U.S. patent application number 15/162814 was filed with the patent office on 2016-09-15 for stimulating assembly fixation features.
The applicant listed for this patent is Nicholas Charles Kendall Pawsey, Frank Risi. Invention is credited to Nicholas Charles Kendall Pawsey, Frank Risi.
Application Number | 20160263371 15/162814 |
Document ID | / |
Family ID | 52996244 |
Filed Date | 2016-09-15 |
United States Patent
Application |
20160263371 |
Kind Code |
A1 |
Pawsey; Nicholas Charles Kendall ;
et al. |
September 15, 2016 |
STIMULATING ASSEMBLY FIXATION FEATURES
Abstract
Embodiments presented herein are generally directed to a
stimulating assembly of a cochlear implant. The stimulating
assembly comprises one or more fixation features configured to be
inserted into a recipient's cochlea via an opening in the cochlea.
Following insertion, the one or more fixation features are
configured to engage an inner surface of the cochlea adjacent to
the opening to prevent movement of the stimulating assembly out of
the cochlea through the opening.
Inventors: |
Pawsey; Nicholas Charles
Kendall; (North Ryde, AU) ; Risi; Frank;
(Newtown, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pawsey; Nicholas Charles Kendall
Risi; Frank |
North Ryde
Newtown |
|
AU
AU |
|
|
Family ID: |
52996244 |
Appl. No.: |
15/162814 |
Filed: |
May 24, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14064586 |
Oct 28, 2013 |
9375565 |
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15162814 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/0541
20130101 |
International
Class: |
A61N 1/05 20060101
A61N001/05; A61N 1/36 20060101 A61N001/36 |
Claims
1. An assembly for insertion into a cochlea of a recipient through
an opening in the cochlea, comprising: an elongate carrier member;
and at least one expandable fixation feature disposed at a proximal
portion of the carrier member and configured to expand after
insertion into the cochlea in order to prevent movement of the
stimulating assembly out of the cochlea through the opening.
2. The assembly of claim 1, wherein the at least one expandable
fixation feature has a first insertion configuration that enables
the expandable fixation feature to pass through the opening, and a
second expanded configuration such that the at least one expandable
fixation feature engages an inner surface of the cochlea adjacent
to the opening so as to prevent movement of the stimulating
assembly out of the cochlea.
3. The assembly of claim 1, wherein in the first insertion
configuration the at least one expandable fixation feature has a
first thickness, and wherein in the second expanded configuration
the at least one expandable fixation feature has a second
thickness, wherein the second thickness if greater than the first
thickness.
4. The assembly of claim 1, wherein the at least one expandable
fixation feature is configured to swell when exposed to the
recipient's cochlea fluid.
5. The assembly of claim 4, wherein the at least one expandable
fixation feature is formed from a biocompatible hygroscopic
material.
6. The assembly of claim 1, wherein the at least one expandable
fixation feature is a section of the proximal portion of the
carrier member.
7. The assembly of claim 1, wherein the at least one expandable
fixation feature is an element molded around an outer surface of
the proximal portion of the carrier member.
8. The assembly of claim 1, wherein the assembly comprises a
plurality of stimulating contacts disposed in the carrier member,
and the expandable fixation feature is disposed proximal to the
stimulating contacts.
9. The assembly of claim 8, wherein the expandable fixation feature
is part of the carrier member, and the carrier member is configured
so that the expandable fixation features is disposed distal to the
opening in the cochlea after insertion of the assembly.
10. The assembly of claim 1, wherein the at least one expandable
fixation feature is configured to expand substantially radially
within the recipient's cochlea to form an annular flange.
11. An intra-cochlea stimulating assembly comprising: an elongate
carrier member; a plurality of stimulating contacts disposed in the
carrier member; and at least one compressible fixation feature
disposed at a proximal portion of the carrier member and having a
pre-insertion configuration, wherein the at least one compressible
fixation feature is configured to be compressed during insertion
into the cochlea and to uncompress after insertion into the cochlea
to prevent movement of the stimulating assembly out of the
cochlea.
12. The stimulating assembly of claim 11, wherein after insertion
into the cochlea, the at least one compressible fixation feature
engages an inner surface of the cochlea adjacent an opening so as
to prevent movement of the stimulating assembly out of the
cochlea.
13. The stimulating assembly of claim 11, wherein the at least one
compressible fixation feature is configured to bend in a proximal
direction as the at least one compressible fixation feature passes
through the opening and is configured to substantially resist
bending in a distal direction after insertion into the cochlea.
14. The stimulating assembly of claim 11, wherein the at least one
compressible fixation feature comprises a compressible flange.
15. The stimulating assembly of claim 11, wherein the compressible
fixation feature is disposed at an intra-cochlea portion of the
elongate carrier member proximal to the stimulating contacts.
16. The stimulating assembly of claim 11, wherein the at least one
compressible fixation feature is configured to be positioned
entirely within the cochlea after insertion of the stimulating
assembly.
17. An apparatus, comprising: an elongate carrier member; a
plurality of stimulating contacts disposed in the carrier member;
and at least one fixation feature disposed at an intra-cochlea
portion of the carrier member, wherein the at least one fixation
feature has a first configuration to enable the at least one
fixation feature to pass through an opening in a recipient's
cochlea, and a second configuration to engage an inner surface of
the cochlea adjacent to the opening so as to prevent movement of
the stimulating assembly out of the cochlea.
18. The stimulating assembly of claim 17, wherein the at least one
fixation feature is configured to: (i) be compressed immediately
before insertion into the cochlea through the opening, and (ii)
expand after insertion into the cochlea in order to engage the
inner surface of the cochlea adjacent the opening.
19. The stimulating assembly of claim 17, wherein the at least one
fixation feature is configured to expand radially outward from the
elongate carrier member.
20. The stimulating assembly of claim 17, wherein the at least one
fixation feature is disposed proximal to the stimulating contacts
and configured to be distal to the opening after insertion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 14/064,586, filed on Oct. 28,
2013, the content of which is hereby incorporated by reference
herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to an implantable
stimulating assembly, and more particularly, to stimulating
assembly fixation features.
[0004] 2. Related Art
[0005] Hearing loss, which may be due to many different causes, is
generally of two types, conductive and/or sensorineural. Conductive
hearing loss occurs when the normal mechanical pathways of the
outer and/or middle ear are impeded, for example, by damage to the
ossicular chain or ear canal. Sensorineural hearing loss occurs
when there is damage to the inner ear, or to the nerve pathways
from the inner ear to the brain.
[0006] Individuals who suffer from conductive hearing loss
typically have some form of residual hearing because the hair cells
in the cochlea are undamaged. As such, individuals suffering from
conductive hearing loss typically receive an auditory prosthesis
that generates motion of the cochlea fluid. Such auditory
prostheses include, for example, acoustic hearing aids, bone
conduction devices, and direct acoustic stimulators.
