Note: Descriptions are shown in the official language in which they were submitted.
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COMPUTER ASSISTED SURGERY SYSTEM
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FIELD OF THE INVENTION
[0001] The present invention relates to a computer assisted surgery system and
a
method for operating a computer assisted surgery system, and in particular to
a
computer assisted surgery system and a method for operating a computer
assisted
surgery system providing a virtual representation of a medical device to
provide an
easier application of the medical device, such as an implant or the like.
BACKGROUND OF THE INVENTION
[0002] Fractures of the femoral neck, for example, may be treated by
intramedullary
nailing. In such treatments, a nail for intramedullary nailing typically
comprises at
least one bore hole for receiving a bone screw. The nail is generally
introduced in the
longitudinal direction of the femur, wherein the bone screw laterally extends
at a
certain angle with respect to the neck of the lemur when the bone screw is
received
within the at least one bore hole. A certain problem of the surgeon is to
predict the
future or implanted position of such a nail or implant or parts therof. In the
past. the
operator has acted in a trial and error manner to obtain a more or less
optimum
position of the implant. However, this may lead to a longer duration of the
operation
which may lead to higher stress for the patient. Further, for each trial, at
least one X-
ray image (e.g. a fluoroshot) is generally necessary in order to check the
present
position of the implant in order to evaluate its position.
100031 In recent times, computer assisted surgery for dynamic hip screw had
been
described by Amir Herman et al. in The International Journal of Medical
Robotics
and Computer Assisted Surgery, Dec. 29, 2008; Volume 5, pages 45-50, describes
a
computer assisted surgery system using an image analysis technology in order
to
measure three-dimensional distances, visualize implant templates, and view a
guided
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trajectory on standard fluoroscopy. A guiding system combines a set of X-ray
opaque
markers incorporated into transparent hardware as an aiming, positioning, and
referring device. This device is attached to a guide wire. Fluoroscopic images
are
obtained by the surgeon and then are processed by an image processing engine
which
calculates a three-dimensional orientation relative to a C-arm and a drill
trajectory in
the image.
100041 Further, a process for the acquisition of information intended for the
insertion
of a locking screw into an orifice of an endomedullary device is described in
EP 1 491 151 131. This document describes a process for the acquisition of
information intended for the insertion of a locking screw into a distal
locking hole of
an endomedullary device. The described process includes taking two images of
different orientations of the distal part of the endomedullary device using a
radioscopic unit, acquisition of projection parameters, especially the
position of the
X-ray source and the projection plane of each image by locating a reference
frame
fixed on the endomedullary device and optionally another reference frame fixed
on
the radioscopic unit. The process further includes correcting any distortion
of the
images, segmenting the distal part of the endomedullary device in each image
and
calculating the attributes relating to the position of the device and to that
of the holes,
wherein the attributes comprise at least the contours of the device, its
centre of
gravity and its principal axis. Further, the process includes constructing the
projection cone of the distal part of the device for each image. determining
the
intersection of the two projection cones, modelling of the endomedullary
device on
the basis of the intersection, determining a centre of a locking hole with the
aid of the
modelling and of the centres of gravity of the holes determined on the images,
determining the orientation of the locking orifice in an iterative manner, and
guiding
of a drill tool.
SUMMARY OF THE INVENTION
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[0005] The present invention provides a computer assisted surgery system and a
method for operating a computer assisted surgery system allowing a simple and
fast
positioning of a medical device to be applied, such as an implant, for
example.
[0006] According to one embodiment of the invention, there is provided a
method
for operating a computer assisted surgery system, the method comprising
positioning
of a reference body in relation to an anatomical structure, the reference body
virtually representing a position of a medical device to be applied to the
anatomical
structure, detecting a position of the reference body in relation to the
anatomical
structure, superimposing the anatomical structure with a virtual
representation of a
medical device to be applied based on the detected position of the reference
body in
relation to the anatomical structure, providing rules for allowable ranges for
applying
the medical device in relation to the anatomical structure, modifying the
position of
the reference body, and optimizing the virtual position of the medical device
to be
applied with respect to the anatomical structure so as to obtain a best fit
with respect
to the rules for allowable ranges.
