Patent Description:
Computer-assisted surgery has been developed in order to help a surgeon in altering bones, and in positioning and orienting implants to a desired location. Computer-assisted surgery may encompass a wide range of devices, including surgical navigation, pre-operative planning, and various robotic devices. One area where computer-assisted surgery has potential is in orthopedic joint repair or replacement surgeries. For example, soft tissue balancing is an important factor in articular repair, as an unbalance may result in joint instability. However, when performing orthopedic surgery on joints, soft tissue evaluations are conventionally done by hand, with the surgeon qualitatively assessing the limits of patient's range of motion. The conventional technique may result in errors or lack precision.

<CIT> discloses a motorized joint positioner including a first robotic arm coupled to a first holder and a second robotic arm coupled to a second holder. At least one of the first and second robotic arms includes an actuator controllable to position the corresponding first or second holder.

<CIT>, <CIT>, and <CIT> represent additional relevant prior art.

According to the invention, there is provided a robot-aided knee arthroplasty system as set out in claim <NUM>. The methods described herein are not claimed, but are useful for the understanding of the invention.

The systems and methods described herein may be used for soft tissue balancing using a robotic arm. A robotic arm, used during a surgical procedure may perform soft tissue balancing assessment. For example, a component (such as a pin, a cutting block, etc., as further described below) anchors to a bone and the robotic arm driven to pull on the bone y to perform the soft tissue balancing assessment. In an example, the soft tissue may be placed under tension to determine balance. Applied tension may be determined using information received from a force/torque sensor in the robotic arm. The robotic arm may include a sensor (e.g., inertial, optical, encoder, etc.) to measure a rotation indicative of a rotation required for soft tissue balancing. The soft tissue balancing may be performed with the robotic arm with a leg in flexion or in extension. In an example, a computer-assisted surgery (CAS) system may be used to implement or control the robotic arm.

In an example, a robotic arm may raise an end effector (e.g., located at a distal end of the robotic arm) to displace a femur, while the tibia remains still by gravity, by its fixation to the table (e.g., when a foot support is used), by a human (e.g., surgical assistant or the surgeon), by surgical tape, self-adherent wrap or tape, or other fixing devices or components to secure the tibia. In another example, the robotic arm may use a laminar spreader to spread the bones apart. The laminar spreader may be inserted in the gap between the femoral condyles and the tibial plateau. In order to assist the laminar spreader, additional devices may be used and manipulated by the robotic arm. For example, the robotic arm may manipulate a clamp to benefit from the leveraging of the clamp to apply a greater moment of force at the bones. The laminar spreader may include a gear mechanism (e.g., planetary gear device, rack and pinion, etc.) to assist in amplifying the force of the robotic arm.

A joint laxity may be determined using a sensor on the robotic arm or a component attached to the robotic arm, such as to assist in the soft-tissue balancing at different times during a surgical procedures. For example, soft-tissue balancing may be determined prior to having the robotic arm perform an alteration to the bone, to confirm a predetermined implant size or location on the bone, or to enable adjustments to the predetermined implant size or location on the bone. In another example, the soft-tissue balancing may be determined after one or more cut planes have been made, such as to determine whether further adjustments are necessary.

Referring to the drawings and more particularly to <FIG>, a computer-assisted surgery (CAS) system is generally shown at <NUM>, and is used to perform orthopedic surgery maneuvers on a patient, including pre-operative analysis of range of motion and implant assessment planning, as described hereinafter. The system <NUM> is shown relative to a patient's knee joint in supine decubitus, but only as an example. The system <NUM> could be used for other body parts, including non-exhaustively hip joint, spine, and shoulder bones. A particular function of the CAS system <NUM> is assistance in planning soft tissue balancing, whereby the CAS system <NUM> may be used in total knee replacement surgery, to balance tension/stress in knee joint ligaments.

The CAS system <NUM> may be robotized, in which case it may have a robot arm <NUM>, a foot support <NUM>, a thigh support <NUM> and a CAS controller <NUM>. The robot arm <NUM> is the working end of the system <NUM>, and is used to perform bone alterations as planned by an operator or the CAS controller <NUM> and as controlled by the CAS controller <NUM>. The foot support <NUM> supports the foot and lower leg of the patient, in such a way that it is only selectively movable. The foot support <NUM> may be robotized in that its movements may be controlled by the CAS controller <NUM>. The thigh support <NUM> supports the thigh and upper leg of the patient, again in such a way that it is only selectively or optionally movable. The thigh support <NUM> may optionally be robotized in that its movements may be controlled by the CAS controller <NUM>. The CAS controller <NUM> controls the robot arm <NUM>, the foot support <NUM>, or the thigh support <NUM>. Moreover, as described hereinafter, the CAS controller <NUM> may perform a range-of-motion (ROM) analysis and implant assessment in pre-operative planning, with or without the assistance of an operator. The CAS controller <NUM> may also guide an operator through the surgical procedure, by providing intraoperative data of position and orientation and joint laxity boundaries, as explained hereinafter. The tracking apparatus <NUM> may be used to track the bones of the patient, and the robot arm <NUM> when present. For example, the tracking apparatus <NUM> may assist in performing the calibration of the patient bone with respect to the robot arm, for subsequent navigation in the X, Y, Z coordinate system.

Referring to <FIG> and <FIG>, a schematic example of the robot arm <NUM> is provided. The robot arm <NUM> may stand from a base <NUM>, for instance in a fixed relation relative to the operating-room (OR) table supporting the patient. In one example configuration, the OR table may consist of a 'U'-shaped end portion with each side of the 'U' supporting a leg of the patient and an open floor space existing between each leg. In this configuration, the base is positioned in the open floor space between the legs, therefore allowing the robot arm to access each leg of the patient without repositioning the base as would be desired in a bilateral total knee replacement procedure. The relative positioning of the robot arm <NUM> relative to the patient is a determinative factor in the precision of the surgical procedure, whereby the foot support <NUM> and thigh support <NUM> may assist in keeping the operated limb fixed in the illustrated X, Y, Z coordinate system. The robot arm <NUM> has a plurality of joints <NUM> and links <NUM>, of any appropriate form, to support a tool head <NUM> that interfaces with the patient. The arm <NUM> is shown being a serial mechanism, arranged for the tool head <NUM> to be displaceable in a desired number of degrees of freedom (DOF). For example, the robot arm <NUM> controls <NUM>-DOF movements of the tool head <NUM>, i.e., X, Y, Z in the coordinate system, and pitch, roll and yaw. Fewer or additional DOFs may be present. For simplicity, only a generic illustration of the joints <NUM> and links <NUM> is provided, but more joints of different types may be present to move the tool head <NUM> in the manner described above. The joints <NUM> are powered for the robot arm <NUM> to move as controlled by the controller <NUM> in the six DOFs. Therefore, the powering of the joints <NUM> is such that the tool head <NUM> of the robot arm <NUM> may execute precise movements, such as moving along a single direction in one translation DOF, or being restricted to moving along a plane, among possibilities. Such robot arms <NUM> are known, for instance as described in <CIT>.

Referring to <FIG>, the tool head <NUM> is shown in greater detail. The tool head <NUM> may have laminar spreader plates <NUM>, actuatable independently from a remainder of the tool head <NUM>, for simultaneous use with a tool support by the tool head <NUM>. The laminar spreader plates <NUM> are used to spread soft tissue apart to expose the operation site. The laminar spreader plates <NUM> may also be used as pincers, to grasp objects, etc. The tool head <NUM> may also comprise a chuck or like tool interface, typically actuatable in rotation. In <FIG>, the tool head <NUM> supports a burr 26A, used to resurface a bone. In <FIG>, the tool head <NUM> supports a circular tool 26B. As a non-exhaustive example, other tools that may be supported by the tool head <NUM> include a registration pointer, a reamer, a reciprocating saw, a retractor, depending on the nature of the surgery. The various tools may be part of a multi-mandible configuration or may be interchangeable, whether with human assistance, or as an automated process. The installation of a tool in the tool head <NUM> may then require some calibration in order to track the installed tool in the X, Y, Z coordinate system of the robot arm <NUM>.

In order to preserve the fixed relation between the leg and the coordinate system, and to perform controlled movements of the leg as described hereinafter, a generic embodiment is shown in <FIG>, while one possible implementation of the foot support <NUM> is shown in greater detail in <FIG>. The foot support <NUM> may be displaceable relative to the OR table, in order to move the leg in flexion/extension (e.g., to a fully extended position and to a flexed knee position), with some controlled lateral movements being added to the flexion/extension. Accordingly, the foot support <NUM> is shown as having a robotized mechanism by which it is connected to the OR table, with sufficient DOFs to replicate the flexion/extension of the lower leg. Alternatively, the foot support <NUM> could be supported by a passive mechanism, with the robot arm <NUM> connecting to the foot support <NUM> to actuate its displacements in a controlled manner in the coordinate system. The mechanism of the foot support <NUM> may have a slider <NUM>, moving along the OR table in the X-axis direction. Joints <NUM> and links <NUM> may also be part of the mechanism of the foot support <NUM>, to support a foot interface <NUM> receiving the patient's foot.

Referring to <FIG>, an example of the foot interface <NUM> has an L-shaped body ergonomically shaped to receive the patient's foot. In order to fix the foot in the foot support <NUM>, different mechanisms may be used, one of which features an ankle clamp <NUM>. The ankle clamp <NUM> surrounds the rear of the foot interface <NUM>, and laterally supports a pair of malleolus pads <NUM>. The malleolus pads <NUM> are positioned to be opposite the respective malleoli of the patient, and are displaceable via joints <NUM>, to be brought together and hence clamp onto the malleoli. A strap <NUM> may also be present, to further secure the leg in the foot support <NUM>, for example by attaching to the patient's shin. As an alternative to the arrangement of <FIG>, a cast-like boot may be used, or a plurality of straps <NUM>, provided the foot is fixed in the foot support <NUM>. In essence, the foot support <NUM> must anchor the leg to the table, with controllable movements being permissible under the control of the controller <NUM>.

Referring to <FIG>, the thigh support <NUM> may be robotized, static or adjustable passively. In the latter case, the thigh support <NUM> may be displaceable relative to the OR table, in order to be better positioned as a function of the patient's location on the table. Accordingly, the thigh support <NUM> is shown as including a passive mechanism, with various lockable joints to lock the thigh support <NUM> in a desired position and orientation. The mechanism of the thigh support <NUM> may have a slider <NUM>, moving along the OR table in the X-axis direction. Joints <NUM> and links <NUM> may also be part of the mechanism of the thigh support <NUM>, to support a thigh bracket <NUM>. A strap <NUM> may immobilize the thigh/femur in the thigh support <NUM>. The thigh support <NUM> may not be necessary in some instances. However, in the embodiment in which the range of motion is analyzed, the fixation of the femur via the thigh support <NUM> may assist in isolating joint movements.

