Device for driver-specific backout prevention

Abstract

A driver-specific backout prevention mechanism is disclosed that includes a screw and a body. A first driver can be used to couple and separate the screw from the body, while a second driver can be used only to adjust the position of the screw within the receiving body. The body includes a cavity for receiving the head of the screw, the cavity having an inward flange. The screw includes an upper socket and a lower socket, a channel extending from the lower socket through the head, and a locking body disposed within the channel. Engagement with the first driver allows the locking body to move so that a fastener can be inserted and removed from the body. Engagement with the second driver displaces the locking body so that it interfaces with the flange, thereby preventing the screw fastener from being removed from the body by the second driver.

Description

[Technical field]

[0001] The present disclosure relates generally to surgical instruments, systems, and methods, and more particularly to instruments, systems, and methods that include driver specific backout prevention features that allow different drivers to selectively operate components. Such instruments, systems, and methods may be used in a variety of procedures, for example, orthopedic or neurological surgeries, such as spinal fusion surgery. [Background technology]

[0002] Surgery is used to treat and cure a wide range of diseases, illnesses, and injuries. Surgeons often need to access internal tissues through open or minimally invasive surgery. The term "minimally invasive" refers to all types of minimally invasive surgery, such as endoscopic surgery, laparoscopic surgery, arthroscopic surgery, natural orifice intraluminal surgery, and natural orifice transluminal surgery. Minimally invasive surgery can have many advantages over traditional open surgical procedures, such as less trauma, faster recovery, less risk of infection, and smaller scars.

[0003] In many surgical procedures, whether minimally invasive or not, it may be desirable to form a working channel within the patient to provide access to a surgical site within the patient. One such example is orthopedic or neurological surgery, including, for example, spinal fusion, where it may be desirable to form a working channel through the patient's tissue to access the patient's vertebrae and / or intervertebral discs disposed between adjacent vertebrae.

[0004] Various methods are known for providing such a working channel, including devices that are tethered to the operating table on which the patient is positioned, devices that penetrate tissue without being tethered to any other structure, or devices that are tethered to multiple anchors implanted in the patient's bones. In such device configurations, the device may be improperly supported, may move undesirably relative to the patient as the patient moves relative to the operating table or other external structure, or may interfere with the surgeon or other user in performing some aspects of the procedure.

[0005] As an example, in spinal procedures involving operations on a patient's intervertebral disc located between adjacent vertebrae, access to the intervertebral disc space can be difficult. With the advent of modular pedicle screws, it may be possible to implant a pedicle anchor prior to performing disc surgery. As a result, a retractor assembly is used to hold open a surgical access site for insertion and subsequent operation of the pedicle screw. However, the retractor assembly often requires complex articulation of various retractor arms and blades to achieve an optimized access site. Thus, retractor devices often use multi-axial joints that can be selectively loosened and tightened during a surgical procedure; however, the retractor device components, including the multi-axial joints, need to be disassembled and sterilized before and after use. Summary of the Invention [Problem to be solved by the invention]

[0006] Thus, there is a need for improved devices, systems, and methods that ensure safe and secure options for locking mechanisms between instrument 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 multi-component devices to be reliably assembled and safely adjusted during a surgical procedure without the risk of accidental disassembly. [Means for solving the problem]

[0007] Disclosed herein are surgical instruments, systems, and methods that provide backout prevention for screws used for polyaxial restraint and locking of components of a surgical retractor assembly. For example, the embodiments described herein provide a fastener and threaded housing assembly that can be used to adjust the position of a poly ball in a socket of a polyaxial joint, for example, with two different drivers, where a first driver can be used to completely remove (e.g., back out) the fastener from the threaded housing, and a second driver can be used only to adjust the position of the fastener in the housing. The embodiments described herein can provide many advantages over conventional approaches. These can include, for example, the ability to prevent the fastener from accidentally separating from the housing during a surgical procedure when using a dedicated driver tip for adjusting the fastener, and the ability to insert and remove the fastener from the housing with a second driver before or after a surgical procedure, for example, to sterilize the fastener and housing separately.

[0008] The backout prevention mechanism includes a body configured to receive a fastener, the body having an inwardly extending flange defining a cavity configured to receive a head of the fastener when the fastener is disposed within the body, the cavity having a proximal opening of the cavity, a fastener having a threaded portion and a head portion, and a locking body disposed in each of at least one radially extending channel of the screw. The head portion has an upper socket configured to interface with a driver for adjusting a position of the fastener within the body, a lower socket, and at least one channel extending radially from the lower socket, the at least one channel sized and shaped to permit translation of the locking body through the channel. The backout prevention mechanism 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 is engaged by a second driver. In a first configuration, engagement of the drive portion of the first driver with the upper socket of the head portion allows the lock body to move radially inward within the channel such that a fastener may be inserted distally into and removed proximally from the body without interference between the lock body and a flange of the cavity. In a second configuration, when a fastener is disposed within the body such that at least one radially extending channel is disposed distally relative to the flange of the cavity, engagement of the drive portion of the second driver with the upper socket includes engagement of a distal end portion of the second driver with a lower socket of the head portion that displaces the lock body radially outward such that the lock 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.

