System and method for haptic control of surgical tool

Abstract

To provide a system and the like for haptic control of surgical tool.SOLUTION: A surgical system includes a surgical tool (36) associated with a virtual haptic interaction point (60) such that movement of the virtual haptic interaction point corresponds to movement of the surgical tool. The surgical system further includes a processing circuit (20) to establish a virtual entry boundary (50) and activate a haptic object (52), which constrains the surgical tool after the haptic interaction point crosses the virtual entry boundary.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Application No. 13 / 725,348, filed December 21, 2012, which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to the field of haptics, and more particularly to haptic control of surgical tools. [Background technology]

[0003] During computer-assisted surgery, surgeons may utilize haptic devices. "Haptics" refers to the sense of touch, and the field of haptics specifically relates to human-interactive devices that provide feedback to operators. Feedback can include tactile sensations, such as vibrations. Feedback can also include force on the user, such as a positive force or resistance to movement. A common use of haptics is to provide guidance and limitations to the device's operation to the user. For example, a haptic device is coupled to a surgical tool that the surgeon manipulates to perform surgery. The surgeon's manipulation of the surgical tool can be guided or limited using haptics, providing feedback to the surgeon during manipulation of the surgical tool.

[0004] Typically, before performing surgery using a haptic device, a surgical plan is developed. Because the surgical plan varies from patient to patient, the surgical system uses the surgical plan to guide and restrict the movement of surgical tools during surgery. Such control of the surgical tools helps protect the patient and assist the surgeon in carrying out the surgical plan.

[0005] Haptic devices used in surgery typically have at least two surgical modes. In a free mode, the surgeon has general freedom to manipulate a surgical tool coupled to the haptic device. In a haptic control mode, components of the surgical system (e.g., haptic objects) are activated to guide or constrain the movement of the surgical tool. The use of prior art haptic devices can be further enhanced by mechanisms that improve the transition between the free mode and the haptic control mode during surgery. Summary of the Invention

[0006] overview One embodiment of the present invention relates to a surgical system including a surgical tool associated with a virtual haptic interaction point, where movement of the virtual haptic interaction point corresponds to movement of the surgical tool, and further including processing circuitry configured to establish a virtual starting boundary and activate a haptic object configured to constrain the haptic interaction point after the haptic interaction point crosses the virtual starting boundary.

[0007] Another embodiment of the present invention relates to a method of using a surgical system, the method including providing a surgical tool and providing a virtual haptic interaction point, where movement of the virtual haptic interaction point corresponds to movement of the surgical tool, the method further including providing a virtual starting boundary and activating a haptic object configured to constrain the haptic interaction point after the haptic interaction point crosses the virtual starting boundary.

[0008] Yet another embodiment of the present invention relates to a computer-readable storage medium having instructions that, when executed by a processing circuit, aid in the planning or performance of a surgery, including instructions for associating a surgical tool with a virtual haptic interaction point such that movement of the virtual haptic interaction point corresponds to movement of the surgical tool, instructions for establishing a virtual start boundary and a virtual end boundary, wherein an activated haptic object is configured to constrain the surgical tool after the haptic interaction point crosses the virtual start boundary, and instructions for deactivating the haptic object after the haptic interaction point crosses the virtual end boundary.

[0009] Other example embodiments relate to other features and combinations of features as may be generally recited in the claims. [The present invention 1001] a surgical tool associated with a virtual haptic interaction point, wherein movement of the virtual haptic interaction point corresponds to movement of the surgical tool; a processing circuit configured to establish a virtual starting boundary and activate a haptic object, the activated haptic object configured to constrain the surgical tool after a haptic interaction point crosses the virtual starting boundary; A surgical system comprising: [The present invention 1002] The surgical system of the present invention 1001, wherein the processing circuit is further configured to establish a virtual end boundary and deactivate the tactile object after the tactile interaction point crosses the virtual end boundary. [The present invention 1003] The processing circuit is further configured to automatically correct the position of the surgical tool in response to a trigger when the tactile interaction point crosses the virtual starting boundary, in a surgical system of the present invention 1001. [The present invention 1004] The processing circuit is further configured to automatically correct the orientation of the surgical tool when triggered by the tactile interaction point crossing the virtual starting boundary, in a surgical system of the present invention 1001. [The present invention 1005] A surgical system of the present invention 1001, wherein the virtual starting boundary encloses a three-dimensional volume and is pill-shaped. [The present invention 1006] A surgical system of the present invention 1001, wherein the virtual starting boundary encloses a three-dimensional volume and has the shape of a partially excised tablet, and the cross section of the virtual starting boundary is fan-shaped. [The present invention 1007] A surgical system according to the present invention 1001, wherein the surgical tool is a spherical boring tool. [The present invention 1008] A surgical system of the present invention 1001, wherein the surgical tool is a sagittal saw. [The present invention 1009] The surgical system of the present invention 1001, wherein the tactile object is a straight line. [The present invention 1010] A surgical system according to the present invention 1001, wherein the tactile object is a plane. [The present invention 1011] A surgical system according to the present invention 1001, wherein the tactile object is a three-dimensional volume. [The present invention 1012] The surgical system of the present invention 1001 further includes an offset haptic object configured to be adjusted before or during surgery. [The present invention 1013] The surgical system of the present invention 1001 further comprising a safety mechanism configured to deactivate the haptic object. [The present invention 1014] The processing circuitry deactivating the haptic object upon the occurrence of an event; evaluating a plurality of conditions after the event has ended; The surgical system of the present invention 1001 is configured to reactivate the haptic object when the plurality of conditions are met. [The present invention 1015] providing a surgical tool; providing a virtual tactile interaction point, the movement of which corresponds to the movement of the surgical tool; providing a virtual starting boundary; and activating a haptic object configured to constrain the surgical tool after the haptic interaction point crosses the virtual starting boundary. A method of using a surgical system, comprising: [The present invention 1016] providing a virtual termination boundary; and deactivating the haptic object after the haptic interaction point crosses the virtual exit boundary. The method of the present invention 1015 further comprises: [The present invention 1017] The method of claim 1015, further comprising the step of automatically correcting the position of the surgical tool when triggered by the tactile interaction point crossing the virtual starting boundary. [The present invention 1018] The method of claim 1015, further comprising the step of automatically correcting the orientation of the surgical tool when triggered by the tactile interaction point crossing the virtual starting boundary. [The present invention 1019] The method of claim 1015, wherein the virtual starting boundary encloses a three-dimensional volume and is tablet-shaped. [The present invention 1020] The method of claim 1015, wherein the virtual starting boundary encloses a three-dimensional volume and has the shape of a partially excised tablet, and the cross section of the virtual starting boundary is fan-shaped. [The present invention 1021] The method of claim 1015, wherein the surgical tool is a spherical burr. [The present invention 1022] The method of claim 1015, wherein the surgical tool is a sagittal saw. [The present invention 1023] The method of the present invention 1015, wherein the tactile object is a straight line. [The present invention 1024] The method of claim 1015, wherein the tactile object is a plane. [The present invention 1025] The method of claim 1015, wherein the tactile object is a three-dimensional volume. [The present invention 1026] The method of claim 1015 further comprising providing an offset haptic object configured to be adjusted pre-operatively or intra-operatively. [The present invention 1027] deactivating the haptic object upon the occurrence of an event; evaluating a plurality of conditions after the event has ended; reactivating the haptic object if the plurality of conditions are met. The method of the present invention 1015 further comprises: [The present invention 1028] 1. A computer-readable storage medium having instructions that, when executed by a processing circuit, assist in the planning or performance of a surgical procedure, instructions to associate the surgical tool with the virtual haptic interaction point such that movement of the virtual haptic interaction point corresponds to movement of the surgical tool; instructions to establish a virtual beginning boundary and a virtual ending boundary; instructions to activate a haptic object, the activated haptic object configured to constrain the surgical tool after the haptic interaction point crosses the virtual starting boundary; and an instruction to deactivate the haptic object after the haptic interaction point crosses the virtual exit boundary; The recording medium comprising: [Brief explanation of the drawings]

