Bone screws, instrumentation, and methods of using of same

A stylet control system for selectively advancing and retracting a stylet includes a stylet having a first end and a second end, the second end being threaded, a screwdriver defining a bore for receiving a portion of the stylet and having a screw-engaging end for engaging a screw, the stylet being rotationally fixed relative to the screwdriver. The system includes a control device having a passage for receiving the screwdriver and having an inner portion defining a lumen for receiving the portion of the stylet, the inner portion being threaded for engaging the threaded second end of the stylet, when the screwdriver is rotated in the first rotation direction and the control device is prevented from rotating, the screwdriver advances the screw in the first axial direction and the stylet retracts in a second axial direction, opposite the first axial direction.

BACKGROUND OF THE INVENTION

The present invention generally relates to fixation devices, and more particularly, to spinal fasteners for single step insertion.

A technique commonly referred to as spinal fixation is employed for fusing together and/or mechanically immobilizing vertebrae of the spine. Spinal fixation may also be used to alter the alignment of adjacent vertebrae relative to one another so as to change the overall alignment of the spine. Such techniques have been used effectively to treat many degenerative conditions and, in most cases, to relive pain suffered by the patient.

In some applications, a surgeon will install pedicle screws into the pedicles of adjacent vertebrae (along one or multiple levels of the spine) and thereafter connect the screws with a spinal rod in order to immobilize and stabilize the vertebral column Whether conducted in conjunction with interbody fusion or across single or multiple levels of the spine, the use of pedicle screws connected by fixation rods is an important treatment method employed by surgeons.

There remains room for improvement in the design and use of pedicle screws, particularly for surgical efficiency while maintaining safety and accuracy during screw insertion.

BRIEF SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, a method of spinal repair includes the steps of inserting a stylet through a lumen of a screw such that a distal tip of the stylet extends distally from a distal end of the screw, the stylet extending along an axis; advancing the screw and the stylet toward a bone until the distal tip of the stylet contacts the bone; and rotating the screw about the axis of the stylet in a first direction and simultaneously oscillating rotation of the stylet about the axis between the first direction and a second direction opposite to the first direction.

In other embodiments, the step of rotating may include advancing the screw into bone. The step of oscillating may include retracting the stylet away from the bone. When the screw is rotated in the first direction and the stylet is rotated in the second direction, the screw and the stylet may move in opposite directions along the axis. The method may include the step of removing the stylet from the bone. The screw may have a distal cutting edge. The method may include the step of inserting the stylet into the bone to a depth that is less than an intended insertion depth of the screw.

Another embodiment of the disclosure includes a system for spinal repair. The system includes a screwdriver that includes a drill adaptor that has an internal surface and is rotatable in a first direction and a second direction opposite the first direction. The screwdriver includes a gear system that has a driving gear, a driven gear, and one or more connector gears, the driving gear has a splined internal surface and an external surface configured to mate with the internal surface of the drill adaptor such that rotation of the drill adaptor causes rotation of the driving gear in the same direction. The driven gear has a splined internal surface, the driving gear and the driven gear are connected by the one or more connector gears such that rotation of the driving gear causes rotation of the driven gear in the opposite direction. The screwdriver includes a first ratchet pawl that has a splined outer surface configured to engage the splined inner surface of the driving gear and a second ratchet pawl that has a splined outer surface configured to engage the splined inner surface of the driven gear. The first and second ratchet pawls are splined in the same direction such that when one of the driving gear and the driven gear engages the respective first or second pawl, the other gear is disengaged from the respective first or second pawl. A shaft is connected to the first and second ratchet pawls. The system also includes a stylet that has a threaded portion and a housing surrounding the first and second ratchet pawls and rotationally locked relative to the shaft. The housing has a threaded inner surface to engage the threaded portion of the stylet.

In other embodiments, the first and second ratchet pawls may each connected to the shaft by a pin. The shaft may rotate in a single direction. Rotation of the drill adaptor may cause rotation of the stylet in the same direction as the drill adaptor. The threaded portion of the stylet may include threads having the same pitch as internal threads of the threaded portion of the housing. Rotation of the drill adaptor in the first direction about the axis may cause the stylet to remain axially fixed and rotation of the drill adaptor in the second direction about the axis may cause the stylet to retract axially. The system may include a fastener defining a lumen for receiving the stylet. Rotation of the drill adaptor in the first direction and the second direction about the axis may cause the bone screw to advance into the bone. The fastener may include a channel adapted to receive a spinal rod, a shaft extending from the head to a distal tip, the distal tip having at least one cutting edge.

Another embodiment of the present disclosure includes a fastener that includes a head which has a channel adapted to receive a spinal rod, and a shaft extending from the head to a distal tip. The shaft has a thread, and the distal tip has at least one cutting edge.

In other embodiments, the fastener may be cannulated. The threads may continuously transition into the at least one cutting edge. The threads may terminate at a location spaced apart from the at least one cutting edge.

Yet another embodiment of the present disclosure includes a stylet control system for selectively advancing and retracting a stylet that includes a stylet that has a first end and a second end. The second end is threaded. The system includes a screwdriver that defines a bore for receiving the stylet and has a screw-engaging end for engaging a screw, the stylet is rotationally fixed relative to the screwdriver. The system includes a control device that is attachable to the screwdriver and has an inner surface defining a lumen for receiving the stylet. A portion of the inner surface is threaded for engaging the threaded second end of the stylet. When the control device is rotated in a first rotation direction and the screwdriver is prevented from rotating, the stylet advances in a first axial direction, and when the screwdriver is rotated in the first rotation direction and the control device is prevented from rotating, the screwdriver advances the screw in the first axial direction and the stylet retracts in a second axial direction, opposite the first axial direction.

In other embodiments, the threaded portion of the stylet may be an integral and monolithic part of the stylet. The stylet may be keyed and the screwdriver includes a corresponding keyed feature such as a hex feature on an inner surface to rotatably lock the stylet to the screwdriver. The system may include a quick connect feature to couple the control device to the screwdriver. The control device and the screwdriver may each include a robotic end effector.

Yet another embodiment of the present disclosure includes a stylet control system for selectively advancing and retracting a stylet that includes a stylet that has a first end and a second end. The second end is threaded. The system includes a screwdriver that defines a bore for receiving a portion of the stylet and has a screw-engaging end for engaging a screw, the stylet is rotationally fixed relative to the screwdriver. The system includes a control device that is operatively connected to the screwdriver and has an inner portion defining a lumen for receiving the portion of the stylet. The inner portion is threaded for engaging the threaded second end of the stylet. When the screwdriver is rotated in the first rotation direction and the control device is prevented from rotating, the screwdriver advances the screw in the first axial direction and the stylet retracts in a second axial direction, opposite the first axial direction.

In other embodiments, the stylet may be keyed and the screwdriver includes a corresponding keyed feature such as a hex feature on an inner surface to rotatably lock the stylet to the screwdriver. The system may include a robotic end effector and a cap to couple the screwdriver to the robotic end effector. The control device may be operatively connected to a robotic end effector. The control device may include an ultrasonic transducer for imparting an ultrasonic force to the stylet. The ultrasonic transducer may be positioned within a housing of the control device. The ultrasonic transducer may be detachable from and external to a housing of the control device. The ultrasonic transducer may include piezoelectric material. The inner portion of the control device may include at least one threaded pawl for engagement with the threads of the stylet. The system may be part of a kit which includes a robotic end effector. The kit may include a bone screw attachable to the screwdriver. The bone screw may be self-drilling. The bone screw may be cannulated. The control system of the kit may include an ultrasonic transducer for imparting an ultrasonic force to the stylet.

