Abstract: An annuloplasty band and method of implantation. The band is shaped and sized to avoid the adjacent aortic valve structure and better protects against dehiscence along the muscular mitral annulus. The band is asymmetric and when implanted spans more around the side of the mitral annulus having the posterior commissure than the side with the anterior commissure. The band has a saddle shape with a posterior upward bow centered on a minor axis of the mitral annulus, and a span extending clockwise therefrom is longer than a span extending counter-clockwise. The longer span may be 150° while the shorter span extends 90°. A set of rings may have different saddle profiles and different plan view shapes for different sized bands. A method includes implanting so that the band extends over the posterior leaflet and a short distance past the posterior commissure outside of the anterior leaflet.

Abstract: A radiopaque nitinol stent for implantation in a body lumen is disclosed. The stent is made from a superelastic alloy such as nickel-titanium or nitinol, and includes a ternary element including tungsten. The added tungsten in specified amounts improve the radiopacity of the nitinol stent comparable to that of a stainless steel stent of the same strut pattern coated with a thin layer of gold. Furthermore, the nitinol stent has improved radiopacity yet retains its superelastic and shape memory behavior and further maintains a thin strut/wall thickness for high flexibility.

Abstract: The use of nucleating agents to manufacture polymeric stents is disclosed. The resulting stents may have increased crystallinity, decreased crystal size, increased mechanical properties, and faster degradation times.

Abstract: An endo luminal support structure (10) includes strut members (11) interconnected by swivel joints (15) to form a series of linked scissor mechanisms. The structure can be remotely actuated to compress or expand its shape by adjusting the scissor joints within a range of motion. In particular, the support structure can be repositioned within the body lumen or retrieved from the lumen. The support structure can be employed to introduce and support a prosthetic valve (100) within a body lumen.

Abstract: A medical device, for example a stent, has a surface which in use contacts body tissue, wherein said surface has on it a biocompatible coating layer comprising a polymer having covalently bound allyl-terminated pendent groups, said pendent groups comprising a moiety selected from -0-CH2—CH?CH2—S—CH2—CH?CH2—S(=0)-CH2—CH?CH2—Se—CH2—CH?CH2 and —Se (=0 J-CH2—CH?CH2. This surface has good biocompatibility and can bind strongly to a metallic surface. The polymer may be made from an electropolymerisable monomer, e.g. a pyrrole.

Abstract: A device for heart valve repair including at least one tension member having a first end and second end. A basal anchor is disposed at the first end of the tension member and a secondary anchor at the second end. The method includes the steps of anchoring the basal anchor proximate a heart valve and anchoring the secondary anchor at a location spaced from the valve such that the chamber geometry is altered to reduce heart wall tension and/or stress on the valve leaflets.

Abstract: The invention concerns methods of coating stents and stents produced in accordance therewith. The object of the invention is to provide methods of coating stents with a polysaccharide layer which has improved adhesion capacity on the substrate surface of the implant, and to afford correspondingly functionalized stents. That is achieved inter alia by covalent bonding of a non-crosslinked hyaluronic acid to a substrate surface of the stent with the formation of hyaluronic acid layer and crosslinking of the hyaluronic acid layer.

Abstract: An image is captured or otherwise converted into a signal in an artificial vision system. The signal is transmitted to the retina utilizing an implant. The implant consists of a polymer substrate made of a compliant material such as poly(dimethylsiloxane) or PDMS. The polymer substrate is conformable to the shape of the retina. Electrodes and conductive leads are embedded in the polymer substrate. The conductive leads and the electrodes transmit the signal representing the image to the cells in the retina. The signal representing the image stimulates cells in the retina.

Abstract: A one step method for drug coating an interventional device is disclosed by mixing a drug with a phosphorylcholine-linked methacrylate polymer in a liquid and applying the mixture to an interventional device, such as a stent, in a single step.

Abstract: Devices for assessing the size, shape, and topography of vessel lumens and hollow portions of organs are described. The devices are particularly adapted for determining the size, shape, topography, and compliance of the native heart valves to facilitate the later implantation of a prosthetic heart valve. The devices are typically catheter-based having an assessment mechanism fixed to a distal end of the catheter. The assessment mechanism generally includes an expandable member, such as a balloon. The assessment mechanism may also include an imaging member, a physical assessment member, an electronic mapping construction, an alignment mechanism, a valvuloplasty balloon, or any combination thereof.

