U.S. patent application number 14/642792 was filed with the patent office on 2015-07-16 for robot guided oblique spinal stabilization.
The applicant listed for this patent is MAZOR ROBOTICS LTD.. Invention is credited to Yossef BAR, Isidore LIEBERMAN, Moshe SHOHAM, Eli ZEHAVI.
Application Number | 20150196326 14/642792 |
Document ID | / |
Family ID | 42233683 |
Filed Date | 2015-07-16 |
United States Patent
Application |
20150196326 |
Kind Code |
A1 |
BAR; Yossef ; et
al. |
July 16, 2015 |
Robot Guided Oblique Spinal Stabilization
Abstract
A robotic system for performing minimally invasive spinal
stabilization, using two screws inserted in oblique trajectories
from an inferior vertebra pedicle into the adjacent superior
vertebra body. The procedure is less traumatic than such procedures
performed using open back surgery, by virtue of the robot used to
guide the surgeon along a safe trajectory, avoiding damage to
nerves surrounding the vertebrae. The robot arm is advantageous
since no access is provided in a minimally invasive procedure for
direct viewing of the operation site, and the accuracy required for
oblique entry can readily be achieved only using robotic control.
This robotic system also obviates the need for a large number of
fluoroscope images to check drill insertion position relative to
the surrounding nerves. Disc cleaning tools with flexible wire
heads are also described. The drilling trajectory is determined by
comparing fluoroscope images to preoperative images showing the
planned path.
Inventors: |
BAR; Yossef; (Tirat
HaCarmel, IL) ; ZEHAVI; Eli; (Haifa, IL) ;
LIEBERMAN; Isidore; (Ft. Lauderdale, FL) ; SHOHAM;
Moshe; (Hoshaya, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAZOR ROBOTICS LTD. |
CAESAREA |
|
IL |
|
|
Family ID: |
42233683 |
Appl. No.: |
14/642792 |
Filed: |
March 10, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13132095 |
Sep 19, 2011 |
8992580 |
|
|
PCT/IL2009/001130 |
Dec 1, 2008 |
|
|
|
14642792 |
|
|
|
|
61193441 |
Dec 1, 2008 |
|
|
|
Current U.S.
Class: |
606/279 ;
606/180 |
Current CPC
Class: |
A61B 2017/3407 20130101;
A61B 17/3205 20130101; A61B 17/1757 20130101; A61B 90/50 20160201;
A61B 17/7064 20130101; A61B 34/30 20160201; A61B 2034/107 20160201;
A61B 2034/303 20160201; A61B 2017/0256 20130101; A61B 2017/00685
20130101; A61B 2017/00261 20130101; A61B 2090/3762 20160201; A61B
17/320016 20130101; A61B 2017/564 20130101; A61B 17/7001 20130101;
A61B 2017/00557 20130101; A61B 2217/005 20130101; A61B 90/11
20160201; A61B 17/1671 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/3205 20060101 A61B017/3205 |
Claims
1-25. (canceled)
26. A method for performing spinal stabilization between two
adjacent vertebrae of a subject, the method comprising: drilling
two oblique posterior entry passages, one from each pedicle region
in an inferior one of said two adjacent vertebrae into the body of
the adjacent superior vertebra towards its anterior cortical rim;
cleaning the disc space between said two adjacent vertebrae;
inserting an inflatable distraction balloon through a first one of
said oblique posterior entry passages into said disc space between
said two adjacent vertebrae, and inflating said distraction
balloon; inserting a screw obliquely into said inferior and
superior vertebrae along the other one of said oblique posterior
entry passages, such that said vertebrae are mutually fixed in
position; deflating and withdrawing said distraction balloon; and
inserting a second screw obliquely between said inferior and
superior vertebrae along the first one of said oblique posterior
entry passages, such that said vertebrae are firmly fixed in
position.
27. A method for performing spinal stabilization between two
adjacent vertebrae of a subject according to claim 26, further
comprising the step of inserting bone grafting material into said
disc space through said first oblique posterior entry passage after
deflation and withdrawal of said distraction balloon.
28. A method for performing spinal stabilization between two
adjacent vertebrae of a subject according to claim 26, wherein said
oblique posterior entry passages are drilled with the aid of a
robot.
29. A method for performing spinal stabilization between two
adjacent vertebrae of a subject according to claim 26, wherein said
oblique posterior entry passages are drilled using a mechanical
positioner aligned by a surgeon.
30. A tool for cleaning an intervertebral space, comprising: a
hollow tubular sleeve; a central element disposed coaxially within
said hollow tubular sleeve; said central element being rotatable
relative to said hollow tubular sleeve; and at least one flexible
cutting element attached to a distal end of said central element,
such that rotation of said central element causes said flexible
cutting element to morcelize nucleus material in said
intervertebral space.
31. A tool according to claim 30, wherein said central element
comprises a screw element, such that said morcelized nucleus
material can be removed from said intervertebral space by rotation
of said central element.
32. A tool according to claim 30, wherein said flexible cutting
element comprises at least one wire element.
33. A tool according to claim 32, wherein said wire element
comprises at least one loop of wire.
34. A tool according to claim 30, wherein said flexible cutting
element is constructed of a shape memory alloy.
35. A tool according to claim 30, wherein the flexibility of said
cutting element is such that said cutting element changes its angle
of attack relative to the axis of said tool as said tool is
rotated.
36. A tool according to claim 30, wherein said at least one
flexible cutting element is operative to clean the end plates of
the vertebrae associated with said intervertebral space.