[0009] In some examples, the lock 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 of the fastener within the body in the second configuration. The cavity can define a cylindrical inner wall, and the flange is a radial flange. In some examples, the inner wall of the cavity defines a width greater than a diameter of a head portion of the fastener plus twice the extension distance of the lock body from the head portion in the second configuration.

[0010] The radially extending channel is configured to retain the lock body in a radially extending direction. The lower socket may define a cylindrical inner wall. The upper socket may define a shape configured to interface with a shape of the drive portions of the first and second drivers and to allow for torque transfer from the drive portions to the fastener to adjust a position of the fastener within the body. The body may include a threaded portion configured to receive a threaded portion of the fastener.

[0011] In some examples, in the first configuration, a maximum engagement position between the drive portion of the first driver and the upper socket of the head portion is defined by contact between the drive shaft of the first driver and the upper socket.

[0012] In some examples, 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.

[0013] In some examples, in at least one of the first configuration or the second configuration, the maximum engagement position of the drive portion is defined by contact between a drive feature of the drive portion and an end of a corresponding drive feature in the upper socket.

[0014] Another example of the present disclosure is a surgical instrument having a retractor body configured to couple to an implantable anchor, a first tissue manipulation tool coupled to the retractor body and capable of multi-axial movement relative to the retractor body, and a second tissue manipulation tool coupled to the retractor body and capable of multi-axial movement relative to the retractor body, each of the first tissue manipulation tool and the second tissue manipulation tool coupled to the retractor body via a multi-axial joint, each joint including a screw for selectively locking the multi-axial joint against movement, each manipulation tool and screw including an anti-backout mechanism according to an embodiment of the present disclosure, the manipulation tool including a body of the anti-backout mechanism and the screw including a fastener.

[0015] In some instances, the first and second tissue manipulation tools oppose one another such that they may be moved either toward or away from one another.

[0016] The instrument may further comprise a lock coupled to the body and configured to interface with the anchor extension to selectively lock the position of the body relative to the anchor extension.

[0017] In some examples, each of the first and second tissue manipulation tools may be coupled to the body via a ball-and-socket joint, hi some examples, each of the ball-and-socket joints includes an expansion member configured to selectively lock the ball-and-socket joint against movement.

[0018] Another example of the present disclosure is a 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 within the body, the cavity defining an inwardly extending flange proximal to the cavity, and a fastener having a threaded portion and a head portion, the head portion comprising: an upper socket configured to interface with a driver to adjust a position of the fastener within the body, a lower socket, and at least one channel extending radially from the lower socket, the at least one channel sized and shaped to permit translation of the lock body through the channel. The system also includes a locking body disposed in each of the at least one radially extending channel of the screw, and a locking driver with a distal end region sized and shaped to engage both the upper and lower sockets, the distal end region having a drive portion and a locking portion located distally relative to the drive portion, the drive portion configured to interface with the upper socket to transmit torque to the fastener to adjust a position of the fastener within the body, the locking portion configured to be disposed in the lower socket when the drive portion is interfaced with the upper socket and sized and shaped to displace the locking body radially outward to a position that prevents the locking body within the fastener from being moved proximally beyond the flange. A standard driver with a distal end having a drive portion without a locking portion sized and shaped to move the locking body radially outward is able to transmit torque to the upper socket to adjust a position of the fastener proximally and distally within the body without interference between the locking body and the flange.

[0019] In some examples, the body is a first body and the system further comprises a second body configured to couple to the implantable anchor, the first body defining at least a portion of a manipulation tool connected to the second body and configured to be capable of multi-axial movement relative to the second body, the tissue manipulation tool coupled to the second body via a multi-axial joint, and a position of the fastener within the first body selectively locks the multi-axial joint against movement.

[0020] Yet another embodiment of the present disclosure is a method of assembling and adjusting a position of a fastener within a locking mechanism, the method including: inserting the fastener into a body of the locking mechanism; coupling a first driver to the fastener such that a lock body disposed in a radially extending channel of the fastener is disposed distally of an inwardly extending flange in a cavity of the body, using the first driver to thread the fastener distally into engagement with the body; coupling a second driver to the fastener while the fastener is in threaded engagement with the body, the second driver displaces the lock body radially outwardly such that the lock body interferes with the flange of the channel to prevent proximal movement of the fastener beyond a position where the lock body interferes with the flange; and using the second driver to adjust the position of the fastener within the body by threading the fastener between a maximum proximal position and a maximum distal position defined by the interference between the lock body and the flange. In some examples, the lock body is a ball bearing.

[0021] In some examples, the body includes a collet disposed within the socket, and inserting the fastener into the body includes coupling a distal end of the fastener to an expansion member disposed within the collet, such that adjusting the position of the fastener within the body expands and contracts the collet within the socket to adjust the level of frictional engagement between the collet and the socket.

[0022] In some examples, the body is a first body defining at least a portion of a manipulation tool and the socket is a part of a second body configured to couple to the implantable anchor, and the method further includes coupling a collet to the socket after inserting the fastener into the first body with the first driver, the collet and socket defining a multi-axial joint, and adjusting the position of the fastener within the body using the second driver includes selectively locking the multi-axial joint against movement.