Yet another embodiment of the present disclosure includes a stylet control system for selectively advancing and retracting a stylet including a stylet having a first end and a second end, a screwdriver defining a bore for receiving the stylet and having a screw-engaging end for engaging a screw, the stylet being rotationally fixed relative to the screwdriver, robotic end effector having a passage therethrough, a cap configured to be received within a portion of the passage of the robotic end effector and being operatively connected to the screwdriver, a retraction feeder receivable within a lumen of the cap and having a mating engagement member for engaging the engagement member of the stylet, when the screwdriver is rotated in a first rotation direction, the screwdriver advances the screw in the first axial direction and the stylet engages the engagement member of the retraction feeder to retract the stylet in a second axial direction, opposite the first axial direction.

In other embodiments, the engagement members of the stylet and retraction feeders may include mating threads, and the retraction feeder includes a threaded pawl for one-way engagement of the threaded stylet. The stylet may be keyed and the screwdriver may include a corresponding keyed feature such as a hex feature on an inner surface to rotatably lock the stylet to the screwdriver. The control system may further include an ultrasonic transducer for imparting an ultrasonic force to the stylet. The retraction feeder may be rotatably locked within the end effector.

Another embodiment of the present disclosure includes a stylet control system for selectively advancing and retracting a stylet including a stylet having a first end and a second end, the second end being threaded, a screwdriver defining a bore for receiving the stylet and having a screw-engaging end for engaging a screw, the stylet being rotationally fixed relative to the screwdriver, a robotic end effector having a passage therethrough, a cap configured to be received within a portion of the passage of the robotic end effector and being operatively connected to the screwdriver, and a retraction feeder receivable within a lumen of the cap and having a threaded pawl for one-way engagement with the threads of the second end of the stylet, when the screwdriver is rotated in a first rotation direction, the screwdriver advances the screw in the first axial direction and the threads of the stylet engages the threaded pawl of the retraction member to retract the stylet in a second axial direction, opposite the first axial direction.

DETAILED DESCRIPTION

The present invention generally relates to a fastener to be used in conjunction with spinal rods during spinal surgery. Those of skill in the art will recognize that the following description is merely illustrative of the principles of the invention, which may be applied in various ways to provide many different alternative embodiments.

The various embodiments of the bone screws or fasteners described below are designed to facilitate efficient and accurate screw insertion during surgery. In some embodiments, the fasteners are cannulated for receiving a stylet extending through the length of the channel. In such cases, the stylet includes a sharp tip to create a pilot hole. In other embodiments, certain fasteners are solid along the shaft rather than being cannulated. In such embodiments, the distal tip of the shaft of the fastener includes a sharp cutting tip for forming a pilot hole and drilling into the bone. The use of the fasteners and/or stylet for creating the pilot hole and cutting into the bone until the threads of the fasteners engage and pull the screw into the bone eliminates the steps of reaming, awling, tapping the hole, or otherwise preparing the hole, before the screw can be placed into the prepared hole. As a result, the fasteners in the present disclosure provide for more efficient implantation.

FIGS.1-2depict a first embodiment of a fastener100and a Kirschner wire or stylet150that is configured for spinal applications, and in particular, for the use of fastener100as a pedicle screw, as will be described in detail below. Fastener100includes a screw shaft103and a tulip104, which has a channel adapted to receive a spinal rod. A spinal rod can be installed into tulip104and held in place by a set screw (not shown), which can be threaded into internal threads of tulip104.

Fastener100is polyaxial in that shaft103is separate from and polyaxially movable with respect to tulip104. Tulip104and a proximal end107of shaft103can generally be referred to as a head of fastener100. Shaft103extends along a longitudinal axis from its proximal end107to a distal tip109. Proximal end107of shaft103forms an interference fit connection with a distal opening of tulip104to create the polyaxial connection. Tulip104can swivel to form different angles with respect to shaft103which allows for proper rod placement. In alternative embodiments, the fastener may be a monolithic structure with the tulip statically connected with the proximal end of shaft103.

Shaft103includes threads112extending between proximal end107and distal tip109. As seen inFIGS.1and2, fastener100, including shaft103and tulip104, is cannulated through its entire length for receiving stylet150as shown. Stylet150terminates at a sharp distal point156.

With reference toFIG.2, distal tip109of shaft103is an annular surface that includes at least one cutting edge115for cutting into the cortical bone and facilitating initial engagement with the bone during insertion of fastener100such that distal tip109may be referred to as a drill tip. Cutting edges115are shaped to propagate a hole in the bone during advancement of fastener100. The annular surface of distal tip109forms two flat surfaces between cutting edges115in the form of notches for cutting the bone.

Threads112extend along shaft103to a distal end112aadjacent the distal tip109and cutting edges115. With the placement of thread112in close proximity to the cutting edges115, the threading facilitates the pulling motion of fastener100into the bone immediately after cutting edges penetrate cortical bone.

The embodiment of fastener100shown inFIGS.1and2includes a double lead thread. With a double lead thread, there are, as shown, two cutting edges115. Other embodiments may include a single or a triple lead thread, or may include more threads around shaft103. For example,FIGS.3and4show a fastener100′ which is substantially similar to fastener100except that the threading includes a triple lead thread, and fastener100′ includes three cutting edges115′ at distal tip109′ for cutting into the cortical bone until threads112′ engage the bone and pull fastener100′ into placement. The cutting edges115′ are formed by the thread exiting the bottom of the screw tip. A triple lead thread advantageously provides a more balanced approach that prevents grabbing of the bone by only one of the cutting edges. The number of cutting edges115does not have to equal the number of threads112along shaft103, since the function of cutting edges115to penetrate the bone is not always aligned with the function of threads112to advance fastener100along its trajectory within the bone.

FIGS.5and6depict a fastener200according to another embodiment of the present disclosure. Fastener200differs from fastener100in that shaft203is not cannulated but rather includes a cutting drill point216at the distal end209of the shaft. Threads212transition into the cutting point216at distal end209, such that cutting point216forms the drill tip to cut into the bone to form the hole without the use of a stylet. The distal portion of the shaft203may include one or more flutes214. Fastener200is polyaxial, though it can also be constructed as a monoaxial embodiment.

The fasteners ofFIGS.3-6include a smooth transition region between the cutting features and the threads. The smooth transition region allows the cutting features to continuously cut into bone until the cutting blends into the threads, which create the axial force to push the threads forward into the bone. InFIG.4the geometry is similar to an end mill, and inFIG.5the geometry is similar to a brad point drill tip.

As a result of cutting drill point216, fastener200can be inserted into the bone in one step which eliminates a separate step of reaming or drilling the hole with a separate tool before inserting fastener200into the bone. This advantageously reduces the number of steps and tools required during surgery. Additionally, the sharp cutting point216facilitates accuracy of the placement of the bone screw during insertion because it can be pushed into the bone to penetrate slightly and dock fastener200to prevent skiving during insertion.

