Cervical spine positioning system and apparatus

Abstract

A cervical spine positioning system includes an end effector configured to be secured to the head of a patient, as well as a plurality of cables attached to the end effector. A plurality of motorized pulleys are attached to the plurality of cables and configured to adjust the length of the cables to reposition the patient's cervical spine via movement of the end effector. A control device is in communication with the plurality of motorized pulleys.

Description

Attorney Docket No.: 104908-101 CERVICAL SPINE POSITIONING SYSTEM AND APPARATUS CROSS REFERENCE TO RELATED APPLICATION This application claims priority to United States Patent Application No.63 / 571,543, filed March 29, 2024, and entitled: CERVICAL SPINE POSITIONING SYSTEM AND APPARATUS, the entire contents of which is herein incorporated by reference. BACKGROUND

[0001] Deformity of the cervical spine may arise from tissue degeneration, trauma,destructive pathology like tumors and infections, or from failed spine surgery. Changes in alignment, loss of cervical lordosis, and neural compression may cause pain, myelopathy, radiculopathy, and sensorimotor deficits. Cervical spine deformity may also affect thoracolumbar alignment and pelvic tilt, as compensatory changes occur to maintain horizontal gaze. Operative procedures, such as cervical traction, are commonly performed to correct cervical spinal alignment. High distraction forces (up to 200 lbs.) may be necessary to reduce a spinal deformity into optimal alignment. Additionally, the position and orientation (i.e., the pose) of the head is important to achieve the optimal directionality of the force / moment application on the cervical spine. Failure to achieve these requirements may result in severe adverse outcomes, including repeated surgeries due to under-correction, ligamentous injuries, and in some instances neurological complications.

[0002] Because these applied distraction forces are large and precise, they are challenging toachieve by surgeons themselves in a confined workspace without any external assistance. Conventionally, pulley-rope systems with hanging weights are used to assist surgeons with applying the large distraction forces on the cervical spine. However, this latter method is difficult to use because manual increases in weight are necessary in order to increase the amount of traction. The amount of traction force depends on the available weights. Thus, the weight can only be added discreetly (e.g., 5 lb. increments), hence fine modulation of the traction force is not possible, leading to risks, such as over-traction. Additionally, the afore mentioned pulley- rope systems are cumbersome when transporting patients for radiologic or operative interventions and there is no built-in safety mechanism if the weights are disengaged or the skull 1 30986301.1Attorney Docket No.: 104908-101 tong slips. More importantly, because the force is applied at a single point on the head, this method has limited capability to position and orient the head, as well as change the direction of the forces.

[0003] There have been some improvements to traditional weight-pulley systems. Forexample, Kinnaird developed a portable system to provide cervical traction, which uses springs to replace the need for adding weights. The springs can be adjusted mechanically to change the amount of traction force. More recently, a motorized traction device was developed in which linear motors were used to tension the rope in lieu of weights. To safeguard the amount of force applied on the head and prevent over-traction, a load cell was used to monitor the tension within the rope. A closed-loop control was also implemented to apply the amount of traction force set by the surgeon through a simple console. Using this console, the surgeon can manually set the amount of traction force. In essence, each of these methods use different techniques to replace the need for weights.

[0004] Other recent techniques have been developed to apply forces on the cervical spinevia two (2) directional ropes originating from a single point on the head (e.g., bivector method), or leveraging the tilt of the hospital beds to apply traditional traction at a different angle. However, each of these latter techniques are currently implemented only via the weight-pulley systems, which have similar limitations as previously discussed. Additionally, in the bivector method, two separate weight-pulley systems are necessary, making this technique even more cumbersome to use and adding complexity and safety issues associated with intraoperative traction. Though advantageous, these methods still employ the same principle that was used in the traditional weight-pulley systems. That is, a static force is applied on the cervical spine via a single point, which fails to allow for positioning of the head or the flexibility to control force direction and / or apply moments on the head.

[0005] Accordingly, there is a pervasive need in the field to develop new tools to addressthe above-noted limitations for cervical spine deformity surgeries. Without any new developments, surgeons will continue to use outdated pulley-weight techniques with patients continuing to have suboptimal clinical outcomes. 2 30986301.1Attorney Docket No.: 104908-101 BRIEF DESCRIPTION

[0006] Therefore and in accordance with at least one aspect, there is provided a cervicalspine positioning system comprising an end effector configured to be secured to the head of a patient, a plurality of cables attached to the skull tong, a plurality of motorized pulleys attached to the plurality of cables and configured to adjust the length of the cables to reposition the patient’s cervical spine via movement of the end effector, and a control device in communication with the plurality of motorized-pulleys, the herein system being configured to provide application of force in a controlled and accurate manner using six (6) degrees of freedom.