[0010] The present disclosure will be better understood from the following detailed description when taken in conjunction with the accompanying drawings, in which like elements are designated with like reference numerals and in which: [Figure 1] FIG. 1 is a diagram illustrating a surgical system according to an exemplary embodiment. [Figure 2] 2A and 2B show an embodiment of a sagittal saw. [Figure 3A] 10A-10C illustrate a planned femoral modification according to an exemplary embodiment. [Figure 3B] 10A-10C illustrate a planned femoral modification according to an exemplary embodiment. [Figure 3C] 10A-10C illustrate a planned tibial correction according to an exemplary embodiment. [Figure 3D] 10A-10C illustrate a planned tibial correction according to an exemplary embodiment. [Figure 4] FIG. 4 illustrates a method of use of a surgical system, according to an exemplary embodiment. [Figure 5A] 10A-10C illustrate the initiation and termination of haptic control when the tool normal is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 5B] 10A-10C illustrate the initiation and termination of haptic control when the tool normal is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 5C] 10A-10C illustrate the initiation and termination of haptic control when the tool normal is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 5D] 10A-10C illustrate the initiation and termination of haptic control when the tool normal is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 5E] 10A-10C illustrate the initiation and termination of haptic control when the tool normal is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 6] 6A-6B are diagrams illustrating the haptic objects in FIGS. 5A-5E, according to an exemplary embodiment. [Figure 7] 7A-7B are diagrams illustrating offset haptic objects according to an exemplary embodiment. [Figure 8A] 10A-10C illustrate the initiation and termination of haptic control when the tool centerline is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 8B] 10A-10C illustrate the initiation and termination of haptic control when the tool centerline is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 8C] 10A-10C illustrate the initiation and termination of haptic control when the tool centerline is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 8D] 10A-10C illustrate the initiation and termination of haptic control when the tool centerline is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 8E] 10A-10C illustrate the initiation and termination of haptic control when the tool centerline is perpendicular to the haptic object, according to an exemplary embodiment. [Figure 9] 9A-9B are diagrams illustrating the haptic objects in FIGS. 8A-8E, according to an exemplary embodiment. [Figure 10] FIG. 10 illustrates another embodiment of an offset haptic object, according to an exemplary embodiment. [Figure 11A] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a line, according to an exemplary embodiment. [Figure 11B] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a line, according to an exemplary embodiment. [Figure 11C] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a line, according to an exemplary embodiment. [Figure 11D] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a line, according to an exemplary embodiment. [Figure 11E] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a line, according to an exemplary embodiment. [Figure 12] FIG. 12 illustrates various features of the surgical plan according to the embodiment shown in FIGS. 11A-11E. [Figure 13A] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a three-dimensional volume, according to an exemplary embodiment. [Figure 13B] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a three-dimensional volume, according to an exemplary embodiment. [Figure 13C] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a three-dimensional volume, according to an exemplary embodiment. [Figure 13D] 10A-10C illustrate the initiation and termination of haptic control when the haptic object is a three-dimensional volume, according to an exemplary embodiment. [Figure 14] FIG. 14 illustrates various features of the surgical plan according to the embodiment shown in FIGS. 13A-13D. [Figure 15] FIG. 15 illustrates the haptic recovery feature used when haptic control is released. [Figure 16] FIG. 16 is a diagram illustrating a starting boundary according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Before turning to the drawings, which describe exemplary embodiments in detail, it should be understood that the present invention is not limited to the content or methods described in the specification or illustrated in the drawings. Furthermore, the terminology used is for descriptive purposes only and is not intended to limit the present invention. For example, some of the drawings illustrate methods for initiating and terminating haptic control during a particular surgical procedure on a patient's knee. However, the haptic control described herein may be applied to haptic control of surgical tools during any type of surgical procedure on any part of a patient, such as the patient's shoulder, arm, elbow, hand, buttocks, leg, foot, neck, face, etc.

[0012] Examples of surgical systems 1, a surgical system 100 includes a navigation system 10, a computer 20, and a haptic device 30. The navigation system tracks the patient's bones and the surgical tools used during surgery, allowing the surgeon to visualize the bones and tools via a display device 24 and to have haptic control of a surgical tool 36 coupled to the haptic device 30.

[0013] The navigation system 10 may be any type of navigation system configured to track a patient's body and surgical tools during surgery. For example, the navigation system 10 may include a non-mechanical tracking system, a mechanical tracking system, or a combination of these systems. The navigation system 10 acquires the position and orientation (i.e., pose) of an object relative to a coordinate frame of reference. As the object moves within the coordinate frame of reference, the navigation system tracks the object's pose and detects the object's movement.

[0014] In one embodiment, the navigation system 10 includes a non-mechanical tracking system, as shown in FIG. 1 . The non-mechanical tracking system is an optical tracking system that includes a detection device 12 and a trackable portion (e.g., navigation marker 14). The trackable portion is disposed on the tracked object and is detectable by the detection device 12. In one embodiment, the detection device 12 includes a visible light detector, such as the Micron Tracker (Claron Technology, Toronto, Canada), that detects a pattern (e.g., a checkerboard pattern) on the trackable portion. In another embodiment, the detection device 12 includes a set of infrared-sensitive stereo cameras that can be installed in the operating room where the surgery will be performed. The trackable portion includes multiple markers that are attached to the tracked object in a secure and stable manner and have a known geometric relationship to the tracked object. As is well known, the trackable element may be active (e.g., a light emitting diode, LED) or passive (e.g., a reflective sphere, a checkerboard pattern), and may include a unique geometry (e.g., a unique geometric arrangement of markers). In particular, if active, the trackable element may include hardwired markers and a unique firing pattern.

[0015] During surgery, the detection device 12 detects the position of the trackable part, and the surgical system 100 (e.g., the detection device 12 using implantable electronics) calculates the pose of the tracked object based on the position of the trackable part, its inherent geometry, and the known geometric relationship between the tracked object. The navigation system 10 includes a trackable part for each object the user wishes to track, such as a navigation marker 14 located on the tibia 2, a navigation marker 16 located on the femur 4, a haptic device marker 18 (for tracking the global or macroscopic position of the haptic device 30), and an end-effector marker 19 (for tracking the tip of the haptic device 30).

[0016] Referring again to FIG. 1 , the surgical system 100 further includes processing circuitry, illustrated as computer 20. The processing circuitry includes a processor and a memory device. The processor may be a general-purpose processor, an Application Specific Integrated Circuit (ASIC), one or more Field Programmable Gate Arrays (FPGAs), a group of processing components, or any other suitable electronic processing component. The memory device (e.g., memory, memory unit, storage device, etc.) is one or more devices (e.g., RAM, ROM, flash memory, hard disk drive, etc.) for storing data and / or computer code for completing or facilitating the various processes and functions described herein. The memory device may be or include volatile or non-volatile memory. The memory device may store components such as databases, object code, scripts, or other types of information structures to support the various operations and information structures described herein. According to an exemplary embodiment, the memory device is communicatively coupled to the processor via the processing circuitry and includes computer code for performing (e.g., by the processing circuitry and / or the processor) one or more operations described herein.

[0017] The computer 20 is configured to be in communication with the navigation system 10 and the haptic device 30. Additionally, the computer 20 receives information related to the surgery and performs various functions for performing the surgery. For example, the computer 20 may include software necessary to perform functions related to image analysis, surgical planning, positioning, navigation, image guidance, and haptic guidance.

