U.S. patent application number 14/193243 was filed with the patent office on 2014-06-26 for device and accessories for limiting flexion.
This patent application is currently assigned to Simpirica Spine, Inc.. The applicant listed for this patent is Simpirica Spine, Inc.. Invention is credited to Ian Bennett, Louis Fielding, Hugues Malandain, Anand Parikh, Jeffrey Schwardt, Eller Torres, IV.
Application Number | 20140180340 14/193243 |
Document ID | / |
Family ID | 45928438 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140180340 |
Kind Code |
A1 |
Fielding; Louis ; et
al. |
June 26, 2014 |
DEVICE AND ACCESSORIES FOR LIMITING FLEXION
Abstract
A device may be used to limit flexion of the spine without
substantially limiting extension of the spine. Various accessories,
instruments, and methods may be used to help deploy the flexion
limiting device, manipulate, and adjust it.
Inventors: |
Fielding; Louis; (San
Carlos, CA) ; Parikh; Anand; (San Francisco, CA)
; Torres, IV; Eller; (Tracy, CA) ; Bennett;
Ian; (San Francisco, CA) ; Malandain; Hugues;
(Mountain View, CA) ; Schwardt; Jeffrey; (Palo
Alto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Simpirica Spine, Inc. |
San Carlos |
CA |
US |
|
|
Assignee: |
Simpirica Spine, Inc.
San Carlos
CA
|
Family ID: |
45928438 |
Appl. No.: |
14/193243 |
Filed: |
February 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13267394 |
Oct 6, 2011 |
8696710 |
|
|
14193243 |
|
|
|
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61390459 |
Oct 6, 2010 |
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Current U.S.
Class: |
606/279 |
Current CPC
Class: |
A61B 17/7053 20130101;
A61B 17/7068 20130101; A61B 17/82 20130101; A61B 17/842 20130101;
A61B 17/8869 20130101; A61B 17/8894 20130101; A61B 17/708
20130101 |
Class at
Publication: |
606/279 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. A method for adjusting tension in a surgical tether structure,
said method comprising: providing an implantable surgical tether
structure having a tether and a locking mechanism coupled thereto;
inserting a portion of the tether into the locking mechanism;
tightening the tether structure by actuating a tightening
instrument thereby pulling the tether through the locking
mechanism; maintaining tension in the tether structure with a
braking component frictionally coupled to the tightening
instrument; and locking the tether into the locking mechanism by
actuating a locking instrument thereby drawing the tether into the
locking mechanism, and wherein the braking component permits
retraction of the tether into the locking mechanism during
actuation of the locking mechanism while maintaining tension in the
tether structure.
Description
CROSS-REFERENCE
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/267,394 now U.S. Pat. No. ______ (Attorney
Docket No. 41564-716.201) filed Oct. 6, 2011, which is a
non-provisional of, and claims the benefit of U.S. Provisional
Patent Application No. 61/390,459 (Attorney Docket No.
41564-716.101) filed Oct. 6, 2010; the entire contents of which are
incorporated herein by reference.
[0002] This application is related to the following co-pending
patent application Ser. Nos. 12/479,016 and 13/037,039; the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention generally relates to medical methods
and apparatus. More particularly, the present invention relates to
orthopedic internal fixation such as methods, devices, and
accessories for restricting spinal flexion in patients having back
pain or for providing fracture fixation in long bone and
trochanteric fractures or other orthopedic applications where a
tether may be employed.
[0005] A major source of chronic low back pain is discogenic pain,
also known as internal disc disruption. Patients suffering from
discogenic pain tend to be young, otherwise healthy individuals who
present with pain localized to the back. Discogenic pain usually
occurs at the discs located at the L4-L5 or L5-S1 junctions of the
spine. Pain tends to be exacerbated when patients put their lumbar
spines into flexion (i.e. by sitting or bending forward) and
relieved when they put their lumbar spines into extension (i.e. by
standing or arching backwards).
[0006] Flexion and extension are known to change the mechanical
loading pattern of a lumbar segment. When the segment is in
extension, the axial loads borne by the segment are shared by the
disc and facet joints (approximately 30% of the load is borne by
the facet joints). In flexion, the segmental load is borne almost
entirely by the disc. Furthermore, the nucleus shifts posteriorly,
changing the loads on the posterior portion of the annulus (which
is innervated), likely causing its fibers to be subject to tension
and shear forces. Segmental flexion, then, increases both the loads
borne by the disc and causes them to be borne in a more painful
way. Discogenic pain can be quite disabling, and for some patients,
can dramatically affect their ability to work and otherwise enjoy
their lives.
[0007] Pain experienced by patients with discogenic low back pain
can be thought of as flexion instability, and is related to flexion
instability manifested in other conditions. The most prevalent of
these is spondylolisthesis, a spinal condition in which abnormal
segmental translation is exacerbated by segmental flexion. The
methods and devices described should as such also be useful for
these other spinal disorders or treatments associated with
segmental flexion, for which the prevention or control of spinal
segmental flexion is desired. Another application for which the
methods and devices described herein may be used is in conjunction
with a spinal fusion, in order to restrict motion, promote healing,
and relieve pain post-operatively. Alternatively, the methods and
devices described should also be useful in conjunction with other
treatments of the anterior column of the spine, including
kyphoplasty, total disc replacement, nucleus augmentation and
annular repair. General orthopedic or surgical applications are
envisioned where a tether, cable or tape may be employed. An
example is trochanteric fracture fixation in which a cerclage
device is wrapped around the bone and is attached and tightened to
facilitate fracture healing. Similarly, the device may also be used
in conjunction with a cerclage device for the fixation of long bone
fractures.
[0008] Patients with discogenic pain accommodate their syndrome by
avoiding positions such as sitting, which cause their painful
segment to go into flexion, and preferring positions such as
standing, which maintain their painful segment in extension. One
approach to reducing discogenic pain involves the use of a lumbar
support pillow often seen in office chairs. Biomechanically, the
attempted effect of the ubiquitous lumbar support pillow is also to
maintain the painful lumbar segment in the less painful extension
position.
[0009] Current treatment alternatives for patients diagnosed with
chronic discogenic pain are quite limited. Many patients follow a
conservative treatment path, such as physical therapy, massage,
anti-inflammatory and analgesic medications, muscle relaxants, and
epidural steroid injections, but typically continue to suffer with
a significant degree of pain. Other patients elect to undergo
spinal fusion surgery, which commonly requires discectomy (removal
of the disk) together with fusion of adjacent vertebra. Fusion may
or may not also include instrumentation of the affected spinal
segment including, for example, pedicle screws and stabilization
rods. Fusion is not usually recommended for discogenic pain because
it is irreversible, costly, associated with high morbidity, and has
questionable effectiveness. Despite its drawbacks, however, spinal
fusion for discogenic pain remains common due to the lack of viable
alternatives.
[0010] An alternative method, that is not commonly used in
practice, but has been approved for use by the United States Food
and Drug Administration (FDA), is the application of bone cerclage
devices which can encircle the spinous processes or other vertebral
elements and thereby create a restraint to motion. Physicians
typically apply a tension or elongation to the devices that applies
a constant and high force on the anatomy, thereby fixing the
segment in one position and allowing effectively no motion. The
lack of motion allowed after the application of such devices is
thought useful to improve the likelihood of fusion performed
concomitantly; if the fusion does not take, these devices will fail
through breakage of the device or of the spinous process to which
the device is attached. These devices are designed for static
applications and are not designed to allow for dynamic elastic
resistance to flexion across a range of motion. The purpose of bone
cerclage devices and other techniques described above is to almost
completely restrict measurable motion of the vertebral segment of
interest. This loss of motion at a given segment gives rise to
abnormal loading and motion at adjacent segments, which can lead
eventually to adjacent segment morbidity.
[0011] Another solution involves the use of an elastic structure,
such as tethers, coupled to the spinal segment. The elastic
structure can relieve pain by increasing passive resistance to
flexion while often allowing substantially unrestricted spinal
extension. This mimics the mechanical effect of postural
accommodations that patients already use to provide relief.
[0012] Spinal implants using tether structures are currently
commercially available. One such implant couples adjacent vertebrae
via their pedicles. This implant includes spacers, tethers and
pedicle screws. To install the implant, selected portions of the
disc and vertebrae bone are removed. Implants are then placed to
couple two adjacent pedicles on each side of the spine. The pedicle
screws secure the implants in place. The tether is clamped to the
pedicle screws with set-screws, and limits the extension/flexion
movements of the vertebrae of interest.
[0013] Because significant tissue is removed and because of screw
placement into the pedicles, the implant and accompanying surgical
methods are highly invasive and the implant is often irreversibly
implanted. There is also an accompanying high chance of nerve root
damage. Where the tip of the set-screw clamps the tethers, the
tethers may be abraded and may generate particulate debris.