37. A tool for cleaning an intervertebral space, comprising: a
hollow tubular sleeve; a central element disposed coaxially within
said hollow tubular sleeve; said central element being
longitudinally moveable relative to said hollow tubular sleeve; and
at least one flexible cutting element attached to a distal end of
said central element, such that longitudinal motion of said central
element of said central element causes said flexible cutting
element to operate at different distances from the distal end of
said tool, wherein said hollow tubular sleeve and said central
element are rotatable, such that that rotation of said central
element causes said flexible cutting element to morcelize nucleus
material in said intervertebral space.
38. A tool according to claim 37, wherein said at least one
flexible cutting element is at least one loop of wire, one of whose
ends is attached to said hollow tubular sleeve, and the other of
whose ends is attached to said central element, such that
longitudinal motion of said central element causes said at least
one loop to expand or to contract.
39. A tool according to claim 37, further comprising a screw
element, such that said morcelized nucleus material can be removed
from said intervertebral space by rotation of said central
element.
40. A tool according to claim 37, wherein said flexible cutting
element is constructed of a shape memory alloy.
41. A tool according to claim 37, wherein the flexibility of said
cutting element is such that said cutting element changes its angle
of attack relative to the axis of said tool as said tool is
rotated.
42. A tool according claim 37, wherein said at least one flexible
cutting element is operative to clean the end plates of the
vertebrae associated with said intervertebral space.
Description
RELATED APPLICATIONS
[0001] This application is a division of U.S. Ser. No. 13/132,095,
which is a national stage application of PCT/IL2009/001130, filed
Dec. 1, 2009 and claiming the benefit of U.S. Ser. No. 61/193,441,
filed Dec. 1, 2008. The contents of these applications are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of vertebral
stabilization techniques by means of a pair of obliquely inserted
screws, especially using robotic procedures to safely generate the
oblique entry paths between the inferior and superior vertebrae to
be fused.
BACKGROUND OF THE INVENTION
[0003] As illustrated schematically in FIGS. 1A and 1B, a common
treatment for spinal stabilization is the fixation of two or more
vertebrae 10, 12, performed by insertion of a pair of screws 14,
16, into each of the vertebrae to be fused and connecting the screw
heads on either side of the spine by two rigid rods 17, 18.
Cleaning the disc space 15 and inserting bone graft into the
cleaned disc space causes bone to grow between the vertebrae until,
until several months later, the fusion is completed. FIG. 1A is a
cross sectional plan view of the superior vertebra 10, while FIG.
1B is a lateral view from the left of both fused vertebrae 10,
12.
[0004] The screws are usually inserted into the pedicles 19, two
for each vertebra such that a minimum of four screws are required
for each level of fusion. Spinal fusion by means of pedicle screw
insertion is currently the most common procedure adopted for spinal
stabilization, with hundreds of thousands of cases performed each
year all over the world.
[0005] A different fixation technique, using only two obliquely
inserted screws, one on either side of the spine, has also been
described in the article entitled "Direct Pediculo-Body Fixation in
Cases of Spondylolisthesis with Advanced Intervertebral Disc
Degeneration", by D. Grob et al published in European Spine
Journal, Vol. 5, pp. 281-285; 1996. The surgical approach suggested
in this article is for oblique trans-pedicular interbody fixation,
and it was successfully performed at the L4-L5 and L5-S1 levels. In
this technique, a pair of screws is inserted bilaterally through
the pedicles of the inferior vertebra and passed diagonally across
the disc space towards the anterior cortical rim of the superior
vertebral body. FIG. 2A illustrates a lateral view of such a pair
of vertebrae 20, 21, of a patient suffering from spondylolisthesis,
showing the oblique entry of the screw 22, as described in Grob et
al. Because of the anterior displacement of the upper slipped
vertebra 20, the entry angle of the screw is closer to the lateral
plane than 45.degree., the significance of which will be described
hereinbelow. Grob et al also describes the use of an inward angle
of 5.degree. to 10.degree. in the saggital direction, as will be
shown in FIGS. 2B and 2C below, to ensure that the screws remain
within the body of the superior vertebra 20 and do not penetrate
the cortical bone thereof.
[0006] Grob et al describes the cases of 16 patients with average
follow-up of 31 months (24-77 months) treated with this direct
pediculo-body fixation technique. Clinical evaluation showed
significant reduction in pain and increase in functionality.
Radiologic evaluations indicate solid bony fusion in all cases, and
no neurological or other complications were observed. The
stand-alone two-screw construction was concluded to be simple to
implement and clinically successful. The screws provided
three-dimensional stability, which led to bony unions and favorable
clinical outcomes in all patients. This procedure thus uses only
two screws, rather than four screws and two rods.
[0007] Even though this procedure was performed with good success
on a significant number of patients (16), the technique has not
gained much acceptance in the operating room. One reason for its
low acceptance may be that the required screw trajectories pass
close to nerve roots, and hence a clear view of the operation site
is needed to minimize the risk of damage to a nerve, whether at the
spinal canal or at the foramen. This required, as described in
Grob, an open surgical procedure with a large incision to expose
the entire region of the oblique trajectory from the skin to the
entry point at the vertebra, and towards the second vertebrae into
which the screw is inserted, so that the surgeon is able to
estimate accurately the correct entry position and angle. This
technique was therefore highly traumatic to the tissues and muscles
of the back, and this may have contributed to the lack of
acceptance of the technique, despite its structural simplicity.
