Abstract:
Components and portions of components of a hearing prosthesis encapsulated in a microorganism-barrier membrane. Methods and apparatus are described for implanting hearing prosthesis components in precise locations, and maintaining the locations, with at least some components or portions of components encapsulated in a microorganism-barrier membrane.

Description:
BACKGROUND 
       [0001]    This invention relates generally to implantable medical devices, and more particularly, to an implantable adjustable fixation device having reduced infection. 
         [0002]    Implantable medical devices comprise one or more components which are temporarily or permanently implanted in a patient or recipient. Examples of such medical devices are Implantable hearing prostheses which address hearing loss in the recipient. There are generally two types of hearing loss, conductive and sensorineural. Sensorineural hearing loss is due to the absence or destruction of the cochlear hair cells which transduce sound into nerve impulses. Various hearing prostheses have been developed to provide individuals suffering from sensorineural hearing loss with the ability to perceive sound. For example, cochlear implants have an electrode assembly that is implanted in the cochlea. In operation, electrical stimuli are delivered to the auditory nerve via the electrode assembly, thereby bypassing the inoperative hair cells to cause a hearing percept. 
         [0003]    Conductive hearing loss occurs when the natural mechanical pathways that provide sound in the form of mechanical energy to cochlea are impeded, for example, by damage to the ossicular chain or ear canal. For a variety of reasons, individuals having conductive hearing loss are typically not candidates for a cochlear implant. Such individuals typically receive an acoustic hearing aid. Hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. In particular, hearing aids amplify received sound and transmit the amplified sound into the ear canal. This amplified sound reaches the cochlea in the form of mechanical energy, causing motion of the perilymph and stimulation of the auditory nerve. 
         [0004]    Unfortunately, not all individuals suffering from conductive hearing loss are able to derive suitable benefit from hearing aids. For example, some individuals are prone to chronic inflammation or infection of the ear canal. Other individuals have malformed or absent outer ear and/or ear canals resulting from a birth defect, or as a result of medical conditions such as Treacher Collins syndrome or Microtia. 
         [0005]    For these and other individuals, another type of hearing prosthesis has been developed in recent years. This hearing prosthesis, commonly referred to as a middle ear implant, converts received sound into a mechanical force that is applied to the ossicular chain or directly to the cochlea via an actuator implanted in or adjacent to the middle ear cavity. 
       SUMMARY 
       [0006]    The terms “invention,” “the invention,” “this invention,” “the present invention,” “disclosure,” “the disclosure,” “this disclosure” and “the present disclosure” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim. 
         [0007]    The disclosed subject matter improves efficacy of implantable medical devices such as cochlear stimulator devices and their implantation by providing adjustable couplings between actuators and other middle ear components or between an individual&#39;s anatomy and an actuator or other prosthetic component, and by providing improved methods and apparatus for implanting such devices. 
         [0008]    In one embodiment, mechanical couplings are covered with a smooth flexible membrane that prevents microorganism contact, attachment to and/or growth on the coupling surfaces. Such a membrane covering can be, among other alternatives, silicone tubing attached to structures attached to the couplings or silicone moldings molded to or adhesively attached to such structures. 
         [0009]    The membrane may include apertures if needed to provide access for a screw driver or other tool to adjust the coupling. 
         [0010]    Other embodiments of the membrane-covered coupling can use a universal joint or other joint structure that can be manipulated into a desired position and then locked without penetration of the membrane, such as by the application of force. 