Abstract: A system for coating a stent includes a device for weighing a stent, a device for aligning the stent with a stent support, a device for coating the stent, a device for drying the stent, and a device for inspecting the stent.

Abstract: A thin-wall PTFE (polytetrafluoroethylene) tube in the form of a tube of porous expanded PTFE film wherein the porous PTFE film has a microstructure containing a multiplicity of fibrils oriented substantially parallel to each other. The tube has a wall thickness of less than about 0.25 mm and is made from at least one first layer and at least one second layer of porous PTFE film, wherein the fibrils of the first and second layers are oriented substantially perpendicular to each other. Preferably the fibrils of the at least one first layer are oriented substantially parallel to the longitudinal axis of the tube and the fibrils of the at least one second layer of porous PTFE film are oriented substantially circumferential to the tube. The first and second layers may be inner and outer layers respectively, or alternatively their relationship may be reversed.

Abstract: A prosthetic valve for implantation in a stenosed aortic valve. The prosthetic valve includes a compressible and expandable frame formed with intersecting metallic bars and a valvular structure made with pericardial tissue. The frame is compressible for delivery into a patient's vasculature through an 18 F (5.7 mm) arterial introducer using a catheterization technique. The bars of the frame preferably have a diameter in the range of 0.1 to 0.6 mm for providing the frame with sufficient radial strength to resist the recoil force exerted by the stenosed aortic valve after implantation. The prosthetic valve includes an internal cover made with pericardial tissue. The internal cover is fastened to an internal surface of the frame between an inlet end of the frame and the valvular structure for preventing regurgitation.

Abstract: A heart valve prosthesis is provided having a self-expanding multi-level frame that supports a valve body comprising a skirt and plurality of coapting leaflets. The frame transitions between a contracted delivery configuration that enables percutaneous transluminal delivery, and an expanded deployed configuration having an asymmetric hourglass shape. The valve body skirt and leaflets are constructed so that the center of coaptation may be selected to reduce horizontal forces applied to the commissures of the valve, and to efficiently distribute and transmit forces along the leaflets and to the frame. Alternatively, the valve body may be used as a surgically implantable replacement valve prosthesis.

Abstract: A valve prosthesis which is especially useful in the case of aortic stenosis and capable of resisting the powerful recoil force and to stand the forceful balloon inflation performed to deploy the valve and to embed it in the stenotic aortic annulus, comprises a collapsible valvular structure and an expandable frame on which said valvular structure is mounted. The valvular structure is composed of physiologically compatible valvular tissue that is sufficiently supple and resistant to allow the valvular structure to be deformed from a closed state to an opened state. The valvular tissue forms a continuous surface. The valve prosthesis can be delivered percutaneously, surgically, or endoscopically.

Abstract: A cardiac valve prosthesis having a frame and two or more leaflets (preferably three) attached to the frame. The leaflets are attached to the frame between posts, with a free edge which can seal the leaflets together when the valve is closed under back pressure. The leaflets are created in a mathematically defined shape allowing good wash-out of the whole leaflet orifice, including the area close to the frame posts, thereby relieving the problem of thrombus deposition under clinical implant conditions.

Abstract: An image is captured or otherwise converted into a signal in an artificial vision system. The signal is transmitted to the retina utilizing an implant. The implant consists of a polymer substrate made of a compliant material such as poly(dimethylsiloxane) or PDMS. The polymer substrate is conformable to the shape of the retina. Electrodes and conductive leads are embedded in the polymer substrate. The conductive leads and the electrodes transmit the signal representing the image to the cells in the retina. The signal representing the image stimulates cells in the retina.

Abstract: Provided herein is a PEA polymer blend and coatings or implantable devices formed therefrom.

Abstract: The present invention provides medical devices comprising nanocomposite materials. By utilizing nanocomposites in the production thereof, the inventive medical devices can be produced with various advantageous properties. Methods of producing the inventive medical devices are also provided. Inasmuch as the inventive devices are expected to provide certain advantages in their use, there is also provide a method of medical care including methods of treatment or diagnosis, wherein the inventive devices are brought into therapeutic contact with a body to be treated or diagnosed thereby.