[0007] Thus, by using a virtual representation of a medical device to be
applied, a
future position of a real medical device can be predicted without the need of
inserting
this medical device during the phase of determining the final desired position
of the
medical device. Thus, the position of the medical device can be virtually
optimized
before inserting the medical device. This may lead to reducing the stress for
the
patient with respect to an incision and X-ray impact. Optimizing may include
finding
of the optimal location, orientation and geometry of the medical device, i.e.
the
implant. This optimizing may take place supported by a computer device. The
reference body may be a particular add-on element as well as a medical tool
having a
unique geometry to identify the position thereof in imaging.
100081 According to another embodiment of the invention, the position of a
medical
device includes dimensions, location, and orientation of the medical device.
[0009] Thus, the medical device can be virtually represented considering all
relevant
information with respect to an anatomical structure of the patient. Position
may also
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be the geometry of the medical device, in particular out of a predetermined
variety of
medical devices.
100101 According to yet another embodiment of the invention, detecting the
positioned reference body in relation to an anatomical structure comprises
taking two
two-dimensional images from different angles and generating a three-
dimensional
representation based on the two two-dimensional images, and determining a
spatial
position of the reference body in relation to the anatomical structure based
on the
three-dimensional representation. The two 2-dimensional images may include the
anatomical structure receiving the medical device. The position of the medical
device
in relation to the anatomical structure may be based on the 3-dimensional
representation.
[0011] Thus, the anatomical structure as well as the virtual implant or the
virtual
medical device to be applied can be represented in a three-dimensional manner
in
order to give an overview over the correct positioning and dimensioning of the
medical device to be applied.
100121 According to still yet another embodiment of the invention, modifying
may
comprise rotating and/or displacing the reference body.
100131 Thus, the reference body representing the position of the medical
device can
be virtually positioned with respect to the anatomical structure so as to find
out the
optimized position of the future positioned medical device within the rules
provided,
wherein the rules provide the allowable ranges for applying the medical device
in
relation to the anatomical structure.
10014] According to still yet another embodiment of the invention, modifying
may
comprise selecting the medical device out of a predetermined group of a
variety of
medical devices.
10015] Thus, for meeting the rules for allowable ranges, also the dimensions
of the
medical devices can be selected out of a predetermined group in order to find
out an
optimal implant type to be implanted, for example. The various types may have
various geometries, e.g. lengths. inclination angles, and other geometric
properties.
corresponding to the various anatomical properties.
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10016] According to still yet another embodiment of the invention, the method
of
operating a computer assisted surgery system further comprises imaging the
superposition of the anatomical structure and the virtual representation of
the medical
device to be inserted.
100171 Thus, the surgeon is capable of in-situ controlling and monitoring of
the
ongoing process of the computer assisted surgery system, which may be of
relevance
when finally deciding whether the optimization is sufficient and to provide a
final
check by the surgeon in person.
10018] According to still yet another embodiment of the invention, the
position of
the medical device to be applied is remote from the reference body.
Preferably, the
medical device is an implant. Preferably, the reference body is mountable to a
medical tool, such as an aiming tool, for example.
[0019] Thus, the reference body does not have to be provided in the immediate
vicinity of the medical device. Implants may be virtually represented that are
not in
direct vicinity of the reference body. This is particularly relevant for
implants that
have a final remote position with respect to an opening location of the
incision.
Further, also sub-implants can be virtually represented, such as a bone screw
of an
intramedullary nail, for example, when providing the reference body to an
aiming
tool.
[0020] According to still yet another embodiment of the invention, there is
provided
a program element, which, when being executed by a processor is adapted to
carry
out the inventive method for operating a computer assisted surgery system.
100211 According to still yet another embodiment of the invention, there is
provided
a computer readable medium having stored the inventive program element.
[0022] Thus, the method for operating a computer assisted surgery system can
be
carried out on a computer and a computer program, respectively.
100231 According to still yet another embodiment of the invention, there is
provided
a computer assisted surgery system comprising a reference body in relation to
an
anatomical structure, the reference body virtually representing a position of
a
medical device to be applied to the anatomical structure, a detector device
being
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adapted for detecting a position of the reference body in relation to the
anatomical
structure, a database including virtual medical device information and a
computation
device being adapted for superimposing the anatomical structure with a virtual
representation of a medical device to be applied, based on an output of the
detector
device and modifying the position of the reference body and optimizing the
virtual
position of the medical device to be applied with respect to the anatomical
structure
so as to obtain the best fit with respect to predetermined rules for allowable
ranges
for applying the medical device in relation to the anatomical structure.
