U.S. patent application number 14/821878 was filed with the patent office on 2015-12-03 for skeletal bone fixation mechanism.
This patent application is currently assigned to MUSC Foundation For Research Development. The applicant listed for this patent is MUSC Foundation For Research Development. Invention is credited to Bruce M. FRANKEL, Mark Evald SEMLER.
Application Number | 20150342647 14/821878 |
Document ID | / |
Family ID | 52428344 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150342647 |
Kind Code |
A1 |
FRANKEL; Bruce M. ; et
al. |
December 3, 2015 |
SKELETAL BONE FIXATION MECHANISM
Abstract
A skeletal fixation apparatus may include two or more bodies
that are attached to two or more screws that have been inserted
into vertebral bodies associated with a patient. The apparatus may
also include two or more cylindrical members that are attached to
the bodies to control the movement or alignment of the bodies when
the skeletal fixation apparatus is being installed in the patient.
The apparatus may further include a rod that includes a first
curvature and a second curvature. The first curvature may be
different than the second curvature and may be based on a medical
diagnosis associated with stabilizing the vertebral bodies. The
second curvature may enable the bodies to be immovably fastened to
the rod in a manner that precludes the cylindrical members from
contacting each other or causing a false torque condition to exist
when the skeletal fixation apparatus is installed in the
patient.
Inventors: |
FRANKEL; Bruce M.; (Mount
Pleasant, SC) ; SEMLER; Mark Evald; (Mount Pleasant,
SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MUSC Foundation For Research Development |
Charleston |
SC |
US |
|
|
Assignee: |
MUSC Foundation For Research
Development
Charleston
SC
|
Family ID: |
52428344 |
Appl. No.: |
14/821878 |
Filed: |
August 10, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13957190 |
Aug 1, 2013 |
|
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|
14821878 |
|
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Current U.S.
Class: |
606/262 |
Current CPC
Class: |
A61B 17/7011 20130101;
A61B 17/7013 20130101; A61B 17/7032 20130101; A61B 90/06 20160201;
A61B 2090/066 20160201; A61B 2090/037 20160201; A61B 17/7085
20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 19/00 20060101 A61B019/00 |
Claims
1.-12. (canceled)
13. A method comprising: obtaining parameters associated with a
medical diagnosis in connection vertebral bodies of a patient that
are to be stabilized by installing a skeletal fixation assembly,
the parameters identifying a first curvature of a fixation rod,
associated with the skeletal fixation assembly, to be used to
stabilize the vertebral bodies; identifying, based on obtaining the
parameters, a second curvature is to be included in a segment of
the fixation rod, the second curvature being different than the
first curvature and enabling a first body, associated with skeletal
fixation assembly, to be immovably attached to the segment in a
manner that precludes a first cylindrical member, removably
attached to the first body, from making contact with a second
cylindrical member, associated with the fixation assembly;
modifying the segment of the fixation rod in a manner that includes
the second curvature, based on the identification of the second
curvature; and installing, in the patient, the skeletal fixation
assembly in a manner that includes the modified segment of the
fixation rod.
14. The method of claim 13, where the first body is pivotably
attached to a screw that is inserted into one of the vertebral
bodies.
15. The method of claim 13, were identifying the second curvature
further includes: identifying, based on the parameters, a first
location, associated with one of the vertebral bodies, at which a
screw is to be inserted into the one of the vertebral bodies;
identifying an axis, associated with the first location, that
intersects the fixation rod when the skeletal fixation assembly is
installed in the patient; determining, based on identifying the
axis, a second location, associated with the fixation rod, at which
the axis intersects the fixation rod; and identifying the segment
based on the determination of the second segment.
16. The method of claim 15, where modifying the segment further
includes: identifying a particular axis that is approximately
perpendicular to the axis; and creating the second curvature,
associated with the segment, in a manner that causes a longitudinal
axis, associated with the segment to be approximately parallel with
the particular axis.
17. The method of claim 15, further comprising: identifying, based
on the parameters, a second location, associated with a different
one of the vertebral bodies, at which a particular screw is to be
inserted into the different one of the vertebral bodies;
identifying a particular axis, associated with the second location,
that intersects the fixation rod when the skeletal fixation
assembly is installed in the patient; determining, based on
identifying the particular axis, a third location, associated with
the fixation rod, at which the particular axis intersects the
fixation rod, when the skeletal fixation assembly is installed in
the patient; identifying a particular segment of the fixation rod
to which a second body is to be attached, the second cylindrical
body being removably attached to the second body; identifying a
different axis that is approximately perpendicular to the
particular axis; creating a different second curvature, associated
with the particular segment, in a manner that causes a particular
longitudinal axis, associated with the particular segment, to
approximately align with the different axis; and the second
curvature precluding the second cylindrical member from making
contact with the first cylindrical member or a third cylindrical
member associated with the skeletal fixation assembly when the
skeletal fixation assembly is installed in the patient.
18. The method of claim 13, where the second curvature is in the
same plane as the first curvature.
19. The method of claim 13, where the second curvature is in a
different plane as the first curvature.
20. The method of claim 13, further comprising: modifying a cross
section of the segment in a manner that corresponds to a cross
section used by the first body to attach to the segment, the
modified cross section precluding the fixation rod from rotating
relative to the first body when the first body is immovably
attached to the segment.
21. The method of claim 13, where a length, associated with the
segment, is greater than a width associated with the first
body.
22.-26. (canceled)
Description
BACKGROUND
[0001] Procedures associated with posterior minimally invasive
lumbar spinal fusion often use extended tab screws (e.g., pedicle
screws), screw extension towers, and a rigid fixation rod (e.g., to
which the screw extension towers are immovably fastened)
(hereinafter, a "skeletal fixation assembly") to fixate vertebral
bodies to one another. Fixating the vertebral bodies precludes or
reduces a degree to which the vertebral bodies can change position
and/or orientation relative to each other or relative to another
portion of a spinal column of a patient; thus enabling a portion of
a spine to which skeletal fixation assembly is attached to be
stabilized.
