Surgical instruments

Abstract

The invention discloses a surgical instrument (25), in particular, a surgical cutting or drilling instrument, the surgical instrument (25) comprising: a drive unit; a cutting tool or drill bit (5), the cutting tool or drill bit being engageable with the drive unit; a measuring device (1), the measuring device being configured to measure a distance [x(t)] covered by the cutting tool or drill bit (5) along a cutting or drilling path relative to time and relative to a reference position; a processing unit and a digital data storage device, wherein reference data are stored in the digital data storage device, the reference data comprising at least one data set, the at least one data set specifying a reference pattern G within a time window (11) within a transition range. Ref and defining a reference point (21') of the transition, wherein the time window (11) comprises a first time period before the reference point (21') of the transition and a second time period after the reference point (21') of the transition, and wherein the processing unit (14) is suitably programmed to compare the recorded pattern G with at least one reference pattern G Ref A comparison is made and the position of the transition (21) is found in the recorded graph G.

Description

Background Art 1. Technical Field

[0002] The invention relates to a surgical instrument according to the preamble of independent claim 1 and to a method for estimating the length of a bone screw from drilling characteristics according to the preamble of claim 55 .

[0003] Based on clinical observations, one problem in orthopedic and trauma surgery is determining the required screw length for, e.g., bicortical screw placement, before inserting the screw into a bone segment. Current mechanical depth gauges are rather inaccurate, unreliable, and difficult to operate, resulting in:

[0004] - Prolonged operation time;

[0005] - Insertion of screws that are too long, resulting in soft tissue irritation, pain, and reoperation;

[0006] - Insertion of screws that are too short, resulting in bone failure and reoperation;

[0007] -Screws need to be replaced, resulting in the scrapping of screws and increased hardware costs.

[0008] 2. Description of Related Technology

[0009] From US 2016 / 036756 MCGINGLEY et al., a surgical electric drill including an integrated measurement system is known, which is used to determine when the leading edge of a surgical tool reaches a second medium from a first medium. This known electric drill includes: a displacement sensor, which outputs a displacement signal, which represents the displacement of the leading edge of the tool relative to a reference point; a computing module, which is in operative communication with the displacement sensor and is used to generate a velocity signal and an acceleration signal based on the displacement signal; and a processing module, which is in operative communication with the computing module, and is configured to determine the incidence of the leading edge of the tool reaching the second medium from the first medium only based on the displacement signal, the velocity signal and the acceleration signal. The disadvantage of this known surgical electric drill is that the reference data for determining the transition of the leading edge of the tool from the first medium to the second medium only include the calibration thresholds of the displacement, velocity and acceleration of the tool at the moment when the tool transitions from the first medium to the second medium. Summary of the invention

[0010] The object of the present invention is to provide a surgical cutting or drilling device having a device for determining the transition of a cutting tool or drill bit from a first medium having a first density to a second medium having a different second density during a cutting or drilling process, the cutting or drilling process comprising a numerical procedure with significantly higher robustness using only displacement characteristics.

[0011] The invention solves the posed problem with a surgical instrument comprising the features of claim 1 and a method for estimating the length of a bone screw from drilling characteristics comprising the features of claim 55 .

[0012] The advantages of this surgical instrument can basically be seen from the following:

[0013] - determining that the transition of the cutting tool or drill bit is based on a plurality of reference patterns of the distance covered by the cutting tool or drill bit, wherein each reference pattern extends within a time window comprising a first time period before a reference point of the transition and a second time period after the reference point of the transition, so that in the case of a surgical drilling device the importance of detecting the point at which the drill bit leaves the bone cortex can be increased;

[0014] - the processing unit can report two values ​​of the position of the transition of the drill bit from the first medium to the second medium, which occur at the position where the cutting tip of the drill bit leaves the proximal cortex, respectively the distal cortex, of the bone. The surgeon can then decide whether to apply a monocortical or a bicortical bone screw; and

[0015] Due to the use of a single position sensor, the measuring unit has a simple construction and can therefore be constructed as a stand-alone unit which can be temporarily attached to a standard surgical cutting or drilling device.

[0016] Further advantageous embodiments of the present invention can be reviewed as follows:

[0017] In a particular embodiment, the digital data storage device further stores a predetermined threshold value of the similarity measure, and wherein the processing unit is programmed to trigger a transition event if the similarity threshold value is reached and to report the position x of the transition.

[0018] In another embodiment, the digital data storage device is configured as a buffer to keep the actual time window of the current graph G of the distance [x(t)] at least as large as the reference graph G Ref The window is the same size.

[0019] In another embodiment, a plurality of reference patterns G Ref stored in a digital data storage device, representing various drilling or cutting characteristics, and the processing unit is suitably programmed to repeat the following steps: with the aid of all stored reference patterns G Ref The similarity metric is used to quantify the similarity between the recorded graph G or at least a part of the recorded graph G and the reference graph G. Ref The consistency between graph G and all reference graphs G Ref The overall best fit between , thereby identifying the position x of the transition in the recorded graph G.

[0020] In another embodiment, each reference pattern GRef At least 10 values, preferably at least 20 values, of the distance [x(t)] covered by the cutting tool or drill are specified, these values ​​being subsequent values ​​relative to the time within a second time period after the reference point of the transition.

[0021] In yet another embodiment, each reference pattern G Ref At least 30 values, preferably at least 40 values, of the distance [x(t)] covered by the cutting tool or drill are specified, these values ​​being subsequent values ​​relative to the time within the first time period before the reference point of the transition.

[0022] The use of multiple values ​​of the distance [x(t)] covered by the cutting tool or drill bit before and after the reference point of the transition allows the algorithm's robustness to be improved, since the detection of the transition of the cutting tool or drill bit is not limited to the features only at the transition point, but is performed by characterizing the movement of the cutting tool or drill bit before and after the transition point. In this way, false positive events can be filtered and eliminated.

[0023] In another embodiment, in each reference pattern G Ref The second time period after the reference point of the transition amounts to at least 0.1 seconds, preferably at least 0.3 seconds.

[0024] In another embodiment, in each reference pattern G Ref The first time period before the reference point of the transition amounts to at least 0.3 seconds, preferably at least 0.4 seconds.

[0025] In another embodiment, the reference data will refer to the graph G Ref Designated as having a monotonically increasing distance [x(t)] covered by the cutting tool or drill in a first time period before reaching a reference point of the transition. When the drill has left the bone and has become clearly stationary after leaving, the user performs an unintended further movement and advances the drill further. Using one of the devices known from the prior art, all criteria for the transition are met, so that an erroneous value of the transition point is detected and a bone screw that is clearly too long is selected and positioned in the bone. Due to the need for a constant advancement speed v>0 of the cutting tool or drill, such events can be filtered and eliminated.

[0026] In yet another embodiment, the surgical instrument further comprises a surgical cutting or drilling device.

[0027] In another embodiment, the surgical drilling device is a surgical electric drill, wherein the drive unit comprises a motor and a spindle, the spindle being drivable by the motor and having a longitudinal axis, such that the reference point can be defined by the surface of the implant or the bone. A program executed by the processing unit allows estimating the bone screw length based solely on the drilling characteristics.