[0007] In at least one embodiment, the plurality of cables comprises six (6) cables, and in atleast one other embodiment, the plurality of cables comprises seven (7) cables. The cables can be attached to a frame in which the plurality of motorized pulleys are attached to the frame such that the end effector is supported by the plurality of cables within the frame. In one or more embodiments, the frame comprises a plurality of casters attached to a base of the frame. In one or more embodiment, the frame can be folded for storage. The end effector can include skull tongs, a halo ring or other similar apparatus.

[0008] In some embodiments, the control device comprises a two (2) axis joystick, adisplay, and control circuitry that are configured to control the plurality of motorized pulleys, determine the force components applied to the end effector, and display the force components on the display, wherein the force components can comprise force magnitude and force vector angles.

[0009] According to at least one other aspect, there is provided a robotic system forsurgically manipulating the cervical spine to achieve satisfactory alignment, wherein the system comprises a patient side robot comprising a cable-driven mechanical electrical device attached to an end effector positioned on the head of a patient; and a surgeon-side robot comprising one or more control devices for controlling the cable-drive mechanical electrical device to apply six degree of freedom application of force and moment to head of a patient. In at least some embodiments, the surgeon-side robot can include a hand-held motorized device that maps the degrees of freedom of the patient-side robot and renders scaled force / moment in order to provide haptic feedback. The surgeon-side robot can be integrated with fluoroscopic systems in order to 3 30986301.1Attorney Docket No.: 104908-101 provide real-time visual information to the surgeon. The cable-driven mechanism of the patient- side robot includes a plurality of cables connected to a standard skull tong / clamp (e.g., Mayfield clamp) through an adapter. The cables are connected through motorized pulleys fixedly attached onto a frame. An electrical system includes actuators, sensors, microcontrollers, screens, switches, custom-made integrated circuits, and interfaces to provide power and communication of the patient-side and surgeon-side robots, as well as integration with the fluoroscopic systems. Software is also included as part of the herein described system, which includes control algorithms for each robot to apply force / moment on the head of patients and scaled force / moment to the surgeon’s hand. Teleoperative control strategies are also included in at least one embodiment to render the force / moment commands.

[0010] A realized advantage of the herein described system is that of increased accuracy inthe alignment of the cervical spine of a patient during surgery.

[0011] Another advantage of this positioning system is the reduced need for future revisionsurgeries, as the device would be able to improve the accuracy of the cervical alignment, thereby resulting in better surgical outcomes

[0012] These and other features and advantages will be readily apparent from the followingDetailed Description, which should be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1(a) is a schematic view of a cervical spine positioning system in accordancewith aspects of the present disclosure;

[0014] FIG. 1(b) depicts a control structure for the cervical spine positioning system of FIG.1(a) according to various aspects of the present disclosure;

[0015] FIG. 2 is a side perspective view of a portion of a cervical spine positioning systemmade in accordance with aspects of the present disclosure; 4 30986301.1Attorney Docket No.: 104908-101

[0016] FIG. 3 is a top perspective view of a portion of a cervical spine positioning system inaccordance with aspects of the present disclosure, including a phantom neck portion within the frame of the device, the phantom neck portion being shown as enlarged in an inset thereof;

[0017] FIG. 4(a) is a top perspective view of a control device for a cervical spinepositioning system made in accordance with aspects of the present disclosure, the control device further a display;

[0018] FIG. 4(b) is a visualization of a force vector applied by a cervical spine positioningsystem, such as that displayed by the control device of FIG.4(a);

[0019] FIG. 5 is a schematic diagram of a control block for a cervical spine positioningsystem in accordance with aspects of the present disclosure;

[0020] FIGS. 6(a) – 6(f) depict measured and actual positions of an end effector (headpiece) of a cervical spine positioning system displayed graphically, and in accordance with aspects of the present disclosure; and

[0021] FIGS. 7(a) -7(f) depict desired, robot-measured and actual force and moments(“wrench”) applied on an end effector (head piece) of a cervical spine positioning system and in accordance with aspects of the present disclosure. DETAILED DESCRIPTION