[0002] In the highly lordotic areas of the cervical and lumbosacral
areas of the spinal column, bend radii or arc of the fixation rod
can cause two or more screw extension towers to come into contact
and/or interfere with each other. When such interference occurs,
the certain induced loads (e.g., a compressive force, a torque, a
tension force, a stress, a strain, a sheering force, etc.) may be
imparted to the fixation rod and/or pedicle screw when a body of an
extended screw (to which a screw extension tower is removably
attached) is fastened to the fixation rod (hereinafter referred to
as "false torque" or "a false torque condition"). Additionally, a
false torque condition may exist in regions of exaggerated sagittal
imbalance and kyphotic curves in the cervico-thoracic, and thoracic
spine or other regions with coronal plane deformities. When the
extension towers are removed, the one or more of the loads may be
removed, changed, or released which may enable the fixation rod to
move (e.g., rotate, shift, change location, change orientation,
etc.) relative to the pedicle screw. Such movement may cause the
portion of the spinal column to not be stabilized because the false
torque and resulting movement of the fixation rod may enable the
vertebral bodies to move relative to each other to each other or
another portion of the spine. False torque can also occur with the
use of conventional screws such as mono-axial, and poly-axial
without extension towers in similar fashion as described above.
[0003] FIG. 1 is a conventional skeletal fixation assembly 100
(hereinafter, "conventional assembly 100") of a type known in the
art. As shown in FIG. 1, conventional assembly 100 includes a pair
of screw extension towers 110 (hereinafter together referred to as
"towers 110" and each, a "tower 110"), a pair of pedicle screw
bodies 115 (hereinafter together referred to as "bodies 115" and
each, a "body 115"), and a conventional fixation rod 120.
[0004] Tower 110 may include a rigid generally cylindrical member
that includes a first end that is removably attached to body 115
and a second, opposite end that can be gripped or positioned by a
medical practitioner (e.g., doctor, surgeon, nurse, etc.) to move
and/or align body 115 during a medical procedure in which
conventional assembly 100 is attached to vertebral bodies (e.g.,
shown as vertebrae 1 and vertebrae 2) included in a spinal column
of a patient. The first end may include a frangible mechanism that
allows tower 110 to be detached from body 115 by the medical
practitioner. Body 115 may be made of a rigid U-shaped material to
which tower 110 is removably attached (e.g., to the end
corresponding to the open or top end of the "U"). Body 115 may also
include a pedicle screw (not shown in FIG. 1) that protrudes
through an opening (e.g., in the end corresponding to the closed or
bottom end of the "U") that can be installed and/or screwed into a
vertebrae. Body 115 also includes one or more set screws (not shown
in FIG. 1) that can be used to fasten conventional fixation rod 120
to body 115. Conventional fixation rod 120 may include a rod made
of a rigid material (e.g., a metal or metal allow, composite,
ceramic, hard plastic, etc.) that can be inserted into and/or
fastened to body 115 (e.g., using the setting screw). Conventional
fixation rod 120 may include a predetermined bend radius or arc
(hereinafter, a "medical curvature") based on a medical diagnosis
or procedure performed by the medical practitioner to control the
manner in which the vertebral bodies are to be stabilized.
[0005] When conventional fixation rod 120 is inserted in and
fastened to bodies 115 (e.g., by tightening each setting screw to a
predetermined torque setting), the first ends of towers 110 may
move as the setting screws are tightened causing the first ends of
towers 110 to make contact and/or interfere with each other when
the bend radius or arc of conventional fixation rod 120 is less
than a threshold. Such interference may preclude towers 110 and
bodies 115 from assuming a predetermined position or orientation,
which may impart certain induced loads on conventional fixation rod
120. The induced loads may cause a false torque condition to exist
with respect to conventional assembly 100. Furthermore, the
interference may also, or alternatively, cause conventional
fixation rod 120 to rotate or change position when the setting
screws are tightened which may cause the medical practitioner to
loosen the setting screws, reposition conventional fixation rod 120
to the desired position or orientation, and attempt to retighten
the setting screws. When towers 110 are removed and/or disconnected
from bodies 115 (e.g., as called for by the medical procedure), the
false torque condition may enable bodies 115 and/or conventional
fixation rod 120 to change position or orientation thus precluding
the vertebral bodies from being stabilized or causing the vertebral
bodies to be stabilized in a manner that is not intended by the
medical practitioner.
DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a diagram of a conventional skeletal fixation
assembly;
[0007] FIGS. 2A and 2B are diagrams of the conventional skeletal
fixation assembly of FIG. 1 and an example skeletal fixation
assembly, in which the systems and/or methods described herein may
be implemented, respectively;
[0008] FIGS. 3A and FIG. 3B are diagrams of an example a fixation
rod of FIG. 2B;
[0009] FIG. 4A is a diagram of example components of a conventional
skeletal fixation assembly associated with a false torque
condition;
[0010] FIGS. 4B and FIG. 4C are diagrams of example components of a
skeletal fixation assembly that precludes a false torque
condition;
[0011] FIGS. 5A-5C are diagrams of example attachment segments of a
fixation rod associated with different cross sections;
[0012] FIG. 6 is a flow chart of an example process for creating a
fixation rod for use in a skeletal fixation assembly; and
[0013] FIGS. 7A-7E are diagrams of example stages of formation of a
fixation rod associated with a skeletal fixation assembly.
DETAILED DESCRIPTION
[0014] The systems, methods, technologies, and/or techniques
(hereinafter referred to as the "systems and/or methods"),
described herein, may include a skeletal fixation assembly that is
installed in the patient in a manner that precludes two or more
screw extension towers, associated with the skeletal fixation
assembly, from contacting and/or interfering with each other.
Precluding the screw extension towers from making contact and/or
interfering with each other may enable the skeletal fixation
assembly to be installed on two or more vertebral bodies of a
portion of a spinal column and/or two or more bones or bone
fragments (e.g., in connection with a bone fracture) associated
with the patient without creating a false torque condition. The
installation of the skeletal fixation assembly without creating the
false torque condition may ensure that the vertebral bodies, bones,
and/or bone fragments remain in a fixed position and/or orientation
relative to each other (hereinafter, "stabilized" or a "stabilized
condition") after the extension towers are removed from the
skeletal fixation assembly. Additionally, or alternatively, the
installation of the skeletal fixation assembly without creating the
false torque condition may preclude or reduce certain loads,
unknown to and/or not intended or desired by the medical
practitioner, from being imparted to the vertebral bodies, bones,
and/or bone fragments, and/or pedicle screws associated with the
skeletal fixation assembly. The term patient, as used herein, may
include any human subject or animal subject having a skeletal
structure.
