U.S. patent application number 13/310514 was filed with the patent office on 2012-03-29 for spinal midline indicator.
This patent application is currently assigned to SpinalMotion, Inc.. Invention is credited to Ulrich Reinhard Hahnle, Malan De Villiers.
Application Number | 20120078374 13/310514 |
Document ID | / |
Family ID | 32825832 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120078374 |
Kind Code |
A1 |
Villiers; Malan De ; et
al. |
March 29, 2012 |
SPINAL MIDLINE INDICATOR
Abstract
A spinal midline indicator (10) has a body (14) of radiolucent
material for insertion between adjacent vertebrae (18, 20) and a
radiographic marker (12) located centrally with the body to
indicate the position of the spinal midline (22) in
anterior-posterior images when the body is centrally located
between the vertebrae. The radiographic marker is typically an
elongate metal handle. The body may carry secondary radiographic
markers (16) on opposite sides of and equidistant from the handle
so that the handle indicates the position of the spinal midline
when the body is placed centrally between the vertebrae.
Inventors: |
Villiers; Malan De;
(Wapadrand, ZA) ; Hahnle; Ulrich Reinhard;
(Saxonwold, ZA) |
Assignee: |
SpinalMotion, Inc.
Mountain View
CA
|
Family ID: |
32825832 |
Appl. No.: |
13/310514 |
Filed: |
December 2, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12616697 |
Nov 11, 2009 |
8090428 |
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13310514 |
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11187733 |
Jul 21, 2005 |
7637913 |
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12616697 |
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PCT/IB2004/000170 |
Jan 26, 2004 |
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11187733 |
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Current U.S.
Class: |
623/17.16 |
Current CPC
Class: |
A61B 17/025 20130101;
A61F 2/44 20130101; A61F 2002/4658 20130101; A61B 90/39 20160201;
A61B 2017/0256 20130101; A61F 2/442 20130101; A61B 17/1757
20130101; A61B 17/1671 20130101; A61F 2/4657 20130101; A61F
2250/0098 20130101; A61F 2002/3008 20130101; A61B 2090/3916
20160201 |
Class at
Publication: |
623/17.16 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2003 |
ZA |
2003/0874 |
Claims
1. A spinal midline indicator comprising: a body of radiolucent
material sized and shaped to fit into an intervertebral space
between two adjacent vertebrae; and a radiographic marker formed as
an elongated handle attached to and extending from the body along a
central axis of the body in an anterior-posterior direction,
wherein the handle is embedded in the body.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/616,697 (Attorney Docket No.
29850-705.302), filed Nov. 11, 2009, which is a continuation of
U.S. patent application Ser. No. 11/187,733 (Attorney Docket No.
29850-705.301), filed Jul. 21, 2005, which is a continuation of
International Application PCT/IB2004/000170 (Attorney Docket No.
29850-705.601), filed Jan. 26, 2004, which claims the benefit of
South African Application No. 2003/0874 (Attorney Docket No.
29850-705.841), filed Jan. 31, 2003, the full disclosures of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a spinal midline indicator.
[0003] It is important for a surgeon performing an ALIF (anterior
lumbar interbody fusion) or ACIF (anterior cervical interbody
fusion) cage or spinal disc replacement procedure to be able
accurately to establish the centre- or midline of the spine. It is
only once the surgeon has correctly established the position of the
spinal midline that he is able to place the cage or spinal disc
accurately on that midline. ff-centre placement will result in
eccentric loading and possible early failure or accelerated
wear.
[0004] At present, surgeons attempt to establish the spinal midline
by visual inspection of an A-P (anterior-posterior) image. However
this is often inaccurate, and can lead to subsequent off-centre
placement of the cage or disc with potential disadvantages as
described above.
[0005] The present invention seeks to provide an instrument which
will facilitate accurate establishment of the spinal midline.
BRIEF SUMMARY OF THE INVENTION
[0006] According to the present invention there is provided a
spinal midline indicator comprising a body of radiolucent material
for insertion between adjacent vertebrae and a radiographic marker
associated centrally with the body to indicate, in an
anterior-posterior radiographic image, the position of the spinal
midline when the body is appropriately located between the
vertebrae. Conveniently the radiographic marker is an elongate
handle which is connected to the body to facilitate placement of
the body between the vertebrae and which is made of a radiographic
material, i.e., a material which is substantially opaque to
radiographic (fluoroscopic) imaging.
[0007] In the preferred embodiment, the body carries, in addition
to the handle which serves as a first radiographic marker, two or
more secondary radiographic markers on opposite sides of and
equidistant from the first marker, whereby the first marker
indicates the position of the spinal midline when the body is
placed centrally between the vertebrae and the secondary markers
are seen in the radiographic image to be equidistant from lateral
edges of the vertebrae.