[0007] In many people who are profoundly deaf, however, the reason
for their deafness is sensorineural hearing loss. Those suffering
from some forms of sensorineural hearing loss are unable to derive
suitable benefit from auditory prostheses that generate mechanical
motion of the cochlea fluid. Such individuals can benefit from
implantable auditory prostheses that stimulate nerve cells of the
recipient's auditory system in other ways (e.g., electrical,
optical and the like). Cochlear implants are often proposed when
the sensorineural hearing loss is due to the absence or destruction
of the cochlea hair cells, which transduce acoustic signals into
nerve impulses. Auditory brainstem stimulators might also be
proposed when a recipient experiences sensorineural hearing loss
due to damage to the auditory nerve.
SUMMARY
[0008] In one aspect of the invention, a stimulating assembly for
insertion into a cochlea of a recipient through an opening in the
cochlea is provided. The stimulating assembly comprises an elongate
carrier member having a proximal end and a distal end and a
plurality of stimulating contacts disposed along at least a first
surface of the carrier member. A fixation feature is formed in the
proximal end of the carrier member and is configured to, after
insertion into the cochlea; prevent movement of the stimulating
assembly out of the cochlea through the opening.
[0009] In one aspect of the invention, an apparatus is provided.
The apparatus comprises an elongate carrier member having first and
second distally extending portions and a plurality of stimulating
contacts disposed along at least a first surface of the second
portion. The carrier member comprises a transition region having a
shape such that the second portion of the elongate carrier member
is offset from the first portion of the carrier member.
[0010] In another aspect of the invention, a stimulating assembly
for insertion into a cochlea of a recipient through an opening in
the cochlea is provided. The stimulating assembly comprises an
elongate carrier member having a proximal portion and a distal
portion, a plurality of stimulating contacts disposed along at
least a first surface of the distal portion, and a fixation feature
comprising a portion of the carrier member formed into a zigzag
shape such that the distal portion of the elongate carrier member
is offset from the proximal portion of the carrier member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the present invention are described herein in
conjunction with the accompanying drawings, in which:
[0012] FIG. 1 is a schematic diagram of an implanted cochlear
implant comprising a stimulating assembly having a fixation feature
in accordance with embodiments presented herein;
[0013] FIG. 2A is a side view of a stimulating assembly comprising
a fixation feature in accordance with embodiments of the present
invention;
[0014] FIG. 2B is an enlarged view of the fixation feature of the
stimulating assembly illustrated in FIG. 2A;
[0015] FIG. 2C is a side view of the stimulating assembly
illustrated in FIG. 2A following insertion into a recipient's
cochlea;
[0016] FIG. 3A is a side view of another stimulating assembly
comprising a fixation feature in accordance with embodiments of the
present invention;
[0017] FIG. 3B is an enlarged view of the fixation feature of the
stimulating assembly illustrated in FIG. 3A;
[0018] FIG. 3C is a side view of the stimulating assembly
illustrated in FIG. 3A following insertion into a recipient's
cochlea;
[0019] FIG. 4A is a side view of another stimulating assembly
comprising a fixation feature in accordance with embodiments of the
present invention;
[0020] FIG. 4B is a side view of the stimulating assembly
illustrated in FIG. 4A following insertion into a recipient's
cochlea;
[0021] FIG. 4C is a side view of the stimulating assembly of FIG.
4A with a straightening sheath in accordance with embodiments of
the present invention;
[0022] FIG. 5A is a side view of a stimulating assembly comprising
a fixation feature in accordance with embodiments of the present
invention;
[0023] FIG. 5B is a side view of the stimulating assembly
illustrated in FIG. 5A following insertion into a recipient's
cochlea;
[0024] FIG. 6A is a side view of a stimulating assembly comprising
a fixation feature in accordance with embodiments of the present
invention;
[0025] FIG. 6B is a side view of the stimulating assembly
illustrated in FIG. 5A following insertion into a recipient's
cochlea;
[0026] FIG. 7 is a side view of a stimulating assembly comprising a
plurality of fixation features in accordance with embodiments of
the present invention;
[0027] FIG. 8A is a side view of another stimulating assembly
comprising fixation features in accordance with embodiments of the
present invention;
[0028] FIG. 8B is a side view of the stimulating assembly
illustrated in FIG. 8A during insertion into a recipient's
cochlea;
[0029] FIG. 8C is a side view of the stimulating assembly
illustrated in FIG. 8A following insertion into a recipient's
cochlea; and
[0030] FIG. 9 is a side view of a stimulating assembly comprising a
plurality of fixation features in accordance with embodiments of
the present invention.
DETAILED DESCRIPTION
[0031] Embodiments presented herein are generally directed to a
stimulating assembly of a cochlear implant (also commonly referred
to as cochlear implant device, cochlear prosthesis, and the like;
simply "cochlear implant" herein). The stimulating assembly
comprises one or more fixation features configured to be inserted
into a recipient's cochlea via an opening in the cochlea. Following
insertion, the one or more fixation features are configured to
engage an inner surface of the cochlea adjacent to the opening to
prevent movement of the stimulating assembly out of the cochlea
through the opening.
[0032] FIG. 1 is perspective view of an exemplary cochlear implant
100 in accordance with embodiments presented herein. The cochlear
implant 100 includes an external component 142 and an internal or
implantable component 144. The external component 142 is directly
or indirectly attached to the body of the recipient and typically
comprises one or more sound input elements 124 (e.g., microphones,
telecoils, etc.) for detecting sound, a sound processor 134, a
power source (not shown), an external coil 130 and, generally, a
magnet (not shown) fixed relative to the external coil 130. The
sound processor 134 processes electrical signals generated by a
sound input element 124 that is positioned, in the depicted
embodiment, by auricle 110 of the recipient. The sound processor
134 provides the processed signals to external coil 130 via a cable
(not shown).
[0033] The implantable component 144 comprises an implant body 105,
a lead region 108, and an elongate stimulating assembly 118. The
implant body 105 comprises a stimulator unit 120, an internal coil
136, and an internal receiver/transceiver unit 132, sometimes
referred to herein as transceiver unit 132. The transceiver unit
132 is connected to the internal coil 136 and, generally, a magnet
(not shown) fixed relative to the internal coil 136. Internal
transceiver unit 132 and stimulator unit 120 are sometimes
collectively referred to herein as a stimulator/transceiver unit
120.