FIGS.7and8depict a fastener300similar to fasteners100and200. Like fastener100, fastener300is cannulated for receiving stylet350. Fastener300includes distal end309formed into a drill point316with two cutting edges315. Drill point316is sized and configured to cut into the bone to form the hole during insertion of fastener300into a pedicle. As with fastener100, stylet350can be pushed into the bone to prevent skiving of fastener300during insertion.

Another embodiment of the present disclosure is a fastener400, shown inFIGS.9-11. Fastener400includes channel415extending through the entirety of the shaft403for receiving stylet450.

Stylet450includes elongated shaft body452extending along a longitudinal axis and terminating at sharp distal tip456. Body452of stylet450extends through a proximal end of the shaft403and out of distal end409such that the sharp tip456of stylet450extends beyond the distal end409of the shaft403of fastener400.

Body452of stylet450includes a keyed stop458that is engageable with a corresponding stop member, ledge, or shoulder positioned on or near a proximal end of shaft403. In an engaged position, the stylet is rotationally and axially fixed with respect to shaft403of fastener400. Stylet450can be disengaged from the locked relationship between the stylet and the shaft403so that the stylet can be removed from the cannulated channel of the fastener. Alternatively, stylet450may be frangibly connected to the screw, such that the frangible connection can be fractured for removal of the stylet after the bone screw is inserted into bone.

Keyed stop458may be in the form of a flat section running along at least a length of body452of stylet450to ensure that the body remains in an axially-fixed and rotatably-fixed position relative to shaft403. The cross-section of stylet450is non-circular to include the flat section or to be hexagonally shaped so that it can be rotationally locked with the internal lumen of fastener400. Thus, once stylet450is in place, the tip456coupled with distal end409of fastener400is configured similarly to cutting point216of non-cannulated fastener200.

During use, stylet450is first positioned within channel415of shaft403such that the keyed stop is engaged and the stylet is axially and rotationally fixed relative to the shaft. With the stylet450secured to the shaft403, the sharp tip456of the stylet450extends further distally than the fastener to form the cutting point. With stylet450secured to shaft403, distal end409of fastener400has the same shape and geometry of fastener200. Fastener400and stylet450rotate simultaneously as the fastener and stylet are advanced into bone. After fastener400is implanted to the desired depth in the bone, the keyed stop is disengaged and stylet450can be removed from the fastener. The removal of stylet450may be advantageous in certain instances because the sharp point456of the stylet is removed from the anatomy which may result in less damage to the surround area over time.

FIGS.12and13depict a fastener500according to yet another embodiment of the present disclosure. Fastener500includes a cannulated threaded shaft503that terminates at distal tip509. Distal tip509includes saw tooth members540positioned around the circumference thereof. Each saw tooth member540is in the shape of a triangular member terminating in a point. In the illustrated embodiment, there are six saw tooth members540; however, in other embodiments there may be more or less of the saw tooth members positioned around the circumference of the distal tip. Additionally, the saw tooth members may be larger or smaller depending on the number of members around the circumference. Although shown as triangularly shaped, in other examples, the saw tooth members may be trapezoidal, rectangular, etc.

FIG.14depicts a fastener600according to another embodiment of the present disclosure. Fastener600includes cannulated shaft that includes thread having serrations634along a portion of the shaft. Serrations634include alternating peaks and valleys. Serrations634may be in the form of the various embodiments of serrations described in U.S. application Ser. No. 15/645,264 filed on Jul. 10, 2017 and titled Spinal Fastener with Serrated Thread. The inclusion of the serrations reduces insertion torque, which reduces the chance of bone fracture and breaching. The shaft terminates at distal tip609which includes sharp triangular-shaped saw tooth members640positioned around the circumference of the distal tip.

FIGS.60-61show a fastener1300according to another embodiment of the present disclosure. Fastener1300includes cannulated shaft1303that is threaded along its length to distal tip1309. Shaft1303tapers toward distal tip1309, and distal tip1309includes substantially V-shaped saw tooth members1340positioned around the circumference of the distal tip1309, as best shown inFIG.61.

FIGS.62-63show fastener1400according to another embodiment of the present disclosure. Fastener1400is similar in most respects to fastener1300except that shaft1403has a constant major diameter.

FIGS.64-65show fastener1500according to another embodiment of the present disclosure. Fastener1500includes cannulated shaft1503which tapers to distal tip1509. Fastener1500includes substantially C-shaped saw tooth members1540such that between adjacent tooth members is a curved edge rather than the pointed edge shown inFIG.61in connection with fastener1300.FIGS.66-67show fastener1600according an embodiment that is substantially identical to fastener1500except that fastener1600includes shaft1603with major constant diameter rather than a tapering profile, as in fastener1500.FIG.68shows fastener1700which is another variant of fasteners1500and1600, with fastener1700including shaft1703with a constant major diameter and tapering minor diameter.FIG.69shows the distal tip of fastener1800, which is another variant to fastener1500. Fastener1800includes saw tooth members1840angled relative to one another.

FIG.70shows fastener1900according to another embodiment of the present disclosure. Fastener1900includes cannulated threaded shaft1903which terminates at distal tip1909. Distal tip1909includes a only single cutting member1940for cutting into the bone. The single cutting member1940may have a rectangular, trapezoidal, triangular, or c-shape.

Referring toFIGS.15and16, a fastener700includes a non-cannulated threaded shaft703terminating at rounded distal tip709that includes burr members722that allow for high speed cutting of the cortical bone. The burr members722are positioned around the circumference of the distal tip and are separated from one another by cut-out portions.

In another embodiment, shown inFIG.17, a fastener800includes a self-drilling distal tip809with one or more flutes828positioned at a distal portion of shaft803. Threading812extends to the distal tip809which allows the shaft to engage and anchor into the bone immediately upon contact.

In an alternative embodiment, shown inFIG.18, a fastener900includes self-drilling distal tip909of the shaft which includes a helically threaded portion932. The pitch of threaded portion932is less than that of threads912of the shaft. As shown in the illustrated embodiment, the distal end of the shaft may include one or more flutes that do not cut across the entire helically threaded portion932.

In yet another embodiment,FIG.19shows a fastener1000having a distal tip that includes first threaded portion1014and second unthreaded portion1016which tapers inwardly to form a pointed tip1009to facilitate a self-drilling tip. The shaft also includes a cutting flute extending to pointed tip1009.

FIG.20shows a fastener1100which includes a threaded portion1112adjacent a distal portion of the shaft that has tap threads1132. Tap threads1132extend along less than half of the length of the shaft and may extend along about one-third of the length of the shaft. Tap threads1132are of a smaller pitch than the threads of threaded portion1112, and also include a helical flute extending along tap threads1132to facilitate threading of the hole through the cortical bone.

In another embodiment, shown inFIG.21, a fastener1200includes a shaft that terminates at awl tip1209. Awl tip1209is configured to create the pilot hole during implantation of fastener1200. Threads1212may overlap a portion of the awl tip or, as shown, threads1212may terminate at the proximal-most end of the awl tip.

It is contemplated that each of the non-cannulated fasteners can alternatively be cannulated for use with a stylet.

