Patent Description:
The present disclosure relates to a method and system for configuring a surgical tool during surgery.

It is important to accurately position surgical tools during surgery to allow the most effective treatment. One example includes surgery in relation to bones and joints, such as knee and hip replacement surgery. This may involve cutting, or otherwise shaping, bone and cartilage of the patient and securing implantable components thereto.

This requires the surgical tools to be accurately configured relative to the patient such that the surgical tool can operate in accordance with the surgical plan. This may involve apparatus and systems that assist the surgeon to guide the surgical tool to the desired position.

As an example, a positioning guide may be placed relative to anatomical features of the patient. Anatomical features may include portions of the surface of the bone, cartilage and soft tissue constructs. The surgeon may then position surgical tools relative to the positioning guide. The positioning guide may then assist a blade to cut the bone, assist drilling into the bone, assist insertion of pins into the bone, and/or assist positioning and securing an implant to the bone. However, a positioning guide needs to be made for a specific patient before surgery and may be limited to guiding a single surgical tool to a single configuration.

An alternative may be a re-usable instrument with settings that are not patient specific, such as an intramedullary rod to reference distance femoral cut on the femur.

Therefore, such known methods and systems for configuring surgical tools would require the desired configuration of the surgical tool known in advance of surgery so that a positioning guide may be manufactured. This reduces the flexibility, such as in cases where the desired configuration may not be known until shortly before surgery.

<CIT> discloses a guidance system which can be used by a surgeon in situations where a patient has not already undergone surgery to have an implant placed within the body. <CIT> discloses an image guided surgery system to enable a surgeon to move a surgical tool into a desired position relative to a body part. <CIT> discloses a method of performing hip surgery with a robotic guided system on a patient with femoral acetabular impingement. <CIT> discloses a system for guiding resurfacing operations on a portion of a joint of a bone using a guide with actuators (motors) controlled by a computer to position a cutting tool relative to a bone so that the bone surface can be cut in a flexible and accurate manner. <CIT> discloses an instrument for treating tissue during a medical procedure. <CIT> discloses a method for navigated placement of bone engaging elements, such as support pins used to support a cutting block on a bone for resection.

In the present description the term "position" with reference to a position of an element may include a position of the element in two, or three, dimensional space and may also include the orientation of the element.

A first aspect of the invention, as defined in claim <NUM>, relates to a method for configuring a bone preparation tool in relation to an anatomical feature of a bone, the method comprising:.

Specific embodiments are set forth in the dependent claims.

A second aspect of the invention, as defined in claim <NUM>, relates to software that, when installed on a computer, causes the computer to perform the method described above.

A third aspect of the invention, as defined in claim <NUM>, relates to a system for configuring a bone preparation tool in relation to an anatomical feature of a bone, the system comprising a laser range finding device, the laser range finding device comprising:.

characterised in that the system comprises
a processor.

Examples of the present disclosure will be described with reference to:.

<FIG> illustrates a system <NUM> for configuring a surgical tool <NUM> in relation to an anatomical feature <NUM>, where a reference feature, in this example a tool interface <NUM>, is fixed in relation to the anatomical feature <NUM>. A sensor system <NUM> detects the anatomical feature <NUM> and the tool interface <NUM>, which in turn sends sensor data to be received by an input port <NUM> of the system <NUM>.

The system <NUM> includes a processing device <NUM> having a processor to determine spatial data <NUM> indicative of a position of the anatomical feature <NUM> and a position of the tool interface <NUM> based on the received sensor data. The processing device <NUM> also determines a first desired spatial configuration <NUM> of the surgical tool <NUM> in relation to the tool interface <NUM> based on the spatial data <NUM> and a second desired spatial configuration <NUM> of the surgical tool <NUM> in relation to the anatomical feature <NUM>. The processing device <NUM> may send an output signal via output port <NUM> to a surgical tool apparatus <NUM> that positions the surgical tool <NUM>.

There is also disclosed a method <NUM> of configuring a surgical tool <NUM> in relation to an anatomical feature <NUM>. The method <NUM> may be performed by a processor of the processing device <NUM> and includes determining <NUM> spatial data <NUM> indicative of a position of the anatomical feature <NUM> and a position of the tool interface <NUM>. The method <NUM> further includes determining <NUM> a first desired spatial configuration of the surgical tool <NUM> in relation to the tool interface <NUM>. The first desired spatial configuration may be based on the spatial data (representative of positions of the anatomical feature <NUM> and the tool interface <NUM>) and a second desired spatial configuration of the surgical tool in relation to the anatomical feature.

