NL2036781B1

NL2036781B1 - Method and system for selecting an implant

Info

Publication number: NL2036781B1
Application number: NL2036781A
Authority: NL
Inventors: Kölling Bart; Moree Tijs; Baltus Laurensz Schornagel Justus
Original assignee: Slam Ortho B V
Priority date: 2024-01-10
Filing date: 2024-01-10
Publication date: 2025-07-22
Also published as: WO2025151033A1

Abstract

1 8 A method of selecting an implant to be placed into a bore in a bone is disclosed. The method comprises: providing a user interface system comprising a visual display; providing, in the system, a bone property signal representing a mechanical property of the bone along the depth of the bore; and graphically displaying the bone property signal as a function of bore depth using the display of the user interface system. The method further comprises the steps of: providing, in the system, an implant property signal representing at least a length of at least one implant of a predetermined set of implants for selection to be placed into the bore; displaying, using the display of the user interface system, the implant property signal in visual relation to the graphically displayed bone property signal; and selecting, based on the displayed signals, one of the implants to be placed into the bore.

Description

Method and system for selecting an implant

The present invention relates to a method of selecting an implant to be placed into a bore in a bone.

The present invention further relates to a system for selecting an implant to be placed into a bore drilled in a bone during surgery.

In the field of internal fixation in orthopaedic or trauma surgery, implants are placed in bone to fixate fragments in place to allow for proper healing of the bone. This may be used to treat a fractured bone or, during an osteotonty wherein a bone is intentionally sawed (or broken) into multiple pieces, to correct an anomaly in the bone structure.

The process of fixating a bone is called osteosynthesis. Types of implants that can be used during osteosynthesis include screws, wires, nails, and pins. For instance, during an osteosynthesis procedure, a bone screw may be placed in a plate with holes and into a bore in a bone or placed into a bore in a bone without a plate or be placed into a bore in a bone through an intermedullary nail.

In osteosynthesis, first a bore is drilled into the bone. Optionally, during one or more interruptions of the drilling, an X-ray image is taken to check the position of the cutting tool and to check its progress. Once a bore with the desired depth has been drilled, an appropriate implant is to be selected. To select an implant with an appropriate length, it is useful to know the depth of the bore.

Often, the bore depth is measured with a manual depth gauge. Determining the required implant length with a manual depth gauge can be a hassle as the tool is cambersome to use and the measurements are often inaccurate. At times, an additional X-ray image is taken with the depth gauge in place to ensure that the information the gauge provides is accurate. A second property that is of importance for a well-informed implant choice, is the density of the bone. The density determines the ability of the bone to hold implants. Based on this bone density different implant types are better suited. The different implant types differ on properties such as pitch, thread width or thread angle.

Based on the bore depth manually measured using the depth gauge, it is decided what implant to use. The selected implant is placed into the bore. Optionally, an additional X-ray image is taken to evaluate whether the implant indeed has an appropriate length and is properly placed, in particular whether the distal tip of the implant is seated in a dense bone part such as the cortical bone. If not, the implant is removed. the bore depth may be remeasured, and a new implant is placed into the bore. In some cases, even further drilling of the bore may be required.

To verify whether the newly placed implant is of the appropriate length, an additional X-ray image may be made. Each time an X-ray image is taken, the people in the operating room are exposed to the radiation.

Thus, conventional bore depth measurement techniques are often inconvenient, time-consuming and unreliable, and too often require trial-and-error and multiple X-ray exposures before a correct implant is inserted. Moreover, too often implants are wasted due to inaccurate depth measurements, as single-use implant packaging dictates that the implant cannot be resterilised and cannot be used in another patient. The cost of wasted implants, like the cost of the procedural delays due to incorrect implant selection, is considerable.

Furthermore, not all implant misplacements are identified during the procedure due to the two- dimensional nature of X-ray images. These misplaced implants could subsequently lead to complications such as an unstable fixation. Complications due to wrong implant lengths result in pain, tissue damage, joint impairment, and discomfort. Implant-related complaints are one of the most frequent reasons for revision surgery.