The method of using the solid, non-cannulated fasteners (i.e. fasteners200,700,800,900,1000,1100,1200) will now be described with specific reference to fastener200, although the method applies to each of the aforementioned non-cannulated fasteners. As shown inFIG.22, fastener200is positioned on the pedicle bone and distal tip209is docked onto the bone. The fastener200is pushed into the bone until the distal tip penetrates the bone to dock the fastener. This allows for an accurate point of entry during initial insertion of the fastener into the bone and prevents skiving of the screw. Torque is applied to the fastener, either by manual insertion, robotic or power insertion. The distal tip209cuts the bone until threads212catch bone and advance the screw into the bone, shown inFIG.23.

A similar method of implantation is used with fastener400as the stylet450and fastener become “integral” with one another while stylet450is in the engaged position and axially and rotationally locked with respect to fastener400. After implantation of fastener400, stylet450is removed from the bone.

The method of using the cannulated fasteners (i.e. fasteners100,300,500,600) will now be described with specific reference to fastener100, although the method applies to each of the aforementioned cannulated fasteners. As shown inFIG.24, stylet150is positioned within the channel of the shaft103of fastener100. Sharp tip156of stylet150is used to form the pilot hole. The stylet is then advanced into the bone, while shaft103remains placed on or above the bone surface. The stylet is advanced into bone about 5 to 30 millimeters, as shown inFIG.25. Torsion is applied to fastener100such that the screw rotates with respect to stylet150, which remains at its same depth within the bone during insertion of fastener100, and the cutting feature of the distal end of fastener100cuts into the cortical bone. For fastener100, the cutting feature includes cutting edges115. As fastener100cuts into bone, stylet150remains axially fixed and does not advance farther into the bone. The securement of stylet150in the bone at the desired depth of screw placement while fastener100is being advanced into the bone helps to prevent skiving. The advancement of fastener100relative to the secured stylet150helps to maintain the accurate trajectory of the fastener. Fastener100is advanced to the desired depth by continuing to rotate fastener100until its threads engage the bone and advance fastener100down stylet150, as shown inFIG.26. The depth to which fastener100is inserted is just smaller than the depth to which stylet150has been inserted. After final placement of the fastener, stylet150is pulled proximally and removed from the shaft of fastener100, as shown inFIG.27. Removal of the sharp tip of stylet150is advantageous in that it prevents damage that could otherwise be caused by the sharp feature to the surrounding area after the procedure.

The use of the stylet to maintain the proper trajectory during screw placement is advantageous particularly in instances where a fastener is screwed into a first surface of a first bone, is passed out of a second surface of the first bone, is made to traverse a gap between bone segments, and is screwed into a second bone segment. Typically, without the use of a stylet, as the screw exits the first bone and traverses the gap, the screw's path loses its accuracy before entering the second bone. In the present disclosure, the movement of the screw over the previously positioned and secured stylet maintains the placement of the screw along the proper position of the second bone despite having to traverse a gap. This technique is particularly useful in surgeries involving smaller pedicles, such as the pedicles of the thoracic spine. Placement of the stylet through the bone portions across the gap does not present the same difficulties, particularly given its sharp tip and the fact that it can be pushed or oscillated during insertion as opposed to being rotated. Often the skiving of a bone screw occurs based on the tip of the screw moving along the bone surface as it attempts to penetrate the surface while it is rotating. The fasteners of the present invention are aimed at eliminating this problem.

The step of advancing the stylet into the bone can be performed with the use of a robotic end effector2000and an advancement mechanism2100positioned at a proximal end of robotic end effector2000. In the illustrated embodiment, shown inFIGS.28and29, advancement mechanism2100includes threaded knob2105which engages the stylet as threaded knob2105is rotated in a first direction. As threaded knob2105is advanced distally, the stylet translates distally through a screwdriver2200and through the cannulated channel of the attached fastener. The stylet is connected to a sliding coupler2107that travels axially within the advancement mechanism. The coupler is attached to the stylet via a set screw to secure the stylet to the coupler. Once the stylet is advanced to the desired depth, threaded knob2105can be disengaged from the stylet and removed such that the stylet remains secured within the bone while the fastener is then rotated to advance the fastener into the bone. In alternative embodiments, advancement mechanism2100can include a spring, cam or gear in place of the threading to advance the stylet distally through screwdriver2000and the attached fastener.

FIGS.30-37show a placement device3100that may be used to place a stylet and fastener into the bone. Placement device3100may be used with robotic end effector2000or may be used during manual insertion. Placement device3100allows the stylet to oscillate back and forth between clockwise and counter clockwise directions while the fastener is advanced over the stylet in just one of those rotational directions and threaded into bone.

Placement device3100includes a drill adaptor3130through which the motor of end effector2000can be connected to device3100. Drill adaptor3130communicates with a double drive mechanism3120, as best shown inFIGS.31,32, and37. Double drive mechanism3120includes gear system3125formed of a driving gear3129and a driven gear3127. Driving gear3129has a splined outer surface at its proximal end that mates with a complimentary splined internal surface (not shown) of the drill adaptor3130so that rotation of drill adaptor3130is translated into rotation of driving gear3129. Driving gear3129is connected to driven gear3127through two connector gears3131,3132disposed at opposite sides of a collar3133. Through this connection, rotational movement of driving gear3129in one direction, e.g. clockwise, corresponds to rotational movement of driven gear3127in the opposite direction, e.g. counter clockwise.

A housing3134is disposed within the circumferences of driving gear3129, driven gear3127, and collar3133. Housing3134has two recesses3135,3137in which ratcheted pawls3136,3138, respectively, are disposed, as shown inFIG.37. InFIG.37, driven gear3127is shown in a misaligned state so that pawl3136is exposed, and driving gear3129is removed to expose pawl3138. As shown inFIG.36, an internal circumferential surface3139of driving gear3129is splined for communication with the ratcheted outer surface of pawl3138. An internal circumferential surface (not shown) of driven gear3127is similarly splined for communication with the ratcheted outer surface of pawl3136. Both of pawls3136,3138are ratcheted in the same direction about the axis of device3100. When one gear is in ratcheted connection with its pawl, the other gear slips past its pawl, and vice versa.

Pawl3136is connectable to a screw driver shaft3141through a pin3142. Similarly, pawl3138is connectable to screw driver shaft3141through a pin3143. Since pawls3136,3138are both ratcheted in the same direction while gears3127,3129disposed circumferentially above them are connected in opposite rotational directions, this dictates that rotational motion of housing3134will always only be driven by one of gears3127,3129through its respective pawl3136,3138. That is, when driving gear3129is rotated in a direction to engage with pawl3138, pawl3138engages screw driver shaft3141so that housing3134is rotationally locked with screw driver shaft3141. Also, when driven gear3127is rotated in a direction to engage with pawl3136, pawl3136engages screw driver shaft3141so that housing3134is rotationally locked with screw driver shaft3141. The opposite rotational directions of gears3127,3129therefore dictate that screw driver shaft3141will always be rotationally locked with housing3134and that housing3134will always be rotated in the same direction regardless of the direction in which drill adaptor3130is rotated.

Based on the structural makeup of device3100as described above, rotation of drill adaptor3130in either direction (i.e. clockwise or counter clockwise) will result in rotation of screw driver shaft3141in a single direction (i.e. only clockwise or only counter clockwise). As device3100is configured for insertion of a fastener, the direction screw driver shaft3141rotates is clockwise by right-hand rule. A distal end of screw driver shaft3141is noncircular to mate with the tulip of the fastener to facilitate insertion. A screw driver sleeve3144is disposed about screw driver shaft3141such that screw driver shaft3141can rotate therein. A distal end of screw driver sleeve3144has an annular depression in which interior flanges of each prong of the tulip can be seated to maintain the fastener at the end of device3100, particularly as it is advanced toward the surgical site.