Since the method determines the first desired spatial configuration in relation to the tool interface <NUM>, and the tool interface is fixed to the anatomical feature <NUM>, the result may be more accurate and less complex than other methods. For example, the disclosed method <NUM> may be more accurate that methods that are based on determinations of absolute positions of the anatomical feature <NUM> within an operation theatre and positioning the surgical tool <NUM> with reference to the absolute position of the surgical tool <NUM> in the operation theatre.

While some examples in this disclosure relate to determining the position of the tool interface <NUM>, it is to be understood that equally and more generally, processing device <NUM> may determine spatial data <NUM> indicative of a position of the anatomical feature <NUM> and a position of a reference feature, such as a cartilage defect or a bone feature, such as a medial epicondyle. The reference feature is also fixed in relation to the anatomical feature <NUM> and may be a pre-defined fixed reference feature, such as a bone feature or patient specific cartilage defect selected by an operator, doctor or surgeon.

An example of a process of replacing a joint of a patient using the method <NUM> and system <NUM> will now be described. This includes surgery planning followed by a surgery where the method <NUM> is employed.

A surgical plan may include shaping the anatomical feature <NUM> so that it is suitable for receiving an implant <NUM>. Importantly, the result of shaping of the anatomical feature <NUM> should be relative to the anatomical feature <NUM>. <FIG> illustrates an example of proposed shaping of the anatomical feature <NUM> to achieve a desired geometry (which in this case is shaping an end portion of a femur bone). The proposed shaping includes cutting the bone <NUM> along line <NUM> (which may be representative of a plane in three dimensions) to provide a shaped anatomical feature <NUM> as illustrated in <FIG>. After proposed cutting, and any other preparation work to achieve the desired geometry, the anatomical feature <NUM> may receive an implant <NUM> such as parts of an artificial joint as illustrated in <FIG>.

To improve the likelihood of successful surgery, it is desirable to have an accurately defined cut line <NUM> or plane relative to the anatomical features <NUM>. The cut line <NUM> or cutting plane may correspond to the desired shaped surfaces of the anatomical feature <NUM>. It is to be appreciated that in some examples, this may involve multiple cut lines <NUM> or planes and may further include limitations on how the cut is made, such as the length, the orientation, the type of tool, etc..

In the example of <FIG>, the cut line <NUM> may corresponds to the desired shape of the anatomical feature <NUM> (or an offset thereof). Furthermore, the cut line <NUM> corresponds to the desired path for the surgical tool <NUM> (or an offset thereof). That is, to achieve the desired shape for the anatomical feature <NUM>, the surgical tool <NUM> should be configured at relative to the anatomical feature <NUM> so that the working portion of the surgical tool <NUM> is on (or movable along) the cut line <NUM>. This is illustrated in this example with the second desired spatial configuration <NUM> of the surgical tool <NUM> relative to the anatomical feature <NUM> that includes a position <NUM> (at a displacement <NUM> from a reference location <NUM> of the anatomical feature <NUM>) and a second cutting angle <NUM> (from a reference axis <NUM>) that corresponds to the cut line <NUM>.

It is to be appreciated that the second desired spatial configuration <NUM> of the surgical tool <NUM> may be expressed in a variety of ways. For example, defining the cut line <NUM> may include specifying an angle and one position (of an infinite number) that falls on the line. Alternatively, the line <NUM> may be defined by specifying two positions, where the line <NUM> is determined as a straight line that passes through the two specified positions. In another example, the second desired spatial configuration may include a plane, which is defined by specifying three positions that the plane passes through. It is also to be appreciated difference coordinate systems may be used, such as polar coordinates, Cartesian coordinates, etc..

Determining <NUM> the second desired spatial configuration <NUM> may be performed during the planning stages of the surgery. As noted above, the second desired spatial configuration <NUM> is generally dictated by the desired resultant shape of the anatomical feature <NUM>. The desired shape of the anatomical feature <NUM>, in turn depends on a variety of factors including the type and shape of the implant <NUM>, the physiological characteristics of the patient, and other characteristics of the patient. Other characteristics of the patient may include the types of physical activity that the patient is likely to perform, such a running, playing golf, etc..