[0028] In another embodiment, the processing unit is one of a computer, tablet, smart phone, smart watch, or smart glasses with a monitor.

[0029] In another embodiment, the processing unit comprises a wireless communication device, preferably a Bluetooth module. The derived information (i.e. the measured position x of the cutting head of the drill bit with respect to time and the calculated transition point) can be wirelessly transmitted to an external device, such as a computer with a monitor, a tablet computer, a smart phone, a smart watch or smart glasses.

[0030] In yet another embodiment, the surgical instrument further includes a housing.

[0031] In another embodiment, the measuring device comprises attachment means, preferably an adapter releasably attachable to the housing of a surgical drill. This configuration allows the advantage that the measuring device can be configured as a separate unit that can be temporarily attached to a standard surgical drill.

[0032] In another embodiment, the measuring device comprises a clamp to releasably attach the measuring device to the housing.

[0033] In another embodiment, the adapter is configured as a frame attachable to the housing, preferably as an annular frame fixed to the housing by means of a press fit or via a clamping ring.

[0034] In yet another embodiment, the measuring device is integral with the housing.

[0035] In another embodiment, the best fitting reference pattern G in the selection pattern G is used Ref The similarity measure for finding the position x of the transition in the recorded graph G is a pattern recognition method, preferably a shape context descriptor.

[0036] In another embodiment, the reference data specifies a statistical representation of a plurality of expected recorded patterns G over a range of transitions of a cutting tool or drill bit from a first medium having a first density to a second medium having a different second density during a cutting or drilling process.

[0037] In another embodiment, the reference data is continuously modified during use of the cutting or drilling equipment.

[0038] In another embodiment, the modification of the reference data is performed by a machine learning algorithm, preferably involving the use of a neural network.

[0039] In another embodiment, the measuring device comprises a non-contact displacement sensor.

[0040] Preferably, the contactless displacement sensor is a triangulation distance sensor and comprises a light transmitter and a corresponding receiver.

[0041] In another embodiment, the non-contact displacement sensor includes an LED light emitter.

[0042] In another embodiment, the measuring device comprises a laser device comprising a laser module and one or more electronic light sensors, preferably a charge coupled device (CCD), to perform laser triangulation for displacement assessment. The construction of the measuring device using a laser device for displacement assessment by means of triangulation allows a simple construction of the measuring device without a mechanical arm between the displaceable member and the sensor. Therefore, the surgeon's working area is not occupied and the field of vision is not blocked. In contrast to mechanical contact measurement, non-contact distance measurement reduces the risk of contamination of the patient and does not affect the drilling process. In addition, compared to 6.4 cm of known devices, a significantly larger measuring range is achieved, for example 15 cm to 30 cm, so that a wide variety of drill bits and drill sleeves with different lengths can be used.

[0043] In yet another embodiment, the non-contact displacement sensor is based on radar, preferably a millimeter wave radar sensor.

[0044] In another embodiment, the non-contact displacement sensor is an ultrasonic distance sensor.

[0045] In another embodiment, a non-contact displacement sensor includes a reflector that is slidable along a drill bit and configured to abut an implant, bone, or instrument.

[0046] In another embodiment, the processing unit further comprises a display or a speaker. The derived information can be provided on a display or a speaker mounted locally to the drill, wherein the main output parameters are: the current position x of the cutting head of the drill, which is consistent with the measured distance x covered by the housing in the direction of the longitudinal axis and relative to the surface of the implant, instrument or bone; the current speed of the drill moving forward; and the position of the cutting head of the drill when the drill transitions from the first medium to the second medium, from which the appropriate implant length can be derived.

[0047] In another embodiment, the measuring device comprises a housing for enclosing the processing unit.

[0048] Preferably, the housing enclosing the processing unit is sterilizable.

[0049] In another embodiment, the measuring device includes: a first member, which is in a fixed position relative to the housing; and a longitudinal second member, which is capable of being displaced relative to the first member substantially in the direction of the longitudinal axis of the spindle, and the longitudinal second member includes a front end suitable for adjoining the surface of the bone or implant.

[0050] In yet another embodiment, the displaceable second member comprises a drill sleeve extending in the direction of the longitudinal axis to a front end of the second member.

[0051] In another embodiment, the first component of the measuring device and preferably the processing unit can be inserted into a hollow space arranged in the housing of the surgical drill.

[0052] In yet another embodiment, the first component and preferably the processing unit are part of an electronic module which also includes a power supply and / or a motor for driving the surgical drill, and wherein the power supply is configured to supply electrical energy to the first component and preferably the processing unit and the motor.

[0053] In another embodiment, the hollow space is disposed in the handle of the housing and is configured to receive the electronic module.

[0054] In another embodiment, the housing includes a top portion including a sterilizable window for covering the display.

[0055] Preferably, the top portion is integral with the outer casing and forms a housing for the display.

[0056] In another embodiment, the housing includes at least one sterile window to provide a window for signals transmitted by the non-contact displacement sensor and reflected signals that can be received by the non-contact displacement sensor.

[0057] In another embodiment, the sterile window is configured as a recessed window. During sterilization and operation, critical transparent surfaces are protected from mechanical impact and scratching to avoid damage to the light beam inlet and outlet.

[0058] In yet another embodiment, the housing is attachable to the casing by means of an adapter and includes a cavity configured to receive the electronic module.

[0059] In another embodiment, the housing includes a cover disposed at a rear end of the housing and including a sterilizable rear window for covering the display.

[0060] In another embodiment, the housing includes at least one sterile front window to provide a window for signals transmitted by the non-contact displacement sensor and reflected signals that can be received by the non-contact displacement sensor.

[0061] In another embodiment, the displaceable second member includes a clamping portion for attachment to a cylindrical structure having a variable diameter.

[0062] In another embodiment, the clamping portion of the displaceable second member is configured to provide a friction fit with the drill bit. In this way, the advantage can be achieved that the reflector can slide along the drill bit, but will not move due to gravity or small impacts. In this way, the reflector is pushed against the surface of the instrument or implant without the need to precisely match the geometry of the instrument or implant.

[0063] In another embodiment, the measuring device is positioned relative to the housing such that the light beam emitted by the contactless displacement sensor is oriented at an offset angle relative to the longitudinal axis of the spindle.This configuration allows the advantage that the diameter of the displaceable second member can be reduced.

[0064] In another embodiment, the first member of the measuring device is positioned eccentrically relative to the longitudinal axis of the spindle. Thus, the advantage can be achieved that the (transmitted and reflected) laser beam is not blocked by the drill head. The operator's view is less obstructed.

[0065] In another embodiment, the measuring device comprises at least one accelerometer. In this way, the device can be operated by gestures instead of buttons. Example: Taring is only possible when pointing downwards in a vertical orientation (within limits). Switching back to taring mode is done by orienting the drill to point vertically upwards. Sleep mode and wake-up by device movement is used to save energy.

[0066] In another embodiment, the measuring device further comprises a gyroscope and / or a magnetometer.This configuration allows the advantage that the absolute orientation of the drill can be tracked to control the drilling direction.

[0067] In another embodiment, the surgical instrument further comprises a calibration device.

[0068] In another embodiment, the processing unit is programmed for real-time calculations.

