forces may be analyzed to identify locations of potential urethral trauma. The force analysis may involve examining the spatial distribution of forces along the length of the model urethra to determine specific regions where excessive forces are being applied. This analysis may help identify anatomical locations that are susceptible or most susceptible to injury during catheter insertion procedures, enabling targeted improvements in catheter design or insertion techniques.

[0028] The urethra model 100 may be designed to be reusable with only the tubing 102 requiring replacement while maintaining the same base, sensors, and structure. This replaceable design may provide cost-effectiveness and ease of maintenance for repeated testing procedures. The modular approach may allow for the tubes 102 to be replaced periodically while preserving the supporting infrastructure and measurement systems for continued use in catheter insertion testing applications.

[0029] The urethra model 100 may serve multiple stakeholders in different capacities. Engineers may use the model for catheter testing to evaluate catheter designs and measure insertion forces. Physicians may use the model for training purposes to practice catheter insertion techniques. Patients may use the model for education and practice to familiarize themselves with catheter insertion procedures before performing self-catheterization.

[0030] Referring to FIG. 2, a compartment 120 may be positioned on base 108, providing an enclosure for housing electronic components, data acquisition systems, or other supporting equipment. The compartment 120 may accommodate various electronic interfaces configured for sensor data collection and processing.Attorney Docket No. 3400-0384.01 (845PCT)

[0031] Referring to FIG. 3, three tubes 102 are arranged in parallel, illustrating the different length of tubes that may be form. For example, the tube length and diameter may be made for a male urethra, female urethra, or a juvenile urethra. The tubes 102 may replicate one or more of the stiffness, curvature, and diameter of the human urethra. In one alternative, tube 102 may replicate the biological region of the prostatic urethra, which is a site where the risk of mechanical injury occurs during catheter insertion.

[0032] The tubes may be made from natural polymers such as gelatin, collagen, alginate, agarose, chitosan, glycosaminoglycans (GAGs), cellulose, or sugars, or synthetic polymers such as silicone, styrenic block copolymers, polyurethane, methacrylate (e.g. Poly(2-hydroxyethyl methacrylate, PHEMA), polyacryates, or similar, or hybrid combinations of natural and synthetic polymers, which offer the flexibility and softness that simulates the urethra's mechanical properties.

[0033] Another example of a hybrid combination model could use gelatin, glycosaminoglycans (GAGs) internally, and silicone externally to mimic the friction and stiffness properties of the urethra, or the anatomical regions of the urethral wall structure (inner mucosal layer, stratified squamous or transitional epithelial layer, submucosal layer, and outer muscular layer).

[0034] In one alternative, the polymer material may comprise gelatin, which offers flexibility and softness that simulates the mechanical properties of urethral tissue. The stiffness of the polymer is adjustable, for example in the case of gelatin by varying its bloom strength of the gelatin, ranging from 30 to 325, allowing the creation of a simulation of the urethra's mechanical behavior at different stiffness levels of stiffness. Bloom strength refers to the force, expressed in grams, to depress the surface of a gelatin gel by 4mm with a standard 0.5" diameter cylinder probe, and the larger the value, the stronger the gelatin is. The gelatin mixture may be composed of gelatin powder, glycerol, and water in various ratios to achieve different stiffness levels. In some cases, a 1 :2:8 ratio of gelatin, glycerol, and water may be used, where the Bloom strength of the gelatin may be 300 according to the manufacturer specifications.Attorney Docket No. 3400-0384.01 (845PCT)

[0035] The tubes 102 may exhibit a translucent or semi-transparent appearance with a yellowish or cream coloration that may be characteristic of the gelatin composition. Dye may be added to indicate the location of injury or damage that could lead to injury during the modeled catheter insertion event(s).

[0036] The natural, synthetic or hybrid polymer may be selected for its costeffectiveness, ease of use, and ability to be molded into cylindrical shapes matching the inner diameter of the human urethra of 5-7 mm. Polymer selection may also be made based on the desired properties of the urethra to be incorporated. For example, the addition of GAGs to the inner lumen of a gelatin tube may be selected to mimic the lubricity of the mucous and mucosal layer of the urethra. In another example, a silicone outer layer may be added to surround the gelatin tube to better mimic the compliance and biomechanics of the urethra in vivo and in situ, where it is encased within the muscular and fibrous tissue of the penis, pelvis or prostate, depending on the anatomical section being modeled.

[0037] In another example using synthetic polymer silicone, the stiffness of the silicone tube model may be altered to mimic the various regions of the urethra by modulating the ratio of the components and the curing conditions. For example, the silicone mixture may be made up of a two-part platinum-cure silicone elastomer (such as EcoFlex 00-30 or Dragon Skin), with optional additives such as silicone oil or fumed silica to adjust mechanical properties.