[0018] The haptic device 30 includes a base 32, a robotic arm 34, and a surgical tool 36 coupled to the robotic arm 34. The surgical tool may be any surgical tool connectable to the robotic arm 34. For example, in the embodiment shown in FIG. 1, the surgical tool 36 is a spherical burr. The surgical tool 36 may also be a sagittal saw 38 as shown in FIG. 2A or a sagittal saw 40 as shown in FIG. 2B. The blade 39 of the sagittal saw 38 is aligned parallel to the tool axis 42, while the blade 39 of the sagittal saw 40 is aligned perpendicular to the tool axis 42. A surgeon may select from the spherical burr, sagittal saw 38, sagittal saw 40, and other types of surgical tools depending on the type of bone modification (e.g., drilling, flat cut, curved edge, etc.) they wish to perform.

[0019] A surgeon interacts with the haptic device 30 to perform surgery on a patient. Generally, the haptic device 30 has two surgical modes. In the free mode, the surgeon has substantial freedom in manipulating the orientation of the surgical tool 36. In the haptic control mode, one or more haptic objects 52 are activated. The haptic objects 52 can constrain the surgical tool 36 as described in various embodiments herein.

[0020] Surgical planning Before a surgeon performs a surgery, a surgical plan is developed. The surgical plan is developed using a three-dimensional representation of the patient's anatomy, referred to herein as a virtual bone model 45 (see FIGS. 3A-3D). A "virtual bone model" may include virtual representations of cartilage and other tissues in addition to bone. Computer 20 receives images of the patient's anatomy to be operated on to obtain virtual bone model 45. The patient's anatomy may be scanned using known imaging techniques, such as CT, MRI, or ultrasound. The scan data is then segmented to obtain virtual bone model 45. For example, prior to surgery on a knee, a three-dimensional representation of the femur 4 and tibia 2 is created. Alternatively, virtual bone model 45 may be obtained by selecting a three-dimensional model from a database or library of bone models. In one embodiment, a user may select an appropriate model using input device 22. In another embodiment, computer 20 may be programmed to select an appropriate model based on images or other information provided about the patient. The bone model selected from the database is then modified based on the characteristics of the particular patient, resulting in a virtual bone model 45 that is used in the surgical planning and procedure described herein.

[0021] A surgeon can develop a surgical plan based on the virtual bone model 45. The surgical plan may include desired cuts, drilling, and other modifications to the patient's bone 44, which the surgeon makes using the surgical system 100. The modifications may be planned during surgery based on the shape of the parts to be connected to the bone. For example, the surgical plan may include planned modifications to the bones shown in FIGS. 3A-3D prior to performing a total knee replacement. FIGS. 3A and 3B show a virtual bone model 45 of a femur 4 including planned modifications to the femur 4, including an anterior cut 46, an anterior chamfer cut 92, a distal cut 84, a posterior chamfer cut 94, and a posterior cut 96. FIGS. 3C and 3D show a virtual bone model 45 of a tibia 2 including planned modifications to the tibia 2, including a tibial base cut 49, a wall cut 51, and a peg cut 53. The planned modification to the femur 4 shown in FIGS. 3A and 3B corresponds to a virtual component 66 (FIG. 6A) representing the part to be connected to the femur 4.

[0022] The surgical plan further includes one or more haptic objects 52 that aid the surgeon in executing the surgical plan by constraining the surgical tool 36 during surgery. The haptic object 52 may be formed in one, two, or three dimensions. For example, the haptic object may be a line ( FIG. 11A ), a plane ( FIG. 6B ), or a three-dimensional volume ( FIG. 13A ). The haptic object 52 may be curved, have a curved surface, or have any other shape. The haptic object 52 can be created to represent various desired outcomes of the movement of the surgical tool 36 during surgery. For example, a linear haptic object 52 can represent the trajectory of the surgical tool 36. A planar haptic object 52 can represent modifications, such as cuts, to be made on the surface of the bone 44. One or more boundaries in the three-dimensional haptic object can represent one or more modifications, such as cuts, to be made on the surface of the bone 44. Additionally, portions of the three-dimensional haptic object may correspond to portions of bone to be resected during surgery.

[0023] Prior to surgery, the patient's anatomy is positioned relative to the virtual bone model 45 of the patient's anatomy using known positioning techniques. One possible positioning technique is point-based positioning, as described in U.S. Patent No. 8,010,180, issued August 30, 2011, for "Tactile Guidance System and Method," which is incorporated herein by reference in its entirety. Alternatively, positioning may be 2D / 3D positioning using a portable radiographic device, as described in U.S. Patent Application No. 13 / 562,163, filed July 30, 2012, for "Radiographic Imaging Device," which is incorporated herein by reference in its entirety. Positioning the patient's anatomy enables precise navigation and haptic control during surgery. As the patient's anatomy moves during surgery, the surgical system 100 correspondingly moves the virtual bone model 45. Thus, the virtual bone model 45 corresponds to or is associated with the patient's actual (i.e., physical) anatomy. Similarly, any haptic object 52 created during surgical planning also moves relative to the patient's anatomy and corresponds to a location in real (i.e., physical) space. This location in physical space is referred to as an implementation boundary. For example, a linear haptic object 52 corresponds to a linear implementation boundary in physical space, a planar haptic object 52 corresponds to a planar implementation boundary in physical space, and a three-dimensional haptic object 52 corresponds to a three-dimensional volume in physical space.

[0024] The surgical system 100 also includes a virtual tool 47 (FIG. 5A) that is a virtual representation of the surgical tool 36. As the navigation system 10 tracks the surgical tool 36 during surgery, the virtual tool 47 moves relative to the surgical tool 36. The virtual tool 47 includes one or more haptic interaction points (HIPs) that represent and are associated with locations on the physical surgical tool 36. As described further below, the relationship between the HIPs and haptic objects 52 enables the surgical system 100 to constrain the surgical tool 36. In an embodiment in which the surgical tool 36 is a spherical burr, the HIP 60 may indicate the center of the spherical burr (FIG. 11A). For example, if the surgical tool 36 is irregularly shaped, such as sagittal saws 38 and 40 (FIGS. 2A and 2B), the virtual representation of the sagittal saw may include multiple HIPs. The use of multiple HIPs to generate haptic forces (e.g., positive force feedback, resistance to movement) on a surgical tool is described in U.S. patent application Ser. No. 13 / 339,369, filed Dec. 28, 2011, entitled "System and Method for Providing Substantially Stable Haptics," which is incorporated herein by reference in its entirety. In one embodiment of the present invention, a virtual tool 47 representing a sagittal saw includes eleven HIPs. References herein to a HIP are considered to include references to one or more HIPs. For example, HIP 60 can represent one or more HIPs, and any calculation or processing based on HIP 60 is considered to include calculation or processing based on multiple HIPs.

[0025] During surgery, the surgical system 100 constrains the surgical tool 36 based on the relationship between the HIP and the haptic object 52. In general, the term "constraint" is used herein to describe the property of restricting movement. However, the type of constraint applied to the surgical tool 36 depends on the shape of the associated haptic object 52. The haptic object 52 may be formed in any desired shape or form. As discussed above, three exemplary embodiments include a line, a plane, and a three-dimensional volume. In one embodiment, the surgical tool 36 is constrained because the HIP 60 of the surgical tool 36 is limited to movement along the linear haptic object 52. In another embodiment, the surgical tool 36 is constrained because the planar haptic object 52 substantially prevents movement of the HIP 60 outside of the plane and outside the boundaries of the planar haptic object 52. The boundaries of the planar haptic object 52 act as a fence surrounding the HIP 60. If the haptic object 52 is a three-dimensional volume, the surgical tool 36 may be constrained by substantially preventing movement of the HIP 60 outside the space bounded by the walls of the three-dimensional haptic object 52. The constraints imposed on the HIP 60 result in constraints on the surgical tool 36 due to the relationship between the virtual environment (including the virtual bone model 45 and the virtual tool 47) and the physical environment (including the patient's anatomy and the real surgical tool 36).