[0008] In this respect the procedure is different from the common
spinal fusion methods using four screws per level. As illustrated
in FIGS. 1A and 1B, such prior art spinal fusion methods involve a
screw trajectory which remains exclusively within the vertebral
bone, from the entry point at the pedicle through to the vertebral
body. Unless a gross error has been made in the insertion
trajectory, there is little danger of nerve damage. It is reported
that only about 3% of such operations result in permanent
neurological deficits with this technique. The insertion trajectory
can either be determined visually by the surgeon, or can be
performed robotically, based on an operative plan using
pre-surgical CT images, or by use of a navigation system to define
an accurate path.
[0009] In addition, because of the difficulty of safe insertion of
the screws, as described in Grob, it is necessary to perform the
oblique drilling under fluoroscopic control, which may involve both
the patient and the operating room staff with unnecessarily
significant levels of X-ray exposure.
[0010] The procedure described in Grob was performed on patients
suffering from spondylolisthesis, involving significant anterior
slippage of the superior vertebra and an advanced stage of disc
resorption with a reduction of disc height by at least 75% of the
original height. Under these conditions, and as shown in FIG. 2A,
the drill enters the superior vertebra through the posterior end
plate, and at an angle of less than 45.degree. to the lateral
plane, thus clearly avoiding the foramen 27. However, if the
procedure were to be performed on a patient having normal vertebral
alignment and a normal disc height, the entry angle would need to
be tilted closer to the axial direction, thereby involving a closer
encroachment to the nerve roots at the foramen. This would increase
the risk of nerve damage in performing this oblique entry
procedure. Furthermore, the size of the incision that has to be
made in the subject's back is considerably longer for a normally
aligned vertebral spine, than for a patient with spondylolisthesis,
since the angle of entry of the drilling axis is closer in the case
of the normally aligned spine to the axial direction of the spine.
This makes the open surgery approach even less inviting as a
technique for treating aligned vertebrae. Finally, it should be
noted that in a significant number of patients, the vertebrae may
lie several centimeters below the surface of the patient's skin,
beneath layers of fat and muscle tissue, such that the additional
depth from the skin to the vertebra, in combination with the angle
of the trajectory to the normal, would increase the length of the
incision needed even more than indicated above.
[0011] This oblique entry procedure has been described again
recently, in US patent publication number US 2009/0163957 to S. St.
Clair et al, for use in fusion procedures in subjects having normal
vertebral separation. FIGS. 2B and 2C illustrate the position and
path of entry of such a pair of obliquely inserted screws. Though
the vertebral alignment in FIGS. 2B and 2C is different from that
in FIG. 2A, similar items are similarly numbered to those of FIG.
2A. FIG. 2B shows schematically a posterior view of the adjacent
vertebrae 20, 21, with interbody oblique fixation screws 22,
showing the inward tilt of the screws as described in Grob et al.,
and FIG. 2C shows a lateral view of the same vertebrae. The
drawings, and FIG. 2C in particular, show the path of the screws
from the inferior articular process 23 of the facet joint of the
inferior vertebra 21, traversing the pedicle and through the
endplate 24 of the inferior vertebra, across the interbody space 28
between the vertebrae, through the inferior endplate 25 of the
superior vertebra body 20, through the centrum of the superior
vertebra and towards the junction 26 of the superior endplate and
the anterior vertebral surface of the superior vertebra. It is
observed in FIG. 2C that the entry angle in the posterior-anterior
plane is at an angle of 45.degree. or less to the longitudinal axis
of the spine defined by the superior and inferior vertebrae, such
that the drill trajectory passes significantly closer to the
position of nerve roots at the foramen 27 than was the case with
the procedures described by Grob, performed on spondylolisthesic
patients. The procedures described in the US 2009/0163957
publication therefore further emphasizes the need for an apparatus
and method for performing oblique stabilization or fusion more
safely than the Grob prior art procedures, where only
spondylolisthesic patients were treated.
[0012] The disclosures of each of the publications mentioned in
this section and in other sections of the specification, are hereby
incorporated by reference, each in its entirety.
SUMMARY OF THE INVENTION
[0013] The present disclosure describes new exemplary systems and
methods for performing minimally invasive spinal stabilization,
using only two screws inserted in oblique trajectories from an
inferior vertebra pedicle into the adjacent superior vertebra body.
The procedure can be less traumatic than some previously described
procedures using oblique trajectories, by executing the trajectory
drilling in a minimally invasive manner through two stab incisions,
using a robotic arm to guide the surgeon along a safe trajectory.
The robot arm is virtually essential in such a minimally invasive
procedure since no access is provided for direct viewing of the
operation site, and the high accuracy required for oblique entry
can only be generally achieved using robotic control. This high
accuracy level is mandated by the presence of nerve roots exiting
the foramen in close proximity to the path required to proceed from
the pedicle region of the inferior vertebra to the adjacent
superior vertebra body. This robot guided system also obviates the
need for a large number of fluoroscope images to check the drill
insertion position relative to the nerve positions around the
subject's vertebrae.
[0014] One exemplary implementation involves a system for preparing
a spinal stabilization procedure between two adjacent vertebrae of
a subject, the system comprising:
(i) a surgical robot mounted such that it can define at least one
path for oblique screw insertion from the pedicle region in an
inferior one of the two adjacent vertebrae into the body of the
adjacent superior vertebra, towards its anterior cortical rim, (ii)
a control system receiving three-dimensional preoperative data,
including information regarding the spatial location of the bone
structures and the nerve positions of the two adjacent vertebrae,
and (iii) a registration system to relate the coordinate system of
the surgical robot with the three-dimensional preoperative data,
wherein the control system is adapted to use the information to
determine a safe path for the oblique screw insertion.
[0015] In such a system, the safe path may be a path in the
coordinate system of the surgical robot, which does not intersect
the course of a nerve of the subject, as determined from the
three-dimensional preoperative data. This three-dimensional
preoperative data may be obtained from CT scans, MRI scans or
ultrasound images.