Referring to <FIG>, the CAS controller <NUM> is shown in greater detail relative to the other components of the robotized surgery system <NUM>. The controller <NUM> has a processor unit to control movement of the robot arm <NUM>, and of the leg support (foot support <NUM> and thigh support <NUM>), when applicable. The robotized surgery controller <NUM> provides computer-assisted surgery guidance to an operator, whether in the form of a range-of-motion (ROM) analysis or implant assessment in pre-operatively planning or during the surgical procedure. The system <NUM> may comprise various types of interfaces, for the information to be provided to the operator. The interfaces may be monitors or screens including wireless portable devices (e.g., phones, tablets), audio guidance, LED displays, among many other possibilities. For example, there is illustrated in <FIG> and <FIG> graphic user interfaces (GUI) e.g., <NUM>, <NUM>, <NUM>. <NUM>, and 3300A-3300D that may be operated by the system <NUM>. The controller <NUM> may then drive the robot arm <NUM> in performing the surgical procedure based on the planning achieved pre-operatively. The controller <NUM> may do an intra-operative soft-tissue balancing assessment, and hence enable corrective plan cuts to be made, or guide the selection of implants or other intra-operative adjustments to the plan. The controller <NUM> may also perform a post-operative ROM analysis.

The controller <NUM> may hence have a robot driver <NUM>, such as when the robot arm <NUM> is part of the CAS system <NUM>. The robot driver <NUM> is tasked with powering or controlling the various joints of the robot arm <NUM>, foot support <NUM> and thigh support <NUM>, when applicable. As shown with bi-directional arrows in <FIG>, there may be some force feedback provided by the robot arm <NUM> and leg support <NUM>,<NUM> to avoid overextending the leg or damaging the soft tissue, and to assist in determining joint laxity boundaries. The robot driver <NUM> may control the foot support <NUM> in performing particular motions, to replicate a flexion/extension of the knee, with lateral movements, to measure soft tissue tension and analyze the range of motion of the leg, including varus/valgus. As such, the robot driver <NUM> may output the instant angle of flexion using the position or orientation data it uses to drive the movement of the foot support <NUM>. Sensors A are provided on the foot support <NUM> or in the robot arm <NUM> in order to measure throughout the movement the forces indicative of the tension/stress in the joint. The sensors A must therefore be sensitive enough to detect soft tissue tension/stress through the movement of the foot support <NUM>. In the case of the robot arm <NUM>, the sensors A may be force-torque sensors integrated therein.

The CAS controller <NUM> may use a processor to implement force measurement <NUM>. Force measurement <NUM> may include receiving the signals from the sensors A, and calculating the instant forces in the foot support <NUM>, representative of the tension/stress in the knee joint, or in the robot arm <NUM>, as exemplified hereinafter. The instant forces may be used to perform ROM analysis <NUM> using the processor, along with the foot support tracking data from the robot driver <NUM>. Alternatively or additionally, the ROM analysis <NUM> may use tracking data received from the tracking device <NUM> to determine the range of motion of the leg, as explained hereinafter. The ROM analysis <NUM> may convert the signals from the tracking device <NUM> into position or orientation data. In the latter case, various types of tracking technology may be used to determine the instant flexion/extension and varus/valgus, such as optical tracking as illustrated in <FIG>, inertial sensors, etc. With the combined data from the force measurement <NUM> and from the robot driver <NUM> or other source such as surgeon or medical professional assessment, the ROM analysis <NUM> may be performed. Exemplary formats of the ROM analysis <NUM> are shown in <FIG> and in <FIG>, described hereinafter. The information of the ROM analysis <NUM> may therefore be a pre-operative indication of the current varus/valgus as a function of flexion/extension. The ROM analysis <NUM> may be performed intraoperatively, or post-operatively, to assist in quantifying the soft tissue balancing during or resulting from surgery.

The processor may be used to perform an implant assessment <NUM> to determine how an implant or implants will impact the range of motion. Using the ROM analysis <NUM>, the implant assessment <NUM> takes into consideration the geometrical configuration of the implants based on selectable locations on the bone. For example, the implant assessment <NUM> may include the bone models B from pre-operative imaging (e.g., MRI, CT-scans), whether in 3D or in multiple 2D views. The implant assessment <NUM> may include the implant models C, such the 3D model files including implants of different dimensions.

The implant assessment <NUM> may be performed in a fully automated manner by the processor, in evaluating from the bone model, implant models or from the ROM analysis <NUM> desired implant sizes and location on the bone (i.e., in position and orientation), to balance soft tissue tension/stress. Exemplary formats of the implant assessment are shown in <FIG>, <FIG> and <FIG>, described hereinafter. The information of the implant assessment may therefore be a pre-operative or intraoperative indication of an anticipated post-surgical varus/valgus as a function of flexion/extension.

The implant assessment <NUM> may optionally include operator participation. The illustrations of <FIG> and <FIG> may be GUI items, such as in GUI <NUM> of <FIG> and <FIG> that may be adjusted virtually manually by an operator, for the operator to see the impact on the graphs of <FIG>, respectively. In such an embodiment, the implant assessment <NUM> may provide the assessment to assist the operator in making a decision, as opposed to automatically proposing the desired implant sizes and location on the bone. The proposal of desired implant sizes and location on the bone may be a starting point of operator navigation or decision making. When the implant sizes and location on the bone is selected or set, the implant assessment <NUM> may produce the output D in any appropriate format, such as GUIs <NUM>. The format may also be that of <FIG>, providing an assessment of the proposed implant sizes and location. The output D may also include bone alteration data to assist the operator or the robot arm <NUM> in performing the bone alterations. In such a case, the processor may perform a resurfacing evaluation <NUM> to calculate the bone cut volume and location, for the bone cuts that will be made based on the implant sizes and location on the bone.

The output D may also be a navigation file for the robot arm <NUM> to perform bone alterations based on the pre-operative planning from the implant assessment <NUM>, when the system <NUM> is robotized. The navigation file may include patient-specific numerical control data defining the maneuvers to be performed by the robot arm <NUM> as directed by the robot driver <NUM> of the system <NUM>, or of another system <NUM> in an operating room. The navigation file for robotized surgery may incorporate a calibration subfile to calibrate the robot arm <NUM> and patient joint prior to commencing surgery. For example, the calibration subfile may include the bone model B of the patient, for surface matching to be performed by a registration pointer of the robot arm <NUM>. The robot arm <NUM> may obtain a cloud of bone landmarks of the exposed bones, to reproduce a 3D surface of the bone. The 3D surface may then be matched to the bone model B of the patient, to set the 3D model in the X, Y, Z coordinate system.

The use of the tracking apparatus <NUM> may be determinative on the information that will be in the navigation file C, and may provide tracking data to perform the ROM analysis <NUM>. For example, the tracking apparatus <NUM> may assist in performing the calibration of the patient bone with respect to the robot arm <NUM>, for subsequent navigation in the X, Y, Z coordinate system. According to an embodiment, the tracking apparatus <NUM> comprises a camera that optically sees and recognizes retro-reflective references 71A, 71B, and 71B, so as to track the limbs in six DOFs, namely in position and orientation. In an embodiment featuring the robot arm <NUM>, the reference 71A is on the tool head <NUM> of the robot arm <NUM> such that its tracking allows the controller <NUM> to calculate the position or orientation of the tool head <NUM> and tool 26A thereon. Likewise, references 71B and 71C are fixed to the patient bones, such as the tibia for reference 71B and the femur for reference 71C. As shown, the references <NUM> attached to the patient need not be invasively anchored to the bone, as straps or like attachment means may provide sufficient grasping to prevent movement between the references <NUM> and the bones, in spite of being attached to soft tissue. However, the references 71B and 71C could also be secured directly to the bones. Therefore, the ROM analysis <NUM> of the controller <NUM> may be continuously updated to obtain a current position or orientation of the robot arm <NUM> or patient bones in the X, Y, Z coordinate system using the data from the tracking apparatus <NUM>. As an alternative to optical tracking, the tracking system <NUM> may consist of inertial sensors (e.g., accelerometers, gyroscopes, etc) that produce tracking data to be used by the controller <NUM> to continuously update the position or orientation of the robot arm <NUM>. Other types of tracking technology may also be used.

The calibration may be achieved in the manner described above, with the robot arm <NUM> using a registration pointer on the robot arm <NUM>, and with the assistance of the tracking apparatus <NUM> when present in the robotized surgery system <NUM>. Another calibration approach is to perform radiography of the bones with the references <NUM> thereon, at the start of the surgical procedure. For example, a C-arm may be used for providing suitable radiographic images. The images are then used for the surface matching with the bone model B of the patient. Because of the presence of the references <NUM> as fixed to the bones, the intraoperative registration may then not be necessary, as the tracking apparatus <NUM> tracks the position or orientation of the bones in the X, Y, Z coordinate system after the surface matching between X-ray and bone model is completed.

<FIG> illustrate a robotic arm <NUM> with a detachable pin guide component <NUM> coupled to an end effector component <NUM> in accordance with some embodiments. The detachable pin guide component <NUM> may include one or more pins (e.g., pins <NUM> and <NUM>), which may fit in one or more apertures of the end effector component <NUM>. The detachable pin guide component <NUM> may couple with the end effector component <NUM> in a locked position (e.g., as shown in <FIG>) and may be removed (e.g., as shown in <FIG>). The detachable pin guide component <NUM> may be locked to the end effector component <NUM> using, for example, a screw, friction, etc. In an example, the detachable pin guide component <NUM> may be disposable.

In an example, the detachable pin guide component <NUM> may include a cut guide (e.g., an slot for inserting a saw or other surgical instrument). For example, the detachable pin guide component <NUM> may include a femoral cut guide, a tibial cut guide, a <NUM>-in-<NUM> cut guide, or the like. In an example, the detachable pin guide component <NUM> may be configured for use with a specific implant or may be used generically.

In an example, a bushing may be used, such as between the detachable pin guide component <NUM> and the end effector component <NUM>. The bushing may be used to prevent jamming between the end effector component <NUM> and the detachable pin guide component <NUM> or allow for easy removal of the detachable pin guide component <NUM>. The bushing may be removable, and may be affixed to the end effector component <NUM>. In another example, the end effector component may include one or more pins and the detachable pin guide component <NUM> may include one or more apertures; these features may be in addition to or may replace the one or more pins of the detachable pin guide component <NUM> (e.g., pins <NUM> or <NUM>) or the apertures of the end effector component <NUM>.

The detachable pin guide component <NUM> may include a groove corresponding to a groove on the end effector component <NUM>. When the detachable pin guide component <NUM> and the end effector component <NUM> are coupled, the grooves may provide an aperture for receiving a soft tissue balancing component. The robotic arm <NUM> may apply force to the soft tissue balancing component using the end effector component <NUM> or the detachable pin guide component <NUM> locked to the end effector component <NUM>. The soft tissue balancing component (e.g., as described in further detail below, for example in the discussion of <FIG>, <FIG>, and <FIG>) may apply force in turn to a bone or implant component to test or configure soft tissue balance.

The soft tissue balancing component may be used to perform a ligament balance pull test. Based on the pull test, a femoral rotation is determined. The femoral rotation may be presented (e.g., using a graphical user interface, such as those described below in the discussion of <FIG> and <FIG>). The femoral implant rotation is used to calculate a target femoral implant rotation. The target femoral implant rotation may be displayed (e.g., using a user interface, such as those described below in the discussion of <FIG>). The target femoral implant rotation may be an inverse or opposite of the rotation of the femur rotation. For example, when the femur rotation is <NUM> degrees internally, the target femoral implant rotation may be <NUM> degrees external from the femur. The target femoral implant rotation may be further adjusted as well.