[0022] The following Detailed Description relates to embodiments that greatly improveupon the conventional single-force, weight-pulley approach through the development of a novel six (6) degrees-of-freedom positioning system that is configured to accurately manipulate the cervical spine through precise, surgeon-controlled forces and moments applied upon the head of the patient using two subsystems, namely a patient-side robot and a surgeon-side robot as well as electrical systems and software for enabling each of the subsystems. Throughout the course of this discussion, a number of terms are used to provide a suitable frame of reference with regard to the accompanying drawings. These terms, which may include “distal,” “proximal,” “first,” “second,” “third,” “above,” “below,,” “top” and “bottom” are not intended to limit the scope of the invention, unless where so specifically indicated. In addition the accompanying drawings are 5 30986301.1Attorney Docket No.: 104908-101 intended to illustrate salient features of each of the embodiments. The drawings should not be used for scalar purposes.

[0023] Among the embodiments discussed herein is a bench version of a robotic cervicalspine positioning system, including validation / experimentation results pertaining thereto.

[0024] A cervical spine positioning system 10 is illustrated in schematic form in FIG. 1(a).In brief, this positioning system 10 is designed for purposes of correcting spinal deformity and includes two (2) major subsystems, namely, a surgeon-side robot 20 and a patient-side robot 40, which are disposed in relation to a patient 50 lying on a standard bed or an operating table 60. The surgeon-side robot 20, which is operated by a surgeon 64 includes one or more control devices that can remotely control the operation of the patient-side robot 40. Additionally, a display 68 is configured for viewing real time images from fluoroscopic or other apparatus. The patient-side robot 40 includes a mechanism made up of a plurality of cables 42 and pulleys or pulley guides 44, each powered by motors 46 that are secured to a frame 48, wherein the patient- side robot 40 is configured to apply force and moment forces in six (6) degrees of freedom to an end effector 54 that is attached to the head of the patient 50 using the cable-driven mechanism, as described in greater detail below.

[0025] One embodiment of a cable-driven mechanism 100 is illustrated in FIG. 2. Thismechanism 100 is made up of a frame 104 that supports a plurality of components including a plurality of cables 108 that are commonly attached to an end-effector (also synonymously referred to herein as a “head-piece” 120) at one end of each cable 108. The head piece or end effector 120 is configured to be rigidly attached to the head of the subject through skull tongs (e.g., Mayfield tongs) a halo ring, or similarly structured apparatus using an adapter, allowing the cables 108 to transmit force and moment forces to the patient’s head. The end-effector 120, shown only schematically in FIG.1, is shaped and configured for attachment to the head of a subject / patient. The remaining end of each cable 108 is attached to a pulley wheel that is attached to a shaft of a motor, such as a servo motor, according to this embodiment, wherein each combined motorized pulley is herein labeled with the reference number 114. In this embodiment, a total of three (3) cables 108 extend from respective sides of the frame 104 within the X- Y plane, as shown, and are coupled to the end effector 120 at respective positions A1, A2 6 30986301.1Attorney Docket No.: 104908-101 and A3, as shown in FIG.1. In this embodiment, each of the positions A1, A2 and A3 are equally and circumferentially disposed 120 degrees apart on the end effector 120. However, other alignments of these latter points is acceptable.

[0026] In addition, a further number of the cables 108 further extend from a portion of theframe 104 commonly disposed an axial distance from the end effector 120 in the vertical or Z direction, as shown, in which the cables 108 also interconnect with the end effector 120 at the positions A1, A2 and A3, in a manner described in greater detail below. According to this embodiment, a total of seven (7) cables 108 were used to control a six (6) degree of freedom (DOF) wrench (i.e., a combination of force and moment) applied on the head of a patient via the end effector 120. When all of the cables 108 are placed in tension, the wrench can be applied on the end-effector 120 and therefore the head of the patient. Unlike rigid linkages, however, cables can only be pulled and cannot be pushed. As a result, at least one more (that is, the seventh cable) cable 108 is necessary for coupling to the end effector 120 via a motorized pulley 114 in order to fully control the degrees of freedom of the herein described system. According to this embodiment, the z-direction is coaxial with the spinal axis 124, also shown schematically, with the wrench as applied creating a resultant force vector 128.

