The invention relates to a medical auxiliary instrument for introduction into the body of a patient, to the use of such an auxiliary instrument, to a positioning system for percutaneous interventions, and to a method for determining a reference position for such a positioning system.
Image-assisted interventions, in particular CT-assisted interventions, are nowadays part of clinical routine. In contrast to invasive surgical treatment, minimally invasive image-assisted interventions allow the operator to work with minimal injury to the patient. This does not just reduce the clinical costs. It also reduces the danger of complications and has a positive cosmetic effect.
To carry out these image-assisted interventions, it is necessary to navigate medical instruments through the inside of the patient's body. The term navigation is understood as determining the position by locating means, planning the access route to the target site and guiding a medical instrument to this target site along the planned access route. For this purpose, it is known to arrange electromagnetic coils both on the medical instrument and on the patient's body. When these coils are exposed to an electromagnetic field generated for this purpose, a current flow is induced in these coils. These current signals are detected and are used to determine the position of the medical instrument and thereby to navigate the latter; the coil provided on the medical instrument itself indicates the position of the medical instrument, and the coils arranged on the body of the patient serve as reference markers.
It has hitherto been customary for these reference coils to be secured, for example affixed, to the patient's skin. In complex interventions, particularly in the area of the spinal column, this type of positioning of the reference coils is too imprecise for an exact navigation of the medical instrument, however. The reason for this is that movements of the surface of the patient's body cannot be completely avoided. Reference coils therefore started to be secured directly to the patient's bone, for example using nails, clamps or screws. However, this requires invasive interventions in the patient, for which reason such a positioning of reference coils is very complex and risky and, in addition, the above-mentioned advantages of a minimally invasive intervention are for the most part negated.
It is an object of the present invention to permit a particularly safe, minimally invasive percutaneous intervention, in particular in the area of the spinal column.
This object is achieved by a medical auxiliary instrument for introduction into the body of a patient, with a tube and with a trocar element arranged in the tube, wherein the trocar element has at least one marking element which is designed such that its position can be determined by means of a contactless locating method, and wherein the tube has, at one end, a securing device for establishing a releasable mechanical connection to a tissue part of the patient in such a way that, when the connection to the tissue part is established, the position of the marking element serves as a reference marker for a positioning system for percutaneous interventions.
This object is also achieved by a positioning system for percutaneous interventions, with a medical auxiliary instrument for introduction into the body of a patient, wherein the medical auxiliary instrument has a tube and a trocar element arranged in the tube, wherein the trocar element has at least one marking element which is designed such that its position can be determined by means of a contactless locating method, and wherein the tube has, at one end, a securing device for establishing a releasable mechanical connection to a tissue part of the patient in such a way that, when the connection to the tissue part is established, the position of the marking element serves as a reference marker for the positioning system.
Finally, this object is also achieved by the use of a medical auxiliary instrument, as specified above, for providing a reference position for a positioning system for percutaneous interventions, and by a method for determining a reference position for a positioning system for percutaneous interventions, with the steps of: introducing at least one medical auxiliary instrument, as specified above, into the body of a patient, establishing a mechanical connection between the tube of the auxiliary instrument and the tissue part of the patient, and determining the position of the marking element of the auxiliary instrument by means of a contactless locating method.
A fundamental idea of the invention is for a marking element acting as reference marker to be positioned minimally invasively in the interior of the patient's body. This reference marker is preferably intended to be used for a positioning system for carrying out a computer-navigated percutaneous intervention, in particular for the navigation of a medical instrument, for example a cutting instrument or a biopsy needle, in the patient's body.
This is done using a medical auxiliary instrument which is designed in the manner of a trocar and which comprises a tube, a trocar element and a corresponding marking element. A tube is understood here as a structural part in the form of a hollow cylinder having a substantially tubular shape. The tube is preferably rigid. This permits particularly simple and safe positioning in the interior of the body. The tube can also be pliable and flexible if the trocar element is designed accordingly.
According to the invention, the marking element is brought with the auxiliary instrument to its intended site in the interior of the patient's body. In contrast to the prior art, the reference marker is arranged in the patient, and the medical instrument navigated, in a minimally invasive manner. Except for the additional openings for insertion of one or more auxiliary instruments according to the invention into the body of the patient, no other interventions are needed for fixing the reference system of the positioning system. By means of the present invention, therefore, a reference coil is placed in or directly at the target site, for example a bone tissue of the patient, without this requiring complicated interventions.
Whereas in the case of conventional biopsy needles, for example, the needle is provided exclusively for positioning the needle sleeve, i.e. basically for penetrating through the patient's skin and forming the admission channel, and is then removed again as soon as the sleeve is located at the desired site, in the present invention the positioning of the trocar element in the tube is essential to the function of the auxiliary instrument. The trocar element remains in the tube at least until the marking element has been once located.
By means of the present invention, it is possible, even with just a single auxiliary instrument according to the invention, to make available a reference system that is sufficient for safe navigation. The fixing to the bone of the patient means that no dynamic recording is necessary. After the position of the marking element has been fixed, the reference system only has to be measured again for monitoring purposes or in the event of the position of the patient having changed, for example after transport.
With an image-assisted navigation system of the kind provided according to the invention, it is possible to perform minimally invasive interventions in which even the very smallest target areas in the interior of the body can be reached safely and with precision. The invention can be used in all image-assisted interventions and treatments in which medical instruments have to be moved inside the body, particularly for the percutaneous advance of a needle to a defined anatomical position in the patient. Areas of application include biopsy procedures for removal of tissue that requires examination.
Advantageous embodiments of the invention are set forth in the dependent claims.