[0015] The systems and/or methods may include a fixation rod that
includes a first bend radius or arc and one or more second bend
radii or arcs. The first bend radius or arc may, for example,
correspond a predetermined medical curvature based on a medical
diagnosis or procedure performed by a medical practitioner to
ensure that that vertebral bodies of a spinal column and/or bone
fragments of a fracture bone associated with a patient are
stabilized. Additionally, or alternatively, the one or more second
bend radii or arcs (hereinafter collectively referred to as "local
curvatures" and each, a "local curvature") may be determined to
ensure that two or more screw extension towers, associated with the
skeletal fixation assembly, do not make contact or interfere with
each other when bodies, to which the screw extension towers are
attached, are fastened to the fixation rod. The local curvatures
may be created at one or more locations of the fixation rod in a
manner that preserves and/or does not change or affect the medical
curvature of the fixation rod. The systems and/or methods may also,
or alternatively increase an axial range of motion that the pedical
screws are free to move or pivot that enables improved and or
easier fixation in spines or bone fractures of patients with severe
and/or complicated curves (e.g., in one or more of the coronal
plane, sagittal plane, or transverse plane). Such improved and/or
easier fixation may occur by enabling the pedical screw bodies (to
which the pedical screws are pivotally attached) to engage or
attach to the fixation rod at one or more fixation points in a
shorter interval that would otherwise be possible. While the
description below describes the systems and methods in the context
of stabilizing a patients vertebral bodies, in an additional or
alternatively implementation, the systems and/or methods may not be
so limited. The systems and/or methods may, for example, be
described in the context of other bones and/or bone fragments
associated with a patient such as stabilizing a first bone fragment
and a second bond fragment associated with a fractured bone within
a patient.
[0016] The systems and/or methods may enable a cross sectional area
of a fixation rod to be created or modified to preclude the
fixation rod from rotating when being fastened to a body associated
with a skeletal fixation assembly. Precluding the rotation of the
fixation rod may eliminate the likelihood of a false torque
condition being created and/or may preclude or reduce certain
loads, unknown to and not intended or desired by the medical
practitioner, from being imparted to the vertebral bodes and/or
pedicle screws associated with the skeletal fixation assembly.
Additionally, or alternatively, the cross sectional area of the
fixation rod may be created or modified at a location that
corresponds to a local curvature of the fixation rod and/or at a
location on the fixation rod at which the body, associated with the
skeletal fixation assembly, is fastened. The cross sectional area
may also, or alternatively, be rotated or clocked about a
longitudinal axis of the fixation rod to ensure that a screw
extension tower does not make contact or interfere with another
screw extension tower associated with the skeletal fixation
assembly.
[0017] FIGS. 2A and 2B are diagrams of conventional assembly 100 of
FIG. 1 that is known in the art and an example skeletal fixation
assembly 200 (hereinafter "assembly 200) in which the systems
and/or methods described herein may be implemented, respectively.
As shown in FIG. 2A, conventional assembly 100 may include
components 110-120 in a manner similar that that described above
with respect to FIG. 1, as well as a pair of pedicle screws 130
(hereinafter collectively referred to as "screws 130" and each, a
"screw 130"). Screw 130 may be rotatably attached to body 115 to
permit screw 130 to freely rotate during installation in bone
tissue of a vertebral body associated with a patient and/or to
permit body 115 and/or tower 110 to swivel about screw 130 during
installation of conventional assembly 100.
[0018] Conventional fixation rod 120 may be associated with a
medical curvature 122 that is predetermined based on a medical
diagnosis from a medical practitioner. Each screw 130 may be
associated with a longitudinal axis (e.g., labeled "Screw Axis" in
FIG. 2A) that intersects conventional fixation rod 120 at or in
proximity to a location on conventional fixation rod 120 at which
body 115 is fastened. Each tower 110 may be associated with a
longitudinal axis (hereinafter referred to as "tower axis 112")
(e.g., tower axis 112-1 for left tower 110 and tower axis 112-2 for
right tower 110). A first screw axis, associated with left-most
screw 130, may intersect tower axis 112-1 to form angle 155-1 and a
second screw axis, associated with right-most screw 130, may
intersect tower axis 112-2 to form angle 155-2. In one example,
conventional fixation rod 120 may cause angle 155-1 and/or angle
155-2 to be greater than a first threshold and/or a combination of
angle 155-1 and 155-2 (e.g., a sum, an average, etc.) be greater
than a second, different threshold, which may cause left-most tower
110 and right-most tower 110 to make contact and/or to interfere
with each other. The contact and/or interference may cause a false
torque condition to exist.
[0019] As shown in FIG. 2B, assembly 200 may include towers 110,
bodies 115, and screws 130, as well as fixation rod 220. The number
of components, illustrated in FIG. 2B, is provided for explanatory
purposes only. In practice, there may be additional components,
fewer components, different components, or differently arranged
components than illustrated in FIG. 2B. Also, in some
implementations, one or more of the components of assembly 200 may
perform one or more functions described as being performed by
another one or more of the components of assembly 200.
[0020] Fixation rod 220 may be made of a material (e.g., a metal or
metal alloy, composite, ceramic, hard plastic, etc.) of sufficient
strength and/or rigidity to stabilize a patient's spine with
assembly 200 is installed in the patient. Fixation rod 220 may
also, or alternatively, include a medical curvature 222 and one or
more local curvatures associated with one or more portions of
fixation rod 220 to which bodies 115 are fastened. Medical
curvature 222 may be predetermined by a medical practitioner based
on a medical diagnosis or determined during the procedure performed
by the medical practitioner.
[0021] A local curvature, to be described in greater detail below
with respect to FIGS. 3A and 3B, may enable body 115 to be
immovably fastened to fixation rod 220 in a manner that causes a
screw axis, associated with body 115, to align with a tower axis
associated with tower 110 to which body 115 is attached. For
example, when the first screw axis, associated with left-most screw
130, aligns with tower axis 112-1, angle 155-1 may be less than the
first threshold. In one example, first screw axis and tower axis
112-1 may align such that angle 155-1 is approximately zero.