[0024] Such a computer assisted surgery system allows to predict the future
position
of a medical device to be applied, such as an implant, for example, without
the need
for a trial and error procedure of a surgeon in order to meet the
predetermined rules
for allowable ranges for applying the medical device in relation to the
anatomical
structure, which rules may be provided in form of required distances, for
example, to
the surface of the bone, particular inclination angles between for example the
longitudinal direction of the femur and the orientation of a femoral neck, and
the
like.
[0025] According to an embodiment of the invention, the data base includes a
plurality of data sets for the medical device, wherein the data sets represent
a variety
of medical devices.
[0026] Thus, not only the orientation and the location of the medical device
can be
determined in order to meet the predetermined rules for allowable ranges, but
also
the dimensions of the medical device as such. This may be of relevance in
particular
when having a wide variety of anatomies requiring different dimensions with
respect
to the length, the diameter and particular angles of for example an
intrarnedullary
nail and the respective bone screws. According to an embodiment of the
invention.
the medical device is an implant.
100271 According to still yet another embodiment of the invention, the system
further
comprises a medical tool being adapted for positioning the implant, wherein
the
reference body is mountable in a predefined manner to the medical tool.
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100281 Thus, the reference body may be used for representing an intramedullary
nail,
which is still not implanted in order to find the correct position of the
intramedullary
nail as well as the correct position of the future implanted bone screw before
having
inserted the intramedullary nail. However, the intramedullary nail may be
considered
as a reference body, as the intramedullary nail may have a unique form
representing
also the future position of a bone screw to be inserted. Thus, when having
inserted
the intramedullary nail being mounted to the medical tool, from the geometry
of the
intramedullary nail, the future position, i.e. the location, the dimension,
and the
orientation of the bone screw can be determined. It should be noted that the
intramedullary nail can be used as a reference body representing the future
position
of a bone screw, for example. However, also a separate reference body can be
used
for representing for example the intramedullary nail, wherein such reference
body
may be fixed in a predetermined position to the medical tool or the nail in
order to
represent and predict the future position of the intramedullary nail. When
knowing
the geometry and orientation of the intramedullary nail, also the future
position of a
bone screw can be predicted by evaluating the reference body mounted to the
medical tool.
100291 It should be noted that the above described embodiments of the
invention
apply also for the method of operating the computer assisted surgery system,
the
computer assisted surgery system, the program element as well as the computer
readable medium.
10030] It should also be noted that the above feature may also be combined.
The
combination of the above features may also lead to synergetic effects, even
if' not
explicitly described in detail.
100311 These and other aspects of the present invention will become apparent
from
and elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
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[0032] The present invention will be better understood on reading the
following
detailed description of non-limiting embodiments thereof, and on examining the
accompanying drawings, in which:
[0033] Fig. 1 illustrates a computer assisted surgical system.
[0034] Fig. 2 illustrates a medical tool having fixed thereon a reference body
and an
implant including an intramedullary nail and a bone screw.
100351 Fig, 3 illustrates the implant being separated from the medical tool
shown in
Fig. 2.
[0036] Fig. 3a illustrates the reference body shown in Fig. 3.
[0037] Fig. 3b illustrates an end view of the reference body shown in Fig. 3.
[0038] Fig. 4a illustrates a virtual representation of the implant.
100391 Fig. 4b illustrates a real position of the implant.
[0040] Fig. 5 illustrates a virtual representation of a bone screw and a real
position
of a nail.
100411 Fig. 6 illustrates a virtual representation of a bone screw and a nail.
[0042] Fig. 7a illustrates a deviation to a first direction of a virtual nail
and a virtual
screw as shown by the arrows provided.
[0043] Fig. 7b illustrates a deviation to a second direction of a virtual nail
and a
virtual screw as shown by the arrows provided.
100441 Fig. 7c illustrates a correct position of a virtual nail and a virtual
screw.
100451 Fig. 7d illustrates a final position of a real nail and a real screw.
[0046] Fig. 8a illustrates a deviation to a first direction of a real nail and
a virtual
screw as shown by the arrows provided.