[0026] Tactile control during surgery Typically, at the start of surgery, the haptic device 30 (coupled to the surgical tool 36) is set to free mode, allowing the surgeon to move the surgical tool 36 toward the bone 44 in preparation for a planned modification, such as a cut or drill. In various embodiments described herein, the ease of switching the haptic device 30 from free mode to haptic control mode and back from haptic control mode to free mode allows the surgical system 100 to be more efficient and user-friendly.

[0027] One method of using the surgical system is shown in FIG. 4. In step 401, a surgical tool is prepared. A virtual HIP associated with the surgical tool (e.g., surgical tool 36 of FIG. 1) is also provided (step 402), such that movement of the HIP corresponds to movement of the surgical tool 36. The surgical method further includes setting a virtual start boundary and a virtual end boundary (step 403). As described further below, the start and end boundaries are virtual boundaries created during surgical planning, and interaction between the HIP and the start and end boundaries can facilitate switching of the haptic device 30 between free mode and haptic control mode during surgery. In other words, interaction between the HIP and the start and end boundaries facilitates engagement with and disengagement from haptic control. In step 404, a haptic object is activated. The activated haptic object can constrain movement of the surgical tool after a haptic interaction point crosses the virtual start boundary. In step 405, the haptic object is deactivated after the HIP crosses the virtual exit boundary. The term "after" includes deactivation occurring substantially simultaneously with the HIP reaching the virtual exit boundary, since the haptic object may be deactivated substantially simultaneously with the HIP reaching the virtual exit boundary.

[0028] 5A-5E illustrate a virtual environment for a start haptic control and end haptic control embodiment. In this embodiment, virtual bone model 45 represents femur 4, and virtual tool 47 represents surgical tool 36 in the form of sagittal saw 38 (e.g., shown in FIG. 2A). Sagittal saw 38 can be useful for making various cuts during a total knee replacement surgery, such as cuts corresponding to planned anterior cut 46, posterior cut 96, and tibial base cut 49 (FIGS. 3A-3D). In the embodiment shown in FIGS. 5A-5E, the planned modification is an anterior cut 46 corresponding to an anterior surface 68 of virtual implanted component 66 (FIG. 6A). FIG. 3B is a perspective view illustrating planned anterior cut 46 on virtual bone model 45. The virtual environment shown in FIG. 5A includes a planar haptic object 52. Planar haptic object 52 may also be an offset haptic object 78 (described below). The planar haptic object 52 can take on any desired shape, such as the shape shown in FIG. 6B . In FIG. 6B , the haptic object 52, the blade of the virtual tool 47, and the virtual implanted component 66 are all shown overlapping one another to facilitate understanding of the relationships between the various elements that make up the surgical plan. In this embodiment, the haptic object 52 represents the cut to be made in the femur 4. Accordingly, the haptic object 52 is shown in FIGS. 6A and 6B aligned with the anterior surface 68 of the virtual implanted component 66. The blade of the virtual tool 47 represents the blade when the haptic object 52 is activated in haptic control mode and constrained to the plane of the haptic object 52.

[0029] Referring again to FIG. 5A , the starting boundary 50 is a virtual boundary created during surgical planning. Interaction between the HIP 60 and the starting boundary 50 switches the haptic device 30 from free mode to an "auto-alignment mode," a stage of haptic control described in more detail below. The starting boundary 50 represents an implementation boundary near the patient's anatomy. The starting boundary 50 is designed and positioned so that the surgeon can accurately guide the surgical tool 36 to the implementation boundary when the haptic device 30 is in free mode. The starting boundary 50 often, but not necessarily, surrounds a portion of the haptic object 52. For example, in FIG. 5A , the starting boundary 50 surrounds a portion of the haptic object 52.

[0030] FIG. 5A illustrates a cross-section of a virtual environment. In this embodiment, starting boundary 50 has a pill shape and encloses a three-dimensional volume. The pill-shaped starting boundary 50 has one cylindrical portion of radius R (shown in FIG. 5A) and two hemispherical ends (not shown), also of radius R. A target line 54 forms the cylinder axis (perpendicular to the page in FIG. 5A). Target line 54 passes through target point 55, which is the center point of the cross-section of starting boundary 50 shown. Starting boundary 50 can also have other shapes and configurations, such as a sphere, a cube, a plane, or a curved surface.

[0031] In one embodiment, the starting boundary 50 may be a "Pac-Man-shaped" starting boundary 50a, as shown in FIG. 16. The Pac-Man-shaped starting boundary is formed by cutting out a portion of the pill-shaped starting boundary, resulting in the starting boundary 50a having the cross-section shown in FIG. 16, as described above. Thus, in this embodiment, the starting boundary 50a is a three-dimensional volume having the shape of a pill with a portion removed, such that the cross-section of the virtual starting boundary is a sector (i.e., a "Pac-Man shape"). The Pac-Man-shaped starting boundary 50a includes two intersecting haptic walls 52a. A target line 54 (perpendicular to the page in FIG. 16) represents the intersection of the haptic walls 52a. A target point 55 is the midpoint of the target line 54. The haptic wall 52a is one embodiment of the haptic object 52 described herein, thereby constraining the movement of the surgical tool 36 by preventing the HIP 60 from substantially crossing the haptic wall 52a. The haptic wall 52 allows the Pac-Man-shaped starting boundary 50a to create a safe area in front of the patient's bones. The Pac-Man-shaped starting boundary 50a can be used in any of the embodiments described herein as a starting boundary to protect the patient's bones when a surgical tool approaches the patient. FIG. 16 shows a virtual tool 47 (corresponding to the surgical tool 36) contacting a haptic wall 52a. The haptic wall 52a prevents the virtual tool 47 (and therefore the surgical tool 36) from crossing the haptic wall 52a and approaching the patient's bones.

[0032] At the start of surgery, the surgeon guides the surgical tool 36 toward the implementation boundary indicated by the starting boundary 50. When the surgeon causes the HIP 60 of the surgical tool 36 to cross the starting boundary 50, the surgical system 100 begins automatic alignment. Before or during automatic alignment, the surgical system 100 calculates a change in position and orientation of the surgical tool 36. In one embodiment, this calculation includes calculating a distance 58 (see FIG. 5B ). If the surgical tool 36 is a spherical burr, the distance 58 may represent the shortest line between a single HIP 60 and a target line 54 (e.g., as shown in FIG. 11B ) or other reference object. If the surgical tool 36 is a sagittal saw 38 or 40, the distance 58 may also be calculated, but the calculation of the change in position and orientation of the surgical tool 36 may be based on the positions of multiple HIPs relative to the target line 54 or other reference object.

[0033] After the necessary calculations are completed, the surgical system 100 can automatically align the surgical tool 36 from the state of the virtual tool 47 shown in FIG. 5B to the state of the virtual tool 47 shown in FIG. 5C. Haptic control according to the embodiments described herein includes (1) automatically correcting (i.e., repositioning) the position of the surgical tool 36, (2) automatically correcting (i.e., reorienting) the orientation of the surgical tool 36, or (3) automatically repositioning and reorienting the surgical tool 36. The term "automatic alignment" can refer to any of the scenarios (1), (2), or (3) above and is a general term for correcting either or both the position and orientation of the surgical tool 36. In the embodiment shown in FIGS. 5A-5E, for example, the automatic alignment may change both the position and orientation of the surgical tool 36 relative to the bone 44. The repositioning is accomplished by moving the HIP 60 so that it lies within the plane of the haptic object 52. In one embodiment, the HIP 60 is repositioned to lie on the target line 54. Reorientation of the surgical tool 36 may be accomplished by rotating the virtual tool 47 so that the virtual tool normal 48 is perpendicular to the haptic object 52 (i.e., the tool normal 48 is parallel to the haptic object normal 62), as shown in FIG. 5C . When the virtual tool 47 represents a sagittal saw 38, aligning the virtual tool normal 48 perpendicular to the haptic object 52 ensures that the blade 39 of the sagittal saw 38 is correctly oriented relative to the bone 44. However, if the cutting portion of the surgical tool 36 is symmetrical, such as when the surgical tool 36 is a spherical burr, reorientation of the surgical tool 36 is not necessary during automatic alignment. Rather, the surgical tool 36 may simply be repositioned so that the HIP 60 is within the plane of the haptic object 52. After automatic alignment is complete, the surgical tool 36 is in the proper position to perform bone modifications according to the pre-operative surgical plan.