In one example, the implant (such as a replacement joint) may be tailored to a patient's other characteristics. For example, a person who is expected to have high levels of walking, jogging or even running, may have a particular replacement joint that is suitable for his or her needs. This may also include having a desired shape of the anatomical feature <NUM> that would be suitable for the particular replacement joint and/or the expected level of activity.

The present system <NUM> and method <NUM> may be suitable for replacement surgery with personalised orthopaedics. Such personalised orthopaedics may include treatment involving dynamic anatomic models and simulations thereof. In these systems, personal anatomic information of a patient is collected, such as those derived from medical imaging data such as CT scan (X-ray computed tomography) or MRI (magnetic resonance imaging). The information is then sent to a processor to build three dimensional computer models of the individual's joint. The computer models that are used may undergo dynamic simulations of the joint. This may include simulations with normal activities, such as walking, standing and sitting. It may also include dynamic simulations that may be characteristic of the patient, for example a patient who plays golf or tennis. Such simulations may allow identification of particular stresses and wear on the anatomy or type of implant. It may also allow simulation of other performance characteristics of the joint as well as assisting optimisation of the joint. The simulation may therefore assist in developing a tailored artificial joint for the patient, which may determine <NUM> a particular second spatial configuration <NUM> for the surgical tool <NUM> in relation to the anatomical features <NUM>.

Examples of dynamic anatomical models include the Optimized Ortho hip product called Corin OPS (Corin Optimized Positioning System) those described in International Publication Numbers <CIT> (<CIT>) in the name of Optimized Ortho Pty Ltd. An example of a knee product is PREKS (Pre-Operative Knee Analysis Report). A feature of the PREKS Report is the DKS (Dynamic Knee Score).

After determining the second desired spatial configuration for the surgical tool <NUM> in relation to the anatomical feature <NUM>, the surgeon may proceed with performing surgery. However, in known systems there may be difficulties in configuring a surgical tool <NUM> with direct relation to an anatomical feature <NUM>, or using the anatomical feature <NUM> directly as a reference or indexing surface. For example, the anatomical feature <NUM> may be obscured by other tissue making it difficult to observe the anatomical feature <NUM> and use it as a point of reference. The present system <NUM> and method <NUM> may ameliorate these difficulties by providing an alternative reference to the surgical tool <NUM>.

In surgery, tissue may be cut so that part of the anatomical feature <NUM> is exposed. A tool interface <NUM> is then fixed in relation to the anatomical feature <NUM> of the patient. The tool interface <NUM> may, for example, include a pin or screw that is secured to the anatomical feature <NUM>. This may be facilitated by a surgeon drilling into the anatomical feature <NUM> to receive fasteners fixing the tool interface <NUM>. Referring to the example in <FIG>, the tool interface <NUM> is fixed to a minor portion <NUM> of the anatomical feature <NUM> that will be cut off a main portion <NUM> of the anatomical feature <NUM>. That is, the minor portion <NUM> will be discarded after the surgery and therefore drilling or otherwise securing the tool interface <NUM> into the minor portion <NUM> may not affect the remaining main portion <NUM> of the anatomical feature <NUM>.

After the tool interface <NUM> is fixed to the anatomical feature <NUM>, the respective positions of the tool interface <NUM> and anatomical features <NUM> are determined <NUM>. This may be important as the actual position (including orientation) may be different to the intended position for the tool interface <NUM> that the surgeon had planned. For example, it may be difficult for a surgeon to precisely position and fix the tool interface <NUM> to the minor portion <NUM>. Factors such as obstruction by other human tissue, inaccuracies in tools, errors caused by human factors of the surgeon, etc. may result in the surgeon positioning the tool interface <NUM> at a position that was not originally intended during surgery planning. Alternatively, the surgeon may discover during surgery that there is damage to parts of the anatomical feature <NUM> where the tool interface was planned to be fixed. As a consequence the tool interface <NUM> had to be fixed to another position on the anatomical feature <NUM>.

To determine <NUM> spatial data that is indicative of the position of the anatomical feature <NUM> and the position of the tool interface <NUM>, the sensor system <NUM> performs a scan of the anatomical feature <NUM> and tool interface <NUM> as shown in <FIG>. The sensor system <NUM> sends the respective sensor data to be received by the input port <NUM>.

In some examples, the spatial data may include at least part of the sensor data. In other forms, the sensor data is used to determine the spatial data. Spatial data may include may forms, and in one example sensor data from the scan may be represented by a 3D point cloud showing spatial information of the detected area of the sensor system <NUM>.