         [0011]    In another embodiment, apparatus ends to be coupled in a particular relationship once the remote ends are properly positioned are initially movable but are then fixed in position by a chemical/mechanical means. For instance, the joint-covering membrane can contain a hardenable fluid such as paste or liquid epoxy that is cured by use of ultraviolet light, mixing of epoxy components or another means once the apparatus ends are in the positions desired. Solidification of the epoxy can fix the positions of portions of rods or other components free to move relative to each other before solidification. Solidification of epoxy or another adhesive or other material can also freeze components of an adjustment mechanism encapsulated in a membrane also containing the epoxy, adhesive or other material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Embodiments of the disclosed subject matter are described below with reference to the attached drawings, in which: 
           [0013]      FIG. 1  is perspective view of a human ear; 
           [0014]      FIG. 2A  is a perspective view of an exemplary direct acoustic cochlear stimulator implanted in accordance with embodiments of the present technology; 
           [0015]      FIG. 2B  is a perspective view of an exemplary direct acoustic cochlear stimulator implanted in accordance with another embodiment of the present technology; 
           [0016]      FIG. 2C  is a perspective view of an exemplary direct acoustic cochlear stimulator implanted in accordance with yet another embodiment of the present technology; 
           [0017]      FIG. 3  is a schematic diagram depicting an exemplary implantable component assembly in accordance with an embodiment of the present technology; 
           [0018]      FIG. 3A  is a perspective view of an exemplary internal component of a middle ear implant; 
           [0019]      FIG. 3B  is the perspective view of an exemplary internal component of a middle ear implant shown in  FIG. 3A  with an embodiment of a sheath or membrane encapsulating a component of the implant in accordance with the teachings of the present invention; 
           [0020]      FIG. 4  is a side view schematic diagram, partially in section, of an adjustable coupling encapsulated in a membrane in accordance with the present technology; 
           [0021]      FIG. 5  is a top view of a portion of the membrane-encapsulated coupling of  FIG. 4 ; 
           [0022]      FIG. 6  is a schematic diagram, partially in section, of a membrane capsule containing apparatus ends and uncured epoxy; 
           [0023]      FIG. 7  is another view of the membrane capsule of  FIG. 6  with the apparatus ends flexed; 
           [0024]      FIG. 8  is a schematic depiction of the membrane capsule and apparatus ends of  FIG. 6  during curing of the epoxy with ultraviolet light; 
           [0025]      FIG. 9  is a schematic diagram, partially in section of an alternative embodiment of an epoxy-containing membrane of this invention with an included vial of hardener or catalyst; 
           [0026]      FIG. 10  depicts the application of force to break the vial in the embodiment of  FIG. 9 ; 
           [0027]      FIG. 11  is a top view, partially in section, of a membrane-encapsulated universal joint; 
           [0028]      FIG. 12  and  FIG. 13  depict “free” and “locked” joint components, respectively; and 
           [0029]      FIG. 14  is a schematicized elevation view of a lockable, membrane encapsulated stacked truncated cones joint embodiment of the technology; 
           [0030]      FIG. 15  is a schematic diagram, partly in section, of another membrane-encapsulated coupling; and 
           [0031]      FIG. 16  is a schematicized perspective view of an embodiment of an actuator positioning apparatus. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Subject matter is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
         [0033]      FIG. 1  is perspective view of a human skull showing the anatomy of the human ear. As shown in  FIG. 1 , the human ear comprises an outer ear  101 , a middle ear  105  and an inner ear  107 . In a fully functional ear, outer ear  101  comprises an auricle  110  and an ear canal  102 . An acoustic pressure or sound wave  103  is collected by auricle  110  and channeled into and through ear canal  102 . Disposed across the distal end of ear cannel  102  is a tympanic membrane  104  which vibrates in response to sound wave  103 . This vibration is coupled to oval window or fenestra ovalis  112 , which is adjacent round window  121 . This vibration is coupled through three bones of middle ear  105 , collectively referred to as the ossicles  106  and comprising the malleus  108 , the incus  109  and the stapes  111 . Bones  108 ,  109  and  111  of middle ear  105  serve to filter and amplify sound wave  103 , causing oval window  112  to articulate, or vibrate in response to the vibration of tympanic membrane  104 . This vibration sets up waves of fluid motion of the perilymph within cochlea  140 . Such fluid motion, in turn, activates hair cells (not shown) inside cochlea  140 . Activation of the hair cells causes nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve  114  to the brain (also not shown) where they cause a hearing percept. 
         [0034]    As shown in  FIG. 1 , semicircular canals  125  are three half-circular, interconnected tubes located adjacent cochlea  140 . Vestibule  129  provides fluid communication between semicircular canals  125  and cochlea  140 . The three canals are the horizontal semicircular canal  126 , the posterior semicircular canal  127 , and the superior semicircular canal  128 . The canals  126 ,  127  and  128  are aligned approximately orthogonally to one another. Specifically, horizontal canal  126  is aligned roughly horizontally in the head, while the superior  128  and posterior canals  127  are aligned roughly at a  45  degree angle to a vertical through the center of the individual&#39;s head. 