[0034] The magnets in the external component 142 and implantable
component 144 facilitate the operational alignment of the external
coil 130 with the internal coil 136. The operational alignment of
the coils enables the internal coil 136 to transmit/receive power
and data to/from the external coil 130. More specifically, in
certain examples, external coil 130 transmits electrical signals
(e.g., power and stimulation data) to internal coil 136 via a radio
frequency (RF) link. Internal coil 136 is typically a wire antenna
coil comprised of multiple turns of electrically insulated
single-strand or multi-strand platinum or gold wire. The electrical
insulation of internal coil 136 is provided by a flexible silicone
molding. In use, transceiver unit 132 may be positioned in a recess
of the temporal bone of the recipient. Various other types of
energy transfer, such as infrared (IR), electromagnetic, capacitive
and inductive transfer, may be used to transfer the power and/or
data from an external device to cochlear implant and FIG. 1
illustrates only one example arrangement.
[0035] Elongate stimulating assembly 118 is implanted in cochlea
140 and includes a contact array 146 comprising a plurality of
stimulating contacts 148. Stimulating assembly 118 extends through
cochleostomy 122 and has a proximal end connected to stimulator
unit 120 via lead region 108 that extends through mastoid bone 119.
Lead region 108 couples the stimulating assembly 118 to implant
body 105 and, more particularly, stimulator/transceiver unit 120.
The stimulating contacts 148 may be electrical contacts, optical
contacts, or a combination of optical and electrical contacts.
Present commercial devices offered by the industry use electrical
contacts, but Cochlear and others are engaged in research on the
potential uses of optical stimulation alone of in conjunction with
electrical or other stimulation mechanisms.
[0036] There are a variety of types of intra-cochlear stimulating
assemblies that may be inserted into a recipient's cochlea. For
example, a perimodiolar stimulating assembly is a stimulating
assembly that is configured to adopt a curved configuration during
and/or after implantation into the recipient's cochlea. To achieve
this, the stimulating assembly may be pre-curved to the same
general curvature of a cochlea. Perimodiolar stimulating assemblies
are typically held straight by, for example, a stiffening stylet or
sheath which is removed during implantation. Varying material
combinations or shape memory materials may also be used so that the
stimulating assembly may adopt its curved configuration when in the
cochlea.
[0037] A stimulating assembly can also be a non-perimodiolar
stimulating assembly. A non-perimodiolar stimulating assembly may
be a substantially straight assembly, a mid-scala assembly which
assumes a mid-scala position during or following implantation, or a
short assembly implanted into at least a basal region of the
cochlea. The stimulating assembly may extend towards the apical end
of the cochlea, referred to as the cochlea apex.
[0038] In certain circumstances a stimulating assembly may extrude
(i.e., migrate/withdraw) from a recipient's cochlea. Extrusion of a
stimulating assembly may negatively impact hearing performance of
the stimulating assembly. As such, in the embodiments of FIG. 1, a
fixation feature 102 is disposed near a proximal end of the
stimulating assembly 118. The fixation feature 102 is configured to
be inserted through the cochleostomy 122 and, following insertion,
engage an inner surface of the cochlea 140 adjacent to the
cochleostomy 122 to prevent extrusion of the stimulating assembly
out of the cochlea 140.
[0039] FIGS. 2A-2C are side views of a stimulating assembly 218
that comprises a fixation feature 202 in accordance with
embodiments presented herein. FIG. 2A illustrates stimulating
assembly 218 prior to insertion into a recipient's cochlea, while
FIG. 2B illustrates an enlarged view of the fixation feature 202
prior to insertion. FIG. 2C illustrates electrode assembly 218
after insertion when the fixation feature 202 is positioned to
substantially prevent extrusion/migration of the stimulating
assembly 218 out of the recipient's cochlea 240.
[0040] Stimulating lead assembly 218 comprises a carrier member 204
having a distal end 210 and a proximal end 212. Distal end 210
terminates in a tip 211 that is adapted to be implanted furthest
into the recipient's cochlea 240. A plurality of spaced stimulating
contacts 248 are mounted or disposed in/on at least a first surface
214 of the carrier member 204 between the proximal end 212 and the
distal end 210. It should be appreciated that as used herein,
particular combinations of the terms mounted/disposed, in/on, etc.,
are not to be interpreted to refer to any particular manufacturing
technique or structural relationship.
[0041] The carrier member 204 includes a second surface 216 that
opposes the first surface 214. The carrier member 204 may have, for
example, a circular, oval, or other cross-sectional shape. As such,
"opposing surfaces" refers to the fact that at least a portion of
each of the surfaces 214 and 216 faces in substantially opposing
directions from one another. Carrier member 204 may be manufactured
from a silicone material and is connected to a lead region (not
shown in FIG. 2A) from the proximal region. The lead region
physically and electrically connects stimulating lead assembly 218
with a stimulator unit (not shown in FIG. 2A).
[0042] The fixation feature 202 is configured to substantially
prevent extrusion of the stimulating assembly 218 from the cochlea
240. In the embodiment of FIGS. 2A-2C, the fixation feature 202 is
formed by a portion 250 of the carrier member 204 and a portion 252
of a shape element 254 permanently disposed in the carrier member
204. The fixation feature 202 is, in essence, a transition region
in the stimulating assembly 218 that connects two offset segments
(portions) of the stimulating assembly 218, namely a proximal or
first portion 205 and a second or distal portion 207. The fixation
feature 202 has a generally zigzag or sinuous shape.
[0043] As shown in FIG. 2C, following insertion of the stimulating
assembly 218 into a recipient's cochlea, the fixation feature 202
is configured to engage an inner surface (wall) 227 of the cochlea
240 adjacent to an opening 274 (through which the stimulating
assembly 218 is inserted) to prevent movement of the stimulating
assembly out of the cochlea through the opening 274. The shape and
mechanical properties of the fixation feature 202 cause a region
223 of surface 216 to abut the wall 227 within the cochlea 240. In
this implanted position, the region 223 of surface 216 is
substantially parallel to the wall 227, but is substantially
perpendicular to a central axis 229 of the opening 274. As such,
the fixation feature 202 operates with the cochlea wall 227 to
resist/counteract forces from within the cochlea 240 towards
opening 274.
[0044] As shown in greater detail in FIG. 2B, the portion 252 of
shape element 254 comprises a first angle 260 and a second angle
262. The first angle 260 faces substantially away from first
surface 214 of the stimulating assembly 218, while the second angle
262 faces substantially towards the first surface 214 of the
stimulating assembly 218. That is, the first and second angles 260
and 262 face in substantially opposing directions forming a zigzag
shape within shape element 254 at segment 252. Stated differently,
the portion 252 comprises two substantially parallel and offset
segments 255(A) and 255(B) connected by a third segment 257. Prior
to insertion into a cochlea while in a steady (i.e., non-biased and
non-stretched) state, the segments 255(A) and 255(B) are offset
from one another by a distance 258.