[0016] Additionally, the safe path may be chosen using criteria
obtained from the three-dimensional preoperative data to ensure
that the path does not approach any nerve roots. The above
mentioned the control system should be adapted to inhibit the robot
from executing a path in the coordinate system of the surgical
robot, which would coincide with the course of a nerve of the
subject, as determined in the three-dimensional preoperative data.
Furthermore, this safe path may be determined by the control system
using criteria which ensure that the path does not approach any
nerve roots, nor that it can make any undesired collisions with a
bone structure. Yet other implementations may involve a system such
as described above, in which the safe path passes through a pedicle
of the inferior vertebra, and is determined by the control system
using criteria which further ensure that the safe path does not
break out of the cortical wall of the pedicle.
[0017] The safe path in the coordinate system of the surgical robot
may be viewed by fluoroscopic imaging or ultrasonic imaging. It
should be such that the spinal stabilization procedure can be
performed by minimally invasive techniques, or without direct
viewing of the anatomical land marks of the inferior vertebra.
[0018] With regard to the path, it can be defined by the robot by
means of a tool guide held in the robot's operating arm, such that
a surgeon can drill the safe path through the tool guide.
Alternatively, the system can further comprise a robotic held
drill, such that the robot itself can drill the safe path.
[0019] Additionally, in further implementations of any of the
above-described systems, the registration system may comprise an
image processing module for comparison of anatomical topological
features of the subject in the three-dimensional preoperative data
with those same features in fluoroscope images of the vertebrae.
Additionally, the registration system may further include a target
having predefined marker features, disposed in a predetermined
position and orientation relative to the robot, such that images of
the target in the fluoroscope images enable the co-ordinate system
of the robot to be related to that of fluoroscope images of the
vertebrae. Finally, as an alternative, the registration system
could utilize a navigational system to relate the co-ordinate
system of the robot to fluoroscope images of the vertebrae.
[0020] Still other example implementations involve a method for
performing spinal stabilization between two adjacent vertebrae of a
subject, the method comprising:
(i) generating three-dimensional preoperative data including
information regarding the spatial location of the bone structures
and nerve positions associated with the two adjacent vertebrae,
(ii) using the three-dimensional preoperative data to plan at least
one path for oblique screw insertion, from the pedicle region in an
inferior one of the two adjacent vertebrae into the body of the
adjacent superior vertebra towards its anterior cortical rim, the
at least one planned path avoiding nerve positions of the subject
as determined in the preoperative data, (iii) mounting a surgical
robot such that it can define the at least one planned path, (iv)
registering the coordinate system of the robot to the
three-dimensional preoperative data, (v) utilizing the surgical
robot to generate a drilled hole along one of the at least one
planned paths, and (vi) inserting a screw obliquely between the
inferior and superior vertebrae through the drilled hole.
[0021] In such a method, the at least one planned path may be two
planned paths, one on each lateral side of the vertebrae, such that
two screws may be inserted obliquely between the inferior and
superior vertebrae. The method may be performed minimally
invasively using a percutaneous technique. In any such methods, the
at least one path should also be planned to avoid any undesired
collisions with a bone structure.
[0022] Furthermore, according to another exemplary implementation,
the robot may define the at least one planned path by means of a
tool guide held in its operating arm, and the generating of the
drilled hole may then be performed by a surgeon using the tool
guide.
[0023] In any of these methods, the step of registering the
coordinate system of the robot to the three-dimensional
preoperative data may advantageously comprise the step of comparing
anatomical topological features of the subject in the
three-dimensional preoperative data with those same features in
fluoroscope images of the vertebrae. Such a registration method may
further comprise the step of disposing a target having known
markers, in a predetermined position and orientation relative to
the robot, such that images thereof in the fluoroscope images
enable the co-ordinate system of the robot to be related to that of
fluoroscope images of the vertebrae. Alternatively, the step of
relating the co-ordinate system of the robot to fluoroscope images
of the vertebrae may be achieved by means of a navigational
system.
[0024] Another exemplary implementation involves a method of
inserting a tool into a disc space between two adjacent vertebrae
of a subject, comprising the steps of:
(i) generating three-dimensional preoperative data including
information regarding the spatial location of bone structures and
nerve positions associated with the two adjacent vertebrae, (ii)
using the three-dimensional preoperative data to plan an oblique
posterior entry path, from a pedicle region in an inferior one of
the two adjacent vertebrae into the body of the adjacent superior
vertebra towards its anterior cortical rim, (iii) mounting a
surgical robot having a control system such that it can define the
planned entry path, (iv) registering the coordinate system of the
robot to the three-dimensional preoperative data, (v) using the
controller to ensure that the planned entry path in the coordinate
system of the surgical robot, does not approach a nerve position of
the subject, as determined in the preoperative data, (vi) using the
surgical robot to generate a drilled hole along the planned entry
path, and (vii) inserting the tool obliquely into the disc space
between the inferior and superior vertebrae through the drilled
hole.
[0025] Yet a further implementation may be for a method of
performing spinal stabilization between two adjacent vertebrae of a
subject, the method comprising:
(i) drilling two oblique posterior entry passages, one from each
pedicle region in an inferior one of the two adjacent vertebrae
into the body of the adjacent superior vertebra towards its
anterior cortical rim, (ii) cleaning the disc space between the two
adjacent vertebrae, (iii) inserting an inflatable distraction
balloon through a first one of the oblique posterior entry passages
into the disc space between the two adjacent vertebrae, and
inflating the distraction balloon, (iv) inserting a screw obliquely
into the inferior and superior vertebrae along the other one of the
oblique posterior entry passages, such that the vertebrae are
mutually fixed in position, (v) deflating and withdrawing the
distraction balloon, and (vi) inserting a second screw obliquely
between the inferior and superior vertebrae along the first one of
the oblique posterior entry passages, such that the vertebrae are
firmly fixed in position.