The operation of gear system3125is made possible because an outer housing3145is held stationary (i.e. non rotatable) during operation of device3100. Outer housing3145is either held by the user or connected to the end effector2200during operation. Pins3146,3147are anchored to outer housing3145, through connector gears3131,3132, respectively, and into collar3133. This allows drill adaptor3130to be rotationally connected to driving gear3129and driven gear3127, and ultimately to housing3134to drive screw driver shaft3141, which in turn drives the fastener.

Another simultaneous function of driver3100is that it can rotate a stylet3180through a threaded proximal end3181of stylet3180. A threaded internal surface3182of housing3134is threadedly connected with threaded proximal end3181. Also, a pin3149is disposed through housing an aperture in threaded proximal end3181and protrudes through a slot in drill adaptor3130at either end, so that rotation of drill adaptor3130in one direction (i.e. clockwise or counter clockwise) always corresponds with rotation of stylet3180in the same direction (i.e. clockwise or counter clockwise, respectively) as drill adaptor3130. Thus, when drill adaptor3130is oscillated, stylet3180is also oscillated. When drill adaptor3130is rotated in one direction, stylet3180is rotated along with it.

The threaded connection of stylet3180with housing3134adds a further useful dimension to device3100since housing3134is axially stationary along device3100though it rotates in one direction due to double drive mechanism3125. Assuming device3100is configured so that clockwise rotation by right-hand rule advances the fastener distally, during clockwise rotation of drill adaptor3130, torque is transmitted by the slot in drill adaptor3130via pin3149to stylet3180, and stylet3180is simply driven in the same clockwise direction, though no translation of stylet3180occurs. The threads of threaded proximal end3181and housing3134are of the same pitch. When stylet3180and housing3134both rotate in the same direction, there is no relative movement between their threads. When the input motion is reversed to counter clockwise rotation of drill adaptor3130, stylet3180once again follows in the same counter clockwise direction of drill adaptor3130, but since it is threaded to housing3134that is rotating in the opposite clockwise direction, the relative motion between the mating threads causes an axial translation of stylet3180, having the effect of incremental retraction. The slot in drill housing3130through which pin3149is disposed accommodates translation of stylet3180. The position of the pin3149along the length of the slot can serve as an indicator for where the tip of stylet3180is relative to the tip of the fastener, and could include depth markings to give a more precise indication. Selecting a particular pitch and lead of threads dictates how much axial translation occurs for a given angular rotation of drill housing3130. Additionally selecting a particular pitch and lead of thread on the fastener dictates how much relative axial translation occurs between the bone and stylet3180.

Any of the previously described rotations or translations could be reversed to achieve alternative surgical goals, such as progressively advancing stylet3180or maintaining a constant stylet3180depth relative to the bone. A simple switch can also be provided to allow the user to mechanically select between “forward” (as described above) and “reverse” modes of device3100.

Spine surgeons currently use a natural oscillating motion to advance instruments into the spine to create a pilot hole in the pedicle to prepare for screw insertion. For example, a surgeon will twist an awl, gearshift, or jamshidi needle back and forth to carefully advance it to the desired depth. While device3100can be utilized either electronically (via power or a robot) or manually by hand, it captures this desired oscillating motion while simultaneously driving the fastener over the stylet in a single, efficient tool.

During use of device3100, stylet3180is first loaded by setting it to the proper depth relative to the length of the intended fastener. Since device3100is configured to either maintain the axial position of stylet3180or retract it, this is the furthest distally that the tip of stylet3180will be positioned relative to the handle of device3100during the procedure. A fastener3300is then loaded onto device3100by placing it over stylet3100and connecting it to screw driver shaft3141. Device3100is advanced until the distal tip of stylet3100is docked to the bone, as shown inFIG.38. At this point or during docking, the surgeon can begin to oscillate drill housing3130by hand or robotically by keeping outer housing3145stationary and not rotating it. This oscillating motion of stylet3180during docking prevents tugging on the local tissue and tendons so that the procedure can be carried out most efficiently and with the least disruption to the surrounding anatomy. While this practice is currently used by surgeons, the oscillation of stylet3180even when device3100is used robotically provides surgeons with comfort that the same technique is being applied during the procedure.

Continued oscillation of drill housing3130while device3100is being pushed distally embeds the tip of stylet3180into the bone until fastener3300meets the bone surface. At this point, further oscillation of drill housing3130engages the threads of fastener3300into the bone to advance fastener3300, all while fastener is guided by the path set by stylet3180. Upon each small counter clockwise rotation of drill housing3130, stylet3180retracts along the length of fastener3300so that stylet3180is retracted simultaneously. In this way, the surgeon can cannulate the pedicle via oscillating rotational motion of a sharp cutting tool such as a stylet or stylet3180, while simultaneously advancing a cannulated screw or fastener3300over stylet3180, all driven by a single oscillating input motion to device3100.

In other embodiments similar to device3100, the threaded connection and automatic retraction of stylet3180can be omitted and stylet3180can simply be pulled from the surgical site once fastener3300is implanted to the appropriate depth.

According to another embodiment of the present disclosure,FIGS.42-47show a stylet control system4000for selective and controlled axial movement (i.e. advancement and/or retraction) of a stylet for use during surgery in which a cannulated bone screw is inserted into bone around the stylet. Stylet control system4000includes control device4120for use in conjunction with a threaded stylet4150and a screwdriver4170during a spinal surgery in which a pedicle screw4010is implanted in bone. Control device4120may be controlled manually or with a robotic device, such as a robotic end effector.

Bone screw4010includes a head portion, a threaded shaft4011, and a tulip4020for coupling the screw to an orthopedic rod. Bone screw4010may be a standard size pedicle screw or it may be a screw adapted for use in minimally invasive surgery. Any of the above-described screws are suitable for use in stylet control system4000. Bone screw4010is cannulated such that stylet4150can extend through the cannulation and can extend beyond a distal tip of the screw. Bone screw4010has a threaded shaft4011and its head is received within tulip4020. Tulip4020is designed to receive a stabilizing rod therethrough. An inner surface of tulip4020includes threads capable of engaging with the screwdriver4170, described in further detail below. Further, bone screw4010includes a self-cutting feature at its distal end, such as sharp cutting edges.

Stylet4150extends between proximal end4152and distal end4158, which terminates at a sharp distal point to allow the stylet to cut through bone to form a cannulation for ease of insertion of bone screw4010, as described above. At proximal end4152, stylet4150includes monolithic threaded portion4159that facilitates axial translation of the stylet relative to screwdriver4170and control device4120. Stylet4150also includes an anti-rotation feature to prevent relative rotation between stylet4150and screwdriver4170. For example, in the illustrated embodiment, stylet4150includes keyed hex portion4153that has a hexagonal cross section extending along a portion of its length which corresponds to a hex feature on screwdriver4170, described below. As shown inFIG.43, hex portion extends from a distal end of threaded portion4159. Although described herein as a hex, the mechanically keyed feature may be square, oval, triangular, trapezoidal etc.

