Surgery – Instruments
Reexamination Certificate
1999-09-09
2001-10-23
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
C073S865900, C073S001750, C073S001790, C073S001010
Reexamination Certificate
active
06306126
ABSTRACT:
The present invention relates to a calibrating device for detecting the position, firstly, of the axis of the shank (axis of action) and, secondly, of the front end (point of action, line of action or area of action) of a surgical instrument relative to an emitter mounted on the instrument.
Modern imaging methods such as x-ray tomography and nuclear magnetic resonance are nowadays an important aid in surgery. It is particularly helpful if the surgical instruments used together with the image of the patient can be shown on a screen during surgical interventions. For this purpose, the position of the surgical instruments relative to the patient must be measured continuously during the operation.
One conventional method is to use a stereotactic frame. The stereotactic frame is attached firmly to the patient and the surgical instruments are secured on the frame, allowing their position relative to the patient to be determined in a simple manner. There is a description of stereotactic frames in the brochure “Stereotactic Treatment Planning” issued by Howmedica Leibinger GmbH in 1996. There is a survey of various systems in the article entitled “Neuronavigation: A ten-year review” by Hans F. Reinhardt in the book “Computer-integrated surgery” by R. H. Taylor, S. Lavallee; G. C. Burdea, R. Mosges; Cambridge/Mass., London/England: The MIT Press (1966), Page 329ff.
However, attaching a stereotactic frame to the patient is very involved and unpleasant for the patient.
In more modern systems, therefore, the position of a surgical instrument is measured by infrared radiation (“navigator”). In this method, the position of the patient and the position of the surgical instrument are determined separately and then correlated. A system of this kind is shown, for example, in the brochure entitled “Experience new perspectives—with the OPM® Neuro 200 system”, Carl Zeiss, D-73446 Oberkochen.
The position of the patient is measured as follows: four screws, for example, provided with marking balls containing a contrast agent are first of all inserted into the patient. These marking balls can be seen on a CT recording and can thus serve as a reference point. During the operation, the marking balls are then removed, and a so-called navigation pointer is inserted at precisely the correct location into a remaining hollow. The navigation pointer has infrared LEDs, the radiation of which is recorded by a CCD camera situated, for example, over the operating table. Since a plurality of diodes are emitting radiation simultaneously, the system can calculate the position of the tip of the navigation pointer and hence the position of the hollow. If this method is carried out for all four screws, four points on the patient are associated with a clearly defined spatial position, it being possible for the system to calculate the spatial position of the patient from just three points, the fourth point acting as a control point.
The position of the surgical instrument is determined in a similar manner with infrared radiation. An emitter having LEDs, the position of which in space can be calculated by means of the data supplied by the CCD camera, is mounted on the rear part of the surgical instrument (e.g behind the handle). If the computer system knows the position of the tip of the instrument relative to the emitter, it can likewise calculate the position of the tip of the instrument in space (or of some other point of action) and the instrument can be shown on the computer screen together with the CT image. Since the emitter is connected firmly to the surgical instrument, the position of the tip of the instrument relative to the emitter need only be determined once, and the corresponding data are input into the computer system. However, calibration in this way has hitherto been very involved since it cannot be performed by the surgeon himself.
It would be desirable for the surgeon to be able to connect a wide variety of surgical instruments firmly to an emitter before or during an operation and to be able to quickly perform the calibration himself. Hitherto, there have been no methods for such calibration because surgical instruments have a very wide variety of shapes. In particular, not all surgical instruments have a tip (point of action). The end of the instrument can, for example, also be an edge (line of action), as in the case of a chisel, or be spoon-shaped. In the case of a tube, the end of the instrument has an area of action. Another difficulty in ascertaining the end of the instrument is that the axis of the shank of the instrument, i.e. the axis of action, which can, for example, be an axis of rotation, may be bent relative to the rear part of the instrument. A surgical instrument of this kind, with a bent shape, is particularly difficult to calibrate. It would therefore be desirable if it were also possible to determine the position of the axis of action during calibration.
EP 0 832 610 A2 describes a calibrating device for determining the position both of the axis of a shank and of the end of a surgical instrument relative to an emitter mounted in the latter. In this case, the distance between the area of action of the instrument and a reference surface is determined by a method in which the reference surface is touched by the tip of the instrument.
It is therefore the object of the invention to provide a calibrating device for determining the position, firstly, of the axis of the shank (axis of action) and, secondly, of the front end of the instrument (point of action, line of action or area of action) of a surgical instrument relative to an emitter mounted on the rear part of the instrument, which device is simple and quick to operate.
The distinguishing features of the calibrating device according to the invention are given in the patent claims.
The calibrating device preferably has: two clamping-device carriers, each with a clamping device, in a clamped state the clamping devices bringing the shank of the instrument into a clearly defined clamped position relative to the calibrating device; a supporting plate on which the front end of the instrument rests in the clamped state; and a reference emitter, the axis of action of the instrument being essentially perpendicular to the supporting plate in the clamped position, and the supporting plate and the reference emitter of the calibrating device being connected firmly to one another.
The calibrating device according to the invention has the advantage that it can be operated in situ by the surgeon himself. All that is required is to mount an emitter on the instrument and then bring the instrument into the clamped position in the calibrating device, i.e. the front end of the instrument is resting on the supporting plate and the clamping devices are clamping the shank of the instrument so that the axis of the shank is perpendicular to the supporting plate, more specifically colinear with a calibrating-device axis defined by the clamping devices. The CCD camera now determines both the position of the emitter and the position of the reference emitter of the calibrating device and can thus acquire the position of the axis of the shank and of the end of the instrument relative to the emitter of the instrument. The position of the end of the instrument is determined insofar as the plane in which the end of the instrument lies is calculated.
Preferably, at least one clamping-device carrier can be displaced in the direction perpendicular to the supporting plate. This makes the calibration system more adaptable to different surgical instruments with shanks of different lengths.
Preferably, the supporting plate is arranged on a base plate and four columns extending perpendicular to the supporting plate are attached to the base plate at the corners of a quadrilateral, each clamping-device carrier being fixed to at least one column. The use of a base plate has the advantage that the entire system is made more stable. The columns also help in this respect.
Preferably, the clamping-device carriers are each designed as a plate which has four guide holes for guidanc
Dvorak Linda C. M.
Pearne & Gordon LLP
Ram Jocelyn Debra
Stryker Leibinger GmbH & Co KG
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