Other conventional methods include preoperative three-dimensional planning, X-ray-based solutions, and density estimation methods. Preoperative three-dimensional scans lead to considerable radiation exposure and are time and resource intensive. With a two-dimensional X- ray image of a bone, it is hard to determine the bone structures to be encountered when drilling and to determine, after drilling, the location of the bore and a precise implant length. Further, a DXA scan for bone density estimation cannot be performed during surgery and is thus not suitable in an emergency in which the patient must be immediately operated on and cannot be scanned first.

Other solutions may require additional tools and steps to be performed, which could disturb the worktlow of the surgeon. Moreover, additional steps could lead to additional risks.

Altogether, the conventional bore depth measurement methods may result in measurement inaccuracies, which leads to implant misplacements and/or to increased radiation exposure, operating room times, and costs.

It is an object of the present invention, amongst other objects, to provide an improved method of selecting an implant to be placed into a bore in a bone, in particular wherein the aforenoted drawbacks are at least partially solved.

Hereto, a method of selecting an implant to be placed into a bore in a bone is provided, wherein the method comprises the steps of: - providing a user interface system comprising a visual display; - providing, in the system, a bone property signal representing a mechanical property of the bone along the depth of the bore; - graphically displaying the bone property signal as a function of bore depth using the display of the user interface system; - providing, in the system, an implant property signal representing at least a length of at least one implant of a predetermined set of implants for selection to be placed into the bore; - displaying, using the display of the user interface system, the implant property signal in visual relation to the graphically displayed bone property signal; - selecting, based on the displayed signals, one of the implants to be placed into the bore.

Displaying one or more implant lengths in visual relation to the bone property along the depth of the bore facilitates accurately selecting an implant to be placed into a bore in a bone and enables the surgeon to select an appropriate implant in a time-efficient manner. Moreover, as the implant can be selected more accurately, fewer X-ray images are needed such that radiation exposure can be reduced. Furthermore, more accurate depth measurements reduce implant waste since the screws will be correctly placed more often, and thus decrease overall costs. Additionally, the safety and satisfaction of patients may be improved by ensuring fewer complications and fewer revision surgeries.

Typically, the length dimension of the implant to be selected does not match the depth dimension of the bore. Specifically a head of the implant, such as a screw, typically protrudes a certain extent out of the bore and a tip thereof may protrude beyond the cortical bone. By having the tip of the screw protrude beyond the cortical bone, it may be ensured that the thread of the screw optimally engages the cortical bone to maximise the grip of the screw. By visualising the implant, especially its length, in addition to the bone property along the depth of the bore, the user can more accurately select an implant of an appropriate length more conveniently while taking into account the exact circumstances such as bone properties and implant specifications and requirements.

Preferably, the step of displaying the implant property signal comprises graphically displaying the length of the at least one implant of the set of implants along the bore depth. It is then further preferred if the step of graphically displaying the length of the at least one implant of the set of implants comprises displaying the length of the at least one implant together with the graphically displayed bone property signal overlayed onto each other. Thus, the implant length and the mechanical bone property are displayed in a single graphical representation. For instance, the graphically displayed implant length may be overlayed onto the graphically displayed bone property signal.

According to a preferred embodiment of the method, the bone property signal is graphically displayed as a one-dimensional heatmap. The mechanical property of the bone is preferably the density of the bone. Thus, the bone density along the depth of the bore may be visualised by means of respective shades, colours or tints in dependence of the density value at each depth value. For instance, the density of the densest bone parts may be indicated in white, the density of the least dense bone parts may be indicated in black, and densities therebetween may be indicated in shades of grey.

The method can provide the user, such as a surgeon, with a clear and quantitative insight into the structure of the bone. In previous methods, the surgeon attempts to feel the structure of the bone while drilling thereinto. By, instead, quantifying the bone structure and displaying the information as a one-dimensional heatmap representing the bone density as a function of the bore deph, the user can be provided with much more accurate information relating to implant selection. This way, for instance, the user can determine what bone screw to place into the bone in order to minimise the extent the bone screw protrudes out of the bone, while ensuring the screw is optimally seated into the deepest part of the dense cortical bone by reading the width of the cortical bone from the density map and choosing an implant that will reach this deepest part. Furthermore, based on the information about the density and/or other parameters, the user can determine whether a special type of implant should be used, for instance an implant especially configured to be used for soft bone. Also, based on the anatomical information, the user can see whether the drilled bore 1s too shallow or whether the surgeon drilled too far. For example, if the surgeon has drilled through one bone into another, there is the risk that a bone screw is placed in both bones such that mutual movement of the bones is blocked, which may immobilise the patient such that another surgery is required to remove the bone screw from the other bone. Such screw placement in both bones can be prevented because, if the surgeon has drilled through one bone into another, the density map would show more sections of dense cortical bone than expected.

