Abstract:
The invention relates to a surgical instrument comprising a handle portion and a tip, wherein a tip sensor is provided on the handle portion. The tip sensor enables detection of when a tip is inserted into and/or removed from the handle. In addition, the tip sensor enables a navigation system to be notified when landmarks are probed with the surgical instrument, thereby ensuring accurate capture of the location of the landmark.

Description:
RELATED APPLICATION DATA 
     This application claims the priority of U.S. Provisional Application No. 61/104,799, filed on Oct. 13, 2008, which is hereby incorporated in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a surgical instrument, in particular a pointer instrument. 
     BACKGROUND OF THE INVENTION 
     Pointer instruments are widely used especially in the field of medical navigation, wherein this also applies to the instruments in accordance with the invention as described here. One specific type of use is to move the tip of the pointer instrument to points on the patient (landmarks) or on medical auxiliary devices, wherein calibrated or pre-calibrated pointer instruments are localized with the aid of a medical tracking system (for example via cameras and position markers on the instrument); the position of the tip of the instrument is thus known and therefore also the position of the landmark or, in very general terms, the point to which the pointer tip is moved. 
     Thus, this results on the one hand in a necessity to calibrate the instrument before it is used and/or a necessity to use a pre-calibrated instrument, the shape and dimensions of which—in particular, the position of the tip—has to be known to the navigation system. On the other hand, using such an instrument with a navigation system is in most cases still very operatively intensive, because the user always has to inform the navigation system that he is currently moving to a landmark, such that its position can be recorded and/or stored. If a number of points are successively recorded or a contour profile is continuously traveled using the pointer tip, difficulties can result because the navigation system constantly has to be informed as to whether the pointer tip is currently lying on the contour to be scanned or is being lifted and transferred to another location. If navigation is not “informed” in good time in the latter case, completely meaningless contour data is recorded during the transfer movement of the pointer. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a surgical instrument, in particular a pointer instrument, which makes handling with a medical navigation system simple and more user-friendly. 
     This object is solved in accordance with the invention by a surgical instrument comprising a handle portion and a tip, wherein a tip sensor is provided on the handle portion. The sub-claims define preferred embodiments of the invention. 
     In accordance with the present invention, a surgical instrument is thus provided, in particular a pointer instrument, which comprises a handle portion and a tip, and a tip sensor on the handle portion. The tip sensor is so-called because it detects various features which are associated with the tip of the instrument and which are explained in more detail below. In other words, the handle portion of the instrument in accordance with the invention is embodied such that it can detect information concerning the instrument tip, and precisely this characteristic of the instrument in accordance with the invention makes handling it very much simpler. For various information concerning the tip and/or its cooperation or interaction with the handle can be used in order to make navigation simpler, less elaborate and more user-friendly, because such information (for example concerning the type of tip or the current load on the tip) can replace information inputs which otherwise have to be made on the navigation system by the user. 
     Although a pointer instrument is a very good example of an instrument in accordance with the present invention, the invention is not limited to such pointer instruments. It can extend its advantages to any possible instruments, and examples of this include a broach comprising a handle and different tips, i.e. broach tips having for example different diameters or lengths. Another example of such a surgical instrument would be a bone saw which can use different exchangeable saw blades with a single handle. 
     In accordance with one embodiment of the present invention, at least one tip can be removably fastened to the handle portion, in particular using a releasable fastening, specifically a plug fastening. A number of tips can be exchangeably fastened to the handle portion, specifically by means of a fastening adaptor which is the same for a number of tips or for all the tips and allows the tips to be simply fastened and therefore also simply exchanged. Once fastened, the tip should sit on the handle rigidly and with zero tolerance. 
     The tip can comprise a handle fastening portion (which can also be the fastening adaptor) which complementarily cooperates with the tip sensor, and in accordance with one embodiment variant of the present invention, the tip sensor comprises a presence sensor for the presence of a tip. The presence sensor will in particular operate automatically, i.e. will determine the presence of a tip without being additionally operated, i.e. without user intervention. 
     It is however possible within the framework of the present invention not only for the presence of a tip to be determined but also for the tip and handle or one of the two elements to comprise a tip identifying device, in particular comprising a recognition device and/or reading-off device for the type and/or characteristics of the tip, wherein the device is assigned to the tip sensor, and comprising a recognition feature on the tip. 
     The tip identifying device can comprise a shape identification and/or shape key (for example in the manner of a door key), an RFID identification and/or a barcode identification. It is possible to embody the instrument such that the tip portion which interacts with the tip sensor, specifically the handle fastening portion comprising the recognition feature, bears information concerning the type and/or characteristics of the tip. 