         [0035]    Each canal is filled with a fluid called endolymph and contains a motion sensor with tiny hairs (not shown) whose ends are embedded in a gelatinous structure called the cupula (also not shown). As the orientation of the skull changes, the endolymph is forced into different sections of the canals. The hairs detect when the endolymph passes thereby, and a signal is then sent to the brain. Using these hair cells, horizontal canal  126  detects horizontal head movements, while the superior  128  and posterior  127  canals detect vertical head movements. 
         [0036]      FIG. 2A  is a perspective view of an example of a direct acoustic cochlear stimulator  200 A. Direct acoustic cochlear stimulator  200 A comprises an external component  242  that is directly or indirectly attached to the body of the recipient, and an internal component  244 A that is temporarily or permanently implanted in the recipient. External component  242  typically comprises two or more sound input elements, such as microphones  224 , for detecting sound, a sound processing unit  226 , a power source (not shown), and an external transmitter unit  225 . External transmitter unit  225  comprises an external coil (not shown). Sound processing unit  226  processes the output of microphones  224  and generates encoded data signals which are provided to external transmitter unit  225 . For ease of illustration, sound processing unit  226  is shown detached from the recipient. 
         [0037]    Internal component  244 A comprises an internal receiver unit  232 , a stimulator unit  220 , and a stimulation arrangement  250 A in electrical communication with stimulator unit  220  via cable  218  extending thorough artificial passageway  219  in mastoid bone  221 . Internal receiver unit  232  and stimulator unit  220  are hermetically sealed within a biocompatible housing, and are sometimes collectively referred to as a stimulator/receiver unit. 
         [0038]    Internal receiver unit  232  comprises an internal coil (not shown), and optionally, a magnet (also not shown) fixed relative to the internal coil. The external coil transmits electrical signals (i.e., power and stimulation data) to the internal coil via a radio frequency (RF) link. The internal coil is typically a wire antenna coil comprised of multiple turns of electrically insulated platinum or gold wire. The electrical insulation of the internal coil is provided by a flexible silicone molding (not shown). In use, implantable receiver unit  232  is positioned in a recess of the temporal bone adjacent auricle  110 . 
         [0039]    In the illustrative embodiment of  FIG. 2A , ossicles  106  have been explanted. However, it should be appreciated that stimulation arrangement  250 A may be implanted without disturbing ossicles  106 . 
         [0040]    Stimulation arrangement  250 A comprises an actuator  240 , a stapes prosthesis  252 A and a coupling element  251 A which includes an artificial incus  261 B. Actuator  240  is osseointegrated to mastoid bone  221 , or more particularly, to the interior of artificial passageway  219  formed in mastoid bone  221 . 
         [0041]    In the embodiment shown in  FIG. 2A , stimulation arrangement  250 A is implanted and/or configured such that a portion of stapes prosthesis  252 A abuts an opening in one of the semicircular canals  125 . For example, in the illustrative embodiment, stapes prosthesis  252 A abuts an opening in horizontal semicircular canal  126 . In alternative embodiments, stimulation arrangement  250 A is implanted such that stapes prosthesis  252 A abuts an opening in posterior semicircular canal  127  or superior semicircular canal  128 . 
         [0042]    As noted above, a sound signal is received by microphone(s)  224 , processed by sound processing unit  226 , and transmitted as encoded data signals to internal receiver  232 . Based on these received signals, stimulator unit  220  generates drive signals which cause actuation of actuator  240 . The mechanical motion of actuator  240  is transferred to stapes prosthesis  252 A such that a wave of fluid motion is generated in horizontal semicircular canal  126 . Because, vestibule  129  provides fluid communication between the semicircular canals  125  and the median canal, the wave of fluid motion continues into median canal, thereby activating the hair cells of the organ of Corti. Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve  114  to cause a hearing percept in the brain. 