[0027] In terms of overall description, an n-DoF wrench w applied on the end-effector 120is related to the m cable tensions τ by in which w is a 6x1 vector that represents the wrench (including a 3-dimensional force f and a 3- dimensional moment m) applied on the head of the patient, J is an n x m Jacobian matrix (n < m); (e.g., a 6x7 matrix), that depends on the geometry of the herein described robotic positioning system and which denotes the transmission of the system depending on the cable configuration.

[0028] Another embodiment of a similar cervical spine positioning system 200 is shown inFIG.3. As in the prior version, this positioning system 200 includes a fixed or stationary frame 204 that is sized and configured supports a plurality of motorized pulleys 214, as well as a plurality of cables 208. One end of each cable 208 is attached onto a pulley wheel of a corresponding motorized pulley 214, in which the pulley wheel is disposed onto a shaft of a 7 30986301.1Attorney Docket No.: 104908-101 motor, such as a servo motor. According to this example, the remaining end of each cable 208 is attached to a phantom neck 250 via an end effector 220, which is designed to replicate that of an actual subject. This phantom neck 250 consists of a series of 5 cm diameter foam rings, bonded via adhesives, in order to form a flexible vertical column that structurally mimic the mobile cervical spine. In this example, a 3D-printed and ring shaped end-effector 220 was attached on top of the foam rings of the phantom neck 250, to represent the head, as well as the attached skull tongs or similar apparatus on the head.

[0029] In some embodiments, the mounting positions of the motorized pulleys 214 can beadjustable on the frame 204, based on different design criteria. By way of a non-limiting example, four of the motorized pulleys 214 can be placed far from the head near the spinal axis to ensure efficient transmission of cable tension into a large distraction force (up to100 lb., or 400N, with an 11 mm pulley radius). The remaining three (3) motorized pulleys 214 can be positioned closer to the head for improved leverage when controlling the head’s position perpendicular to the spinal axis. The seven (7) cables 214 can terminate on the head attachment at three, non-collinear locations, resulting in a 2-3-2 configuration according to this embodiment based on the intersection points of the various cables 208 at the end effector. More specifically, two cables intersect at point A1, three cables intersect at point A2 and the remining two cables intersect at point A3, as shown in FIG.2. This latter configuration allows for analytical computation of the position and orientation of the head based on the angular displacements, as measured by the encoders of the various servo motors fixedly attached to the frame 204. The tensioning of the various cables is controlled by each of the motors. Various testing / validation results are provided for this specific embodiment in a later portion of this disclosure.

[0030] The forward kinematics problem is defined as solving the position and orientation ofthe end-effector 120 based on the cable lengths. The 2-3-2 cable attachment configuration shown in FIGS 1-3, allows the forward kinematics to be solved analytically. The bottom insertion point A2 is the terminus of three (3) cables 208 corresponding to three (3) servo motors whose positions in the inertial frame are known. The encoders of each of the corresponding servo motors of each of the motorized pulleys measure the joint angles, and these can be used to calculate the cable lengths given the radii of the pulley wheels. With the cable lengths known, three (3) spheres can be constructed centered at the exit point of each cable from the motor with 8 30986301.1Attorney Docket No.: 104908-101 radii corresponding to the lengths of each cable. The intersecting point of these spheres is the position of A2 in the inertial frame. With the position of A2 known, the positions of A1 and A3 can then be solved by using the same algorithm. The only difference is that one of the three spheres is centered at point A2with a radius between A2and A1or A2and A3, respectively. With the position of three points on the end-effector being known, the position and orientation of the end-effector can be solved based on the geometry of the end-effector. In some embodiments, the orientation of the end-effector is presented by Euler angles using the fixed x-y-z convention, corresponding rotations referred to as pitch-roll-yaw, respectively.

[0031] Given a desired 6-DoF wrench wd, where the first three elements represent the forcevector and the final three elements correspond to the moment, a Jacobian matrix J is used to solve for the cable tensions τ per Equation (1). Unit length cable vectors ci(which are shown in the embodiment of FIG.1) are constructed in the direction of each cable corresponding to the direction of the force applied by each cable on the end-effector. For purposes of calculating the moment applied by the cables on the end-effector, radius vectors bi (FIG.1) are constructed corresponding to the vector from the inertial origin to the cable force vector. The Jacobian matrix J is then constructed as follows:

[0032] Given wd and J, the controller then finds a cable tension solution τ such that, wheneach cable of the physical robot is tensioned accordingly, wdis applied to the end-effector. Because J is not a square matrix, J cannot be inverted to solve for the cable tensions.

