Patent Description:
Surgical procedures are used to treat and cure a wide range of diseases, conditions, and injuries. Surgery often requires access to internal tissue through open or minimally invasive surgical procedures. The term "minimally invasive" refers to all types of minimally invasive surgical procedures, including endoscopic, laparoscopic, arthroscopic, natural orifice intraluminal, and natural orifice transluminal procedures. Minimally invasive surgery can have numerous advantages compared to traditional open surgical procedures, including reduced trauma, faster recovery, reduced risk of infection, and reduced scarring.

Whether minimally invasive or not, there are a number of surgical procedures in which it can be desirable to form a working channel in a patient to provide access to a surgical site within the patient. One such example is orthopedic or neurologic surgical procedures, including, e.g., spinal fusion procedures where it can be desirable to form a working channel through a patient's tissue to access their vertebrae and/or the intervertebral discs disposed between adjacent vertebrae.

A variety of methods for providing such a working channel are known, including various devices that are anchored to a surgical table upon which a patient is disposed, devices that penetrate tissue without being anchored to any other structure, or devices that anchor to a plurality of anchors implanted in a patient's bone. In such arrangements, the devices may be inadequately supported, may undesirably move relative to a patient if the patient moves relative to the operating table or some other external structure, or may impede a surgeon or other user in performing some aspect of a procedure.

By way of example, in spinal procedures involving operation on a patient's intervertebral disc disposed between adjacent vertebrae, access to the disc space can be difficult. The advent of modular pedicle screws can allow pedicle anchors to be implanted before performing intervertebral disc operations. As a result, retractor assemblies are used to hold open a surgical access site for insertion of the pedicle screws and subsequent operation. However, retractor assemblies often require complex articulation of various retractor arms and blade to effectuate an optimized access site. Retractor devices therefore often use polyaxial joints that can be selectively loosened and tightened during a surgical procedure; however, retractor device components, including the polyaxial joint need to be disassembled and sterilized prior to and after use.

Accordingly, there is a need for improved devices, systems, and methods that ensure the safe and secure option of the locking mechanisms between instrumentation components to ensure that they are not accidentally disassembled during a surgical procedure, while also allowing selectable articulation and movement between certain components. For example, there is a need for improved fastener assemblies to allow multicomponent devices to be securely assembled and safely adjusted during a surgical procedure without risk of accidental disassembly. <CIT> provides a surgical instrument according to the preamble of claim <NUM>.

Surgical instruments and systems, and background methods are disclosed herein that provide backout prevention for a screw used for polyaxial restraint and locking of components of surgical retractor assemblies. For example, the embodiments described herein provide a fastener and threaded housing assembly that can be used to adjust, for example, the position of a polyball in a socket of a polyaxial joint with two different drivers, where the first driver can be used to completely (e.g., back out) remove the fastener from the threaded housing, and the second driver can only be used to adjust the position of the fastener in the housing. The embodiments described herein can provide a number of advantages over prior approaches. This can include, for example, the ability to prevent accidental disassembly of the fastener from the housing during a surgical procedure when using a special driver trip for adjusting the fastener, the ability to insert and remove the fastener into the housing with a second driver before or after a surgical procedure in order to, for example, separately sterilize the fastener and housing.

A surgical instrument includes a body configured to receive a fastener, the body defining a cavity configured to receive a head of the fastener when the fastener is disposed in the body, the cavity having an inwardly extending flange defining a proximal opening of the cavity, a fastener having a threaded portion and a head portion, the head portion comprising an upper socket configured to interface with a driver for adjusting the position of the fastener within the body; a lower socket; and at least one channel radially extending from the lower socket and sized and shaped to allow translation of a locking body through the channel; and a locking body disposed in each of the at least one radially extending channels of the screw, wherein the surgical instrument has a first configuration when the head portion of the fastener is engaged by a first driver and a second configuration when the head portion of the screw of engaged by a second driver, wherein, in the first configuration, engagement of a drive portion of the first driver with the upper socket of the head portion allows the locking body to move radially inward in the channel such that the fastener can be inserted distally into the body and removed proximally from the body without interference between the locking body and the flange of the cavity, and wherein in the second configuration, when the fastener is disposed in the body such that the at least one radially extending channel is disposed distal to the flange of the cavity, engagement of a drive portion of a second driver with the upper socket includes engagement of a distal end portion of the second driver with the lower socket of the head portion that displaces the locking body radially outward such that the locking body interferes with the flange of the channel when the fastener is advanced proximally by the second driver such that the fastener cannot be removed from the body by the second driver.

In some instances, the locking body is a ball bearing. The cavity can define a length below the flange, the length of the cavity defining a maximum possible adjustment distance for the fastener in the body in the second configuration. The cavity can define a cylindrical inner wall, and where the flange is a radial flange. In some instances, the inner wall of the cavity defines a width that is larger than a diameter of the head portion of the fastener plus twice an extension distance of the locking body from the head portion in the second configuration.