         [0043]      FIG. 2B  shows a stimulation arrangement  250 B comprising actuator  240 , a stapes prosthesis  252 B and a coupling element  251 B which includes artificial incus  261 B that couples the actuator to the stapes prosthesis. In this embodiment, stimulation arrangement  250 B is implanted and/or configured such that a portion of stapes prosthesis  252 B abuts round window  121  of cochlea  140 . 
         [0044]    The embodiments of  FIGS. 2A and 2B  are exemplary embodiments of a middle ear implant that provides mechanical stimulation directly to cochlea  140 . Other types of middle ear implants provide mechanical stimulation to middle ear  105 . For example, middle ear implants may provide mechanical stimulation to a bone of ossicles  106 , such to incus  109  or stapes  111 .  FIG. 2C  depicts an exemplary embodiment of a middle ear implant  200 C having a stimulation arrangement  250 C comprising actuator  240  and a coupling element  251 C. Coupling element  251 C includes a stapes prosthesis  252 C and an artificial incus  261 C which couples the actuator to the stapes prosthesis. In this embodiment, stapes prosthesis  252 C abuts stapes  111 . 
         [0045]    As will be appreciated by reference to  FIG. 2A , actuator  240  is located in passageway  219 , and the position of actuator  240  is therefore largely limited by the location of passageway  219 . At the same time, stapes prosthesis  252 A is to be positioned very precisely on semicircular canal  126 . The same is true of other prostheses attached to or contacting other middle ear  105  structures. For instance, stapes prosthesis  252 B illustrated in  FIG. 2B  is to be positioned very precisely on the round window  121  of cochlea  140 , and stapes prosthesis  252 C, and artificial incus  261 C are to be very specifically positioned relative to the stapes  111  shown in  FIG. 2C . 
         [0046]    Since the precise size and anatomy of the inner ear and cranium vary from individual to individual, it is desirable to provide the capability to precisely adjust the position of the stapes prosthesis during implantation. 
         [0047]      FIG. 3A  is a perspective view of an exemplary internal component  344  of a middle ear implant which generally represents internal components  244  described above. Internal component  344  comprises an internal receiver unit  332 , a stimulator unit  320 , and a stimulation arrangement  350 . As shown, receiver unit  332  comprises an internal coil (not shown), and preferably, a magnet  320  fixed relative to the internal coil. As would be appreciated, stimulator unit  320  is typically hermetically sealed within a biocompatible housing. 
         [0048]    Stimulator unit  320  is connected to stimulation arrangement  350  via a cable  328 . Stimulation arrangement  350  comprises an actuator  340 , a stapes prosthesis  354  and a coupling element  353 . A proximal end of stapes prosthesis  354  is connected to actuator  340  via coupling element  353 , and in operation, actuator  340  vibrates stapes prosthesis  354 . Middle ear implant internal component  344  further includes actuator positioning mechanism  370  for positioning actuator  340  and thereby positioning stapes prosthesis  354 . The actuator positioning mechanism may be attached to a fixation system (not shown) secured directly to a bone. In one embodiment, the fixation system comprising a cross-shaped component. The fixation mechanism may be secured via one or more bone screws drilled into the recipient&#39;s skull through apertures located towards the distal ends of the cross-shaped component. The positioning mechanism may contain one or more position/orientation adjustment components each of which commits relative adjustments in position and/or orientation. In  FIG. 3A , an position/orientation adjustment component in the form of a ball joint  372  permits the articulation of actuator  340  relative to middle ear implant internal component  344 . Actuator support  374  is depicted as being in the form of a collar, and receives and otherwise holds actuator  340  therein, and thus holds the actuator to the actuator positioning mechanism  370 . Actuator support  374  allows for longitudinal positioning of the actuator  340  within the actuator support  374 . 
         [0049]    As may be appreciated by reference to  FIG. 3A , the position of stapes prosthesis  354  may be adjusted by moving actuator  340  and thereby moving stapes prosthesis  354  because it is rigidly coupled to actuator  340  by coupling  353 . 