[0047] Fig. 8b illustrates a deviation to a second direction of a real nail
and a virtual
screw as shown by the arrows provided.
[0048] Fig. 8c illustrates a correct position of a real nail and a virtual
screw.
100491 Fig. 8d illustrates a final position of a real nail and a real screw.
100501 Fig. 9a illustrates a virtual representation of a variety of different
geometries,
i.e. inclination angles of a screw with respect to a nail.
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[00511 Fig. 9b illustrates a virtual representation of a variety of different
geometries,
i.e. inclination angles of a screw with respect to a nail.
100521 Fig. 10 illustrates a virtual representation of a variety of different
geometries,
i.e. lengths of a screw with respect to a real nail.
100531 Fig. 11 illustrates a schematic flow diagram of the method for
operating a
computer assisted surgical system.
DETAILED DESCRIPTION
(00541 Fig. 1 illustrates a computer assisted surgery system 1. A patient 2
can be
positioned in or on the computer assisted surgery system so that application
of a
medical device to be applied, such as an implant, for example, can be
assisted. The
computer assisted surgery system of Fig. I illustrates a configuration for the
implantation of the intramedullary nail in the femur of the patient 2. For
this purpose,
an imaging device 3 is provided in order to deliver images from the location
of the
anatomical structure for which the application of the implant is intended. The
computer assisted surgery system further comprises a display unit 4 as well as
a
computation unit 5 so that the correct position of the medical device and
implant,
respectively, can be computed and displayed on the display unit. Thus, the
surgeon
receives assistance in applying an intramedullary nail and a respective bone
screw.
for example, so that the total incision time can be reduced and the position
of the
implant can be improved.
100551 Fig. 2 illustrates a medical application tool 10 in form of an aiming
tool. The
aiming tool comprises a finger grip I I and a coupling portion 15 for coupling
a
medical device 200 to he applied. This medical device in Fig. 2 is an
intrarnedullary
nail 200. This intramedullary nail has an upper portion 201 also comprising a
coupling portion 205 for coupling the intramedullary nail to the coupling
portion 15
of the medical tool 10. In the embodiment shown in Fig. 2, the intramedullary
nail
200 comprises an orifice 202 provided in the upper shaft portion 201 of the
intramedullary nail. This orifice 202 serves for receiving a bone screw 210.
The
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intramedullary nail further comprises a lower shaft portion 203 comprising a
further
orifice 204 for receiving a distal fixation screw 220. The bone screw 210 is
designed
to extend into the neck of femur bone. For this purpose, the bone screw 210 is
provided with a gear shaft 211 for a fixation in the bone material. Further,
the bone
screw is provided with a fixation arrangement 216, so that the bone screw can
be
fixed within the intramedullary nail 200. This fixation can be carried out by
an
internal screw along the longitudinal extension of the intramedullary nail in
the upper
shaft portion 201 so as to fix the position of the bone screw 210 with respect
to the
intramedullary nail 200. Further, the bone screw 210 can be provided with a
receptacle 215 for receiving a respective tool, e.g. a screw driver, for
turning the
bone screw 210 into the bone, for example the femoral neck.
100561 In Fig. 2, a reference body 100 is fixed in a predetermined manner onto
the
medical tool 10. The reference body comprises a finger grip 101 for an easier
fixation and positioning of the reference body. The reference body further
comprises
a plurality of fiducial markers 102. These markers are distributed over the
reference
body in a predefined manner in order to give a unique representation in any
two-
dimensional projection, so that a single fluoroshot image may be sufficient
for
determining the unique 3D-position of the reference body 100. As the reference
body
100 is fixed to the medical tool 10 in a predefined manner, also with respect
to the
intramedullary nail 200, the known orientation, location, and in general
position of
the reference body 100 at the same time represents the position of the
intramedullary
nail 200. In case, the geometry of the intrarnedullary nail 200 is known, also
the
position of the bone screw 210 and the distal locking screw 220 is predefined
at least
for the direction of the longitudinal extension thereof. Thus, the positioning
of the
medical tool 10 together with the reference body 100 allows for determining
the
position of the intramedullary nail 200 as well as at least the longitudinal
extension
direction of the bone screw 210 and the distal locking screw 220, irrespective
of the
visibility of the intramedullary nail in a fluoroshot image, for example. In
order to
determine whether the reference body 100 is correctly positioned with respect
to the
medical tool 10, also the medical tool 10 can be provided with a plurality of
fiducial
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markers 12, so that the correct position of the reference body with respect to
the
medical tool 10 can be determined by evaluating a single fluoroshot image.