[0045] The carrier member 204 is molded around the shape element
254 such that the portion 250 of the carrier member 204 has a shape
corresponding to the shape of portion 252. That is, portion 250
comprises a first angle 270 and a second angle 272 generally
corresponding to the first angle 260 and second angle 262,
respectively, of shape element 254. The first and second angles 270
and 272 substantially oppose one another forming a zigzag pattern
within carrier member 204 at portion 250.
[0046] In general, the angle 260 in FIG. 2B should be minimized in
order to make insertion possible, while still providing sufficient
function as a feature to prevent migration. In the example of FIG.
2B, angle 260 is approximately 150 degrees. In certain embodiments,
the angle 260 may be in the range of approximately 160 degrees to
approximately 170 degrees. As such, in certain embodiments, the
angle 260 may be larger than angle 262.
[0047] It is to be appreciated that the lengths of segment 257 and
fixation feature 202 shown in FIGS. 2A-2C are merely illustrative.
In other embodiments, the segment 257 and fixation feature 202 may
be relatively longer than as shown in FIGS. 2A-2C. The lengths of
segment 257 and fixation 202 are generally selected to provide
sufficient offset to enable the fixation feature 202 to interlock
with a wall of the cochlea.
[0048] A surgeon inserts stimulating assembly 218 into cochlea 240
via an opening 274. The opening 274 may be, for example, the oval
window, round window or other natural or man-made aperture (e.g.,
cochleostomy) in cochlea 240. In particular, the surgeon "pushes"
the stimulating assembly 218 through the opening 274 in the
direction of the apical end of the cochlea 240. In certain
examples, the fixation feature 202 may be partially deformed from
the zigzag shape so as to fit through the opening 274.
[0049] In terms of surgical technique, the surgeon will likely grip
the stimulating assembly 218 at, or as close as possible to, the
fixation feature 202 during most of the insertion. The surgeon may
only grip proximal end 212 in the final stage to push the fixation
feature 202 through the cochlea opening. 100481 When the surgeon
ceases to push the stimulating assembly 218 into the cochlea 240,
the stimulating assembly 218 will have a tendency to migrate in the
direction of the opening 274. This tendency may be the result of
internal forces within the stimulating assembly 218 (i.e., elastic
nature of the carrier member 204 and/or the electrical conductors
disposed therein) and/or interaction of the stimulating assembly
with the cochlea 240 that place bias force(s) on the stimulating
assembly 218 in a proximal direction. The bias force(s) on
stimulating assembly 218 are represented in FIG. 2C by arrow
277.
[0050] The shape element 254 is formed from a material having
elastic properties such as a nitinol alloy or an elastomeric
polymer such as silicone rubber. Due to the elastic nature of the
shape element 254, the bias forces 277 cause the fixation feature
202 (i.e., portion 223 of surface 216) to be forced against wall
227 of the cochlea 240 that is adjacent to the opening 274. In this
case, the portion 223 is substantially parallel to the wall 227 at
a point between the opening 274 and the lateral wall 235 of the
cochlea 240. The interaction of fixation feature 202 with the wall
227 of the cochlea 240 will counteract the bias forces 277 to
prevent movement of the stimulating assembly 218 out of the cochlea
through the opening 274.
[0051] In general, a stimulating assembly remains implanted in a
recipient permanently. However, in certain circumstances, a
stimulating assembly may be removed from a recipient during surgery
(i.e., to reposition the stimulating assembly) or after a period of
time. Although the fixation feature 202 is configured to prevent
migration of the stimulating assembly 218 out of the cochlea 240,
the fixation feature 202 does not prevent surgical removal of the
stimulating assembly 218. More specifically, as noted above, the
fixation feature 202 is configured such that the bias forces 277
force the fixation feature against the cochlea wall. However, when
a surgeon places a tensile force on the proximal end 212 of the
stimulating assembly 218, the elastic nature of the shape element
254, coupled with the zigzag shape, causes the fixation feature 202
to at least partially straighten and slide out of the cochlea
through the opening 274. Therefore, the fixation feature 202 is
configured to operate with the cochlea wall to resist/counteract
forces from within the cochlea 240 towards opening 274, but is at
least partially non-resistive to tensile forces placed on the
stimulating assembly 218 outside of the cochlea 240.
[0052] It is also to be appreciated that the zigzag shape of
fixation feature 202 shown in FIGS. 2A-2C is merely illustrative.
Fixation feature 202 may have any other shape that, when inserted
in the cochlea 240, causes a region of the lower surface (i.e.,
surface 216) to be substantially parallel to the wall 227 so as to
operate with the cochlea wall 227 to resist/counteract forces from
within the cochlea 240 towards opening 274, while still enabling
removal of the stimulating assembly 218 (i.e., at least partially
non-resistive to tensile forces placed on the stimulating assembly
218 outside of the cochlea 240).
[0053] FIGS. 3A-3C are side views of another stimulating assembly
318 comprising a fixation feature 302 in accordance with
embodiments presented herein. Fixation feature 302 is similar to
fixation feature 202, but has an alternative zigzag shape.
[0054] FIG. 3A illustrates stimulating assembly 318 prior to
insertion into a recipient's cochlea, while FIG. 3B illustrates an
enlarged view of the fixation feature 302. FIG. 3C illustrates
electrode assembly 318 after insertion when the fixation feature
302 is positioned to substantially prevent extrusion/migration of
the stimulating assembly 318 out of the recipient's cochlea
340.
[0055] Stimulating lead assembly 318 comprises a carrier member 304
having a distal end 310 and a proximal end 312. Distal end 310
terminates in a tip 311 that is adapted to be implanted furthest
into the recipient's cochlea 340. A plurality of spaced stimulating
contacts 348 are mounted or disposed in/on at least a first surface
314 of the carrier member 304 between the proximal end 312 and the
distal end 310.
[0056] The carrier member 304 includes a second surface 316 that
opposes the first surface 314. The carrier member 304 may have, for
example, a circular, oval, or other cross-sectional shape. Carrier
member 304 may be manufactured from a silicone material and is
connected to a lead region (not shown in FIG. 3A). The lead region
physically and electrically connects stimulating lead assembly 318
with a stimulator unit (not shown in FIG. 3A).
[0057] The fixation feature 302 is configured to substantially
prevent extrusion of the stimulating assembly 318 from the cochlea
340. In the embodiments of FIGS. 3A-3C, the fixation feature 302 is
formed by a portion 350 of the carrier member 304 and a portion 352
of a shape element 354 permanently disposed in the carrier member
304. The fixation feature 302 is, in essence, a transition region
in the stimulating assembly 318 that connects two offset segments
(portions) of the stimulating assembly 318, namely a proximal or
first portion 305 and a second or distal portion 307. The fixation
feature 302 has a generally zigzag or sinuous shape.