[0023] Any of the above-described features or variations may be applied to any particular aspect or embodiment of the present disclosure in several different combinations, and without an explicit description of any particular combination, this is simply to avoid redundancy in this summary. [Brief description of the drawings]

[0024] The present disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 illustrates one embodiment of a surgical instrument assembly in accordance with the teachings presented herein. [Diagram 2] FIG. 2 is a detailed view of a retractor of the assembly of FIG. 1. [Diagram 3] FIG. 2 is an exploded view of the assembly of FIG. 1. [Figure 4] FIG. 3 is an exploded view of the retractor of FIG. 2. [Diagram 5] FIG. 3 is a partially transparent detail view of the retractor of FIG. 2. [Figure 6] FIG. 3 is a partially transparent bottom detail view of the retractor of FIG. 2. [Figure 7] FIG. 13 is a front perspective view of another embodiment of a surgical instrument assembly in accordance with the teachings presented herein. [Figure 8A] FIG. 8 is a perspective view of an actuation tool of the assembly of FIG. 7. [Figure 8B] FIG. 8B is an alternative view of the working tool of FIG. 8A. [Figure 9] FIG. 8B is a partially transparent perspective view of the working instrument of FIG. 8A. [Figure 10A] FIG. 8 is a perspective view of a distal driver tip of the actuation instrument of the assembly of FIG. 7. [Figure 10B] 8 is a perspective view of an alternative distal driver tip for use with the actuation tool of the assembly of FIG. 7. FIG. [Figure 11A] FIG. 3 is a partially transparent view of one embodiment of a driver-specific backout prevention assembly for use with the locking mechanism of the multi-axis joint of the retractor of FIG. [Figure 11B] FIG. 11B is a cross-sectional view of the assembly of FIG. 11A showing the screw in a proximal position. [Figure 11C] FIG. 11B is a partially transparent view of the assembly of FIG. 11A showing the screw in a distal position. [Figure 11D] FIG. 11D is a cross-sectional view of the assembly of FIG. [Figure 12A] FIG. 11C is a partially transparent view of the driver specific backout prevention assembly of FIGS. 11A-11D being used with the driver tip of FIG. 10B. [Figure 12B] FIG. 12B is a cross-sectional view of the assembly of FIG. 12A showing the screw in a distal position with the anti-backout driver tip partially inserted. [Figure 12C] FIG. 12B is a partially transparent view of the assembly of FIG. 12A showing the anti-backout driver tip fully inserted. [Figure 12D] FIG. 12D is a cross-sectional view of the assembly of FIG. 12C. [Figure 12E] FIG. 12B is a partially transparent view of the assembly of FIG. 12A showing the anti-backout driver tip fully inserted and the screw fully backed out, with the anti-backout feature engaging the internal flange of the body. [Figure 12F] FIG. 12F is a cross-sectional view of the assembly of FIG. 12E. [Figure 12G] FIG. 12B is a cross-sectional view of the assembly of FIG. 12A showing the screw in a proximal position with the anti-backout driver tip partially inserted. [Figure 12H] FIG. 12C is a cross-sectional view of the assembly of FIG. 12G. [Figure 13A]11A-12H, showing a top cross-sectional view of the driver specific backout prevention assembly of FIGS. 11A-12H with the backout prevention driver tip disposed within the socket of the screw. FIG. [Figure 13B] FIG. 13B is a top cross-sectional view of the assembly of FIG. 13A with a standard driver tip disposed within the socket of the screw. [Figure 14] 11A-12H are photographs of one embodiment of the driver specific backout prevention assembly of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Certain exemplary embodiments will now be described to provide a general understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will appreciate that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of the disclosure is defined solely by the claims. Features illustrated or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the disclosure.

[0026] Furthermore, to the extent that linear or circular dimensions are used in describing the disclosed devices and methods, such dimensions are not intended to limit the types of shapes that may be used with such devices and methods. Equivalents to such linear and circular dimensions may be determined for any geometric shape. Furthermore, in this disclosure, like-numbered components of the embodiments generally have similar characteristics. Furthermore, the size and shape of the device and its components may depend at least on the anatomy of the subject in which the device will be used, the size and shape of the components in which the device will be used, and the method and procedure in which the device will be used.

[0027] 1-6 illustrate an exemplary surgical instrument assembly 100 in accordance with the teachings presented herein. The assembly 100 may be used in a variety of surgical procedures, including spinal procedures such as microsurgical osteotomies, spinal decompressions, spinal fusions, and the like. In general, the assembly 100 may include a support instrument 102 that couples to an implanted anchor 104, such as a pedicle screw or other bone screw. The assembly 100 may further include a retractor 106 coupled to the support instrument 102. Other components not shown herein may be included in or coupled to the assembly 100. Such components may include, for example, any of a variety of cameras or visualization systems, and any of a variety of other surgical instruments.

[0028] An exemplary method of using the assembly 100 of FIGS. 1-6 may include one or more of the following steps, performed in any of a variety of orders: a) making an incision in the patient's skin; b) percutaneously inserting an implantable anchor, such as a pedicle screw or other bone screw, through the incision; c) coupling a support device 102 to the implanted anchor (e.g., a pedicle anchor); d) coupling a tissue retractor to the device; e) effecting medial-lateral retraction of the tissue surrounding the incision; f) coupling an optical visualization device to the tissue retractor and / or the device; g) resecting a portion of the superior articular process and / or performing a microsurgical decompression procedure; h) extracting disc material, including removing cartilaginous material from the vertebral endplates; i) inserting an interbody device; and j) deploying a stabilization mechanism to stabilize the intervertebral segment.