[0038] In one alternative, the mixture included a 1 :1 ratio by weight of Part A and Part B silicone base. The stiffness of the cured silicone may be varied by adjusting the proportion of silicone oil (softener) or fumed silica (stiffener) added to the base mixture. Increasing the amount of silicone oil will decrease the material's stiffness, resulting in a softer tube, while increasing the amount of fumed silica will increase the stiffness, resulting in a firmer tube.

[0039] To prepare the silicone mixture, amounts of Part A and Part B are weighed. In one example, 50 grams of Part A and 50 grams of Part B may be combined in a mixing vessel. To decrease stiffness, 10 grams of silicone oil may be added to the mixture and thoroughly stirred until homogeneous. To increase stiffness, 5 gramsAttorney Docket No. 3400-0384.01 (845PCT) of fumed silica may be added and mixed until fully dispersed. The mixture may then be degassed under vacuum to remove air bubbles.

[0040] Once the combination is mixed thoroughly, it may be poured into a cylindrical mold with a 6 mm diameter rod to form the lumen. The mold may then be allowed to cure at room temperature for 4 hours or longer, after which the silicone tube may be removed. The tube may be left on the rod for an additional 24 hours to ensure complete curing and dimensional stability.

[0041] The shore hardness of the resulting silicone tube may be measured using a durometer. The ratio of silicone oil or fumed silica may then be adjusted to create a silicone tube with the same shore hardness as the target biological tissue (e.g., porcine urethra, human urethra, or male prostatic urethra). This process allows for precise tuning of the mechanical properties to match the anatomical region of interest.

[0042] In another example, to replicate the mechanical and biological properties of the urethra for benchtop testing and simulation, a composite model comprising three distinct layers could be constructed, including 1 ) A gelatin core, serving as the primary moldable matrix and mimicking the bulk mechanical properties and flexibility of native urethral tissue, 2) Glycosaminoglycans (GAGs), incorporated within the gelatin to simulate the hydrated, viscoelastic extracellular matrix found in native tissue, enhancing biological relevance and moisture retention, and 3) A silicone outer shell, providing structural support, durability, and a realistic tactile interface for repeated handling and instrumentation.

[0043] An example of a construction approach could include using a 3D-printed mold or mold fabricated by other means to define the anatomical curvature and diameter of the urethra. Gelatin is dissolved in heated water, and GAGs are added at a concentration optimized for viscoelasticity and hydration. The mixture is poured into the mold and allowed to set, forming the inner core. Once the gelatin-GAG core is cured, it is encapsulated within a layer of medical-grade silicone, either by dipcoating or casting. The silicone shell is cured to form a flexible, protective outer layer.Attorney Docket No. 3400-0384.01 (845PCT)

[0044] Potential advantages of this or a similar combination model include biological relevance (the gelatin-GAG core closely mimics the hydrated, viscoelastic nature of urethral tissue), mechanical fidelity (tunable stiffness and elasticity allow for accurate simulation of tissue response to catheterization), durability (the silicone shell protects the model from dehydration and mechanical wear, enabling repeated use), and modularity (the inner core can be replaced or modified independently of the outer shell, facilitating iterative testing and customization).

[0045] Dye may be added to indicate the location of injury or damage that could lead to injury in the modeled catheter insertion. Movement of the dye into the wall of the tube or into non-dyed layers may indicate the site of the frictional or penetrating injury. For example, dyes such as methylene blue, sirius red, picrosirius red, aniline blue, or fast green may be added to the lumen of a gelatin or collagen tube. In another example, alcian blue, safranin-O, toluidine blue, or periodic acid- Schiff (PAS) dyes may be added to a GAG luminal layer of a multi-laminated model. Alternatively, the model may include a color-changing dye (e.g., mechano-sensitive dyes) that allows visualization of where the most force is being applied within the urethra. Examples of mechano-sensitive dyes include pressure sensitive paints with Ruthenium chromophores and mechanochromic dyes such as spiropyrans, diarylethenes, and Rhodamine- or DABCO-based dyes.

[0046] Referring to FIG. 5, a graph illustrates the stress-strain relationships for different gelatin-glycerol-water ratios used in forming the tube. The graph displays three distinct curves representing different composition ratios: 1 :2:8, 1 :2:4, and 1 :2:2 (gelatin:glycerol:water). The x-axis represents strain values ranging from 0 to 4, while the y-axis represents stress values ranging from 0 to 1 MPa. The elastic modulus may be calculated from the slope of each curve, where a steeper slope indicates higher stiffness of the gelatin material.