Control device4120includes proximal assembly4121that is rotatable relative to screwdriver4170. Proximal assembly4121includes inner core4125, coupling member4132, and outer handle4140. Inner core4125defines central lumen4126extending therethrough for receiving stylet4150. As shown inFIG.44, control device4120includes coupling member4132with base4134having a generally cylindrical shape and top portion4135having a planar surface and a sidewall with opposing cut-outs4135for receiving screws4138, which secure base4134to inner core4125. Base4134is sized to fit within central lumen4126of inner core4125. Coupling member4132includes a threaded opening4136extending through base4134and top portion4135for engaging threaded portion4159of stylet4150.

Inner core4125includes an attachment feature to attach coupling member4132to proximal end4130of inner core4125. In the illustrated embodiment, the attachment feature is in the form of two threaded bores4128extending into proximal end4130of inner core4125that are sized for receiving set screws4138. With coupling member4132axially and rotationally secured to inner core4125, threaded opening4136of the coupling member is coaxial with central lumen4126of the inner core so that stylet4150can extend through the assembly. In other examples, coupling member4132may be integral or monolithic with inner core4125.

Control device4120also includes outer handle4140housing coupling member4132and inner core4125. Outer handle4140defines central lumen4146extending longitudinally through its entirety. Central lumen4146is sized to accommodate inner core4125. Outer handle4140has a rounded outer surface to allow for a user to comfortably grip the handle. Outer handle4140is axially and rotatably fixed to inner core4125and coupling member4132such that when the outer handle4140is rotated in a first direction, e g manually or robotically, inner core4125and coupling member4132are also rotated in the first direction. In the illustrated embodiment shown inFIG.46, a proximal end of coupling member4132extends farther proximally than the proximal end of outer handle4140, such that threaded opening4136is positioned proximal to outer handle4140. Further, when stylet4150is positioned within inner core4125, a portion of stylet4150extends proximally to outer handle4140as shown inFIG.42.

Control device4120includes quick connect system4141that facilitates a simple and efficient connection to the proximal end of screwdriver4170, as shown in detail inFIGS.45-47. Quick connect system4141includes a collar4144that surrounds a distal shaft4127of inner core4125. An inner shaft4180of screwdriver4170is connected to collar4144via at least one a spring-loaded ball bearing4148received within a radial groove4178on inner shaft4180of screwdriver4170. When collar4144is located radially outside of radial groove4178with the ball bearing disposed within the groove4178, collar4144does not permit the ball bearing4148to leave groove4178, thereby connecting control device4120and screwdriver4170. The engagement of ball bearing4148and groove4178prevents axially movement of control device4120relative to screwdriver4170but allows rotation of the control device4120relative to the screwdriver4170. When collar4144is moved away, the ball bearing can move radially outward so that control device4120and screwdriver4170can be disconnected. Screwdriver4170also includes recess4176for attaching an alternative quick connect in the event the user wants to use a standard handle to manually drive the screw into bone.

The quick connect system4141may be released by applying an axial force in the proximal direction, which may be applied by a user to collar flange4149, to remove the radial load applied against the screwdriver4170to disengage the screwdriver from the control device4120.

Referring toFIGS.42and43, screwdriver4170extends between proximal end4172and distal end4184. Distal end4184is configured for securing to and engaging a screw, such as pedicle screw4010. Screwdriver4170may be used with mono-axial pedicle screws, poly-axial pedicle screws, reduction screws, or screws designed for minimally invasive surgeries (MIS screws).

At distal end4184, screwdriver4170engages screw4010. An outer sleeve may include external threaded portion configured to thread into corresponding threads on the inner surface of the tulip4020of screw4010. Inner shaft4180is positioned concentrically within the outer sleeve and includes a driving member for engagement within a corresponding opening of the head of bone screw4010. The driving member may be hexagonally shaped designed to torque bone screw4010to advance the screw into bone. Alternatively, inner shaft4180may include threads to engage the threads of tulip4020of screw4010.

Inner shaft4180is cannulated along its length and defines inner lumen4181to allow stylet4150to extend entirely through the shaft and through bone screw4010. Inner shaft4180includes an anti-rotation feature at its proximal end to prevent stylet4150from rotating relative to screwdriver4170. In this manner, stylet4150is rotationally coupled with screwdriver4170, and both are rotatable relative to proximal handle assembly4121. In the illustrated embodiment, the anti-rotation feature includes a hex-shaped inner surface4182surrounding inner lumen4181on at least the proximal end of the screwdriver4170. Hex portion4153on stylet4150is sized and shaped to fit within inner shaft4180without relative rotational movement between the hex members4153,4182, thus rotationally coupling the elements.

System4000is also designed for use in robot-assisted surgery and can be connected to a robotic device to facilitate the torqueing of bone screw4010into the bone and/or to facilitate the movement of stylet4150. In other examples, system4000can be manually operated in part, i.e. control device4120may be manually operated while the screwdriver is robotically operated, or both pieces can be either robotically or manually operated. For example, as shown inFIG.48, a robotic device4200including a robotic arm with a rotatable end effector coupled to the end of the robotic arm can interface with a robotic unit coupler positioned on proximal end4172of screwdriver4170. The robotic coupler includes at least one tab for transmitting torque to the screwdriver. End effector4210transmits torque to inner shaft4180to rotate the shaft4180in a clockwise direction to advance the screw in bone. When the control device4120is held stationary during this robotic rotation of screwdriver4170, stylet4150retracts proximally.

To assemble system4000, stylet4150is first advanced through control device4120and threaded portion4159of stylet4150is threaded into threaded opening4136of coupling member4132. Control device4120is then loaded onto screwdriver4170via quick connect system4141, while stylet4150is positioned through the assembled device such that it extends through the distal end of bone screw4010. When the stylet4150is loaded into the screwdriver4170, stylet4150is rotationally fixed relative to the screwdriver due to the mating hex features4182,4153of the screwdriver and the stylet.

In operation, with distal end4158of stylet4150positioned against bone, proximal handle assembly4121is rotated by rotating outer handle4140in a first direction, such as in the clockwise direction. When outer handle4140is rotated in the first direction, screwdriver4170is held stationary and is not rotated, which produces relative rotational movement between control device4120and screwdriver4170. The rotation of outer handle4140causes inner core4125to rotate so that threads of threaded opening4136of inner core engage threads of threaded portion4159of stylet4150. Screwdriver4170is held stationary, meaning that stylet4150is also not rotated. Thus, as threaded portions4136,4159engage each other, stylet4150advances axially through control device4120and screwdriver4170, i.e. stylet4150travels in the distal direction, based on the threaded engagement. As stylet4150moves distally it travels through bone and produces a path having the desired trajectory for the bone screw to follow, while the shaft of the bone screw4010remains placed on or above the bone. Once stylet4150is advanced to the desired depth in the bone, which may be about 5 to 30 millimeters, bone screw4010can be implanted over stylet4150to maintain the desired trajectory of the bone screw. Because bone screw4010advances over stylet4150, this helps to prevent skiving of the tip of bone screw4010relative to the intended entry point in the bone. In the example of robotic operation of the screwdriver4170, the end effector4210keeps the screwdriver stationary to insert stylet4150without impaction.