The femoral implant rotation may be determined such that the rotation may compensate for an imbalance in soft tissue tension between medial and lateral compartments. The rotation of the femur during the pull test may be directly related to the determined femoral implant rotation such that a rectangular or balanced gap results from applying the rotation. For example, when the rotation is applied to placement of the implant, the gap may be balanced between the medial and the lateral compartments. In an example, the robotic arm <NUM> may apply a force to perform the pull test by using the soft tissue balancing component to pull on the femur. To perform the test, the robotic arm <NUM> may apply one or more known loads to increase the accuracy of the determined rotation.

In an example, a torque or force sensor may be used to measure torque of one or more of the components depicted in <FIG>, such as the robotic arm <NUM>, the end effector component <NUM>, or the detachable pin guide component <NUM>, or on a component such as a soft tissue balancing component. In an example, a sensor may be used to detect ligament stress or ligament tension. In another example, a position or orientation sensor (e.g., a navigation sensor, such as a sensor located on a portion of the robotic arm <NUM>) may be used to determine a varus or valgus angle of a target leg. The varus or valgus angle may be used to determine ligament pulling in the target leg. From the varus or valgus angle or the stress or tension on the ligament, pulling on the soft tissue may be determined and a rotation to correct the pulling may be determined, and may be output on a graphical user interface (GUI), such as that described with respect to <FIG>.

In an example, a ligament test or other soft tissue balancing test may be performed before a bone resection cut is performed. For example, the soft tissue balancing test may be performed before any resection of a femur or a tibia. In an example, the soft tissue balancing test may be performed after resection and implantation of an implant to verify that the soft tissue is correctly balanced. For example, a first test may be performed pre-resection, which may result in a rotation angle to be used for balancing, and a second test may be performed after the implant is inserted to verify that the rotation angle was correct or that the implant was properly seated.

In an example, resecting a bone may include using the robotic arm <NUM>. The robotic arm <NUM> may have a cut guide attached to the end effector component <NUM> to guide the resection. A guide may be used to align a cutting, burring, or sawing device with a target object, such as a target bone. Cut guides are often manually placed by a surgeon on the target object. In other examples, cuts are made using fully autonomous robotic cutting devices. In another example, a surgeon may guide the robotic arm <NUM> collaboratively with force assistance from the robotic arm <NUM> (e.g., using a force sensor coupled to the robotic arm <NUM>). In this example, the surgeon may apply a small directional force while the robotic arm <NUM> moves in response. The robotic arm <NUM> may then automatically align to a cut plane in response to a surgeon selection (e.g., on the robotic arm <NUM> or on a user interface). In an example, the cut guide may be used to precisely align a surgical instrument to make a cut, such as on a target bone or other target object. The alignment of the end effector component <NUM> may involve a planning system with a user interface including positioning a representation of the end effector component <NUM> on a representation of the target object. During the surgical procedure, a selectable indication on an intraoperative user interface (e.g., those of <FIG>) may be used to activate movement the end effector component <NUM> to the planned alignment position. The cut guide may be used as a guide for the surgical instrument to make a cut on the target object, such as to align the surgical instrument with a specific plane or line. By using a cut guide, a surgeon may retain control of the surgical instrument while also using the robotic arm <NUM> to ensure that the surgical instrument is aligned with a predetermined cut plane or cut line. The robot in conjunction with a surgical navigation system allows for repeatable transfer of pre-defined surgical plan to the patient during the surgical procedure, while still allowing the surgeon some level of control over the final cuts.

<FIG> illustrates a soft tissue balancing component, including a spike <NUM> for use in a robotic soft tissue balancing system 600A in accordance with some embodiments. The spike <NUM> may be used as a femoral spike to apply force to a femur. The spike <NUM> may include a shaft portion <NUM> to receive force and transfer the force via rigidity of the spike <NUM> to a spike portion <NUM>, which in turn may apply force on the femur. The spike <NUM> may include a hollow shaft defined by an outer shaft wall <NUM>. The hollow shaft may be perpendicular to the shaft portion <NUM>. The hollow shaft may be used to lock or secure the spike in place (e.g., to prevent rotation), such as relative to a robotic arm or component.

In an example, the spike portion <NUM> of the spike <NUM> may include an enlarged surface area to minimize bone damage. In an example, different shaped spikes may be used (e.g., flat, rectangular, triangular, round, etc.), such as to accommodate the patella or soft tissue. In an example, the shaft portion <NUM> of the spike <NUM> and a component used to secure or couple with the spike <NUM> (e.g., a robotic arm or components attached thereto) may have a combined thickness, average thickness, or maximum thickness similar to (e.g., within a tolerance of) or less than a femoral implant to be used. For example, the shaft portion <NUM> of the spike <NUM> and the component used to secure or couple with the spike <NUM> may have a size such that a patellar tendon is under natural tension when the spike <NUM> is used to apply force to the femur.

<FIG> illustrates a robotic soft tissue balancing system 600B including the spike <NUM> in accordance with some embodiments. The soft tissue balancing system 600B includes a robotic arm <NUM> to apply a force to the spike <NUM>. The spike <NUM> may apply the force to a femur <NUM>. The robotic arm <NUM> may include an end effector component <NUM> and a pin guide component <NUM>, which may be detachable. The robotic arm <NUM>, end effector component <NUM>, and pin guide component <NUM> may be those described above with respect to <FIG>. In an example, the pin guide component <NUM> attaches to the end effector component <NUM> to secure the spike <NUM> in place relative to the robotic arm <NUM>. The pin guide component <NUM> may be decoupled from the end effector component <NUM> to allow for removal of the spike <NUM>.

A force applied by the robotic arm <NUM> on the spike <NUM> may cause the femur <NUM> to move, putting ligaments in tension. As the ligaments are pulled by the force on the femur <NUM>, a balancing test may be performed. For example, tension in the ligaments may be measured or observed, force on the femur <NUM> may be tracked, or a rotation angle may be determined or observed. The rotation angle may then be used to set a target femoral rotation.

In an example, arrow <NUM> may represent a pull direction (e.g., force direction) that the spike <NUM> pulls the femur <NUM>. For example, the arrow <NUM> may point along a line parallel to a plane of a resection cut of the femur <NUM>. In an example, the arrow <NUM> may point along a line perpendicular to a plane formed by a top surface of the pin guide component <NUM> or perpendicular to an axis of the spike <NUM>.

<FIG> illustrates a soft tissue balancing component, including a condyle pivot <NUM> for use in a robotic soft tissue balancing system 700A in accordance with some embodiments. The condyle pivot <NUM> may be used to apply force to a femur. The condyle pivot <NUM> may include a shaft portion <NUM> to receive force and transfer the force via rigidity of the condyle pivot <NUM> to platform arms 705A-705B, which in turn may apply force on the femur. The condyle pivot <NUM> may include a hollow shaft, which may be perpendicular to the shaft portion <NUM>. The hollow shaft may be used to lock or secure the condyle pivot in place (e.g., to prevent rotation), such as relative to a robotic arm or component.

In an example, the platform arms 705A-705B of the condyle pivot <NUM> may include enlarged surface areas to minimize bone damage. In an example, different shaped platform arms 705A-705B may be used (e.g., flat, rectangular, triangular, round, etc.). In an example, the shaft portion <NUM> of the condyle pivot <NUM> and a component used to secure or couple with the condyle pivot <NUM> (e.g., a robotic arm or components attached thereto) may have a combined thickness, average thickness, or maximum thickness similar to (e.g., within a tolerance of) or less than a femoral implant to be used. For example, the shaft portion <NUM> of the condyle pivot <NUM> and the component used to secure or couple with the condyle pivot <NUM> may have a size such that a patellar tendon is under natural tension when the condyle pivot <NUM> is used to apply force to the femur.

The platform arms 705A-705B may each apply a same force or may apply different forces. For example, a torque may be applied to the condyle pivot <NUM> by the robotic arm <NUM> to keep the platform arms 705A-705B aligned along a plane, which may include varying force between the platform arms 705A-705B. When a limit is reached, for example, a first ligament is put in tension at a threshold level or a threshold force is reached, the relative forces applied on the platform arms 705A-705B may be used to determine a rotation angle to be used when resecting the femur <NUM> or when creating or inserting an implant. In another example, the platform arms 705A-705B may have equal force applied to each, and be allowed to rotate (e.g., away from an initial plane). The angle of the platform arms 705A-705B (e.g., relative to the initial plane) at an end position may be used to determine the rotation angle for later use. The end position may be determined when a threshold tension is reached on ligaments (e.g., a medial and a lateral ligament), when a threshold force is reached, or when a predetermined distance is reached (e.g., <NUM>, <NUM>, a distance corresponding to a tibia implant thickness such as <NUM>, <NUM>, <NUM>, etc.), which may include a safety factor (e.g., +/- <NUM>-<NUM>), or the like. In an example, a combination of end position markers may be used, such as a predetermined distance approximately equal to a tibia implant thickness (e.g., an insert (poly) or an implant assembly, which may be predetermined using planning techniques), while retaining a maximum force as safety factor. For example, when a maximum force is reached before the predetermined distance, the robotic arm may be stopped. In another example, balanced ligaments may be used to mark the end position. The threshold tension may be determined visually or using a sensor. The end position (e.g., when rotation stops) may be determined by optical navigation in an example.

<FIG> illustrates a robotic soft tissue balancing system 700B including the condyle pivot <NUM> in accordance with some embodiments. The soft tissue balancing system 700B includes a robotic arm <NUM> to apply a force to the condyle pivot <NUM>. The condyle pivot <NUM> may apply the force to a femur <NUM>, such as by pushing the femur <NUM> in a direction away from a tibia. For example, the condyle pivot <NUM> may use the platform arms 705A-705B to push on the femur <NUM> to apply the force. The robotic arm <NUM> may include an end effector component <NUM> and a pin guide component <NUM>, which may be detachable. The robotic arm <NUM>, end effector component <NUM>, and pin guide component <NUM> may be those described above with respect to <FIG>. In an example, the pin guide component <NUM> attaches to the end effector component <NUM> to secure the condyle pivot <NUM> in place relative to the robotic arm <NUM>. The pin guide component <NUM> may be decoupled from the end effector component <NUM> to allow for removal of the condyle pivot <NUM>.

A force applied by the robotic arm <NUM> on the condyle pivot <NUM> may cause the femur <NUM> to move, putting ligaments in tension. As the ligaments are pulled by the force on the femur <NUM>, a balancing test may be performed. For example, tension in the ligaments may be measured or observed, force on the femur <NUM> may be tracked, or a rotation angle may be determined or observed.

In an example, a pivot point of the platform arms 705A-705B may be at the shaft portion <NUM> of the condyle pivot <NUM>. The shaft portion <NUM> may be aligned, using the robotic arm <NUM>, at various points of the femur <NUM>. For example, the pivot point may be located at a medial condyle in a varus knee. In another example, pivot point may be the center of the knee. In yet another example, instead of using a spike as in <FIG> or a condyle pivot as in <FIG>, a posterior paddle, c-shaped adaptor, or other shape may be used to apply force to the femur <NUM>.

In an example, a device may be inserted into a joint, such that turning a screw of the device may allow the soft tissue balancing test to be performed. For example, the device may expand at the turn of the screw. In an example, the robotic arm <NUM> may turn the screw. In an example, a force sensor for detecting force on the tibia, on the femur, or between the tibia and the femur may be the eLIBRA soft tissue force sensor device from Zimmer Biomet of Warsaw, IN.