     In accordance with another aspect of the present invention, the tip sensor comprises a force sensor for the force exerted by a tip on the handle portion. Using this force sensor, it is possible to detect whether the tip is currently pressing against a resistance and therefore whether the instrument is currently ready for use or is being used. It is thus possible for example to determine whether the tip is currently being moved to a landmark in order to detect its position. Detecting the force also allows detection over a longer period of time, such that it is possible to determine whether for example a pointer tip is sliding over a surface in order to detect its contour. The contour would then only be detected as long as a force by the tip on the handle is measured. When the instrument is removed from the surface, a force is also no longer exerted, and this can immediately and automatically switch off the contour detection in the navigation system. 
     Put in general terms, a functional interaction device is provided in a modification of the surgical instrument in accordance with the present invention and transmits data concerning the cooperation of the tip and the handle portion to a medical navigation system in order to assist in image-guided surgery, wherein the functional interaction device can comprise a data communicator, in particular a radio transmitter such as a Bluetooth or high-frequency and/or radio-frequency communicator/transmitter or an infrared, sonic and/or ultrasonic communicator/transmitter. A receiver for said communicated data can of course also be provided in a system attached in accordance with the invention, specifically a receiver for the data of the data communicator, which is connected to the medical navigation system. 
     The instrument can comprise an electrical energy supply, specifically comprising an energy store (battery, rechargeable battery) and/or an energy generator. In one embodiment, the rechargeable battery can specifically be charged in a non-contact process and/or by inductive charging. The energy generator can comprise one or more of the following devices: a piezoelectric energy generator; a thermo-electric energy converter; a solar cell energy converter. 
     In the following—up until the description of the figures—other general information concerning possible embodiments of a surgical instrument in accordance with the invention, specifically a pointer instrument for image-guided surgery, is also given. 
     The handle can be fitted with navigation markers, wherein specifically two or more reflective spherical markers can be provided. The geometry of the spherical marker array is dependent on the maximum length of the instrument tip. As an alternative to spherical markers, flat—for example circular—reflective layers can also be used. 
     As already mentioned, the tip interface is preferably embodied such that it can hold exchangeable tips which should be easy to exchange and fastened rigidly and/or with zero tolerance. With respect to detecting the tip, connected tips can preferably be automatically detected. This can be achieved with the aid of a key mechanism, i.e. the fastening mechanism is embodied like a car or house key which comprises an identification consisting of geometric data and a fixation to a device. The key shape can for example be provided on the tip side, while the handle is formed like a lock. A reverse arrangement is of course possible in principle. 
     If an RFID technique is used for identification, an energy-free RFID chip can be provided on the tip, while the RFID reader is situated in the handle. Alternatively, the reader could also be situated in the navigation station. If a barcode is used as a means of identification, it can be molded to the tip interface (injection-molding) or formed by laser engraving. A simple but durable imprint is of course also conceivable. A simple optical reading device would then be situated in the handle, which operates sequentially (code is read as the tip slides in), completely (code is read as a whole) or using remote detection in which the code is read by the navigation and/or tracking system. To this end, a dedicated reading device can be attached to the navigation and/or tracking system, or the tracking camera is used to read the code. 
     The status of the instrument tip connected to the handle can be regularly transmitted via a communication device, for example once a second, and different status information could be: “no tip provided”; “tip removed”; “tip inserted”; “unknown tip”; “tip detected” or “tip detected and OK”. 
     A certain number of tips can be identified, and it is advantageous for this purpose to store the geometric tip data. The tip data is expediently stored and/or provided either in and/or on the tip itself or in the navigation system. In the former case, the data can be provided, encoded, in an identification device. The key can thus comprise both the identification and the tip data as shape information, and this data can also be stored in barcodes or RFIDs. It is also possible to accommodate all or some of the data in the navigation system, wherein for example the handle determines which tip is attached and the more specific data concerning the tip is then provided in the navigation system. 
     Basic information which comprises a mechanical description of the shape (vector graphics, splines, etc.) can be selected as the data format, or a complete 3D shape description (XML, VFML, STML). As already mentioned, a change of tip can be automatically relayed (detecting the tip, communication device). It is possible to identify a bent tip simply by checking it using the navigation software or by holding or pivoting it on a surface if—which is possible in accordance with the invention—not all the geometric data is stored for example in the software. 
     If a force sensor is used, it will measure the force which is exerted on the tip by measuring the force which passes from the tip to the handle portion. It is possible to indicate the pressure and/or force constantly on a navigation screen or also as an LED display (for example as fluorescent strips on the handle), advantageously comprising a green-yellow-red display sequence which shows non-critical, critical and excessive loads. This measurement of the force and/or pressure can also be used as a “switch”, for example if surface-matching operations are performed and it is necessary to know at each moment whether the tip of the instrument is contacting something. When contacting the skin, the threshold for the force which indicates a contact would be low; in bone scans, this threshold would be higher. By measuring the force in this way, it is also possible to determine whether point acquisition is currently being performed on a bone or on a soft tissue (muscle, skin). 