[0069] In another embodiment, the processing unit comprises a data storage to store data related to the length of the bone screw, preferably including the safety margin, the screw head length, the end section length and the screw length increment.

[0070] In another embodiment, the processing unit is suitably programmed to control the rotational speed of the spindle of the surgical drill or to stop the spindle when the transition point is detected.

[0071] In another aspect of the present invention, a method for estimating the length of a bone screw from drilling characteristics using a surgical drill according to the present invention is provided, the method comprising the following steps: A) advancing the surgical drill coaxially relative to the longitudinal axis of the spindle to drill a hole in the bone, and recording the position (x) of the cutting head of the drill relative to the surface of the bone or implant in the drilling direction relative to time; B) determining the distance [x(t)] covered by the drill bit relative to the surface of the bone or implant when the cutting head of the drill bit leaves the cortex of the bone by using stored reference data to find the position of the transition of the drill bit from the first medium to the second medium in the recorded graph G; and C) selecting a bone screw having a length corresponding to the distance [x(t)] covered by the drill bit determined in step B) while taking into account a predetermined safety margin.

[0072] In another embodiment of the method, the following steps are performed before step A):

[0073] positioning the surgical drill relative to the bone so that the front end of the displaceable second member and the cutting tip of the drill abut the surface of the bone or object; and

[0074] If necessary, adding an offset value stored in the data storage device to the relative position; and

[0075] The relative position is stored as a starting point (x=0) for measuring the position (x) of the cutting tip of the drill relative to the bone surface in the drilling direction with respect to time.

[0076] In this case, the second component comprises a drill sleeve which extends in the direction of the longitudinal axis to a front end of the second component.

[0077] In another embodiment of the method, the following steps are performed before step A):

[0078] positioning the surgical drill relative to the bone so that the front end of the displaceable second member abuts against a drill sleeve inserted into soft tissue covering the bone to be treated; and

[0079] adjusting a cutting bit of a drill bit secured in an engagement device of a surgical drill relative to the displaceable second member so that the cutting bit of the drill bit abuts a surface of the bone; and

[0080] If necessary, adding an offset value stored in the data storage device to the relative position; and

[0081] The relative position is stored as a starting point (x=0) for measuring the position (x) of the cutting tip of the drill relative to the surface of the bone or implant in the drilling direction with respect to time.

[0082] In this case, a separate drill bushing can be used.

[0083] In another embodiment of the method, the following steps are performed before step A):

[0084] positioning a drill bit secured in the engagement device relative to the displaceable second member by using a calibration device so that a front end of the second member contacts a surface of the calibration device and a cutting tip of the drill bit abuts a stopper protruding from a surface of the calibration device;

[0085] storing the relative position as a starting point (x=0) for measuring the position (x) of the cutting tip of the drill relative to the surface of the bone or implant in the drilling direction with respect to time; and

[0086] The surgical drill is positioned relative to the implant such that the leading end of the displaceable second member abuts a surface of the implant.

[0087] Preferably, the first medium penetrated by the cutting tool or drill bit of the surgical instrument is cortical bone or trabecular bone.

[0088] Preferably, the surgical drill according to the present invention is used for estimating bone screw length. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Several embodiments of the present invention will be described below by way of example and with reference to the accompanying drawings, in which:

[0090] Figure 1 shows a perspective view of an embodiment of an apparatus according to the invention;

[0091] Figure 2 A schematic diagram showing a reference pattern specified by reference data and a process performed by a processing unit;

[0092] Figure 3 shows a schematic diagram of a process performed by a processing unit in the case of drilling a hole through a bone;

[0093] Figure 4 shows a perspective view of another embodiment of the device according to the present invention;

[0094] Figure 5 shows a perspective view of another embodiment of the device according to the present invention;

[0095] Figure 6 Shows Figure 5 An exploded front view of an embodiment of the invention;

[0096] Figure 7 shows a perspective view of a calibration device for use with the device according to the invention;

[0097] Figure 8 shows Figure 7A perspective view of an embodiment of a calibration device together with a drill bit and a displaceable second member of the device according to the invention;

[0098] Fig. 9 A schematic cross-sectional view showing an implant positioned on a bone together with a drill bit and an embodiment of a displaceable member of an apparatus according to the invention at the starting point of the drilling process;

[0099] Fig.10 shows a schematic cross-sectional view of an implant positioned on a bone together with a drill bit and an embodiment of a displaceable member of an apparatus according to the invention at the point where the drill bit abuts on the surface of the bone;

[0100] Figures 11a to 11e Perspective views showing different embodiments of the displaceable second member of the device according to the invention;

[0101] Fig.12 shows a perspective view of another embodiment of the device according to the present invention;

[0102] Fig.13 Shown according to Fig.12 A perspective view of a first component of a measuring device of this embodiment of the device;

[0103] Fig.14 Shown according to Fig.12 Another perspective view of the first component of the measuring device of this embodiment of the device;

[0104] Fig.15 Shown from the Fig.12 A perspective view of the embodiment of the device viewed from the front;

[0105] Fig.16 shows a perspective view of a displaceable second member of a measuring device according to another embodiment of the device according to the invention; and

[0106] Fig.17 A perspective view of an assembly is shown, the assembly comprising a Fig.16 A displaceable second member of the measuring device, together with the drill sleeve and the calibration device. DETAILED DESCRIPTION

[0107] The following description of different embodiments of the surgical instrument 25 relates by way of example but not limitation to a surgical drilling device configured as a surgical drill 2, wherein:

[0108] - the drive unit comprises a motor and a spindle 13 which can be driven by the motor and has a longitudinal axis 7 in the direction of which the drilling path extends;

[0109] - the engagement means are configured to allow the chuck 6 of the drill bit 5 to be clamped; and wherein

[0110] - The reference position is defined by the surface of the implant 26 or of the bone.

[0111] The measuring device 1 may comprise a signal conditioner to convert the analogue signal generated by the sensor into a digitised signal. Furthermore, the processing unit 14 may be provided with a timer or a clock in order to record the relative position x with respect to time.

[0112] definition

[0113] The following definitions of currently used terms and expressions describe their exact meanings as used throughout this specification:

[0114] Position x of the cutting head of the drill bit relative to the surface of the bone or implant: During the drilling process, the distance x covered by the housing 12 in the direction of the longitudinal axis 7 of the spindle 13 and relative to the surface of the bone or implant 26 is related to the position x of the cutting head 9 of the drill bit 5 relative to the surface of the bone or implant 26 in the drilling direction, because the drill bit 5 is firmly fixed in the chuck 6 of the surgical drill 2 and is positioned at the beginning of the drilling process, as described in detail below.

[0115] Depending on the object (e.g. bone) in which the hole is drilled, the cutting tool or drill bit 5 may have more than one transition point 21 from the first medium to the second medium, such as a first transition from cortical bone to cancellous bone (spongy bone) and a second transition from cortical bone to surrounding tissue. Ref The reference point of the transition is denoted by reference numeral 21'.