Preferably, the user interface system further comprises a processor.

The method preferably further comprises, using the processor, the steps of comparing the bone property signal with a predetermined threshold value, determining, based on the comparison between the bone property signal and the predetermined threshold value, a bore depth at which the bone property signal exceeds the predetermined threshold value close to a deep end of the bore, and selecting. based on the determined bore depth close to the deep end of the bore and on the lengths of the implants of the set of implants, at least one implant to be suggested from the set of implants, wherein the implant property signal represents at least the length of the at least one 5 implant to be suggested. The predetermined threshold may be a dynamic threshold, i.e., a threshold calculated by, e.g.. an anomaly detection algorithm and continuously trained or updated by recent historical values. Specifically, the step of determining the bore depth close to the deep end of the bore comprises detecting, based on the comparison between the bone property signal and the predetermined threshold value, cortical bone closest to the deep end of the bore, wherein the at least one implant to be suggested is determined based on the depth of the detected cortical bone and the lengths of the implants for selection. Particularly, the processor detects the number of times that the bone property signal is higher than the threshold value, to determine the number of cortical bone areas drilled through, preferably wherein the processor provides a signal when the number surpasses a predetermined value, the signal indicating that the bore is complete, and wherein the method further comprises the step of displaying this number using the user interface system, preferably as an integer number, and/or stopping the drilling machine from further drilling.

Preferably, the step of providing the bone property signal comprises providing, in the system, drilling signals representing at least a drilling distance and at least one or both of an axial drilling force and a drilling torque during drilling of the bore, and determining, based on the drilling signals, the bone property signal, preferably using the processor. Using both the axial force and the torque can improve the accuracy even further and allows for compensation for blunt drill bits.

Alternatively, the input signal represents the energy expended by the drill during drilling, which corresponds to the product of the axial force and the drilling distance and to the product of the torque and the angular displacement of the drill bit.

The drilling parameters may be measured during drilling and the drilling signals representing the drilling parameters may be subsequently provided as input into the system and further processed by the system, in particular to calculate the mechanical bone property represented by the bone property signal.

According to a further preferred embodiment of the method, the step of graphically displaying the bone property signal comprises continuously updating the graphically displayed bone property signal in real-time.

A further preferred embodiment of the method comprises the steps of repeatedly providing, in the system, at least one real-time drilling risk parameter representative of a drilling-related risk during drilling of the bore, such as drill bit bluntness, and, when the at least one drilling parameter exceeds a preset threshold, outputting a warning signal using the user interface system, preferably outputting an audible warning signal and/or indicating a visual warning signal using the user interface system. Preferably, the drilling parameter is compared with the threshold using the processor. Thus, during drilling, a warning relating to an excessive drilling force, rotational speed, heat generation, or relating to drill bit bluntness can be provided. To determine the heat generation of the bone, the processor may integrate the drilling torque and axial force over distance to calculate the work needed for creating the bore. Next, for different depth segments of the bone along the bore, typically having mutually different bone densities, heat generation in the bone can be determined by calculating the work per unit bone volume using the drill diameter and distance drilled. Alternatively, or additionally, a tissue layer transition warning may be provided. That is, a threshold for detecting the transition of the drill bit into another tissue layer, for example from cortical bone into soft tissue, may be implemented, wherein a change in a mechanical property is evaluated, preferably using the processor. If a change is detected, the detection of a tissue layer transition may result in a warning signal.

A further preferred embodiment of the method comprises the steps of determining, based on the bone property signal, a bone quality signal representing a quality of the bone, and displaying the bone quality signal using the user interface system. For instance, the step of displaying the bone quality signal may comprise displaying a numerical value indicative of the bone quality signal.