100571 Fig. 3 illustrates the single elements of the implant portion and the
tool
portion shown in Fig. 2. Fig. 3 illustrates the intramedullary nail 200 in a
released
manner with respect to the medical tool 10. The medical tool 10 comprises a
coupling portion 15 having a unique matching pattern 16 in form of for example
noses for receiving a respective counterpart of the intramedullary nail 206,
205.
Thus, a unique matching position of the intramedullary nail 200 with respect
to the
medical tool 10 can be provided, so that it can be ensured that the reference
body 100
can be used for pre-definitely representing the intramedullary nail 200.
[0058] Fig. 3a illustrates a front view of the reference body 100. The
fiducial
markers 202 are irregularly distributed over the reference body 100, however,
in a
predefined manner, so that a single fluoroshot allows a unique determination
of the
spatial position of the reference body. Fig. 3b illustrates a side view of the
reference
body being separated from the medical tool 10.
100591 When knowing the position of an intramedullary nail 200 with respect to
the
reference body, the variation of the position of the reference body, here
mounted
onto the medical tool 10, can be used to determine a future position of the
intramedullary nail, even if the nail is not mounted to the medical tool 10.
This can
be seen from Fig. 4a, which illustrates an anatomical structure 300 in form of
a femur
bone having a femur head 330, a femur neck 320 and femur shaft 310. When
positioning the medical tool 10 having mounted thereon the reference body 100.
a
future position of an intramedullary nail can be determined by visualizing a
virtual
representation of the intramedullary nail 200'. It should be noted that for
the
following description, the reference numbers with an apostrophe represent a
virtual
portion of a medical device to be applied, e.g. an implant, wherein the
references
without an apostrophe represent the real medical device, also when already
applied.
[0060] When positioning the medical tool 10 onto the top of the femur bone,
the
modification of the position of the medical tool together with the reference
body 100
allows determining a virtual representation of the later applied medical
device. When
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having found the correct position of the medical device to be implanted, as
shown in
Fig. 4a, a respective guide wire 400 can be applied to the femur bone so as to
fix the
point of entry, which belongs to an optimal position of the medical device to
be
applied. Then, the medical tool 10 can be removed while remaining the guide
wire
400 at the femur bone 300. Thus, the entry point is fixed in order to apply a
drilling
device or an awl for opening the respective entering point of the femur bone.
After
the drilling, the real intramedullary nail 200 can be coupled to the medical
tool 10 in
order to insert the intramedullary nail into the femur bone 300, in particular
the
femur shaft 310, as can be seen from Fig. 4b.
100611 The reference body may also be mounted to an awl or bore tool, or to a
targeting tool for representing an awl. When providing an awl with a reference
body,
the future position of the nail can be predicted based on the trajectory of
the awl.
Thus, the future position of the nail can be determined when producing the
bore hole.
e.g. by an awl or a drilling tool. In other words, it is possible to determine
the future
nail position in situ when drilling the hole for the nail.
1006211t should be noted that according to the known geometry of the
intramedullary nail and the predefined coupling of the intramedullary nail 200
to the
medical tool 10 via the predefined coupling arrangement 205, 206, 15, 16, also
the
direction of the bone screw 210 is defined as well as the direction of the
distal
locking screw 220.
10063] Fig. 5 illustrates starting from Fig. 4b having inserted the real
intramedullary
nail 200, the virtual representation of the bone screw 210' and the locking
screw 220'.
Although the exact position of the bone screw as well as the locking screw can
be
varied, the longitudinal direction and orientation thereof is predefined by
the orifices
202, 204 of the intramedullary nail. Thus. when having inserted the
intramedullary
nail, a virtual representation of the bone screw 210' can be used in order to
determine
the correct position of the intramedullary nail with respect to a longitudinal
translation as well as a rotation with respect to the longitudinal axis of the
intramedullary nail. It should be understood, that also the intramedullary
nail 200 can
be provided with a unique geometry allowing the defined determination of the
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position of the intramedullary nail, i.e. the location, the dimension, and the
orientation thereof. In other words, when using the real intramedullary nail
200 as a
reference body, an additional reference body 100 on top of the medical tool
may be
left out, as the intramedullary nail then may serve as a reference body for
the hone
screw 210' to be applied as well as a distal locking screw 220' to be applied.