[0014] Other implants employing tether structures couple adjacent
vertebrae via their processes instead. These implants include a
tether and a spacer. To install the implant, the supraspinous
ligament is temporarily lifted and displaced. The interspinous
ligament between the two adjacent vertebrae of interest is then
permanently removed and the spacer is inserted in the interspinous
interspace. The tether is then wrapped around the processes of the
two adjacent vertebrae, through adjacent interspinous ligaments,
and then mechanically secured in place by the spacer or also by a
separate component fastened to the spacer. The supraspinous
ligament is then restored back to its original position. Such
implants and accompanying surgical methods are not without
disadvantages. These implants may subject the spinous processes to
frequent, high loads during everyday activities, sometimes causing
the spinous processes to break or erode. Furthermore, the spacer
may put a patient into segmental kyphosis, potentially leading to
long-term clinical problems associated with lack of sagittal
balance. The process of securing the tethers is often a very
complicated maneuver for a surgeon to perform, making the surgery
much more invasive. And, as previously mentioned, the removal of
the interspinous ligament is permanent. As such, the application of
the device is not reversible.
[0015] More recently, less invasive spinal implants have been
introduced. Like the aforementioned implant, these spinal implants
are placed over one or more pairs of spinous processes and provide
an elastic restraint to the spreading apart of the spinous
processes during flexion. However, spacers are not used and
interspinous ligaments are not permanently removed. As such, these
implants are less invasive and may be reversibly implanted. The
implants typically include a tether and a securing mechanism for
the tether. The tether may be made from a flexible polymeric
textile such as woven polyester (PET) or polyethylenes such as
ultra high molecular weight polyethylene (UHMWPE); multi-strand
cable, or another flexible structure. The tether is wrapped around
the processes of adjacent vertebrae and then secured by the
securing mechanism. The securing mechanism may involve the indexing
of the tether and the strap, e.g., the tether and the securing
mechanism include discrete interfaces such as teeth, hooks, loops,
etc. which interlock the two. Highly forceful clamping may also be
used to press and interlock the tether with the securing mechanism.
Many known implementations can clamp a tether with the tip of a
set-screw, or the threaded portion of a fastener.
[0016] The mechanical forces placed on the spinal implant are often
unevenly distributed towards the specific portions of the tether
and the securing mechanism which interface with each other. These
portions are therefore typically more susceptible to abrasion,
wear, or other damage, thereby potentially reducing the reliability
of these spinal implants as a whole. Other known securing methods
use a screw or bolt to draw other components together to generate a
clamping force. While these methods may avoid the potentially
damaging loads, the mechanical complexity of the assembly is
increased by introducing more subcomponents. Other methods use a
buckle through which the tether is threaded in a tortuous path,
creating sufficient friction to retain the tether. These buckles
generally distribute the load over a length of the tether; although
they may be cumbersome to use and adjust as the tether is required
to be threaded around multiple surfaces and through multiple
apertures. Many of the aforementioned methods involve the use of
several components, which must often be assembled during the
surgical procedure, often within the wound. This adds time,
complexity and risk to the surgical procedure. Additionally,
several tools or instruments may be required to implant and adjust
the device. These instruments or tools can be awkward or difficult
to use and may require the surgeon and an assistant to hold the
tools and manipulate them.
[0017] For the aforementioned reasons, it would be desirable to
provide improved methods and apparatus to implant and secure the
tethers of such spinal implants. In particular, such methods and
apparatuses should be less invasive and should enable the tether to
be more easily, reversibly, repeatably, safely and reliably secured
to an implant by a surgeon, in a surgery setting. Such apparatuses
should be ergonomically designed to so they are easy to manipulated
and can accommodate various anatomies and physician positions.
Additionally, the apparatuses should be easy to use with various
features to ensure that tools are actuated in the proper direction
when used. It would also be desirable if a single surgeon could
operate all the tools without requiring an assistant. At least some
of these objectives will be met by the embodiments disclosed
herein.
[0018] 2. Description of the Background Art
[0019] Patents and published applications of interest include: U.S.
Pat. Nos. 3,648,691; 4,643,178; 4,743,260; 4,966,600; 5,011,494;
5,092,866; 5,116,340; 5,180,393; 5,282,863; 5,395,374; 5,415,658;
5,415,661; 5,449,361; 5,456,722; 5,462,542; 5,496,318; 5,540,698;
5,562,737; 5,609,634; 5,628,756; 5,645,599; 5,725,582; 5,902,305;
Re. 36,221; 5,928,232; 5,935,133; 5,964,769; 5,989,256; 6,053,921;
6,248,106; 6,312,431; 6,364,883; 6,378,289; 6,391,030; 6,468,309;
6,436,0909; 6,451,019; 6,582,433; 6,605,091; 6,626,944; 6,629,975;
6,652,527; 6,652,585; 6,656,185; 6,669,729; 6,682,533; 6,689,140;
6,712,819; 6,689,168; 6,695,852; 6,716,245; 6,761,720; 6,835,205;
7,029,475; 7,163,558; Published U.S. Patent Application Nos. US
2002/0151978; US 2004/0024458; US 2004/0106995; US 2004/0116927; US
2004/0117017; US 2004/0127989; US 2004/0172132; US 2004/0243239; US
2005/0033435; US 2005/0049708; 2005/0192581; 2005/0216017; US
2006/0069447; US 2006/0136060; US 2006/0240533; US 2007/0213829; US
2007/0233096; Published PCT Application Nos. WO 01/28442 A1; WO
02/03882 A2; WO 02/051326 A1; WO 02/071960 A1; WO 03/045262 A1;
WO2004/052246 A1; WO 2004/073532 A1; and Published Foreign
Application Nos. EP0322334 A1; and FR 2 681 525 A1. The mechanical
properties of flexible constraints applied to spinal segments are
described in Papp et al. (1997) Spine 22:151-155; Dickman et al.
(1997) Spine 22:596-604; and Garner et al. (2002) Eur. Spine J.
S186-S191; Al Baz et al. (1995) Spine 20, No. 11, 1241-1244;
Heller, (1997) Arch. Orthopedic and Trauma Surgery, 117, No.
1-2:96-99; Leahy et al. (2000) Proc. Inst. Mech. Eng. Part H: J.
Eng. Med. 214, No. 5: 489-495; Minns et al., (1997) Spine 22 No.
16:1819-1825; Miyasaka et al. (2000) Spine 25, No. 6: 732-737;
Shepherd et al. (2000) Spine 25, No. 3: 319-323; Shepherd (2001)
Medical Eng. Phys. 23, No. 2: 135-141; and Voydeville et al (1992)
Orthop Traumatol 2:259-264.
SUMMARY OF THE INVENTION
[0020] The present invention provides fastening mechanisms,
instruments, and methods for releasably locking an implantable
surgical tether. Exemplary orthopaedic applications include
restricting flexion of at least one spinal segment or securing
broken bones together. More particularly, the provided fastening
mechanisms, instruments, and methods relate to improvements to the
methods and devices of deploying and implanting spinal implants for
the treatment of discogenic pain and other conditions, such as
degenerative spondylolisthesis. Specifically, such deployment and
implantation methods are made less invasive, easier to operate, and
more reliable and reversible by the provided fastening mechanisms
and methods.
[0021] In a first aspect of the present invention, a system for
adjusting tension in a surgical tether comprises an implantable
surgical tether structure having a tether comprising a free end and
a locking mechanism adapted to receive the tether. The locking
mechanism is adapted to lock the free end of the tether in the
locking mechanism when the tether is disposed therein such that the
tether forms a loop that is adapted to encircle an anatomical
structure. The locking mechanism is adapted to allow adjustment of
loop size or tension therein. The system also includes a locking
instrument operably coupled with the locking mechanism. Actuation
of the locking instrument in a locking direction frictionally locks
the tether in the locking mechanism thereby preventing slidable
movement of the tether. The system also includes a tightening
instrument and a braking component. The tightening instrument is
adapted to receive the free end of the tether, and actuation of the
tightening instrument in a tightening direction reduces the loop
size or increases loop tension. Actuation of the tightening
instrument in a loosening direction opposite the tightening
direction increases the loop size or decreases loop tension. The
braking component is coupled to the tightening instrument with
sufficient friction to hold the tightening instrument in a
tightened position after actuation of the tightening instrument in
the tightening direction. The braking component is also coupled to
the tightening instrument with sufficient friction to allow the
tightening instrument to move from the tightened position to a
loosened position when the locking instrument is actuated in the
locking direction.
[0022] The surgical tether structure may comprise a superior loop
segment and an inferior loop segment, and the superior loop segment
may be adapted to be disposed around a superior spinous process,
while the inferior loop segment may be adapted to be disposed
around an inferior spinous process or sacrum. The surgical tether
structure may comprise a first compliance member coupled with the
locking mechanism, and the first compliance member may be adapted
to provide a force resistant to flexion of a spinal segment. The
surgical tether structure may further comprise a second compliance
member that is disposed substantially parallel to the first
compliance member. The first and the second compliance members may
be adapted to be disposed on opposite sides of a spinal midline.
The surgical tether structure may further comprise a second locking
mechanism that is adapted to receive the tether. The second locking
mechanism may be adapted to lock the tether in the second locking
mechanism when the tether is disposed therein, and the second
locking mechanism may be disposed substantially parallel to the
other locking mechanism, each on opposite sides of a spinal
midline.