A further preferred embodiment of the method comprises a step of measuring the bore depth as a distance from a reference point.

A further preferred embodiment of the method comprises the steps of providing, in the system, a drilling anomaly detection signal representing at least one or both of a lateral drilling force and a drilling direction during drilling of the bore, and indicating the drilling anomaly detection signal using the user interface system.

According to a further preferred embodiment of the method, a preceding bone property signal representing a mechanical bone property along the depth of another bore is graphically displayed, using the display of the user interface system, as a function of bore depth alongside the graphically displayed current bone property signal.

According to a further aspect of the present invention, a system for selecting an implant to be placed into a bore drilled in a bone is provided, wherein the system comprises: - at least one sensor, arranged to provide at least one signal for determining a depth of the bore and for determining a mechanical property of the bone along the depth of the bore; - a processor, arranged to receive the at least one signal from the at least one sensor and configured to determine, based on the at least one signal. a depth of the bore and the mechanical property of the bone along the depth of the bore, wherein the processor is further configured to provide a bone property signal representing the mechanical property of the bone along the depth of the bore; - a user interface system comprising a visual display and arranged to receive the bone property signal and an implant property signal representing at least a length of at least one implant of a predetermined set of implants for selection to be placed into the bore, wherein the user interface system is configured to, using the display, graphically display the bone property signal as a function of bore depth and display the implant property signal in visual relation to the graphically displayed bone property signal.

A preferred embodiment of the system comprises a drill bit and at least one of a rotatable drill bit unit and a drilling machine for driving the drill bit into the bone, the drill bit unit comprising a component housing and the drill bit.

Preferably, the at least one sensor is arranged in the one of the drill bit unit and the drilling machine.

The at least one sensor may comprise a strain gauge mounted in and/or on the drill bit unit or on a drive shaft of the drilling machine and arranged to produce a signal representing a force exerted on the drill bit during drilling. It is then preferred if multiple strain gauges are mounted on the drill bit and arranged to produce signals representing both axial force and/or torque exerted on the drill bit.

Using both the axial force and the torque can improve the accuracy even further and allows for compensation for blunt drill bits.

Alternatively, or additionally, the at least one sensor comprises a contactless distance sensor arranged to produce a signal representing a distance between the sensor and a reference point on the system during drilling, the distance representing the penetration depth of the drill bit in the bone.

According to a preferred embodiment of the system, the processor is arranged in the drill bit unit.

According to a further preferred embodiment of the system, a power source, such as a battery, for powering the at least one sensor is arranged in the drill bit unit.

Preferably, the processor is configured to communicate wirelessly.

The present invention is further illustrated by the following figures, which are not intended to limit the scope of the invention in any way, wherein: - figure 1 shows a schematic side view of a drilling machine; - figure 2 shows a schematic front view of a preferred embodiment of a user interface; - figure 3 shows a schematic block diagram of the steps relating to the data processing and the calculation of the information to be displayed; - figure 4 shows a schematic block diagram representing a bone density calculating algorithm; - figure 5 shows a schematic block diagram representing a detection algorithm.

In figure 1 a drilling machine 10 is shown in a schematic side view. The drilling machine 10 comprises a drive shaft driving a drill chuck 14 that holds a drill bit unit 16, which contains a sensor unit 11 and comprises the drill bit 17. The drill bit unit 16 is releasably mounted in the drill chuck 14 to allow interchanging between different drill bit units 16. The drilling machine 10 is operable by means of the trigger 13 on the housing 12. The sensor unit 11 continuously gathers data from its sensors, measuring the distance to a reference point or surface, the axial force applied to, and the angular velocity of, the drill bit 17. Other signals may include the lateral force on the drill bit 17 and the drill direction or drill bit pitch. Signals, gathered by the sensor unit 11 during drilling into a bone 20, are processed by a processor, included in the drill bit unit 16, and thereatter wirelessly communicated to a user interface 30 as shown in figure 2.