Additionally, or alternatively, when the first and second screw
axes, associated with left-most and right-most screws 130,
respectively, align with tower axes 112-1 and 112-2, respectively,
a combination of angles 155-1 and 155-2 (e.g., a sum, an average,
etc.) may be less than the second threshold. In one example, first
screw axis and tower axis 112-1 may align and second screw axis and
tower axis 112-2 may align such that a combination of angles 155-1
and 155-2 is approximately zero.
[0022] FIGS. 3A and FIG. 3B are diagrams of an example fixation rod
220. As shown in FIG. 3A and 3B, fixation rod 220 may include
medical curvature 222 in a manner similar to that described above
with respect to FIG. 2B, as well as a group of local curvatures
305-1, 305-2 and 305-3 (hereinafter together referred to as "local
curvatures 305" and each, a "local curvature 305"). Fixation rod
220 is described below as including a single medical curvature 222
and a group of local curvatures 305 for explanatory purposes.
Additionally, or alternatively, fixation rod 220 may include fewer
local curvatures 305, additional medical curvatures 222 and/or
local curvatures 305, different medical curvatures 222 and/or local
curvatures 305, or differently arranged medical curvatures 222
and/or local curvatures 305. While FIGS. 3A and 3B describe medical
curvature 222 and local curvatures 305 in a single two-dimensional
plane for explanatory purposes, additionally, or alternatively,
medical curvature 222 and/or local curvature 305 may exist as
complex a curvature in three dimensions based on two or more
orthogonal two-dimensional planes (e.g., two or more of the coronal
(or frontal) plane, sagittal (median) plane, transverse (or
horizontal) plane, and/or some other two dimensional plane).
[0023] Local curvature 305 may include a portion of fixation rod
220 associated with a contour or shape that does not conform to
medical curvature 222 and/or which enables body 115 to be fastened
to the portion of fixation rod 220 without causing a false torque
condition. For example, local curvature 305-1 may include a first
contour or shape that enables a first body 115 to be immovably
fastened to a first portion of fixation rod 220, associated with
local curvature 305-1, in a manner that causes a first screw axis,
associated with first body 115, to align with a first tower axis
112 of a first tower 110 to which first body 115 is attached.
Additionally, or alternatively, local curvature 305-2 may include a
second contour or shape that enables a second body 115 to be
immovably fastened to a second portion of fixation rod 220,
associated with local curvature 305-2, in a manner that causes a
second screw axis, associated with second body 115, to align with a
second tower axis 112 of a second tower 110 to which second body
115 is attached. Local curvature 305-3 may include a third contour
or shape that enables a third body 115 to be immovably fastened to
a third portion of fixation rod 220, associated with local
curvature 305-3, in a manner that causes a third screw axis,
associated with third body 115, to align with a third tower axis
112 of a third tower 110 to which third body 115 is attached.
[0024] A combination of the first shape and/or contour, the second
shape and/or contour, and/or the third shape and/or contour (e.g.,
associated with local curvatures 305-1, 305-2, 305-3, respectively
and/or other shapes and/or contour associated with fixation rod
220) may be created in a manner that preserves medical curvature
222 associated with fixation rod 220. Such combination of shapes
and/or countours may, for example, include an average, median,
mean, etc. of a respective radii of curvature (e.g., shown as r1
and r2 for the first two curvatures of FIG. 3A) and/or arc length
(e.g., shown as .theta.1 and .theta.2 for the first two curvatures
of FIG. 3A) for each curvature or bend of fixation rode 220 and/or
a combination of shapes and/or contours associated with sinusoidal,
polynomial, parabolic, hyperbolic, elliptical, and/or other shapes
and/or contours. Additionally, or alternatively, fixation rod 220
may include one or more local curvatures 305 in a manner that
enables medical curvature 222 of fixation rod 220 to be
approximately equal to medical curvature 122 of conventional
fixation rod 120 (e.g., shown as a dashed line in FIG. 3A).
[0025] As shown in FIG. 3B, fixation rod 220 may include a group of
attachment segments 310-1, 310-2 and 310-3 (hereinafter together
referred to as "attachment segments 310" and each, a "attachment
segment 310") that correspond to local curvatures 305-1, 305-2 and
305-3, respectively. Attachment segment 310 may include a portion
of fixation rod 220 to which body 115 is immovably attached (e.g.,
body 115 is precluded from moving relative to attachment segment
310). Attachment segment 310 may also, or alternatively, include a
length that is centered about a screw axis associated with body
115. In one example, attachment segment 310-1 may correspond to a
generally straight portion of fixation rod 220 of sufficient length
(e.g., shown as the shaded area of local curvature 305-1) to
accommodate a width of body 115 to be fastened to attachment
segment 310-1. Additionally, or alternatively, some or all of the
length of attachment segment 310-1 may include a longitudinal axis
(e.g., shown as "Local Axis in FIG. 3B) that does not align with
medical curvature 122 and/or 222. The longitudinal axis may also,
or alternatively, be created in a manner that enables body 115 to
be attached to attachment segment 310-1 such that a screw axis,
associated with body 115, aligns with tower axis 112 associated
with tower 110 to which body 115 is attached. In one example, the
local axis may be approximately perpendicular to the screw axis
and/or tower axis 112. Fixation rod 220 may include one or more
other local curvatures 305 (e.g., local curvature 305-2, 305-3,
etc.) and/or one or more other attachment segments 310 (e.g.,
attachment segment 310-2, 310-3, etc.) to which one or more other
bodies 115 are to be attached in a manner similar to that described
above. Additionally, or alternatively, a first local axis,
associated with attachment segment 310-1, may, for example,
approximately align with a second local axis associated with
attachment segment 310-2 and/or a third local axis associated with
attachment segment 310-3. The approximate alignment of the first
local axis, second local axis, and/or third local axis may cause
tower 110-1 removably attached to a first body 115 to be
approximately parallel to tower 110-2 and/or tower 110-3 removably
attached to a second body 115 and/or third body 115, respectively,
when first body 115, second body 115, and/or third body 115 are
attached to attachment segment 310-1, 310-2 and/or 310-3,
respectively. The approximately parallel towers 110 may preclude
tower 110-1, tower 110-2, and/or tower 110-3 from making contact
with each other.