[0034] The surgical system 100 may include safety mechanisms that allow the operator to maintain control during automatic alignment. The safety mechanisms may be designed to require a predetermined action (or continuation of an action) by the user to complete automatic alignment. In one embodiment, the surgical system 100 emits an audible noise or other alert when the HIP 60 crosses the start boundary 50. The surgical system 100 may then begin automatic alignment. However, the operator must press a trigger or take another action before automatic alignment begins. If the trigger is released during automatic alignment, the surgical system 100 may stop all automatic operation of the haptic device 30 or place the haptic device 30 in a free mode. In another embodiment, the haptic device 30 includes a sensor that detects when the operator's hand is present. If the operator removes their hand from the sensor during automatic alignment, the surgical system 100 may stop all automatic operation of the haptic device 30 or place the haptic device 30 in a free mode. The surgeon ensures that automatic alignment is complete by keeping their hand over the sensor. The safety features of these embodiments allow the surgeon to determine whether and for how long automatic alignment is enabled. Additionally, the surgeon can stop automatic alignment if other objects (e.g., tissue or instruments) interfere with the surgical tool 36 during automatic alignment.

[0035] The starting boundary 50a of FIG. 16 is particularly useful when the safety mechanisms described above are in place. As one example, the surgeon initiates the haptic control process described herein by guiding the surgical tool 36 toward the patient until it penetrates the starting boundary. The surgical system 100 then notifies the surgeon that the system is ready to begin automatic alignment. However, the surgeon does not have to immediately press a trigger or take other action to enable the system to begin automatic alignment mode. During this delay, the surgical tool 36 remains in free mode, allowing the surgeon to continue guiding the tool toward the patient. Accordingly, the starting boundary 50a of FIG. 16 includes haptic walls 52a. These haptic walls 52a prevent the surgeon from continuing to guide the surgical tool 36 (represented by the virtual tool 47) toward the patient prior to automatic alignment (e.g., by pressing a trigger or placing a hand on a sensor). In this manner, the haptic wall 52a serves as a safety mechanism to protect the patient prior to proper positioning and orientation of the surgical tool 36 to perform the planned bone modification.

[0036] Referring to FIG. 5C , automatic alignment has been completed, the orientation of the surgical tool 36 has been accurately corrected, and the haptic device 30 remains in the haptic control mode. Generally, the haptic control mode can be characterized by activating a haptic object 52 and imposing constraints on the movement of the surgical tool 36 by the haptic object 52. Therefore, automatic alignment can be considered a form of haptic control, because the haptic object 52 is activated and the surgical tool 36 is constrained by the haptic object 52 to specific movements for realigning the surgical tool 36. In the haptic control phase shown in FIG. 5C , the haptic object 52 is activated and the HIP 60 is constrained within a plane defined by the haptic object 52. Therefore, the surgeon can move the surgical tool 36 within a planar boundary corresponding to the haptic object 52, but is constrained (e.g., prevented) from moving the surgical tool 36 outside the planar boundary. The surgeon performs the planned cut in haptic control mode. While the surgeon is cutting, the virtual tool 47 can move in the x-axis direction from the position shown in FIG. 5C to the position shown in FIG. 5D. The virtual tool 47 may also move back and forth in the z-axis direction, corresponding to the movement of the surgical tool 36. However, the planar haptic object 52 limits the movement of the HIP 60 (and thus the surgical tool 36) in the y-axis direction. FIG. 6B shows the shape of the haptic object 52 according to one embodiment, along with the virtual tool 47 of FIG. 5C overlaid on the haptic object 52. The surgeon can reposition the sagittal plane saw 38 within the working boundary corresponding to the haptic object 52, but the surgical system 100 prevents the sagittal plane saw 38 from exceeding the outer boundary of the working boundary. FIG. 6A is a diagram of the haptic object 52 aligned with the anterior surface 68 of the virtual implanted component 66. As mentioned above, the modifications to the bone, and therefore to the haptic object 52, are typically planned to correspond to the shape of the elements that will be connected to the bone during surgery.

[0037] At some stages in the haptic control mode, an end boundary 64 is activated (see FIGS. 5C-5E). Similar to the start boundary 50 described above, the end boundary 64 is a virtual boundary created during surgical planning. Interaction between the HIP 60 and the end boundary 64 triggers the deactivation of the haptic object 52 and the switching of the haptic device 30 from the haptic control mode to the free mode. Thus, the surgical system maintains the haptic control mode and keeps the surgical tool 36 within the implementation boundary corresponding to the haptic object 52 until the HIP 60 crosses the end boundary 64. Once the HIP 60 crosses the end boundary 64 (e.g., by moving from the position shown in FIG. 5D to the position shown in FIG. 5E), the haptic object 52 is deactivated and the haptic device 30 switches from the haptic control mode to the free mode. When haptic control is released, the surgical tool 36 is no longer constrained within the implementation boundary and can be freely manipulated by the surgeon.

[0038] In one embodiment, the ending boundary 64 is a plane located a distance L from the starting boundary 50 (see FIG. 7A ) and has an ending normal 59. While in haptic control mode, the surgical system 100 continuously calculates the distance from the HIP 60 to the ending boundary 64. Because the ending normal 59 points away from the patient's anatomy, the distance from the HIP 60 to the ending boundary 64 is typically negative during bone modification (e.g., cutting, drilling). However, when this distance becomes positive, haptic control is released upon the haptic object 52 coming to a halt and the haptic device 30 enters free mode. In other embodiments, the ending boundary 64 can be curved, three-dimensional, or of any other configuration or shape suitable for interacting with the HIP 60, allowing haptic control to be released during surgery. Simultaneously, or immediately after switching to free mode, the ending boundary 64 is deactivated and the starting boundary 50 is reactivated. The surgeon can then re-enter the haptic control mode by bringing the surgical tool 36 closer to the patient so that the HIP 60 crosses the entry boundary 50. In this manner, the surgeon can move back and forth between the free mode and the haptic control mode by manipulating the surgical tool 36.

[0039] The start boundary 50 and end boundary 64 described in connection with various embodiments herein provide advantages over prior art haptic control. Some prior art haptic object embodiments require separate user actions to activate and deactivate the haptic object and thus initiate and terminate haptic control. For example, to release the HIP from the haptic object's area, the user must press a button or perform a similar action to deactivate the haptic object. The user action deactivates the haptic object, allowing the surgeon to freely manipulate the surgical tool. With the end boundary described herein, the surgeon does not need to perform a separate deactivation process. Rather, the surgeon simply pulls the surgical tool 36 away from the patient to automatically deactivate the haptic object 52 and terminate haptic control. Thus, the disclosed embodiments save time in the operating room. Furthermore, operation of the haptic device 30 is more intuitive and user-friendly as the operator can easily switch between free mode and haptic control mode.