[0029] The retractor assembly 106 described above, in combination with the support instrument or anchor extension 102 and the implanted anchor 104, may be used, for example, to widen an incision made in the patient's skin and tissue to allow better access to a surgical site. As a further example, in some embodiments, these components may be anchored to a single implanted screw or anchor to form an assembly that provides medial-lateral tissue retraction to increase access for various surgical procedures. Retracting the skin and underlying tissue surrounding the incision medially and laterally may provide a wider opening and working channel between tissue manipulation tools to access the patient's spine or intervertebral space. In some embodiments, the working channel may extend to encompass adjacent anchors implanted in the adjacent vertebrae. Once the tissue of the incision walls has been retracted to form a working channel, any of a variety of surgical procedures may be performed by introducing one or more instruments through the working channel defined by the tissue manipulation tools of the retractor assembly. For example, procedures on the disc space, such as disc replacement, discectomy, endplate preparation, fusion cage insertion, bone graft delivery, etc., may be performed by passing instruments or implants through the working channel.

[0030] Returning to Figures 1-6, Figure 1 illustrates one embodiment of a surgical instrument assembly 100 including a support instrument 102 coupled to an implantable anchor 104 and a tissue retractor 106. Further details regarding embodiments of the assembly 100 are described in U.S. patent application Ser. No. 16 / 139,409, entitled "PATIENT-MOUNTED SURGICAL SUPPORT," and U.S. patent application Ser. No. 16 / 139,434, entitled "PATIENT-MOUNTED SURGICAL RETRACTOR," both filed Sep. 24, 2018. Further details regarding embodiments of the implantable anchor 104 can be found in U.S. patent application Ser. No. 15 / 208,872, entitled "BONE ANCHOR ASSEMBLIES AND RELATED INSTRUMENTATION," filed Jul. 13, 2016. Further details regarding particular embodiments of retractors that may be used in surgical assembly 100 can be found below and in U.S. Patent No. 7,491,168, the entire contents of each of which are incorporated herein by reference.

[0031] In general, the support device may include an elongate body 108 having a laterally extending fork formed at its distal end that may interface with a narrow neck of the anchor 104. The fork may 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 may be sized to receive a portion of the implantable anchor 104. For example, the projections may be configured to fit around a proximal portion of a bone anchor that may be part of a modular monoaxial or polyaxial pedicle screw. Such an anchor may include a generally cylindrical distal shank portion having threads for tapping into bone, as well as a narrow neck proximal to the shank portion and a wider proximal head. The proximal head may be generally spherical or hemispherical in shape and may be configured to couple with a receiver head before or after implantation in the patient's bone. The elongated body may also include a lock configured to exert a resisting force on the head of the anchor to control the multi-axial movement of the instrument 102 relative to the anchor 104. As shown in FIG. 3, the lock may include a lock body 302 that is coupled to the elongated body 108 and is translatable relative to the elongated body along a longitudinal axis 304 of the elongated body. The lock body 302 may have a generally elongated shape to facilitate coupling with the elongated body 108 and translating or sliding along or relative to the elongated body. The lock may be actuated by a lock screw 305 that may cause distal translation of the lock body 302 when further threaded into the elongated body 108. The lock body 302 may further include a laterally extending ring-shaped protrusion 306 at its distal end that may be configured to contact and exert a resisting force on the proximal head of the anchor 104. Ring-shaped protrusion 306 may define a lumen for maintaining access to a drive feature formed on the proximal end of the head of anchor 104.This lumen, along with the lateral extensions of projections 306 and the forks formed at the distal end of elongate body 108, may allow instrument 100 to be oriented such that the longitudinal axis of the instrument is laterally offset or non-coaxial with the longitudinal axis of anchor 104. Such a configuration may allow a driver or other instrument to access the drive features of anchor 104 even when instrument 100 is coupled. This allows flexibility for implanting anchor 104 both before and after instrument 100 is coupled to anchor 104.

[0032] Returning to FIG. 2, a more detailed schematic diagram of one embodiment of the tissue retractor 106 is presented. The retractor 106 can include a body 202 that can be configured to couple to a support instrument or anchor extension 102. The first and second tissue manipulation tools 204, 206 can be coupled to the body 202, for example, by rigid arms 208, 210, respectively. Each of the first and second tissue manipulation tools 204, 206 can be capable of multi-axis movement relative to the body via multi-axis joints 212, 214, such as ball-and-socket joints. Such joints can allow the tissue manipulation tools 204, 206 to move relative to one another in a variety of ways. For example, the tools 204, 206 can be pivoted toward or away from one another about an axis that extends parallel to the longitudinal axis of the support instrument 102 (e.g., an axis parallel to axis 304 in FIG. 3). The tools 204, 206 may also be pivoted toward or away from one another, for example about axes transverse or oblique to the axis 304. For example, the tools 204, 206 may be moved tip-wise relative to one another, where the distal ends of the tools are moved toward or away from one another by a greater amount than the proximal ends of the tools. In some embodiments, moving tip-wise may include moving the distal ends of the tools away from one another, while the proximal ends of the tools are moved toward one another or do not move, thus leaving the distance between the proximal ends of the tools unchanged. Additionally, each multi-axis joint 212, 214 may include a lock 216, 218 that may be used to selectively lock the position of the associated tissue manipulation tool 204, 206 or impose a counter force that prevents movement in the absence of at least a threshold level of force.