[0033] In some embodiments and to solve for an optimal cable tension solution τ, thefollowing quadratic programming optimization problem was formulated:which will minimize the absolute difference between the desired and actual wrench (Jτ) applied by the herein described system. A gradient descent algorithm is then used to solve this optimization problem for an optimal τ in which each cable tension is between 15–250 N. τ is 9 30986301.1Attorney Docket No.: 104908-101 initialized at its minimum values such that the gradient descent algorithm will first arrive at a solution that minimizes τ by leveraging the convex structure of the landscape of this search problem. This removes the need for an additional tension-minimizing term in the objective function, improving runtime.

[0034] With reference to FIGS. 4(a) and 4(b), a user control and visualization interface isshown in accordance with at least one embodiment, which can be used, for example, in any of the positioning systems shown and described for the surgeon-side robot. The control device according to this embodiment is a two-axis joystick 180 having a display 184 as well as plurality of control buttons 188 defining a user interface, wherein the control device is configured for attachment to the herein described system to control the direction and magnitude of the three- dimensional force (force and moment) applied to the end effector. In this control scheme, the desired 3-dimensional moment vector is zero. After selecting a magnitude, the joystick angle is mapped to the direction of the force vector, where a vertical movement of the joystick results in a distraction force applied parallel to the spinal axis or z-axis. If the joystick is angled away from this default position, the force vector is angled proportionally relative to the z-axis, such that the components of the force vector along the x and / or y-axis are now nonzero. The control and visualization interface, as shown in FIGS.4(a) and 4(b) can describe the magnitude and direction of the force vector applied to the end-effector in two (2) different ways. On a large screen shown in FIG.4(b), a visualization of the force vector 192 can be provided, with the x and y- components of this force vector 192 being displayed on the x-y plane. In addition and on the large LCD screen provided next to the surgeon, the precise magnitude of the force vector 192 as well as the angles at which the force vector deviates from the z-axis along the x and y-axis can also be displayed.

[0035] The parallel cable-drive mechanism and the user control and visualization interfaceas described herein and be used as primary components of the patient-side robot and surgeon- side robot subsystems of an overall cervical spine positioning system, such as that previously schematically depicted in FIG.1(a). A patient 50 is disposed horizontally onto a bed 60 in relation to a surgeon 70 positioned in relation to the surgeon-side robot 20. The patient-side robot 40, as previously noted, is an electrically powered mechanical device that includes a head attachment element positioned on the skull of the patient that is joined with cables or other 10 30986301.1Attorney Docket No.: 104908-101 mechanisms for moving the head attachment element and thus the head of the patient. More specifically, the patient side robot 40, as previously described applies a six (6) degree of freedom force / moment on the head of the patient 50 while this force / moment is controlled remotely by the surgeon through the surgeon-side robot 20. In one or more embodiments, the frame 48 of the patient side robot 40 can include a set of casters 49 and can be anchored to the floor and / or fixed to a standard hospital bed or an operating table 60 during use to increase stability. In at least one embodiment, the frame 48 can also be folded for storage in order to minimize its footprint for purposes of storage. As previously described, a plurality of servo motors 46 are positioned on the frame with the cables 42 being attached to a skull tong / clamp (e.g., a Mayfield clamp), or a halo ring through an adaptor, onto the head of the patient 50.

[0036] With reference to FIGS. 1(a) and 1(b), the cable-driven patient side robot isconfigured to apply force / moment (6 DOF wrench) on the head and the control-visualization interface which can include a hand-held motorized device maps the degrees of freedom of the patient side robot and renders scaled force / moment in order to provide haptic feedback to the surgeon.

[0037] In this schematic system example, the surgeon-side robot 20 can be integrated withfluoroscopic systems 68, such as X-ray, to provide real-time visual information. Other aspects of this schematically shown system 10 include an electrical system with actuators, sensors, microcontrollers, screens, switches, custom-made integrated circuits (ICs) and interfaces to provide suitable power and communication for the overall system 10, as well as integration with additional systems, e.g., fluoroscopic machines and software including control algorithms for each robot 20, 40 to apply force / moment to the head of the patient 50 and scaled force / moment to the surgeon 64. The software and hardware can further include tele-operative control strategies to properly render the force / moment commands. The algorithms can also include safety measures to detect and address potential adverse events, such as, but not limited to pin slippage.