[0026] FIG. 4A is a diagram of an example portion of conventional
assembly 100 (hereinafter "conventional assembly portion 400")
associated with a false torque condition. As shown in FIG. 4A,
conventional assembly portion 400 may include components 110
through 130 as described above with respect to FIG. 2A.
Additionally, body 115, associated with conventional assembly
portion 400, may include a set screw 405 and a fixation rod saddle
410. Set screw 405 may be made of a rigid material (e.g., metal,
plastic, ceramic, etc.) that includes threads that enable a medical
practitioner to tighten set screw 405 against conventional fixation
rod 120 (as shown by the downward pointing arrow and
clockwise-pointing dashed arrow in FIG. 4A). Saddle 410 may be made
of a rigid material and may include a shape that permits
conventional fixation rod 120 to be seated and held in place when
set screw 405 is tightened (e.g., as shown in the detailed figures
of set screw 405). In one example, set screw 405 may be tightened
to a predetermined setting (e.g., torque setting, a force setting,
etc.), which may cause body 115 to be fastened to conventional
fixation rod 120. When tower 110 interferes with another tower 110,
associated with conventional assembly 100, a false torque condition
may be created (e.g., shown by the dashed curved arrow labeled
False Torque Condition in FIG. 4A) in a manner similar to that
described above with respect to FIG. 1, when set screw 405 is not
flush against conventional fixation rod 120. Additionally, or
alternatively, when set screw 405 is tightened, fixation rod 120
may not seat properly within saddle 410, which may cause saddle 410
and/or screw 130 (e.g., including an approximately spherical head
of screw 130) to become impinged between and/or make contact with
body 115 and/or conventional fixation rod 120 (e.g., shown as the
dashed straight arrow labeled "False Torque Condition"). Such
impingement and/or contact may impart unwanted or unknown loads
into the vertebral bodies and/or bone fragments of a patient and/or
may reduce the range in which body 115, saddle 410 or tower 110 is
free to move and/or pivot relative to screw 130. When the medical
practitioner removes tower 110 from body 115, the interference with
the other tower 110 may be removed, and body 115 may be free to
rotate (e.g., as shown by the clockwise-pointing solid arrow in
FIG. 4A). When body 115 rotates, conventional fixation rod 120 may
not be seated and/or held in place within saddle 410 and/or body
115 may not be fastened to conventional fixation rod 120. In this
example, conventional fixation rod 120 may be free change location
or orientation relative to body 115 and/or rotate about the medical
curvature 122 which may not stabilize vertebral bodies and/or bone
fragments associated with a patient.
[0027] FIGS. 4B and 4C are diagrams of an example portion of
assembly 200 (hereinafter "assembly portion 450") that precludes a
false torque condition from occurring. As shown in FIG. 4B,
assembly portion 450 may include fixation components tower 110,
body 115, screw 130, and fixation rod 220 as described above with
respect to FIG. 2B. Assembly portion 450 may also include set screw
405 and saddle 410 as described in FIG. 4A. Fixation rod 220 may
include attachment segment 310 to which body 115 is immovably
attached when set screw 405 is tightened against fixation rod 220
causing fixation rod 220 to be seated and/or held in place within
saddle 410. In this example, a false torque condition may not exist
because tower 110 does not interfere with another tower 110
associated with assembly 220 and/or because screw 130 is not
impinged between and/or does not make contact with fixation rod 220
and/or body 115. In one example, fixation rod 220 may include a
cross section that is of a particular shape (e.g., circular,
elliptical, etc.) that permits to fixation rod 220 to rotate
relative to body 115 in the event that set screw 405 is not
tightened to the predetermined setting (e.g., a torque setting, a
force setting, etc.) or loosens over time.
[0028] As shown in FIG. 4C, assembly portion 450 may include saddle
410 that permits screw 130 to freely swivel or pivot axially about
the screw axis (as shown by the dashed curved arrow in FIG. 4C).
Such freedom to axially pivot may enable screw 115 to be installed
in the vertebral bodies or bone fragments at a variety of angles
without causing a false torque condition in the patient.
Additionally, or alternatively, the freedom of screw 115 to axially
pivot may allow greater flexibility to install assembly portion 450
in the patient based on the geometry of the vertebral bodies, bone
fragments, or orientation or shape of fixation rod 220.
[0029] FIGS. 5A-5C are diagrams of example attachment segments 310
of fixation rod 220 associated with different cross section. As
illustrated in FIGS. 5A-5C, fixation rod 220 may include attachment
segment 310 associated with a cross section 505. In one example, a
first cross sectional area 505 may correspond to a circular cross
sectional area 505-1 as shown in FIG. 5A. Saddle 410, associated
with body 115, may include an aperture 510 into which fixation rod
220 is inserted and can be seated and/or held in place when set
screw 405 (not shown in FIG. 5A) is tightened against fixation rod
220 to fasten fixation rod 220 to body 115. In one example, a first
aperture 510 may correspond to a circular aperture 510-1 (e.g., as
shown in FIG. 5A) that may enable saddle 410 to receive fixation
rod 220, associated with circular cross sectional area 505-1. The
insertion of fixation rod 220, associated with circular cross
section 505-1, into circular aperture 510-1, associated with saddle
410, may enable fixation rod 220 to be seated and/or held in place
within saddle 410 and/or body 115.
[0030] Additionally, or alternatively, as illustrated in FIG. 5B, a
second cross sectional area 505 may correspond to a hexagonal cross
sectional area 505-2. A second aperture 510 may also, or
alternatively, correspond to a hexagonal aperture 510-2 (e.g., as
shown in FIG. 5B) that may enable saddle 410 to receive fixation
rod 220, associated with hexagonal cross sectional area 505-2. The
insertion of fixation rod 220, associated with hexagonal cross
section 505-2, into hexagonal aperture 510-2, associated with
saddle 410, may enable fixation rod 220 to be seated and/or held in
place within saddle 410 and/or body 115. Additionally, or
alternatively, the combination of hexagonal cross section 505-2 and
hexagonal aperture 510-2 may make fixation rod 220 more resistant
to rotating or twisting within saddle 410 compared with fixation
rod 220, associated with circular cross section 505-1, that is
seated in saddle 405 associated with circular aperture 510-1.