Abstract: Provided herein is a PEA polymer blend and coatings or implantable devices formed therefrom. The PEA polymer blend is formed of a PEA polymer and a material capable of hydrogen bonding with the PEA. The PEA polymer blend can form a coating on an implantable device, one example of which is a stent. The coating can optionally include a biobeneficial material and/or optionally with a bioactive agent. The implantable device can be used to treat or prevent a disorder such as one of atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof.

Abstract: A bone implant composite comprising a collagen matrix and a calcium-based mineral, the calcium-based mineral having a particle size of 25-2000 ?m and being interspersed in the collagen matrix; wherein the bone implant composite contains 3-60% by weight the collagen matrix and 40-97% by weight the calcium-based mineral, and has a pore size of 50-500 ?m, a density range of 0.02-0.8 g/cm3, and a tensile strength range of 0.4-100 kg/cm2. Also disclosed are methods of preparing the above-described composite.

Abstract: An implantable prosthetic valve that is transformable from a first helical pre-implantation configuration to a second valvular functional configuration, and methods of delivery.

Abstract: A device and methods for improving the function of a heart valve, such as an aortic valve, is disclosed. In one embodiment, the device includes an insert member configured for insertion between leaflets of an aortic valve. The insert member preferably includes three radial arms extending outwardly from a central portion. The device also includes an anchoring member which is coupled to the insert member and configured for maintaining the insert member within the heart valve. In operation, each of the arms fills gaps between heart valve leaflets, thereby minimizing or preventing regurgitation through the heart valve.

Abstract: The present invention relates to an intraluminal medical device formed of a first base material and having a second material inlaid in the base material wherein at least one of said first material and said second material is more radiopaque than the other. The second material may be inlaid in the first either by swaging, rolling, or by coextruding the two materials. The second radiopaque material forms a substantially smooth surface with the first base material.

Abstract: A thin-wall PTFE (polytetrafluoroethylene) tube in the form of a tube of porous expanded PTFE film wherein the porous PTFE film has a microstructure containing a multiplicity of fibrils. The thin-wall tube is used in a non-porous embodiment as the balloon portion of a balloon catheter. The thin-wall tube is not elastomeric; however, because of the thinness, strength and flexibility of the tube, it may be inserted into a body conduit in a collapsed state and then deployed from a catheter and inflated up to the maximum diameter of the thin-wall tube. The porous PTFE film is provided with a continuous layer of adhesive to provide the non-porous tube; the adhesive is preferably a thermoplastic and more preferably a thermoplastic fluoropolymer such as fluorinated ethylene propylene.

Abstract: Expandable heart valves for minimally invasive valve replacement surgeries are disclosed. The valves are rolled into a first, contracted configuration for minimally invasive delivery and then unrolled or unfurled at the implantation site. One- and two-piece stents may be used in conjunction with a plurality of flexible leaflet-forming membranes. The one-piece stents may include an annulus anchoring section, a sinus section with the membranes attached over sinus apertures, and a rigid outflow section. The two-piece stent may include a primary stent to provide a tubular base at the annulus, and a secondary stent having the membranes that couples within the primary stent. Lockout tabs to secure the stents in their expanded shapes are provided. Also, alignment structure may be provided to ensure concentric unfurling. Anchoring barbs at the stent edges or in the stent body secure the valve within the annulus. Methods of implantation are also provided.

Abstract: This invention relates to a device for fastening and anchoring heart valve prostheses which is essentially formed of wire-shaped interconnected elements. The aim of the invention is to be able to be implant, in a minimally invasive manner, a device of this type via the aorta by compressing the device to make it smaller, and by extending the same at the site of implantation, whereby ensuring a secure retention and a secure sealing with regard to the aorta wall. To this end, the invention provides that for fastening and supporting a cardiac valve prosthesis, three identical pairs of arched elements are interconnected, with a configuration that is offset by 120°, by means of solid body articulations. These solid body articulations carry out the function of pivot bearings.

Abstract: A valvular prosthesis and method of using the prosthesis are disclosed. A valve apparatus is located within a stent apparatus, such that the prosthesis is deformable between a first condition and a second condition, in which the prosthesis has a reduced cross-sectional dimension relative to the first condition, whereby implantation of the prosthesis is facilitated when in the second condition.