[0026] This latter method for performing spinal stabilization may
further comprise the step of inserting bone grafting material into
the disc space, through the first oblique posterior entry passage,
after deflation and withdrawal of the distraction balloon.
Additionally, in such methods, the oblique posterior entry passages
may advantageously be drilled with the aid of a robot.
Alternatively, they may be drilled using a mechanical positioner
aligned by a surgeon.
[0027] A further example implementation may involve a tool for
cleaning an intervertebral space, the tool comprising:
(i) a hollow tubular sleeve, (ii) a central element disposed
coaxially within the hollow tubular sleeve, the central element
being rotatable relative to the hollow tubular sleeve, and (iii) at
least one flexible cutting element attached to a distal end of the
central element, such that rotation of the central element causes
the flexible cutting element to morcelize nucleus material in the
intervertebral space.
[0028] In such a tool, the central element may comprise a screw
element, such that the morcelized nucleus material can be removed
from the intervertebral space by rotation of the central element.
In either of these tools, the flexible cutting element may comprise
at least one wire element, which could advantageously comprise at
least one loop of wire. In any of these tools, the flexible cutting
element may be constructed of a shape memory alloy.
[0029] Another exemplary tool described in this disclosure, for
cleaning an intervertebral space, may comprise:
(i) a hollow tubular sleeve, (ii) a central element disposed
coaxially within the hollow tubular sleeve, the central element
being longitudinally moveable relative to the hollow tubular
sleeve, and (iii) at least one flexible cutting element attached to
a distal end of the central element, such that longitudinal motion
of the central element of the central element causes the flexible
cutting element to operate at different distances from the distal
end of the tool, (iv) wherein the hollow tubular sleeve and the
central element are rotatable, such that that rotation of the
central element causes the flexible cutting element to morcelize
nucleus material in the intervertebral space.
[0030] In such a tool, the at least one flexible cutting element
may be at least one loop of wire, one of whose ends is attached to
the hollow tubular sleeve, and the other of whose ends is attached
to the central element, such that longitudinal motion of the
central element causes the at least one loop to expand or to
contract. The tool may further comprise a screw element, such that
the morcelized nucleus material can be removed from the
intervertebral space by rotation of the central element.
Furthermore, the flexible cutting element may be constructed of a
shape memory alloy.
[0031] An additional feature in any of the tools mentioned above is
that the flexibility of the cutting element may be such that the
cutting element changes its angle of attack relative to the axis of
the tool as the tool is rotated. The at least one flexible cutting
element of the tool may also be operative to clean the end plates
of the vertebrae associated with the intervertebral space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The presently claimed invention will be understood and
appreciated more fully from the following detailed description,
taken in conjunction with the drawings in which:
[0033] FIGS. 1A-1B show a prior art fusion of two vertebrae by
insertion of a pair of screws into each of the vertebrae, and
connection of the screw heads by two rigid rods;
[0034] FIGS. 2A, 2B and 2C illustrate schematically various views
of the fusion of two vertebrae by insertion of a pair of screws
between the two vertebrae;
[0035] FIGS. 3A and 3B are schematic illustrations of sections of
the spine showing how the nerve roots emerge laterally from the
spinal column through the foramina;
[0036] FIG. 4A is a schematic drawing of a robotic system of the
present disclosure, mounted on a patient's back, ready for
performing oblique screw trajectory drilling;
[0037] FIG. 4B is a typical three dimensional target, such as is
used for the robot co-ordinate registration process;
[0038] FIGS. 5 and 6 are schematic views of the spine, showing how
the disc cleaning and removal procedures through the oblique
trajectory holes, as described in this disclosure, relate to the
structure of the vertebrae;
[0039] FIG. 7 is an illustration of a nucleus morcelizing tool,
adapted to use a flexible wire cutter at its distal working
end;
[0040] FIGS. 8A, 8B and 8C illustrate various implementations of
the flexible wire cutting tools used for disc cleaning according to
further implementations shown in this disclosure;
[0041] FIG. 9 is a schematic illustration of a complete disc
evacuation system implementing a screw pump tool, as shown in FIGS.
8B and 8C above; and
[0042] FIG. 10 shows a vertebral distraction device composed of an
inflatable balloon inserted through one of the obliquely drilled
holes.
DETAILED DESCRIPTION
[0043] The current disclosure describes exemplary robotic devices
and a robotic procedure for performing minimally invasive spinal
stabilization, using only two screws inserted in an oblique
trajectory from an inferior vertebra pedicle into the adjacent
superior vertebra body. The procedure can be less traumatic than
the previously described procedures using oblique trajectories, by
executing the trajectory drilling in a minimally invasive manner
through two stab incisions, using a robotic arm such as the
SpineAssist supplied by Mazor Surgical Technologies Ltd. of
Caesarea, Israel, to guide the surgeon along a safe trajectory. The
robot arm is essential in such a minimally invasive procedure since
no access is provided for direct viewing of the anatomical land
marks, and the high accuracy required for oblique entry can only be
generally achieved using robotic control.