[0116] Figure 1 An embodiment of a surgical drill 2 according to the present invention is shown, wherein the surgical drill 2 basically comprises: a housing 12, in which a motor and a spindle 13 driven by the motor are housed; a measuring device 1, which is releasably attached or fixed to the housing 12; and an adapter 15, which is used to fix the measuring device 1 to the housing 12. The spindle 13 has a longitudinal axis 7 and includes a chuck 3 for clamping a drill bit 5 at the front end. The measuring device 1 includes a first member 3 and a longitudinal second member 4, which is in a fixed position relative to the housing 12 and can be displaced relative to the first member 3 parallel to or coaxial with the longitudinal axis 7 of the spindle 13 by way of example but not limitation. Alternatively, the measuring device 1 can be arranged at the housing 12 so that the second member 4 can be displaced at an angle relative to the longitudinal axis 7 of the spindle 13. Systematic errors (cosine errors) arising from this angle measurement can be easily compensated. The advantage of this configuration is that the reflector can be smaller, so that the measuring end can be arranged closer to the drill bit 5.

[0117] The displaceable second member 4 has a front end 10, wherein in use, the front end 10 of the displaceable second member 4 abuts against a bone surface or a surface of an implant 26 (e.g. a bone plate or a drill sleeve). The drill bit 5 can be clamped in a chuck 6 and provided with a cutting bit 9. Furthermore, the displaceable second member 4 can include a drill sleeve 23, which extends to the front end 10 of the second member 4 in the direction of the longitudinal axis 7.

[0118] The measuring device 1 comprises a laser device for linear displacement assessment. The laser device comprises: a laser module 18 having a laser light emitting device; a reflector 20 attached to a drill sleeve 23 forming a second member 4 capable of sliding along a drill bit 5; and at least one electronic light sensor 19, which is configured as a charge coupled device (CCD) by way of example but not limitation, to perform laser triangulation for linear displacement assessment.

[0119] In another alternative embodiment, linear displacement assessment may be performed through the use of an ultrasonic position sensor.

[0120] In order to integrate the determination of the screw length in the drilling procedure so as to eliminate the depth measurement step after drilling in the bone, the construction of the measuring device 1 is based on the fact that during drilling, an acceleration peak of the drill bit 5 occurs when the cutting tip 9 of the drill bit 5 leaves the bone cortex, as this is an unavoidable property of hand-held drilling. Therefore, the housing 12 of the surgical drill 2 is subjected to the same acceleration together with the first member 3 of the measuring device 1.

[0121] The surgical instrument 25 further comprises a processing unit 14 and a digital data storage device. The processing unit 14 is electronically connected directly or wirelessly to the measuring device 1 and is suitably programmed to record a graph G of the distance [x(t)] covered by the cutting tool or drill 5 during the cutting or drilling process relative to a reference position and relative to time. In the digital data storage device are stored reference data comprising one or more data sets, each data set specifying a reference graph G of the distance [x(t)] covered by the cutting tool or drill 5 during the cutting or drilling process relative to time and within a time window 11 within which the cutting tool or drill 5 transitions from a first medium having a first density to a second medium having a different second density. Ref .

[0122] like Figure 2 As shown, multiple reference graphics G Ref can be stored in a digital data storage device, representing various drilling or cutting characteristics. The processing unit 14 is suitably programmed to repeat the following steps: with the aid of all stored reference patterns G RefThe similarity metric is used to quantify the similarity between the recorded graph G or at least a part of the recorded graph G and the reference graph G. Ref The consistency between graph G and all reference graphs G Ref The overall best fit between , thereby identifying the position x of the transition 21 in the recorded graph G.

[0123] One or more reference graphics G Ref Each reference pattern in defines a reference point 21' of the transition of the cutting tool or drill 5 from the first medium to the second medium, wherein the time window 11 comprises a first time period before the reference point 21' of the transition and a second time period after the reference point 21' of the transition. The processing unit 14 is suitably programmed for comparing the recorded pattern G or at least a part of the recorded pattern G with at least one reference pattern G by means of a similarity measure. Ref Comparing to quantify the recorded pattern G or at least a portion of the recorded pattern G with at least one reference pattern G Ref The consistency between the two similarity measures is determined by comparing the two similarity measures, thereby finding the position x of the transition 21 in the recorded graph G. In the case where at least a portion of the recorded graph G is used for comparison, the at least a portion of the recorded graph G extends at least over a time period as specified by the time window 11. The processing unit 14 is programmed for real-time calculations. The digital data storage device also stores a predetermined threshold value for the similarity measure, and the processing unit 14 is programmed to trigger a transition event and report the position x of the transition 21 if the similarity threshold value is reached.

[0124] Figure 3 A schematic diagram of the process performed by the processing unit 14 in the case of drilling a hole through a bone is shown. The processing unit 14 can report two values ​​of the position of the transition 21 of the drill 5 from the first medium to the second medium, which occur at the position where the cutting tip 9 of the drill 9 leaves the proximal cortex [x(ta)], respectively the distal cortex [x(tb)] of the bone, so that the surgeon can then decide whether to apply a monocortical bone screw or a bicortical bone screw.

[0125] The digital data storage device is in particular configured as a buffer to keep the actual time window of the current graph G of the distance [x(t)] at least as large as the reference graph G Ref As an example but not limiting, each reference pattern G RefThe distance [x(t)] covered by the cutting tool or drill bit 5 is specified by about 30 values ​​of subsequent values ​​of the time in a first time period before the reference point 21' of the transition, and the distance [x(t)] covered by the cutting tool or drill bit 5 is specified by about 10 values ​​of subsequent values ​​of the time in a second time period after the reference point 21' of the transition. Exemplarily, the first time period before the reference point 21' of the transition amounts to about 0.3 seconds, and the second time period after the reference point 21' of the transition amounts to about 0.3 seconds. In addition, the reference data inherently requires that the cutting tool or drill bit 5 has a positive advancement speed v>0 in the first time period before reaching the reference point 21' of the transition. The best fitting reference graph G applied to the selection of the graph G Ref The similarity measure of the part to find the position x of the transition 21 in the recorded graph G can be a pattern recognition method, exemplarily but not limitingly a shape context descriptor. The reference data specifies a statistical representation of a plurality of expected recorded graphs G within the range of the transition of the cutting tool or drill 5 from a first medium with a first density to a second medium with a different second density during the cutting or drilling process. In addition, the reference data is continuously modified according to the use of the cutting or drilling equipment, wherein the modification of the reference data can be performed by a machine learning algorithm, preferably by involving the use of a neural network.

[0126] The measuring device 1 in particular measures and records the relative movement between the displaceable second member 4 and the first member 3 fixed relative to the housing 12. Since the drill 5 is firmly clamped in the chuck 6, the relative movement between the displaceable second member 4 and the first member 3 coincides with the relative movement of the cutting head 9 of the drill 5 relative to the front end 10 of the displaceable second member 4. Therefore, the measuring device 1 measures and records in real time the relative movement of the drill 5 in the drilling direction relative to the bone surface or relative to the implant surface on which the front end 10 of the displaceable second member 4 of the measuring device 1 abuts. The movement of the drill 5 relative to the displaceable second member 4 of the measuring device 1 is a one-dimensional translational movement, and the position x of the cutting head 9 of the drill 5 relative to the front end 10 of the displaceable second member 4 at any moment is given by the x coordinate of the cutting head 9 along the x axis 8, which in this case forms a reference system. At the beginning of the drilling procedure, for example when the cutting head 9 of the drill 5 is flush with the front end 10 of the displaceable second member 4 , the position x or x coordinate of the cutting head 9 is set to zero.

