WO2014140572A1

WO2014140572A1 - Instrument for preparing an osteotomy

Info

Publication number: WO2014140572A1
Application number: PCT/GB2014/050738
Authority: WO
Inventors: Neil Meredith
Original assignee: Neil Meredith
Priority date: 2013-03-12
Filing date: 2014-03-12
Publication date: 2014-09-18
Also published as: GB201304411D0; GB201404355D0; GB2513245A

Abstract

A hand-held surgical instrument comprises an orientation determining unit for determining the orientation of the instrument, and an indicator arranged in use to provide an indication of the orientation to a user. The orientation determining unit is preferably arranged to determine the orientation of the instrument with respect to at least one, preferably two and more preferably three axes. As an example, a drill (18) has a handle (18a) and a drill motor portion (18b), on which is mounted an orientation determining unit (20). The orientation determining unit comprises a sensor having a magnetometer, an accelerometer, a gyroscope or a combination thereof, in the form of a MEMS.

Description

INSTRUMENT FOR PREPARING AN OSTEOTOMY

The present invention relates to a surgical instrument, and to a method of orienting a surgical instrument, and is concerned particularly, although not exclusively, with a surgical instrument for use in preparing osteotomies, and to a method of orienting such an instrument.

Dental implants are medical devices commonly used to support crowns bridges or dentures in the replacement of missing teeth. They typically have a profile, part of which is generally screw-shaped, with a diameter in the range 3- 7mm, a length in the range 7-20mm and are commonly made of metal or ceramic, such as titanium or zirconia for example. When inserted into a prepared hole in bone the implant surface forms a direct and intimate contact with bone. This is commonly termed osseointegration . The implant, which may be termed an implant fixture, is normally surrounded by bone. The endosseous (i.e in-bone) part of the implant is connected to a crown, bridge or denture via an abutment. This is typically a collar, cylinder or spacer of varying height and diameter which crosses the gingivae, soft tissue or gum to provide a means of connection between an implant and the crown, bridge or denture.

Dental implants commonly have a threaded external form to aid stability and may have a cylindrical, tapered or step- like external geometry. There are also a wide range of sizes, diameters and lengths to ensure that there is a suitable component for all types of bone quality and quantity. Dental implants are inserted into a pre-prepared hole in the bone termed an osteotomy. The osteotomy is typically prepared in stages using a series of drills progressively increasing in size and more closely fitting the external form of the implant. This serial preparation is carried out to control the removal of the amount of bone and to prevent overheating which can lead to bone death. It also enables the clinician to alter the angulation, orientation and depth of the osteotomy during the preparation. Implants may be placed singly to replace a single tooth or multiple implants may be used to support a bridge or denture. The accuracy of the orientation and depth of the osteotomy in all dimensions and directions is critical to the successful restoration of the bridge, crown or denture. The angulation of the implant and its positioning should be such that the implant is placed so that its long axis is parallel to that of any adjacent tooth roots and perpendicular to the occlusal plane (an arbitrarily derived or virtual flat plane formed by connecting the tips of all the tooth cusps with a flat surface) . The geometry of tooth surface and directions is termed "mesial" - when it is towards the midline (front), "distal" - when towards the back of the mouth, "buccal" or "labial" - outwards towards the lips, and "palatal" or "lingual" - towards the tongue or palate.

The implant should be placed in a mid labiopalatal and mesiodistal position in relation to the crown or tooth it is replacing. This ensures an optimal direction for placement of the abutment and crown. Prostheses, crowns, bridges or dentures are commonly screwed onto the abutment and implant or cemented onto the abutment that is screwed on to the implant.

Figure 1 shows schematically a lower jawbone 10 with a number of implants 12 embedded therein. The implants each have an endosseous part 12a and an abutment post 12b on to which, in the example shown, is secured a bridge 14.

Mis-angulation of the direction of the implant at the time of placement can result in a very poor position with the screw access channel emerging through the front of the tooth which is a common occurrence.

In addition to optimising the position and orientation of a single implant during placement it is also essential to ensure that, when more than one implant is placed, each implant is as near parallel to the others as possible. If multiple implants diverge or converge by more than a few degrees, this can make the design, fabrication and placement of the abutments and restorations extremely difficult. Implant system components are designed to be able to be used within a specific range of angulations (typically <+/- 20^°) . If implants are angulated beyond this then it may not be possible to make a prosthesis that can be fitted.

Figure 2 shows schematically a jawbone 10 with a plurality of implants 12 that are misaligned in a number of axes. The misalignment has been exaggerated in the example.