[0047] As shown in FIG. 5, the gelatin stiffness may be adjusted by varying the water component ratio, where increasing water content increases material stiffness due to dehydration effects. The 1 :2:8 ratio curve exhibits the highest stress values across the strain range, reaching approximately 1 .0 MPa at a strain of 4, while the 1 :2:4 ratio curve demonstrates intermediate stress values, reaching approximatelyAttorney Docket No. 3400-0384.01 (845PCT)0.64 MPa at the same strain level. The 1 :2:2 ratio curve shows the lowest stress values, reaching approximately 0.55 MPa at a strain of 4. The linear relationship between stress and strain for each curve demonstrates that the mechanical properties of the gelatin material may be predictably controlled through compositional adjustments.

[0048] Referring to FIG. 4, a urethra mold 122 for fabricating a model urethra is shown in an exploded isometric view. The urethra mold 122 may be machined, cast or 3D-printed, to encase a polymer during the formation of a tube 102.

[0049] The mold 122 may comprise a mold first half 124 and a mold second half 126 that together define a mold cavity 128 when assembled. The mold cavity 128 may be configured to form a curved tubular structure that replicates the anatomical features of a human urethra.

[0050] The mold first half 124 and the mold second half 126 may include complementary mating surfaces with grooves on the face of each half where the halves are connected. These grooves may enable separation of the mold first half 124 and the mold second half 126 after a casting material has solidified within the mold cavity 128. The grooves may provide alignment features that facilitate proper assembly of the mold 122 while allowing for controlled disassembly once the gelatin or other polymer material has cured.

[0051] A core pin 130 may be configured to extend through the mold cavity 128 to define an internal lumen in the tube or tubular structure. The core pin 130 may have a curved configuration that includes a bend of approximately 30 degrees to replicate the anatomical curvature of a prostatic urethra. In some cases, the core pin 130 may have a 6 mm diameter and may include the 30-degree curve to mold the polymer into the proper prostatic urethra shape. The core pin 130 may maintain the internal geometry of the model urethra during the casting process, so that the resulting tubular structure includes a properly dimensioned lumen for catheter insertion testing.

[0052] In another example, the mold may be straight or incorporate more acute angles than 30 degrees to mimic other regions of the male urethra (the spongy, or penile, urethra, the membranous urethra, and the pre-prostatic urethra). In anotherAttorney Docket No. 3400-0384.01 (845PCT) example, the mold can be fabricated to produce a tube that models the female urethra, or specific regions along the length of the female urethra. Additionally, the stiffness of the tube 102 may be altered to mimic the various regions of the urethra by modulating the ratio of the components.

[0053] As further shown in FIG. 4, legs 132 may extend from the mold first half 124 to support the mold 122 during a curing process. The legs 132 may provide a stable base for the mold 122 to stand on during the curing process, elevating the mold 122 above a supporting surface. The legs 132 may allow gravity to assist in keeping the casting material contained within the mold cavity 128 while the material solidifies. In some cases, the mold 122 may include four legs 132 extending from the bottom surface of the mold first half 124 to provide stable support during the fabrication process.

[0054] In one alternative of making a tube 102, a mixture included a 1 :2:8 ratio of gelatin, glycerol, and water, respectively. Water is boiled, and in one example, 4 grams of gelatin powder and 8 grams of glycerol are gradually added water to the mixture in 4-gram increments while stirring. The water remained boiling while the gelatin and glycerol were added, and the mixture was completely mixed with no particles floating. The process was repeated until 32 grams were added. Once the mixture was thoroughly mixed, the mixture was poured into the mold. The mold sat for 4 hours before removing the gelatin mixture. The gelatin mixture was left on the 6 mm rod for a couple of days to let the mixture set before removing the rod. This allowed the mixture to set and to give time for dehydration and subsequent shrinkage.

[0055] In an example, the shore hardness of the porcine urethra was measured, and the above ratio was altered to create a gelatin urethra with the same shore hardness. In another example, the shore hardness of the urethra.

[0056] Referring to FIG. 7, a urethra model 200 may be configured to replicate anatomical features of a human urethra with varying structural detail. The urethra model 200 may include a tube 202 that represents the anatomical structure of the urethra, configured with a curved geometry to simulate the natural curvature found in the prostatic region. The tube 202 may be secured to a support 204 through aAttorney Docket No. 3400-0384.01 (845PCT) tube holder 206, which maintains the tube 202 in a predetermined anatomical orientation for testing procedures.

[0057] A projection 208 may extend into the channel of the tube holder 206, providing a constricted area of the channel. As further shown in FIG. 7, an inset detail view reveals a cross-sectional representation of the tube 202 in the constricted area of the channel of the tube holder 206. The projection 208 squeezes or pinches the tube 202 to mimic a stricture 210 of a urethra, e.g., a narrowing of the urethral passage, simulating a pathological condition where scar tissue or fibrotic tissue deposition causes constriction of the urethra. This could also mimic a false passage in the urethra.