[0127] For this purpose, the position x or the x coordinate of the cutting head 9 of the drill 5 relative to time is recorded by a processing unit 14 which is integrated in the first component 3 of the measuring device 1 .

[0128] Exemplarily but not limiting, the processing unit 14 is configured as a digital processing unit and includes a microprocessor having a processor register to record the position of the second member 4 relative to the first member 3. As described above, the position of the second member 4 relative to the first member 3 coincides with the position x or x-coordinate of the cutting tip 9 of the drill bit 5 relative to the front end 10 of the displaceable second member 4.

[0129] The drilling distance from the second cortex to the exit (i.e., the position x or x-coordinate of the cutting head 9 of the drill bit 5 when the cutting head 9 leaves the distal cortex) is automatically calculated based on the process performed by the processing unit 14. Based on this position x or x-coordinate, the required screw length can be estimated, preferably including a safety margin. To this end, the processing unit 14 can include a data memory to store data related to the length of the bone screw, preferably including a safety margin, the screw head length, the end segment length, and the screw length increment.

[0130] The measuring device 1, in particular the displacement sensor, can be integrated in the housing 12 or can be temporarily attached to the housing. In a configuration capable of temporary attachment, the measuring device 1 comprises an attachment device in the form of an adapter 15, which can be releasably attached to the housing 12 of the surgical drill 2. The adapter 15 is exemplarily but not restrictively configured as an annular frame, which can be attached to the housing 12 by means of a press fit or via a clamping ring. Alternatively, the measuring device 1 can include a clamp to releasably attach the measuring device 1 to the housing 12.

[0131] The measuring device 1 may include a wireless communication device, which is exemplarily configured as a Bluetooth module with a signal conditioner. Via the wireless communication device, data can be wirelessly transmitted to an external computer with a monitor, a tablet computer, a smart phone, a smart watch or smart glasses to calculate or indicate the derived information, i.e., the measured position of the cutting head of the drill with respect to time, the calculated speed with respect to time and the calculated transition point can be wirelessly transmitted to an external device, such as a computer with a monitor, a tablet computer, a smart phone, a smart watch or smart glasses. Alternatively, the derived data can be provided on a display or a speaker locally mounted to the surgical drill 2.

[0132] Furthermore, the measuring device 1 comprises a sterilizable housing 16 for enclosing the processing unit 14 , a wireless communication device and a power supply 22 for the measuring device 1 , wherein the power supply 22 comprises one or more rechargeable or non-rechargeable batteries which can be arranged in the housing 16 .

[0133] Furthermore, the device 25 may further include a calibration device 27, such as Figure 7 8 and described in more detail below.

[0134] Figure 4 Another embodiment of a device 25 according to the invention is shown, wherein Figure 2 Device 25 with Figure 1 The embodiment of differs only in that the processing unit 14 is an external unit, such as a computer with a monitor, a tablet computer, a smart phone, a smart watch or smart glasses, and the measuring device 1 comprises a wireless data transmission device 17, and the processing unit 14 comprises a wireless data reception device, so that the measured distance x covered by the housing 12 in the direction of the longitudinal axis 7 and relative to the surface of the implant 26 or the bone can be transmitted from the measuring device 1 to the external processing unit 14 and recorded relative to time. The external processing unit 14 may comprise a device similar to Figure 1 An embodiment of the present invention may include a microprocessor, or may include a central processing unit.

[0135] Figure 5 and Figure 6 Another embodiment of a device 25 according to the invention is shown, wherein Figure 5 and Figure 6 The measuring device 1 of this embodiment is Figure 1 The embodiment of the invention differs in that the first member 3, which includes a laser module 18 for emitting a laser beam and a receiver for triangulation (e.g., an electronic light sensor 19 in the form of a photodiode or a charge coupled device (CCD)), is configured as part of an electronic module 31. The electronic module 31 can be inserted into a hollow space 32 formed in a handle 33 of the housing 12, wherein the hollow space 32 extends from an opening 34 at the bottom of the handle 33 to a top portion 35 of the housing 12. The opening 34 can be closed by means of a cover 36 that can be attached to the bottom of the handle 33.

[0136] In addition to the first member 3, the electronic module 31 also includes a display 30 arranged in an upper portion 37 of the electronic module 31, wherein the shape and size of the upper portion 37 are designed to cooperate with a corresponding chamber 38 constructed in the top portion 35 of the housing 12. In addition, the electronic module 31 has a lower portion 40, which includes a laser module 18, an electronic light sensor 19, a processing unit 14 and a power supply 22, which is used to drive the surgical drill 2 and to supply power to the laser module 18, the light sensor 19 and the processing unit 14. Exemplarily, the power supply 22 can be a battery or a storage battery. The shape and size of the lower portion 40 of the electronic module 31 are designed to cooperate with the hollow space 32 in the handle 33 of the housing 12. The laser window 41 is arranged in front of the lower portion 40 of the electronic module 31 and slightly lower than the upper portion 37, so that the laser beam and the electronic light sensor 19 are aligned with the corresponding windows 42, 43 ( Figure 6 )match.

[0137] A first sterile window 42 and a second sterile window 43 are arranged in the housing 12 of the surgical drill 2 to provide windows for the laser beam emitted by the laser module 18 and the reflected light beam received by the electronic light sensor 19. The first sterile window 42 and the second sterile window 43 are arranged at the front of the housing 12 (and when viewed in a front view, arranged below the longitudinal axis 7 of the spindle 13) and are located on opposite sides of a mid-plane 44 of the surgical drill 2 containing the longitudinal axis 7 and at a distance from the mid-plane 44, which allows the laser beam and the reflected light beam to pass by the spindle 13 and the chuck 6 of the surgical drill 2.

[0138] The top portion 35 of the housing 12 forms a housing 16 for the display 30, wherein the housing 16 is exemplarily but not limitingly integral with the housing 12 of the surgical drill 2 and surrounds the chamber 38. The housing 16 includes a third sterile window 45 for covering the display 30. In addition, the housing 16 is arranged on the housing 12 at a position opposite to the handle 33 of the surgical drill 2. The third sterile window 45 is angled relative to a plane orthogonal to the longitudinal axis 7 of the spindle 13 and is toward the rear end of the housing 12.

[0139] By way of example but not limitation, the measuring device 1 is suitably configured to control the rotation speed of the spindle 13 of the surgical drill 2 so that when a peak is detected by means of the measuring device 1 , the power supplied to the electric motor of the drill 2 can be shut off, thereby preventing the drill bit 5 from suddenly rushing forward.