<FIG> shows a representation of a 3D point cloud generated from sensor data received from the sensor system <NUM> that scanned the anatomical feature <NUM> and tool interface shown in <FIG>. From the 3D point cloud, the position of the anatomical features <NUM> and the tool interface <NUM> may be determined. In one example, a feature extraction algorithm may be used to determine the anatomical feature <NUM> and the tool interface <NUM> in the 3D point cloud. Once these are identified, the respective positions of the anatomical feature (such as position of reference position <NUM>) and the tool interface <NUM> may be determined.

In another example, processor <NUM> determines the position of the anatomical features <NUM> based on medical imaging data, such as CT or MRI images. Processor <NUM> analyses the medical imaging data and constructs a 3D segmented mesh that represents the imaging data. However, the reference feature <NUM> is applied during surgery, that is, after the medical imaging has been performed. As a result, the reference feature <NUM> is not visible in the medical imaging. The aim is to use the medical imaging and the derived 3D mesh model as an accurate representation of the anatomical features and then use the surface laser scan to align the actual anatomical features in front of the surgeon with the model. Since the reference feature <NUM> is now applied, this alignment step can provide the relative position of the reference feature in the 3D mesh model. In other words processor <NUM> determines the scanned position of the reference feature, such as an alignment array or other reference tool by calculating a best fit convergence between the points within the laser scan and the points generated within the 3D segmented mesh (derived from the medical images).

<FIG> illustrates a 3D mesh model <NUM> to assist with the best fit convergence the 3D segmented mesh is post processed using the following techniques.

In one example, there is a default position defined for the reference array and the processor <NUM> performs the following steps:.

The transformation matrix may have the following form:.

One aspect that may reduce the accuracy of alignment between the 3D mesh model from the medical imaging and the surface scan may be the presence of soft tissue on the bone <NUM>. While the bone is accurately represented by a CT image, the soft tissue is transparent to X-Ray waves and therefore causes little to no effect in the CT image. However, the soft tissue does reflect the laser beam <NUM>' which may result in a discrepancy between the laser scan and the 3D mesh model. In other words, the different wavelengths of radiation used for creating the 3D mesh model and for generating the surface scan may lead to different kinds of tissues being imaged and included.

In order to increase the accuracy of the alignment, processor <NUM> may exclude regions of the 3D mesh model from the alignment process. There are regions with both the distal femur and proximal tibia where soft tissue is most likely to be present, examples of which include the tibia spline. <FIG> illustrates an example area <NUM> in the PCL attachment that is excluded from the alignment process.

These areas can be identified within the 3D segmented mesh and tagged to be included or excluded during the alignment process. <FIG> shows a graphical representation of the tags within the distal femur where the faces around the pcl attachment have be tagged to exclude (non-confident or potentially inaccurate regions) and the areas around the distal and anterior regions including osteophytes have been tagged to include (confident or potentially highly accurate regions). Processor <NUM> may perform the alignment only on the confident regions or only on the regions that have not been excluded. Processor <NUM> may also apply a small weighting factor to non-confident regions (which could be zero) and/or a large weighting factor to confident regions.

Processor <NUM> may create a number of morphed surrogate model in order to enhance the alignment process when using CT images. The morphed models may be created using the following steps:.

<FIG> illustrates the original, a joint space morph and troch morph model, respectively.

After the morphing is performed, processor <NUM> performs the alignment process. <FIG> illustrates an initial scan <NUM> created within "camera space". The point on normal direction of each target is recorded relative to the same co-ordinate system of the scan as shown in <FIG>.

<FIG> illustrate how the scan and targets, respectively, are transformed relative to the default array position. <FIG> shows the <NUM>,<NUM> nodes of the scan while <FIG> shows the <NUM>,<NUM> nodes of the 3D mesh model. In this example none of the connect regions are filtered out and the scan is limited to a silhouette of the 3D segmented mesh relative to the co-ordinate system within the pre-operative plan.

<FIG> illustrate an iterative alignment process. It can be seen that it <FIG> there is some misalignment at points <NUM>, <NUM>, <NUM> and <NUM> while in <FIG> the alignment of those points is improved. The iterative alignment process is performed between cloned copies of the scan and each of the surrogate models. The iterative alignment process may stop iterating once a "best fit" based on mean deviation has been achieved.

The alignment between each of the surrogate models and the 3D segmented mesh is analysed by processor <NUM> using the following process:.