The example device illustrated in <FIG> is shown contacting a certain portion of a distal end of a partially resected femur. This is an exemplary engagement with the distal end of the femur, other examples may engage the femur in a different orientation or before or after resections. Additionally, in some examples, the platform arms 705A-705B may be contoured to facilitate engagement with the target bone surface.

In an example, arrow <NUM> may represent a pull direction (e.g., force direction) that the condyle pivot <NUM> pulls the femur <NUM>. For example, the arrow <NUM> may point along a line parallel to a plane of a resection cut of the femur <NUM>. In an example, the arrow <NUM> may point along a line perpendicular to a plane formed by a surface of the pin guide component <NUM> or a surface of the condyle pivot <NUM>, for example a surface in contact with the femur <NUM>.

According to the invention, the CAS controller <NUM> operates the robot arm <NUM> to perform a robotized soft-tissue balancing assessment, such as by using a processor to perform soft-tissue balancing <NUM>, although it may, in a non-claimed example, also be done without robotized assistance. Referring to <FIG>, with a device <NUM> anchored to the bone (such as a pin, a cutting block, etc.), the robot arm <NUM> is driven to pull on the bone and hence put the soft tissue under tension. Applied tension may be controlled using the signals from the force-torque sensors A in the robot arm <NUM> with the output of the force measurement <NUM>. In an embodiment, the device <NUM> includes a pin and a cutting block. The robot arm <NUM> pulls the femur away from the tibia by manipulating the pin of the device <NUM>, such that the pin (and femur) may rotate relative to the robot arm <NUM>. The rotation of the femur will naturally go toward soft tissue balancing, in which tension T1 is equal to tension T2. The device <NUM> may further include an inertial sensor to measure a rotation Θ indicative of the rotation required for soft tissue balancing. The rotation Θ is also monitored and measured by the robot arm <NUM>, with appropriate sensors (optical, encoders, inertial, etc). Referring to <FIG>, similar operations may be performed with the leg being in extension. <FIG> is a schematic view illustrating an intraoperative soft tissue assessment using a CAS system in knee extension in accordance with the invention. The robot arm <NUM> pulls the femur away from the tibia, either in extension or in flexion, and automatically stop. The robot arm <NUM> stops at a predetermined distance (gap), or, in non-claimed examples, when a threshold force or tension is reached, or at a user-selected stopping position. The predetermined distance (e.g., <NUM>, <NUM>, a distance corresponding to a tibia implant thickness such as <NUM>, <NUM>, <NUM>, etc.), may include a safety factor (e.g., +/- <NUM>-<NUM>), or the like. In an example, a combination of end position markers may be used, such as a predetermined distance approximately equal to a tibia implant thickness (e.g., an insert (poly) or the implant assembly, which may be predetermined using planning techniques), while retaining a maximum force as safety factor. For example, when a maximum force is reached before the predetermined distance, the robotic arm may be stopped. In another example, balanced ligaments may be used to mark the end position.

In <FIG>, the soft tissue is put under tension using the robot arm <NUM> acting on the device <NUM>. In an embodiment, the robot arm <NUM> raises the device <NUM> to displace the femur, while the tibia remains still by gravity or by its fixation to the table (e.g., when a foot support <NUM> is used), by a human (e.g., surgical assistant or the surgeon), by surgical tape, self-adherent wrap or tape, or other fixing devices or components to secure the tibia. It is also considered to use the laminar spreaders <NUM> of the robot arm <NUM>, as in <FIG>, to spread the bones apart. The laminar spreaders <NUM> may be inserted in the gap between the femoral condyles and the tibial plateau. In order to assist the laminar spreaders <NUM>, additional devices may be used and manipulated by the robot arm. For example, the spreaders <NUM> may manipulate a clamp to benefit from the leveraging of the clamp to apply a greater moment at the bones. Likewise, the spreaders <NUM> may manipulate a spreader with gear mechanism (planetary gear device, rack and pinion, etc), to assist in amplifying the force of the robot arm.

The processor may perform soft-tissue balancing <NUM> to quantify joint laxity to assist in the soft-tissue balancing at different moments during the surgical procedures operated by the CAS controller <NUM>. For example, the soft-tissue balancing <NUM> may assess soft-tissue balancing prior to having the robot arm <NUM> perform the alterations to the bone, to confirm the desired implant sizes and location on the bone produced by the implant assessment <NUM>, or to enable adjustments to the desired implant sizes and location on the bone, and impact the output of the resurfacing evaluator <NUM>. The soft-tissue balancing <NUM> may assess soft-tissue after cut planes have been made, to determine whether further adjustments are necessary.

In another embodiment, the output D is in the form of a patient-specific cut guide 3D file, for a patient-specific cut guide to be machined or 3D printed for operative use. For example, the patient-specific cut guide may have negative surfaces of the bone model for unique positioning on the bone, such that cut planes and drill guides are placed as planned. As another example, the output D may be a navigation file, of the type programmed into inertial sensor units manually navigated by an operator. Referring to <FIG>, similar operations may be performed with the leg being in extension.

In an example, the soft tissue assessment may be performed with the leg in flexion (e.g., as shown in <FIG>) or in extension (e.g., as shown in <FIG>). When in flexion, the leg may be held at a <NUM> degrees angle of flexion, or substantially <NUM> degrees, such as within plus or minus ten degrees. In another example, with the leg in extension, the leg may be held at zero degrees angle of extension, <NUM> degrees, <NUM> degrees, or the like, such as based on surgeon preference. The soft tissue assessment may be used to measure or display gap measurements for soft tissue balancing during a test when a knee is in flexion or extension. In an example, the soft tissue balancing assessment when the knee is in flexion may include not releasing the femur when pulling. In another example, the test may include pulling on the femur, then measuring an amount of rotation that results in balance between the soft tissue (e.g., ligaments). The femur may be free to rotate to find the balance based on the amount of force on the ligaments. In an example, the soft tissue balancing assessment may be performed with the patella in place or dislocated.

<FIG> illustrate a soft tissue balancing component, including a j-shaped adaptor <NUM> and a robotic arm <NUM> for use in a ligament pull system (shown in views 1000A-1000D) in accordance with some embodiments. The j-shaped adaptor <NUM> may attach to an end effector <NUM> on a distal end of the robotic arm <NUM>. In an example, the end effector <NUM> may be configured to receive the j-shaped adaptor <NUM> and lock the j-shaped adaptor <NUM> into place, secured to the robotic arm <NUM>. The attachment of the j-shaped adaptor <NUM> to the end effector <NUM> may result in an audible click. View 1000A illustrates the j-shaped adaptor <NUM> detached from the end effector <NUM> and view 1000B illustrates the j-shaped adaptor <NUM> coupled to the end effector <NUM>. View 1000C illustrates the j-shaped adaptor <NUM> attached to the end effector <NUM> in a configuration for performing a soft tissue balancing test on a lateral portion of a femur and view 1000D illustrates the j-shaped adaptor <NUM> attached to the end effector <NUM> in a configuration for performing a soft tissue balancing test on a medial portion of a femur. In another example, the j-shaped adaptor <NUM> may be configured to be reversible and lock into the end effector <NUM> at the same place in each direction, or in four directions (e.g., perpendicular to the lateral or medial views). In an example, the robotic arm <NUM> may apply a force to the j-shaped adaptor <NUM> to pull the j-shaped adaptor <NUM> in a direction while the j-shaped adaptor <NUM> is engaged with a femur. Pulling on the femur may allow the ligament pull system to determine a rotation angle for balancing the ligaments of the knee. In an example, the j-shaped adaptor <NUM> may be used to pull on the femur with the patella of the knee in place. In an example, the patella or soft tissue may be averted or in a normal position when doing the pull test in flexion.

A bone spike may be used to secure the j-shaped adaptor <NUM> to a bone. For example, the bone spike may be placed by a surgeon or using the robotic arm <NUM> at a predetermined location on the bone. The j-shaped adaptor <NUM> may be fitted around the spike with a spike adaptor anchor located at a distal end of the j-shaped adaptor <NUM>. The j-shaped adaptor <NUM> may be fitted around the spike using the robotic arm <NUM>, such as automatically, or using force sensing and surgeon input. The j-shaped adaptor <NUM> may then be used to apply a force on the bone (e.g., the femur) to pull the bone away form a second bone (e.g., the tibia) to conduct a soft tissue balancing test. The robotic arm <NUM> may apply the force on the j-shaped adaptor <NUM>, which then in turn applies the force on the bone spike, which then applies the force on the bone. The soft tissue balancing test may be performed with the patella or soft tissue in place (e.g., not dislocated) by using the j-shaped adaptor <NUM> to avoid the patella or soft tissue. For example, the j-shaped adaptor <NUM> may reach around the patella, but remain rigid when the force is applied on the j-shaped adaptor <NUM> by the robotic arm <NUM>, thus pulling the bone (e.g., the femur), while avoiding the patella. A straight component adaptor used instead of the j-shaped adaptor <NUM> may be interfered with by the patella and require dislocation of the patella. Performing the soft tissue balancing test with the patella in place may result in more accurate results than performing the soft tissue balancing test with the patella dislocated.

In an example, the robotic arm <NUM> may apply a force on the j-shaped adaptor <NUM> to cause the j-shaped adaptor <NUM> to pull on the bone spike until a threshold force is reached, a threshold tension in the soft tissue is reached, according to a preoperative plan, a surgeon stops the procedure, a predetermined distance is reached, or the like. The predetermined distance (e.g., <NUM>, <NUM>, a distance corresponding to a tibia implant thickness such as <NUM>, <NUM>, <NUM>, etc.), may include a safety factor (e.g., +/- <NUM>-<NUM>), or the like. In an example, a combination of end position markers may be used, such as a predetermined distance approximately equal to a tibia implant thickness (e.g., predetermined using planning techniques), while retaining a maximum force as safety factor. For example, when a maximum force is reached before the predetermined distance, the robotic arm may be stopped. In another example, balanced ligaments may be used to mark the end position. The j-shaped adaptor <NUM> may pull on the bone spike until a distance matching a preoperatively or intraoperatively known thickness of a tibial implant is reached. When the j-shaped adaptor <NUM> completes pulling, an angle of rotation of the bone may be recorded (e.g., by surgical planning software, a robotic controller, etc.) for later pin positioning or cut guide placement. In an example, the j-shaped adaptor <NUM> may include a horseshoe-shaped adapter (i.e., two j-shaped adaptors connected at their distal ends).

<FIG> illustrates a system <NUM> for testing soft tissue balance in extension in accordance with some embodiments. The system <NUM> may be used to measure or display gap measurements for soft tissue balancing during a test when a knee is in extension. For example, an extension gap test may include pulling on a tibia while a knee is in extension. In an example, a spacer block may be placed on a jig <NUM>, for example with shims or other flat thin surface inserted as the spacer block. For example, a flat attachment may be slid on the jig <NUM> to perform the test. The jig <NUM> may be attached to a robotic arm <NUM>, which may cause a force to be imparted onto the flat attachment via the jig <NUM>. The force may be imparted onto the tibia to pull the tibia away from the femur. In an example, the flat attachment may include one or more feet that may clip into a slot of the jig <NUM>. The jig <NUM> may be used to assess the extension gap and to test varus/valgus angles. In an example, the soft tissue balancing test may be performed at a specified varus/valgus angle. Releases may be performed at that angle until the ligaments are balanced. The ligament balancing may be performed by measuring tension (e.g., by measuring force) within a component, such as using a sensor.