[0140] Figures 12 to 15 Another embodiment of the device 25 according to the invention is shown again, in which Figures 12 to 15 The measuring device 1 of this embodiment is Figure 1 The embodiment of the embodiment of the invention differs in that the first component 3 comprises an electronic module 31 which, in addition to a laser module 18 for emitting a laser beam and a receiver for triangulation, also comprises an electronic light sensor 19, for example in the form of a photodiode or a charge coupled device (CCD), a display 30. In addition, the electronic module 31 comprises a processing unit 14 and a power supply 22 for the measuring device 1. The display 30 is arranged at the rear side 46 of the electronic module 31. Similar to Figure 1 In an embodiment of the present invention, a sterilizable housing 16 can be attached to a surgical drill 2 and comprises a chamber 38 for receiving an electronic module 31. A sterile front window 47 is arranged at the front of the housing 16 to allow the laser beam emitted by the laser module 18 and the reflected beam reflected by means of a reflector 20 arranged at the second member 4 of the measuring device 1 to pass.

[0141] The laser module 18 and the electronic optical sensor 19 receiving the reflected light beam to perform triangulation are arranged laterally spaced from each other in the electronic module 31 so that the laser beam and the reflected light beam pass over the longitudinal axis 7 of the mandrel 13 when viewed in a front view of the assembled first component 3.

[0142] The housing 16 comprises an adapter 15 for fixing the first member 3 of the measuring device 1 to the housing 12, wherein the adapter 15 can be releasably attached to the housing 12 of the surgical drill 2. The adapter 15 is configured exemplarily but not limitingly as an annular frame, which can be attached to the housing 12 by means of a clamping ring 48, which can be fixed to a stationary part of the spindle 13, for example, by means of a clamping screw 49.

[0143] The clamping ring 48 is positioned on the housing 16 at a position laterally offset relative to the longitudinal center plane of the housing 16 to allow the laser beam and the reflected beam to pass by the drill 5. In addition, by means of the adapter 15, the housing 16 is attached to the surgical drill 2 at an angle relative to the longitudinal axis 7, so that the laser beam is emitted at an angle to the longitudinal axis 7, thereby allowing the size of the reflector 20 of the second member 4 of the measuring device 1 to be reduced.

[0144] The housing 16 is sterilizable and is constructed as a separate part arranged on top of the housing 10. The chamber 38 has an opening at the rear side of the housing 16 and can be closed by means of a cover 51 that can rotate around an axis located at the lower side of the housing 16 and extending orthogonally to the longitudinal axis. The cover 51 includes a sterile rear window 52 for covering the display 30, wherein the rear window 52 is angled relative to a plane orthogonal to the longitudinal axis 7 of the spindle 13 and is oriented toward the rear end of the housing 12 when the cover 51 is closed.

[0145] By way of example but not limitation, an actuator 53 for a power switch of the electronic module 31 may be arranged inside the cover 51 so that when the cover 51 is closed, energy is supplied from the power supply 22 to the electronic components of the measuring device 1. In order to operate the processing unit 14, the laser module 18 and the electronic light sensor 19, one or more buttons 54 may be positioned at the rear side of the electronic module 31. The sterile rear window 52 may be provided with a recess in order to provide weakened areas in the rear window 52, ​​which allow actuation of the one or more buttons 54 when the cover 51 is in its closed position.

[0146] Figure 1 , Figures 4 to 6 as well as Figures 12 to 15 The processing unit 14 of an embodiment comprises a microprocessor or a central processing unit including processor registers to record the distance x covered by the housing 12 in the direction of the longitudinal axis 7 and relative to the surface of the implant 26 or the bone relative to time during the drilling process.

[0147] It must be noted that real-time feedback of the current drill depth alone can be of high value to the surgeon. More valuable information is delivered by the current drilling speed. This helps the surgeon control his feed rate to avoid mechanical or thermal damage to the bone, or can be used to estimate bone quality.

[0148] Fig.16 Another embodiment of a reflector 20 is shown which is not integral with nor attached to the drill sleeve 23. The reflector 20 can be clamped to the drill bit 5 in such a way that it can slide on the drill bit 5, making the reflector 20 independent of the construction of the drill sleeve 23. The reflector 20 has a disc-shaped portion 55 and a clamping portion 56 on each side adjacent thereto, which clamping portion comprises a longitudinal slot so as to form a tongue suitable for applying radial pressure to the drill bit 5.

[0149] The method for estimating the length of a bone screw from drilling characteristics basically comprises the following steps: A) advancing the surgical drill 2 coaxially relative to the longitudinal axis of the spindle 13 to drill a hole in the bone, and recording the position (x) of the cutting tip 9 of the drill 5 relative to the surface of the bone or implant 26 in the drilling direction relative to time; B) using the selected reference pattern G Ref and the selected reference graph G Ref determining the moment when the cutting tip 9 of the drill bit 5 leaves the cortex of the bone by defining a reference position of the transition 21' of the drill bit 5 from the first medium to the second medium; C) determining the distance [x(t)] covered by the drill bit 5 at the moment determined in step B); and D) selecting a bone screw having a length corresponding to the distance [x(t)] covered by the drill bit 5 determined in step C) taking into account a predetermined safety margin.

[0150] As mentioned above, the position x of the cutting head 9 of the drill 5 relative to the surface of the bone or implant 26 in the drilling direction is set to zero at the beginning of the drilling process. However, this zero position of the cutting head 9 of the drill 5 depends on the following fact, whether:

[0151] 1) The displaceable second member 4 comprises a drill sleeve 23 extending to the front end 10 of the second member 4 in the direction of the longitudinal axis 7, such as Figure 3 , Figure 4 and Figures 11a to 11e shown; or whether

[0152] 2) The drill sleeve is a separate component that has been previously inserted into the soft tissue covering the bone to be treated; or

[0153] 3) The zero position of the cutting tip 9 will be set relative to the implant 26 (e.g. bone plate). In the case where the drill 5 is guided in the drill sleeve 23, the drill sleeve contacts or is attached to the bone plate during drilling and thus does not allow the cutting tip 9 of the drill 5 to abut the upper surface of the bone plate ( Fig. 9 ), the starting point of the measurement can be determined using a calibration device 27 ( FIG. 8 ) which provides a physical stop 28 inside the drill sleeve 23 at a height corresponding to the upper surface of the bone plate. Alternatively, if the length of the drill bit 5 and the drill sleeve 23 are known, the starting point can be calculated from this data.

[0154] With regard to the above variant 1), the method comprises the following steps before step A):

[0155] Positioning the surgical drill 2 relative to the bone so that the front end 10 of the displaceable second member 4 and the cutting tip 9 of the drill bit 5 abut the bone surface; and

[0156] The relative position is stored as a starting point (x=0) for measuring the position x of the cutting tip 9 of the drill 5 relative to the bone surface in the drilling direction with respect to time.

[0157] As for the above variant 2), the method comprises the following steps before step A):

[0158] Positioning the surgical drill 2 relative to the bone so that the front end 10 of the displaceable second member 4 abuts against a drill sleeve 23 inserted into the soft tissue covering the bone to be treated; and

[0159] adjusting the cutting tip 9 of the drill 5 secured in the chuck 6 of the surgical drill 2 relative to the displaceable second member 4 so that the cutting tip 9 of the drill 5 abuts the surface of the bone; and

[0160] The relative position is stored as a starting point (x=0) for measuring the position x of the cutting tip 9 of the drill 5 relative to the bone surface in the drilling direction with respect to time.