[0023] The locking mechanism may comprise a roller rotatably
disposed in a housing. The locking mechanism may comprise a slot
passing therethrough, wherein the slot is sized to receive the
tether. The locking mechanism slot may pass through the housing,
and the roller may also comprise a through slot such that the slots
are aligned with one another when the locking mechanism is
unlocked. The slots may be misaligned with one another when the
locking mechanism is locked. Rotation of the roller into a locked
position may draw the tether into the housing from two directions.
The locking mechanism may also include a stop mechanism having an
engaged position and an unengaged position. In the engaged position
the roller may be prevented from rotating, and in the disengaged
position the roller may be free to rotate.
[0024] The locking instrument may comprise an elongate shaft which
may be tubular and may have a distal end adapted to be releasably
coupled with the locking mechanism. The locking instrument may
comprise an inner shaft and an outer shaft. The inner shaft may be
adapted to actuate the locking mechanism, and the outer shaft may
be adapted to actuate a stop mechanism that prevents actuation of
the locking mechanism into an unlocked position. Actuation of the
locking mechanism in the locking direction may draw the tether into
the locking mechanism from two directions.
[0025] The tightening instrument may comprise an elongate shaft
releasably coupled with the tether. The tightening instrument may
comprise a proximal end, a distal end, and a friction element
disposed therebetween. The friction element may be adapted to allow
the braking component to frictionally engage the tightening
instrument. The friction element may comprise a spheroid or a ball.
The tightening instrument may further comprise a handle coupled to
a proximal end of the instrument.
[0026] The braking component may comprise a first arm coupled to a
second arm. The first and second arms may be adapted to flex
outward and biased to return to an inward position which may
frictionally couple the braking component with the tightening
instrument. A first end of the braking component may releasably
engage the locking instrument, and a second end of the braking
component opposite the first end may releasably engage the
tightening instrument. The tightening instrument may comprise a
friction element, and the first and second arms on the second end
of the braking component each comprise an aperture for receiving
the friction element.
[0027] In another aspect of the present invention, a method for
adjusting tension in a surgical tether structure comprises
providing an implantable surgical tether structure having a tether
and a locking mechanism coupled thereto, inserting a portion of the
tether into the locking mechanism, and tightening the tether
structure by actuating a tightening instrument thereby pulling the
tether through the locking mechanism. The method also includes
maintaining tension in the tether structure with a braking
component frictionally coupled to the tightening instrument, and
locking the tether into the locking mechanism by actuating a
locking instrument which draws the tether into the locking
mechanism. The braking component permits retraction of the tether
into the locking mechanism during actuation of the locking
mechanism while maintaining tension in the tether structure.
[0028] The implantable surgical tether structure may comprise a
first and second compliance member adapted to provide a force
resistant to flexion of a spinal segment. The compliance members
may be disposed on opposite sides of a spinal midline and they may
be substantially parallel with one another. The surgical tether
structure may resist flexion of the spinal segment substantially
without restricting extension of the spinal segment. The surgical
tether structure may comprise a superior loop segment and an
inferior loop segment, and the method may further comprise
disposing the superior loop segment around a superior spinous
process, and disposing the inferior loop segment around an inferior
spinous process or a sacrum.
[0029] Inserting a portion of the tether may comprise inserting a
free end of the tether into the locking mechanism. Tightening the
tether structure may comprise rotating the tightening instrument so
that the tether rolls therearound. Tightening the tether structure
may also comprise sliding the tether through a slot in the
tightening instrument.
[0030] Maintaining tension may comprise engaging a pair of arms
around the tightening instrument. The tightening instrument may
comprise a friction element, and engaging the pair of arms may
comprise disposing the arms around the friction element. Actuating
the locking instrument may comprise rotating the locking instrument
and/or rotating a roller in the locking mechanism. The method may
also include engaging a stopping element with the locking mechanism
to prevent actuation thereof.
[0031] In another aspect of the present invention, a system for
indicating status in a surgical tether locking mechanism comprises
an implantable surgical tether structure, a locking instrument, a
stopping instrument, and an indicator plate. The implantable
surgical tether structure has a tether and a locking mechanism
adapted to receive the tether. The locking mechanism is adapted to
lock the tether therein, and the locking mechanism also comprises a
stopping element adapted to prevent over-actuation of the locking
mechanism. The locking instrument is operably coupled with the
locking mechanism such that actuation of the locking instrument in
a locking direction actuates the locking mechanism into a locked
position where the tether is frictionally locked in the locking
mechanism. This prevents slidable movement of the tether. The
stopping instrument is operably coupled with the stopping element.
Actuation of the stopping instrument in an engaged direction
actuates the stopping element into an engaged position which
prevents actuation of the locking mechanism. The indicator plate is
disposed adjacent the locking instrument and the stopping
instrument. The indicator plate has indicia that indicates when the
stopping element is in the engaged position or the disengaged
position. The indicia also indicates when the locking mechanism is
in the locked position or in the unlocked position, and the indicia
indicates the direction to actuate the stopping instrument between
the disengaged and the engaged positions, or the direction to
actuate the locking mechanism between the unlocked and locked
positions.
[0032] The system may further comprise a post extending from the
indicator plate, and the post may be adapted to prevent over
actuation of the stopping instrument beyond the engaged or
disengaged position. The post may also be adapted to prevent over
actuation of the locking instrument beyond the locked and unlocked
position. The indicator plate may comprise a through hole sized to
slidably receive the stopping instrument and the locking
instrument. The through hole may be oblong in order to permit
lateral movement of either the stopping instrument or the locking
instrument when disposed therein. The indicator plate may comprise
a second through hole that is sized to slidably receive a second
stopping instrument and a second locking instrument. The indicator
plate may comprise a figure eight shape, and the indicator plate
may constrain lateral movement of the stopping instrument or the
locking instrument.
[0033] In yet another aspect of the present invention, a method of
adjusting tension and indicating status of a surgical tether
comprises providing an implantable surgical tether structure having
a tether and a locking mechanism, inserting the tether into the
locking mechanism, and coupling a locking instrument with the
locking mechanism. The locking mechanism also has a stopping
element adapted to prevent over actuation of the locking mechanism.
The method also comprises coupling a stopping instrument with the
stopping element, and engaging an indicator plate with the locking
instrument and the stopping instrument. The indicator plate has
indicia that indicate a locked position and an unlocked position of
the locking mechanism, and the indicia also indicate an engaged
position and an unengaged position of the stopping element. In the
locked position the tether is locked in the locking mechanism, and
in the unlocked position the tether is movable through the slot. In
the engaged position the locking mechanism is not actuatable, and
in the unengaged (also referred to as disengaged) position the
locking mechanism is actuatable. The method further comprises
actuating the locking mechanism into either the locked or unlocked
position by actuating the locking instrument until an indicia on
the indicator plate indicates that the locking instrument is in the
locked or unlocked position, and also actuating the stopping
element into either the engaged or disengaged position by actuating
the stopping instrument until an the indicia on the indicator plate
indicates that the stopping instrument is in the engaged or
disengaged position.
[0034] The indicator plate may comprise a through hole, and
engaging the indicator plate may comprise sliding the locking
instrument and the stopping instrument through the through hole.
The locking mechanism may comprise a housing and a roller disposed
therein with the housing having the slot passing therethrough and
the roller having a slot passing therethrough. Actuating the
locking mechanism may comprise rotating the roller so that the
slots are either aligned or misaligned with one another. Actuating
the locking instrument or the stopping instrument may comprise
rotating an elongate shaft. Actuating the stopping element may
comprise rotating the stopping element into engagement with the
locking mechanism or rotating the stopping element to disengage
from the locking mechanism. The method may further comprise
preventing over actuation of the locking mechanism beyond the
locked or unlocked position by constraining actuation of the
locking instrument with a post coupled with the indicator plate.
The method similarly may also include preventing over actuation of
the stopping element beyond the engaged or disengaged position by
constraining actuation of the stopping instrument with a post
coupled with the indicator plate.
[0035] In another aspect of the present invention, an actuator
mechanism for one-way actuation of a medical device comprises an
ergonomically shaped handle designed to fit in a surgeon's hand, a
coil spring disposed in the handle, and an elongate shaft at least
partially disposed in a central channel of the spring which is
coiled to form the central channel. One end of the spring is
coupled with the handle. Rotation of the handle in a first
direction reduces the spring central channel diameter so as to
constrict around the elongate shaft so that handle rotation is
transmitted to the elongate shaft causing rotation of the elongate
shaft. Rotation of the handle in a second direction opposite the
first direction increases the spring central channel diameter
thereby releasing the elongate shaft from the torsion spring so
that handle rotation is not transmitted to the elongate shaft
resulting in no rotation thereof. An end of the spring may form a
protuberance that is captured in an aperture of the handle. The
torsion spring may comprise a welded region that joins the torsion
spring with the handle.