[0031] Additionally, or alternatively, as illustrated in FIG. 5C, a
third cross sectional area 505 may correspond to an oval cross
section 505-3. A third aperture 510 may also, or alternatively,
correspond to an oval aperture 510-3 (e.g., as shown in FIG. 5C)
that may enable saddle 410 to receive fixation rod 220, associated
with oval cross sectional area 505-3. The insertion of fixation rod
220, associated with oval cross section 505-3, into oval aperture
510-3, associated with saddle 410, may enable fixation rod 220 to
be seated and/or held in place within saddle 410 and/or body 115.
Additionally, or alternatively, the combination of oval cross
section 505-3 and oval aperture 510-2 may make fixation rod 220
more resistant to rotating or twisting within saddle 410 compared
with fixation rod 220, associated with circular cross section
505-1, that is seated in saddle 405 associated with circular
aperture 510-1.
[0032] In the discussion above, cross sectional area 505 and/or
aperture 510 are described with respect to a circular, an oval, or
a hexagonal shape for explanatory reasons. Additionally, or
alternatively cross sectional area 505 and/or aperture 510 may
include other cross sections and/or shapes such as, for example, an
elliptical shape, a square shape, a rectangular shape, a triangular
shape, pentagonal shape, etc.
[0033] FIG. 6 is a flow chart of an example process 600 for
creating a fixation rod 220 for use in assembly 200. Process 600
may be performed by a medical practitioner while installing
assembly 200 in a spinal column associated with a patient.
Additionally, or alternatively, some or all of process 600 may be
performed by device and/or or collection of devices separate from,
or in combination with, assembly 200. FIGS. 7A-7E are diagrams of
example stages of formation 700-790 (hereinafter referred to
collectively as "stages 700-790" and individually, as "stage 700,"
"stage 725," "stage 750," "stage 775," or "stage 790"),
respectively, of fixation rod 220 associated with assembly 200.
Some or all of process 600 of FIG. 6 will be described with
references to some or all stages 700-790 of FIGS. 7A-7E,
respectively.
[0034] Assume that a medical practitioner performs a medical
procedure on a patient and determines that a portion of the spinal
column of the patent is to be stabilized skeletal fixation assembly
(e.g., assembly 200 of FIG. 2B). Assume further that the medical
practitioner specifies information and/or parameters associated
with assembly 200 to be used to stabilize the portion of the spinal
column (hereinafter referred to as "medical parameters"). For
example, the medical parameters may include information that
identifies a length and/or a medical curvature 122, associated with
conventional fixation rod 120, to be used to stabilize two or more
vertebral bodies of the spinal column; information identifying one
or more locations on each of the vertebral bodies at which a
respective pedicle screw (e.g., screw 130) can be inserted;
information identifying a width of body 115 to be used to fasten
fixation rod 220; information that specifies a cross section (e.g.,
a shape, cross sectional area, radius, diameter, etc.) of
attachment segment 310 of fixation rod 220; information specifying
an aperture of saddle 410 (e.g., a shape, cross sectional area,
radius, diameter, etc.) associated with body 115; etc. The medical
practitioner may, in one example, enter the parameters into a user
interface displayed by a user device and the user device may
receive the parameters and may store the parameters in a memory
associated with the user device.
[0035] As shown in FIG. 6, process 600 may include obtaining
medical parameters associated with a skeletal fixation assembly and
obtaining a rod based on the medical parameters (block 605), and
determining, based on the parameters, a point on the rod at which a
screw axis intersects the rod (block 610). For example, a medical
practitioner may obtain predetermined parameters, associated with
assembly 200, and may, based on the parameters, identify a location
on a vertebral body in which screw 130 is to be inserted.
Additionally, or alternatively, the medical practitioner may
identify a longitudinal axis, associated with screw 130 (e.g.,
hereinafter referred to as a "screw axis"), when screw 130 is
installed in the vertebral body. The medical practitioner may also,
or alternatively, use one or more known methods to obtain a rod
(e.g., conventional fixation rod 120 or some other rod) that
corresponds to the length and/or medical curvature 122 specified by
the medical parameters. The medical practitioner may determine a
location on conventional fixation rod 120 at which the screw axis
intersects conventional fixation rod 120 (hereinafter the
"intersection point"). The intersection point may be based on a
location and/or orientation of conventional fixation rod 120,
relative to the location on the vertebral body in which screw 130
is to be inserted, in the event that conventional assembly 100 is
attached to the patient.
[0036] Additionally, or alternatively, the steps performed by the
medical practitioner could be performed automatically by a
computing device executing logic and/or a set of instructions
stored in a memory. For example, the medical practitioner may
instruct the computing device to obtain the medical parameters
(e.g., using a pointing device such as a mouse, by pressing one or
more buttons on a keyboard, etc.) and the computing device may,
based on the instruction, retrieve the parameters from the memory.
Additionally, or alternatively, the computing device may identify
the location on the vertebral body in which screw 130 is to be
inserted based on the parameters. The computing device may also, or
alternatively, determine an orientation of screw 130 when inserted
in the vertebral body, may identify the screw axis based on the
orientation of screw 130, and may determine the intersection point
of conventional fixation rod 120.
[0037] Additionally, or alternatively, an axis that is different
than the screw axis may be used to determine the intersection
point, such as when screw 130 is inserted in the vertebral body
and/or bone fragment on an axis that deviates from a vertical axis
at an angle that is greater than a particular threshold (e.g., 20
degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, etc.). In
this example, the axis may be substantially vertical or parallel to
the coronal plane as would be understood by a person skilled in the
art and may intersect a location at which screw 130 is inserted
into the vertebral body or bone fragment.