There are currently three methods used to control the orientation of the osteotomy and implant direction: freehand, using a stent or guide or using a paralleling device . Most commonly the orientation and placement location for a dental implant osteotomy is carried out using the skill and experience of the surgeon who will assess visual and radiographic landmarks and then manually control the orientation of a motorised hand-piece holding the drills and implant to optimize placement angulation, depth and position. He may use small pins called ^direction indicators' or flags to give him visual feedback. Figure 3 is intended schematically to represent the visual assessment method.

The second most common method for aiding implant placement is the use of a stent /surgical guide. This can range in sophistication and complexity and typically it may be an acrylic guide made from a model of the patient's mouth. The guide is indexed and oriented by remaining teeth or by the patient's tissues and typically has one or more holes to indicate the ideal sites for implant placement.

In its simple form it provides no direct contact or guidance for the drills or implant. Complex stents may be designed in software from radiographic CT data that is used to plan the ideal implant location and then produce a CAD- CAM plastic stent. Such stents commonly have metal tubes to set precisely the orientation and depth of the implant placements . Figure 3 illustrates schematically a third approach, which uses paralleling, pantograph-like devices. One such device is shown at 16. These have articulating arms 16a to provide a guide for the drilling instrument 18. The arms can be reused. They are not patient specific and make use of flags and direction indicators rigidly linked via hinged arms to try to ensure that osteotomies remain parallel. Such devices have proved cumbersome in use and are not particularly popular. Accordingly, there is a need for a method or device capable of assisting or guiding a clinician in the preparation of single/multiple osteotomies and implant placements with a repeatable and reproducible accuracy to within a specified tolerance of a few millimetres or degrees. The problem is more critical in the placement of multiple implants where the geometrical interrelationship of the different implants needs to be highly accurate and, depending on the implant system, having a deviation no greater than +/- 20^°. Single implant placement is less critical as the guidelines and references are most commonly taken from the adjacent anatomy i.e. teeth.

Embodiments of the invention aim to address at least partly the aforementioned problems.

The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto.

According to one aspect of the present invention, there is provided a hand-held surgical instrument comprising an orientation determining unit for determining the orientation of the instrument, and an indicator arranged in use to provide an indication of the orientation to a user. The orientation determining unit is preferably arranged to determine the orientation of the instrument with respect to at least one, preferably two and more preferably three axes .

The orientation determining unit may comprise at least one magnetometer, and more preferably a multi-axis magnetometer . Preferably the orientation determining unit comprises at least one accelerometer, and more preferably a multi-axis accelerometer .

The orientation determining unit may comprise at least one gyroscope .

In a preferred arrangement, the orientation determining unit comprises at least one micro-electromechanical system (MEMS) .

The instrument may be arranged to provide real-time feedback to a user as to the orientation of the instrument.

The indicator may comprise visual indication means, which may comprise an electronic display.

Alternatively, or in addition, the indicator may comprise audio indication means. Alternatively, or in addition, the indicator may comprise haptic indication means. Alternatively, or in addition, the instrument may comprise feedback means arranged in use to control the speed or operation of the instrument.

Preferably the instrument comprises a memory, which may be an electronic storage means.

The memory may be arranged in use to store data, which may comprise orientation data for at least one orientation of the instrument.

The instrument may be arranged in use to compare data of one orientation, which may comprise a present orientation, with data of another orientation, which may comprise data of a previously stored orientation.

In a preferred arrangement the instrument comprises an electronic processor, such as a microprocessor.

The orientation determining unit may be arranged in use to determine the orientation of the instrument with respect to at least one reference, which reference may be the earth' s magnetic field.

Preferably the orientation unit comprises at least one sensor .

The orientation determining unit may be integral with the instrument .

Alternatively, the orientation determining unit may be remote from the instrument. The orientation determining unit may be attached to, or mounted on, another device comprising one of a group including, but not limited to: another surgical instrument, a motor, a hand piece and a probe .

The display may be integral with the instrument. Alternatively the display may be remote from the instrument and may be connected to the instrument wirelessly or by a wired connection.

The electronic processing means may be linked by wire or may be connected wirelessly with one or more of the indicator, the orientation determining unit the sensor and the memory.

Preferably the instrument comprises an instrument for preparing an osteotomy. The instrument may comprise an instrument for preparing an osteotomy for use in a dental or orthopaedic implant procedure.

The invention also includes a method of orientating a handheld surgical instrument, the method comprising holding the instrument so that an orientation determining unit of the instrument can determine its orientation, noting an indication of the orientation and moving the instrument to a preferred orientation in accordance with indicated orientation data.