[0064] Fig. 6 illustrates a virtual representation of the intramedullary nail
200'
together with a virtual representation of the bone screw 210' and the distal
locking
screw 220'. As the position of the bone screw 210' is defined by the
orientation
thereof with respect to the intramedullary nail 200', the positioning of the
medical
tool can be used to find the correct position of the intramedullary nail as
well as the
bone screw. By repositioning of the medical tool 10, the virtual
representation of the
intramedullary nail 200' together with the bone screw 210' varies, so that the
correct
position not only of the intramedullary nail but also of the bone screw can be
determined. This allows for example to determine the correct axial
displacement of
the virtual intramedullary nail 200' in order to find the correct position of
a virtual
bone screw 210' to maintain certain distances between the bone screw and the
hone
surface of the femoral neck 320. This will be described in greater detail with
respect
to the following figures.
100651 Fig. 7a illustrates a virtual position of the intrarnedullary nail 200'
together
with the virtual representation of the bone screw 210'. However, the virtual
representation of the implants, the intramedullary nail as well as the bone
screw,
illustrates a position, which is not sufficient for a final insertion of the
intramedullary
nail as well as the bone screw, as the distances of the intramedullary nail to
the
surface of the femur shaft as well as the distance of the bone screw to the
surface of
the femur neck are too narrow (see arrows). Thus, the position of the medical
tool 10
has to be modified in order to find a better positioning.
[0066] Fig. 7b illustrates a repositioning, however, this positioning is also
not
suitable for a final insertion of the implant, as the virtual representation
of the
intramedullary nail 200' as well as the virtual representation of the bone
screw 210' is
again too narrow to the surface of the femur shaft 310 and the femur neck 320,
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respectively. After a further repositioning, according to Fig. 7c, a correct
position of
the virtual intramedullary nail 200' and a virtual representation of the bone
screw
210' is achieved, so that the correct position can be fixed, for example by
applying a
guide wire 400. After having fixed the correct point of entry, the entire real
implant,
i.e. the intrarnedullary nail 200 and the bone screw 210 can be applied to the
femur
bone 300 in the previously determined position. It should be noted that
according to
the unique representation of the reference body 100, uniquely representing the
intramedullary nail as well as the direction of the bone screw, no further
fluoroscopic
shots are required between Figs. 7a and 7c. Another fluoroscopic shot may be
taken
if controlling the final implant position is desired to confirm a successful
implantation thereof, as illustrated in Fig. 7d.
100671 As shown in Fig. 7c. in the case where the correct point of entry is
determined, the intramedullary nail 200 can be coupled to the medical tool 10
and
then can be inserted into the femur shaft 310. Either the intramedullary nail
200 or
the reference body 100 or both, the reference body 100 and the intramedullary
nail
200, can be used as a reference body 100 in order to virtually represent the
bone
screw 210' and a virtual representation of the distal locking screw 220'. By
repositioning the medical tool 10 together with the intramedullary nail 200.
the
correct future position of the bone screw 210' can be determined.
100681 Figs. 8a to 8d illustrate the placement of a virtual representation of
a hone
screw 210' when having positioned a real nail 200. Fig. 8a illustrates an
insufficient
position with respect to the low distance between the virtual bone screw 210'
to the
surface of the femur neck 320 (arrows), whereas Fig. 8b illustrates a counter-
positioned insufficient positioning with respect to the other side of the
femur neck
(arrows). Fig. 8c illustrates a better position of the intramedullary nail 200
with
respect to the virtually representation of the bone screw 210', so that the
real bone
screw 210 can be inserted as shown in Fig. 8d. It should be noted that the
reference
body 100 can also be used to represent for example a boring tool in order to
provide
a bore hole into the shaft of the femur neck 310, so that during the drilling
process,
the correct position of the driller can be monitored without the need for
single
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fluoroshot images during the drilling procedure. The reference body may also
represent the nail 200' when drilling a bore hole so that the correct
positioning of the
nail can be monitored when drilling the hole for receiving the later nail.