The sensor unit 11 comprises a distance sensor arranged to emit an electromagnetic wave to a reference surface reflecting the electromagnetic wave, to receive the reflected electromagnetic wave and to produce a signal based on the received electromagnetic wave, the signal representing the distance. This way, data related to the depth of the bore can be obtained. The distance between the sensor and the reference surface may be calculated on the basis of the reflection angle, the phase or time difference and/or the intensity of the received wave. Especially, the sensor emits infrared laser light through a collimation lens in a dot pattern on the reference surface. The light reflected from the reference surface is received by a receiver lens which projects the reflected dot pattern onto a CMOS image sensor. Additionally, the reflected laser light may pass through an optical filter arranged near the receiving lens which only transmits infrared light. Strain gauges

(not shown) are glued to the surface of the drill bit unit 16 by an adhesive, such as cyanoacrylate.

Information about the axial force and the torque exerted on the drill bit 17 are picked up by the strain gauges. The signals that are created by the strain gauges are measured with a Wheatstone bridge. Based on the axial force and the torque determined by the strain gauges, the density that is encountered by the drill bit 17 can be calculated.

Specifically, two distance sensors may be arranged on opposite sides of the drill bit 17. In this manner the processor can determine, based on the difference between the distances measured by the two distance sensors, the angle of the drill bit 17 and display this information on the user interface 30.

The outer layer of the bone 20, the cortices 21, comprises cortical bone which has a higher density.

The inside of the bone 20 comprises trabecular bone 22, containing bone marrow and having a lower density. It is preferred to select an implant that passes through both cortices 21. As described further below, a suitable implant, in this example a bone screw 39, can be selected by a user in an efficient manner using the user interface 30. More specifically, the interface 30 can be used to automatically obtain and display a recommended screw length based on sensor data trom drilling, to allow the user to determine the correct length accurately and quickly.

Figure 2 shows the visual display 31 that displays the information that is wirelessly communicated by the processor of the drill bit unit 16 to the user interface 30. The visual display 31 displays at the start a new, blank, one-dimensional bone density heatmap 33, representing the bone density as a function of the bore depth. Incrementally the displayed bone density heatmap 33 is updated and shown on the visual display 31 based on live measurements. Here, the densest bone parts are indicated in black and the least dense parts are indicated in white. During this process, the bone density heatmap 33 is a graphical representation of the bone density along a length scale over the drilling trajectory. This density map 33 is visualised in the form of a heatmap 33 wherein different colours, shades or tints indicate the different densities calculated based on the drilling signals.

Also, additional drilling parameters such as the current position of the drill can be read from the screen. The live depth indicates the best screw length if that screw would be placed up until exactly where the drill is at that moment. After finishing the drilling action, the drill is pulled out of the bone 20. Based on the bone density heatmap 33 and the available implants, a visualisation of the available implants, here referred to as implant overlay 37, indicating recommended screw length(s) by means of one or more chevrons 37 on the drill path which indicate where the tip of the screw would end up if a screw of that particular length would be placed, is overlayed on top of the bone density heatmap 33, and a suggestion is made for the implant to be selected. These recommendations are selected from the available screws and are based on the cortices 21 detected on the basis of the estimated bone structure. The deepest drilling point is also converted to the corresponding screw to show the maximal possible screw that would fit the hole. The displayed information can be used to select an implant length and an implant type. The selection of the most suitable implant is not only to be based on the implant length, but can also be based on other parameters like the pitch or the size of the threads of the implant. The user interface may also be configured such that no implant is suggested and that only a visual indication of the depth of dense bone material first contacted by the drill bit, to the depth of the deepest dense bone material is provided.

Next to the bone density heatmap 33 and the suggested implant lengths displayed on the visual display 31 of the user interface 30, other parameters are displayed as well. Firstly, the different possible implants, such as implant types and diameters, are displayed in an implant option section 32. The live depth of the bore is displayed based on the distance measurement and the instrument parameters. A visual warning indicator 36 may light up to indicate a real-time drilling risk parameter that relates to risks such as bluntness of the drill bit 17 and excessive force on the drill bit 17 when a predetined threshold is surpassed. The visual warning indicator 36 may be accompanied by an audible warning signal when a further threshold is surpassed. The plate 34 that is used in combination with the screw 39 is visualised together with the screw 39, especially the head of the screw. That is, the implant plate 34 and bone screw 39 are shown on scale as an overlay over the density map 33. Further, based on the bone structure and especially the cortices 21, an overall bone quality indication 35 can be displayed as a numerical value. Previous heatmaps are shown below the current heatmap 33 for comparison. The hardware device status 40, in terms of for instance battery level and connectivity, is also shown. Displaying the implants for selection helps the user to correctly assess the appropriate screw length. The user interface 30 can be shown on any suitable screen.