[0036] In still another aspect of the present invention, a method
for one-way actuation of a medical device comprises providing an
actuating mechanism comprising an ergonomically shaped handle
designed to fit in a surgeon's hand, a spring coupled to the handle
and being coiled to form a central channel, and an elongate shaft
disposed in the central channel. The method also includes rotating
the handle in a first direction such that the central channel
diameter reduces and constricts around the elongate shaft thereby
transmitting rotation of the handle to rotation of the elongate
shaft, and rotating the handle in a second direction opposite the
first direction such that the central channel diameter increases so
that the central shaft is disengaged therefrom thereby preventing
transmission of handle rotation to the shaft.
[0037] Rotating the handle in the first direction may lock the
surgical ether disposed on the locking mechanism.
[0038] In another aspect of the present invention, a system for
adjusting tension in a surgical tether comprises an implantable
surgical tether structure having a tether and a locking mechanism.
The locking mechanism is adapted to lock the tether when the tether
is disposed in the locking mechanism. The system also has a tether
tightening instrument adapted to tighten the tether. The tether
tightening instrument comprises a handle having one or more
friction elements, a central channel, and a receiver, and an
elongate shaft having a cross-pin and a slot near a distal end
thereof sized to receive the tether. The handle slidably receives
the elongate shaft in the central channel such that rotation of the
handle is transmitted into rotation of the elongate shaft when the
cross-pin is engaged with the receiver so that the tether is
tightened. Also rotation of the elongate shaft is constrained due
to friction between the elongate shaft and the one or more friction
elements, but rotation of the elongate shaft is still permitted
when sufficient counter torque is applied thereto. The constraint
or rotation of the elongate shaft is provided when the handle
slidably receives the elongate shaft in the central channel and the
cross-pin remains disengaged from the receiver so that the tether
remains at least partially tightened. The elongate shaft may
further comprise a quick release knob for disengaging the elongate
shaft from the handle. The one or more friction elements may
comprise tabs on the elongate shaft or on the handle. The elongate
shaft may have a longitudinal axis and the cross-pin may be
transverse thereto. The slot may slidably receive the tether and
the tether is spooled around the elongate shaft when the elongate
shaft is rotated in a first direction, and wherein the tether is
unspooled from the elongate shaft when the elongate shaft is
rotated in a second direction opposite the first direction.
[0039] In another aspect of the present invention, a method for
tightening a surgical strap comprises providing an implantable
surgical tether structure having a tether and a locking mechanism
with a slot therein. The locking mechanism is adapted to lock the
tether when the tether is disposed in the slot. The method also
includes frictionally engaging a handle with an elongate shaft. The
handle has a central channel and a receiver and the elongate shaft
has a cross-pin and a slot near a distal end of the elongate shaft,
the elongate shaft slidably disposed in the central channel. The
cross-pin is disposed in the receiver, and the handle is actuated
thereby actuating the elongate shaft and tightening the tether.
Disengaging the cross-pin from the receiver still maintains
frictional engagement of the handle with the elongate shaft so as
to prevent rotation of the elongate shaft and maintain tension in
the tether until a counter torque sufficient to overcome the
frictional engagement between the handle and the elongate shaft is
applied thereto thereby allowing release of the tension in the
tether.
[0040] Frictionally engaging the handle with the elongate shaft may
comprise engaging one or more friction tabs on the handle with the
elongate shaft. Actuating the handle may comprise rotating the
handle in a first direction so that the tether spools around the
elongate shaft. The counter torque may be applied when the locking
mechanism is actuated to lock the tether therein.
[0041] These and other embodiments are described in further detail
in the following description related to the appended drawing
figures.
INCORPORATION BY REFERENCE
[0042] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0044] FIG. 1 is a schematic diagram illustrating the lumbar region
of the spine.
[0045] FIG. 1A a schematic illustration showing a portion of the
lumbar region of the spine taken along a sagittal plane.
[0046] FIG. 2 illustrates a spinal implant of the type described in
US Patent Publication No. 2005/0216017A1.
[0047] FIGS. 3A-3B illustrate additional tissue surrounding the
spinous processes.
[0048] FIGS. 4A-4M show an exemplary method of surgically
implanting a spinal device.
[0049] FIG. 5 illustrates an exemplary compliance element.
[0050] FIGS. 6A-6C illustrate the use of an exemplary fastening or
locking mechanism incorporated in the compliance element for
removably locking a tether.
[0051] FIG. 7 is an exploded view of an exemplary fastening or
locking mechanism.
[0052] FIGS. 8A-8B illustrate the use of a tether and a fastening
or locking mechanism in trochanteric fracture fixation.
[0053] FIGS. 9A-9I illustrate use of an indicator plate.
[0054] FIGS. 10A-10E illustrate an exemplary embodiment of a
tightening instrument.
[0055] FIGS. 11A-11K illustrate embodiments of a one-way
driver.
[0056] FIG. 12 illustrates an exemplary tightening instrument.
[0057] FIGS. 13A-13C illustrate an exemplary braking component.
[0058] FIGS. 14A-14C illustrate use of the braking component in
FIGS. 13A-13C with the tightening instrument of FIG. 12.
DETAILED DESCRIPTION OF THE INVENTION
[0059] FIG. 1 is a schematic diagram illustrating the lumbar region
of the spine including the spinous processes (SP), facet joints
(FJ), lamina (L), transverse processes (TP), and sacrum (S). FIG.
1A is a schematic illustration showing a portion of the lumbar
region of the spine taken along a sagittal plane and is useful for
defining the terms "neutral position," "flexion," and "extension"
that are often used in this disclosure.
[0060] As used herein, "neutral position" refers to the position in
which the patient's spine rests in a relaxed standing position. The
"neutral position" will vary from patient to patient. Usually, such
a neutral position will be characterized by a slight curvature or
lordosis of the spine where the spine has a slight anterior
convexity and slight posterior concavity. In some cases, the
presence of the constraint of the present invention may modify the
neutral position, e.g. the device may apply an initial force which
defines a "new" neutral position having some extension of the
untreated spine. As such, the use of the term "neutral position" is
to be taken in context of the presence or absence of the device. As
used herein, "neutral position of the spinal segment" refers to the
position of a spinal segment when the spine is in the neutral
position.
[0061] Furthermore, as used herein, "flexion" refers to the motion
between adjacent vertebrae in a spinal segment as the patient bends
forward. Referring to FIG. 1A, as a patient bends forward from the
neutral position of the spine, i.e. to the right relative to a
curved axis A, the distance between individual vertebrae L on the
anterior side decreases so that the anterior portion of the
intervertebral disks D are compressed. In contrast, the individual
spinous processes SP on the posterior side move apart in the
direction indicated by arrow B. Flexion thus refers to the relative
movement between adjacent vertebrae as the patient bends forward
from the neutral position illustrated in FIG. 1A.
[0062] Additionally, as used herein, "extension" refers to the
motion of the individual vertebrae L as the patient bends backward
and the spine extends from the neutral position illustrated in FIG.
1A. As the patient bends backward, the anterior ends of the
individual vertebrae will move apart. The individual spinous
processes SP on adjacent vertebrae will move closer together in a
direction opposite to that indicated by arrow B.
[0063] FIG. 2 shows a spinal implant of the type described in
related U.S. Patent Publication No. 2005/0216017 A1 (now U.S. Pat.
No. 7,458,981), the entire contents of which are herein
incorporated by reference. As illustrated in FIG. 2, an implant 10
typically comprises an upper strap component 12 and a lower strap
component 14 joined by a pair of compliance members 16. The upper
strap 12 is shown disposed over the top of the spinous process SP4
of L4 while the lower strap 14 is shown extending over the bottom
of the spinous process SP5 of L5. The compliance member 16 will
typically include an internal element, such as a spring or rubber
block, which is attached to the straps 12 and 14 in such a way that
the straps may be "elastically" or "compliantly" pulled apart as
the spinous processes SP4 and SP5 move apart during flexion. In
this way, the implant provides an elastic tension on the spinous
processes which provides a force that resists flexion. The force
increases as the processes move further apart. Usually, the straps
themselves will be essentially non-compliant so that the degree of
elasticity or compliance may be controlled and provided solely by
the compliance members 16.
[0064] FIG. 3A is a side view of the lumbar region of the spine
having discs D separating the vertebral bodies V. The supraspinous
ligament SSL runs along the posterior portion of the spinous
processes SP and the interspinous ligament ISL and multifidus
tendon and muscle M run alongside of and attach to the spinous
processes SP. FIG. 3B is a posterior view of FIG. 3A.
[0065] FIGS. 4A-4M illustrate an exemplary surgical method of
implanting a spinous process constraint such as the embodiment of
FIG. 2. One of the first steps to surgically implant a spinal
implant is to make an incision to access the spinal area of
interest. FIG. 4A shows the lumbar region of back K after an
incision I has been made through the patient's skin. FIG. 4B
illustrates the lumbar region of the spine after the incision I has
been made through the patient's skin. Multifidus muscle and tendon
M have been refracted with refraction tools TR to expose the
spinous processes.