Abstract: A valve prosthesis is disclosed which is implantable within a vein or other blood vessel of a patient using a minimally-invasive surgical procedure. The prosthesis includes a tubular wire frame which presses radially outward against the inner walls of the blood vessel following implantation to hold the prosthesis in position. Multiple flow-resistive pockets that open and close in response to changes in blood flow direction are attached to the frame to impede the flow of blood in the reverse direction. The prosthesis is implanted using an introducer catheter which holds the prosthesis in a radially-compressed state as the prosthesis is inserted into and positioned within the blood vessel.

Abstract: Provided are crosslinked polymer compositions that include a first synthetic polymer containing multiple nucleophilic groups covalently bound to a second synthetic polymer containing multiple electrophilic groups. The first synthetic polymer is preferably a synthetic polypeptide or a polyethylene glycol that has been modified to contain multiple nucleophilic groups, such as primary amino (—NH2) or thiol (—SH) groups. The second synthetic polymer may be a hydrophilic or hydrophobic synthetic polymer, which contains or has been derivatized to contain, two or more electrophilic groups, such as succinimidyl groups. The compositions may further include other components, such as naturally occurring polysaccharides or proteins (such as glycosaminoglycans or collagen) and/or biologically active agents.

Abstract: An annuloplasty ring having a three-dimensional discontinuous form generally arranged about an axis with two free ends that are axially offset. The ring is particularly suited for repair of the tricuspid valve, and more closely conforms to the annulus shape. The ring is more flexible in bending about radially extending axes than about the central axis. The ring may have an inner structural support covered by a pliable sleeve and/or a fabric tube. The structural support may have a varying cross-section, such as a C-shaped cross-section in a mid-section between two free ends and a rectangular cross-section at the free ends. A deliver template having a mounting ring with about the same shape as the ring facilitates implant, and may be releasably attached to a delivery handle. The deliver template may include a plurality of cutting guides for releasably attaching the annuloplasty ring thereto while presenting maximum outer surface area of the ring.

Abstract: An improved method and apparatus for automated handling of stents using tape and reel, tray or cassette processing equipment is provided to reduce stent and stent coating damage during production, storage and distribution activities, and to allow high volume processing of high-quality stent products. In the tape reel-based system of the present invention, stents are fed into an automated tape assembly device which orients the stents and then feeds them between a carrier tape and a cover tape. The stent-bearing tape assembly is then gathered onto a reel for storage and transport. The stent-bearing tape assembly reel is subsequently loaded into a reel receiver associated with an automated stent coating machine, wherein the stent-bearing tape is fed into an automated tape separator, and the stents removed from the tape assembly are mounted by automated machinery onto stent holders, which in turn pass the stents through a stent coating applicator.

Abstract: A prosthetic valve assembly for use in replacing a deficient native valve comprises a replacement valve supported on an expandable valve support. If desired, one or more anchors may be used. The valve support, which entirely supports the valve annulus, valve leaflets, and valve commissure points, is configured to be collapsible for transluminal delivery and expandable to contact the anatomical annulus of the native valve when the assembly is properly positioned. Portions of the valve support may expand to a preset diameter to maintain coaptivity of the replacement valve and to prevent occlusion of the coronary ostia. A radial restraint, comprising a wire, thread or cuff, may be used to ensure expansion does not exceed the preset diameter. The valve support may optionally comprise a drug elution component. The anchor engages the lumen wall when expanded and prevents substantial migration of the valve assembly when positioned in place.

Abstract: A device for correcting mitral and tricuspid valve regurgitation. The device connects the leaflet bases of the posterior and anterior mitral leaflets to each other with a stabilizing element extended transversely across the valve annulus. The stabilizing element is by first and second ends secured into a first and a second position respectively at the valve annulus using sutures, anchors or clips. Coaptation is attained, by reducing the length of the stabilizing element.