         [0050]    Actuator positioning mechanisms can be very effective, but many of these actuator positioning mechanisms have a position/orientation adjustment component or other component that contains numerous small recesses and crevices. These are structures on which microorganisms can accumulate, become attached and, for example, form biofilms. Such conditions could possibly contribute to undesirable effects such as infections. 
         [0051]      FIG. 3B  is a perspective view of ball joint  372  of actuator positioning member  370  encapsulated by a membrane  380 , also referred to herein as a sheath. In an alternative embodiment, sheath  380  can encapsulate both ball joint  372  and actuator support  374 . Sheath  380  comprises an internal surface proximate to the encapsulated position/orientation adjustment component, and an external surface. In some embodiments, the external surface is substantially smooth to inhibit microorganisms. In other embodiments, the external surface of sheath  380  may be otherwise configured and/or treated to inhibit microorganisms. In yet another alternative embodiment, a sheath  380  may be divided into multiple sheathes (collectively referred to as sheath  380 ), each configured to encapsulate a different part of the position/orientation adjustment component and, to interoperate with each other as necessary to provide the desired encapsulation of the component. In another embodiment, the sheath  380  is a polymeric tube. Suitable polymers include, but are not limited to, silicone, polyurethane, and PTFE. The tube can be substantially conformal to the surfaces of the position/orientation adjustment component. It should be appreciated that in those applications which have multiple position/orientation adjustment components, a single sheath may be configured to encapsulate both such components, or multiple sheaths each configured to encapsulate one such component, may be implemented. 
         [0052]    In a further embodiment, the internal surface of sheath  380  can be substantially attached to the position/orientation adjustment component(s). For example, sheath  380  may comprise a molding configured to conform to the surfaces of the encapsulated component. In other embodiments the sheath may additionally or alternatively be attached to the surfaces of the encapsulated component. 
         [0053]    In another embodiment, sheath  380  further contains a malleable material. The malleable material may comprise a liquid such as un-cured silicone. When the encapsulated component has been positioned in the desired orientation, the malleable material can be hardened, for example by being cured with ultraviolet light. 
         [0054]    Actuator positioning mechanisms can be very effective, but they are sometimes difficult to manipulate and adjust.  FIGS. 4 and 5  depict a tool-position/orientation adjustment component  410  between two mechanical structural components  412 ,  414 , where one of the two components  412  and  414  would be coupled to an electromechanical actuator and the other would be anchored or directly or indirectly coupled to an anchored component of the device, such as a fixation system ( FIGS. 3A and 3B ). Position/orientation adjustment component  410  includes a ball  416  clasped by arms  418  that are tightened around ball  416  by a screw  420 . Position/orientation adjustment component  410  is encapsulated by a membrane  422  that surrounds the component  410  and sealingly engages mechanical structures  412 ,  414 . A screwdriver (not shown) can be inserted through a slit  424  in membrane  422  so that screw  420  can be adjusted. Slit  424  may be self-closing or may be sealed with adhesive after completion of such a screw adjustment. 
         [0055]      FIGS. 6 ,  7  and  8  depict a membrane  622  that is filled with a material  610  that is initially a liquid or other fluid (such as paste) within which ends  614  and  616  of joint members  618  and  620  are initially free to move, permitting joint members  618  and  620  to be positioned in a wide variety of angles and other orientations relative to each other. After such positioning has been achieved, the material  610  and  611  is caused to harden or solidify. An exemplary material  610  is silicone which is cured by the application of ultraviolet light  810  as depicted in  FIG. 8  (material  610  is UV light hardening). An alternative exemplary material  610  is a two-part material such as epoxy resin that hardens when the parts are mixed, for example, by breaking a vial of hardener  912  as depicted in  FIGS. 9 and 10 . 
         [0056]    As an alternative to a vial of hardener  912 , a membrane wall  1510  (shown in  FIG. 15 ) could divide the space within membrane  1522  with epoxy resin or another first material  1524  on one side of the wall  1510  and hardener, catalyst or another second material  1526  on the other. Membrane  1522  could be manipulated to cause the dividing membrane  1510  to rupture, allowing mixing of the two components  1526  and  1524 . 