[0058] As shown in FIG. 3C, following insertion of the stimulating
assembly 318 in a recipient's cochlea, the fixation feature 302 is
configured to engage an inner surface (wall) 327 of the cochlea 340
adjacent to an opening 374 (through which the stimulating assembly
318 is inserted) to prevent movement of the stimulating assembly
out of the cochlea through the opening 374. The shape and
mechanical properties of the fixation feature 302 cause a region
323 of surface 314 to abut the wall 327 within the cochlea 340. In
this implanted position, the region 323 of surface 314 is
substantially parallel to the wall 327, but is substantially
perpendicular to a central axis 329 of the opening 374. As such,
the fixation feature 302 operates with the cochlea wall 327 to
resist/counteract forces from within the cochlea 340 towards
opening 374.
[0059] As shown in greater detail in FIG. 3B, the portion 352 of
shape element 354 comprises a first angle 360 and a second angle
362. The first angle 360 faces substantially towards the first
surface 314 of the stimulating assembly 318, while the second angle
362 faces substantially away from first surface 314 of the
stimulating assembly 318. That is, the first and second angles 360
and 362 face substantially opposing directions forming a zigzag
pattern within shape element 354 at segment 352. Stated
differently, the portion 352 comprises two substantially parallel
and offset segments 355(A) and 355(B) connected by a third segment
357. Prior to implantation, the segments 355(A) and 355(B) are
offset from one another by a distance 358.
[0060] The carrier member 304 is molded around the shape element
354 such that the portion 350 of the carrier member 304 has a shape
corresponding to the shape of portion 352. That is, portion 350
comprises a first angle 370 and a second angle 372 generally
corresponding to the first angle 360 and second angle 362,
respectively, of shape element 354. The first and second angles 370
and 372 substantially oppose one another forming a zigzag pattern
within carrier member 304 at portion 350.
[0061] In general, the angle 360 in FIG. 3B should be minimized in
order to make insertion possible, while still providing sufficient
function as a feature to prevent migration. In the example of FIG.
3B, angle 360 is approximately 150 degrees. In certain embodiments,
the angle 360 may be in the range of approximately 160 degrees to
approximately 170 degrees. As such, in certain embodiments, the
angle 360 may be larger than angle 362.
[0062] It is also to be appreciated that the lengths of segment 357
and fixation feature 302 shown in FIGS. 3A-3C are merely
illustrative. In other embodiments, the segment 357 and fixation
feature 302 may be relatively longer than as shown in FIGS. 3A-3C.
The lengths of segment 357 and fixation 302 are generally selected
to provide sufficient offset to enable the fixation feature 302 to
interlock with a wall of the cochlea.
[0063] A surgeon inserts stimulating assembly 318 into cochlea 340
via an opening 374. In particular, the surgeon "pushes" the
stimulating assembly 318 through the opening 374 in the direction
of the apical end of the cochlea 340. When the surgeon ceases to
push the stimulating assembly 318 into the cochlea 340, the
stimulating assembly 318 will have a tendency to migrate in the
direction of the opening 374. This tendency may be the result of
internal forces within the stimulating assembly 318 and/or
interaction of the stimulating assembly with the cochlea 340 that
place bias force(s) on the stimulating assembly 318 in a proximal
direction. The bias force(s) on stimulating assembly 318 are
represented in FIG. 3C by arrow 377.
[0064] In terms of surgical technique, the surgeon will likely grip
the stimulating assembly 318 at, or as close as possible to, the
fixation feature 302 during most of the insertion. The surgeon may
only grip proximal end 312 in the final stage to push the fixation
feature 302 through the cochlea opening.
[0065] The shape element 354 is formed from a material having
elastic properties such as a nitinol alloy or an elastomeric
polymer such as silicone rubber. As such, the bias forces 377 cause
the zigzag shaped fixation feature 302 (i.e., portion 323 of
surface 214) to be forced against a surface of the cochlea 340 that
is adjacent to the opening 374. In this case, the portion 323 is
substantially parallel to the wall 327 at a point between the
opening 374 and the medial wall 339 of the cochlea 340. The
interaction of fixation feature 302 with the wall 327 will
counteract the bias forces 377 to prevent movement of the
stimulating assembly 318 out of the cochlea through the opening
374.
[0066] Although the fixation feature 302 is configured to prevent
migration of the stimulating assembly 318 out of the cochlea 340,
the fixation feature 302 does not prevent surgical removal of the
stimulating assembly 318. As noted above, the fixation feature 302
is configured such that the bias forces 377 push the fixation
feature against the cochlea wall. However, when a surgeon places a
tensile force on the proximal end 312 of the stimulating assembly
318, the elastic nature of the shape element 354 coupled with the
zigzag shape causes the fixation feature 302 to at least partially
straighten and slide out of the cochlea through the opening 374.
Therefore, the fixation feature 302 is configured to operate with
the cochlea wall to resist/counteract forces from within the
cochlea 340 towards opening 374, but is at least partially
non-resistive to tensile forces placed on the stimulating assembly
318 outside of the cochlea 340.
[0067] It is also to be appreciated that the zigzag shape of
fixation feature 302 shown in FIGS. 3A-3C is merely illustrative.
Fixation feature 302 may have any other shape that, when inserted
in the cochlea 340, causes a region of the upper surface (i.e.,
surface 314) to be substantially parallel to the wall 327 so as to
operate with the cochlea wall 327 to resist/counteract forces from
within the cochlea 340 towards opening 374, while still enabling
removal of the stimulating assembly 318 (i.e., at least partially
non-resistive to tensile forces placed on the stimulating assembly
318 outside of the cochlea 340).
[0068] FIGS. 2A-2C and 3A-3C illustrate fixation features that
comprise a portion of a carrier member and a shape element disposed
within the carrier member. In those embodiments, the shape element
has elastic properties that enable the zigzag shaped fixation
features to be forced against an inner surface of the cochlea
following insertion. It is to be appreciated that the shape element
may take a number of different arrangements. It is also to be
appreciated that the shape element may be omitted in certain
embodiments. Instead, the carrier member, or at least a portion
thereof forming a fixation feature, may be formed to have the
elastic properties and desired zigzag shape.
[0069] FIGS. 4A and 4B illustrate one such example of a stimulating
assembly 418 having a fixation feature 402 formed without a shape
element. FIG. 4A illustrates stimulating assembly 418 prior to
insertion into a recipient's cochlea, while FIG. 4B illustrates
electrode assembly 418 after insertion when the fixation feature
402 is positioned to substantially prevent extrusion/migration of
the stimulating assembly 418 out of the recipient's cochlea
440.