[0033] As mentioned above, the tissue retractor 106 may be configured to couple to a support device or anchor extension 102 and may be configured to slide along the length of such device to adjust the height of the retractor relative to the implanted anchor 104. As shown in FIG. 2, the retractor body 202 may include a closed or partially open lumen or recess 220 that is configured to receive a portion of the support device 102, such as the generally cylindrical elongated body 108 (see FIG. 1). The retractor 106 may further include features to selectively lock the position of the retractor relative to the support device 102, such as a spring-loaded protrusion or tab 222 that may engage with a ratchet rack or other series of recesses or other surface features formed on the support device elongated body 108. Additionally, in some embodiments, the locking feature 222 may be configured to prevent not only movement along the length of the support device 102, but also rotation thereabout. An actuator 224, such as the sliding or translating member shown, may be included to allow a user to easily retract the protrusion 222 against the biasing force of a spring or other biasing element disposed within the body 202 of the retractor 106.

[0034] In addition to adjusting the position of the retractor 106 along the length of the support device 102, the length of each of the tissue manipulation tools 204, 206 may also be adjusted. For example, in some embodiments, the tissue manipulation tools 204, 206 may each include an extension 226, 228 that may be configured to translate relative to the tissue manipulation tool 204, 206. Translating either extension 226, 228 proximally or distally relative to the associated tool 204, 206 may change the overall length of the tool and may also allow the tool to reach deeper into tissue, for example, when the retractor 106 is mounted higher than the patient's skin surface along a more proximal portion of the support device's elongate body 108.

[0035] FIG. 3 shows a partial exploded view illustrating how the retractor 106 may be coupled to the support device 102 by sliding the retractor downward or distally over a proximal portion of the support device. For example, the recess or lumen 220 of the retractor 106 may be aligned with the generally cylindrical elongated body 108 of the support device, and the retractor may be advanced downward or distally along axis 304. While advancing the retractor relative to the support device, the user may manually retract the spring-loaded tab or protrusion 222 using the sliding lever 224 to allow free movement of the retractor relative to the support device. Once the desired position is reached, the user may release the lever 224 to allow the protrusion 222 to be advanced into engagement with a complementary recess or other feature formed on the elongated body 108 to maintain the relative positioning of the retractor and support device. In other embodiments, the complementary features formed on the elongate body 108 and the protrusions 222 may be formed as a biased ratchet, where, for example, distal advancement of the retractor can be accomplished without actuating the lever 224, but proximal retraction of the retractor 106 relative to the instrument 102 requires actuation of the lever 224 to retract the biased protrusions 222.

[0036] 4-6 show the retractor 106 in various exploded and partially transparent views to better illustrate the interaction of the various components of the retractor 106. For example, the multi-axis joints 212, 214 can be seen in greater detail. Each multi-axis joint 212, 214 can include a socket 402, 404 formed in the body 202 of the retractor 106. Each of the arms 208, 210 coupled to the tissue manipulation tools 204, 206 can have a generally ball-shaped proximal end 406, 408 (e.g., a collet) that includes one or more relief slots formed therein such that various portions of the proximal end (e.g., petal 428) can deform relative to other portions. The locks 216, 218 may be coupled to each arm 208, 210 by cooperation between threads 410, 412 formed on the locks and threads 414, 416 formed on the inner surfaces of through holes in the arms 208, 210. Additionally, an extension member 420 may be disposed at a distal end of each lock 216, 218 and configured within the ball-shaped distal end 408 such that adjustment of the position of the lock 218 by movement along the threads 412 may result in the extension member 420 moving distally within the ball-shaped proximal end 408 to bias the petals 428 outwardly, or alternatively, the extension member 420 may be retracted proximally to seat further within the curved inner surface of the petals 408 and not bias the petals outwardly. The lock assembly 499 may include the lock 218 and a portion of the arm 210 to which the lock 218 is operably coupled.

[0037] 5 and 6, when assembled, the extension members 418, 420 can be disposed within the generally ball-shaped proximal ends 406, 408 in an unlocked (e.g., retracted) position that allows for disposing the extension members 418, 420 within one of the sockets 402, 404 of the body 202. To lock the ball-shaped proximal ends 406, 408 within and relative to one of the sockets 402, 404, the locks 216, 218 can be rotated relative to the arms 208, 210 such that the extension members 420 are advanced further into the ball-shaped proximal ends 408 by the threaded connection between the arms 208, 210 and the locks 216, 218. Advancement of the locks 216, 218 into the ball-shaped proximal ends 408 may cause the expansion members 418, 420 formed at the distal end of each lock to expand the petals 428 radially outward inside the sockets 402, 404. As the petals 428 of the ball-shaped proximal ends 406, 408 expand radially, they may be urged into contact with the sidewalls of the sockets 402, 404. This may cause an increase in frictional forces between the sockets 402, 404 and the ball-shaped proximal ends 406, 408 of the arms 208, 210. Furthermore, once the locks 216, 218 are fully advanced, the force of the expansion members 418, 420 against the petals 428 may effectively lock the ball-shaped proximal ends 406, 408 in a given position, thereby preventing any movement of the arms 208, 210 or the tissue manipulation tools 204, 206 coupled thereto.