The displayed information is the result of processing of the data using algorithms, the two sources of this data are the signals originating from the sensor unit 11 and the instrument set parameters.

The signals from the sensor unit 11, originating from the distance sensors and the strain gauges, contain information about the position of, and forces acting on, the drill bit 17. The instrument set parameters are pieces of information about the used drill bit 17 and implants desired or available.

This is used to display accurate implant measurements. The user can configure this information before, during or after drilling, or (part of) this information will also be automatically determined from the sensor data.

The steps relating to the data processing and the calculation of the information to be displayed are shown in the flow diagram of figure 3. In a first step S10, the system is continuously gathering signals from the sensor unit 11 collecting parameters of the drilling action, the signals representing drilling distance and torgae and axial force on the drill bit 17. Next, in a second step S20, the system detects the start of the drilling action when the measured signals surpass, or conform to, predefined threshold values. In a third step S30, the measured signals are used to calculate the encountered bone density with the bone density calculating algorithm, discussed below with reference to figure 4, and calculate other parameters that are to be represented in the user interface 30. That is, the measured sensor data is continuously fed to the bone density calculating algorithm and its output is used to update the interface 30, specifically the density map 33 and the drill position. In addition, the data is monitored for anomalies and warning signals are provided in case of an anomaly. In a fourth step S40, when the drilling stops, the system detects the stop as the gathered signals stop exceeding the aforesaid threshold values or surpass other threshold values, and the system stops measuring. With the information gathered by the bone density calculating algorithm on bone density in step S30, a detection algorithm, discussed below with reference to figure 3, determines, in a fifth step S50, the implant lengths that properly match with the measured density heatmap 33. Extra indicators, such as a bone quality value 35, are determined as well. In a final step S60. both the density heatmap 33 and the implant lengths are displayed on the visual display 31 of the user interface system 30 alongside the extra indicators, as described above in relation to figure 2. That is, the implants lengths are displayed as an implant overlay 37 over the bone density heatmap 33 in the form of chevrons 37 on top of the bone density heatmap 33 with the implant lengths numerically displayed underneath with implant digits 38. This way, the user is provided with useful information in a clear and convenient manner for efficiently selecting a proper bone screw 39.

With this invention a more accurate assessment of appropriate implant length can be obtained, as the sensor data can give sub-millimetre accurate readings of the depth, which can be converted to accurate implant length measurements. Bone structure and density also gives more quantitative information a surgeon can use to potentially use more or different types of implants. For example, a screw with larger threads might be used if a bone 20 is weak to achieve better fixation of the screw into the bone 20.

In the following, the bone density calculating algorithm used in the third step S30 is described with reference to figure 4. The bone density calculating algorithm comprises several substeps. At the start of the measurement, an empty bone density heatmap 33 is created in the first substep S31. Ina second substep S32, the drilling signals are received from the sensor unit 11. Upon receiving the signals, the signals are pre-processed using a low-pass filter and anomalies are rejected in a third substep S33. In a fourth substep S34, after those filtering steps, the samples are transformed into dynamic kernels, based on the measured distance, force and angular velocity. In a fifth substep

S35, the dynamic kernels are positioned at the distance position on the heatmap 33 that corresponds to the distance signal in the measurement. In a sixth substep S36, the dynamic kernel is summed with the current density map and the numerical values in the bone density heatmap 33 are updated. The seventh substep S37 comprises updating the visualisation of the bone density heatmap 33 and the location of the drill bit 17 on the user interface 30. If the measurement is not yet finished, substeps S32-S37 of the algorithm are repeated with the next set of drilling signals that are received. When the drilling is ended, the bone density heatmap 33 is saved to the memory of the user interface system in an eighth substep S38 and shown as a previous measurement on the user interface 30.