[0070] In this example, the stimulating assembly 418 comprises a
carrier member 404 having a distal end 410 and a proximal end 412.
Distal end 410 terminates in a tip 411 that is adapted to be
implanted furthest into the recipient's cochlea 440. A plurality of
spaced stimulating contacts 448 are mounted or disposed in/on at
least a first surface 414 of the carrier member 404 between the
proximal end 412 and the distal end 410.
[0071] The carrier member 404 includes a second surface 416 that
opposes the first surface 414. Carrier member 404 may be
manufactured from one or more silicone materials and is connected
to a lead region (not shown in FIG. 4A) from the proximal region.
The lead region physically and electrically connects stimulating
lead assembly 418 with a stimulator unit (not shown in FIG.
4A).
[0072] The fixation feature 402 is configured to substantially
prevent extrusion of the stimulating assembly 418 from the cochlea
440. In the embodiment of FIGS. 4A and 4B, the fixation feature 402
is formed by a portion 450 of the carrier member 404. In this
embodiment, the portion 450 is formed from silicone rubber. The
grade of silicone used for portion 450 may have a greater stiffness
than the grade of silicone used for the remainder of the
stimulating assembly 418, which is designed to maximize flexibility
for atraumatic insertion. In other words, different grades of
silicone may be used for the portion 450 and the rest of the
stimulating assembly 418.
[0073] As shown, the fixation feature 402 is, in essence, a
transition region in the stimulating assembly 418 that connects two
offset segments (portions) of the stimulating assembly 418, namely
a proximal or first portion 405. The fixation feature 402 has a
generally zigzag or sinuous shape.
[0074] As shown in FIG. 4B, following insertion of the stimulating
assembly 418 in a recipient's cochlea, the fixation feature 402 is
configured to engage an inner surface (wall) 427 of the cochlea 440
adjacent to an opening 474 (through which the stimulating assembly
418 is inserted) to prevent movement of the stimulating assembly
out of the cochlea through the opening 474. The shape and
mechanical properties of the fixation feature 402 cause a region
423 of surface 416 to abut the wall 427 within the cochlea 440. In
this implanted position, the region 423 of surface 416 is
substantially parallel to the wall 427, but is substantially
perpendicular to a central axis 429 of the opening 474. As such,
the fixation feature 402 operates with the cochlea wall 427 to
resist/counteract forces from within the cochlea 440 towards
opening 474.
[0075] It is to be appreciated that the lengths of fixation feature
402 shown in FIGS. 4A and 4B is merely illustrative. In other
embodiments, the fixation feature 402 may be relatively longer than
as shown in FIGS. 4A and 4B. The length of fixation feature 402 is
generally selected to provide sufficient offset to enable the
fixation feature 402 to interlock with a wall of the cochlea.
[0076] A surgeon inserts stimulating assembly 418 into cochlea 440
via the opening 474. The opening 474 may be, for example, the oval
window, round window or other natural or man-made aperture (e.g.,
cochleostomy) in cochlea 240. In particular, the surgeon "pushes"
the stimulating assembly 418 through the opening 474 in the
direction of the apical end of the cochlea 440. In certain
examples, the carrier member 204 includes a second surface 216 that
opposes the first surface 214. The carrier member 204 may have, for
example, a circular, oval, or other cross-sectional shape. As such,
"opposing surfaces" refers to the fact that at least a portion of
each of the surfaces 214 and 216 faces in substantially opposing
directions from one another. Carrier member 204 may be manufactured
from a silicone material and is connected to a lead region (not
shown in FIG. 2A) from the proximal region. The lead region
physically and electrically connects stimulating lead assembly 218
with a stimulator unit (not shown in FIG. 2A).
[0077] In terms of surgical technique, the surgeon will likely grip
the stimulating assembly 418 at, or as close as possible to, the
fixation feature 402 during most of the insertion. The surgeon may
only grip proximal end 412 in the final stage to push the fixation
feature 402 through the cochlea opening.
[0078] When the surgeon ceases to push the stimulating assembly 418
into the cochlea 440, the stimulating assembly 418 will have a
tendency to migrate in the direction of the opening 474. This
tendency may be the result of internal forces within the
stimulating assembly 418 (i.e., elastic nature of the carrier
member 244 and/or the electrical conductors disposed therein)
and/or interaction of the stimulating assembly with the cochlea 440
that place bias force(s) on the stimulating assembly 418 in a
proximal direction. The bias force(s) on stimulating assembly 418
are represented in FIG. 4B by arrow 477.
[0079] Due to the mechanical properties of the fixation feature
402, the bias forces 477 cause the fixation feature 402 (i.e.,
portion 423 of surface 416) to be forced against wall 427 of the
cochlea 440 that is adjacent to the opening 474. In this case, the
portion 423 is substantially parallel to the wall 427 at a point
between the opening 474 and the lateral wall 435 of the cochlea
440. The interaction of fixation feature 402 with the wall 427 of
the cochlea 440 will counteract the bias forces 477 to prevent
movement of the stimulating assembly 418 out of the cochlea through
the opening 474.
[0080] In general, a stimulating assembly remains implanted in a
recipient permanently. However, in certain circumstances, a
stimulating assembly may be removed from a recipient during surgery
(i.e., to reposition the stimulating assembly) or after a period of
time. Although the fixation feature 402 is configured to prevent
migration of the stimulating assembly 418 out of the cochlea 440,
the fixation feature 402 does not prevent surgical removal of the
stimulating assembly 418. More specifically, as noted above, the
fixation feature 402 is configured such that the bias forces 477
force the fixation feature against the cochlea wall. However, when
a surgeon places a tensile force on the proximal end 412 of the
stimulating assembly 418, the mechanical properties and/or shape of
the fixation feature 402 cause the fixation feature 402 to at least
partially straighten and slide out of the cochlea through the
opening 474. Therefore, the fixation feature 402 is configured to
operate with the cochlea wall to resist/counteract forces from
within the cochlea 440 towards opening 474, but is at least
partially non-resistive to tensile forces placed on the stimulating
assembly 418 outside of the cochlea 440.
[0081] It is also to be appreciated that the zigzag shape of
fixation feature 402 shown in FIGS. 4A and 4B is merely
illustrative. Fixation feature 402 may have any other shape that,
when inserted in the cochlea 440, causes a region of the lower
surface (i.e., surface 416) to be substantially parallel to the
wall 427 so as to operate with the cochlea wall 427 to
resist/counteract forces from within the cochlea 440 towards
opening 474, while still enabling removal of the stimulating
assembly 418 (i.e., at least partially non-resistive to tensile
forces placed on the stimulating assembly 418 outside of the
cochlea 440).