[0038] 7 illustrates an alternative embodiment of a surgical instrument assembly 1000 including an implantable anchor 104 and a support instrument 1002 coupled to a tissue retraction assembly 1006. Also illustrated is an embodiment of a driver 1008 that may be used to actuate locks 1010, 1012 that may selectively permit or prevent multi-axial movement of opposing tissue manipulation instruments 1014, 1016 relative to a body 1018 of the retraction assembly 1006.

[0039] 8A-9 show the driver 1008 in further detail. In some embodiments, the driver 1008 can include a housing 1802 disposed about a drive shaft 1804 that couples at its proximal end to a handle 1806. A distal end 1812 of the drive shaft 1804 can be configured to interface with a proximal end of the locks 1010, 1012 of the tissue retractor assembly 1006 to impart an actuation torque. The driver 1008 can also include a stabilization shaft 1810 that is coaxially disposed about the drive shaft 1804 and coupled to the housing 1802 and the interface 1808. The interface 1808 may include opposing slots or notches 1814, 1816 that may receive portions of one of the arms 1302, 1304 when the interface is disposed over one of the locks 1010, 1012 such that the distal end 1812 of the drive shaft 1804 engages the lock. The user may then hold the housing 1802 steady to counter any tendency of the retractor assembly 1006 to rotate or otherwise move in response to pivoting the handle 1806. More specifically, the rigid non-rotating connection between the housing 1802, stabilizing shaft 1810, and interface 1808, combined with the inability of the interface 1808 to rotate relative to the arms 1302, 1304 because of the slots 1814, 1816, may provide effective stability when the user pivots the handle 1806 while holding the base 1802.

[0040] One problem that occurs with the above type of instruments is that a user may unintentionally back out the screw 419 of the lock 216, 218 too much during the procedure. This may result in the screw 419 becoming disengaged from the threads 414, 416 of the tissue manipulation tool arm 208, 210. To prevent this, embodiments of the present disclosure provide a mechanism to prevent the screw 419 of the lock, 216, 218, also called a poly ball locking screw, from being unintentionally removed during the procedure. However, because the screw 419 also needs to be disassembled for cleaning and initial assembly, the screw 419 needs to be selectively removable beyond its backstop. Thus, a backout prevention mechanism is provided and described herein that allows for selective removal of the screw 419 beyond the backstop. This feature may be added to the locking assembly 499 where backing out of the screw 419 is necessary to allow the petals 428 of the ball-shaped proximal end 408 to collapse and insert into the socket 404; however, backing out completely would completely disengage the screw 419 from the threads 416 and / or the extension member 420. This creates the need for a backstop to notify the user when the screw 419 is sufficiently backed out and / or to prevent unintentional separation of the screw 419 from the extension member 420, while still allowing adjustment of the screw 419 to allow adjustment of the locking assembly 499.

[0041] One purpose of the backout prevention mechanism is to allow backout prevention to occur without permanently capturing the screw or lock 218, as this is undesirable due to the challenges posed when sterilizing the components. For example, the assembly 499 may need to be fully disassembled after use and each component fully sterilized, which requires separating the screw 419 from the threads 416 as well as separating the extension member 420 from the screw 419. If a more traditional captured screw were utilized to prevent unintentional backout, complete disassembly would not be possible and thorough cleaning and sterilization may be difficult. Thus, the present disclosure provides a mechanism for selective backout prevention based on a driver utilized by the user, which allows selective prevention of backout during a procedure, but also allows complete disassembly for cleaning and sterilization. As described in more detail below, the lockout assembly 499 may include a fastener (e.g., screw 419) and a body (e.g., the portion of the arm 210 that receives the screw 419) that cooperate to provide an anti-backout mechanism that allows the screw 419 to be assembled or disassembled or adjusted with a first driver and adjusted with a second driver, such that the second driver cannot be used to disassemble or back out the screw 419 from the arm 210.

[0042] FIG. 10A is a perspective view of one embodiment of a driver tip 1813 of a distal end 1812 that may be utilized, for example, on the actuation tool 1008 of the assembly of FIG. 7. The device configuration of FIG. 10A may also be referred to as a standard driver. As described in more detail below, the standard driver 1812 may be used to fully adjust the positioning of a lock 218 or other fastener within a lock assembly 499 (or lock assembly 599 as shown in FIGS. 11A-14), including initial assembly or subsequent disassembly of the lock assembly 499. FIG. 10B is a perspective view of an alternative distal driver tip for use with the actuation tool of the assembly of FIG. 7. FIG. 10B shows a backout prevention driver 1901 including a distal end 1912 having two distinct regions, a proximal driver tip 1913 and a distal interference element 1914 extending between the driver tip 1913 and a terminal end of the distal end 1912. In operation, as discussed in more detail below, the use of the anti-backout driver 1901 in conjunction with the lock assembly 499, 599 prevents the fastener or lock 218 from being disassembled or completely backed out of the body 210.