The method may include storing orientation data of a first orientation and moving the instrument until an indicator indicates that a second orientation of the instrument has a predetermined relationship with the first orientation. The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent.

A preferred embodiment of the present invention will now be described. By way of example only, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 shows schematically a jawbone with a number of dental implants therein;

Figure 2 shows a jawbone with implants that are misaligned;

Figure 3 illustrates schematically a previously considered visual technique for aligning implants;

Figure 4 shows schematically a previously considered apparatus for aligning implants;

Figure 5 shows schematically an implant relative to three perpendicular axes; Figure 6 shows schematically a hand instrument relative to three perpendicular axes;

Figure 7 shows a hand-held surgical instrument according to an embodiment of the present invention;

Figure 8 shows the instrument of Figure 7 in alternative configurations; and Figure 9 shows schematically the instrument of Figures 7 and 8. The embodiment described below seeks to provide a device that can record the spatial orientation of an instrument with reference to three axes, as 9 degrees of freedom, and can provide audible, visual or tactile/haptic feedback to the operator of the instrument concerning the degree of deviation from that precisely recorded spatial orientation. This will enable a clinician to determine the accuracy of his preparation of the osteotomy in order to ensure accurate implant orientation. A feedback mechanism, including an automatic power cutout for the drill in the case of an out-of-orientation drill, may be provided.

Figure 5 shows schematically the orientation of an implant 12 with respect to three perpendicular axes x, y and z.

Figure 6 shows schematically a dental drill 18 in relation to the three axes x, y and z. Figure 7 shows the drill 18 having a handle 18a and a drill motor portion 18b, on which is mounted an orientation determining unit 20. The orientation determining unit comprises a sensor having a magnetometer, an accelerometer, a gyroscope or a combination thereof, in the form of a MEMS (not shown) , as will be described below.

As shown in Figure 8, the orientation determining unit 20 may be positioned in any of a number of locations with respect to the drill 18, so long as at least a sensor is fixed to move with the drill. Some possible locations for the orientation determining unit are indicated by the numeral 20.

Figure 9 shows schematically the main components of the orientation determining unit 20. They include an electronic processor 22, a tri-axis sensor 24, which may comprise a magnetometer, an accelerometer, a gyroscope or any combination thereof, an electronic display 26, an audio output 28, a haptic feedback device 30 arranged to provide a tactile response to the user via the handle 18a, and a memory unit 32.

The device is relatively simple to design and makes use of the many commercially available integrated circuit magnetometers, gyroscopes and accelerometers . Some devices incorporate a combination of sensors and a motion processor on a single chip (e.g. Invensens Inc MPU -6000). The sensor 24 senses the position and orientation of the device relative to the earth' s magnetic field, and/or the accelerometers movement, or to a local reference source. This data is processed digitally typically to give I²C or SPI data that is then fed into a motion processing unit (not shown) or directly into the processor 22. The processor 22 processes the digital data resolving the X,Y and Z orientations and relevant movement data. The processor also drives the outputs 26, 28 and 30 to provide feedback to the operator. The sensor 24 can be placed on or inside the surgical instrument and can be supplied with power and data lines from a remote control unit (not shown) .

There follows a description of one example of a method of using the instrument: The operator will hold a surgical instrument attached to the orientation measuring unit. The surgical instrument will usually have a drill for preparing a round hole, or osteotomy in bone. If placing multiple implants the operator will orientate the drill so as to obtain the best clinical position for the implant and drill the osteotomy. When the drill is in the osteotomy the orientation measuring unit can record the orientation of the drill and osteotomy as a 3 dimensional coordinate Χ,Υ,Ζ. The operator then goes on to drill the further osteotomies and the orientation measuring unit provides audible, visual, haptic or feedback control to the operator to enable him to ensure that the subseguent osteotomies are within a preset tolerance of the first. If preparing just a single osteotomy the operator can establish a reference by aligning the instrument/drill to the local anatomy, bone contours and adjacent teeth and then using this reference to optimize the placement of the osteotomy. During drilling, if the clinician inadvertently changes the orientation of the instrument beyond a predetermined extent relative to the previously stored orientation, the drill may automatically switch to a power - off state to prevent further drilling. The orientation determining unit described above provides a number of benefits to a clinician. Firstly, it will measure the orientation in space as Χ,Υ,Ζ co-ordinates of a surgical instrument, such as a dental implant drill in a dental hand-piece with motor. The orientation can be displayed visually as a digital numerical, or graphical, indication. Data of a specific orientation, which may be a previously determined orientation, can be stored in the memory for comparison with a later adopted orientation, such as for example in the preparation of a series of osteotomies.