[0038] An example of a control structure to interface the surgeon with the robot control loopis shown in FIG.1(b). Based on the visual information through fluoroscopy and haptic feedback (^̂^^^), the surgeon 64 uses the surgeon-side robot 20 to manipulate the pose (^^^^) of the head and, consequently, the cervical spine. The patient-side robot 40 then executes a downscaled position 11 30986301.1Attorney Docket No.: 104908-101 (^^^^) and apply a six-DoF force / moment on the head (^^^^). This force / moment is measured by a force / torque sensor (not shown) that is embedded in the head-attachment and will be downscaled to render the haptic feedback (^̂^^^).

[0039] Another version of a control structure is shown in FIG. 5. In brief and according tothis approach, the surgeon will input a force on the surgeon-side robot, which will then scaled into a motion command for the end effector of the patient-side robot. Different from the prior example described above, the cable velocities (instead of tensions) according to this control block will be directly computed and achieved by the motors of the motorized pulleys. To avoid cable slacking, the cable tensions will be monitored (e.g., by an in-line tension sensor or using the motor current sensing), and if a low tension is detected, then compensation of cable velocity will be added so that all cables remain tout. The force-torque sensor on the end-effector will sense the force-moment applied to the head, which will be rendered back (with a down-scaling factor) to the surgeon-side robot as a haptic feedback.

[0040] The following legend relates to the preceding discussion of the control block of FIG.5, in which: ^^^^: force-moment measured by a 6-axes force-torque sensor mounted between the head and the robot attachment; ^^: wrench (force and moment) applied by the robot to the head, computed based on the robot configuration; ^^ℎ: estimated force-moment applied by the surgeon’s hand; ^^^^^^^^: desired robot attachment velocity, proportional to the hand force-moment via a gain ^^; ^̇^^^^^^^: computed desired cable velocities, related to the attachment velocity through robot Jacobian matrix ^^; ^̇^^^^^^^^: actual velocity output by the motors through its servo controller, measured through the motor encoder data; 12 30986301.1Attorney Docket No.: 104908-101 ^^^^^^^^: measured motor current through the motor-embedded current sensors; ^^^̇^: compensation of cable velocity due to slacking. The tension correction algorithm tensions the cable if the measured current is below a threshold; ^̇^: the real cable speeds applied to move the robot attachment; and ^^^^^^^^: estimated cable forces, related to the motor current through the rated motor constants ^^^^.

[0041] Preliminary bench testing was performed to validate the force / moment applicationand position / orientation measurement accuracy of the patient-side robot of FIG.3 using a control device and visualization interface as shown by the surgeon-side robot depicted in FIGS.4(a) and 4(b). More specifically, the following validation was made to validate the performance of the prototypical system, its ability to accurately produce desired forces, moments, and its ability to accurately measure the position and orientation of the end-effector through analysis of results was made as herein described, further demonstrating the safety and efficacy of the herein described positioning system.

[0042] To evaluate accuracy of position and orientation measurement through the forwardkinematics, the apparatus 200 of FIG.3 was placed within a 21-camera motion capture system. This motion capture system was used to measure the actual position and orientation of the end- effector 210 of the herein described system 200 in real-time. These data were then compared to the measured position and orientation data calculated by the system’s internal forward kinematics algorithm. Data were generated by rotating and translating the end-effector manually to assess as large of a workspace as possible (minimal tension of 15 N was maintained in each cable by the servo motors). Position and orientation data are presented in FIGS.6(a) – 6(f) versus time for pitch, roll, yaw (measured in degrees), as well as X, Y and Z (measured in mm). Position and orientation validation results of this data are herein presented in Table I. 13 30986301.1Attorney Docket No.: 104908-101

[0043] In addition to the preceding experiments and in order to evaluate the accuracy of thewrench computation, a 6-axis force / torque sensor was placed at the inertial frame origin of the device of FIG.3. The end-effector 220 was rigidly attached to the force / torque sensor (i.e., without the soft phantom neck 250) such that the actual wrench applied by the cables 208 on the end-effector 220 could be recorded. The measured wrench data were computed according to Equation (1), in which the Jacobian matrix J was computed according to Equation (2) using the forward kinematics algorithm, and τ is the optimal result of the tension planner optimization problem described in Equation (3). Wrench accuracy results are shown in FIGS.7(a)-7(f) for desired, robot-measured and actual wrench applied to the end effector of the herein described system in which X force, Y force and Z force (in Newtons (N)) were compiled, as well as X torque, Y torque and Z torque (in Newton meters (Nm)). Position and orientation validation results are summarized in Table II, where the listed error is herein defined as the difference between the desired and actual wrench. 14 30986301.1Attorney Docket No.: 104908-101

[0044] With the phantom neck model in place, experiments were also conducted varying themagnitude of the distraction force vector, as well as the direction of the force vector using the joystick.