[0161] As for the above-mentioned variant 3), the method comprises the following steps before step A): Fig. 9 and Fig.10 ):

[0162] By using the calibration device 27 ( Figure 7 and FIG. 8 ) positioning the drill bit 5 fixed in the chuck 6 relative to the displaceable second member 4 so that the front end 10 of the second member 4 contacts the surface 29 of the calibration device 27 and the cutting tip 9 of the drill bit 5 abuts against the stopper 28 protruding from the surface 29 of the calibration device 27;

[0163] storing the relative position as a starting point (x=0) for measuring the position x of the cutting tip 9 of the drill 5 relative to the surface of the bone or implant 26 in the drilling direction relative to time; and

[0164] The surgical drill 2 is positioned relative to the implant 26 (eg, a bone plate) so that the front end 10 of the displaceable second member 4 abuts against the surface of the implant 26 (eg, Fig. 9 ).

[0165] Fig.17 Another embodiment of the calibration device 27 is shown. The reflector 20 and the calibration device 27 (e.g., Figure 7 and Figure 8) can be made for one-time use. In other embodiments, according to Figures 11a to 11e , Fig.16 and Fig.17 The drill sleeve 23 of one of the embodiments shown in FIG. 2 can also be designed as a disposable component and, for this purpose, can be connected to the calibration device 27 via a predetermined breaking point.

[0166] Although the invention has been described in conjunction with its specific embodiments, it is evident that many alternatives, modifications and variations are apparent to those skilled in the art. Therefore, the present invention is intended to encompass all such alternatives, modifications and variations that fall within the scope of the appended claims.

[0167] It should be understood that certain features of the invention described in the context of separate embodiments for the sake of clarity may also be provided in combination in a single embodiment. Conversely, various structures of the invention described in the context of a single embodiment for the sake of simplicity may also be provided individually or in any suitable sub-combination, or as appropriate in any other described embodiment of the invention. Certain features described in the context of various embodiments should not be considered essential features of those embodiments, unless the embodiment does not function without those elements.

Claims

1. A surgical instrument (25), comprising: - drive unit; - a cutting tool or a drill bit (5) which can be engaged with the drive unit; a measuring device (1) attached to the surgical instrument (25) or integral with the surgical instrument, wherein the measuring device (1) is configured to measure the distance [x(t)] covered by the cutting tool or drill bit (5) along a cutting or drilling path relative to time and relative to a reference position; a processing unit (14) directly connected electronically to the measuring device (1) and suitably programmed to record a graph G of the distance [x(t)] covered by the cutting tool or drill (5) during the cutting or drilling process relative to the reference position and relative to time; as well as - digital data storage devices, Features Reference data are stored in the digital data storage device, the reference data comprising at least one data set specifying a reference graph G of the distance [x(t)] covered by a cutting tool or drill bit (5) during a cutting or drilling process relative to time and within a time window (11) within which the cutting tool or drill bit (5) transitions from a first medium with a first density to a second medium with a different second density. Ref ,in At least one reference pattern G Ref a reference point (21') defining the transition of the cutting tool or drill bit (5) from the first medium to the second medium; and wherein The time window (11) includes a first time period before the reference point (21') of the transition and a second time period after the reference point (21') of the transition; and The processing unit (14) is suitably programmed to compare the recorded pattern G with the at least one reference pattern G by means of a similarity measure. Ref Comparing to quantify the difference between the recorded pattern G or at least a portion of the recorded pattern G and the at least one reference pattern G Ref , thereby finding the position x of the transition (21) in the recorded graph G.

2. A surgical instrument according to claim 1, wherein the digital data storage device also stores a predetermined threshold value of the similarity metric, and wherein the processing unit (14) is programmed to trigger an event and report the position x of the transition (21) if the threshold value of similarity is reached.

3. The surgical instrument according to claim 2, wherein the digital data storage device is configured as a buffer to keep the actual time window of the current graph G of the distance [x(t)] at least consistent with the reference graph G Ref The window (11) is the same size.

4. The surgical instrument according to claim 1 , wherein the plurality of reference patterns G Ref stored in the digital data storage device, representing various drilling or cutting characteristics, and wherein the processing unit (14) is suitably programmed to repeat the following steps: with the aid of all stored reference patterns G Ref The similarity metric is used to quantify the similarity between the recorded graph G or the at least one portion of the recorded graph G and the reference graph G. Ref The consistency between graph G and all reference graphs G Ref The overall best fit between , thereby identifying the position x of the transition (21) in the recorded graph G.

5. The surgical instrument according to claim 1 , wherein each reference pattern G Ref At least 10 values ​​of said distance [x(t)] covered by the cutting tool or drill (5) are specified, said values ​​being subsequent values ​​relative to the time within said second time period after a reference point (21') of said transition.

6. The surgical instrument according to claim 5, wherein each reference pattern G Ref At least 20 values ​​of said distance [x(t)] covered by the cutting tool or drill (5) are specified, said values ​​being subsequent values ​​relative to the time within said second time period after a reference point (21') of said transition.

7. The surgical instrument according to claim 5, wherein each reference pattern G Ref At least 30 values ​​of said distance [x(t)] covered by the cutting tool or drill (5) are specified, said values ​​being subsequent values ​​relative to the time within said first time period before a reference point (21') of said transition.

8. The surgical instrument according to claim 7, wherein each reference pattern G Ref At least 40 values ​​of said distance [x(t)] covered by the cutting tool or drill (5) are specified, said values ​​being subsequent values ​​relative to the time within said first time period before a reference point (21') of said transition.

9. The surgical instrument according to claim 1 , wherein in each reference pattern G Ref The second time period after the reference point (21') of the transition amounts to at least 0.1 seconds.

10. The surgical instrument according to claim 9, wherein in each reference pattern G Ref The second time period after the reference point (21') of the transition amounts to at least 0.3 seconds.

11. The surgical instrument according to claim 9, wherein in each reference pattern G Ref The first time period before the reference point (21') of the transition amounts to at least 0.3 seconds.

12. The surgical instrument according to claim 11, wherein in each reference pattern G Ref The first time period before the reference point (21') of the transition amounts to at least 0.4 seconds.

13. The surgical instrument according to claim 1 , wherein the reference data is a reference to a graph G Ref Designated as having a monotonically increasing distance [x(t)] covered by the cutting tool or drill (5) during the first period of time before reaching the reference point (21') of the transition.

14. The surgical instrument according to one of claims 1 to 3, wherein the surgical instrument (25) further comprises a surgical cutting or drilling device.

15. A surgical instrument according to claim 14, wherein the surgical drilling device is a surgical electric drill (2), wherein the drive unit comprises a motor and a spindle (13), the spindle being drivable by the motor and having a longitudinal axis (7), so that the reference point can be defined by the surface of an implant (26) or a bone.

16. The surgical instrument according to one of claims 1 to 3, wherein the processing unit (14) is one of a computer with a monitor, a tablet computer, a smart phone, a smart watch or smart glasses.

17. The surgical instrument according to one of claims 1 to 3, wherein the processing unit (14) comprises a wireless communication device.