The radially extending channel is configured to retain the locking body in the radially extending direction. The lower socket can define cylindrical inner wall. The upper socket can define shape configured to interface with a shape of the drive portion of the first and second drivers and enable torque to be delivered from the drive portion to the fastener for adjusting the position of the faster in the body. The body can include a threaded portion configured to receive the threaded portion of the fastener.

In some instances, in the first configuration, a maximum engagement position of the drive portion of the first driver with the upper socket of the head portion is defined by contact between a drive shaft of the first driver and the upper socket,.

In some instances, in the second configuration, a maximum engagement position of the distal end portion of the second driver is defined by contact between the distal end portion and a bottom of the lower socket.

In some instances, in at least one of the first or second configurations, a maximum engagement position of the drive portion is defined by contact between drive features of the drive portion and an end of corresponding drive features in the upper socket.

Another example of the present disclosure is a surgical instrument system having a retractor body configured to couple to an implantable anchor, a first tissue manipulating implement coupled to the retractor body and capable of polyaxial movement relative thereto, and a second tissue manipulating implement coupled to the retractor body and capable of polyaxial movement relative thereto, wherein each of the first and second tissue manipulating implements couples to the retractor body via a polyaxial joint, and each joint includes a screw to selectively lock the polyaxial joint against movement, and where each manipulating implement and screw includes a surgical instrument according to example of the present disclosure, wherein the manipulating implant includes the body of the surgical instrument and the screw includes the fastener.

In some instances, first and second tissue manipulating implements are opposed to one another such that they can move any of toward and away from one another.

The instrument can include a lock coupled to the body and configured to interface with the anchor extension to selectively lock a position of the body relative to the anchor extension.

In some instances, each of the first and second tissue manipulating implements couples to the body via a ball and socket joint. In some instances, each of the ball and socket joints includes an expanding member configured to selectively lock the ball and socket joint against movement.

Another example, useful as background to the present disclosure is backout prevention system having a body configured to receive a fastener, the body defining a cavity configured to receive a head of the fastener when the fastener is disposed in the body, the cavity defining an inwardly extending flange at a proximal location of the cavity, a fastener having a threaded portion and a head portion having an upper socket configured to interface with a driver for adjusting the position of the fastener within the body, a lower socket, and at least one channel radially extending from the lower socket and sized and shaped to allow translation of a locking body through the channel. The system also includes a locking body disposed in each of the at least one radially extending channels of the screw and a locking driver having a distal end region sized and shaped to engage both the upper socket and lower socket, the distal end region having a drive portion and a locking portion located distal to the drive portion, where the drive portion is configured to interface with the upper socket for delivering torque to the fastener for adjusting the position of the fastener in the body, and here the locking portion is configured to be disposed in the lower socket when the drive portion is interfaced with the upper socket and is sized and shaped to displace the locking body radially outward to a position that prevents the locking body in the fastener from being moved proximally past the flange. Where a standard driver having a distal end having a drive portion without a locking portion sized and shaped to move the locking body radially outward is able to deliver a torque to the upper socket to adjust the position of fastener in the body proximally and distally without interference between the locking body and the flange.

In some instances, the body is a first body and the system further including a second body configured to couple to an implantable anchor, where the first body defines at least a portion of a manipulating implement configured to be connected to the second body and capable of polyaxial movement relative thereto, where the tissue manipulating implement couples to the second body via a polyaxial joint, and where the position of the fastener in the first body selectively locks the polyaxial joint against movement.

Yet another example, useful as background to the present disclosure is method of assembling and adjusting the position of a fastener in a locking mechanism, the method including inserting the fastener into a body of the locking mechanism, coupling a first driver to the fastener and threading the fastener distally into engagement with the body using the first driver such that a locking body disposed in a radially extending channel of the fastener is disposed distal to an inwardly extending flange in a cavity of the body, with the fastener in threaded engagement with the body, coupling a second driver to the fastener, the second driver displacing the locking body radially outward such that the locking body interferes with the flange of the channel to prevent proximal movement of the fastener beyond a location where the locking body interfaces with the flange, adjusting the position of the fastener in the body using the second driver by threading the fastener between a maximum proximal location defined by the interference between the locking body and the flange and a maximum distal location. In some instances, the locking body is a ball bearing.

In some instances, the body includes a collet disposed in a socket, and wherein the inserting the fastener into the body includes coupling a distal end of the fastener to an expanding member disposed in the collet such that adjusting the position of the fastener in the body expands and contracts the collet in the socket and adjust a level of frictional engagement between the collet and the socket.

In some instances, the body is a first body that defines at least a portion of a manipulating implement and the socket is part of a second body that is configured to couple to an implantable anchor, and the method further includes coupling the collet to the socket after inserting the fastener to the first body with the first driver, the collet and socket defining a polyaxial joint, and wherein adjusting the position of the fastener in the body using the second driver includes selectively locking the polyaxial joint against movement.

Any of the features or variations described above can be applied to any particular aspect or embodiment of the present disclosure in a number of different combinations. The absence of explicit recitation of any particular combination is due solely to the avoidance of repetition in this summary.

This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:.

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure.