[0045] Using the 2-axis joystick and user visualization interface of FIG. 4(a) as a surgeon-side robot, the herein described positioning system was able to apply sufficient force when used in a manner similar to traditional pulley-rope systems, in order to achieve optimal cervical spine alignment for surgeries requiring cervical spinal traction and head-neck manipulation. The novel features of the herein described device, including precise modulation of the force vector magnitude and direction, provide additional control and potentially improve surgical outcomes as a result of this control and accuracy by more easily manipulating the patient’s head and neck into the desired cervical spine alignment. A realized advantage of the herein described system is that of increased accuracy in the alignment of the cervical spine during surgery, thereby providing a strong positive indicator for the outcome of the surgery. A further advantage of this system would be in the reduced need for future revision surgeries, as the device would be able to improve the accuracy of the cervical alignment, resulting in better surgical outcomes.

[0046] Accordingly, in some embodiments, a user control scheme involved the operatorsetting a desired force vector (magnitude and direction) to be applied to the head using the control device settings. This technique is most similar to the already known technique that merely employs a rope, pulley, and weights; therefore, the surgeons would be most familiar with this control scheme. Alternatively, however, other control techniques could be employed. For example, a desired position and orientation of the patient’s head could be created by an operator using feedback control combined with the forward kinematics function, in which this control scheme could be implemented with the robot hardware. It will be understood that other suitable control techniques could be considered and implemented.

[0047] In at least one embodiment, the purpose of controlling the moment applied on theend-effector to be 0 Nm about all axes is to reduce unwanted twisting of the cervical spine as the cables are initially tightened to apply the forces desired by the operator. In one configuration, the unintended moment applied by the robot can be kept to <5 Nm. This may be improved by optimizing the positioning of the cables to prioritize moment reproduction ability. While the 15 30986301.1Attorney Docket No.: 104908-101 current paradigm is to apply linear forces to the head, through further experiments with this robot, surgeons may be applying the basic concepts described herein for purposes of applying moments to the patient’s cervical spine.

[0048] In some embodiments, motor encoder measurements were used to performposition / orientation measurement, while current sensors can be used to measure and compute the wrench applied on the end-effector. Use of precise sensors will improve the overall performance of the system. The system can be scaled in terms of overall performance by using more cables and / or employing servo motors with greater gear ratios or large pulley wheels to reduce the effect of motor friction on the system to optimize the application and overall improved wrench reproduction accuracy. However, this may inhibit the robot’s ability to generate large magnitude forces. To account for this, the number of motors could be increased; simultaneously, this may improve forward kinematics accuracy by averaging a greater number of data points to calculate the position and orientation of the end-effector.

[0049] Accordingly, the present disclosure presents numerous embodiment of a cervicalspine positioning system for cervical spine deformity surgery. Bench-top testing results clearly indicate that the herein described design is able to accurately produce a desired six (6)- degree of freedom wrench applied on the head, as well as measure the 6-DoF position and orientation of the head.

[0050] While the robotic system has been described in terms of particular variations andillustrative figures, those of ordinary skill in the art will recognize that the concepts described by this disclosure are not limited to the variations or figures described. That is, the head piece (end effector) and frame, among other structural components as herein described, can easily assume various shapes other than those illustrated and described herein.

[0051] In addition, where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. Therefore, to the extent there are variations, which are within the spirit of the disclosure or equivalent to the 16 30986301.1Attorney Docket No.: 104908-101 inventive concepts found in the appended claims, it is the intent that this patent will cover those variations as well.

[0052] To the extent that the claims recite the phrase “at least one of” in reference to aplurality of elements, this is intended to mean at least one or more of the listed elements, and is not limited to at least one of each element. For example, “at least one of an element A, element B, and element C,” is intended to indicate element A alone, or element B alone, or element C alone, or any combination thereof. “At least one of element A, element B, and element C” is not intended to be limited to at least one of an element A, at least one of an element B, and at least one of an element C.