     Metal or plastics may be considered as materials for the instrument tip; the tips can be disposable. The interface can be embodied as a standard interface for a number of handles or types of handles. 
     The communication between the instrument and the navigation system (IGS system=image-guided surgery system) can be unidirectional, i.e. when the handle is attached, sensor data is transmitted. The communication should have as few so-called line-of-sight problems as possible, which would be ensured in the case of radio communication. Sonic communication is however also conceivable, or infrared communication in which a tracking camera of the navigation system or a separate receiver is used as the receiver. Bidirectional communication is also possible, in which for example errors ascertained by the IGS system are indicated by LEDs on the handle. 
     Different buttons for controlling the navigation software can be attached to the handle, i.e. for example push-buttons, rocker switches or turning knobs (one to three, especially two to three buttons). They can be mechanical or electromechanical in nature or can be sensor buttons. They can have a tactile pattern on their surface so that they can be easily operated using surgical gloves. 
     Energy is needed for example for communication, for the sensor and the buttons, and batteries can be provided which are enclosed by the handle, can be sterilized along with it and exhibit a service life of several years. Exchangeable batteries are also conceivable, as are rechargeable batteries or thermo-electric elements which convert heat energy into electrical energy. The energy during the sterilization process could then in particular be used to charge the electrical energy supply. It is also possible to obtain energy by piezoelectric technology, wherein pressing a button could generate enough energy for example to support communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below on the basis of different embodiments and with the aid of the enclosed drawings. It can comprise any of the features described here, individually and in any expedient combination. It can in particular also comprise specific uses of the devices shown or methods which are performed using them and presented here. 
         FIG. 1  shows a schematic representation of an instrument in accordance with the invention, comprising a number of exchangeable tips. 
         FIGS. 2A and 2B  show a scheme for inductively charging energy. 
         FIG. 3  shows a scheme for thermo-electrically charging the instrument with energy. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows different alternatives of a surgical instrument, i.e. comprising different tips  12 ,  14 ,  16  (wherein the reference sign  10  is also used as a whole for the tip in general) and a handle portion  20 . The tips can be different tips for a surgical pointer, wherein the tip  12  is a long straight tip, the tip  14  is a tip comprising an angled front part and the tip  16  is a rounded tip. All the tips have a fastening portion at the end opposite their front end, and in the case of the tips  12  and  14 , this fastening portion  13  is formed as a key shape portion. The instrument tip  16  has a fastening portion  15  which has been provided with an engraved or imprinted barcode. The fastening portions  13 ,  15  serve on the one hand to fasten the tip to the handle, and on the other hand to identify the tip and to provide data, i.e. shape data, concerning the tip. Thus, the key portion  13  can comprise this data by mechanical shaping, while in the barcode of the portion  15 , the data is accommodated in an encrypted form. 
     The tip  10  is connected by the fastening portion  13 ,  15  (adaptor) to the handle  20  which is shown here rather schematically and (to simplify presentation) somewhat distorted in its dimensions. The fastening portions of the tips  10  are inserted into the tip receptacle  21 , where they are fastened. A first sensor  22  is assigned to the tip receptacle  21  and can on the one hand detect the presence of a tip and on the other hand—in specific embodiments—can also enable the tip to be identified via the information provided by the fastening portions  13 ,  15 . If the receptacle  21  is complementarily formed as a lock for the key shape  13 , a mechanical scan will both detect the presence of the tip and retrieve the additional information. In the case of the tip  16 , the sensor  22  can comprise a barcode reader. 
     Another component in the handle  20  is the force sensor  23 , using which the force and/or pressure which is exerted on the front end of the respective tip is determined via the force which is exerted by the tip on the sensor  23 . As already described, this force information and/or pressure information can be evaluated in different ways, i.e. for example as a “switch” for point acquisition or area acquisition or as load information, wherein it is possible to differentiate whether the pointer is touching soft or hard tissue. 
     The reference sign  25  here represents another device which can be attached to the handle, for example an induction cell or solar cell for obtaining energy or a display (LED display) for the pressure values which are measured using the sensor  23 . The reference sign  27  indicates an energy supply, i.e. a battery or a rechargeable battery, which is connected to the energy-generating or energy-consuming elements in the handle. A connection to the element  25 , which as a solar cell or induction cell and/or piezoelectric cell can provide power to the energy supply  27 , is for example representatively shown. 