Additionally, to the extent that linear or circular dimensions are used in the description of the disclosed devices and methods, such dimensions are not intended to limit the types of shapes that can be used in conjunction with such devices and methods. Equivalents to such linear and circular dimensions can be determined for any geometric shape. Further, in the present disclosure, like-numbered components of the embodiments generally have similar features. Still further, sizes and shapes of the devices, and the components thereof, can depend at least on the anatomy of the subject in which the devices will be used, the size and shape of components with which the devices will be used, and the methods and procedures in which the devices will be used.

<FIG> illustrate an exemplary surgical instrument assembly <NUM> according to the teachings provided herein. The assembly <NUM> can be used in various surgical procedures, including spinal surgeries such as microsurgical bone resection, spinal decompression, spinal fusion, and the like. In general, the assembly <NUM> can include a support instrument <NUM> that couples to an implanted anchor <NUM>, such as a pedicle or other bone screw. The assembly <NUM> can further include a retractor <NUM> coupled to the support instrument <NUM>. Other components not illustrated here can be included or coupled to the assembly <NUM>. Such components can include, for example, any of a variety of cameras or visualization systems, and any of a variety of other surgical instruments.

An exemplary method of using the assembly <NUM> of <FIG> can include any one or more of the following steps, performed in any of a variety of sequences: a) making an incision in a skin of a patient; b) percutaneously inserting through the incision an implantable anchor, such as a pedicle or other bone screw; c) coupling the support instrument <NUM> to the implanted anchor (e.g., a pedicle anchor); d) coupling a tissue retractor to the instrument; e) providing medial-lateral retraction of tissue surrounding an incision; f) coupling an optical visualization instrument to the tissue retractor and/or instrument; g) resecting a portion of the superior articular process, and/or performing a microsurgical decompression procedure; h) extracting intervertebral disc material including removing cartilaginous material from the vertebral endplates; i) inserting an interbody device; and j) deploying a mechanism of stabilization to stabilize the intervertebral segment.

The above described retractor assembly <NUM>, in combination with the support instrument or anchor extension <NUM> and implanted anchor <NUM>, can be used to, for example, widen an incision formed in a patient's skin and tissue to enable better access to a surgical site. By way of further example, in some embodiments these components can form an assembly that is anchored to a single implanted screw or anchor and provides medial-lateral tissue retraction to increase access for a variety of surgical procedures. Medially and laterally retracting skin and underlying tissue surrounding an incision can provide a wider opening and working channel between the tissue manipulating implements to access the patient's spine or intervertebral space. In some embodiments, the working channel can extend to encompass an adjacent anchor implanted in an adjacent vertebra. Once the tissue of the incision walls is retracted to form the working channel, any of a variety of surgical procedures can be performed by introducing one or more instruments through the working channel defined by the tissue manipulating implements of the retractor assembly. For example, procedures on the intervertebral disc space, such as disc replacement, discectomy, endplate preparation, fusion cage insertion, bone graft delivery, and the like can be performed by passing instruments or implants through the working channel.

Returning to <FIG>, <FIG> illustrates one embodiment of a surgical instrument assembly <NUM> that includes a support instrument <NUM> coupled to an implantable anchor <NUM> and a tissue retractor <NUM>. Further details regarding embodiments of the assembly <NUM> can be found in <CIT>, entitled "PATIENT-MOUNTED SURGICAL SUPPORT," as well as<CIT>. Further details regarding embodiments of the implantable anchor <NUM> can be found in <CIT>, and entitled "BONE ANCHOR ASSEMBLIES AND RELATED INSTRUMENTATION. " Furthermore, details regarding certain embodiments of retractors that can be used in the surgical assembly <NUM> can be found below and in <CIT>. The entire contents of each of these references are useful as background and for the understanding of the disclosure.

Generally, the support instrument can include an elongate body <NUM> with a laterally-extending fork formed at a distal end thereof that can interface with a narrowed neck of the anchor <NUM>. The fork can include opposed projections that extend laterally from a distal portion of the elongate body and define a U-shaped or otherwise open-ended recess that can be sized to receive a portion of the implantable anchor <NUM>. For example, the projections can be configured to fit around a proximal portion of a bone anchor that can be part of a modular mono- or polyaxial pedicle screw. Such anchors can include a generally cylindrical distal shank portion with threads for tapping into bone, as well as a narrowed neck proximal of the shank portion and a wider proximal head. The proximal head can be generally spherical or semi-spherical in shape and can be configured to couple with a receiver head before or after implantation in a patient's bone. The elongate body can also include a lock configured to exert a drag force on the head of the anchor to control polyaxial movement of the instrument <NUM> relative to the anchor <NUM>. As shown in <FIG>, the lock can include a lock body <NUM> that is coupled to the elongate body <NUM> and translatable relative thereto along a longitudinal axis <NUM> of the elongate body. The lock body <NUM> can have a generally elongate shape to facilitate coupling with and translating or sliding along or relative to the elongate body <NUM>. The lock can be actuated by a lock screw <NUM> that can cause distal translation of the lock body <NUM> as the screw is threaded further into the elongate body <NUM>. The lock body <NUM> can further include a laterally-extending ring-shaped projection <NUM> at a distal end thereof that can be configured to contact the proximal head of the anchor <NUM> and exert a drag force thereon. The ring-shaped projection <NUM> can define a lumen to maintain access to a drive feature formed on a proximal end of the head of the anchor <NUM>. This lumen, in combination with the lateral extension of the projection <NUM> and the fork formed at the distal end of the elongate body <NUM> can orient the instrument <NUM> such that a longitudinal axis of the instrument is laterally offset or non-coaxial with a longitudinal axis of the anchor <NUM>. Such a configuration can allow a driver or other instrument to access the drive feature of the anchor <NUM> even when the instrument <NUM> is coupled thereto. This can enable flexibility to implant the anchor <NUM> any of before and after coupling the instrument <NUM> thereto.