Abstract: A Ti—Zr type alloy manifesting excellent plastic workability at normal temperature fit for the use in general industry, allowing improvement in corrosion resistance fit for the use in medical treatment, offering improved corrosion resistance in an acidic solution, particularly a HCl solution, and having flexibility as evinced by a low Young's modulus on a par with a bone; and a medical appliance such as a guide wire to be directly inserted into a blood vessel of a human body under the X-ray fluoroscopy and a stent retained in a human body for a long time, which are made of the Ti—Zr type alloy are provided. The Ti—Zr type alloy of the present invention consists of 25 to 50% by weight of Ti, 25 to 60% by weight of Zr, 5 to 30% by weight of Nb, and 5 to 40% by weight of Ta, provided that the weight ratio of Zr to Ti be in the range of 0.5 to 1.5 and the weight ratio of Nb to Ta be in the range of 0.125 to 1.5.

Abstract: Expandable heart valves for minimally invasive valve replacement surgeries are disclosed. In a first embodiment, an expandable pre-assembled heart valve includes a plastically-expandable annular base having plurality of upstanding commissure posts. A tubular flexible member including a prosthetic section and a fabric section is provided, with the prosthetic section being connected to the commissure posts and defining leaflets therebetween, and the fabric section being attached to the annular base. In a second embodiment, an expandable heart valve includes an annular tissue-engaging base and a subassembly having an elastic wireform and a plurality of leaflets connected thereto. The annular base and subassembly are separately stored and connected just prior to delivery to the host annulus. Preferably, the leaflet subassembly is stored in its relaxed configuration to avoid deformation of the leaflets. The expandable heart valves may be implanted using a balloon catheter.

Abstract: A prosthetic heart valve having an elastomeric stent with an annular base and a plurality of apertures or holes circumferentially spaced around the base for receiving a suture. Flexible polymeric leaflets are molded over the stent. Polymeric material surrounds the apertures, leaving a central opening in each aperture. The base may be a frustro-conical ring. A sewing ring is mounted on the heart valve by suturing the ring through the apertures. Apertures or holes may also be provided by extending an area covered by woven material around all or part of the circumference of the base.

Abstract: Expandable heart valves for minimally invasive valve replacement surgeries are disclosed. The valves are rolled into a first, contracted configuration for minimally invasive delivery and then unrolled or unfurled at the implantation site. One- and two-piece stents may be used in conjunction with a plurality of flexible leaflet-forming membranes. The one-piece stents may include an annulus anchoring section, a sinus section with the membranes attached over sinus apertures, and a rigid outflow section. The two-piece stent may include a primary stent to provide a tubular base at the annulus, and a secondary stent having the membranes that couples within the primary stent. Lockout tabs to secure the stents in their expanded shapes are provided. Also, alignment structure may be provided to ensure concentric unfurling. Anchoring barbs at the stent edges or in the stent body secure the valve within the annulus. Methods of implantation are also provided.

Abstract: A stent includes a stent member having a plurality of post members formed therein. Each post member is connected to an adjacent post member by an interconnecting portion. A plurality of leg members extend from the stent member. The stent may be molded within a flexible polymer valve. The legs stabilize and locate the stent in the mold. Upon completion of the molding process, the legs can be separated from the stent.

Abstract: The invention relates to a device for fastening and anchoring heart valve prostheses which is essentially formed of wire-shaped interconnected elements. According to the object such a device shall be able to be implanted through the aorta in a minimally invasive manner by folding up small enough, and deployed at the site of implantation, wherein a secure retention and a secure sealing with respect to the aorta wall are ensured. To solve this object, for fastening and anchoring a heart valve prosthesis three respective identical pairs of arched elements are interconnected by means of solid articulations in a respective configuration offset by 120° each. These solid articulations meet the function of pivot bearings.

Abstract: Improved, adaptable tissue-type heart valves and methods for their manufacture are disclosed wherein a dimensionally stable, pre-aligned tissue leaflet subassembly is formed and its peripheral edge clamped between and attached to an upper shaped wireform and a lower support stent. A variety of adaptable structural interfaces including suture rings, flanges, and conduits may be attached to the support stent with or without an outlet conduit disposed about the wireform to provide a tissue-type heart valve adaptable for use in either a natural heart or in mechanical pumping devices. The methods include forming individual leaflets with a template and using the template to attach the leaflets together to form a tissue leaflet subassembly. The template and leaflets include a straight edge terminating in oppositely directed tabs, and a curvilinear cusp edge extending opposite the straight edge.