In <FIG> the representation is a two dimensional representation of points in a 3D point cloud. It is to be appreciated that the sensor system <NUM> may also provide sensor data indicative of a range of one or more of the points. Range information may also be used to assist feature extraction and/or determination of the respective positions of the anatomical feature <NUM> and tool interface <NUM> as described further below. In other words, the 3D point cloud generally comprises points that cover the entire viewing area including the theatre table, the floor or other equipment, such as lights. For illustrative purposes <FIG> comprises only those points that are within a small distance from the bone surface. For example, the processing device <NUM> may determine the maximum measured distance and the minimum measured distance in the point cloud. Processing device <NUM> may then step through the distances until the shape of the marker <NUM> can be detected using pattern matching. Processing device <NUM> may then use those points that are within a set distance, such as <NUM>, from the distance of the marker <NUM>. These are the points that are shown in <FIG>.

It is to be appreciated that the relative position of the anatomical feature <NUM> to the tool interface <NUM> may also be determined from the sensor data. Referring to <FIG>, relative position <NUM> may be the distance and orientation between the tool interface <NUM> and a reference point <NUM> of the anatomical feature <NUM>.

In the example above, spatial data is in the form of a 3D point cloud. Other forms of spatial data may include digital images (including stereoscopic images), position data on absolute positions of the anatomical feature <NUM> and tool interface <NUM>, relative position of the anatomical feature <NUM> and the tool interface <NUM>, etc. In turn, these may be represented in various coordinates systems, including those described above.

Importantly, the spatial data <NUM> provides information of the relative position <NUM> of the tool interface <NUM> and the anatomical feature <NUM> which can then be used to assist configuring the surgical tool <NUM> to the second desired spatial configuration discussed below.

The next step is to determine <NUM> a first desired spatial configuration <NUM> of the surgical tool <NUM> in relation to the tool interface <NUM> based on spatial data <NUM> and the second desired spatial configuration <NUM>. An example will now be described with reference to <FIG> that shows a surgical tool <NUM> cutting into the anatomical feature <NUM>.

The spatial data <NUM> may be used to derive the relative position <NUM> between the tool interface <NUM> and the reference point <NUM> of the anatomical feature <NUM>. The second desired spatial configuration <NUM>, including the cut line <NUM>, may be defined by point <NUM> that is displaced <NUM> from the reference point <NUM>. The processor may then apply known mathematical equations (such as trigonometric functions) to determine a first desired spatial configuration <NUM> of the surgical tool <NUM> (relative to the tool interface <NUM>) that would configure the surgical tool <NUM> to be along cut line <NUM>. The determined first desired spatial configuration <NUM> may be in the form of a vector <NUM> from the tool interface <NUM> to the surgical tool <NUM> and a first cutting angle <NUM> for the surgical tool <NUM>.

The first desired spatial configuration <NUM> of the surgical tool <NUM> will configure the surgical tool <NUM> along the cut line <NUM>. That is, configuring the surgical tool <NUM> in the same, or similar corresponding configuration, had the surgical tool been configured according to the second desired spatial configuration <NUM> (which would also configure the surgical tool <NUM> along cut line <NUM>).

The dynamic model that is used to determine the second desired spatial configuration <NUM> may be based on a model coordinate system that can be arbitrary in relation to the anatomical feature. For example, the model coordinate system may have an x-axis that is identical to the longitudinal axis of the bone <NUM> and the origin of the coordinate system may be on an arbitrary point on that axis. The z-axis and y-axis are then orthogonal to the x-axis up to an arbitrary rotation around the x-axis. The second desired spatial configuration is then defined in relation to this model coordinate system with a desired relation to the anatomical feature <NUM>. When the position of the tool interface <NUM> is determined, processing device <NUM> determines a transformation of the model coordinate system to the position of the tool interface <NUM>. The same transformation can then be applied to the second desired spatial configuration to determine the first desired spatial configuration of the tool in relation to the tool interface. This may include multiplying the coordinates of the second spatial configuration by rotation matrices to rotate around respective coordinate axis: <MAT> <MAT> <MAT>.

The system <NUM> may provide an output signal, via output port <NUM>, to set the surgical tool <NUM> to the first spatial configuration <NUM>. The tool interface <NUM> may be interfaced with the surgical tool apparatus <NUM> to allow the surgical tool apparatus <NUM> to have an accurate reference with respect to the tool interface <NUM>. Thus the surgical tool <NUM> (via the surgical tool apparatus) can be accurately configured relative to the tool interface <NUM>.