Returning to <FIG>, a more detailed illustration of one embodiment of the tissue retractor <NUM> is provided. The retractor <NUM> can include a body <NUM> that can be configured to couple to the support instrument or anchor extension <NUM>. First and second tissue manipulating implements <NUM>, <NUM> can be coupled to the body <NUM> by, for example, rigid arms <NUM>, <NUM>, respectively. Each of the first and second tissue manipulating implements <NUM>, <NUM> can be capable of polyaxial movement relative to the body via a polyaxial joint <NUM>, <NUM>, such as a ball-and-socket joint. Such a joint can allow the tissue manipulating implements <NUM>, <NUM> to move relative to one another in a variety of manners. For example, the implements <NUM>, <NUM> can be pivoted toward or away from one another about an axis extending parallel to a longitudinal axis of a support instrument <NUM>, (e.g., an axis parallel to the axis <NUM> in <FIG>). The implements <NUM>, <NUM> can also be pivoted toward or away from one another about an axis transverse or oblique to, e.g., the axis <NUM>. For example, the implements <NUM>, <NUM> can be toed relative to one another, wherein distal ends of the implements are moved toward or away from one another by an amount greater than proximal ends of the implements. In some embodiments, toeing can include moving distal ends of the implements away from one another while proximal ends of the implements are either moved toward one another or do not move such that a distance between the proximal ends of the implements remains unchanged. Furthermore, each polyaxial joint <NUM>, <NUM> can include a lock <NUM>, <NUM> that can be used to selectively lock a position of the associated tissue manipulating implement <NUM>, <NUM> or impose a drag force to inhibit movement in the absence of at least a threshold level of force.

As noted above, the tissue retractor <NUM> can be configured to couple to a support instrument or anchor extension <NUM> and can be configured to slide along a length of such an instrument to adjust a height of the retractor relative to the implanted anchor <NUM>. As shown in <FIG>, the body <NUM> of the retractor can include a closed or partially-open lumen or recess <NUM> configured to receive a portion of the support instrument <NUM>, such as a generally cylindrical elongate body <NUM> (see <FIG>). The retractor <NUM> can further include a feature to selectively lock a position of the retractor relative to the support instrument <NUM>, such as a spring-biased protrusion or pawl <NUM> that can engage a ratchet rack or other series of recesses or other surface features formed on the elongate body <NUM> of the support instrument. Furthermore, in some embodiments the locking feature <NUM> can be configured to prevent not only movement along a length of the support instrument <NUM>, but also rotation thereabout. An actuator <NUM>, such as the illustrated sliding or translating member, can be included to allow a user to easily withdraw the protrusion <NUM> against the biasing force of a spring or other biasing element disposed within the body <NUM> of the retractor <NUM>.

In addition to adjusting a position of the retractor <NUM> along a length of the support instrument <NUM>, a length of each of the tissue manipulating implements <NUM>, <NUM> can also be adjusted. For example, in some embodiments the tissue manipulating implements <NUM>, <NUM> can each include an extension <NUM>, <NUM> that can be configured to translate relative to the tissue manipulating implements <NUM>, <NUM>. Proximally or distally translating either extension <NUM>, <NUM> relative to the associated implement <NUM>, <NUM> can change an overall length of the implement and, for example, can allow an implement to reach deeper into tissue even if the retractor <NUM> is mounted at a greater height above a patient's skin surface along a more proximal portion of the support instrument elongate body <NUM>.

<FIG> illustrates a partially exploded view showing how the retractor <NUM> can be coupled to the support instrument <NUM> by sliding the retractor down or distally over a proximal portion of the support instrument. For example, the recess or lumen <NUM> of the retractor <NUM> can be aligned with the generally cylindrical elongate body <NUM> of the support instrument and the retractor can be advanced down or distally along the axis <NUM>. While advancing the retractor relative to the support instrument, a user can manually retract the spring biased pawl or protrusion <NUM> using the sliding lever <NUM> to allow free movement of the retractor relative to the support instrument. When a desired position is reached, the user can release the lever <NUM> such that the protrusion <NUM> is advanced into engagement with a complementary recess or other feature formed on the elongate body <NUM> to maintain the relative positioning of the retractor and support instrument. In other embodiments, the complementary features formed on the elongate body <NUM> and the protrusion <NUM> can be formed as a biased ratchet wherein, e.g., distal advancement of the retractor can be achieved without actuating the lever <NUM>, but proximal withdrawal of the retractor <NUM> relative to the instrument <NUM> requires actuating the lever <NUM> to withdraw the biased protrusion <NUM>.