Particularly advantageous handling of the medical auxiliary instrument is ensured if the marking element is arranged completely within the interior of the trocar element. This means that the external diameter of the preferably pin-shaped or needle-shaped trocar element can be adapted to the internal diameter of the tube in such a way that the trocar element closes the tube substantially completely. The tube can then be more easily advanced in the tissue, and it is possible to avoid damage to the body tissue, as could occur in the case of a tube that was closed incompletely.
The marking element is preferably arranged at one end of the trocar element, this end preferably being the end of the trocar element that closes an end opening of the tube at the end of the tube comprising the securing device. This ensures that the marking element is located in or on the tissue part or at least in immediate proximity to the tissue part which is mechanically connected to the tube when the latter is fitted in place. This permits particularly exact navigation of a medical instrument relative to the tissue part, on the basis of the signals from the marking element serving as reference.
In another embodiment of the invention, the trocar element has a second marking element which is arranged at a distance from the first marking element, preferably at the opposite end of the trocar element. By using more than one marking element, it is possible to define the reference coordinate system necessary for navigation, without a further auxiliary instrument being needed to do so.
The marking elements used are preferably elements whose position can be determined by means of an electromagnetic locating method, in particular electromagnetic coils. The use of such marking elements has proven particularly safe, robust and reliable in the past. Alternatively, however, other marking elements can also be used, for example permanent magnets that serve as markers for determination of position by means of a locating method based on a purely magnetic technique.
The securing device on the tube is preferably a device designed for a releasable connection to a bone tissue, in particular a cutting thread, preferably in the form of an outer thread. However, alternative forms are possible here too, for example of such a type that a clamped connection is established instead of a screwed connection.
To ensure that the auxiliary instrument according to the invention can be used for determining a reference position in a positioning system, the auxiliary instrument is first introduced into the body of the patient. For this purpose, the trocar element can have a tip which protrudes from the front end of the tube and which ensures particularly easy introduction into the patient's body. Thereafter, the mechanical connection is established between the tube and the tissue part of the patient. In the case of a screw thread, this is done by rotating the tube, as a result of which the latter is turned into the bone of the patient. The position of the marking element is then determined, for example with the aid of the current signal of an electromagnetic coil serving as marking element in an external electromagnetic field applied for this purpose.
Illustrative embodiments of the invention are explained in more detail below with reference to the drawings, in which:
In all the figures, the invention is only shown schematically and with its principal components.
An example of a medical auxiliary instrument 10 according to the invention for introduction into the body of a patient is shown in
A marking element in the form of an electromagnetic reference coil 16 is arranged completely within the interior of the trocar element 12. This reference coil 16 is designed in such a way that its position can be determined by means of a contactless electromagnetic locating method and thus corresponds in principle to the reference coil 4 shown in
The tube 11 is open at both ends and has, at one end 18, a securing device in the form of an external cutting thread 19 for forming a releasable mechanical connection to the bone 3. In order to establish a connection to the bone 3, the auxiliary instrument 10 is pressed with its tip 13 into the bone tissue. The tube 11 is then turned in the direction of rotation 9 about its axis of rotation 20, which at the same time is its longitudinal axis, such that the cutting thread 19 is turned into the bone 3 and the tube 11 is fixed in the bone 3.
When the connection to the bone 3 has been established, the position of the reference coil 16 on or in the bone 3 serves as a reference marker for the positioning system 100.
The reference coil 16 is located in the pointed end 13 of the trocar element 12 that closes the opening 15 of the tube 11 facing in the connection direction 14. When the tip 13 has been forced into the bone 3 of the patient, a point located in immediate proximity to the bone surface is consequently used as a reference point in the reference coordinate system of the positioning system 100. This permits particularly safe navigation of the biopsy needle 1 or of another medical instrument to the bone 3.
To ensure that the reference coordinate system of the positioning system 100 can be defined unambiguously, two reference coils 16 are required. If only a single reference coil 16 were used, the position of the rotation axis 20 would be known, but not the angle position of a point remote from this axis. For this reason, a second reference coil 16′ is used whose longitudinal axis does not extend parallel to the longitudinal axis of the first reference coil 16. In this way, the angle position of a point situated remote from the rotation axis 20 can also be determined unambiguously. Evaluation of the measured data is particularly simple if the second reference coil 16′ is arranged at an angle of 90° with respect to the first reference coil 16.
The second reference coil 16′ can now be arranged as a further coil in the same auxiliary instrument 10, as is shown in
Applying reference coils in the area of the cervical spine has proven particularly difficult in the past. In the prior art, such coils are applied by means of clamps that are secured on the vertebral body, cf. the clamp 22 indicated by broken lines in
The use of the present invention is therefore particularly recommended in the area of the spinal column, in particular in the area of the cervical spine. Two auxiliary instruments 10, 10′ are preferably secured on the two transverse processes 23 of the vertebral body 24 (
In contrast to a trocar in which the trocar element is removed from the tube after introduction into the body and the operating surgeon, after withdrawing the trocar element from the tube, has the possibility of introducing an optical instrument or a gripping, cutting or other medical instrument into the body, it is not necessary, for the purposes of the invention, to remove the trocar element 12 from the tube 11. However, after the reference coil 16 in the tip 13 of the trocar element 12 has been located, the trocar element 12 can be removed from the tube 11, such that the tube 11, as in a normal trocar, can then be fitted with other trocar elements, for example a biopsy needle 1.
All of the features set forth in the description, in the appended claims and in the drawing can be considered essential to the invention both individually and also in any desired combination with one another.
Number | Date | Country | Kind |
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10 2006 037 604.8 | Aug 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/007013 | 8/8/2007 | WO | 00 | 2/10/2009 |