[0058] In another alternative, a urethra model could include a 3D-printed tube representing a selected section of the male urethra, for example, the prostatic urethra. The 3D-printed tube may be mounted on a support, similar to support 104 and / or tube support 1 10, which holds the tube in place. A multitude of load cells may be placed along the outer surface of the tube. These load cells record the force exerted by the catheter on the tube wall as it travels through it. The force exerted by the catheter is indicative of the trauma it would cause to the urethral wall and is largely dependent on the geometrical attributes of the catheter. The data acquisition and processing are performed by an onboard microcontroller and is communicated to an external device, such as a laptop or desktop, through terminal software.

Claims

Attorney Docket No. 3400-0384.01 (845PCT)We Claim:1 . A urethra model system for testing catheter insertion, comprising: a tube formed from a polymer material and having a lumen extending therethrough, the tube configured to replicate anatomical features of a human urethra; a support structure configured to secure the tube in a predetermined orientation; and at least one force sensor configured to measure forces applied to the tube during catheter insertion testing.

2. The urethra model system of claim 1 , wherein the tube has a curved or straight geometry.

3. The urethra model system of any one of claims 1 and 2, wherein the polymer material comprises gelatin.

4. The urethra model system of claim 3, wherein the gelatin has a bloom strength ranging from 30 to 325.

5. The urethra model system of any one of claims 1 -4, wherein the polymer material comprises one or more of collagen, alginate, agarose, chitosan, glycosaminoglycans (GAGs), cellulose, or sugars, or synthetic polymers such as silicone, styrenic block copolymers, polyurethane, methacrylate (e.g. Poly(2- hydroxyethyl methacrylate, PHEMA), polyacryates, or similar, or hybrid combinations of natural and synthetic polymers.

6. The urethra model system of any one of claims 1 -5, wherein the tube comprises a multi-layer structure having an inner core and an outer shell.

7. The urethra model system of claim 6, wherein the inner core comprises gelatin and glycosaminoglycans, and the outer shell comprises silicone.

8. The urethra model system of any one of claims 1 -7, wherein the tube has a curved geometry that includes a bend of approximately 30 degrees to simulate a prostatic urethra.Attorney Docket No. 3400-0384.01 (845PCT)9. The urethra model system of any one of claims 1 -8, wherein the lumen has an inner diameter of 5-7 mm.

10. The urethra model system of any one of claims 1 -9, further comprising a dye incorporated into the tube to indicate locations of potential injury during catheter insertion.11 . The urethra model system of claim 10, wherein the dye is a mechanosensitive dye that changes color in response to applied force.

12. The urethra model system of claims 1 -11 , wherein the at least one force sensor is configured to detect forces exceeding 5 Newtons.

13. The urethra model system of claims 1 -12, wherein the support structure includes a plurality of tube holders.

14. The urethra model system of claim 13, wherein positions of the tube holders are adjustable.

15. The urethra model system of any one of claims 1-14, further including a stricture in the tube.

16. The urethra model system of claim 15, wherein the stricture is formed by the support pinching the tube.

17. A method of testing catheter insertion forces, comprising: providing a model urethra comprising a polymer tube that replicates a urethra; positioning at least one force sensor in contact with the polymer tube; inserting a catheter through a lumen of the polymer tube; and measuring forces applied to the polymer tube during the catheter insertion using the at least one force sensor.

18. The method of claim 17, wherein the tube has a curved or straight geometry.

19. The method of claim 18, wherein the polymer tube comprises gelatin.Attorney Docket No. 3400-0384.01 (845PCT)20. The method of claim 19, wherein the gelatin has a bloom strength ranging from 30 to 325.

21. The method of any one of claims 17-20, wherein the polymer tube comprises one or more of collagen, alginate, agarose, chitosan, glycosaminoglycans (GAGs), cellulose, or sugars, or synthetic polymers such as silicone, styrenic block copolymers, polyurethane, methacrylate (e.g. Poly(2- hydroxyethyl methacrylate, PHEMA), polyacryates, or similar, or hybrid combinations of natural and synthetic polymers.

22. The method of any one of claims 17-21 , wherein the tube comprises a multi-layer structure having an inner core and an outer shell.

23. The method of claim 22, wherein the inner core comprises gelatin and glycosaminoglycans, and the outer shell comprises silicone.

24. The method of any one of claims 17-23, wherein the tube has a curved geometry that includes a bend of approximately 30 degrees.

25. The method of any one of claims 17-24, further comprising a step of detecting when the measured forces exceed 5 Newtons.

26. The method of any one of claims 17-25, further comprising a step of analyzing the measured forces to identify locations of potential urethral trauma.

27. A mold for fabricating a model urethra, comprising: a mold first half and a mold second half that together define a mold cavity when assembled, the mold cavity configured to form a curved tubular structure; a core pin configured to extend through the mold cavity to define an internal lumen in the tubular structure.

28. The mold of claim 27, wherein the core pin has a curved configuration that includes a bend of approximately 30 degrees to replicate an anatomical curvature of a prostatic urethra.

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