<FIG> illustrate the retractor <NUM> in various exploded and partially transparent views to better explain the interaction of various components thereof. For example, the polyaxial joints <NUM>, <NUM> can be seen in greater detail. Each polyaxial joint <NUM>, <NUM> can include a socket <NUM>, <NUM> formed in the body <NUM> of the retractor <NUM>. Each of the arms <NUM>, <NUM> coupled to the tissue manipulating implements <NUM>, <NUM> can have a generally ball-shaped proximal end <NUM>, <NUM> (e.g., a collet) that includes one or more relief slots formed therein such that various portions of the proximal end (e.g., petals <NUM>) can deform relative to other portions thereof. A lock <NUM>, <NUM> can be coupled to each arm <NUM>, <NUM> by cooperation between threads <NUM>, <NUM> formed on the lock and threads <NUM>, <NUM> formed on an inner surface of through-holes in the arms <NUM>, <NUM>. Further, an expanding member <NUM> can be disposed at a distal end of each lock <NUM>, <NUM> and arranged within the ball-shaped proximal end <NUM> such that adjustment of the lock <NUM> position by movement along the threads <NUM> can move the expanding member <NUM> distally within the ball-shaped proximal end <NUM> such that it urges the petals <NUM> outward or the expanding member <NUM> can be retracted proximally such that it sits more in a curved inside surface of the petals <NUM> and does not urge them outward. A lock assembly <NUM> can include a lock <NUM> and a portion of the arm <NUM> to which the lock <NUM> is operatively coupled.

When assembled, as shown in <FIG> and <FIG>, the expanding members <NUM>, <NUM> can be disposed within the generally ball-shaped proximal ends <NUM>, <NUM> in an un-locked (e.g., retracted) position that allows the expanding members <NUM>, <NUM> to be disposed within one of the sockets <NUM>, <NUM> of the body <NUM>. To lock the ball-shaped proximal ends <NUM>, <NUM> within and relative to one of the sockets <NUM>, <NUM>, the locks <NUM>, <NUM> can be rotated relative to the arms <NUM>, <NUM> to advance the expanding member <NUM> farther into the ball-shaped proximal end <NUM> due to the threaded coupling between the arms <NUM>, <NUM> and the locks <NUM>, <NUM>. Advancement of the locks <NUM>, <NUM> into the ball-shaped proximal end <NUM> can cause the expanding member <NUM>, <NUM> formed at a distal end of each lock to expand the petals <NUM> radially outward inside the sockets <NUM>, <NUM>. As the petals <NUM> of the ball-shaped proximal ends <NUM>, <NUM> expand radially, they are urged into contact with the sidewalls of the sockets <NUM>, <NUM>. This can cause an increase in frictional force between the sockets <NUM>, <NUM> and the ball-shaped proximal ends <NUM>, <NUM> of the arms <NUM>, <NUM>. Further, upon sufficient advancement of the locks <NUM>, <NUM>, the force of the expanding members <NUM>, <NUM> against the petals <NUM> can effectively lock the ball-shaped proximal ends <NUM>, <NUM> in a given position and thereby prevent any movement of the arms <NUM>, <NUM> or tissue manipulating implements <NUM>, <NUM> coupled thereto.

<FIG> illustrates an alternative embodiment of a surgical instrument assembly <NUM> that includes a support instrument <NUM> coupled to an implantable anchor <NUM> and a tissue retraction assembly <NUM>. Also shown is an embodiment of a driver <NUM> that can be used to actuate locks <NUM>, <NUM> that can selectively permit or prevent polyaxial movement of opposed tissue manipulating implements <NUM>, <NUM> relative to a body <NUM> of the retraction assembly <NUM>.

<FIG> illustrate the driver <NUM> in greater detail. In some embodiments, the driver <NUM> can include a housing <NUM> disposed about a driveshaft <NUM> that couples to a handle <NUM> at a proximal end thereof. A distal end <NUM> of the driveshaft <NUM> can be configured to interface with a proximal end of a lock <NUM>, <NUM> of the tissue retractor assembly <NUM> to impart an actuating torque thereto. The driver <NUM> can also include a stabilizing shaft <NUM> disposed coaxially about the driveshaft <NUM> and coupled to the housing <NUM> and an interface <NUM>. The interface <NUM> can include opposed slots or cut-outs <NUM>, <NUM> that can receive portions of one of the arms <NUM>, <NUM> when the interface is disposed over one of the locks <NUM>, <NUM> such that the distal end <NUM> of the driveshaft <NUM> engages the lock. A user can then counter brace against any tendency of the retractor assembly <NUM> to rotate or otherwise move in response to turning the handle <NUM> by holding the housing <NUM> steady. More particularly, the rigid, non-rotational coupling between the housing <NUM>, the stabilizing shaft <NUM>, and the interface <NUM>, in combination with the interface <NUM> being unable to rotate relative to the arms <NUM>, <NUM> due to the slots <NUM>, <NUM>, can provide effective stabilization when a user holds the base <NUM> while turning the handle <NUM>.