[0066] After the incision has been made, a piercing tool T having a
sharp distal end may be used to access and pierce the interspinous
ligament ISL while avoiding the supra spinous ligament SSL,
creating an interspinous ligament perforation P1 superior of the
first spinous process SSP of interest. This surgical approach is
desirable since it keeps the supra spinous ligament intact and
minimizes damage to the multifidus muscle and tendons and other
collateral ligaments. As shown in FIG. 4C, from the right side of
the spine, tool T accesses and pierces the interspinous ligament
ISL adjacent of the first spinous process SSP of interest. The
distal end of tool T is shown in dotted line. Alternatively, tool T
may access and pierce the interspinous ligament ISL from the left
side instead. The distal end of tool T is coupled with tether 102,
parts of which are also shown in dotted line. In addition to
accessing and piercing the interspinous ligament ISL, piercing tool
T also advances or threads tether 102 through perforation P1. As
shown in FIG. 4D, tool T is then removed, leaving tether 102
positioned through perforation P1. Multifidus tendon and muscle M
is not shown in FIGS. 4C and 4D so that other elements are shown
more clearly.
[0067] FIG. 4E is a posterior view of a section of the spine after
the above steps have been performed. Often times, the distal tip TI
of tool T is detachable. As shown in FIG. 4E, after tool T accesses
and pierces the interspinous ligament ISL with distal tip TI,
distal tip TI is detached from tool T and is left in place in
perforation P1 (shown in dotted line) above the first spinous
process SSP of interest. Tether 102 lags behind tip TI. In some
cases, distal tip TI may fully pierce through interspinous ligament
ISL. In these cases, distal tip TI has passed through the
interspinous ligament ISL while a portion of tether 102 is left in
place in perforation P1.
[0068] After tip TI or a portion of tether TH is left in place in
perforation P1, another tool may couple with tip TI and pull tip TI
such that it drags tether 102a and compliance element 104a to its
appropriate position relative to the spine, as shown in FIG. 4F.
Compliance element 104a is coupled to tether 102a and is used to
provide a force resistive to flexion of spinous processes SR
Compliance element 104a includes a fastening mechanism or fastening
element 106a (also referred to herein as a locking mechanism) and
may further comprise a spring, a tensioning member, a compression
member, or the like. Related compliance members are described in
commonly owned U.S. patent application Ser. No. 12/106,103
(Attorney Docket No. 026398-000410US), the entire contents of which
are incorporated herein by reference.
[0069] The steps of accessing the ISL, piercing the ISL, and
threading tether 102 through a perforation are then repeated for
the opposite, lateral side of the spine for an adjacent spinous
process ISP, inferior of the first superior spinal process SSP of
interest. As shown in FIGS. 4G and 4H, tool T accesses the
interspinous ligament from the left side of the spinal midline and
pierces the interspinous ligament ISL, creating a second
perforation P2 located inferior of a second spinous process of
interest, labeled as inferior spinous process ISP. As shown in FIG.
4G, the inferior spinous process ISP of interest is directly
adjacent to and inferior of the first superior spinous process SSP
of interest. However, it is entirely possible to perform the
described procedure starting with the inferior spinous process ISP
first instead of the superior spinous process SSP, for example,
perforation P2 may be created before perforation P1. It is also
possible that there may be a gap of one or more spinous processes
SP between the spinous processes of interest. Multifidus tendon and
muscle M is not shown in FIGS. 4G and 4H for clarity of the other
shown elements.
[0070] As shown in FIGS. 4H, 4I and 4J, like with the steps shown
in conjunction with the first piercing, tether 102b is pierced
through perforation P2 and left in place along with distal tip TI
of tool T (best seen in FIG. 4I). Another tool such as a pair of
forceps, is then used to grasp distal tip TI to pull tether 102b
and compliance element 104b in place relative to the spine, as
shown in FIG. 4J. Opposing compliance members 104a and 104b on
opposite sides of spinous processes SP are oriented in opposite
directions. Each compliance element 104a, 104b is coupled with
their respective tether 102a, 102b and has a respective fastening
mechanism or fastening element 106a, 106b. Fastening mechanism
106a, 106b are configured to couple with the tether 102a, 102b of
the opposing compliance member 104a, 104b. For example as shown in
FIG. 4K, tether 102a is advanced through compliance member 104b and
is coupled with fastening mechanism 106b while tether 102b is
advanced through compliance member 104a and is coupled with
fastening mechanism 106a. Except for their orientation, compliance
members 104a and 104b are identical. One of skill in the art will
appreciate that the tether may enter and exit the fastening
mechanism in a number of different directions and configurations,
and FIG. 4K merely is one exemplary embodiment.
[0071] Fastening mechanism 106 (also referred to herein as a
locking mechanism) may comprise a driver feature 108. As shown in
FIG. 4L, the driver feature is adapted to receive a rotating driver
tool RT. The driver feature may be a Phillips head, a slotted flat
head, a Torx head, a hex head, or the like. Rotation of tool RT,
which may be either clockwise or counter-clockwise, changes the
configuration of fastening mechanism 106 so as to lock and secure
tether 102 in place. This forms a continuous, multi-component
tether structure or constraint 110 which couples two spinous
processes SP together, as shown in FIG. 4M. Compliance elements
104a, 104b are used to control flexion between spinous processes SP
while tethers 102a, 102b and respective fastening mechanisms 106a,
106b contribute to coupling the spinous processes SP together.
Depending on the location of the perforations P1 and P2 and the
lengths of the compliance elements 104a, 104b, constraint 110 may
couple more than two spinous processes SP together. In general,
compliance elements 104a, 104b comprise spring-like elements which
will elastically elongate as tension is applied through tethers
102a, 102b in an axis generally parallel to the spine. As the
spinous processes or spinous process and sacrum move apart during
flexion of the constrained spinal segment, the superior tether 102a
and inferior tether 102b will also move apart. Compliance elements
104a, 104b each include spring-like elements which will elastically
resist the spreading with a force determined by the mechanical
properties of the spring-like element. Thus, constraint 110
provides an elastic resistance to flexion of the spinal segment
beyond the neutral position. Constraint 110 is often configured to
provide a resistance in the range from 7.5 N/mm to 20 N/mm but the
resistance may be below 3 N/mm or even below 0.5 N/mm. Constraint
110 may also be adjustable in certain dimensions to allow
tightening over the spinous processes or spinous process and sacrum
when the spinal segment is in a neutral position. Other, related
tether embodiments and joining methods are disclosed in U.S. patent
application Ser. No. 12/106,103 (Attorney Docket No.
026398-000410US), U.S. Patent Publication No. 2008/0009866
(Attorney Docket No. 026398-000140US), U.S. Patent Publication No.
2008/0108993 (Attorney Docket No. 026398-000150US), U.S. patent
application Ser. No. 12/106,049 (Attorney Docket No.
026398-000151US) and U.S. Provisional Patent Application No.
60/936,897 (Attorney Docket No. 026398-000400US), each of which,
the entire contents are incorporated herein by reference.
[0072] FIG. 5 illustrates an exemplary embodiment of a spring-like
element 50 of compliance member 104a, 104b. Spring-like element 50
is generally similar to the spring-like elements disclosed in
related, co-assigned U.S. patent application Ser. No. 12/106,103,
the entire contents of which are incorporated herein by reference.
Fastening mechanism 106 having a driver feature 108 is housed
within spring-like element 50. Element 50 comprises a housing
having a helical groove machined in the housing body to form the
spring-like element. Element 50 includes an adjustable tether
connector 52 and a fixed tether connector 54, both of which are
preferably formed integrally or monolithically with the helical
spring structure 51. Typically, the helical spring structure 51 and
coupling portions of both tether connectors 52 and 54 will be
formed from one piece of material, usually being a metal such as
titanium, but optionally being a polymer, ceramic, reinforced glass
or other composite, or other material having desired elastic and
mechanical properties and capable of being formed into the desired
geometry. In a preferred embodiment, spring-like element 50 is
machined or laser cut from a titanium rod. Alternatively, a
suitable polymeric material will be polyetherether ketone (PEEK).
Other features may be built into the spring-like element 50, such
as a stress relief hole 56. Components that compose the adjustable
tether connector may potentially include a roller and a lock-nut;
such components could be made from the same material as the element
50 and adjustable tether connector (e.g. titanium components if the
spring-like element 50 is titanium), or they could be made from a
different material (e.g. injection molded PEEK). The exterior of
the spring-like element 50 may be covered with a protective cover,
such as a sheath fabricated from an elastomer, polymer or other
suitable material. The sheath may be placed over the body of the
spring-like element 50 in order to prevent the intrusion of tissue
and body fluids into the spaces between the turns of the coil and
interior of the element.