[0082] FIG. 4C illustrates an example where the fixation feature
402 is held straight for insertion into a recipient's cochlea by a
sheath 457. As shown, the sheath 457 extends around (i.e.,
partially envelopes) at least the portion 450 and has sufficiently
rigidity to maintain the portion 450 in a relatively straight
configuration for insertion into the recipient's cochlea. The
sheath 457 may be formed from a material that is relatively stiffer
than the material forming portion 450.
[0083] In certain embodiments, the sheath 457 is configured to be
removed during or after insertion to so as to enable the portion
450 to adopt the shape shown in FIG. 4A. For example, the sheath
may be a split tube that supports the portion 450 in a
substantially straight configuration during insertion. The sheath
457 may be removed as the portion 450 passes through opening 474
(FIG. 4B) or may be removed after portion 450 passes through the
opening.
[0084] In other embodiments, the sheath 457 is formed from a
bioresorbable material which softens or dissolves on exposure to
the recipient's body fluid. More specifically, the sheath 457 may
be configured to soften or dissolve upon insertion into the cochlea
so as to enable the portion 450 to adopt the shape shown in FIG. 4A
(i.e., to interlock with the cochlea). In such embodiments, the
bioresorbable material forming the sheath 457 may be selected from,
for example, polyacrylic acid (PAA), polyvinyl alcohol (PVA),
polylactic acid (PLA) and polyglycolic acid (PGA).
[0085] In a still further embodiment, the sheath 457 can be formed
from a shape memory alloy or a heat sensitive material. For
example, the stiffening element can be formed from a
nickel/titanium alloy, or a bimetallic element formed of a laminate
of two different metals, that is shaped to take a straight or
substantially straight configuration at room temperature but bends
into another shape once it is exposed to body temperature.
[0086] It is to be appreciated that the use of sheath 457 with
stimulating assembly 418 is merely illustrative. The sheath 457, or
other sheaths, may be use with other stimulating assemblies
described herein to maintain fixation features in a relatively
straight configuration during insertion into a recipient's
cochlea.
[0087] FIGS. 5A and 5B are side views of an embodiment of an
electrode assembly 518 comprising an expandable fixation feature
502. FIG. 5A illustrates the stimulating assembly 518 and
expandable fixation feature 502 prior to insertion into a
recipient's cochlea, while FIG. 5B illustrates the stimulating
assembly 518 and expandable fixation feature 502 after insertion
into the cochlea.
[0088] Stimulating lead assembly 518 comprises a carrier member 504
having a distal end 510 and a proximal end 512. A plurality of
spaced-apart stimulating contacts 548 is disposed on or in a
carrier member 504. As shown in FIG. 5B, stimulating lead assembly
518 may be implanted into cochlea 540 through an opening 574 in a
cochlea 540. The aperture may be, for example, the oval window,
round window, or a cochleostomy, as described above.
[0089] The expandable fixation feature 502 comprises a portion 550
of carrier member 504 that has a first configuration that enables
the fixation feature 502 to be inserted into a recipient's cochlea
via an opening 574. The portion 550 of the stimulating assembly 518
is configured to swell when exposed to the recipient's bodily fluid
(i.e., the recipient's cochlea fluid). As such, after insertion
into the cochlea, the portion 550 has a second configuration where
the portion engages an inner surface of the cochlea adjacent to the
opening so as to prevent movement of the stimulating assembly 518
out of the cochlea.
[0090] As noted above, the portion 550 is formed from a material
that expands (e.g., swells) upon exposure to the recipient's
cochlea fluid. The remainder of the stimulating assembly 518 is
formed from a polymeric material that does not expand when exposed
to cochlea fluid. In certain embodiments, the entirety of portion
550 is formed from the expandable material, while in other
embodiments only an outer region of the portion 550 is formed from
the expandable material.
[0091] FIGS. 6A and 6B illustrate further embodiments presented
herein where a stimulating assembly 618 comprises an expandable
fixation feature 602 formed by positioning or molding an expandable
material around the outer surface of a carrier member 604. In such
embodiments, the expandable fixation feature 602 has a
pre-insertion thickness and a different post-insertion thickness.
That is, in the pre-insertion configuration of FIG. 6A, the
expandable fixation feature 602 extends from the outer surface of
carrier member 604 by a distance 601. However, in the
post-insertion configuration of FIG. 6B, the expandable fixation
feature 602 has a thickness 603 that is greater than the thickness
601.
[0092] The expandable materials used in the embodiments of FIGS.
5A-5B and 6A-6B may be a biocompatible hygroscopic material such as
soft hygroscopic polymeric or hydrogel material. As an example, the
biocompatible material can be a natural polymer such as a
glycosaminoglycan, for example, hyaluronic acid, chondroitin
sulfate, and cellulose or a synthetic polymer, such as a hydrogel,
poly(vinyl alcohol), poly(2-hydroxyethylmethylacrylate), and
polyethylene oxide. Other possible materials include
Polydimethylsiloxane (PDMS) elastomers, collagen, chitosan,
alginate, a poly(acrylonitrile)-based hydrogel, poly(ethylene
glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer
network (IPN) hydrogel, polyethylene oxide-polybutylene
terephthalate (PEO-PBT), a hyaluronic acid based hydrogel,
high-molecular-weight polyacrylic acid (PAA) as a filler in a
Silastic matrix, PVA/chitosan blends, poly(hydroxy
ethylmethacrylate), poly(ethylene glycol) (PEG) hydrogels,
tetraethylene glycol diacrylate, polyethylene glycol methacrylate
(PEGMA), cross-linkable (2-hydroxyethyl methacrylate) (HEMA), and
poly(methyl acrylate-co-hydroxyethyl acrylate) hydrogel. The use of
a soft polymeric material, which may stretch and thin, may be
beneficial should the stimulating lead assemblies 518/618 need to
be surgically explanted.
[0093] FIG. 7 illustrates a further embodiment of the present
invention in which a plurality of expandable fixation features are
provided. More specifically, FIG. 7 illustrates a stimulating
assembly 718 comprising three expandable fixation features 702(A),
702(B), and 702(C). For ease of illustration, the three expandable
fixation features 702(A), 702(B), and 702(C) are each shown in a
deployed or expanded (i.e., post-insertion) configuration. The
expandable fixation features 702(A), 702(B), and 702(C) may formed
by positioning or molding an expandable material around the outer
surface of a carrier member 704 (as in the embodiments of FIGS. 6A
and 6B), or may comprise a portion of the carrier member 704 (as in
the embodiments of FIGS. 7A and 7B).