[0043] 10A and 10B, driver tips 1813, 1913 are shown as having a hexlobe drive feature, however this is one of many common driver features and is shown by way of example only. Many different driver features may be used with the embodiments disclosed herein.

[0044] 11A-11D are partial see-through and cross-sectional views of a driver specific backout prevention assembly 599 for use with the screw 419 and lock 218 of the polyaxial joint of the retractor of FIG. 2. FIG. 11A is a partial see-through view, and FIG. 11B is a cross-sectional view, both showing the driver specific backout prevention assembly 599 having a standard driver 1812 disposed in a socket 2218 of a screw 519 disposed in a body 2210. The body 2210 can be, for example, the portion of the arm 210 that receives the screw 519. The screw 519 can have a threaded portion that screws into a corresponding threaded portion of the body 2210. However, in some examples, the body 2210 and the portion having the corresponding thread 416 can be separate pieces, and in still other examples, the screw 519 and the body 2210 can be connected by means other than threads, such as a pin and channel system, or other means known in the art. The body 2210, in turn, defines a cavity 2215 for receiving a head portion 2218 or socket of the screw 519. The cavity 2215 includes an inwardly extending flange 2211 or protrusion that functions as a backstop when an anti-backout driver is disposed within the head portion 2218 (as shown in FIGS. 12A-12H ).

[0045] 11A and 11B, the head portion of the screw 419 defines an upper socket 2220 and a lower socket 2250, and the drive tip 1813 can only engage the upper socket 2220. The head portion 2218 also includes one or more channels 2219 extending radially from the lower socket 2250. Each channel 2219 includes a locking body, such as the illustrated ball bearing 2240. In operation, the backout prevention assembly 599 allows the standard driver 1812 to fully insert and remove the screw 519 from the body 2210 because the ball bearings 2240 disposed within the channels 2219 can be biased radially inward by the flange 2211, at least partially into the lower socket 2250, as shown, and thus do not interfere with the flange 2211. 11A and 11B thus show the anti-backout assembly 599 in the "up" position with a standard driver 1812, where the male hex lobe feature of the driver tip 1813 bottoms out on the female lobe within the upper socket 2220 and the ball bearings 2240 are free to move inwardly to allow removal of the screw 519 from the body 2210. FIGs. 11C and 11D show the anti-backout assembly 599 in the "down" position with a standard driver 1812. Additionally, distal advancement of the screw 419 is limited by the interaction of the distal facing surface of the head portion 2218 with the proximal facing surface of the cavity, as shown in FIG.

[0046] 12A-12H are partial see-through and cross-sectional views of the driver specific backout prevention assembly 599 of FIGS. 11A-11D being used with the backout prevention driver 1901 of FIG. 10B. FIGS. 12A and 12B show the insertion of the distal end 1912 of the backout prevention driver 1901 into the head portion 2218 of the screw, with the screw 519 in the "down" position and the interference element 1914 disposed within the upper socket 2220. In this position, the interference element 1914 lacks an engagement feature, so the interference element 1914 cannot engage the upper socket 2220 to drive the screw 519. Additionally, the ball bearing 2240 is not constrained by anything disposed within the lower socket 2250 and is free to move.

[0047] 12C and 12D, where the features (e.g., male hex lobes) of the driver 1913 bottom out on corresponding features (e.g., female lobes) of the upper socket 2220 and the interference element 1914 is disposed within the lower socket 2250. The presence of the interference element 1914 displaces the ball bearing 2240 radially outward from the head portion 2218 until it extends into the cavity 2215 of the body 2210. As shown in FIGS. 12E and 12F, the ball bearing 2240 extends from the head portion beyond the outer diameter of the head portion to a distance where it interferes with the flange 2211 when the screw 519 is driven proximally.

[0048] 12E and 12F, the backout prevention driver 1901 is used to back out the screw 519 from the body 2210 until the ball bearing 2240 reaches an interference position (indicated by circle 2299) with the flange 2211. The backout prevention driver 1901 cannot back out the screw 519 beyond the position shown because the presence of the interference element 1914 in the lower socket 2250 will prevent the ball bearing 2240 from moving radially inward beyond the inner diameter of the flange 2211. Thus, once the screw 519 is disposed within the body 2210 with the channel 2219 past the flange 2211, the backout prevention driver 1901 can only be used to adjust the position of the screw 519 such that the length 2299 of the cavity 2215 allows the locking ball bearing 2240 to be below the head portion 2218 when it abuts the flange 2211.

[0049] 12G and 12H show removal of the anti-backout driver 1901 from the head portion 2218, thereby allowing the ball bearings to move radially inward into the lower socket 2250, thereby allowing the screws 519 to be retracted proximally past the flange 2211, for example, using a standard driver 1812.