18. The surgical instrument of claim 17, wherein the wireless communication device is a Bluetooth module.

19. The surgical instrument of claim 15, wherein the surgical instrument further comprises a housing (12).

20. The surgical instrument according to claim 19, wherein the measuring device (1) comprises attachment means.

21. The surgical instrument according to claim 20, wherein the attachment means is an adapter (15) releasably attachable to the housing (12) of the surgical drill (2).

22. The surgical instrument according to one of claims 19 to 21, wherein the measuring device (1) comprises a clamp to releasably attach the measuring device (1) to the housing (12).

23. The surgical instrument according to claim 21, wherein the adapter (15) is configured to be attachable to a frame of the housing (12).

24. The surgical instrument according to claim 23, wherein the frame is an annular frame fixed to the housing (12) by means of a press fit.

25. The surgical instrument according to one of claims 19 to 21, wherein the measuring device (1) is integral with the housing (12).

26. The surgical instrument according to claim 1, wherein the reference graph G is applied to select the best fit among the graphs G. Ref The part of finding the similarity measure of the position x of the transition (21) in the recorded graph G is a pattern recognition method.

27. The surgical instrument of claim 26, wherein the pattern recognition method is a shape context descriptor.

28. A surgical instrument according to one of claims 1 to 3, wherein the reference data specifies a statistical representation of a graph G of multiple expected records within a range of transitions of a cutting tool or drill bit (5) from a first medium having a first density to a second medium having a different second density during a cutting or drilling process.

29. The surgical instrument of claim 14, wherein the reference data is continuously modified during use of the cutting or drilling device.

30. The surgical instrument of claim 29, wherein the modification of the reference data is performed by a machine learning algorithm.

31. The surgical instrument of claim 30, wherein said modification of said reference data is performed by involving the use of a neural network.

32. The surgical instrument according to one of claims 19 to 21, wherein the measuring device (1) comprises a contactless displacement sensor.

33. The surgical instrument of claim 32, wherein the non-contact displacement sensor is a triangulation distance sensor and comprises a light transmitter and a corresponding receiver.

34. The surgical instrument of claim 32, wherein the non-contact displacement sensor comprises an LED light emitter.

35. The surgical instrument according to claim 32, wherein the measuring device (1) comprises a laser device comprising a laser module (18) and one or more electronic light sensors (19).

36. The surgical instrument according to claim 35, wherein the electronic light sensor (19) is a charge coupled device (CCD) to perform laser triangulation for displacement evaluation.

37. A surgical instrument according to claim 35 or 36, wherein the non-contact displacement sensor is radar based.

38. The surgical instrument of claim 37, wherein the non-contact displacement sensor is a millimeter wave radar sensor.

39. The surgical instrument of claim 35 or 36, wherein the non-contact displacement sensor is an ultrasonic distance sensor.

40. The surgical instrument of claim 32, wherein the non-contact displacement sensor comprises a reflector (20) slidable along the drill bit (5) and configured to abut an implant (26), bone, or instrument.

41. The surgical instrument according to claim 32, wherein the processing unit (14) further comprises a display (30) or a speaker.

42. The surgical instrument according to claim 41, wherein the measuring device (1) comprises a housing (16) for enclosing the processing unit (14).

43. The surgical instrument according to claim 42, wherein the housing (16) enclosing the treatment unit (14) is sterilizable.

44. The surgical instrument according to claim 42 or 43, wherein the measuring device (1) comprises: a first member (3) which is in a fixed position relative to the housing (12); as well as A longitudinal second member (4) which is displaceable relative to the first member (3) substantially in the direction of the longitudinal axis (7) of the spindle (13) and comprises a front end (10) adapted to abut against a surface of a bone or an implant (26).

45. The surgical instrument according to claim 44, wherein the second displaceable member (4) comprises a drill sleeve (23) extending in the direction of the longitudinal axis (7) to the front end (10) of the second member (4).

46. ​​The surgical instrument according to claim 44, wherein the first component (3) of the measuring device (1) and the processing unit (14) are insertable into a hollow space (32) arranged in the housing (12) of the surgical drill (2).

47. A surgical instrument according to claim 46, wherein the first component (3) and the processing unit (14) are part of an electronic module (31), the electronic module also comprising a power supply (22) and a motor for driving the surgical drill (2), and wherein the power supply (22) is configured to supply electrical energy to the first component (3) and the processing unit (14) and the motor.

48. The surgical instrument according to claim 47, wherein the hollow space (32) is arranged in the handle (33) of the housing (12) and is configured to receive the electronic module (31).

49. The surgical instrument of claim 41, wherein the housing (12) includes a top portion (35) including a sterilizable window (45) for covering the display (30).

50. The surgical instrument according to claim 49, wherein the top portion (35) is integral with the housing (12) and forms a casing for the display (30).

51. A surgical instrument according to claim 35 or 36, wherein the housing (12) includes at least one sterile window (42, 43) to provide a window for signals transmitted by the non-contact displacement sensor and reflected signals that can be received by the non-contact displacement sensor.

52. The surgical instrument according to claim 51, wherein the sterile window (42, 43) is configured as a recessed window.

53. A surgical instrument according to claim 47 or 48, wherein the housing (16) is attachable to the casing (12) by means of an adapter (15) and comprises a chamber (38) configured to receive the electronic module (31).

54. The surgical instrument according to claim 42 or 43, wherein the housing (16) comprises a cover (51) which is arranged at the rear end of the housing (16) and comprises a sterilizable rear window (45) for covering the display (30).

55. A surgical instrument according to claim 42 or 43, wherein the housing (16) includes at least one sterile front window (47) to provide a window for signals transmitted by the non-contact displacement sensor and reflected signals that can be received by the non-contact displacement sensor.

56. The surgical instrument according to claim 44, wherein the second displaceable member (4) comprises a clamping portion (56) for attachment to a cylindrical structure having a variable diameter.

57. The surgical instrument according to claim 56, wherein the clamping portion (56) of the second displaceable member (4) is configured to provide a friction fit with a drill bit (5).

58. A surgical instrument according to claim 32, wherein the measuring device (1) is positioned relative to the housing (12) so that the light beam emitted by the non-contact displacement sensor is oriented at an offset angle relative to the longitudinal axis (7) of the spindle (13).

59. The surgical instrument according to claim 44, wherein the first member (3) of the measuring device (1) is positioned eccentrically with respect to the longitudinal axis (7) of the spindle (13).

60. The surgical instrument according to one of claims 1 to 3, wherein the measuring device (1) comprises at least one accelerometer.

61. The surgical instrument according to one of claims 1 to 3, wherein the measuring device (1) further comprises a gyroscope and / or a magnetometer.

62. The surgical instrument according to one of claims 1 to 3, wherein the surgical instrument further comprises a calibration device (27).

63. The surgical instrument according to one of claims 1 to 3, wherein the processing unit (14) is programmed for real-time calculations.

64. The surgical instrument according to one of claims 1 to 3, wherein the processing unit (14) comprises a data memory to store data related to the length of the bone screw.

65. The surgical instrument of claim 64, wherein the data includes a safety margin, a screw head length, a tip segment length, and a screw length increment.

66. A surgical instrument according to claim 15, wherein the processing unit (14) is suitably programmed to control the rotation speed of the spindle (13) of the surgical drill (2) or to stop the spindle (13) when the transition (21) is detected.

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