This
monitoring of the drilling procedure is similar to the illustration of Fig. 8a
to 8c,
wherein the intramedullary nail 200 then is replaced by a driller, whereas the
virtual
representation of the bone screw 210' may be maintained in order to ensure the
correct position of the bone screw 210.
100691 It should be noted that the computer assisted surgery system may also
assist
in finding a better position or orientation of the reference body 100. 200.
This can
happen by giving detailed instructions to the surgeon in which the aiming tool
direction should be moved to find the correct position. It is also possible to
give a
haptic feedback to the handgrip of the aiming tool, for example, so that the
surgeon
can directly recognize in which direction he should move the aiming tool. For
this
purpose respective actors can be placed to the handle or grip.
100701 Fig. 9a illustrates the visualization of the virtual representation of
an
intramedullary nail having a varying geometry of the orifice 202. By selecting
a
respective virtual intrarnedullary nail 200', the inclination of the bone
screw 210' can
be varied to a steeper position 210a' or a less inclined position 210b'. Thus,
by
virtually representing a variation of possible intramedullary nails allowing
different
inclination angles of the bone screw 210', the correct type of intramedullary
nail can
be selected in order to achieve the correct positioning of the later implanted
bone
screw 210. This selection can be carried out by the computer assisted surgical
system
when searching for an optimum geometry in the database and proposing the
respective type of implant.
100711 In practice stereotaxis with intra-operative X-ray imaging is used,
wherein an
awl 9 provided with a reference body 100 may be used to drill a bore hole for
the
nail, as illustrated in Fig. 9b. The system may detect the reference body 100
of the
awl 9 and thus knows the axis of implant 200', e.g. the axis of the gamma
nail/intramedullary nail in 3D space. When having entered the bone for a
certain
distance, the trajectory of the awl 9 is substantially determined. However,
slight
CA 02732970 2011-02-28
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corrections may be carried out depending on the depth of the awl. By producing
two
two-dimensional images, e.g. one in the AP-direction and one in the ML-
direction,
the anatomic structure can be visualized together with the already entered
awl. In ML
view, the system segments femoral head and thus knows the centre of the
femoral
head, and is thus able to calculate correct rotation of implant in ML view. In
AP
view, the system overlays implant with correct axis rotation as calculated in
ML,
performs automatic segmentation of femoral head, thus calculates the centre of
the
femoral head (or the Apex). The virtual representation of the nail allows to
rotate
and/or to translate the reference body so as to find the optimized position
for the nail.
The system then may virtually move the implant e.g. the nail along the
trajectory
corresponding to the nail axis until trajectory of bone screw, e.g. for 125
inclination
angle between nail 200' and bone screw 210' as default, runs through head
centre (or
Apex) and displays, in addition to the default type, all other available types
of
implant. This may be carried out by a software tool. The optimal nail position
and
optimal nail type may be determined automatically by the computation device
based
on the available data sets of the data-base so that the surgeon may receive a
proposal
for the nail position and the nail type, as well as the corresponding bone
screw and/or
the distal locking screw. Optionally the user may interact with the system to
adapt
entry depth of nail. Optionally the system may present a 3D reconstruction of
whole
scenery. The already introduced awl provides for a stable position in the bone
so that
the future position of the intramedullary nail can be provided. Further. the
rigid
position of the awl allows maintaining the position in the operation process.
In other
words, the entire work flow of the operation will not be disturbed when using
the
computer assisted surgery system. It should be noted that the illustrations of
Figs. 2
to 10 are illustrations in the AP-direction, and that corresponding
illustrations may
also be obtained in ML-direction to be fed with the computational unit 5.
[00721 Fig. 10 illustrates in a similar way the selection of the correct bone
screw 210
out of a variety of bone screws, so that the required distances of the bone
screw to
the surface of the femur head 330 can be maintained. Fig. 10 illustrates two
possible
lengths of a bone screw 210' and 2 IOc', wherein the system based on the rules
for
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allowable ranges should select the position 210', as the longer bone screw
210c' does
not maintain the required distance to the surface of the bone head 330.