The detection algorithm used in the fifth step S50 to calculate implant lengths from the bone density heatmap 33, is described in the following with reference to figure 5. The detection algorithm comprises several substeps. In a first substep S51, the bone density heatmap 33 is loaded into the detection algorithm. Thereafter, in a second substep S52, using a dynamic threshold, the higher bone density values. corresponding to the cortices 21, are extracted from the bone density heatmap 33. In a third substep S53, the first point with a density value above the threshold and the last point with a density value above the threshold are determined. The distance between these two points is the total cortex-to-cortex length (C2C) representing the distance between the areas with cortical bone 22. In a fourth substep S54, the system checks if there are other areas present in the bone density heatmap 33 that have a density value above the threshold. If there are no other areas present, the algorithm will only perform one C2C measurement in substep S55B. However, when an extra area with a high density value is detected in the bone density heatmap 33, a second C2C measurement is performed in substep S55A, wherein the cortex-to-cortex length from the starting area with a density value above the threshold to the extra area with a density value above the threshold is measured. Next, in a sixth substep S56, an implant type is selected from the implant option menu 32 shown on the user interface 30 and the algorithm determines if length should be added to the C2C measurement or if a different starting point should be used. The C2C measurements are updated to the selected implant measurements. Finally, the detection algorithm gives the choice to round the implant measurements up and down to the available discrete implant lengths. If the choice for rounding is made, the system will, in substep 57B, show the discrete implant lengths for every implant measurement on the user interface 30. H the choice is made to do no rounding to the discrete available implant lengths, the implant measurements are directly shown on the visual display 31 in substep 57A. The implant lengths are indicated in the user interface 30 as an implant overlay 37 on the bone density heatmap 33 as chevrons 37 and numerically with implant digits 38 representing their length underneath the bone density heatmap 33, as described above in relation to figure 2. The detection algorithm is able to suggest a preferred implant or overlays multiple possible implant lengths on top of a single bone density heatmap 33. Multiple heatmaps 33 of respective subsequent drillings, each representing the bone density as a function of the bore depth, are shown alongside each other.

The drawings are illustrative of selected aspects of the present disclosure, and together with the description serve to explain principles and operation of methods, products, and systems embraced by the present disclosure.

It will be apparent to those skilled in the art that various modifications and variations may be made without departing from the spirit or scope of the invention. Since modifications combinations, subcombinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

Conclusions

1. A method for selecting an implant, such as a bone screw, to be placed in a bore in a bone, the method comprising the steps of: — providing a user interface system comprising a visual display; — providing in the system a bone property signal representing a mechanical property of the bone along the depth of the bore; — graphically displaying the bone property signal as a function of bore depth using the display of the user interface system; — providing in the system an implant property signal representing at least a length of at least one implant of a predetermined set of implants for selection for placement in the bore; — displaying, using the display of the user interface system, the implant property signal in visual relation to the graphically displayed bone property signal; — selecting, based on the displayed signals, one of the implants to be placed in the bore.

The method of claim 1, wherein the step of displaying the implant property signal comprises graphically displaying the length of the at least one implant of the set of implants along the drilling depth.

The method of claim 2, wherein the step of graphically displaying the length of the at least one implant of the set of implants comprises superimposing the length of the at least one implant together with the graphically displayed bone property signal.

A method according to any preceding claim, wherein the user interface system further comprises a processor, the method further comprising, with the aid of the processor, the steps of comparing the bone property signal with a predetermined threshold value, determining, based on the comparison between the bone property signal and the predetermined threshold value, a drilling depth at which the bone property signal exceeds the predetermined threshold value close to a deep end of the drilling, and selecting at least one implant to be proposed from the set of implants based on the determined drilling depth close to the deep end of the drilling and based on the lengths of the implants of the set of implants, the implant property signal representing at least the length of the at least one implant to be proposed.

A method according to claim 4, wherein the step of determining the drilling depth proximate the deep end of the drilling comprises detecting cortical bone closest to the deep end of the drilling based on the comparison between the bone property signal and the predetermined threshold value, wherein the at least one implant to be proposed is determined based on the depth of the detected cortical bone and the lengths of the implants for selection.