[0044] Reference is now made to FIGS. 3A and 3B which are
illustrations of sections of the spine showing how the nerve roots
emerge laterally from the spinal column through the foramina, from
a position just next to or superior the facet joint, and descend
downwards laterally of the pedicle. FIG. 3A is a cross sectional
view of a vertebra 30, showing the spinal cord 31 and its nerve
roots 32 exiting the spinal channel at the intervertebral foramen
33 and extending laterally outwards just anterior to the facet
joint 35. FIG. 3B is an isometric view of a single vertebra 30,
showing how the nerve root 32 bends downwards after leaving the
foramen 33 of the spinal bone structure. As a consequence of this
three-dimensional topography of the nerves, the path of a screw
trajectory 37, as shown in the dotted outline in the vertebra of
FIG. 3B, running from the pedicle of an inferior vertebra,
diagonally upwards across the disk space 38 towards the anterior
cortical rim of a superior vertebral body passes very close to and
just below the nerve 32 where it exits the foramen 33. Therefore
unless the screw trajectory is drilled with very high accuracy,
there is danger of damage to a nerve root or spinal cord.
Furthermore, in order to reach the superior vertebra, the angle
being drilled in the pedicle does not coincide with the axis of the
pedicle. There is therefore a danger that if an accurate trajectory
is not used, the drill may break out of the cortical wall of the
pedicle, causing collateral damage.
[0045] The possibility of nerve damage may be the main reason why
the prior work of Grob and colleagues was performed using a
surgical approach involving a standard posterior exposure of the
involved vertebrae, such that the surgeon could see the exact path
being drilled, and align it to avoid the nerve roots.
[0046] In the preoperative planning stage of the present method,
the surgeon plans the screw locations and entry trajectories
generally on a set of CT scans, where 3D views of the operating
site are available. Although CT scans are currently the most
generally used three-dimensional imaging techniques, it is to be
understood that other imaging techniques, such as MRI or Ultrasound
may equally well be used. CT scan data will be used in this
application as an illustrative and non-limiting three-dimensional
imaging method. The surgeon uses specific criteria which enable him
to choose the safest path with the least danger to nerve roots in
the vicinity of the operation site. The position of the nerve roots
can be marked on the CT scan data, such that these positions can be
avoided when the insertion trajectory is planned. Since a
conventional spinal CT scan does not show nerve tissue, when using
CT data, the surgeon can estimate nerve positions based on the
features of the spinal bone anatomy, and the surgeon's knowledge of
where the nerves are disposed relative to those features. Since the
nerves are directly visible in MRI imaging, if such an imaging
modality is used, the nerve positions can be used directly by the
surgeon in his preoperative plan.
[0047] The preoperative CT scans are then registered to the
intraoperative imaging system, commonly a fluoroscope imaging
system. One method of performing such image registration is by use
of an image processing system to compare certain of the subject's
anatomical topological features in the CT scans with those same
features in the fluoroscope images. Additionally, the co-ordinate
system of the robot must be registered to the fluoroscope
co-ordinate system so that the robot pose can be related to the
fluoroscope images. This can typically be done by use of a three
dimensional marker target, whose position and alignment is known
relative to that of the robot, such as by mounting it on the same
baseplate as is used by the robot, and whose image is then defined
in the fluoroscope system, thus registering the robot's absolute
frame of reference with the image co-ordinate system of the
fluoroscope. As an alternative to the use of a target, a
navigational system can be used, detecting the robot position and
the position of a vertebra by means of markers, such as LED's or
retroreflectors attached to each, whose positions are correlated
using the navigation system. Alternatively, the positions of known
anatomical landmarks and known points on the robot can be related
by use of a monitored touch tool. Once this registration procedure
is complete, the robot can then be programmed to guide the surgical
tool along the safe trajectory as planned by the surgeon.
[0048] Reference is now made to FIG. 4A, which is a schematic
drawing of the robotic system mounted on a patient's back, ready
for performing the oblique screw trajectory drilling method
described in this disclosure. The robot 40 is mounted on a bridge
assembly 41 supported by clamping or by use of one or more K-wires
43 to vertebrae of the spine and/or the pelvis, and also optionally
clamped to the operating table 42. Use of this additional clamping
to the operating table increases the stability of the robot under
conditions when force may be applied to the robot during the
drilling process, which may cause it to move as the drilling
process exerts forces on the spine. In addition, a rigid reference
by clamp or K-wire 43 is made to the spine, so that the robot's
position is fixed relative to the bones being operated on by the
robot. The robot is not generally used to perform the drilling
itself, but rather to align a tool guide 44 in the calculated
position and direction, such that the surgeon can then perform the
procedure using that tool guide to ensure an accurate and safe
entry path. However, it is to be understood that the use of the
robot is not intended to be limited to aligning a tool guide, and
that the application is intended to also cover more active use of
the robot in performing the procedure, such as in drilling the hole
itself. The control system 45 is adapted to utilize input data from
CT scans stored preoperatively to implant the surgeon's selected
entry path onto that data. The CT scans should include data on the
vertebral anatomy and the control software should be capable of
using the position of the nerves determined from this vertebral
anatomy, as forbidden areas for the insertion trajectory to pass
through or to pass nearby. The system thus provides assistance to
the surgeon by showing him potential collision paths of his/her
planned insertion trajectory with nerves lying in its path.