In one example, the surgical tool apparatus <NUM> may include a robotic arm <NUM> having the surgical tool <NUM>. The robotic arm <NUM> may include actuators to displace and orientate the surgical tool <NUM> in accordance with the output signal from the output port <NUM> such that the surgical tool is in the first spatial configuration <NUM> as illustrated in <FIG>.

Alternatively, the surgical tool apparatus <NUM> may include adjustable mechanisms, such as guides and/or jigs to assist configuring the surgical tool <NUM> in relation to the tool interface <NUM>. In one alternative, the output signal may provide visual indicia for the surgeon so that the surgeon can make appropriate adjustments to the surgical tool apparatus <NUM> to configure surgical tool <NUM>.

After the surgical tool <NUM> shapes the anatomical feature <NUM>, such as making a cut along cut line <NUM> to provide the major portion <NUM>, it may be desirable to verify the that the surface of the anatomical feature <NUM> is shaped to the desired shape.

<FIG> illustrates a major portion <NUM> of the anatomical feature <NUM> having a shaped end <NUM>. The method may include subsequently performing another scan of the anatomical feature <NUM> with the sensor system <NUM>, wherein sensor data may be sent to determine spatial data which in turn allows determination <NUM> of the result of applying the surgical tool <NUM>. This may be similar to step <NUM>, although the spatial data in this instance may not include position data of the tool interface <NUM> which may have been removed with the minor portion <NUM>. In one example, a 3D point cloud of the major portion <NUM> may be used to determine the result of the shaped major portion. This result may be compared with the desired geometry of the anatomical feature to verify the result of applying the surgical tool <NUM>. In one example, this may include determining the position of the shaped end <NUM>. This may include determining a surface angle <NUM> relative to the reference axis <NUM>.

The method may also include verifying the position of the implant <NUM> as shown in <FIG>. After verifying the surfaces of the anatomical feature <NUM> is shaped as desired to receive the implant <NUM> the surgeon may then secure the implant <NUM>, such as parts of a replacement joint, to the anatomical feature <NUM>. The sensor system <NUM> may then perform a further scan, so that the processor may determine <NUM> a position of an implant in relation to the anatomical feature <NUM>. This step is similar to the step of determining spatial data <NUM> described above, with the exception of determining the position of an implant <NUM> instead of the tool interface <NUM>. In one example, this includes determining <NUM> the position of the implant <NUM> relative to the shaped end <NUM>. This may include determining a surface angle <NUM> of the implant <NUM> relative to the reference axis <NUM>. The surface angle <NUM> of the implant <NUM> may be compared to the surface angle <NUM> of the shaped end <NUM> to validate correct positioning of the implant <NUM>.

<FIG> illustrate an alternative where a marker <NUM> is used to assist in determining the position of the tool interface <NUM>.

The marker <NUM> may be constructed with material that can be detected by the sensor system <NUM>. The marker <NUM> may include distinctive features that can assist detection. In the example illustrated in <FIG> a distinctive feature is the crucifix shape <NUM> of an end of the marker. In one alternative, the marker may include distinct features such as shapes or patterns, for example shape <NUM>, <NUM> positioned at extremities of the crucifix <NUM>. In some other alternatives, the marker <NUM> may be made of different types of materials to provide distinctive features, where one material may be easily contrast and differentiable to another type of material. Such distinctive features may assist in detection of the marker <NUM> as well as determining information such as position, including orientation of the marker <NUM>. This may be enhanced by selectively placing distinctive features on the marker <NUM> such that detection of particular distinctive features by the sensor system <NUM> may allow the processor to determine a unique position, including orientation, of the marker <NUM>.

The marker <NUM> may be a device that can be engaged with the tool interface <NUM>. For example, the tool interface <NUM> may include a socket to receive a corresponding spigot of the marker <NUM>. Alternative forms of engagement between the tool interface <NUM> and marker <NUM> may include dovetail joint, bayonet mount, T slot and key system, interference fit, etc. Since the relative position of the tool interface <NUM> and the marker <NUM> may be specified or predefined (such as from manufactured specifications), if the position of the marker <NUM> is determined, in a manner similar to step <NUM>, then the position of the tool interface <NUM> can also be determined.

Similarly, a marker <NUM> may also be used during the step <NUM> of determining the position of an implant <NUM>. In this case, the marker <NUM> may be interfaced with the implant <NUM> after which the sensor system <NUM> may scan for the anatomical feature <NUM> and marker <NUM> similar to step <NUM> described above.