[0094] In general, the three expandable fixation features 702(A),
702(B), and 702(C) are present to provide a surgeon with the
ability to select one of several final positions for the
stimulating assembly 718. Each of the three expandable fixation
features 702(A), 702(B), and 702(C) is configured to be inserted
into a recipient's cochlea and expand into an expanded
configuration. In the expanded configuration, each of the
expandable fixation features 702(A), 702(B), and 702(C) can operate
with an inner surface of the cochlea to prevent migration of the
stimulating assembly 718 from the cochlea.
[0095] FIGS. 5A-5B, 6A-6B, and FIG. 7 illustrate embodiments in
which the expandable fixation features 502 and 602 expand
substantially radially within the recipient's cochlea to form an
annular flange. It is to be appreciated that the annular flange
shape of FIGS. 5A-5B and 6A-6B is merely illustrative and that
other shapes may be used in embodiments of the present invention
(e.g., a toroidal shape).
[0096] FIGS. 8A-8C are side views of a stimulating assembly 818
having alternative fixation features in accordance with embodiments
of the present invention. FIG. 8A illustrates stimulating assembly
818 prior to insertion into a recipient's cochlea, while FIG. 8B
illustrates electrode assembly 818 during insertion into a
recipient's cochlea. FIG. 8C illustrates electrode assembly 818
after insertion when the fixation features are positioned to
substantially prevent extrusion/migration of the stimulating
assembly 818 out of the recipient's cochlea.
[0097] In the embodiments of FIGS. 8A-8C, the stimulating assembly
818 comprises a carrier member 804 having a distal end 810 and a
proximal end 812. A plurality of stimulating contacts 848 is
disposed in the carrier member 804. As shown, the stimulating
assembly 818 is configured to be inserted through an opening 874 in
a recipient's cochlea 840.
[0098] The stimulating assembly 818 also comprises a compressible
fixation feature 802 extending around a circumference of a proximal
end of the carrier member 804. For ease of illustration, the
fixation feature 802 is shown in cross-section.
[0099] The fixation feature 802 comprises a circumferential
flexible flange or collar formed from, for example, silicone,
polyimide or PEEK, mesh (e.g., Dacron), or resilient or elastic
metals. In certain examples, the non-silicone materials may form
the body of the fixation feature 802, but are encased in a thin
layer of silicone.
[0100] Prior to insertion, the fixation feature 802 extends out
from the surface of the carrier member 804. However, the fixation
features 802 have a shape and/or orientation so as to be compressed
during insertion into a recipient's cochlea. More specifically FIG.
8B illustrates stimulating assembly 818 as surgeon pushes the
stimulating assembly through an opening 874 in a recipient's
cochlea 840. As the fixation feature 802 passes through the opening
874, the fixation feature bends backwards (i.e., in a proximal
direction) toward the carrier member 804. That is, the walls of the
opening 874 force the fixation feature 802 backwards in the
direction generally shown by arrows 881.
[0101] Furthermore, as shown in FIG. 8C, due to the
resilient/elastic properties of the fixation feature 802, the
fixation feature is configured to return to its pre-insertion
configuration after passing through the opening 874. That is, as
generally shown by arrows 883, the fixation feature 802 "springs"
outward or away from the carrier member 804 to return to the
pre-insertion configuration once the fixation feature is positioned
within the cochlea.
[0102] Similar to the embodiments described above, when the surgeon
ceases to push the stimulating assembly 818 into the cochlea 840,
the stimulating assembly 818 will have a tendency to migrate in the
direction of the opening 874. This tendency may be the result of
internal forces within the stimulating assembly 818 and/or
interaction of the stimulating assembly with the cochlea 850 that
place bias force(s) on the stimulating assembly 818 in a proximal
direction.
[0103] As shown in FIG. 8C, the bias force(s) on stimulating
assembly 818, which are represented in FIG. 8C by arrow 877, cause
the fixation feature 802 to be forced against surfaces 895 of the
cochlea 840 adjacent to the opening 874. In turn, the surfaces 895
place forces on the fixation feature 802 in the distal direction.
The distal force(s) are represented in FIG. 8C by arrows 897.
Although the fixation feature 802 is configured to bend backwards
(i.e., in the proximal direction the carrier member 804), the
fixation feature has sufficient rigidity such that they do not bend
in the forward (distal) direction in response to the forces 897. As
such that the engagement of the fixation feature with the surfaces
895 will counteract the bias forces 877 to prevent movement of the
stimulating assembly 818 out of the cochlea through the opening
874.
[0104] Although the fixation feature 802 is configured to prevent
migration of the stimulating assembly 818 out of the cochlea 840,
the fixation feature 802 does not prevent surgical removal of the
stimulating assembly 818. As noted above, the fixation feature 802
is configured such that the bias forces 877 push the fixation
feature 802 against the cochlea wall and the fixation feature 802
has sufficient rigidity to resist bending in the forward direction.
However, when a surgeon places sufficient tensile force on the
proximal end 812 of the stimulating assembly 818 the fixation
feature 802 may bend forward as it passes through the opening 874.
Therefore, the fixation feature 802 is configured to operate with
the cochlea wall to resist/counteract forces from within the
cochlea 840 towards opening 874, but is non-resistive to tensile
forces placed on the stimulating assembly 818 outside of the
cochlea 840.
[0105] FIGS. 8A-8C illustrate a specific arrangement that uses
compressible fixation features in the form of a single compressible
flange. It is to be appreciated that other arrangements are within
the scope of the present invention. For example, in alternative
embodiment a two opposing flanges may be disposed on opposing sides
of carrier member and operate substantially the same as described
with reference to the flange of FIGS. 8A-8C. In other embodiments,
more than two flanges may be used.
[0106] FIG. 9 illustrates a further embodiment of the present
invention in which a plurality of compressible fixation features
are provided. More specifically, FIG. 9 illustrates a stimulating
assembly 918 comprising three compressible fixation features 902,
903, and 905. Each set 902, 903, and 905 comprises a
circumferential flange configured as described above with reference
to FIGS. 8A-8C.
[0107] In general, the three compressible fixation features 902,
903, and 905 are present to provide a surgeon with the ability to
select one of several final positions for the stimulating assembly
918. Each of the three compressible fixation features 902, 903, and
905 are configured to be compressed during insertion to a
recipient's cochlea and return to their original configuration
thereafter. In the expanded configuration, each compressible
fixation feature 902, 903, and 905 can operate with an inner
surface of the cochlea to prevent migration of the stimulating
assembly 918 from the cochlea.
[0108] The invention described and claimed herein is not to be
limited in scope by the specific preferred embodiments herein
disclosed, since these embodiments are intended as illustrations,
and not limitations, of several aspects of the invention. Any
equivalent embodiments are intended to be within the scope of this
invention. Indeed, various modifications of the invention in
addition to those shown and described herein will become apparent
to those skilled in the art from the foregoing description. Such
modifications are also intended to fall within the scope of the
appended claims.
* * * * *