According to an alternative implementation of the control system,
such a routine could ensure that even if the surgeon inadvertently
plans a hazardous insertion trajectory path, the control system
would not enable the surgeon to execute such a plan, by blocking
that robot pose. Additionally, in some oblique entry procedures,
especially those performed in the sacral region on patients
suffering from lordosis, the angle of insertion may be close to
axial alignment with the spine, such that the drill trajectory may
collide with the pelvic bone. Thus, collisions with bone structures
may also be taken into consideration in programming blocked poses
of the robot. When MRI is used as the imaging modality, nerves are
also seen, and their imaged position may be used directly for
planning the insertion trajectory. The registration between the
preoperative CT data and the true life world of the robot
co-ordinate system, as determined, for instance, on real time C-arm
fluoroscope images 46, can be performed by any of the known
registration methods, such as those mentioned above. One exemplary
implementation of a three dimensional target 47, such as can be
used for registering the robot co-ordinate system to that of the
fluoroscope system is shown in FIG. 4B. This target 47 is a three
dimensional body, transparent to X-rays, containing preferably two
layers of radio-opaque marker balls 48, whose positions are known,
such that analysis of the positions of the marker balls on an X-ray
image of the target can be used to determine the three dimensional
orientation of the target. The exemplary target shown has a set of
screws or pins 49, for attaching it to the same base as that used
by the robot, such that it has a known geometric relation to that
of the mounted robot, and once its position and orientation is
known from analysis of images, so is the position and orientation
of the robot known.
[0049] Although the system and method has been described
hereinabove for use in spinal fusion, it is also possible to use
the same oblique entry procedures and system for dynamic
stabilization of the spine without fusion. This can be achieved by
having a flexible rather than a rigid connection between the
vertebrae. The oblique fixing screws are then provided with a
somewhat flexible region along part of its length to enable limited
motion between the two vertebrae. Such an application has been
described in US Patent Publication No. US 2009/0112269 to I. H.
Lieberman et al., one of the inventors of the present application,
and assigned to The Cleveland Clinic Foundation.
[0050] In order to obtain good bone fusion, it is necessary to
clean the disc space to remove the disc nucleus and to insert bone
graft or any kind of bone substitute that will encourage inter-body
bone growth and bony fusion. By following these procedures bone can
grow well, and achieve a bony fusion. Furthermore, it is possible
to use the oblique entry screws to fix adjacent vertebrae in
combination with some posteroior fusion techniques, such as
postero-lateral/medial fusion across the facet joints or between
transverse processes, instead of inter-body fusion. In such a
procedure, no cleaning and bone graft of the intervertebral space
is needed. Also in the case of dynamic stabilization of the spine
without fusion, no disc cleaning and bone graft is needed.
[0051] In addition to the drilling and screw insertion, more steps
are required to complete the procedure. These steps include:
nucleus morcelizing, nucleus remnant removal/evacuation, vertebrae
end-plate scraping and in some cases vertebrae distraction.
[0052] There exist commercial tools for disc morcelizing and
removal of the nuclear material. In most cases, these prior art
tools are inserted from the subject's lateral side, radially to the
disc space. This involves the drilling of additional holes in the
annulus, even for minimally invasive methods, besides the hole or
holes required for the insertion of the fixation screws. Since the
annulus has important support characteristics for the disc, such
additional holes in the annulus may considerably affect the
strength of the intervertebral support. The oblique approach, on
the other hand, obviates the need for such additional holes, by
accessing the nucleus of the disc other than through the annulus
itself. Furthermore, since the oblique posterior entry methods
described in this disclosure provide access to the disc space,
which non-oblique entry methods can only access by lateral entry,
this method enables the disc morcelizing and removal tools to be
inserted without the need to make any additional holes at all,
besides the oblique ones drilled for the fixation screws
themselves.
[0053] Disc cleaning and removal through the oblique trajectory
requires understanding of the three dimensional structure in a more
detailed way. This is illustrated by reference to FIGS. 5 and
6.
[0054] Reference is first made to FIG. 5, which is a schematic
cross-sectional view of the disc region of a vertebra 50 showing
the two holes 52 through which the drilling path of the oblique
trajectory enters the disc nucleus space 53. The drilled hole
typically has a diameter of about 4 to 5 mm. A disc cleaning tool
of the type described hereinbelow, having a flexible wire head, is
inserted through one of the drilled working channels into the
nucleus space, and rotation of the tool enables the wire head to
detach and morcelize the nucleus tissue in the region 55
surrounding the hole exit. These tools differ from prior art tools
in that the cutting blades are constructed of flexible wires, so
that the angle of attack relative to the tool axis can vary as the
tool is rotated. Use of a flexible wire head enables the tool to
cover the space within the disc annulus, in spite of the axis of
rotation of the tool being at an angle to the axis of the disc
space. Once the area within the range of the cleaning head has been
morcelized, the tool is withdrawn and inserted through the other
hole, and the procedure repeated therein. Since the two treated
regions overlap, selection of suitable placement of the holes
enables the entire disc region to be cleaned of the tissue of the
disc by this means.
[0055] FIG. 6 is a lateral view of the treated vertebral region,
showing the cleaning tool 56 passing through one of the oblique
trajectory holes 57 in order to access the disc region 51 for
cleaning. As the tool is rotated, the end cutter wires 58 flex with
the rotation and thus are able to cut and morcelize the tissue over
a wider area of the disc than would be possible with a rigid headed
tool operated in the same location. Since the wire cutting head 58
can be extended or retracted from the tool sleeve 56, it can be
adjusted to cover essentially the whole of the internal volume of
the disc situated on its side of the disc.
[0056] FIG. 7 is an illustration of a commercially available
nucleus morcelizing tool 70, adapted to use a flexible wire cutter
72 at its distal working end.
[0057] Reference is now made to FIGS. 8A to 8C which illustrate
various typical implementations of the flexible wire cutting tools
used for disc cleaning according to a further implementation of the
present invention The disc cleaning tool, shown in FIG. 8A, is
composed of two modular parts:
1. The cutting head, which is made of a pair of loops of spring
material 82. 2. The handle 84, which comprises an outer tube or
sleeve with an inner coaxial element 86, which can be a rod or a
tube, the inner element being capable of longitudinal movement 85
relative to the outer tube.