Markers <NUM> may be advantageous in circumstances where the sensor system <NUM> has difficulties detecting the tool interface <NUM> or determining the position of the tool interface <NUM> is otherwise difficult. For example, the tool interface <NUM> may be small or outside a line-of-sight of the sensor system <NUM>.

The present disclosure may be applicable to a wide range of surgical applications. This may include orthopaedic applications, such as arthroplasty where anatomical features such as bone, cartilage and/or soft tissue constructs may need to be reshaped and/or removed. In one example, this may include joint replacement surgery including joints such as the knee, hip, shoulder and elbows. It is to be appreciated that systems and apparatus for performing such procedures may be modified and/or otherwise adapted with the presently disclosed method <NUM> and system <NUM>.

The surgical tool <NUM> may include a bone-preparation tool, such as a tool for cutting, drilling, reaming, machining, shaving and fracturing. An example includes a powered reciprocating saw blade. The saw blade may be guided by the surgical tool apparatus <NUM> such as from a robotic arm <NUM> that is actuated based on output signals from the processing device <NUM>. The surgical tool apparatus <NUM> may have a microcontroller that receives the output signals and, in turn, provides control signals to actuators of the robotic arm <NUM>.

The sensor system <NUM> may include a variety of sensor types suitable for detecting the position of the anatomical feature <NUM> and the tool interface <NUM>. In one example, the sensor system <NUM> includes a range finding device to provide sensor data, in the form of range finder data, to determine the range from the sensor system <NUM>. The range finding device may determine, for multiple points, a distance of the anatomical feature <NUM> and tool interface <NUM> to the position of the sensor system. An example includes a laser range finding device, that includes a steerable laser source <NUM>' to project laser light, at multiple points, towards the anatomical feature <NUM> and tool interface <NUM>. The reflected light may be detected by a light sensor (such as a photo detector <NUM>") and the time of flight of the light used to determine a respective distance. In other examples, the sensor system <NUM> may include one or more digital image sensors (e.g. digital cameras) to provide sensor data. In one example, a system of stereoscopic digital cameras may be used to provide sensor data that can provide data indicative of position of the anatomical feature and tool interface in captured images.

The tool interface <NUM> may be made of material suitable for surgery, such as <NUM> stainless steel and may contain a location feature for a pre-drilled hole, fixation pin holes and <NUM> geometrical features. Examples include the probe spheres by Bal-tec. The tool interface <NUM> may include a socket to receive a corresponding spigot of the surgical tool apparatus <NUM>. It is to be appreciated various ways of interfacing components may be used. Examples may include engagement using a dovetail joint, bayonet mount, T slot and key system, interference fit, etc. The tool interface <NUM> may be fixed to the anatomical features <NUM> by fasteners including pins and screws, adhesives, etc. It is to be appreciated that other suitable methods of fixing the tool interface <NUM> that is suitable for surgery may be used.

The processing device <NUM> includes a processor <NUM> connected to a program memory <NUM>, a data memory <NUM>, a communication port <NUM> and a user port <NUM>. The program memory <NUM> is a non-transitory computer readable medium, such as a hard drive, a solid state disk or CD-ROM. Software, that is, an executable program stored on program memory <NUM> causes the processor <NUM> to perform the method in <FIG>, that is, the method <NUM> of configuring a surgical tool <NUM> in relation to an anatomical feature <NUM>.

The processor <NUM> may then store spatial data <NUM>, sensor data (including range finder data), medical imaging data, data indicative of the first desired spatial configuration, data indicative of the second desired spatial configuration on data store <NUM>, such as on RAM or a processor register. Processor <NUM> may also send the determined first desired spatial configuration, in the form of output signal via communication port <NUM> to an output port <NUM>.

The processor <NUM> may receive data, such as sensor data, medical imaging data, data indicative of the first desired spatial configuration, data indicative of the second desired spatial configuration from data memory <NUM> as well as from the communications port <NUM> and the user port <NUM>, which is connected to a display <NUM> that shows a visual representation <NUM> of the spatial data <NUM> to a user <NUM>. In one example, the processor <NUM> receives sensor data from the sensor system <NUM> thorough the input port <NUM> and/or communications port <NUM>.