In another example, the soft tissue balancing test when the knee is in extension may include using a plate fixed to the tibia to pull on the tibia. The torque may be measured (e.g., using a sensor) to determine an amount of imbalance. In an example, the test may be performed by a plate that is free to rotate. The free rotation plate may be used to apply force on the tibia until the varus/valgus angles are zero to find a balance. In an example, the jig <NUM> may include a spacer block. The spacer block may widen to apply tension to perform a ligament balance test.

<FIG> illustrates an example user interface <NUM> for displaying ligament balance in accordance with some embodiments. The user interface <NUM> includes a medial tension indication <NUM> and a lateral tension indication <NUM>. In the example shown in user interface <NUM>, the medial tension represented in indication <NUM> is less than the lateral tension represented in indication <NUM>. This indicates that the lateral tension should be decreased, such as by performing a release on the lateral ligaments. In an example, lateral tension may include tension between compartments, such as lateral and medial compartments, or collateral ligaments (e.g., medial and lateral collateral ligaments) as an example to differentiate the medial and lateral sides. In another example, all ligament complexes play a role in the balance of the knee, and thus may be balanced. The ligaments may include a medial collateral ligament (MCL), a lateral collateral ligament (LCL), a posterior cruciate ligament (PCL), posterior capsule, etc..

In an example, the difference displayed in the user interface <NUM> between the two ligaments may include a difference in force, a difference in torque, or a difference in displacement between the two ligaments. As releases are performed, the user interface <NUM> may be updated in real time to display updated differences. For example, a release may be performed on the lateral ligament in the example shown for user interface <NUM>, which may cause the balance between the medial and lateral ligaments to become closer to even. In an example, a robotic arm may apply a constant force on a bone to allow a surgeon to perform the ligament releases while watching the extension ligament balance in real time. In another example, a robotic arm may be used to perform the ligament releases. The process may be iterated until the ligament balance is achieved.

<FIG> illustrates a force diagram <NUM> illustrating a technique for determining medial and lateral forces in accordance with some embodiments. The force diagram <NUM> illustrates measurements of forces acted on a tibia <NUM> by an end effector <NUM> of a robotic arm <NUM> during a soft tissue balancing test. In an example, a robotic force FRBT is applied by the end effector <NUM> on the tibia <NUM>. Opposite forces are applied by the tibia <NUM>, which may be effectively labeled a medial force FMCL and a lateral force FLCL. The forces are balanced according to Eq. <NUM> below: <MAT>.

The moment of force (or torque) applied by the robotic arm <NUM> may be known using a force or torque sensor, such as between the end effector <NUM> and the robotic arm <NUM>. The moment may be labeled MRBT and may be balanced by moments of equal and opposite torque at medial and lateral distances (labeled LMCL and LLCL) from the MRBT moment to the medial force and the lateral force according to Eq. <NUM> below: <MAT>.

The lateral and medial distances may be known using a tracking system, such as an optical tracking system, using known dimensions of the end effector, or using sensors attached to components of the system. Using the known FRBT and MRBT and the known distances, Eqs. <NUM> and <NUM> may be solved for the FMCL and the FLCL. These two forces may be used to determine balance in soft tissue, such as the medial collateral ligament and the lateral collateral ligament. The two forces may be output on a display device or user interface, such as those shown in <FIG> or <FIG> below or <FIG> above.

<FIG> illustrates a laminar spreader advantage embodiment <NUM> of a soft tissue balancing test in accordance with some embodiments. <FIG> illustrates a gear advantage embodiment <NUM> of a soft tissue balancing test in accordance with some embodiments. <FIG> illustrates a long lever arm advantage embodiment <NUM> of a soft tissue balancing test in accordance with some embodiments. In some cases, a robotic arm may not be able to apply sufficient force to separate the femur and tibia or perform a soft tissue balancing test. To increase the force applied by the robotic arm, a mechanical advantage may be used. For example, the laminar spreader advantage embodiment <NUM> illustrates a laminar spreader <NUM> to apply additional support while the robotic arm <NUM> applies a force at <NUM> (e.g., using a bone spike as described herein) on a femur <NUM> to separate the femur <NUM> from a tibia <NUM>. In the example shown in <FIG>, force may be applied to the laminar spreader <NUM> by a surgeon (or surgical assistant) or by another robotic arm.

In the example shown in <FIG>, the gear advantage embodiment <NUM> uses a robotic arm <NUM> affixed to a gear <NUM> to apply a torque on a second gear <NUM> to move a pivot joint <NUM> to cause a first spreader arm <NUM> to separate from a second spreader arm <NUM>, the first spreader arm <NUM> applying a force on a first bone and the second spreader arm <NUM> applying a force on a second bone. The gear advantage embodiment <NUM> relies on the additional torque of the gears <NUM> and <NUM> to increase the output force of the robotic arm <NUM>. In the example shown in <FIG>, a robotic arm applies force to a laminar spreader <NUM> with long lever arms to separate a femur <NUM> from a tibia <NUM>. The torque applied by the robotic arm is increased via the long lever arms.

<FIG> are user interfaces for displaying a range-of-motion (ROM) analysis of a CAS controller in accordance with some embodiments. <FIG> are user interfaces for displaying an implant assessment of a CAS controller, enabling implant movement from a caudal viewpoint in accordance with some embodiments. <FIG> are user interfaces for displaying an implant assessment of a robotized surgery controller, enabling implant movement from a frontal viewpoint in accordance with some embodiments.

Referring to <FIG>, a graph illustrating an actual varus/valgus balanced line <NUM> as a function of the leg extension is shown, as a result of the controlled movements of the foot support <NUM>. The force measurement data allows the positioning of <NUM>, as an indication of the varus/valgus value at balanced soft tissue. Lines <NUM> and <NUM> respectively show the valgus and varus values at maximum allowable soft tissue tension, as a result of the lateral movements depicted in <FIG>, as measured by the force measurement <NUM>. The graph of <FIG> is the ROM analysis, done preoperatively or post-operatively.

A similar graph may be produced by the implant assessment <NUM>, to illustrate the impact of given implants at a given location on the bones. However, as shown in <FIG> and <FIG>, the model of the implant I may be rotated by an operator, with angle values being instantly updated. As a result of such virtual adjustments, the varus/valgus balanced line <NUM> may shift to reduce the valgus as in 60A (<FIG>) or to reduce the varus as in 60B (<FIG>). An operator or a processor performing the implant assessment <NUM> may therefore perform such adjustment in order to bring the balanced line <NUM> closer to a neutral varus/valgus through as much of the leg extension as possible.

Referring now to <FIG>, <FIG>, <FIG>, and <FIG>, a surgical workflow that may be operated with the CAS system <NUM> is described, with reference to GUIs <NUM>-<NUM>. The expression GUI is used in the plural to indicate a variation of GUI pages in the surgical workflow. The surgical workflow may be the output D produced by the processor of the CAS controller <NUM>.

Referring to <FIG>, GUI <NUM> is provided to guide an operator during calibration (also known as registration) of the bones for subsequent tracking. The calibration is performed so as to position the limbs in a universal X, Y, Z coordinate system. The origin and orientation of the X, Y, Z coordinate system may be arbitrary, or may be fixed to the OR table or any other structural point, or may be even fixed to a bone of the patient. In the example of <FIG>, <FIG>, <FIG>, and <FIG> for total knee replacement, the femur and the tibia of the patient are to be tracked, whereby their position or orientation (i.e., their location) in the coordinate system must be set. The GUI may provide a visual display of the femur, with animation to suggest movements to be performed during the calibration. According to an embodiment, the femoral head center is determined using the processor to perform a ROM analysis <NUM> to record a plurality of femur positions and orientations, essentially forming a sphere whose center is that of the femoral head. In an embodiment, the points are acquired when the femur is moved in a conical pattern, for example manually. The GUI <NUM> may guide the operator in indicating the number of positions required, and in confirming that a suitable number of points have been acquired. The GUI <NUM> may then request that a plurality of known landmarks be digitized with a tracked digitizer tool (e.g., a tracked pointer, wand, or the registration tool described with respect to <FIG> below), such as the mechanical axis entry point, the medial epicondyle, the lateral epicondyle, the anterior and posterior Whiteside's lines, the anterior cortex, or the medial and lateral condyles. The acquisition of these points may enable the generation of a cloud of points or surface model that may be matched or merged with the bone model B of the femur (<FIG>), via the ROM analysis <NUM>. Hence, at the outset of the steps directed by GUI <NUM>, the femur is tracked in the coordinate system.

Referring to <FIG>, GUI <NUM> is also provided to guide an operator during calibration (also known as a registration), but for a second bone, i.e., the tibia, to locate the tibia in the X, Y, Z coordinate system. The GUI <NUM> may request that a plurality of known landmarks be digitized with a tracked digitizer tool, such as the malleoli, the tibial mechanical axis entry point, points on the medial plateau and on the lateral plateau, or other points such as the medial <NUM>/<NUM> of tuberosity. Although not shown, the GUI <NUM> could suggest that a pivoting motion of the tibia relative to the femur be done to record the movement via the tracking device <NUM> and use the information to determine a mechanical axis of the tibia. As observed from <FIG>, the GUI <NUM> may provide assistance by visual showing the regions of the tibia and fibula in which points are to be digitized. The acquisition of these points may enable the generation of a cloud of points or surface model that may be matched or merged with a bone model B of the tibia (<FIG>), via the ROM analysis <NUM>. Hence, at the outset of the steps directed by GUI <NUM>, the femur and tibia are tracked in the coordinate system.

Referring to <FIG>, GUI <NUM> is used to guide the gathering of range-of-motion data of the tracked limbs, tracked in the coordinate system pursuant to the steps performed using GUIs <NUM> and <NUM>. In an embodiment, the GUI <NUM> guides a human operator, such as a surgeon or medical professional, in determining the limits of the range of motion and of joint laxity, based on force felt by the operator, as an alternative to using the force feedback capability of the robotized version of the system <NUM>. According to <FIG>, a lateral leg display <NUM> may be provided to visually illustrate the limits of flexion and extension, with related angle. The operator manually displaces the tibia relative to the femur between maximum (flexion) and minimum (extension) angles, and the tracking of the tibia and femur by the tracking device <NUM> allows the processor to record these angles for use in the ROM analysis <NUM>. The operator may assist in determining the maximum and minimum angle, by judging when to stop the extension and flexion based on the resistance felt. The leg display <NUM> may present the measured data in different forms, using for instance a movement arch 121A to visually show the range of movement. A ROM bar 121B may also be provided, showing the numerical values of angle, including a median angle. When the extension angle value is outside of standards, the ROM analysis <NUM> may identify potential flexion contracture to influence the resection planning to remedy this issue. When the overall range of motion is below acceptable standards, the ROM analysis <NUM> may identify this condition to influence resection planning and implant selection.