[0038] As also shown in FIG. 6, process 600 may include identifying
an attachment segment of the conventional fixation rod based on the
intersection point and the medical parameters (block 615). For
example, the medical practitioner may determine a first point and a
second point located on conventional fixation rod 120 based on the
intersection point of the screw axis and a width of body 115 or
some other distance obtained from the medical parameters. As shown
in FIG. 7A, stage 700 may include conventional fixation rod 120
associated with medical curvature 122 and may identify a first
point 710 and a second point 715 located on conventional fixation
rod 120. In one example, first point 710 and second point 715 may
be approximately equal distance from the intersection point of the
screw axis with conventional fixation rod 120. In another example,
first point 710 and second point 715 may not be approximately equal
distance from the intersection point. The distance between first
point 710 and/or second point 715 may be based on a width of body
115 and/or some other distance obtained from the medical parameters
(e.g., a predetermined distance, a predetermined percentage of the
length of conventional fixation rod 120, etc.).
[0039] Additionally, or alternatively, the user device may
automatically determine a location associated with first point 710,
a location associated with second point 715, and/or the distance
between first point 710 and second point 715 based on the
intersection point of the screw axis and the width of body 115
and/or some other distance obtained from the medical
parameters.
[0040] As further shown in FIG. 6, process 600 may include
identifying information associated with a local curvature based on
identifying the attachment segment (block 620). For example, the
medical practitioner may determine a first local axis, associated
with first point 710 and second point 715, that enables attachment
segment 310 to be created to which body 115 can be attached in a
manner that precludes tower 110 (e.g., attached to body 115) from
making contact with and/or interfering with another tower 110
associated with assembly 200. In one example, the first local axis
may be determined in a manner that is approximately perpendicular
to the screw axis and/or that causes the screw axis to be aligned
with tower axis 112 associated with tower 110. Additionally, or
alternatively, the first local axis may be determined in a manner
that causes a first angle (e.g., angle 155-1 of FIG. 2B) between
tower axis 112 to be less than a first threshold (e.g., as
described above with respect to FIG. 2B). Additionally, or
alternatively, the first local axis may be determined in a manner
that causes a combination (e.g., a sum, an average, etc.) of the
first angle and a second angle (e.g., angle 155-2 of FIG. 2B)
between a different screw axis and particular tower axis 112, of a
different tower 110 associated with assembly 200, to be less than a
second threshold.
[0041] Additionally, or alternatively, a user device may execute
logic and/or one or more instructions stored in a memory to
automatically determine the first local axis associated with first
point 710 and second point 715 that enables attachment segment 310
to be created in a manner similar to that described above.
[0042] As shown in FIG. 7B, stage 725 may identify the first local
axis, associated with first point 710 and second point 715, that is
approximately perpendicular to the screw axis. The first local axis
may, for example, intersect conventional fixation rod 120 at first
point 710, but may not intersect conventional fixation rod 120 at
second point 715. In this example, the first local axis may
intersect a third point 720 that is not located on conventional
fixation rod 120. Third point 720 may, for example, be located at
an intersection of the first local axis and an axis, associated
with second point 715, that is parallel to the screw axis. The
first local axis may, therefore, intersect first point 710 that is
located on conventional fixation rod 120 and third point 720 that
is not located on conventional fixation rod 120. The first local
axis may represent a longitudinal axis on which a local curvature
305 and/or attachment segment 310 may be created to form fixation
rod 220 (e.g., as shown in stage 750 of FIG. 7C).
[0043] As shown in FIG. 7C, local curvature 305 and/or attachment
segment 310 may be located at a distance that is closer to a center
point, associated with a bend radii of medical curvature 122, than
conventional fixture rod 120 (hereinafter, referred to as "concave
local curvature 305" or "concave faster portion 310").
[0044] Additionally, or alternatively, as shown in stage 775 of
FIG. 7D, a second local axis may be determined based on second
point 715 that is located on conventional fixture rod 120 and a
fourth point 730 that is not located on conventional fixation rod
120. Fourth point 730 may, for example, be located at the
intersection of the second local axis and an axis, associated with
first point 710, that is parallel to the screw axis. The second
local axis, therefore, may intersect second point 715 that located
on conventional fixation rod 120 and fourth point 730 that is not
located on conventional fixation rod 120. The second local axis may
represent a longitudinal axis on which attachment segment 310 may
be created to form fixation rod 220 (e.g., as shown in stage 790 of
FIG. 7E).
[0045] As shown in FIG. 7E, local curvature 305 and/or attachment
segment 310 may be located at a distance that is further from a
center point, associated with a bend radii of medical curvature
122, than conventional fixture rod 120 (hereinafter, referred to as
"convex local curvature 305" or "convex faster portion 310").
[0046] The medical practitioner may also, or alternatively, record
information associated with concave local curvature 305 and/or
convex local curvature 305 that includes, for example, information
identifying the intersection point, first point 710, second point
715, third point 720, fourth point 730, the first local axis, the
second local axis curvature, etc.; and/or information associated
with convex local curvature 305 including, for example, information
identifying the intersection point, first point 710, second point
715, fourth point 730, the local axis, etc.
[0047] While the description above describes the determination of a
concave and/or convex local curvature and/or attachment segment 310
in a two-dimensional plane (e.g., based on a coronal plane, the
sagittal plane, transverse plane, or some other two-dimensional
plane), the concave and/or convex local curvature 305 and/or
attachment segment 310 may also, or alternatively and in a manner
similar to that described above, be determined in a different
two-dimensional plane; in three-dimensions that includes two or
more two-dimensional planes (e.g., two or more of the coronal
plane, sagittal plane, transverse plane, or some other
two-dimensional plane); and/or based on another coordinate system
(e.g., Cartesian coordinates, cylindrical coordinates, spherical
coordinates, etc.).
[0048] As yet further shown in FIG. 6, process 600 may include
determining a cross section of the attachment segment based on the
medical parameters (block 625). For example, the medical
practitioner may obtain, from the medical parameters, information
associated with a cross section (e.g., a cross sectional shape,
dimensions, etc.) of fixation rod 220 and/or attachment segment
310. Additionally, or alternatively, the medical practitioner may
obtain, from the medical parameters, information associated with
aperture 510 of saddle 410 within body 115 (e.g., information
specifying a shape and/or dimension of aperture 510). Based on the
information associated with aperture 510, the medical practitioner
may determine a cross section and/or dimensions of fixation rod 220
and/or attachment segment 310.