One issue encountered with instruments of the type described above is that a user might unintentionally back the screw <NUM> of the lock <NUM>, <NUM> out too far during a procedure. This can cause the screw <NUM> to become decoupled from the threads <NUM>, <NUM> of the tissue manipulating implement arms <NUM>, <NUM>. In order to prevent this, embodiments of the present disclosure provide a mechanism to stop the screw <NUM> of the lock, <NUM>, <NUM>, which is also referred to as a polyball tightening screw, from being unintentionally removed during a procedure. However, because the screw <NUM> also needs to be disassembled for cleaning and initial assembly, the screw <NUM> needs to be selectively removable past its backstop. Therefore, a back-out prevention mechanism allowing for selective removal of the screw <NUM> past a backstop is provided and described herein. This mechanism can be added to the lock assembly <NUM>, where backing out of the screw <NUM> is necessary to allow collapse and insertion of the petals <NUM> of the ball shaped proximal end <NUM> into the socket <NUM>, however backing out completely disconnects the screw <NUM> from the from the threads <NUM> and/or the expanding member <NUM>. This creates the need for a backstop to inform the user when the screw <NUM> is sufficiently backed out and/or prevent an unintended disconnection of the screw <NUM> from the expanding member <NUM> while still allowing adjustment of the screw <NUM> to enable adjustment of the lock assembly <NUM>.

One purpose of the back-out prevention mechanism is to allow backout prevention to occur without permanently capturing the screw or lock <NUM>, since permanent capture of the screw of the lock <NUM> is undesirable due to challenges posed when sterilizing components. For example, the assembly <NUM> may need to be completely disassembled after use and each component fully sterilized, which would require both decoupling the screw <NUM> from the threads <NUM> and the expanding member <NUM> from the screw <NUM>. If a more traditional captured screw was utilized to prevent unintentional backout, full disassembly would not be possible and thorough cleaning and sterilization can be difficult. Accordingly, the present disclosure provides a mechanism for selective backout prevention based on the driver utilized by a user, which can permit selective prevention of backout during a procedure but allow complete disassembly for cleaning and sterilization. As explained in more detail below, the lock assembly <NUM> can include a fastener (e.g., a screw <NUM>) and a body (e.g., a portion of the arm <NUM> receiving the screw <NUM>) that operate together to provide a back-out prevention mechanism that enables the screw <NUM> to be assembled or disassembled or adjusted with a first driver, and adjusted with a second driver, where the second driver cannot be used to disassemble or back-out the screw <NUM> from the arm <NUM>.

<FIG> is a perspective view of one embodiment of a distal end <NUM> driver tip <NUM> that can be utilized on, for example, the actuating instrument <NUM> of the assembly of <FIG>. The arrangement of <FIG> can also be referred to as a standard driver. As explained in more detail below, the standard driver <NUM> can be used to fully adjust the positioning of the lock <NUM> or other fastener in a lock assembly <NUM> (or the lock assembly <NUM> as shown in <FIG>), including an initial assembly or subsequently disassembly of the lock assembly <NUM>. <FIG> is a perspective view of an alternative distal end driver tip for use with the actuating instrument of the assembly of <FIG>. <FIG> shows a backout prevention driver <NUM> that includes a distal end <NUM> with two separate regions: a proximal driver tip <NUM> and a distal interference element <NUM> extending between the driver tip <NUM> and the termination of the distal end <NUM>. In operation, and as discussed in more detail below, use of the backout prevention driver <NUM> with the lock assembly <NUM>, <NUM> prevents the fastener or lock <NUM> from being disassembled or completely backed-out from the body <NUM>.

In <FIG>, the driver tips <NUM>, <NUM> are illustrated as having hexlobe drive features, which are one of many common driver features and are only shown as an example. Many different driver features can be used with the examples disclosed herein.

<FIG> are partially-transparent and cross-sectional views of a driver-specific backout prevention assembly <NUM> for use with the screw <NUM> and lock <NUM> of the polyaxial joints of the retractor of <FIG>. <FIG> is a partially-transparent view and <FIG> is a cross-sectional view, both showing the driver-specific backout prevention assembly <NUM> with a standard driver <NUM> disposed in a socket <NUM> of a screw <NUM> that is disposed in a body <NUM>. The body <NUM> can be, for example, the portion of the arm <NUM> receiving the screw <NUM>. The screw <NUM> can have a threaded portion that is threaded into a corresponding threaded portion of the body <NUM>. In some instances, however, the body <NUM> and the portion having the corresponding threading <NUM> can be separate parts and, in yet other examples, the screw <NUM> and the body <NUM> can be connected with a means other than threading, such as a pin and channel system or other means known in the art. Continuing, the body <NUM> defines a cavity <NUM> for receiving the head portion <NUM> or socket of the screw <NUM>. The cavity <NUM> includes an inwardly extending flange <NUM> or protrusion that serves as a back stop when a backout prevention driver is disposed in the head portion <NUM> (as illustrated in <FIG>).