According to <FIG>, a frontal leg display <NUM> may also be provided in GUI <NUM> to visually illustrate the varus/valgus angles at extension and flexion. In a first step, the operator manually extends the leg, to then pivot the tibia relative to the femur to maximum varus and valgus angles, and the tracking of the tibia and femur by the tracking device <NUM> allows the ROM analysis <NUM> to use these angles. The maximum varus/valgus angles may be determined by the operator's judgement as to when to stop the extension and flexion based on the resistance felt. The frontal leg display <NUM> may provide the data in different forms, using also for example a movement arch 122A to visually show the range of movement, and an extension varus/valgus bar 122B, showing the numerical values of varus and valgus.

Then, according to <FIG> and using the same or another fontal leg display <NUM> and movement arch 122A, the operator manually flexes the leg, to then pivot the tibia relative to the femur to maximum varus and valgus angles, and the tracking of the tibia and femur allows the ROM analysis <NUM> to use these angles. A flexion varus/valgus bar 122C may then show the numerical values of varus and valgus. These values are recorded for subsequent use by the processor in performing the soft tissue balancing <NUM>. Moreover, these values may indicate a loose or tight knee condition, laterally or medially, whether it be correctable by implant positioning or not. In the latter case, the system <NUM> may suggest ligament releasing to remedy the condition. The soft tissue balancing <NUM> may identify such a condition by being programmed with acceptable varus/valgus angle ranges. The varus/valgus angles obtained may be representative of the laxity of the medial and of the lateral collateral ligaments, as these ligaments delimit knee laxity. When the posterior and the anterior cruciate ligaments have not been resected (e.g., in a cruciate retaining surgery), these ligaments may also affect laxity. The knee articular capsule and the patellar tendon may also affect joint laxity.

Referring to <FIG>, an enlarged joint display <NUM> may also be provided to visually illustrate the anterior and posterior drawer distances at flexion. To gather the information, with the leg flexed, the operator manually pushes and pulls the tibia relative to the femur to maximum posterior and anterior positions, and the tracking of the tibia and femur by the tracking device <NUM> allows the ROM analysis <NUM> to use the drawing positions, relative to a neutral position at which the tibia is natively positioned relative to the femur by soft tissue tension. Again, the maximum distances may be determined by the operator's judgement as to when to stop the pushing and pulling based on the resistance felt. The joint display <NUM> may have different forms, using a distance scale 123A to visually show the range of movement, and a distance bar 123B, showing the numerical values of varus and valgus. These values are recorded for subsequent use during the soft tissue balancing <NUM>. Joint displays 123A and 123B may also indicate a target laxity (for comparison) which is programmed to reflect the ideal laxity. The ideal laxity may be based on a surgeon-defined preference or suggested value from literature.

Therefore, at the outset of the surgical workflow steps guided by GUI <NUM>, the system <NUM> has recorded joint laxity data. The recorded information may be based on force feedback felt by the surgeon manipulating the tibia relative to the femur, or may be the result of manipulations by robotized components using sensors A and output by the force measurement <NUM> when the robotized components are programmed to limit force values. The recorded range of motion and joint laxity information may include maximum flexion angle, maximum extension angle, range of motion, varus and valgus angle values at extension, at flexion, or at any desired angle, anterior drawer distance, posterior drawer distance. The recorded information may be as a function of 3D bone models B of the tibia and femur, or of other bones in different surgical procedures. The order of information gathering using the GUI <NUM> may be changed from the order described above.

<FIG> illustrate graphical user interfaces (GUIs) 2200A and 2200B, which may be used for displaying flexion/extension angle, gaps, varus and valgus angles of a knee in accordance with some embodiments. The GUIs 2200A and 2200B include a video component <NUM> to display real-time range of motion. The GUIs 2200A and 2200B include one or more graphical information components. For example, GUI 2200A shows the varus/valgus angle <NUM> at <NUM> degrees varus in the medial direction at an flexion angle <NUM> of <NUM> degrees (from full extension at <NUM> degrees). GUI 2200B shows the varus/valgus angle <NUM> at <NUM> degrees varus in the medial direction at an flexion angle <NUM> of <NUM> degrees (from full extension at <NUM> degrees). Additional information is shown at graphical information component <NUM> in the GUIs 2200A and 2200B. The graphical information component <NUM> includes gap information, varus/valgus angle information, range of motion information, and extension/flexion information. The range of motion information may be used to create a preoperative plan.

In an example, one or more of the GUIs 2200A or 2200B may provide a remote video or allow for a remote audio connection, such as with a remote surgeon. The remote video or remote audio may be a real-time connection to allow the remote surgeon to discuss a procedure or provide training with a local surgeon or to monitor the local surgeon. A GUI used by the remote surgeon may provide the remote surgeon with a video display of a surgical field operated by the local surgeon.

Referring to <FIG> and <FIG>, GUI <NUM> is used for the planning of the implant positions and orientations, taking into consideration joint laxity and range of motion as obtained using GUI <NUM>. The GUI <NUM> receives output from the implant assessment <NUM> and from the soft tissue balancing <NUM>. The GUI <NUM> may have a joint display <NUM> showing bone models B with implant models C. The joint display <NUM> may include a view of the knee in extension (<FIG>) and a view of the knee in flexion (<FIG>). According to an embodiment, the user of GUI <NUM> may toggle between flexion and extension views, and may also toggle between frontal (<FIG> and <FIG>), sagittal or axial planes of view, on preference. The initial or proposed location of the implant models C relative to the bone models B may be determined by the implant assessment <NUM> using the joint laxity data output by the soft tissue balancing <NUM>. The current location may be quantified using different markers, such as those described below. Joint-line variation plane 131A may display the pre-operative joint line versus the proposed joint line or the current joint line (i.e., actual location, as modified) when an operator varies the location of either one of the implant models C. Lateral laxity scale 132A and medial laxity scale 132B may provide a visual indication of the acceptable lateral and medial soft tissue tension. In <FIG> and <FIG>, the acceptable range is indicated by upper and lower limits, along with a pointer indicating the tension at the current implant locations. The scales 132A and 132B may also provide gap distances, current femur and tibia varus/valgus angles, and an anterior gap for patellofemoral joint stuffing as additional data representative of joint laxity. The gap distances may be the sum of planned resection and ligament laxity compared to implant thickness. According to an embodiment, the laxity scales 132A and 132B dynamically reflect modifications to the planned implant location. The adjustments on the laxity scales 132A and 132B may be reflected by the graphs shown in <FIG> and <FIG>, as a function of a rotation of the implant. A femoral component window <NUM> may enable the change of femoral implant size. The user may have the possibility of changing implant sizes, in which case the displayed femoral implant model and related information on the joint display <NUM> may be updated (131A, 132A, 132B, etc.). A spacer component window <NUM> may enable the selection of the spacer thickness or the type of spacer. Changes to the spacer component may result in a dynamic update of the joint display <NUM> and of related data (131A, 132A, 132B, etc.). A tibial component window <NUM> may enable the change of tibial implant size, with the user given the option of changing implant sizes, in which case the displayed tibial implant model and related information on the joint display <NUM> may be dynamically updated (131A, 132A, 132B, etc.). A location control panel <NUM> is provided for the user to modify the location of the femoral component relative to the femur, in translation or location. As the location is modified using the location control panel <NUM>, the joint display <NUM> may be updated and applicable data is also adjusted, such 131A, 132A, 132B, etc. Alternatively or additionally, the implants in the joint display <NUM> may be widgets that may be moved around relative to the bone models B, with the consequential dynamic adjustment of applicable data (e.g., 131A, 132A, 132B). The widget feature may be available in all views. It has the same function whether it is overlaid on the knee or on the left panel of GUI <NUM>: it allows the user to position/orient the implant with respect to the bone. The effect of changing position or orientation of the implant will be dynamically reflected in the laxity scales. The laxity scales will be different in flexion and extension. The laxity scales could be provided throughout all angles of flexion.

Accordingly, the processor may perform the implant assessment <NUM> or the soft tissue balancing <NUM>, and may propose implant components and locations for the implant components via the GUI <NUM>. The GUI <NUM> gives the possibility to an operator to modify the implant components or their locations, by dynamically updating in real-time quantitative data related to joint laxity and range of movement, to assist the operator is finalizing the resection planning. When the implants are selected and their locations are set, the information of the GUI <NUM> is converted into another form of the output D, such as personal surgical instrument tool files or data to perform resection as decided, a navigation file for the robot arm <NUM> when present, or a navigation file for tracked tools. The GUI <NUM> may also be used post-resection, to provide the joint laxity data for the "as-resected" state. The data may be used to document the surgical procedure. This may also allow post-resection corrections when deemed necessary. It may be required to return to GUI <NUM> or <NUM> to recalibrate the bones to obtain more precision in the assessment.

<FIG> illustrates a tibial force detection system <NUM> in accordance with some embodiments. The tibial force detection system <NUM> includes a tibial baseplate <NUM> including one or more force detection components. In an example, the tibial baseplate <NUM> includes four force detection components, corresponding to four quadrants, which are labeled in <FIG> as quadrants 'A', 'B', 'C', and 'D'. The quadrants may be divided such that each quadrant is moveable independently in at least one axis relative to the other quadrants. For example, dividing line <NUM> illustrates a separation between quadrants B and C, such that quadrants B and C may be compressed or decompressed relative to each other. The force detection components may be located within the quadrants (e.g., within the tibial baseplate <NUM> (e.g., underneath a first layer shown in <FIG>). As a quadrant is compressed or decompressed, the force detection component corresponding to that quadrant may include a sensor to detect the compression force (or measure a decompression force or change in force). In another example, the quadrants may be immovable relative to each other, while still including corresponding force detection components to measure force in each quadrant independently. In yet another example, the tibial baseplate <NUM> may be divided into halves, with each half including a corresponding force detection sensor and being moveable relative to the other half. In yet another example, further subdivisions may be made of the tibial baseplate <NUM> including corresponding force detection components and independent movement (e.g., six, eight, etc., radial slices of the tibial baseplate <NUM>). The force detection components may be used to obtain data regarding force imparted on the tibial baseplate <NUM> intraoperatively.

In an example, the knee may be opened and a navigated tibial cut may be made. In an example, variances in the tibial cut may be related to a depth of the cut, which may be relatively standard for most surgeons taking reference from either the high or low tibial plateau. Once the tibial cut has been made the tibial force detection system <NUM> may be placed. The tibial force detection system <NUM> may include a tibial baseplate and a polyethylene trial combination. The tibial force detection system <NUM> may expand medially and laterally, such as to accommodate various sized knees. In an example, the tibial force detection system <NUM> may have a medial or lateral tilting hemi-plateau with the ability to rise and fall all four quadrants independently. The displacement up and down and the force experienced by each quadrant may be measured, such as electronically or hydraulically using a sensor. In an example, the tibial force detection system <NUM> may be an active device such that upward or downward movement may be measured as the knee (e.g., before femoral cuts are performed) is put through a range of motion test. In an example, measuring the movement during the range of motion test may be performed while tracking the patella. In an example, varus or valgus forces may be applied, such as by a robotic arm on the knee or by a surgeon through a range of motion (e.g., the entire range or a predetermined interval, such as <NUM>, <NUM>, <NUM>, <NUM> degrees, or as performed by the surgeon). The sequence may be repeated with a prestress test to better appreciate the knee mechanics, for example, after correction for a lax medial collateral ligament (MCL) or lateral collateral ligament (LCL). In an example, the sequence may be repeated after the femoral cuts have been made or after the femoral trial is seated to provide an opportunity for further improvements to the trial or to optimize soft tissue balancing.