[0040] 7A and 7B show haptic object 52 and offset haptic object 78. Surgical planning may include an adjustable offset haptic object 78 to account for the characteristics of surgical tool 36. Using offset haptic object 78 while haptic device 30 is in haptic control mode may improve surgical precision by taking into account the dimensions of surgical tool 36. Thus, if surgical tool 36 is a spherical burr, offset haptic object 78 may be moved from haptic object 52 such that distance 80 (FIG. 7B) is equal to the radius of the spherical burr. When offset haptic object 78 is activated, surgical system 100 constrains the spherical burr HIP 60 within the planar offset haptic object 78 rather than constraining the spherical burr HIP 60 within the planar haptic object 52. When constrained by the offset haptic object 78, the end of the spherical burr aligns with the planned anterior cut 46. Similarly, if the surgical tool 36 is a sagittal plane saw 38, the distance 80 may be equal to half the thickness t of the blade 39. FIG. 7B illustrates a virtual tool 47. In this embodiment, the virtual tool 47 is the sagittal plane saw 38 shown in FIG. 2A and includes a virtual blade 82. The virtual blade 82 has a thickness t equal to the thickness of the blade 39. When the HIP 60 of the virtual tool 47 is constrained to the offset haptic object 78, the bottom edge of the virtual blade 82 aligns with the planned anterior cut 46. As a result, the actual cut made by the sagittal plane saw 38 during surgery corresponds to the planned anterior cut 46 more accurately than if the HIP 60 were constrained to the haptic object 52 of FIG. 7B.

[0041] In various embodiments, the surgical system 100 utilizes factors related to the performance of the surgical plan when calculating the parameters of the adjustable offset haptic object 78. One factor may be vibration of the surgical tool 36 during surgery, which can cause a discrepancy between the actual dimensions of the surgical tool 36 and the effective dimensions of the surgical tool 36. For example, a spherical burr with a 3 mm radius can remove bone as if it had a 4 mm radius. Therefore, the burr has an effective radius of 4 mm. Similarly, a 2 mm thick blade 39 can vibrate to create a 2.5 mm thick groove in bone. Therefore, the blade 39 has an effective thickness of 2.5 mm. The offset haptic object 78 is created to take into account the effects of the vibration of the surgical tool 36 and other factors, as described above, to accurately perform actual surgical bone modifications.

[0042] The offset haptic object 78 may be adjustable. Adjustability is beneficial because it allows a user to modify the offset haptic object 78 without having to redesign the original haptic object 52. The surgical system 100 may be programmed to allow for easy adjustment by the user as new information is gathered before or during surgery. When a surgical plan includes an offset haptic object 78, elements added to the surgical plan may be similarly adjusted to positions offset from the originally planned positions of the elements. For example, the surgical system 100 may be programmed such that when the offset haptic object 78 is moved from the haptic object 52, the start boundary 50 and the end boundary 64 are also moved the same distance in the y-axis direction. Similarly, the target line 54 and the target point 55 may also be shifted from their originally planned positions. It should be understood that the "haptic object 52" referred to in many of the embodiments described herein may technically be a "displaced haptic object" relative to the original haptic object of the associated surgical plan.

[0043] 8A-8E illustrate a virtual environment during initiation and termination of haptic control according to another embodiment. In this embodiment, the virtual bone model 45 represents the femur 4. The virtual tool 47 represents the surgical tool 36 having the shape of a sagittal saw 40 (e.g., as shown in FIG. 2B). The sagittal saw 40 can be useful for making various cuts during a total knee replacement, such as cuts corresponding to the planned distal cut 84 and the anterior chamfer cut 92. In the embodiment shown in FIGS. 8A-8E, the planned modification is the planned distal cut 84, which corresponds to the distal face 72 of the virtual implanted component 66 (FIG. 9A). A perspective view of the planned distal cut 84 is shown in FIG. 3B. In this embodiment, as in the embodiment shown in FIGS. 5A-5E, the haptic object 52 represents the cut to be made in the femur 4. Haptic object 52 may include any shape established in the surgical plan, such as the shape shown in FIG. 9B.

[0044] Referring again to FIGS. 8A-8E, the initiation and termination of haptic control occurs similarly to the embodiment shown in FIGS. 5A-5E, differing primarily in the automatic alignment and final orientation of the surgical tool 36. Any suitable features disclosed in connection with the embodiment shown in FIGS. 5A-5E may also be present in the embodiment shown in FIGS. 8A-8E. In FIG. 8A, the haptic device 30 is in free mode, and the starting boundary 50 is activated. As the surgeon brings the surgical tool 36 toward the patient's anatomy, the virtual tool 47 correspondingly approaches the starting boundary 50. Once the HIP 60 crosses the starting boundary 50, the surgical system 100 enters automatic alignment, which corrects the position and orientation of the surgical tool 36 after the surgical system 100 performs the necessary calculations (e.g., FIGS. 8B-8C). The position is corrected so that the HIP 60 is aligned with the target line 54, and the orientation is corrected so that the tool axis 42 is perpendicular to the haptic object 52. The blade 39 (FIG. 2B) of the sagittal saw 40 is perpendicular to the tool axis 42, so by aligning the tool axis 42 perpendicular to the haptic object 52, the blade lies in the xy plane during surgery. The orientation of the tool axis 42 in this embodiment contrasts with the embodiment shown in FIGS. 5A-5E, in which the tool axis 42 is parallel to the haptic object 52 during cutting (e.g., FIG. 5C).

[0045] The surgical plan can be developed such that the surgical system 100 orients the surgical tool 36 in a desired orientation relative to the haptic object 52. The desired orientation may depend on the type of surgical tool. For example, if the surgical tool 36 is a sagittal saw, the surgical system 100 may orient the surgical tool 36 differently depending on the type of sagittal saw (e.g., sagittal saw 38 or sagittal saw 40) or the type of cut to be made. Furthermore, in some embodiments, the tool is repositioned but not reoriented during automatic alignment. For example, if the surgical tool 36 is a spherical burr, the surgical system 100 does not necessarily need to reorient the surgical tool 36 to make the desired modification to the bone.

[0046] As shown in FIG. 8C , once the surgical tool 36 is automatically aligned, the HIP 60 is constrained within the plane defined by the haptic object 52. Haptic control entering this phase triggers activation of the end boundary 64. The surgeon makes the cut by manipulating the surgical tool 36 within the planar implementation boundaries corresponding to the haptic object 52 in the x- and z-axes. FIGS. 8C and 8D illustrate the change in position while making the x-axis cut. As the surgeon moves the surgical tool 36 from the position shown in FIG. 8D to the position shown in FIG. 8E , the HIP 60 crosses the end boundary 64. The interaction between the HIP 60 and the end boundary 64 deactivates the haptic object 52, thereby releasing haptic control over the surgical tool 36 and causing the haptic device 30 to re-enter free mode. Upon or shortly after crossing the end boundary 64, the end boundary 64 is deactivated and the start boundary 50 is reactivated. The surgeon can then re-enter automatic alignment and haptic control during bone modification by manipulating the surgical tool 36 so that the HIP 60 crosses the starting boundary 50 .

[0047] 10 shows haptic object 52 and offset haptic object 78 relative to a planned distal cut 84. As described with respect to FIGS. 7A and 7B, adjustable offset haptic object 78 may be modified depending on factors such as the size of surgical tool 36 or other factors related to the performance of the surgical plan. Adjustment of offset haptic object 78 can lead to adjustment of other planned features in the virtual environment, such as start boundary 50, target line 54, target point 55, and end boundary 64.

[0048] The surgical plan depicted in Figures 7A-7B and 10 can be defined by various points and vectors. Normal start point 57 lies on original haptic object 52 and defines the origin of haptic object normal 62, in addition to end normal 59. Furthermore, haptic normal point 61 defines haptic object normal 62 and may be located approximately 50 mm from normal start point 57. Furthermore, end normal point 63 defines end normal 59 and may also be located approximately 50 mm from normal start point 57. Thus, haptic object normal 62 can be defined as a vector pointing from normal start point 57 to haptic normal point 61, and end normal 59 can be defined as a vector pointing from normal start point 57 to end normal point 63. The target point 55 can be located on the offset haptic object 78 and is offset from the normal start point 57 by a desired amount in the direction of the haptic object normal 62. As mentioned above, the desired amount can be determined taking into account the effective radius of the spherical borer or half the effective thickness of the sagittal saw blade 39. The target line 54 can be defined by the target point 55 and the cross product vector of the ending normal 59 and the haptic object normal 62, with an end point on the edge opposite the offset haptic object 78.