Abstract: A prosthetic heart valve having an elastomeric stent with an annular base and a plurality of apertures or holes circumferentially spaced around the base for receiving a suture. Flexible polymeric leaflets are molded over the stent. Polymeric material surrounds the apertures, leaving a central opening in each aperture. The base may be a frustro-conical ring. A sewing ring is mounted on the heart valve by suturing the ring through the apertures. Apertures or holes may also be provided by extending an area covered by woven material around all or part of the circumference of the base.

Abstract: A radiopaque nitinol stent for implantation in a body lumen is disclosed. The stent is made from a superelastic alloy such as nickel-titanium or nitinol, and includes a ternary element including tungsten. The added tungsten in specified amounts improve the radiopacity of the nitinol stent comparable to that of a stainless steel stent of the same strut pattern coated with a thin layer of gold. Furthermore, the nitinol stent has improved radiopacity yet retains its superelastic and shape memory behavior and further maintains a thin strut/wall thickness for high flexibility.

Abstract: The subject invention pertains instruments for use in nuclear spin tomography comprising a metal alloy comprising aluminum, vanadium, and titanium. In a specific embodiment, the subject invention relates to cardiovascular stents which can exhibit a low incidence of artifacts and are viewable in a nuclear spin tomography unit. The subject invention also pertains to a method for processing instruments for use in nuclear spin tomography. Such processing can comprise application of a wet chemical etching solution. In a specific embodiment, the wet chemical etching solution can comprise three parts hydrochloric acid and two parts saltpeter acid.

Abstract: A method and a device for improving cardiac function are provided. The device is packaged in a collapsed state in an end of a catheter. Portions of a frame construction of the device spring outwardly when the catheter is withdrawn from the device. Anchoring formations on the frame construction secure the frame construction to a myocardium of the heart. A membrane secured to the frame construction then forms a division between volumes of an endocardial cavity of the heart on opposing sides of the membrane.

Abstract: Storage containers for expandable heart valves for minimally invasive valve replacement surgeries are disclosed. The containers permit an expandable valve to be stored in its expanded configuration and then converted to its contracted configuration while still in the container. A mechanism incorporated into the container facilitates the conversion. For example, the container may have a base and a lid, and a crank manipulable from outside. The lid actuates a key within the container that engages the valve to perform the contraction. If the valve is a spirally wound type of expandable valve, the key may be attached to an inner side edge and rotated to wind the valve into a tight spiral. A drain in the container may facilitate removal of a preservative solution so that the valve can be seen during the contraction process, or so that the valve can be rinsed while still within the container.

Abstract: Cardiovascular components such as biocompatible heart valves and annular sewing rings are disclosed, as well as, methods for making the same. The heart valves include biodegradable polymer fiber scaffolds and collagen. Also disclosed are donor aortic heart valves processed without the use of crosslinking chemicals.

Abstract: A heart valve prosthesis can be formed with a harvested tissue heart valve and a sewing rim that extends outwardly from the annulus of the harvested heart valve for easier attachment of the prosthesis. The heart valve prosthesis can further include a belt that extends along the annulus to provide further support to the valve annulus. A single piece of pericardial tissue can be used to form the sewing rim, belt and a collar that envelopes the edge of the annulus. The harvested heart valve prosthesis can have the diameter of its annulus adjusted using pledgeted suture prior to the application of additional support structures such as the belt, sewing rim and collar.

Abstract: A prosthetic cardiac valvular member of flexible material includes a flexible stent member which may be either attached to the cardiac valvular member or molded therein. The stent member is formed by a plurality of adjacent filaments which are bound together by suturing, braiding, jacketing or encapsulating. The prosthetic cardiac valvular member may be either a flexible heart valve or an annuloplasty ring. Post members are formed into the stent member when the stent member is used in the flexible heart valve.

Abstract: This invention relates to a device for fastening and anchoring heart valve prostheses which is essentially formed of wire-shaped interconnected elements. The aim of the invention is to be able to be implant, in a minimally invasive manner, a device of this type via the aorta by compressing the device to make it smaller, and by extending the same at the site of implantation, whereby ensuring a secure retention and a secure sealing with regard to the aorta wall. To this end, the invention provides that for fastening and supporting a cardiac valve prosthesis, three identical pairs of arched elements are interconnected, with a configuration that is offset by 120°, by means of solid body articulations. These solid body articulations carry out the function of pivot bearings.