Returning to <FIG>, the head portion of the screw <NUM> defines an upper socket <NUM> and a lower socket <NUM>, with the drive tip <NUM> only being able to engage the upper socket <NUM>. The head portion <NUM> also includes one or more channels <NUM> that extend radially from the lower socket <NUM>. Each channel <NUM> containing a locking body, such as the ball bearing <NUM> shown. In operation, the backout prevention assembly <NUM> allows the standard driver <NUM> to completely insert and remove the screw <NUM> from the body <NUM> because the ball bearings <NUM> disposed in the channels <NUM> do not interfere with the flange <NUM>, due to their ability to be deflected radially inward by the flange <NUM> at least partially into the lower socket <NUM>, as illustrated. Accordingly, <FIG> show the backout prevention assembly <NUM> in an "up" position with a standard driver <NUM>, where the male hexlobe feature of the driver tip <NUM> has bottomed out on the female lobes in the upper socket <NUM> and the ball bearings <NUM> are free to move inwards and allow removal of the screw <NUM> from the body <NUM>. <FIG> show the backout prevention assembly <NUM> in a "down" position with the standard driver <NUM>. Additionally, distal advancement of the screw <NUM> is limited by the interaction of the distal facing surface of the head portion <NUM> with a proximal facing surface of the cavity, as illustrated in <FIG>.

<FIG> are partially-transparent and cross-sectional views of the driver-specific backout prevention assembly <NUM> of <FIG> in use with the backout prevention driver <NUM> of <FIG>. <FIG> show the insertion of the distal end <NUM> of the backout prevention driver <NUM> into the head portion <NUM> of the screw, where the screw <NUM> is the "down" position and the interference element <NUM> is disposed in the upper socket <NUM>. In this position, the interference element <NUM> cannot engage the upper socket <NUM> to drive the screw <NUM>, as the interference element <NUM> lacks engagement features. Additionally, the ball bearings <NUM> are not restricted by the anything disposed in the lower socket <NUM> and are free to move.

Complete insertion of the distal interference element <NUM> into the lower socket <NUM> is shown in <FIG>, where the features of the driver <NUM> (e.g., male hexlobe) have bottomed out on the corresponding features (e.g., female lobes) of the upper socket <NUM>, and the interference element <NUM> is disposed in the lower socket <NUM>. Due to the presence of the interference element <NUM>, the ball bearings <NUM> are displaced radially outward until they extend from the head portion <NUM> and into the cavity <NUM> of the body <NUM>. The ball bearings <NUM> extend from the head portion beyond the outer diameter of the head portion and to a distance where they interfere with the flange <NUM> as the screw <NUM> is driven proximally, as shown in <FIG>.

In <FIG>, the backout prevention driver <NUM> has been used to back the screw <NUM> out of the body <NUM> until the ball bearings <NUM> reach an interference position (indicated by circle <NUM>) with the flange <NUM>. Because the presence of the interference element <NUM> in the lower socket <NUM> prevents the ball bearings <NUM> from moving radially inward past the inner diameter of the flange <NUM>, the backout prevention driver <NUM> cannot back the screw <NUM> out past the position shown. Accordingly, once the screw <NUM> is disposed in the body <NUM> with the channel <NUM> past the flange <NUM>, the backout prevention driver <NUM> can only be used to adjust the position of the screw <NUM> as allowed by the length <NUM> of the cavity <NUM> below the head portion <NUM> when the locking ball bearing <NUM> abuts the flange <NUM>.

<FIG> illustrate removal of the backout prevention driver <NUM> from the head portion <NUM>, whereby the ball bearings are free to move radially inward into the lower socket <NUM>, thereby allowing the screw <NUM> to be retracted proximally past the flange <NUM> using, e.g., the standard driver <NUM>.

<FIG> are top cross-sectional views through the lower socket <NUM> of the driver-specific backout prevention assembly of <FIG>, with <FIG> showing the ball bearings <NUM> in their displaced position (e.g., by the safety feature <NUM> disposed in the lower socket <NUM>) and <FIG> showing the ball bearings <NUM> in a 'free' position when there is sufficient room in the lower socket <NUM> for the ball bearings to be moved inwardly beyond being able to interfere with the flange <NUM> when the standard driver trip <NUM> is disposed in the socket. In some examples, and as illustrated in <FIG>, the channel <NUM> can include an inner abutment <NUM> to prevent the ball bearings from falling into the lower socket <NUM> and out of the channel <NUM>. In some examples, the channel <NUM> can include an outer abutment <NUM> to prevent the ball bearings from falling out of the head portion <NUM> when the head portion <NUM> is removed from the body <NUM>.

While the locking bodies have been shown as ball bearings <NUM>, other locking bodies are contemplated, such as pins, which can also include a spring for biasing the locking body inward to ensure that the locking body does not get stuck in an interference position and prevent removal of the screw <NUM>.