It is advantageous to advance bone screw4010into bone without further advancing stylet4150beyond the desired depth. In order to do so, proximal handle assembly4121is held stationary while screwdriver4170is rotated in a clockwise direction. When screwdriver4170is rotated clockwise, manually or robotically, inner shaft4180of the screwdriver4170rotates in this direction which drives bone screw4010into bone. As screwdriver4170is rotated, and thus stylet4150rotates while proximal handle assembly4121remains stationary, stylet4150travels axially in the retraction direction, i.e. proximally. It may be advantageous that the pitch of the threads of the stylet are the same as the pitch of the threads of the bone screw, which results in the stylet retracting at the same rate as the bone screw is advanced.

In another embodiment according to the present disclosure, control device4120is built into the robotic end effector4250. A back coupler is attached to end effector4250which functions as control device4120and facilitates the relative rotational movement of the screwdriver4170and the back coupler to control the movement of stylet4150in the proximal and distal directions, as desired. When screwdriver4170is driven in the counter-clockwise direction by the end effector4250, stylet4150rotates with screwdriver4170causing the stylet4150to rotate relative to the back coupler. This relative rotation causes stylet4150to advance axially in the distal direction to advance into bone. When the end effector4250rotates screwdriver4170clockwise, stylet4150translates axially in the proximal direction as screwdriver4170simultaneously drives the fastener into bone.

FIGS.49-54show stylet control system7000, which is built into end effector7200. Control system7000includes cap7027which forms a connection between the end effector and the instrument for use, e.g. screwdriver7170. Cap7027defines passage7029which extends from proximal end7031to distal end7033of cap7027and is sized and shaped to receive screwdriver7170into at least a distal portion of passage7029. Cap7027is configured to be attached to a proximal end of control system7000, as shown inFIG.50.

Screwdriver7170, with bone screw7010attached to a distal end thereof, is positioned within passage7029and attached to cap7027. As shown inFIGS.49and50, screwdriver7170extends distally from cap7027. Cap7027is then attached to end effector7200such that screwdriver7170is in operative engagement with the end effector. Cap7027may be designed as a universal cap which configured to attach to various instruments for use during preparation of the bone and implantation of an implant therein, e.g. screwdriver, drill, burr etc.

Control system7000further includes stylet7150which includes threaded portion7159at a proximal end thereof. At least a portion7153of the length of stylet7150is keyed and screwdriver7140includes an anti-rotation feature, such as a corresponding keyed feature to prevent relative rotation between stylet7150and screwdriver7140while allowing axial movement of the stylet within the screwdriver. In the illustrated embodiment, the keyed feature is shown as a hex, although the mechanically keyed feature may be square, oval, triangular, trapezoidal etc. Control system7000includes stylet feeder7140sized such that at least a portion of the stylet feeder7140is received within a proximal portion of passage7029of cap7027. A portion of stylet feeder7140is keyed to prevent relative rotation of the stylet feeder within cap7027. Stylet feeder7140includes hinged threaded pawl7145, the threads of which are configured to facilitate one-way engagement of threaded portion7159of stylet7150, e.g. engagement to cause proximal movement of the stylet during the rotation of the stylet, while disengaging for distal advancement of the stylet. In this regard, rotation of screwdriver during advancement of bone screw7010into bone causes rotation of stylet7150and thus engagement of threaded pawl7145with threaded portion7159of stylet7150. This engagement results in proximal movement, e.g. retraction, of stylet7150as the bone screw is advanced into bone. It may be advantageous that the pitch of the threads of the stylet are the same as the pitch of the threads of the bone screw, which results in the stylet retracting at the same rate as the bone screw is advanced. Of course, this is not required in all embodiments and there may be some benefit to having the stylet designed to retract at a different rate.

As shown inFIG.52, during use, stylet7150is inserted into stylet feeder7140such that the stylet extends through screwdriver7140and bone screw7010so that the distal tip of stylet7150extends just beyond the distal tip of bone screw7010. Stylet7150can then be impacted to dock the screw to the bone, such impaction can be done manually such as by hammering or ultrasonically, such ultrasonic advancement of the stylet is described below with reference toFIGS.55-58. Stylet7150may be impacted into the bone to a depth of between about 10 mm to 20 mm Once stylet7150is advanced to the desired depth, screwdriver7170is driven to advance bone screw7010into bone, which causes simultaneous retraction of stylet7150. After stylet7150is advanced to the desired depth in the bone, screwdriver7170is driven via end effector7200which rotates both the screwdriver and stylet7150, since the stylet is keyed to the screwdriver. As bone screw7010is driven into bone along the trajectory defined by previously implanted stylet7150, the threaded portion7159of stylet7150is engaged by pawls7145, which causes proximal movement, e.g. retraction, of stylet7150as the bone screw is advanced into bone.

According to another embodiment of the present disclosure,FIGS.55-58show a robotic stylet control device5000. Control device5000shares many similar to features as control device4000and control system7000, described above in connection withFIGS.42-47andFIGS.48-53, respectively, although control device5000is designed to facilitate ultrasonic movement and oscillation of a stylet as it is advanced into bone. Control device5000allows for movement of a stylet through a cannulated bone fastener, such as bone fasteners100-500and1300-1900or a cannulated drill, shown inFIG.58. Control device5000provides controlled axial movement (advancement and/or retraction) of a stylet during surgery including implantation of a cannulated bone fastener. The stylet is advanced into bone to create the initial pilot hole for subsequent insertion of the screw. Additionally, the control device5000ultrasonically oscillates during axial movement of the stylet. Such oscillation reduces the applied forces at the bone interface during the advancement of the stylet, which improves robotic accuracy as it minimizes the potential of deflection of the robotic arm. The reduction of force and increased accuracy may also result in a decreased likelihood of skiving.

Traditionally, in during manual preparation of a site for implantation of a bone screw, the process includes multiple steps including: awling, probing, tapping and then placement of the screw. Whereas, with the use of control device5000, the initial pilot hole is created with the stylet which is received within either a cannulated drill or a cannulated bone screw. Thus, control device5000is advantageously procedurally efficient as it eliminates the need for the traditional steps of pilot hole creation.

Turning toFIGS.55and56, control device5000includes housing5300, retraction assembly5140, and end effector5200. Control device5000further includes integrated ultrasonic transducers5275. Housing5300defines passage5310for receiving stylet5150. Housing5300includes a low gain transducer assembly5275for imparting ultrasonic vibrations to stylet5150. Control device5000further includes an energy source for generating the ultrasonic energy.

Transducer assembly5275comprises a plurality of piezoelectric elements positioned within housing5300. Ultrasonic vibration is induced in the end effector by electrically exciting transducers5275. In this example, transducers5275are comprised of piezoelectric elements which produce ultrasonic vibrations. Transducer assembly5275are low gain transducers and output frequencies in the range of about 10,000 Hz to about 30,000 Hz. Such ultrasonic vibrations are transmitted to the stylet5100positioned within passage5306of body5300.

FIGS.55and56show control device5000in conjunction with screwdriver5170and bone screw5010attached to the screwdriver. Stylet5150includes threaded portion5159at its proximal end to facilitate the axial movement of the stylet.