[0058] One end of each of the two loops of spring material 82 is
attached to the inner element 86, while the other end of each of
the two loops of spring material is attached to the outer tube 84.
As the inner element is pushed distally, the length of the two
loops increases, such that they can access and clean points within
the vertebral disc space further from the end of the tool handle.
As the inner element is retracted, the loops can access the disk
space closer to the end of the tool handle.
[0059] Furthermore, retraction of the inner element enables the
surgeon to move nucleus material detached from points further from
the tube end towards the tube end, from where it can be disposed
of, down the tube. The inner element 86 is generally constructed in
the form of a tube such that the dislodged nuclear material can be
removed through the tube, as shown in FIG. 9 below.
[0060] Since the extent of the region in which the tool performs
its cutting action can be readily controlled using the position of
the inner element, this tool enables the user to operate it in a
safe and simple way without any need for additional observation
systems, such as a laparoscopic vision system.
[0061] FIG. 8B is a schematic rendering of another tool for use in
cleaning the inner volume of a vertebral disc. This tool has a pair
of loops of wire as its cutting head arranged in the form of a
propeller 87. In addition, an Archimedes screw 88 is shown in the
barrel of the tube 84, such that nucleus material detached from
within the disc can be transported out of the disc for disposal as
the tool head is rotated. FIG. 8C illustrates an alternative
cutting head, using a pair of flexible wires arranged like a double
tailed whip 89.
[0062] The cutting blades of all of the tools for use in the disc
cleaning operations using the current oblique entry technique can
advantageously be made of a shape memory material, such as Nitinol,
so that they can be inserted at the end of the tool through the
oblique bore in a folded position, and will deploy to their
operating configuration on exit from the bore into the disc space.
Furthermore, these tools differ from prior art tools in that the
cutting blades are constructed of flexible wires, so that the angle
of attack relative to the tool axis can vary as the tool is
rotated, to enable the cutting head to achieve a larger reach
within the disc annulus than would be possible with a rigid cutting
head. Additionally, such tools with flexible wire cutting heads,
are able to clean the end plates of both the superior and the
inferior vertebrae simultaneously and essentially equally well,
even though the access to the superior vertebra end plate is
substantially better than to the inferior vertebra end plate,
because the angle at which the cleaning tool faces the superior
vertebra end plate is more "face-on" than the inferior vertebra end
plate. With a radially inserted tool, this problem does not arise
since both end plates face the tool at equal alignments.
[0063] Devices exist for disc cleaning, generally entering the disc
space radially, though Trans1 Inc, have described an axial approach
in their AxiaLIF.RTM. procedure, though this is limited to the
sacral region, for L5-S1 treatment. The AxiaLIF.RTM. procedures and
the tools used are described in U.S. Pat. No. 6,558,390 and
subsequent patents and applications assigned to Trans1. The tools
used for morcelizing the disc nucleus material, unlike the tools of
the present disclosure, generally have a rigid cutting head, as
they operate in an almost axial position, and therefore do not have
or need the flexibility to change operating angle with rotation of
the tool. However, as previously stated, none of the previously
described methods is designed to enter the disc space in a truly
oblique manner.
[0064] References now made to FIG. 9, which is a schematic
illustration of a complete disc evacuation system implementing a
screw pump tool, as shown in FIGS. 8B and 8C above. The tool is
shown operating within a disc space 90 between an inferior 91 and
superior 92 vertebra. It is power operated, typically being rotated
at speeds of between one and a few revolutions per second and can
use the generic hospital suction system to pump out the morcelized
material removed from the disk space into a waste container 94.
This system can be operated through the oblique trajectory.
[0065] Reference is now made in FIG. 10 which shows a vertebra
distraction device composed of an inflatable balloon 102 inserted
through one of the drilled holes 103 from the pedicle region into
the vertebral disc space 104, and then inflated by means of an
inflation tube 106 to generate opposing forces on the two
neighboring vertebrae, thus enabling decompression and release
stenosis. Once distraction is achieved, one of the oblique screws
is inserted to affix the vertebrae at the distracted position. The
balloon is then deflated and taken out of the disc space, with the
disc positions maintained by the first inserted oblique screw. Bone
graft is then inserted through the second drilled hole from which
the deflated balloon was withdrawn, following which, the second
oblique screw is inserted to complete the fixation of the two
vertebrae.
[0066] FIG. 10 also illustrates well how the oblique hole passes
very closely to the intervertebral foramen 108, and the consequent
need for high accuracy when drilling such holes to avoid damage to
the nerves exiting the spinal column at the foramina. This
emphasizes the advantage in the use of robotic control and drilling
when generating such oblique holes.
[0067] The oblique approach described in this disclosure has an
additional advantage over prior art lateral or radial approaches,
where additional holes have to be made in the annulus of the disc
in order to clean it, to perform distraction, or to insert an
interbody support such as a cage. Since the annulus has important
support characteristics for the disc, this additional hole in the
annulus may considerably affect the strength of the intervertebral
support. The oblique approach, on the other hand, obviates the need
for such an additional hole, by accessing the nucleus of the disc
other than through the annulus itself.
[0068] It is appreciated by persons skilled in the art that the
present invention is not limited by what has been particularly
shown and described hereinabove. Rather the scope of the present
invention includes both combinations and subcombinations of various
features described hereinabove as well as variations and
modifications thereto which would occur to a person of skill in the
art upon reading the above description and which are not in the
prior art.
* * * * *