         [0057]    Materials  610  and  611  may be silicone or epoxy being ultraviolet light-hardening, two part or other existing or future material that is initially fluid and subsequently hardens. Hardening can occur with the passage of time or can be made to harden when desired. Materials  1524  and  1526  on opposite sides of dividing membrane in  FIG. 15  can likewise be epoxy resin and hardener, another material and a catalyst, or other two-component systems that are initially liquid and then solidify when mixed. 
         [0058]    Following solidification of the materials  610 ,  611  or  1525  and  1526  as described above, the associated membrane  622  or  1622  will can provide a smooth surface that does not promote retention and growth of microorganisms or biofilms. Under some circumstances, it may be possible to remove membrane  622  or  1522  leaving a smooth epoxy or other rigidified material that likewise will not promote retention and growth of microorganisms or biofilms. 
         [0059]      FIGS. 11 ,  12  and  13  depict a membrane  1122  encapsulated universal joint  1112  between a first component  1114  and second component  1116 . Universal joint  1112  may be locked after desired positioning is achieved. 
         [0060]    As an example, the universal joint  1112  may be locked, as schematically depicted in  FIGS. 12 and 13 , by application of opposed forces  1310  and  1312  driving locking members  1312  and  1314 , thereby causing the end  1316  to flare as depicted in  FIG. 13 . Flared end  1316  engages surrounding joint member  1318 , thereby locking end  1316  and joint member  1318  so that they cannot rotate or otherwise move relative to each other. Numerous other locking schemes would be usable with a universal joint like joint  1112 . For instance, the membrane  1122  could be filled with epoxy or other hardenable material that is caused to harden or permitted to harden after joint  1112  is positioned as desired. 
         [0061]    Yet another alternative embodiment of this invention is depicted in  FIG. 14 , in which a nested stack  1412  of truncated cones  1414  covered by membrane  1410  form a coupling between an actuator  1416  and an individual&#39;s cranium  1418  or other appropriate anchoring structure. After actuator  1416  has been positioned as desired, wire  1420  inside of the stack  1412  of cones  1414  is tensioned, thereby locking the nested stack  1412  in position. 
         [0062]    As will be appreciated by reference to the Figures and corresponding description above, some embodiments of the present invention, such as those depicted in  FIGS. 4 and 5 , involve manipulation of portions of the implant structure with screwdrivers or other tools in order to position the implant components as desired. Because of the small size, the geometry and other factors, this direct manipulation of joint components can be difficult. Other of the exemplary embodiments of the present technology depicted in the drawings and or described above function by more directly placing components as desired and then solidifying the coupling between the components, such as by hardening epoxy or another suitable material to lock portions of the components in desired relative positions. 
         [0063]    As an alternative to direct adjustment of couplings, and when solidifying materials are used to lock the relative positions of components once placed in those positions, a placement structure such as the one schematically depicted in  FIG. 16  may be used. As one example of such a device, a reference structure  1610  would be temporarily positioned relative to an individual&#39;s scull (not shown) with contact at contact points  1612 . A robotic arm  1614  mounted on reference structure  1610  holding an actuator  1616  could then position actuator  1616  within an appropriate cavity  1618 . After a desired position for actuator  1616  (or another component requiring precise positioning) is achieved, a coupling located (directly or indirectly) between the actuator  1616  (or other component requiring precise positioning) and an attachment structure could be rigidified as depicted in, for instance,  FIGS. 6-10  and  14 . The robotic arm  1614  and reference structure  1610  could then be removed, and the rigidified coupling would hold the components in position. 
         [0064]    Different arrangements are possible of the components depicted in the drawings or described above, as well as components and steps not shown or described. Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present technology is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications can be made without departing from the scope of the claims below and their equivalents. For instance, a number of different materials in addition to silicone may be usable to encapsulate components with complex surfaces. Such materials may be formed as sheets, tubes, capsules or other shapes and then positioned around the prosthetic components as described above, in some instances (but not always) using adhesive. Alternatively, such a barrier may be formed in place encapsulating the prosthetic components. Formation of a smooth-surfaced capsule may be accomplished using a mold to contain liquid or another fluid until it solidifies. Alternatively, some such materials that naturally form a smooth-surfaced mass may be formed in place without the need for a mold.