In an example, when a knee requires soft tissue releases, the releases may performed in a staged and sequential fashion and a re-assessment of the improved kinematics may be performed, for example, after each intervention. This process allows a quantification of knee kinematics during different measurement points intraoperatively. The quantifications may be used to balance the soft tissue more accurately than previous techniques. The quantifications may be saved to a database, such as for modeling, machine learning to predict outcomes in future cases, or the like. In an example, an indication may be provided to a surgeon regarding useful releases for a particular patient. In another example, an indication of femoral component sizing AP, location AP, or rotation may be provided to improve flexion/extension gaps throughout the range <NUM> to <NUM> degrees, which may include accounting for a location of the patella by using the patella tracking.

In an example, a robotic arm may be used to assess bone quality. Using the assessed bone quality, a system may determine whether to use bone cement or to stem a patient when placing an implant, such as the tibial baseplate <NUM>. In another example, the tibial baseplate <NUM> may be hydraulically powered. The hydraulic power may be used to cause the tibia or femur to rotate to a tension rotation angle automatically. The angle may be recorded, such as by using sensors within the tibial baseplate <NUM>. The tibial baseplate <NUM> may be used to expand the gap between the tibia and the femur.

<FIG> illustrate a patella sensor <NUM> of a range of motion testing system in accordance with some embodiments. A first view 2500A illustrates a side view of a patella <NUM> with the patella sensor <NUM>, including relative placement of the patella <NUM> with respect to a femur <NUM> and a tibia <NUM>. A second view 2500B illustrates a back view of the patella <NUM> with the patella sensor <NUM>.

In an example, the patella sensor <NUM> may be placed on the back of the patella <NUM>, for example prior to an incision or bone cut. The patella sensor <NUM> may be used to determine patella position during a range of motion test. For example, the patella sensor <NUM> may include an accelerometer, a magnetometer, a gyroscope, an RFID chip, an optical tracking sensor, or other location sensor. In an example, the patella sensor <NUM> may be located around the periphery of the patella <NUM>, for example to detect and output the outline of the patella <NUM>. In another example, a size of the patella <NUM> may be measured (e.g., via preoperative or intraoperative imaging or direct measurement), and a position of the patella sensor <NUM> relative to the patella <NUM> may be known, allowing a location of the entirety of the patella <NUM> to be known.

The location of the patella <NUM> may be used during a surgical procedure, such as a knee replacement. During a knee replacement procedure, a robotic arm may be used to perform aspects of the procedure. The robotic arm may use the detected location of the patella <NUM> (from the patella sensor <NUM>) to perform a patella cut or to avoid the patella while making other cuts. In an example, the patella sensor <NUM> may be a passive sensor. In an example, a tracking assembly may be used, such as that described in <CIT>.

<FIG> illustrate augmented reality systems for control of a robotic arm <NUM> in accordance with some embodiments. <FIG> include two example embodiments. The augmented reality systems use virtual components to control real world objects. An augmented reality (AR) device allows a user to view displayed virtual objects that appear to be projected into a real environment, which is also visible. AR devices typically include two display lenses or screens, including one for each eye of a user. Light is permitted to pass through the two display lenses such that aspects of the real environment are visible while also projecting light to make virtual elements visible to the user of the AR device.

Augmented reality is a technology for displaying virtual or "augmented" objects or visual effects overlaid on a real environment. The real environment may include a room or specific area (e.g., a surgical field), or may be more general to include the world at large. The virtual aspects overlaid on the real environment may be represented as anchored or in a set position relative to one or more aspects of the real environment. For example, a virtual robotic arm <NUM> of <FIG> may be displayed in a set location of a surgical field, to be controlled by a surgeon using an AR device. An AR system may present virtual aspects that are fixed to a real object without regard to a perspective of a viewer or viewers of the AR system (e.g., the surgeon <NUM>). For example, the virtual object <NUM> of <FIG> may be configured to appear to be an offset distance away from the robotic arm <NUM>. In an example, virtual objects may appear to have a degree of transparency or may be opaque (i.e., blocking aspects of the real environment).

A surgeon may control the virtual robotic arm <NUM> by interacting with the virtual robotic arm <NUM> (e.g., using a hand to "interact" with the virtual robotic arm <NUM> or a gesture recognized by a camera of the AR device). The virtual robotic arm <NUM> may then be used to control the robotic arm <NUM>. For example, the surgeon may move the virtual robotic arm <NUM> and the robotic arm <NUM> may move correspondingly.

In the example shown in <FIG>, one or more virtual control arms (e.g., <NUM> or <NUM>) may be used to control movement of the robotic arm <NUM>. For example, a surgeon may move the virtual control arm <NUM> to cause the robotic arm <NUM> to move in a corresponding fashion. Using more than one virtual control arm may allow for independent degrees of freedom in controlling the robotic arm <NUM>. For example, a surgeon may rotate his or her hand to virtually "twist" the virtual control arm <NUM>, which may cause an end effector of the robotic arm <NUM> to rotate, without translating the robotic arm <NUM>. Similarly, the virtual control arm <NUM> may be moved to cause the robotic arm <NUM> to translate without rotating.

In an example, aspects of the robotic arm <NUM> may be controlled by pressing one or more virtual buttons that may appear virtually overlaid in a real environment. For example, a button may be displayed virtually to cause the robotic arm <NUM> to move to a first position to aid in performing or to perform a surgical technique. Using the virtual button allows the surgeon to remain in place without needing to turn or avert his or her vision to a display device. This allows the surgeon to maintain focus on the surgical field and monitor the robot, as well as reducing time for the procedure.

In an example, using virtual control elements (e.g., <NUM>, <NUM>, or <NUM>) to control the robotic arm <NUM> to perform a procedure may avoid the use of force sensing. For example, instead of controlling the robotic arm <NUM> using force sensing when a surgeon moved the robotic arm <NUM>, the robotic arm <NUM> may respond to movements of the virtual control elements. In another example, force sensing may be used in addition to the augmented reality elements described above. For example, force sensing may be used to communicate information to a system using the robotic arm. For example, tapping on the robotic arm <NUM> may cause the robotic arm <NUM> to lock in place, confirm actions, deny actions, etc. In another example, information may be communicated using virtual buttons as described above. Using the virtual control elements may allow the robotic arm <NUM> to be driven in an active mode throughout a procedure, instead of having non-active modes or locations where the active mode is disabled.

<FIG> illustrates a system <NUM> for distracting a femur from a tibia in accordance with some embodiments. The system includes a leg holder <NUM> connected to a support structure <NUM> via a support device <NUM>, the leg holder <NUM> supporting a patient's knee <NUM>. The support device <NUM> may include a force applicator, such as a hydraulic device, motor, etc., to apply pressure under the femur, for example while the leg is under extension. In another example, the support device <NUM> may be connected to a robotic arm, which may be used to apply a force.

<FIG> illustrates a robotic arm registration system <NUM> in accordance with some embodiments. The robotic arm registration system <NUM> includes a robotic arm <NUM>, an end effector <NUM> attached to a distal end of the robotic arm <NUM>, and a landmark registration identifier <NUM> attached to the end effector <NUM>. The landmark registration identifier <NUM> may be used to automatically identify landmarks by using the robotic arm <NUM> to navigate to different points of a patient's anatomy. For example, the robotic arm <NUM> may be connected to a system that may track the robotic arm <NUM> or the patient's anatomy. Using tracking data, the robotic arm <NUM> may navigate the patient's anatomy to automatically find and tag points using the landmark registration identifier <NUM>. In an example, the landmark registration identifier <NUM> may include a claw tool to register landmarks at angles that may otherwise be difficult to reach with a straight tool.

<FIG> illustrates a flow chart showing a technique <NUM> for using a robotic arm to perform soft tissue balancing in accordance with some embodiments. The technique <NUM> includes an operation <NUM> to apply a force to a bone of a patient joint using a robotic arm. The technique <NUM> includes an operation <NUM> to measure the force to capture data indicative of soft tissue tension in the patient joint. The technique <NUM> may include an operation to track, using a processor, movement of the robotic arm, which may include capturing tracking data. The technique <NUM> includes an operation <NUM> to determine soft tissue tension at the patient joint based on the force data. The soft tissue tension may be determined using the tracking data. The technique <NUM> may include an operation to output the soft tissue tension. The technique <NUM> may include receiving patella location information from a sensor affixed to a back side of the patella. The technique <NUM> may include outputting the patella location information during a range of motion test. The technique <NUM> may include controlling the robotic arm using a virtual component displayed using an augmented reality device. In an example, tracking aspects of the patient's anatomy may be performed using a pneumatic cuff sensor on the patient's anatomy. In an example, the bone may be a tibia or a femur.

<FIG> illustrates a flow chart showing a technique <NUM> for using a robotic arm to perform a soft tissue pull test in accordance with some embodiments. In an example, the technique <NUM> includes an operation <NUM> to resect a distal femur and an operation <NUM> to resect a proximal tibia. In an example, the technique <NUM> includes an operation <NUM> to perform a soft tissue balancing test, such as a ligament test while a joint connecting the femur to the tibia is in extension. Operation <NUM> may be performed with spacer component or a shim device to put the joint under tension. After operation <NUM>, the technique <NUM> may include performing a release, such as of a ligament or a tendon. The technique <NUM> includes an operation <NUM> to insert a soft tissue balancing component, such as a spike, condyle pivot, j-shaped adapter, or the like. Once inserted, the soft tissue balancing component may be used to perform a pull test, such as when the joint is in flexion to determine a rotation required to balance ligaments in the joint.

The technique <NUM> includes an operation <NUM> to use the determined rotation to calculate pin placement for a cut guide (e.g., a <NUM>-in-<NUM> cut guide) to obtain a desired or predetermined femoral component rotation. Operation <NUM> may be performed by a processor, such as using surgical procedure planning software to provide instructions to the processor. The technique <NUM> includes an operation <NUM> to output pin placement locations or to place pins for the cut guide. The technique <NUM> includes an operation <NUM> to perform cuts using the placed cut guide. In an example, a tibial cut may be performed, optionally after operation <NUM> or before operation <NUM>. In an example, any one or more of operations <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or the tibial cut may be performed using a robotic arm. In another example, the technique <NUM> may include an operation to output a pin placement using the rotation angle for updating a preoperative plan intraoperatively. The output pin placement be used instead of preoperative pin placement locations, or an average or weighted average may be used.

In an example, the technique <NUM> may include an optional operation <NUM> to apply a force to a bone, such as the femur or the tibia, to perform a soft tissue balancing test, using an end effector of a robotic arm, which may apply a force to the soft tissue balancing component. In an example, the technique <NUM> may include an optional operation <NUM> to output information about soft tissue balance. In another example, the technique <NUM> may include applying a force to the femur or the tibia using the soft tissue balancing component without the use of a robotic arm.

<FIG> illustrates a flow chart showing a technique <NUM> for performing robot-aided surgery using tracking in accordance with some embodiments. The technique <NUM> includes an operation <NUM> to track movement of a bone using a tracking system, such as an optical tracking system. The tracking system may include a first tracker affixed to a bone of a patient. In an example, the tracking system includes a second tracker affixed to a second bone of the patient. In an example, the tracking system includes a third tracker affixed to a robotic arm. The technique <NUM> may include receiving tracking information from the tracking system including position or orientation information for the third tracker affixed to a portion of the robotic arm. The tracking position or orientation of the robotic arm may be used to track an end effector located at a distal end of the robotic arm, at least in part, using the position and orientation information from the second tracker.