[0073] FIG. 6A shows a cross-section of spring-like element 50
having tether 102 locked therein. Tether 102 enters and exits the
housing 58 of fastening mechanism 106 through entry aperture 53
(also referred to herein as a slot), then it passes through central
channel 55 (also referred to herein as a slot), winds around roller
60 and the inside surface of housing 58, and finally exits through
exit aperture 57 (also referred to herein as a slot). Roller 60 is
housed within central channel 55 and is rotatable within tension
element 50. Roller 60 is often substantially cylindrically shaped
but may also have other shapes, for example, an eccentric shape. A
round symmetrical roller will allow the tether 102 to spool evenly
from both the working end and the tail end of the tether 102, while
an eccentrically shaped roller will result in uneven spooling. The
housing 58 of fastening mechanism 106 may be formed integrally with
spring-like element 50 or may be separate.
[0074] During a procedure similar to the one described with
reference to FIGS. 4A-4M, tether 102 is advanced through top
aperture 53, central channel 55 and roller 60, and out through
bottom aperture 57. As shown in FIG. 6B, top aperture 53, central
channel 55, and bottom aperture 57 are aligned so permit easy
passage of tether 102 therethrough. Roller 60 includes two side
apertures 60a, 60b. Prior to the locking of the tether, entry
aperture 53, side apertures 60a and 60b and exit aperture 57 are
all aligned along a common axis. To provide such alignment, roller
60 may include an alignment feature such as a pin or shoulder.
Thus, the roller 60 may be rotated until stopped by the pin or
shoulder, thereby ensuring alignment of all the apertures. Once
tether 102 is advanced through, roller 60 is rotated, via driver
feature 108, thus creating a friction-based interference fit
between roller 60, the inside surface of the housing and the tether
102. As shown in FIG. 6C, the fastening mechanism is rotated
approximately 180.degree. to create this fit. The rotation of the
roller creates a tortuous path for the tether as it passes between
side apertures 60a, 60b. The rotation may retract the working end
102w and tail end 102t of tether 102, sometimes of different
lengths, inward toward roller 60. Offsetting roller 60 from its
axis of rotation by using an eccentrically shaped roller changes
the amount of tether drawn from either side. The roller may also be
rotated a selected amount in order to draw a desired amount of the
tether into the roller. For example, the roller may be rotated from
about 1/4 turn to two or more complete revolutions. Thus, not only
will the locking mechanism secure the tether in position, but it
may also be used to help adjust length or tension of the
tether.
[0075] A friction-based interference fit is advantageous because
the range along the tether to which the mechanism can attach is
continuous, rather than in discrete increments of non-friction
mechanisms such as teeth, hooks, loops, and the like. Thus, forces
between roller 60 and tether 102 are distributed along a longer
portion of tether 102. Additionally, high clamping forces are not
required. Thus, the risk that any specific point of contact will
abrade, wear, or will otherwise be damaged is minimized.
Furthermore, in contrast with other mechanisms that require high
clamping forces, the discrete rotation of a tool is easier and more
repeatable to perform during surgery.
[0076] After the tether is secured, roller 60 is then locked in
place. Various means may be provided to lock roller 60 in place
within housing 58. Roller 60 and/or the inner surface of housing
108 may include male or female threads which engage the two
elements together. The threads may be partially deformed, thereby
helping to secure the roller element with the housing.
Alternatively, a pin 73 may be coupled to housing 58 and roller 60
may comprise a groove adapted to receive pin 73. Another
possibility is that housing 58 may include a flange adapted to
retain roller 60. A set screw as described below with reference to
FIG. 7 may also be provided to lock roller 60 in place. Rotation of
roller 60 in the opposite direction unwinds tether 102 from roller
60 and reduces the interference fit. Roller 60 and/or housing 58
may further include a position indicator, such as detents or
calibration marks, to provide visual, tactile, or audible feedback
to an operator on the relative position of the roller with respect
to housing 58.
[0077] FIG. 7 shows an exploded view of an exemplary fastening
mechanism 70 that uses a locking set screw 75 to lock roller 76 in
place. Roller 71 is generally similar to roller 60. It is
positioned within housing 76 and includes slots 72 for a tether to
be advanced through. Roller 71 has threads 78 on one end that may
be threadably engaged with the housing 76. Roller 71 also has a
shoulder 74 and includes driver features 77. Shoulder 74 is adapted
to be engageable with locking set screw 75 and housing 76. After
roller 71 has been rotated to lock and secure a tether in place,
set screw 75 is set in a position to engage roller 71 with housing
76 and hold it in position relative to housing 76. Shoulder 74, set
screw 75, and/or housing 76 have threads to allow such engagement.
The threads may be partially deformed, thereby further securing the
locking member with the housing. The threads prevent the roller 71
from unrolling thereby allowing release of the tether. Set screw 75
may comprise driver features 79 to allow rotation of the set screw.
Driver features 77 of roller 71 and driver features 79 of set screw
75 each are adapted to receive a tool so as to permit rotation
thereof. The driver features 77, 79 may be a Phillips head, a
slotted flat head, a Torx head, a hex head, or the like. Driver
features 79 of set screw 75 may comprise an aperture large enough
to permit access to roller 71 with a tool that can rotate roller 71
while set screw 75 is engaged with housing 76. An optional end cap
81 having a central aperture 80 may be positioned adjacent the set
screw 75 and welded, bonded or otherwise affixed to the outer rim
82 of the housing 76 so as to capture all the components forming an
inseparable assembly. The aperture 80 is sized to allow access to
rotation of the set screw. This is desirable since it prevents
parts from falling out during use and also provides a device which
is easier to use since assembly is not required. In preferred
embodiments, the assembly may not be disassembled without breaking
or otherwise damaging the device. In other embodiments, the
assembly may be disassembled without damaging the device.
[0078] One advantage of the roller locking mechanisms disclosed
herein is that the tether is not deformed in planes in which it
lies. The tether may be folded or rolled in a plane transverse to
the planes in which it lies. This is desirable since it minimizes
the possibility of twisting or tangling of the tether and also
reduces wear and tear.
[0079] While the exemplary embodiments described above illustrate a
fastening mechanism that is coupled with a spring-like compliance
member, one will appreciate that the fastening mechanism may be
used independently of a spring or other internal fixator. Other
uses may include applications where a tether is secured with a
knot, crimped or the like. These may include cerclage applications
such as in trochanteric fixation in addition to application of a
substantially rigid tether to multiple spinous processes or lamina.
FIGS. 8A-8B illustrate the use of a tether and fastening mechanism
for trochanteric fixation. FIG. 8A shows a tether T wrapped around
the trochanter of a femur F. A fastening mechanism FM releasably
locks one end of the tether T, thereby forming a closed loop around
the trochanter. FIG. 8B highlights the tether wrapped around the
trochanter.
[0080] In addition to the flexion limiting device and locking
mechanism described above, various other accessory items may be
useful for delivering and adjusting the device during the minimally
invasive surgical procedure. The embodiments described below may be
used alone or in combination with any of the tether and locking
mechanisms described here. Several of these are disclosed
below.
[0081] Indicator Plate:
[0082] Actuating the locking mechanism previously described above
is preferably accomplished with a tool having an inner driver (also
referred to as a locking instrument) and an outer driver (also
referred to as a stopping instrument). The inner driver actuates
the roller and an outer driver actuates the locking set screw. The
inner driver is preferably disposed in a central channel of the
outer driver. Because the implant device preferably has two
compliance members, four drivers may be required to secure the
tether in a desired configuration (two inner drivers and two outer
drivers). This can create confusion for an operator as to whether a
driver has been actuated and which direction to actuate the driver.
Thus, it would be desirable to provide an indicator plate that
indicates the direction to actuate the instruments, as well as
indicating how far to actuate the instrument, and locking mechanism
status. FIGS. 9A-9I illustrate exemplary instruments and methods
for implanting the tether, actuating the locking mechanism, and for
monitoring status of the locking mechanism.
[0083] FIG. 9A illustrates a tether 904 coupled to a compliance
member 902 having a locking mechanism 906 for locking the tether
904 in a slot 908 of the locking mechanism. Because the compliance
member can expand and contract during adjustment of loop size or
loop tension, a holding instrument 910 having an elongate shaft 914
with a cradle 912 on the distal end can be used to hold the
compliance member 902 during implantation without undesirable
contraction or expansion of the compliance member. A pin 918 and
slot 916 near the proximal end of the elongate shaft 914 allow a
second adjacent holding instrument with mating pin and slot to be
coupled together. A textured handle on the proximal end of the
elongate shaft 914 allows the handle to be firmly grasped and
manipulated. The elongate shaft preferably has a central channel
920 that allows instruments to be passed therethrough for access to
the locking mechanism 906.
[0084] FIG. 9B illustrates cradling of the compliance member 902 in
the cradle 912. Additional details on the cradle are disclosed in
U.S. patent application Ser. No. 13/037,039 (Attorney Docket No.