[0073] Fig 11 illustrates the method for operating a computer assisted surgery
system. The method comprises the positioning S 10 of a reference body 100, 200
in
relation to an anatomical structure 300, the reference body virtually
representing a
position of a medical device 200. 210. 220 to be applied to the anatomical
structure,
detecting S20 a position of the reference body in relation to the anatomical
structure.
superimposing S30 the anatomical structure with a virtual representation 200':
210',
220' of a medical device to be applied, based on the detected position of the
reference body in relation to the anatomical structure, providing rules S40
for
allowable ranges for applying the medical device in relation to the anatomical
structure, modifying S50 the position of the reference body and optimizing S60
the
virtual position of the medical device to be applied with respect to the
anatomical
structure so as to obtain a best fit with respect to the rules for allowable
ranges.
Detecting S20 the positioned reference body 100; 200 in relation to an
anatomical
structure may further comprise taking two 2-dimensional images from different
angles S21, generating a 3-dimensional representation based on the two 2-
dimensional image S22, and determining a spatial position of the reference
body in
relation to the anatomical structure based on the 3-dimensional representation
S23.
Modifying S50 may comprise rotating S51 and/or displacing S52 of the reference
body 100; 200, as well as selecting the medical device 200: 210. 220 out of a
predetermined group of a variety of medical devices S53.
[0074] In another embodiment of the present invention, a computer program or a
computer program element is provided that is characterized by being adapted to
execute the method steps of the method according to one of the preceding
embodiments, on an appropriate system.
[00751 The computer program element might therefore be stored on a computer
unit,
which might also be part of an embodiment of the present invention. This
computing
unit may be adapted to perform or induce a performing of the steps of the
method
described above. Moreover, it may be adapted to operate the components of the
CA 02732970 2011-02-28
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above described apparatus. The computing unit can be adapted to operate
automatically and/or to execute the orders of a user. A computer program may
be
loaded into a working memory of a data processor. The data processor may thus
be
equipped to carry out the method of the invention.
100761 This embodiment of the invention covers both, a computer program that
right
from the beginning uses the invention and a computer program that by means of
an
up-date turns an existing program into a program that uses the invention.
10077] Further on, the computer program element might be able to provide all
necessary steps to fulfill the procedure of an embodiment of the method as
described
above.
100781 According to a further embodiment of the present invention, a computer
readable medium, such as a CD-ROM, is presented wherein the computer readable
medium has a computer program element stored on it which computer program
element is described by the preceding section.
100791 However, the computer program may also be presented over a network like
the World Wide Web and can be downloaded into the working memory of a data
processor from such a network. According to a further embodiment of the
present
invention, a medium for making a computer program element available for
downloading is provided, which computer program element is arranged to perform
a
method according to one of the previously described embodiments of the
invention,
[0080] It has to be noted that embodiments of the invention are described with
reference to different subject matters. In particular, some embodiments are
described
with reference to method type claims whereas other embodiments are described
with
reference to the device type claims. However, a person skilled in the art will
gather
from the above and the following description that, unless otherwise notified,
in
addition to any combination of features belonging to one type of subject
matter also
any combination between features relating to different subject matters is
considered
to be disclosed with this application. However, all features can be combined
providing synergetic effects that are more than the simple summation of the
features.
CA 02732970 2011-02-28
-19-
[00811 It has to be noted that embodiments of the invention are described with
reference to different subject matters. In particular, some embodiments are
described
with reference to apparatus type claims whereas other embodiments are
described
with reference to method type claims. However, a person skilled in the art
will gather
from the above and the following description that, unless other notified, in
addition
to any combination of features belonging to one type of subject matter also
any
combination between features relating to different subject matters, in
particular
between features of the apparatus type claims and features of the method type
claims
is considered to be disclosed with this application.
100821 In the claims, the word "comprising" does not exclude other elements or
steps, and the indefinite article "a" or "an" does not exclude a plurality. A
single
processor or other unit may fulfill the functions of several items re-cited in
the
claims. The mere fact that certain measures are re-cited in mutually different
dependent claims does not indicate that a combination of these measures cannot
be
used to advantage.
[00831 A computer program may be stored and/or distributed on a suitable
medium.
such as an optical storage medium or a solid state medium supplied together
with or
as part of other hardware, but may also be distributed in other forms, such as
via the
internet or other wired or wireless telecommunication systems.