<FIG> is a photograph of one embodiment of the driver-specific backout prevention assembly <NUM> of <FIG>, showing the ball-shaped distal end <NUM> of a body <NUM> having a cavity <NUM> (not visible) and a screw <NUM> configured to be disposed in the body <NUM> to adjust the position of a tapered member (not shown) disposed at the end of the screw relative to a conic interior surface of the ball-shaped proximal end <NUM> for expanding the ball-shaped proximal end <NUM>. The head portion <NUM> of the screw <NUM> includes ball bearings <NUM> disposed in the channels <NUM>. <FIG> also shows an example backout prevention driver <NUM> having a driver <NUM> and a interference element <NUM> configured to engage with the socket of the head portion <NUM>, as described herein.

It should be noted that any ordering of method steps expressed or implied in the description above or in the accompanying drawings is not to be construed as limiting the disclosed methods to performing the steps in that order. Rather, the various steps of each of the methods disclosed herein can be performed in any of a variety of sequences. In addition, as the described methods are merely exemplary embodiments, various other methods that include additional steps or include fewer steps are also within the scope of the present disclosure.

The instruments disclosed herein can be constructed from any of a variety of known materials. Exemplary materials include those which are suitable for use in surgical applications, including metals such as stainless steel, titanium, nickel, cobalt-chromium, or alloys and combinations thereof, polymers such as PEEK, ceramics, carbon fiber, and so forth. The various components of the instruments disclosed herein can have varying degrees of rigidity or flexibility, as appropriate for their use. Device sizes can also vary greatly, depending on the intended use and surgical site anatomy. Furthermore, particular components can be formed from a different material than other components. One or more components or portions of the instrument can be formed from a radiopaque material to facilitate visualization under fluoroscopy and other imaging techniques, or from a radiolucent material so as not to interfere with visualization of other structures. Exemplary radiolucent materials include carbon fiber and high-strength polymers.

The devices and methods disclosed herein can be used in minimally-invasive surgery and/or open surgery. While the devices and methods disclosed herein are generally described in the context of spinal surgery on a human patient, it will be appreciated that the methods and devices disclosed herein can be used in any of a variety of surgical procedures with any human or animal subject, or in non-surgical procedures.

The devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, the device can be disassembled, and any number of the particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly.

The devices described herein can be processed before use in a surgical procedure. First, a new or used instrument can be obtained and, if necessary, cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument can be placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and its contents can then be placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation can kill bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container can keep the instrument sterile until it is opened in the medical facility. Other forms of sterilization known in the art are also possible. This can include beta or other forms of radiation, ethylene oxide, steam, or a liquid bath (e.g., cold soak). Certain forms of sterilization may be better suited to use with different portions of the device due to the materials utilized, the presence of electrical components, etc..

Claim 1:
A surgical instrument [<NUM>] comprising:
a body [<NUM>] configured to receive a fastener [<NUM>], the body [<NUM>] defining a cavity [<NUM>] configured to receive a head of the fastener [<NUM>] when the fastener [<NUM>] is disposed in the body [<NUM>], the cavity [<NUM>] having an inwardly extending flange [<NUM>] defining a proximal opening of the cavity [<NUM>];
a fastener [<NUM>] having a threaded portion and a head portion [<NUM>], the head portion [<NUM>] comprising:
an upper socket [<NUM>] configured to interface with a driver for adjusting the position of the fastener [<NUM>] within the body [<NUM>];
characterized in that, the instrument further comprises:
a lower socket [<NUM>]; and
at least one channel [<NUM>] radially extending from the lower socket [<NUM>] and sized and shaped to allow translation of a locking body through the channel [<NUM>]; and
a locking body disposed in each of the at least one radially extending channels [<NUM>] of the fastener [<NUM>],
wherein the surgical instrument has a first configuration when the head portion [<NUM>] of the fastener [<NUM>] is engaged by a first driver [<NUM>] and a second configuration when the head portion [<NUM>] of the fastener [<NUM>] is engaged by a second driver [<NUM>],
wherein, in the first configuration, engagement of a drive portion of the first driver with the upper socket [<NUM>] of the head portion [<NUM>] allows the locking body to move radially inward in the channel [<NUM>] such that the fastener [<NUM>] can be inserted distally into the body [<NUM>] and removed proximally from the body [<NUM>] without interference between the locking body and the flange [<NUM>] of the cavity [<NUM>], and
wherein, in the second configuration, when the fastener is disposed in the body [<NUM>] such that the at least one radially extending channel [<NUM>] is disposed distal to the flange [<NUM>] of the cavity [<NUM>], engagement of a drive portion of a second driver with the upper socket [<NUM>] includes engagement of a distal end portion of the second driver with the lower socket [<NUM>] of the head portion [<NUM>] that displaces the locking body radially outward such that the locking body interferes with the flange [<NUM>]of the channel when the fastener [<NUM>] is advanced proximally by the second driver such that the fastener [<NUM>] cannot be removed from the body [<NUM>] by the second driver.