[0008] Further according to the invention there is provided a
method of identifying a spinal midline which comprises the steps of
inserting the body of a spinal midline indicator as summarized
above between adjacent spinal vertebrae, manipulating the body so
that the radiographic marker is seen in a radiographic image to be
on the spinal midline, and, using the position of the radiographic
marker as a guide, applying a marking, eg. a pin, to a vertebra to
indicate the midline.
[0009] Other features of the invention are set forth in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will now be described in more detail, by way
of example only, with reference to the accompanying drawings.
[0011] FIG. 1 shows a perspective view of a spinal midline
indicator according to the invention;
[0012] FIG. 2 shows a side view of the indicator in the direction
of the arrow 2 in FIG. 1;
[0013] FIG. 3 shows a side view of the indicator in the direction
of the arrow 3 in FIG. 1;
[0014] FIG. 4 shows an end view of the indicator in the direction
of the arrow 4 in FIG. 1;
[0015] FIG. 5 diagrammatically illustrates the indicator in use;
and
[0016] FIG. 6 shows a diagrammatic cross-section at the line 6-6 in
FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The spinal midline indicator 10 seen in FIGS. 1 to 4
includes an elongate handle 12 and a body 14 carried centrally at
one end of the handle. The handle is made of a radiographic
material, i.e. one which is opaque to radiation in the radiowave
part of the spectrum, including X-radiation. The handle may, for
instance, be made of stainless steel or titanium. The handle 12
extends substantially through the body 14. The body 14 is made of a
radiolucent material, i.e. one which is at least to some degree
transparent to the radiation. The body may, for instance, be made
of PEEK (polyetheretherketone) or UHMWPE (ultra-high molecular
weight polyethylene).
[0018] Embedded in the body 14 are two elongate markers 16, also of
radiographic material such as stainless steel or titanium. The
markers 16 are aligned parallel to the handle 12 and are located on
opposite sides of, and equidistant from the handle.
[0019] FIG. 5 diagrammatically illustrates, in an anterior view,
adjacent upper and lower vertebrae 18 and 20 respectively. As
explained above it is important, during an ALIF or ACIF cage or
spinal disc replacement procedure carried out anteriorly, for the
surgeon to be able accurately to establish the spinal midline,
indicated by the line 22, since it is centrally on this line that
the replacement disc or cage must be placed. The procedure is
typically carried out, with the patient lying prone and flat on his
back, through a frontal incision.
[0020] In order to establish the midline 22, the surgeon aligns the
handle 12 at a vertical orientation and uses it to insert the body
14 between the vertebrae 18 and 20. It will be understood that a
separate instrument 100 is used to hold the vertebrae apart for
this insertion to take place. An attempt is made to orientate the
body centrally with the handle 12 vertical, thereby to ensure that
the handle correctly indicates the midline 22.
[0021] An X-ray photograph or radiographic image is taken in the
vertical anterior-posterior direction. In this radiographic image
the handle 12, markers 16 and vertebrae 18,20 will be visible. By
ensuring that the markers 16 are equidistantly laterally spaced
from the osseous edges 23 of the vertebrae, i.e. that the distance
25 is the same on both sides, the surgeon can ensure that the body
14 and handle 12 are centrally positioned. It will be understood
that during this procedure, the handle 12 itself operates as a
radiographic marker indicating a central position.
[0022] It will also be understood that if the handle 12 and markers
16 are aligned with the anterior-posterior direction in which the
radiographic image is taken, they will appear in the radiographic
image merely as dots of small lateral dimension. However if the
handle is not perfectly aligned in the anterior-posterior, i.e.
vertical direction, parallax effects will result in the handle and
markers being seen as lines rather than dots.
[0023] This is illustrated in FIG. 6 in which the full lines show
the handle 10 at the correct anterior-posterior or vertical
orientation and the broken lines show it at orientations in which
it is misaligned by an angle 9. It will be understood that in a
radiographic image in the anterior-posterior direction indicated by
the arrow 24, the handle 12 and markers 16 will appear as dots at
the full line orientation but as short lines at the broken line
orientations.
[0024] By consulting radiographic images and manipulating the
indicator 10 as necessary in response to the information derived
therefrom, the surgeon can ensure that the indicator is at the
correct position and orientation. When the indicator is in the
correct position and at the correct orientation, the handle 12 will
lie in a vertical plane containing the midline 22. The surgeon can
now use the handle as a positive indicator of that midline. The
position of the radiographic marker can be used as a guide to apply
a marking to a vertebra to indicate the midline. He can accurately
mark the midline, for instance by knocking a pin 26 into one of the
vertebrae.
[0025] Once the midline has been marked on one or both of the
vertebrae, the indicator 10 is no longer required and can be
removed for later re-use. The marker(s) then serve to indicate the
midline 22 to enable subsequent, accurate positioning of the
relevant prosthesis to take place.
* * * * *