[0049] Additionally, or alternatively, the medical practitioner may
specify whether the cross section is to be clocked in a particular
direction (e.g., clockwise, counter clockwise, etc. about a
longitudinal axis associated with attachment segment 310) to ensure
that towers 110 to not make contact or interfere when fastened to
attachment segment 310.
[0050] As also shown in FIG. 6, process 600 may include creating a
local curvature, associated with the conventional fixation rod,
based on the information associated with the local curvature or
information associated with the cross section (block 630). For
example, the medical practitioner may identify a portion of
conventional fixation 120 between first point 710 (FIG. 7A) and
second point 715 (FIG. 7A) and may cause a longitudinal axis,
associated with the identified portion of conventional fixation rod
120, to align with the first local axis to create concave local
curvature 305 and/or attachment segment 310 (e.g., when a concave
local curvature 305 and/or concave attachment segment 310 is
specified by the medical parameters). Additionally, or
alternatively, the medical practitioner may cause the longitudinal
axis, associated with the identified portion of conventional
fixation rod 120, to align with the second local axis to create
convex local curvature 305 and/or concave attachment segment 310
(e.g., when a convex local curvature 305 and/or attachment segment
310 is specified by the medical parameters). The medical
practitioner may also, or alternatively, cause a cross section of
the attachment segment 310 (e.g., concave or convex) to change to a
particular cross section specified in the medical parameters (e.g.,
a circular, elliptical, hexagonal, oval, pentagonal, octagonal,
etc. cross section).
[0051] In one example, the creation of local curvature 305 and/or
the change in cross section of attachment segment 310 may be
created by the medical practitioner using a mechanical device to
bend and/or reshape the identified portion of conventional fixation
rod 120 and/or to change the cross section. Additionally, or
alternatively, the medical practitioner may insert a conventional
fixation rod 120 and/or some other rod into a device that may
automatically create local curvature 305 and/or change the cross
section of attachment segment 310. Additionally, or alternatively,
fixation rod 220 may be manufactured in a manner that includes
local curvature 305, the cross section specified by the medical
parameters, or a medical bend 222 that conforms to conventional
medical 122 specified by the medical parameters.
[0052] As also shown in FIG. 6, if another local curvature is to be
created (block 635--YES), then process 600 may include determining,
based on another point on the rod at which another screw axis
intersects (block 610). For example, if another local bend 305 is
to be incorporated into fixation rod 220, the medical practitioner
may identify a different location on the vertebral body or another,
different vertebral body at which a particular screw 130 is to be
attached. Additionally, or alternatively, medical practitioner may,
in a manner similar to that described above with respect to block
610, identify a particular screw axis, associated with particular
screw 130, and a different location at which particular screw axis
intersects fixation rod 220. Medical practitioner may also, or
alternatively, cause other local bend 305 to be created and/or
incorporated into fixation rod 220 in a manner similar to that
described above with respect to blocks 615-630.
[0053] As further shown in FIG. 6, if another local curvature is
not to be created (block 635--NO), then process 600 may include
obtaining a fixation rod based on creating the local curvature or
the other local curvature for installation in a skeletal fixation
assembly (block 640). For example, another local curvature 305 is
not to be incorporated into fixation rod 220, then medical
practitioner may obtain fixation rod 220. The medical practitioner
may also, or alternatively, use fixation rod 220 to stabilize the
vertebral body and/or other vertebral body associated with a
patient. In this example, the medical practitioner may install one
or more screws 130 (e.g., screw 130, particular screw 130, etc.)
into the vertebral body and/or the other vertebral body and may
attach, to screws 130, assembly 200 that includes fixation rod 220.
The medical practitioner may fasten one or more bodies 115 to
fixation rod 220 in a manner that precludes one or more towers 110,
to which bodies 115 are attached, from making contact and/or
interfering with each other. Additionally, or alternatively,
fixation rod 220 may prevent a torque condition from being created
by precluding towers 110 from making contact and/or interfering
with each other. The medical practitioner may also, or
alternatively, detach towers 110 from bodies 115. After detaching
towers 110, bodies 115 may remain fastened to fixation rod 220,
which may preclude fixation rod 220 from changing a location and/or
orientation, and/or from twisting or rotating relative to bodies
115. The same can hold true for conventional screws without towers
attached.
[0054] The foregoing description provides illustration and
description, but is not intended to be exhaustive or to limit the
implementations to the precise form disclosed. Modifications and
variations are possible in light of the above disclosure or may be
acquired from practice of the embodiments.
[0055] For example, while a series of blocks have been described
with regard to FIG. 6, the order of the blocks may be modified in
other implementations. Further, non-dependent blocks may be
performed in parallel.
[0056] It will be apparent that systems and methods, as described
above, may be implemented in many different forms of software,
firmware, and hardware in the implementations illustrated in the
figures. The actual software code or specialized control hardware
used to implement these systems and methods is not limiting of the
embodiments. Thus, the operation and behavior of the systems and
methods were described without reference to the specific software
code--it being understood that software and control hardware can be
designed to implement the systems and methods based on the
description herein.
[0057] Further, certain portions, described above, may be
implemented as a component that performs one or more functions. A
component, as used herein, may include hardware, such as a
processor, an ASIC, or a FPGA, or a combination of hardware and
software (e.g., a processor executing software).
[0058] It should be emphasized that the terms
"comprises"/"comprising" when used in this specification are taken
to specify the presence of stated features, integers, steps or
components but does not preclude the presence or addition of one or
more other features, integers, steps, components or groups
thereof.
[0059] Even though particular combinations of features are recited
in the claims and/or disclosed in the specification, these
combinations are not intended to limit the disclosure of the
embodiments. In fact, many of these features may be combined in
ways not specifically recited in the claims and/or disclosed in the
specification. Although each dependent claim listed below may
directly depend on only one other claim, the disclosure of the
embodiments includes each dependent claim in combination with every
other claim in the claim set.
[0060] No element, act, or instruction used in the present
application should be construed as critical or essential to the
embodiments unless explicitly described as such. Also, as used
herein, the article "a" and "an" are intended to include one or
more items and may be used interchangeably with "one" or "more."
Where only one item is intended, the term "one" or similar language
is used. Further, the phrase "based on" is intended to mean "based,
at least in part, on" unless explicitly stated otherwise.
* * * * *