The technique <NUM> includes an operation <NUM> to monitor a position and orientation of an end effector coupled to the end of a robotic arm, for example using a robotic controller. The technique <NUM> includes an operation <NUM> to move the robotic arm to a soft tissue balancing test position and orientation relative to the bone. The technique <NUM> includes an optional operation <NUM> to control the robotic arm to retain the position and orientation relative to the bone when the bone moves, for example using the robotic controller. The optional operation <NUM> may include receiving an indication of movement of the bone from the tracking system. The technique <NUM> includes an operation <NUM> to apply a force to the bone using an end effector of the robotic arm. The technique <NUM> includes an optional operation <NUM> to track a position and orientation of the end effector when moved by the robotic controller.

The technique <NUM> includes an operation <NUM> to determine soft tissue balance using the position and orientation of the end effector or information from the tracking system, such as a position of the first tracker affixed to the bone. In an example, determining the soft tissue balance may include using force information from a force sensor coupled between the end effector and the robotic arm. The technique <NUM> may include an operation to identify manual movement of the end effector using a force sensor and allowing the manual movement of the end effector relative to the bone. In an example, the end effector may be coupled to a distal end of a bone spike after the bone spike is coupled to the bone. The technique <NUM> may include an operation to output the soft tissue balance, such as for display on a user interface.

The technique <NUM> may include an operation to release the force on the bone when the soft tissue balancing test indicates that soft tissue connected to the bone is in balance, when a threshold force is reached, when a threshold tension is reached, when a predetermined distance (e.g., a distance equal to a tibial implant thickness), or the like. Releasing the force on the bone may include returning the force to zero, such as by increments. For example, the soft tissue balancing test indicates that the soft tissue connected to the bone is in balance based on detecting the bone in a pre-determined orientation during the test. In another example, the soft tissue balancing test indicates that soft tissue connected to the bone is in balance when sufficient data is collected to determine a balance in the soft tissue, and wherein the balance is an indication of the difference in tension between a medial side and a lateral side of the joint. The balance may indicate an angle for a resection cut to be made in a joint replacement procedure. The technique <NUM> may include an operation to perform a release of a portion of soft tissue connected to the bone based on the soft tissue balance. The technique <NUM> may include an operation to output, for example for display on a user interface, an indication of soft tissue balance or an angle of rotation of the bone relative to a second bone.

The technique <NUM> includes an operation to calculate a target femoral implant rotation using a determined rotation of the femur during a soft tissue balancing test. The determined rotation used is when the gap balance is equal to a predetermined gap distance. The target femoral implant may be the inverse or opposite of the determined rotation. The technique <NUM> includes an operation to store the target femoral implant rotation, such as in memory or a database, for use by planning software.

<FIG> illustrates a flow chart showing a technique <NUM> for performing robot-aided surgery using a force sensor in accordance with some embodiments. The technique <NUM> includes an operation <NUM> to secure a bone spike in a distal end of a first bone in a joint of a patient. The technique <NUM> includes an operation <NUM> to measure resistance in soft tissues connected to the first bone using a force sensor of a soft tissue balancing device coupled to a distal end of the bone spike via a spike socket.

The technique <NUM> includes an operation <NUM> to manipulate the soft tissue balancing device during the soft tissue balancing test using a robotic arm. The operation <NUM> may include applying tension to the joint using the robotic arm through the soft tissue balancing device during the soft tissue balancing test. The technique <NUM> includes an operation <NUM> to output an indication of tension in the soft tissue during a soft tissue balancing test. In an example, the first bone is a femur, and the soft tissue includes ligaments connecting the femur to a tibia of the patient joint. The technique <NUM> may include using the robotic arm is to manipulate the soft tissue balancing device with the femur and the tibia in flexion or extension.

The technique <NUM> may include an operation to output, from the robotic arm, a resection angle for an at least partial joint replacement to a computing device to calculate soft tissue balance in the joint. The computing device may be used to calculate a pin placement location for a cut guide based on the resection angle. In an example, a pin placement trial or pins may be positioned or placed, for example using the robotic arm, at a location on the first bone according to the pin placement location. The technique <NUM> may include an operation to output, from a force sensor, force data indicative of soft tissue tension in the patient joint when the force is applied to the first bone by the soft tissue balancing component. In an example, soft tissue tension may be determined at the patient joint based on the force data.

The technique <NUM> may include an operation to move the robotic arm to a soft tissue balancing test position and orientation relative to the first bone. In an example, the robotic arm may be controlled to retain the position and orientation relative to the first bone when the bone moves. The operation may include applying a force to the first bone using the soft tissue balancing component. The operation may include tracking movement of the first bone using an optical tracking system including a first optical tracker affixed to the first bone of the patient and a second optical tracker affixed to the robotic arm. The operation may include determining the tension in the soft tissue during a soft tissue balancing test using the tracked movement of the first bone. The operation may include tracking a position and orientation of the soft tissue balancing component when moved, and determining soft tissue tension using the position and orientation of the end effector and information from the optical tracking system including a position of the second optical tracker affixed to the robotic arm and a position of the first optical tracker affixed to the first bone. In an example, the operation may include determining a tension in medial soft tissue and a tension in lateral soft tissue using a force vector of the soft tissue balancing component on the first bone provided by the force sensor and a relative bone orientation of the first bone to a second bone provided by the optical tracking system.

<FIG> illustrate example user interfaces 3300A-3300D for joint replacement surgical planning in accordance with some embodiments. User interface 3300A of <FIG> includes a cut checklist <NUM> to illustrate cuts that have been performed or that are not yet completed. User interface 3300A includes an interactive user guide <NUM> showing a soft tissue balancing test overview. The user guide <NUM> shows a target implant rotation with respect to a femur to give a balanced flexion gap. The user guide <NUM> shows four steps of the soft tissue balancing test, from an initial state, to pulling on the femur, to showing a gap imbalance, to finally showing a rotation to align the soft tissue.

User interface 3300B of <FIG> includes a second user guide <NUM> including instructions on how to insert a spike <NUM> to connect a soft tissue balancing component <NUM> to a femur <NUM>. The spike <NUM> holds the soft tissue balancing component <NUM> in place, but may allow the femur <NUM> to rotate. The soft tissue balancing test may be initiated, for example, by pressing a foot pedal, which is indicated in the second user guide <NUM>. In an example, the soft tissue balancing test may be performed with a patella or soft tissue in place by using a j-shaped or hook-shaped soft tissue balancing component <NUM>. When the soft tissue balancing test is initiated, a robotic arm may pull the soft tissue balancing component <NUM>, such as by using an end effector connecting the robotic arm to the soft tissue balancing component <NUM> to apply a force on the spike <NUM>, which may in turn cause a force on the femur <NUM>, for example to move the femur <NUM> away from a tibia.

User interface 3300C of <FIG> includes a third user guide <NUM> which shows an illustration of a patient joint including a current imbalance at a particular gap distance, while superimposing a proposed balance (e.g., based on completed releases, cuts, and implants added to the joint). The third user guide <NUM> includes information related to a current rotation or a target femoral implant rotation (e.g., the rotation information may change over time or during a procedure, such as from a current rotation to a target rotation, or may show both, or a difference). The distance pulled (e.g., over time or at a current time) is also illustrated in the third user guide <NUM>. The third user guide <NUM> may include user-selectable options to apply a target femoral implant rotation to a 3D plan or to not apply the target femoral implant rotation to the 3D plan. The 3D plan may include preoperative or intraoperative plans. Adding the target femoral implant rotation to the 3D plan may include adding it to the 3D plan as is, or with changes (e.g., surgeon adjustments).

The user guide <NUM> may include a force bar <NUM> or a distance bar <NUM>. The force bar <NUM> may be used to display a current pulling force (e.g., of a robotic arm on the femur). In an example, the robotic arm may be stopped automatically by a robotic controller when the force reaches a maximum force, which may be displayed on the force bar <NUM>. In an example, a surgeon may control the robotic arm by adjusting the force bar <NUM>. The distance bar <NUM> may move simultaneously with the force bar <NUM> in an example. The distance bar <NUM> shows a distance pulled, such as a distance from the femur to the tibia (whether the femur or the tibia is pulled). In an example, the distance bar <NUM> may be controlled by a surgeon to move the robotic arm similar. In an example, the distance bar <NUM> may include a maximum distance pulled, which when the femur and the tibia are separated by the maximum distance, the robotic arm may be stopped.

User interface 3300D of <FIG> includes a fourth user guide <NUM>, which shows rotation of a femur in a knee joint in various views. The femur may be viewed in flexion with respect to a tibia or in extension. When used intraoperatively, as the joint is placed in these different orientations, the user guide <NUM> may be automatically updated (e.g., using trackers).

One or more of user guides <NUM>, <NUM>, <NUM>, or <NUM> may include information on ligament balance. For example, a soft tissue balancing test may be performed, and force information, tension information, or other sensor data may be sent to the one or more of user guides <NUM>, <NUM>, <NUM>, or <NUM> to display soft tissue balance, such as a rotation angle to balance the ligaments. In another example, the one or more of user guides <NUM>, <NUM>, <NUM>, or <NUM> may display a measured resection technique, for example by providing feedback on actual measured angles or detected forces after or before resection, in addition to the rotation angle at which there is balance.

In an example, medial and lateral borders of a tibial tubercle may be identified and used to determine a medial third landmark location. The one or more of user guides <NUM>, <NUM>, <NUM>, or <NUM> may display the medial and lateral borders or the medial third landmark location. For example, a robotic arm may be used to identify a most medial boundary of a tibial tuberosity. The robotic arm may be used to identify a most lateral boundary of the tibia tuberosity. A system may use these identified boundaries to accurately display and locate a location known as a medial third location on the tibial tuberosity. Identifying this location may not be reproducibly performed with conventional instrumentation, such as with sub-millimeter metric precision. This location may be used to assist in a rotational placement of a tibial base plate for a knee arthroplasty as a reference point.

Claim 1:
A robot-aided knee arthroplasty system comprising:
an end effector (<NUM>) of a robotic arm (<NUM>) to couple to a femur of a knee joint with a soft tissue balancing component that permits the femur to freely rotate while coupled to the end effector (<NUM>);
a robotic controller (<NUM>) to:
cause the robotic arm (<NUM>) to apply a pulling force to the femur using the end effector (<NUM>) to increase a gap distance between a first point on the femur and first point on a tibia of the knee joint;
measure the gap distance between the first point on the femur and the first point on the tibia and a rotation of the femur as the robotic arm (<NUM>) applies the pulling force to the femur using the end effector (<NUM>);
determine whether the measured gap distance of the knee joint is equal to a predetermined gap distance; and
store, when the measured gap distance is equal to the predetermined gap distance at the measured gap distance, the rotation of the femur as a target femoral implant rotation; and
a surgical planning system to plan a position and orientation of a resection of the femur for implantation of a femoral implant at the target femoral implant rotation,
wherein the first point on the femur and the first point on the tibia are defined such that, when the distance between the points is equal to the predetermined gap distance, the measured gap distance results in soft tissue balancing.