A method according to claim 4 or 5, wherein the processor detects the number of times the bone property signal exceeds the threshold value to determine the number of cortical bone areas drilled, preferably wherein the processor provides a signal when the number exceeds a predetermined value, the signal indicating that drilling is complete, and wherein the method further comprises the step of displaying the number, preferably as an integer, using the user interface system, and/or preventing the drilling machine from drilling further.

7. A method according to any preceding claim, wherein the step of graphically displaying the bone property signal comprises continuously updating the graphically displayed bone property signal in real time.

A method according to any preceding claim, comprising the steps of repeatedly providing in the system at least one real-time drilling risk parameter representative of a drilling-related risk during drilling of the borehole, such as drill bit bluntness, and, when the at least one drilling parameter exceeds a preset threshold, outputting a warning signal using the user interface system, preferably outputting an audible warning signal and/or indicating a visual warning signal using the user interface system.

9. A method according to any preceding claim, wherein the mechanical property of the bone is the density of the bone.

IO. A method according to any one of the preceding claims, wherein the bone property signal is graphically represented as a one-dimensional heat map.

A method according to any preceding claim, comprising the steps of determining a bone quality signal representing a quality of the bone based on the bone property signal, and displaying the bone quality signal using the user interface system.

A method according to the preceding claim, wherein the step of displaying the bone quality signal comprises displaying a numerical value indicative of the bone quality signal.

13. A method according to any preceding claim, comprising a step of measuring the drilling depth as a distance from a reference point.

A method according to any preceding claim, wherein the user interface system further comprises a processor, wherein the step of providing the bone property signal comprises providing drilling signals into the system representing at least a drilling distance and at least one or both of an axial drilling force and a drilling torque during drilling of the bore, and determining the bone property signal using the processor based on the drilling signals.

15. A method as claimed in any preceding claim, comprising the steps of providing in the system a drilling deviation detection signal representing at least one or both of a lateral drilling force and a drilling direction during drilling of the bore, and indicating the drilling deviation detection signal using the user interface system.

A method according to any preceding claim, wherein a prior bone property signal representing a mechanical bone property along the depth of another bore is graphically displayed as a function of bore depth using the display of the user interface system alongside the graphically displayed current bone property signal.

17. A system for selecting an implant to be placed in a bore in a bone, the system comprising: — at least one sensor adapted to provide at least one signal for determining a depth of the bore and for determining a mechanical property of the bone along the depth of the bore; — a processor adapted to receive the at least one signal from the at least one sensor and adapted to determine, based on the at least one signal, a depth of the bore and a mechanical property of the bone along the depth of the bore, the processor further adapted to provide a bone property signal representing the mechanical property of the bone along the depth of the bore; — a user interface system comprising a visual display and configured to receive the bone property signal and an implant property signal representing at least a length of at least one implant of a predetermined set of implants for selection for placement in the bore, the user interface system configured, using the display, to graphically display the bone property signal as a function of bore depth and to display the implant property signal in visual relation to the graphically displayed bone property signal.

The system of claim 17, wherein the system comprises a drill and at least one of a drilling unit and a drilling machine for driving the drill into the bone, the drilling unit comprising a component housing and the drill.

19. A system as claimed in claim 18, wherein the at least one sensor is disposed in the one of the drilling unit and the drilling machine.

20. A system as claimed in claim 17 or 18, wherein the at least one sensor comprises a strain gauge mounted in and/or on the drilling unit or on a drive shaft of the drilling machine and adapted to produce a signal representing a force applied to the drilling unit during drilling.

The system of claim 18, 19, or 20, wherein the at least one sensor comprises a non-contact distance sensor configured to produce a signal representing a distance between the sensor and a reference point on the system during drilling, the distance representing the penetration depth of the drill into the bone.

22. A system as claimed in at least claim 20, wherein a plurality of strain gauges are mounted on the drill and are arranged to produce signals representing an axial force and/or torque applied to the drill.

23. System according to any of the preceding claims 18 - 22, wherein the processor is arranged in the drilling unit.

24. System according to any of the preceding claims 18 - 23, wherein a power source, such as a battery, for powering the at least one sensor is arranged in the drilling unit.

25. System according to any of the preceding claims 18 - 24, wherein the processor is adapted to communicate wirelessly.