Numerical or graphical feedback can be provided on the electronic display to indicate in real time the difference between current orientation values and previously recorded ones. Alternatively, or in addition, this feedback can be provided audibly, for example represented by volume or pitch of an audible signal, or else haptically.

In addition, the instrument may be arranged to go to a power off state, or a power on state, in dependence upon the determined orientation. The speed of operation of the motor may also be controlled in accordance with the determined orientation. Using the device, an operator is provided with navigation assistance to enable a surgical instrument to be oriented the same as a previously recorded orientation or within a specified range, such as ± 2° or + 2°<=± 10°, for example.

Another possible use of the instrument is to assist when a dentist cuts down a tooth to make a crown - a technique known as a crown preparation. When a tooth is prepared enamel, dentine and restorative materials are removed over the tooth surface to allow and adequate thickness of the material being used for the crown to achieve sufficient strength and aesthetics. Such a preparation cannot be undercut as the crown will not fit and there will be a gap between the crown and tooth preparation. The optimal taper of a tooth preparation is greater than 0° but less than approximately 10-15°. When cutting a tooth preparation the angle of the preparation is done by eye, sometimes using a tapered burr to help. An undercut preparation is a common problem that must be corrected by the dentist before a crown can be made .

The navigational abilities of the device described can be employed at the start of a tooth preparation to set a reference point to which further preparatory work can relate.

Whereas the above-described examples refer to an osteotomy, the invention could also be used in other procedures.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

1 . A hand-held surgical instrument comprising an orientation determining unit for determining the orientation of the instrument, and an indicator arranged in use to provide an indication of the orientation to a user.

An instrument according to Claim 1, wherein the orientation determining unit is arranged to determine the orientation of the instrument with respect to at least one axis.

3. An instrument according to Claim 1 or 2, wherein the orientation determining unit comprises at least one magnetometer .

4. An instrument according to any of Claims 1 to 3, wherein the orientation determining unit comprises at least one accelerometer .

An instrument according to any of Claims 1 to 4, wherein the orientation determining unit comprises at least one gyroscope.

An instrument according to any of Claims 1 to 5, wherein the orientation determining unit comprises at least one micro-electromechanical system (MEMS) .

An instrument according to any of Claims 1 to 6 wherein the instrument is arranged to provide real time feedback to a user as to the orientation of the instrument .

An instrument according to any of Claims 1 to 7, wherein the indicator comprises visual indication means

9. An instrument according to any of Claims 1 to 8, wherein the indicator comprises audio indication means .

An instrument according to any of Claims 1 to 9, wherein the indicator comprises haptic indication means

An instrument according to any of Claims 1 to 10, wherein the instrument comprises feedback means arranged in use to control the speed or operation of the instrument.

12. An instrument according to any of Claims 1 to 11, wherein the instrument comprises a memory.

13. An instrument according to Claim 12, wherein the memory is arranged in use to store data, comprising orientation data for at least one orientation of the instrument .

14. An instrument according to Claim 12 or 13, wherein the instrument is arranged in use to compare data of one orientation with data of another orientation. 15, An instrument according to any of Claims 1 to 14, wherein the instrument comprises an electronic processor, such as a microprocessor. 16. An instrument according to any of Claims 1 to 15, wherein the orientation determining unit is arranged in use to determine the orientation of the instrument with respect to at least one reference.

An instrument according to any of Claims 1 to 16, wherein the orientation unit comprises at least one sensor .

18. An instrument according to any of Claims 1 to 17, wherein the orientation determining unit is integral with the instrument.

An instrument according to any of Claims 1 to 17, wherein the orientation determining unit is remote from the instrument .

An instrument according to Claim 19, wherein the orientation determining unit is attached to, or mounted on, another device distinct from the instrument .

An instrument according to Claim 20, wherein the other device comprises one of a group including: another surgical instrument, a motor, a hand piece and a probe . An instrument according to any of Claims 1 to wherein the display is integral with the instrument

An instrument according to any of Claims 1 to 22 comprising an instrument for preparing an osteotomy.

A method of orientating a hand-held surgical instrument, the method comprising holding the instrument so that an orientation determining unit of the instrument can determine its orientation, noting an indication of the orientation and moving the instrument to a preferred orientation in accordance with indicated orientation data.

A method according to Claim 24, wherein the method includes storing orientation data of a first orientation and moving the instrument until an indicator indicates that a second orientation of the instrument has a predetermined relationship with the first orientation.