     The handle comprises a data communicator or radio transmitter  26  so that information and/or data can be relayed from the handle. As indicated, all the elements and/or sensors  22 ,  23 ,  25  and the buttons  24  provided (for controlling the navigation software) are connected to said data communicator and/or radio transmitter  26  and provide it with data which it can relay to a navigation system, wherein the transmitter  26  of course consumes energy and is therefore likewise connected to the battery and/or rechargeable battery  27 . Transmitted data can be identification data for the tips or pressure and/or force data of the sensor  23 , or commands which are input via the buttons  24 , or status data (level of charge in the rechargeable battery). The instrument can be a navigated instrument, as follows from the reference array  28  which is fastened to the handle and comprises three reflective spherical markers. 
     In a simple application scenario, the fastening portion  13  of the tip  12  is inserted into the receptacle  21  of the handle  20 . The tip  12  is identified via the key information in the fastening portion  13  which is read off by the sensor  22 . The data concerning the length of the tip and its shape is either provided directly by the information in the fastening portion  13  or is stored in the navigation system. Using this information concerning the tip  12 , a “pre-calibrated” instrument consisting of the tip  12  and the handle  20  is so to speak provided, which can immediately be positionally detected by the navigation system and used for example for acquiring landmarks on a patient. During such acquisition, the pressure on the tip can for example be monitored using the sensor  23 . If a landmark is acquired on the patient&#39;s skin, i.e. if it is to be positionally detected by the pointer tip, only a small pressure will be necessary using the pointer tip. If the pointer tip is pressed too firmly onto the landmark which is situated on the skin, the landmark (skin) could be shifted and the navigation result thus distorted. This pressure can however be monitored using the sensor  23 , such that corresponding incorrect acquisitions can be avoided. The pointer is then for example only pressed onto the landmark in such a way that a fluorescent strip display  25  (here as an embodiment) indicates a green value. 
     Energy can be supplied and/or a rechargeable battery can be recharged as shown for example in  FIGS. 2A and 2B . The instrument  20  has a rechargeable battery  27  which is welded in and tightly sealed such that the instrument can easily be sterilized. To this end, the handle  20  of the instrument is placed on the charging station  32 , and the circuit diagrams on the right show how the charging station comprises a primary circuit  36  comprising a primary coil which inductively operates the secondary circuit  34  and charges the rechargeable battery  27  via the secondary coil. Such an embodiment comprising an enclosed rechargeable battery  27  is very advantageous with respect to sterilization. 
     A different form of energy supply is however also conceivable, i.e. obtaining energy thermo-electrically as shown for example and schematically in  FIG. 3 . The thermo-electric element  40  is provided in order to operate an electrical load  42  and comprises a heat source  41  and a cold sink  43 . The heat source could for example be sterilization heat, while the cold sink is provided by the instrument which during sterilization is initially still cold. A so-called solid-state emitter  44  is connected to the heat source, and a thermo-electric semiconductor is situated between said solid-state emitter  44  and a solid-state collector  45  opposite. As long as there is a temperature gradient between the heat source  41  and the cold sink  43 , the electrical load  42  can be operated—for example, the rechargeable battery  27  can be charged. 
     Such an energy generator could for example be integrated into the instrument handle, wherein the heat source would be outside and the cold sink would be inside or in the middle, where the instrument remains cool the longest. 
     Computer program elements of the invention may be embodied in hardware and/or software (including firmware, resident software, micro-code, etc.). The computer program elements of the invention may take the form of a computer program product which may be embodied by a computer-usable or computer-readable storage medium comprising computer-usable or computer-readable program instructions, “code” or a “computer program” embodied in said medium for use by or in connection with the instruction executing system. Within the context of this application, a computer-usable or computer-readable medium may be any medium which can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction executing system, apparatus or device. The computer-usable or computer-readable medium may for example be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, device or medium of propagation, such as for example the Internet. The computer-usable or computer-readable medium could even for example be paper or another suitable medium on which the program is printed, since the program could be electronically captured, for example by optically scanning the paper or other suitable medium, and then compiled, interpreted or otherwise processed in a suitable manner. The computer program product and any software and/or hardware described here form the various means for performing the functions of the invention in the example embodiment(s). 
     Although the invention has been shown and described with respect to one or more particular preferred embodiments, it is clear that equivalent amendments or modifications will occur to the person skilled in the art when reading and interpreting the text and enclosed drawing(s) of this specification. In particular with regard to the various functions performed by the elements (components, assemblies, devices, compositions, etc.) described above, the terms used to describe such elements (including any reference to a “means”) are intended, unless expressly indicated otherwise, to correspond to any element which performs the specified function of the element described, i.e. which is functionally equivalent to it, even if it is not structurally equivalent to the disclosed structure which performs the function in the example embodiment(s) illustrated here. Moreover, while a particular feature of the invention may have been described above with respect to only one or some of the embodiments illustrated, such a feature may also be combined with one or more other features of the other embodiments, in any way such as may be desirable or advantageous for any given application of the invention.