41564-709.301), the entire contents of which are incorporated
herein by reference. The compliance member is positioned so that
the locking mechanism is lined up with the central channel 920,
thus instruments may be inserted into the central channel to engage
and actuate the locking mechanism. FIG. 9C illustrates two holding
instruments 910 each having a compliance member 902 disposed on
opposite sides of the spinal segment midline with a portion of the
tether 904 passing through the interspinous ligament and disposed
over a superior surface of a superior spinous process, and another
portion of tether 904 passing through the interspinous ligament and
disposed over an inferior surface of an inferior spinous process
using the methods described previously above. The two holding
instruments are coupled together near their proximal ends because
the pin 918 on one instrument is received in the slot 916 on the
adjacent instrument, and similarly the pin on the other instrument
is received in the corresponding slot in the first instrument. The
two holding instruments are then disposed vertically and
substantially parallel with one another. The compliance members are
also substantially parallel with one another and disposed on
opposite sides of the spinal midline.
[0085] An indicator plate is shown in FIG. 9D that facilities
actuation of the locking mechanisms. The indicator plate is
generally a flat planar plate having at least one and preferably
two through holes 928 for receiving the instruments for actuating
the locking mechanism. The through holes 928 may be round or
another shape sized to receive the instruments. In this embodiment,
the holes are oblong in order to receive the actuating instruments
and to allow them to move laterally within the hole in order to
accommodate various anatomies such as spinal midline thickness. A
central post 903 extends outward from the plate and serves as a
stop to prevent overactuation of the locking mechanism as will be
explained in greater detail below. The indicator plate also
includes a first indicator 922 and a second indicator 926. The
first indicator is preferably a lock symbol L which indicates when
various parts of the locking mechanism are in a locked, tightened,
or otherwise engaged position, and the second indicator 926 is
preferably an unlocked symbol U which indicates when various parts
of the locking mechanism are in an unlocked, loose, or otherwise
disengaged position. An actuation indicator 924 also indicates the
direction of actuation to actuate the locking mechanism from the
unlocked to locked position. The indicator plate may be machined or
molded from a polymer or a metal or other material, and the indicia
may be printed thereon or laser etched into the plate.
[0086] FIG. 9E illustrates the indicator plate 921 slidably
disposed over both the elongate shafts of both holding instruments
910. This helps stabilize the instruments by constraining their
movement. In FIG. 9F an inner driver 962, and an outer driver 906
are slidably disposed in the central channel of each of the holding
instruments until their distal ends engage the locking mechanism in
a compliance member 902. The inner driver 962 is also slidably
disposed in the outer driver 960. Once the inner and outer drivers
are engaged with the locking mechanism, a flag 964 (also referred
to herein as a wing) on the outer driver and a flag 966 on the
inner driver will be aligned with the unlocked symbol U on the
indicator plate. One locking mechanism will be locked first by
rotating the inner driver in a clockwise direction so that its flag
970 moves from the unlocked U to the locked position L. This
actuates the roller which draws tether into the locking mechanism
from two directions as described above, creating the friction fit
which locks the tether in the locking mechanism. The outer driver
is then actuated by rotating it clockwise so that its flag 968
moves from the unlocked U to the locked position L. This actuates
the locking set screw (also referred to herein as a stopping
element) and tightens it against the roller, thereby preventing the
roller from moving or unwinding, thus the tether is locked into
position. The outer driver may be referred to as a stopping
instrument since it actuates the locking set screw, which stops or
prevents actuation of the locking mechanism, the inner driver may
be referred to as a locking instrument since it initially actuates
the roller to lock the tether in place. In FIG. 9F the second
locking mechanism on the second compliance member remains unlocked
so that tether tension or loops size may be further adjusted.
Additionally, a tightening tool 940 may be used to take up extra
slack in the tether and tighten loop size or tension. The
tightening tool 940 includes a handle 942 on the proximal end of an
elongate shaft 944 and a slot 950 on the distal end is sized to
receive the tether. Actuation of the tightening tool by rotating it
either clockwise or counterclockwise spools the tether around the
shaft 944 thereby reducing loop size and increasing tether tension,
or by increasing loop size and decreasing tension. The tightening
tool may also include a friction element 946 which is engaged by
bracket 948 (also referred to as a braking clip or braking
component) to hold tension in the tether after it has been
tightened. The friction is sufficient enough to maintain the
tension in the tether without requiring an operator to maintain
torque on the shaft 944, thereby freeing up a surgeon's hand.
Additionally, the friction is still low enough to be overcome when
the inner driver tool is actuated drawing tether from both
directions into the locking mechanism thus requiring that the
tightening tool unwind slightly to allow the tether to be drawn
into the locking mechanism. Additional details on this mechanism
are described in greater detail below.
[0087] FIG. 9G illustrates actuation of the inner driver 962 by
rotating it in a clockwise direction until flag 966 reaches the
locked position L. In some embodiments, the inner driver cannot be
over rotated because post 930 (best seen in FIG. 9D will interfere
with flag 966 and prevent rotation therepast. Actuation of inner
driver 962 draws the tether into the locking mechanism from both
directions locking tether position. As previously mentioned, this
also unwinds a portion of the tether from the tightening tool 940.
In FIG. 9H the outer driver 960 is then actuated by rotating it in
the clockwise direction until its flag 964 is disposed over the
locked position L. Similarly, post 930 (best seen in FIG. 9D)
prevents overactuation of the outer driver due to interference of
the flag 964 with the post 930. Actuation of the outer driver
threadably engages the locking set screw against the roller,
thereby preventing further rotation of the roller. The tether is
therefore locked in position and prevented from further movement by
the set screw which acts as a stopping element or stopping
mechanism. FIG. 9I illustrates both sets of inner and outer drivers
now in the locked position. The tether is adjusted to the desired
tension and/or loop size. The actuating instruments, indicator
plate, and holding instruments may now be removed from the surgical
field and excess tether severed. The procedure is completed with
closure of the incision.
[0088] Tightening Instrument:
[0089] As previously discussed, when a tether tightening instrument
is used to tighten the tether by spooling the tether around a
shaft, the shaft must be held either manually or with another
instrument so that tension is maintained while the locking
mechanism is locked. Additionally, as the locking mechanism is
actuated, the tether is drawn into the locking mechanism from two
directions, thus as the tether is drawn into the locking mechanism,
the tether must be slightly unspooled from the tightening
instrument to ensure that the tether is properly tensioned. Thus, a
surgeon must simultaneously actuate the locking mechanism with one
hand while unspooling tether with another hand. Or, another
instrument must be used to hold and release tension during various
phases of tether adjustment. Thus, it would be advantageous to
provide other tightening instruments which can free the surgeon's
hands and hold or release tether tension as appropriate. FIGS.
10A-10E illustrate an exemplary embodiment of such a tightening
instrument.
[0090] In FIG. 10A the tightening instrument 1002 includes an
elongate shaft 1004 having a proximal end and a distal end. A slot
1006 is near the distal end and is sized to receive the tether such
that rotation of the shaft will spool the tether around the shaft.
A handle 1010 is coupled with the shaft 1004 by sliding the shaft
into a central channel (not seen) in the handle. The shaft may have
a friction fit with the handle, or in preferred embodiments the
handle includes one or more friction tabs 1012 which frictionally
engage the shaft. The handle is engageable and disengageable with
the shaft as indicated by the arrows in FIG. 10A which shows the
handle engaged with the shaft and FIG. 10B shows disengagement of
the handle from the shaft. FIG. 10B also illustrates a cross pin
1014 which is used to help engage the handle with the shaft. Knob
1008 provides an area that is easy to grasp by the operator so that
the handle may be engaged with and disengaged from the shaft. The
cross pin may be press fit, bonded, welded, or otherwise attached
to the shaft and is generally transverse to the longitudinal axis
of the shaft.
[0091] FIG. 10C more clearly illustrates the handle 1010 with
friction tabs 1012 and a receptacle 1016 for the cross pin. FIG.
10D illustrates a cross-section taken along the line A-A in FIG.
10C and more clearly illustrates the receptacle for the cross-pin
and the friction tabs 1012. FIG. 10E illustrates the elongate shaft
more clearly including the slot 1016 for receiving the tether, the
knob 1008, cross pin 1016, and a push pin 1018 for releasing the
shaft from the handle.
[0092] In use, the embodiment of FIGS. 10A-10E is used first to
spool the tether around the shaft thereby adjusting tether tension
or tether loop size. This is accomplished by slidably engaging the
handle with the shaft so that the cross pin is received in the
handle receptacle. Once engaged, rotation of the handle is then
transmitted to the shaft resulting in spooling or unspooling of the
tether. The handle may be rotated clockwise or counter clockwise to
spool the tether. Once the tether has been tensioned to a desired
amount, the handle is disengaged from the shaft by moving the
handle so that the cross pin is released from the receptacle.
Because of friction between the handle and the elongate shaft, the
shaft is prevented from rotating and thus the tether tension will
be maintained without requiring a surgeon to hold the shaft.
Friction between the handle and shaft is enough to prevent release
of the tether tension until the locking mechanism is actuated
creating a counter torque which draws the tether back into the
locking mechanism. This requires that the tether unspool from the
tightening instrument as the tether is drawn into the locking
mechanism, and this force is high enough to overcome the friction
between the handle and shaft thereby allowing unspooling. Thus the
tightening device has a braking system that maintains tether
tension after tension or tether size has been set and releases
tether tension during locking of the tether.