[0053] This Detailed Description uses examples to disclose the invention, including the bestmode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

[0054] The terminology used herein is for the purpose of describing particular embodimentsonly and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes,” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes,” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device 17 30986301.1Attorney Docket No.: 104908-101 or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0055] The corresponding structures, materials, acts, and equivalents of all means or stepplus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description set forth herein has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of one or more aspects set forth herein and the practical application, and to enable others of ordinary skill in the art to understand one or more aspects as described herein for various embodiments with various modifications as are suited to the particular use contemplated and in accordance with the following appended claims. Additional embodiments include any one of the embodiments described above and described in any and all exhibits and other materials submitted herewith, where one or more of its components, functionalities or structures is interchanged with, replaced by or augmented by one or more of the components, functionalities or structures of a different embodiment described above and as set forth in the following appended claims. 18 30986301.1Attorney Docket No.: 104908-101 PARTS LIST FOR FIGS.1 – 7(f) 10 cervical spine positioning system 20 surgeon-side robot 40 patient-side robot 42 cables 44 pulley or pulley guides\ 46 motors 48 frame 49 casters 50 patient 54 end effector (head piece) 60 bed or operating table 64 surgeon 68 display / fluoroscopy 100 cable-driven mechanism 104 frame 108 plurality of cables 114 plurality of motorized pulleys 120 end effector (head piece) 124 spinal axis 19 30986301.1Attorney Docket No.: 104908-101 128 resultant force vector 180 joystick 184 display 188 plurality of control buttons 192 force vector 200 cable-driven mechanism 204 frame 208 plurality of cables 214 motorized pulleys 220 end effector (head piece) 250 phantom neck

[0059] Although the technology has been described and illustrated with respect toexemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions may be made therein and thereto, without parting from the spirit and scope of the present technology. 20 30986301.1

Claims

Attorney Docket No.: 104908-101 We claim:

1. A cervical spine positioning system comprising: an end effector configured to be secured to the head of a patient; a plurality of cables attached to the end effector; a plurality of motorized-pulleys attached to the plurality of cables and configured to adjust the length of the cables to reposition the patient’s cervical spine via movement of the end effector; and a control device in communication with the plurality of motorized-pulleys in which the system is configured to apply a six (6) degree of freedom force and moment to the end effector.

2. The system of claim 1, wherein the plurality of cables comprises six (6) cables.

3. The system of claim 1, wherein the plurality of cables comprises seven (7) cables.

4. The system of claim 1, further comprising a frame, wherein the plurality of motor-pulleys are attached to the frame such that the end effector is supported by the plurality of cables within the frame.

5. The system of claim 1, wherein the end effector comprises skull tongs or a halo ring. 6 The system of claim 4, wherein the frame comprises a plurality of casters attached to a base of the frame.

7. The system of claim 4, wherein the frame is foldable for purposes of storage.

8. The system of claim 1, wherein the control device comprises a 2-axis joystick, a display, and control circuitry configured to control the plurality of motorized pulleys, determine the force components applied to the end effector, and display the force components on the display.

9. The system of claim 8, wherein the force components comprise force magnitude and force vector angles. 21 30986301.1Attorney Docket No.: 104908-101 10. A robotic cervical spine positioning system comprising: a patient side robot comprising a cable-driven mechanical electrical device attached to an end effector positioned on the head of a patient; and a surgeon-side robot comprising a control device for controlling the cable- drive mechanical electrical device in the six degree of freedom application of force and moment to the end effector.

11. The robotic cervical spine positioning system of claim 10, in which the cable-drive mechanical electrical device comprises a frame, a plurality of motorized pulleys fixedly attached to the frame and a plurality of cables in which one end of each cable is attached to the motorized pulleys and a remaining opposite end of each pulley is secured to the end effector.

12. The robotic cervical spine positioning system of claim 10, in which the control device comprises a two-axis joystick configured for remotely controlling the operation of the cable- drive mechanical electrical device.

13. The robotic cervical spine positioning system of claim 10, in which the surgeon-side robot further comprises a display.

14. The robotic cervical spine positioning system of claim 11, wherein the plurality of cables comprises six (6) cables.

15. The robotic cervical spine positioning system of claim 11, wherein the plurality of cables comprises seven (7) cables. 22 30986301.1

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