[0049] 11A-11E illustrate a virtual environment during initiation and termination of haptic control according to another embodiment. In this embodiment, the virtual bone model 45 represents a tibia 2. The virtual tool 47 represents a surgical tool 36 in the shape of a spherical burr, although the surgical tool 36 can be any tool capable of creating a planned hole 88. The planned modification is a hole 88 for receiving a peg of a tibial component. A spherical burr can also be used to create holes for receiving pegs of femoral, patellofemoral, or other types of implanted components. In FIGS. 11A-11E, a virtual tibial component 90 is superimposed on the bone model 45 to more clearly illustrate the planned bone modification. In this embodiment, the haptic object 52 is a line. The placement of the linear haptic object 52 may be planned based on the dimensions or effective dimensions of the surgical tool 36, such as the radius TR of the spherical burr (FIG. 12). As shown in FIG. 12, for example, a space equivalent to radius TR may be left between end 95 of haptic object 52 and the bottom of peg tip 91.

[0050] FIG. 11A shows the virtual environment when the haptic device 30 is in free mode. At the start of surgery, the surgeon moves the surgical tool 36 (FIG. 1) toward the patient until the HIP 60 crosses the starting boundary 50 (FIG. 11B). In this embodiment, the starting boundary 50 is a sphere with a radius R (FIG. 12) and a center point at a target point 55. Once the HIP 60 crosses the starting boundary 50, the surgical system automatically aligns the surgical tool 36. In one embodiment, the surgical system 100 calculates the shortest distance from the HIP 60 to the target point 55 and then repositions the HIP 60 on the target point 55. The surgical system 100 may also reorient the surgical tool 36 so that the tool axis 42 is parallel to the haptic object 52 (FIG. 11C). The HIP 60 is then constrained to movement along the linear haptic object 52, and the surgeon can move the surgical tool 36 along the linear implementation boundary corresponding to the haptic device 52 to form a hole 88 (Figure 11D).

[0051] As in the embodiment described above, the exit boundary 64 is activated during a portion of haptic control. When the surgeon desires to release haptic control, he or she can move the surgical tool 36 until the HIP 60 crosses the exit boundary 64 ( FIG. 11E ). When the haptic object 52 is subsequently deactivated, haptic control is released and the haptic device 30 re-enters free mode. As described with respect to other embodiments, the surgical system 100 may continually calculate the distance between the HIP 60 and the exit boundary 64 and release haptic control when the distance reaches a positive value. Also, as described with respect to the embodiment above, the start boundary 50 can be reactivated after haptic control is released. The surgeon can then resume haptic control by manipulating the surgical tool 36 so that the HIP 60 crosses the start boundary 50.

[0052] FIG. 12 illustrates additional features of a surgical plan including a linear haptic object 52, such as the surgical plan shown in FIGS. 11A-11E. The peg axis is a line extending from a peg tip point 91 at the end of the planned hole 88 to a target point 55. The linear haptic object 52 may be a line on the peg axis having a first end point at an end 95 and a second end point along an end normal 59 past the target point 55. For example, the second end point of the haptic object 52 may be 50 mm past the target point 55 in the direction of the end normal 59. The end boundary 64 may be a plane located a distance L from the start boundary 50 and may have an end normal 59 defined as a vector extending from the peg tip point 91 toward the target point 55.

[0053] 13A-13D illustrate the initiation and termination of haptic control according to another embodiment. In this embodiment, the haptic object 52 is a three-dimensional volume. The virtual bone model 45 can represent any bone 44, such as the femur 4, and the virtual tool 47 can represent any type of surgical tool 36 for performing any type of bone modification. In the virtual environment shown in FIG. 13A, the haptic device 30 is in free mode. To initiate haptic control, the user manipulates the surgical tool 36 toward the patient's anatomy. The virtual tool 47, along with the HIP 60, moves toward the starting boundary 50. In this embodiment, the starting boundary 50 is a plane with a target point 55 (not shown). When the HIP 60 is within the haptic object 52 and crosses the starting boundary 50, haptic control is initiated, as shown in FIG. 13B. In haptic control mode, HIP 60 is prevented from leaving the confines of the three-dimensional volume defined by haptic object 52. Furthermore, initiating haptic control deactivates start boundary 50 and activates end boundary 64 (FIG. 13C).

[0054] The embodiment shown in FIGS. 13A-13D does not include automatic alignment. In other words, during haptic control, the surgical tool 36 is not modified in position or orientation. As a result, the HIP 60 is free to move to any position within the haptic object 52, and the orientation of the surgical tool 36 is not constrained by the haptic object. During haptic control, the surgeon can freely move the surgical tool 36 within the implementation volume corresponding to the haptic object 52 to make any necessary bone modifications, such as cuts corresponding to the planned distal cut 84, the planned posterior chamfer cut 92, and the planned posterior cut 96. FIG. 13C shows the virtual tool 47 as the surgeon makes the cut corresponding to the planned posterior cut 96. During haptic control for the embodiment shown in FIGS. 13A-13D, as with the previously described embodiment, when the HIP 60 crosses the exit boundary 64 (FIG. 13D), haptic control is released and the haptic device 30 enters free mode. 13A-13D include additional features for controlling the position of HIP 60. For example, planar haptic objects aligned with planned cuts 84, 94, 96 could constrain HIP 60 to movement along these planar haptic objects. The virtual environment may also include features for controlling the orientation of virtual tool 47 (and therefore surgical tool 36), such as additional planar or linear haptic objects to which HIP 60 can be constrained.

[0055] FIG. 14 illustrates the surgical plan of FIGS. 13A-13D. End boundary 64 is parallel to start boundary 50 and is located a distance L from start boundary 50 along end normal 59. End normal 59 is a vector pointing from target point 55 toward end normal point 63. FIG. 14 also includes a prior art haptic object 98. In prior art haptic control methods, the user could not move the hip out of haptic object 98 without performing another action to release haptic control, such as pressing a button on input device 22 (FIG. 1). In contrast to prior art haptic object 98, three-dimensional haptic object 52 extends far from the planned cutting plane. Furthermore, the surgical plan for haptic object 52 includes start boundary 50 and end boundary 64. In the disclosed embodiment, when the surgeon moves the surgical tool 36 away from the patient causing the HIP 60 to reach the end boundary 64, the surgical system 100 automatically deactivates the haptic object 52 and releases haptic control. Thus, providing the end boundary 64 provides the surgeon with greater freedom during surgery, freed from haptic control. Additionally, the interaction between activating and deactivating the start boundary 50 and end boundary 64 described herein allows the surgeon to seamlessly and intuitively initiate and terminate haptic control through manipulation of the surgical tool 36, without requiring a separate action to initiate and terminate haptic control.

[0056] FIG. 15 illustrates a haptic recovery feature applicable to any of the haptic control embodiments described herein. The haptic recovery feature is applicable when haptic control is released for reasons other than crossing the HIP 60 end boundary. Haptic control release can occur for a variety of reasons, including a temporary inactivity of the navigation system 10, which detects the pose of one or more tracked objects. For example, some navigation systems require an unobstructed path between the detection device 12 and trackable features, such as the navigation markers 14, 16, the haptic device marker 18, and the end effector marker 19 (FIG. 1). If one of the trackable features is temporarily blocked (i.e., occluded), the navigation system 10 may be unable to effectively determine the pose of one or more tracked objects. As a safety precaution, the surgical system 100 may release haptic control of the surgical tool 36 if a trackable feature becomes occluded during surgery. Haptic control may also be released due to a sudden movement of the tracked object. For example, if the patient's leg or robotic arm 34 is bumped, the navigation system 10 may not be able to accurately track the suddenly moved object. This causes the surgical system to release haptic control of the surgical tool 36. When haptic control is released, the haptic device 30 enters free mode. The haptic recovery feature can then be utilized to resume haptic control by reactivating the haptic object 52, or to keep the haptic device 30 in free mode and prompt the surgeon to re-enter the starting boundary 50.