[0093] One-Way Driver:
[0094] As discussed above, an inner driver and an outer driver are
used to actuate the locking mechanism and set screw. Preferably the
locking mechanism is locked by rotating the inner driver in a
clockwise direction and similarly the set screw is tightened by
rotating the outer driver the clockwise direction. Counter
clockwise rotation will loosen the locking mechanism or loosen the
set screw. While these rotation directions are fairly standard, it
nevertheless can cause confusion to an untrained operator.
Additionally, in some situations, counter-clockwise actuation at
the wrong time during the procedure can result in binding of the
tether locking mechanism. Therefore, it is desirable to provide
one-way drivers that can actuate a mechanism. Preferred embodiments
of a one-way driver are described below and they can be used to
actuate the locking mechanism and set screw described above, or
they may be used to actuate other components and mechanisms where
one-way driving is desirable.
[0095] FIG. 11A illustrates an exemplary embodiment of a one-way
driver 1102 having a handle 1104 and an elongate shaft 1106 coupled
to the handle. The handle may be rotated in one-direction resulting
in rotation of the shaft in the same direction. Rotation of the
handle in the opposite direction uncouples the handle from the
shaft such that the shaft does not rotate and thus the shaft will
not rotate with the handle. A flag 1118 is coupled with the shaft
1106 so that as the shaft rotates, the flag 1118 will also rotate
and this can help an operator keep track of the amount of rotation,
especially when combined with an indicator plate such as previously
described above. A distal engagement element 1108 may include
various driver heads that can mate with any number of heads such as
a flat head, Phillips head, Torx, hex, etc. FIG. 11B illustrates a
cross-section taken along the line A-A in FIG. 11A and highlights
the internal components of the one-way driver.
[0096] The handle 1104 includes a central channel 1114 for
receiving a proximal portion of the elongate shaft 1106. A spring
coil 1110 is disposed around the elongate shaft, and one end of the
spring coil is formed so that a pin 1112 extends radially and
laterally outward from the spring coil. The pin 1112 is then
disposed in a hole 1116 in the handle (best seen in FIG. 11C) thus
the coil spring is fixed to the handle. The opposite end of the
spring coil may be fixed to the elongate shaft using methods known
to those of skill in the art. Rotation of the handle in one
direction will correspondingly rotate and tighten the coil spring
against the shaft 1106 thereby resulting in rotation of the shaft.
Rotation of the handle in the opposite direction will loosen the
coil spring and disengage it from the shaft and thus the shaft will
not rotate with the handle.
[0097] FIG. 11C illustrates the handle 1104 with hole 1116 for
receiving the pin 1112, and FIG. 11D illustrates a cross-section
taken along the line B-B in FIG. 11C. FIG. 11E illustrates the coil
spring 1110 with pin 1112. The pin may be formed by bending a
portion of the spring outward or by welding or otherwise joining
the pin with the spring. FIG. 11F illustrates the shaft 1106 with
indicator flag 1118. The proximal end of the shaft has a larger
diameter section to provide a greater surface area over which the
coil spring tighten and grasp the shaft. The material properties
and geometry of the spring may be varied in order to provide
desirable torque and other characteristics of the one-way
driver.
[0098] FIGS. 11G-11K illustrate an alternative embodiment of a
one-way driver. FIG. 11G illustrates a handle 1104 having an end
cap 1120 that is used to help secure the spring to the handle. FIG.
11H illustrates a cross-section of the handle taken along the line
C-C in FIG. 11G in order to illustrate the internal components of
the one-way driver. Similar to the previous embodiment, a coil
spring 1110 is disposed on the handle and rotation of the handle
increases or decreases the spring diameter so as to engage and
disengage the shaft. An end portion of the coil spring has an
enlarged diameter forming a flange 1122 that can be captured
between the handle and the end cap. This couples the handle and
spring so that rotation of the handle tightens and loosens the
spring around the shaft. FIG. 11I illustrates the spring 1110 more
clearly including the enlarged diameter flange section 1122 which
may be formed integrally from the coil spring or a separate section
may be attached to the coil spring at an attachment region 1124
which may be a welded region, adhesive region, threaded region,
press fit region, or other coupling means may be used to join the
flange with the spring. FIG. 11J illustrates a perspective view of
an end of the handle which includes a rim 1126 that helps capture
the flange on the spring as seen in FIG. 11K where the coil spring
fits in a central channel of the handle and the flange rests
against a distal end of the handle and also rests against the rim.
The end cap 1120 is then threadably engaged, press fit or otherwise
attached to the end of the handle thereby capturing the flange and
operably coupling the spring with the handle. Operation of this
embodiment is similar to the embodiment described above. Rotation
of the handle in one direction tightens the spring onto the shaft
so that the shaft will rotate with the handle, and rotation of the
handle in the opposite direction loosens the spring and uncouples
it from the shaft so that the shaft no longer rotates with the
handle.
[0099] Braking Component:
[0100] Another exemplary embodiment that may be used to tighten the
tether and hold tension without requiring an extra set of hands is
illustrated in FIGS. 12-14C. This embodiment also will allow
tension to be automatically released as the locking mechanism is
actuated when the tether is drawn into the locking mechanism from
two directions which requires unspooling of the tether from the
tightening device.
[0101] FIG. 12 illustrates a tightening instrument 1202 which
includes an elongate shaft 1204 having a handle 1210 on the
proximal end of the shaft and a slot 1206 near the distal end of
the shaft. The handle may include texturing 1212 such as knurling,
channels, or other surface features which facilitate grasping by a
surgeon. The slot 1206 is sized to receive the tether such that
when the tightening instrument is rotated, the tether will spool
around the shaft. A friction element 1208, here a spherical ball is
disposed on the shaft and provides a location for coupling the
tightening instrument with a braking component described below. The
size of the friction element, as well as its surface finish may be
adjusted in order to provide the desired amount of friction. When
the tightening instrument is rotated and the tether is spooled
around the shaft, the friction element engages the braking
component with enough friction to prevent the tightening instrument
from rotating and unspooling the tether. Similarly, when the
locking mechanism is actuated which results in tether being drawn
into the locking mechanism, the friction element engages the
braking component with enough friction such that as the tether is
drawn into the locking mechanism, the tether will unspool from the
elongate shaft.
[0102] FIGS. 13A-13C illustrate an exemplary embodiment of a
braking component that can be used with the tightening instrument
in FIG. 12. The braking component includes a pair of straight or
parallel arms 1302 that are coupled together with a rivet, screw,
or other fastener 1310. One end of the arms is bent laterally
outward to form an L-shaped leg 1304. The L-shaped legs provide a
portion of the braking component that can easily grasped by a
surgeon so that the component can be manipulated. For example, a
surgeon may hold onto the legs and press the component into
engagement with a tightening instrument or a holder instrument as
will be described in greater detail below. The opposite end of the
arms includes an arcuate or concave portion which allows that end
to easily snap onto a cylindrical shaft. Holes 1306 near the
L-shaped legs are sized to receive the friction element 1208 of the
tightening instrument. FIG. 13A is a perspective view of the
braking component, while FIG. 13B is a side view, and FIG. 13C is a
top view of the component.
[0103] FIGS. 14A-14C illustrate how the braking component is used
with the tightening tool. FIG. 14A illustrates a perspective view
of the braking component 1301 engaged with the tightening
instrument 1202 and a holding instrument 910 such as the one
described previously. A tether and compliance member with locking
mechanism 902 are coupled with the holding instrument 910. FIGS.
14B-14C are perspective views of the same thing but taken at
different angles.
[0104] The compliance member and locking mechanism 902 are held in
the cradle of the holding instrument 910. The concave portion 1308
of arms 1302 on component 1301 are snapped over the cylindrical
shaft of the holding instrument 910. The snap fit is sufficient to
prevent the component from sliding up and down the shaft or
otherwise randomly disengaging therefrom. The tightening instrument
is then snapped into the other end of the component such that
friction element 1208 is positioned in holes 1306. In use,
tightening instrument 1202 is rotated to spool the tether around
the tightening instrument shaft. Once a desired tension is set, the
operator may release the tightening tool and the friction between
the component and the friction element will prevent unspooling of
the tether from the shaft. When the tether is placed in the locking
mechanism and the locking mechanism actuated, the tether will be
drawn into the locking mechanism and this will automatically cause
rotation and unspooling of the tether from the tightening
instrument. The braking component is also advantageous since it
helps hold the tightening instrument and the holding instrument
upright, and prevents them from falling into the surgical
field.
[0105] While preferred embodiments of the present invention have
been shown and described herein, it will be obvious to those
skilled in the art that such embodiments are provided by way of
example only. Numerous variations, changes, and substitutions will
now occur to those skilled in the art without departing from the
invention. It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. Additionally, while systems with various
components are disclosed, one of skill in the art will also
appreciate that in any of the embodiments disclosed herein,
individual components or may be provided alone, or in combination
or subcombination with any of the other components. It is intended
that the following claims define the scope of the invention and
that methods and structures within the scope of these claims and
their equivalents be covered thereby.
* * * * *