As shown inFIG.57, bone screw5010is positioned at or near the bone interface with the distal end of stylet5150substantially flush with distal end5012of bone screw5010. Upon actuation of the energy source and thus excitation of the piezoelectric elements of transducer assembly5275, ultrasonic vibrations are induced which oscillates stylet5150in a reciprocating longitudinal direction in strokes of about 20 to 100 micrometers (μm) which ultimately advances the stylet through distal end5012of bone screw5010and within the bone to create the pilot hole which is about 10 to 30 millimeters (mm) measured axially from the interface of the bone. Preferably, the stylet advances about 15 mm for creation of the pilot hole. Oscillation of stylet5150also occurs in a reciprocating torsional direction to twist and turn the stylet while it advances axially (shown by the arrows inFIG.57).

After stylet5150is advanced to the desired depth, e.g. about 15 mm, stylet5150is simultaneously retracted via retraction assembly5140as bone screw5010is driven into the bone by screwdriver5170. In this example, retraction assembly5140is positioned proximally of housing5300and defines passage5123for receiving stylet5150therethrough. Retraction assembly furthers includes an internally threaded portion for engaging threaded portion5159control device5000as described above in connection with control device4120, stylet5150is rotationally coupled to screwdriver5170such that when screwdriver5170and thus stylet5150rotates in a clockwise manner, the engagement of threaded portion5159of stylet5150and internally threaded portion of retraction assembly5140causes proximal axial advancement of stylet5150, e.g. retraction. Because the screwdriver is also rotating, this causes the bone screw5010to be driven into bone at the same time as stylet5150retracts. The pitch of the threads of threaded portion5159of stylet5150and the threads of bone screw5010may match to facilitate movement in opposite directions at the same rate.

FIG.58shows drill5270which may alternatively be utilized in conjunction with control device5000rather than the screwdriver/bone screw, described in connection withFIGS.55-57. Drill5270defines passage5275for receiving stylet5150therethrough. In this example, stylet5150is ultrasonically advanced through drill5270and into bone to create an initial pilot hole. The stylet is then retracted via retraction assembly5140, and drill5270is advanced into bone.

FIG.59shows control device6000which is another embodiment of a device for advancing and retracting a stylet and is similar in most respects to control device5000, the similar features of which will not be described again. Control device6000includes housing6300which operatively connects to a separate, non-integral ultrasound transducer device6270to impart the ultrasonic vibrations to advance the screwdriver or drill into bone.

Robotic systems may be used throughout the pre-operative and intra-operative stages of the surgery.

Preoperative planning for surgeries may include determining the bone quality in order to optimize bone preparation. Bone quality information, such as bone density or elastic modulus, can be ascertained from preoperative scans, e.g. CT scans. The bone quality data can be used to determine optimal properties for effective implant engagement. Examples of such methods are found in U.S. Pat. No. 10,166,109 to Ferko, filed on Sep. 18, 2014, entitled “Patient Specific Bone Preparation for Consistent Effective Fixation Feature Engagement,” U.S. Patent Application Publication No. 2015/0119987 to Davignon et al., filed on Oct. 28, 2014, entitled “Implant Design Using Heterogeneous Bone Properties and Probabilistic Tools to Determine Optimal Geometries for Fixation Features,” and U.S. Pat. No. 10,070,928 to Frank et al., filed on Jul. 1, 2015, entitled “Implant Placement Planning,” each of which is hereby incorporated by reference herein in its entirety. In addition to preoperative imaging, robotic surgery techniques may employ imaging, such as fluoroscopy, during surgery. In such cases, systems integrating the surgical system with the imaging technologies facilitate flexible and efficient intraoperative imaging. Exemplary systems are described in U.S. Pat. No. 10,028,788 to Kang, filed on Dec. 31, 2013, entitled “System for Image-Based Robotic Surgery,” hereby incorporated by reference herein in its entirety.

As in the instant case, robotic systems and methods may be used in the performance of spine surgeries to place implants in the patient's spine as in, for example, U.S. Patent Application Publication No. 2018/0325608 to Kang et al., filed on May 10, 2018, entitled “Robotic Spine Surgery System and Methods,” the disclosure of which is hereby incorporated by reference herein in its entirety. The robotic system generally includes a manipulator and a navigation system to track a surgical tool relative to a patient's spine. The surgical tool may be manually and/or autonomously controlled. Examples of robotic systems and methods that employ both a manual and a semi-autonomous are described in U.S. Pat. No. 9,566,122 to Bowling et al., filed on Jun. 4, 2015, and entitled “Robotic System and Method for Transitioning Between Operating Modes,” and U.S. Pat. No. 9,119,655 to Bowling et al., filed on Aug. 2, 2013, entitled “Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,” each of which is hereby incorporated by reference herein in its entirety.

A robotic controller may be configured to control the robotic arm to provide haptic feedback to the user via the robotic arm. This haptic feedback helps to constrain or inhibit the surgeon from manually moving the screwdrivers4170,8170of systems4000,8000beyond predefined virtual boundaries associated with the surgical procedure. Such a haptic feedback system and associated haptic objects that define the virtual boundaries are described in, for example, U.S. Pat. No. 9,002,426 to Quaid et al., filed on Jun. 23, 2008, entitled “Haptic Guidance System and Method,” and U.S. Pat. No. 8,010,180 to Quaid et al., filed on Dec. 21, 2012, entitled “Systems and Methods for Haptic Control of a Surgical Tool,” and U.S. Pat. No. 10,098,704 to Bowling et al., filed on May 18, 2016, entitled “System and Method for Manipulating an Anatomy,” each of which is hereby incorporated by reference herein in its entirety.

In some cases of autonomous positioning, a tool center point (TCP) of a surgical tool, such as screwdriver4170,8170, is brought to within a predefined distance of a starting point of a line haptic object that provides the desired trajectory. Once the tool center point is within the predefined distance of the starting point, actuation of an input causes the robotic arm to autonomously align and position the surgical tool on the desired trajectory. Once the surgical tool is in the desired position, the robotic system may effectively hold the rotational axis of the surgical tool on the desired trajectory by tracking movement of the patient and autonomously adjusting the robotic arm as needed to keep the rotational axis on the desired trajectory. Such teachings can be found in U.S. Patent Application Publication No. 2014/0180290 to Otto et al., filed on Dec. 21, 2012, entitled “Systems and Methods for Haptic Control of a Surgical Tool,” which is hereby incorporated by reference herein in its entirety.

During operation of a robotic surgical system, the operation of the surgical tool can be modified based on comparing actual and commanded states of the tool relative to the surgical site is described in U.S. Patent Application Publication No. 2018/0168750 to Staunton et al., filed on Dec. 13, 2017, entitled Techniques for Modifying Tool Operation in a Surgical Robotic System Based on Comparing Actual and Commanded States of the Tool Relative to a Surgical Site,” which is hereby incorporated by reference herein in its entirety. Further, robotic systems may be designed to respond to external forces applied to it during surgery, as described in U.S. Patent Application Publication No. 2017/0128136 to Post, filed on Nov. 3, 2016, entitled “Robotic System and Method for Backdriving the Same,” which is hereby incorporated by reference herein in its entirety.

Further, because of the non-homogeneity of bone, applying a constant feed rate, a uniform tool path, and a constant rotational speed may not be efficient for all portions of bone. Systems and methods for controlling tools for such non-homogenous bone can be advantageous as described in U.S. Pat. No. 10,117,713 to Moctezuma de la Barrera et al., filed on Jun. 28, 2016, entitled “Robotic Systems and Methods for Controlling a Tool Removing Material From a Workpiece,” which is hereby incorporated by reference herein in its entirety.