[0057] To determine whether to resume haptic control or maintain the haptic device 30 in free mode, the surgical system 100 is programmed to evaluate whether various conditions are met after haptic control is released due to the occlusion, sudden movement, or other factors. Generally, the conditions may relate to the position or orientation of the surgical tool 36 relative to a desired constrained position or orientation of the surgical tool 36. The conditions may also depend on the type of surgical tool 36 and the shape of the haptic object 52. Three possible conditions for the evaluation may be tool orientation, vertical penetration within the haptic plane, and whether all HIPs are within the haptic boundary. For example, the embodiment shown in FIG. 15 includes a virtual blade 82 representing a sagittal saw and including multiple HIPs (as noted above, although only one HIP 60 is labeled, the same reference numerals for the HIPs 60 apply to multiple HIPs as well). FIG. 15 also includes a planar haptic object 52. In this embodiment, the haptic recovery feature may include determining the orientation of the virtual blade 82 relative to the haptic object 52 by calculating the angle between the tool normal 48 and the haptic object normal 62. When the surgical tool 36 is constrained during cutting to reside within the implementation boundary corresponding to the planar haptic object 52, the tool normal 48 and the haptic object normal 62 are ideally parallel. One condition may be, for example, whether the angle between the tool normal 48 and the haptic object normal 62 is within 2 degrees. If this condition is met, the surgical system 100 may be programmed to ensure that the surgical tool 36 maintains a sufficiently accurate orientation even after a momentary occlusion of the trackable portion or a sudden movement of the patient or robotic arm. The surgical system 100 may also evaluate the position of the HIP 60 relative to the planar haptic object 52 (e.g., perpendicular penetration). 15 shows vertical boundaries 102, 104 above and below haptic object 52. Vertical boundaries 102, 104 can be planned, for example, to be located approximately 0.5 mm away from haptic object 52. A second condition may be whether HIP 60 is located between these vertical boundaries 102, 104.As another example, the third condition may be whether each of the HIPs 60 of the virtual blade 82 is within the outer boundary of the haptic object 52 .

[0058] If each of the relevant conditions is met, the haptic recovery feature reactivates the haptic object 52, resuming haptic control and allowing the surgeon to continue cutting. However, if none of the above conditions are met, the haptic device 30 remains in free mode. Thereafter, as described in various embodiments herein, the surgeon must return the HIP 60 until it crosses the starting boundary 50 (not shown in FIG. 15 ). Once the HIP 60 crosses the starting boundary 50, haptic control can resume. In the present embodiment shown in FIG. 15 , haptic control after the HIP 60 crosses the starting boundary 50 may include automatic alignment followed by constraints on the HIP 60 on the planar haptic object 52. In other embodiments, such as the embodiment shown in FIGS. 13A-13D , haptic control after the HIP 60 crosses the starting boundary 50 may not include automatic alignment.

[0059] The configurations and arrangements of the systems and methods as shown in the various exemplary embodiments are merely examples. While only a few embodiments have been described in detail in this disclosure, numerous modifications (e.g., changes in size, dimensions, structure, shape, proportions of various components, parameter values, use of materials, color, orientation, etc.) are possible. For example, the location of each component may be reversed or otherwise changed, and the nature or number of individual components or locations may be altered or changed. Accordingly, all such modifications are intended to be included within the scope of this disclosure. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. Other substitutions, modifications, alterations, and omissions may be made to the design by altering the conditions or arrangement of the exemplary embodiments without departing from the scope of this disclosure.

[0060] The present disclosure contemplates methods, systems, and program products on machine-readable media for performing various procedures. The disclosed embodiments may be implemented using existing computer processors, by computer processors incorporated into systems suitable for specific or other applications, or by hardware-embedded systems. Embodiments within the scope of the present disclosure encompass program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media may be any media available for access by a general-purpose or special-purpose computer or other machine with a processor. By way of example, such machine-readable media include RAM, ROM, EPROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, other magnetic storage, semiconductor storage, or any other medium that can be used to carry or store desired program code in the form of machine-executable instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or other machine with a processor. When information is transmitted or provided over a network or another communications connection (whether hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection may properly be termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions comprise, for example, instructions and data that cause a general-purpose computer, special-purpose computer, or special-purpose processing device to implement a certain function or group of functions.

[0061] Although the method steps are described in a particular order, the order of the steps need not necessarily be as described. Also, two or more steps (e.g., deactivating start boundary 50 and activating end boundary 64) may be performed in whole or in part simultaneously. Such variations depend on the software and hardware systems selected and designer preferences. All such variations are within the scope of the disclosure. Similarly, software implementation can be accomplished by standard programming techniques using rule-based logic and other logic to accomplish the connecting, processing, comparing, and decision steps.

Claims

1. tool, a robotic device configured to be coupled to the tool; and A controller, a processor; When executed, the processor: controlling the robotic device to provide automatic movement of the tool to a plane associated with a human anatomy; and Based on the tool's automatic movement to reach the plane, controlling the robotic device to cause the tool to remain at the plane while allowing manual repositioning of the tool. a non-transitory computer-readable memory storing instructions for performing operations including The controller A surgical system comprising:

2. The surgical system of claim 1 , wherein the plane is offset from a planned resection.

3. The surgical system of claim 2 , wherein the plane is offset from the planned resection by an amount based on blade size.

4. The surgical system of claim 1 , further comprising a sensor for sensing the presence of a user.

5. The surgical system of claim 4 , wherein controlling the robotic device to provide the automatic operation includes enabling the automatic operation when the sensor detects the presence of the user.

6. 5. The surgical system of claim 4, wherein controlling the robotic device to provide the automatic operation includes disabling the automatic operation when the sensor does not sense the presence of the user.

7. the robotic device extends from a base of the robotic device to a distal end of the robotic device; the surgical system further includes a tracking system configured to track a distal end of the robotic device and a base of the robotic device. The surgical system of claim 1 .

8. The surgical system of claim 1 , further comprising a saw separate from the tool.

9. The surgical system of claim 8 , wherein the saw is a sagittal saw configured to perform bone resections.

10. The surgical system of claim 1 further comprising a burr separate from the tool.

11. The surgical system of claim 1 , wherein the manipulation further comprises defining the plane based on an implantation plan.

12. surgical tools, a robot for holding the surgical tool; and a non-transitory computer readable memory that, when executed in communication with the robot, causes the robot to: automatically moving the surgical tool to a tactile object associated with a human body structure; and allowing the surgical tool to remain at the haptic object while allowing manual repositioning of the surgical tool along or within the haptic object following the surgical tool reaching the haptic object; the non-transitory computer readable memory storing instructions for performing operations including Including, the system.

13. The system of claim 12 , wherein the haptic object is a line.

14. The system of claim 12 , wherein the haptic object is a plane.

15. The system of claim 12 , wherein the haptic object is offset from the planned resection.

16. The system of claim 15 , wherein the haptic object is offset from the planned resection by an amount based on blade size.

17. The system of claim 12 further comprising a saw separate from the surgical tool.

18. The system of claim 12 further comprising a burr separate from the surgical tool.

19. 1. A method of operating a robotic device to constrain movement of a surgical tool, comprising: The robotic device creates an automatic movement of the surgical tool in a plane associated with a human anatomy; and and based on the automatic movement of the surgical tool reaching the plane, the robotic device causes the surgical tool to remain at the plane. A method comprising:

20. The method of claim 19 , further comprising the robotic device defining the plane to have an offset from the planned resection based on a size of a saw or burr.

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