Although communications port <NUM> and user port <NUM> are shown as distinct entities, it is to be understood that any kind of data port may be used to receive data, such as a network connection, a memory interface, a pin of the chip package of processor <NUM>, or logical ports, such as IP sockets or parameters of functions stored on program memory <NUM> and executed by processor <NUM>. These parameters may be stored on data memory <NUM> and may be handled by-value or by-reference, that is, as a pointer, in the source code.

The processor <NUM> may receive data through all these interfaces, which includes memory access of volatile memory, such as cache or RAM, or non-volatile memory, such as an optical disk drive, hard disk drive, storage server or cloud storage. The processing device <NUM> may further be implemented within a cloud computing environment, such as a managed group of interconnected servers hosting a dynamic number of virtual machines.

Example methods for conversion between quaternions and Euler angles is described in "<NPL>, which is included herein by reference.

<FIG> illustrates example code for the determination of the rotation angle while <FIG> illustrates example code for creating a transformation from three spheres.

An example method for least squares fitting of data is described in: <NPL>.

<FIG> illustrates steps of a method for fitting a sphere to 3D Points. Given a set of points <MAT>, m ≥ <NUM> fit them with a sphere (x - a)<NUM> + ( y - b)<NUM> + (z - c)<NUM> = r<NUM> where (a, b, c) is the sphere center and r is the sphere radius. An assumption of this algorithm is that not all the points are coplanar. The energy function to be minimized is expression <NUM> where <MAT>. Taking the partial derivative with respect to r results in expression <NUM>.

Setting equal to zero yields expression <NUM>. The next step is taking the partial derivative with respect to a to obtain expression <NUM>, taking the partial derivative with respect to b to obtain expression <NUM> and taking the partial derivative with respect to c to obtain expression <NUM>.

Setting these three derivatives equal to zero yield expressions <NUM>, <NUM> and1118, respectively.

Replacing r by its equivalent from ∂E / ∂r = <NUM> and using ∂Li / ∂a = (a - xi) / Li, ∂Li / ∂b = (b - xi) / Li , ∂Li / ∂c = (c - xi) / Li, processing device <NUM> can process the three nonlinear equations <NUM>, <NUM> and <NUM> in <FIG> where the parameters are according to expression <NUM>.

Processing device <NUM> can apply a fixed point iteration to solving these equations a<NUM> = x , b<NUM> = y, c<NUM> = z and ai+<NUM> = F(ai,bi,ci), bi+<NUM> = G(ai,bi,ci) ci+<NUM> = H(ai,bi,ci).

An example method for sphere detection within the point cloud is provided in <FIG> and in: <NPL>.

Processing device <NUM> may perform an iterative closes point method (ICP) as shown as pseudo-code in <FIG> and is described in: Ronen Gvili, "Iterative Closest Point", http://www. il/∼dcor/Graphics/adv-slides/ICP. <FIG> illustrates example code for iterative closest point calculation.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the specific embodiments without departing from the scope as defined in the claims.

It should be understood that the techniques of the present disclosure might be implemented using a variety of technologies. For example, the methods described herein may be implemented by a series of computer executable instructions residing on a suitable computer readable medium. Suitable computer readable media may include volatile (e.g. RAM) and/or non-volatile (e.g. ROM, disk) memory, carrier waves and transmission media. Exemplary carrier waves may take the form of electrical, electromagnetic or optical signals conveying digital data steams along a local network or a publically accessible network such as the internet.

It should also be understood that, unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as "estimating" or "processing" or "computing" or "calculating", "optimizing" or "determining" or "displaying" or "maximising" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that processes and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claim 1:
A method for configuring a bone preparation tool (<NUM>) in relation to an anatomical feature (<NUM>) of a bone (<NUM>), the method comprising:
directing a laser light source (<NUM>') of a laser range finding device (<NUM>) towards the bone (<NUM>);
detecting, by a light sensor (<NUM>") of the laser range finding device (<NUM>), light reflected by the bone (<NUM>);
generating a 3D point cloud (<NUM>) based on the reflected light;
determining based on the 3D point cloud (<NUM>) spatial data indicative of a position of the anatomical feature (<NUM>) and of a position of a reference feature (<NUM>) that is fixed in relation to the anatomical feature (<NUM>);
aligning an anatomical model with the spatial data; and
transforming a model coordinate system of the anatomical model to the position of the reference feature (<NUM>) to determine a desired configuration angle of the bone preparation tool (<NUM>) in relation to the reference feature (<NUM>) based on:
the spatial data, and a desired preparation cutting angle of the bone (<NUM>) in relation to the anatomical feature (<NUM>) based on the anatomical model.