[0050] 13A and 13B are top cross-sectional views of the lower socket 2250 of the driver specific backout prevention assembly of FIGS. 11A-12H, with FIG. 13A showing the ball bearings 2240 in their displaced position (e.g., by a safety feature 1914 disposed within the lower socket 2250) and FIG. 13B showing the ball bearings 2240 in a "free" position when there is sufficient room in the lower socket 2250 for the ball bearings to move inward beyond the extent to which they can interfere with the flange 2211 when a standard driver trip 1813 is disposed within the socket. In some examples, as shown in FIG. 13B, the channel 2219 can include an inner abutment 2251 to prevent the ball bearings from falling into and out of the lower socket 2250 and the channel 2219. In some embodiments, the channel 2219 can include an outer abutment 2251 to prevent the ball bearings from falling out of the head portion 2218 when the head portion 2218 is removed from the body 2210.

[0051] While the lock body is shown as a ball bearing 2240, other lock bodies are contemplated, such as a pin, which may include a spring biasing the lock body inward to ensure that it does not get stuck in an interference position and to prevent disengagement of the screws 519.

[0052] 14 is a photograph of one embodiment of the driver specific backout prevention assembly 599 of FIGS. 11A-12H, showing the ball-shaped distal end 408 of the body 2210 having a cavity 2215 (not shown) and a screw 519 configured to adjust the position of a tapered member (not shown) disposed at the end of the screw relative to a conical inner surface of the ball-shaped proximal end 408 to expand the ball-shaped proximal end 408. The head portion 2218 of the screw 519 includes a ball bearing 2240 disposed within the channel 2219. FIG. 14 also shows an exemplary backout prevention driver 1901 having a driver 1913 and an interference element 1914 configured to engage a socket in the head portion 2218, as described herein.

[0053] It should be noted that any order of method steps depicted or suggested in the above description or the accompanying drawings should not 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 orders. Additionally, the methods described are merely exemplary embodiments, and various other methods including additional or fewer steps are within the scope of the present disclosure.

[0054] The instruments disclosed herein can be constructed from any of a variety of known materials. Exemplary materials include materials suitable for use in surgical applications, including, for example, metals such as stainless steel, titanium, nickel, cobalt chrome, or alloys and combinations thereof, polymers such as PEEK, ceramics, carbon fiber, and the like. Various components of the instruments disclosed herein can have various degrees of stiffness or flexibility appropriate for their use. The size of the device can also vary widely depending on the intended use and the anatomy of the surgical site. Furthermore, certain components can be formed from different materials than other components. One or more components or portions of the instruments may be formed from radiopaque materials to facilitate visualization under fluoroscopy and other imaging techniques, or may be formed from radiolucent materials so as not to interfere with visualization of other structures. Exemplary radiolucent materials include carbon fiber and high strength polymers.

[0055] The devices and methods disclosed herein can be used in minimally invasive and / or open surgery. Although the devices and methods disclosed herein are generally described in the context of spinal surgery in human patients, it will be understood that the methods and devices disclosed herein can be used in any of a variety of surgical procedures or in non-surgical procedures with any human or animal subject.

[0056] 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 parts, and subsequent reassembly. Specifically, the device can be disassembled and any number of the particular parts or portions of the device can be selectively replaced or removed in any combination. After 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 use of such techniques, and the resulting reconditioned device, are all within the scope of the present application.

[0057] The devices described herein may be processed before being used in a surgical procedure. First, new or used instruments may be obtained and cleaned as necessary. The instruments may then be sterilized. In one sterilization technique, the instruments may be placed in a closed and sealed container, such as a plastic bag or a TYVEK bag. The container and its contents may 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 instruments and in the container. The sterilized instruments can then be stored in the sterile container. The sealed container can keep the instruments sterile until they are opened in the medical facility. Other forms of sterilization known in the art are also possible. These can include beta or other radiation, ethylene oxide, steam, or liquid baths (e.g., cold immersion). Depending on the materials used, the presence of electrical components, etc., certain forms of sterilization techniques may be more suitable for use with different pieces of equipment.

[0058] Those skilled in the art will appreciate further features and advantages based on the above-described embodiments. Thus, the present disclosure is not limited by what has been particularly shown and described. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

[0059] [Embodiment] (1) A backout prevention mechanism comprising: 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 within the body, the cavity having an inwardly extending flange defining a proximal opening of the cavity; 1. 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; The lower socket, at least one channel extending radially from said lower socket, said channel sized and shaped to permit translation of a lock body therethrough; a locking body disposed in each of the at least one radially extending channel of the screw; the backout prevention mechanism 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 is engaged by a second driver; in the first configuration, engagement of the drive portion of the first driver with the upper socket of the head portion allows the locking body to move radially inward within the channel such that the fastener may be inserted distally into and removed proximally from the body without interference between the locking body and the flange of the cavity; and an anti-backout mechanism including engagement of a drive portion of a second driver with the lower socket of the head portion that displaces the locking body radially outwardly such that the locking body interferes with the flange of the channel when the fastener is advanced proximally by the second driver, when the fastener is disposed within the body such that the at least one radially extending channel is disposed distally relative to the flange of the cavity, such that the fastener cannot be removed from the body by the second driver. (2) The backout prevention mechanism of embodiment 1, wherein the lock body is a ball bearing. (3) A backout prevention mechanism as described in embodiment 1 or 2, wherein the cavity defines a length below the flange, and the length of the cavity defines a maximum possible adjustment distance of the fastener within the body in the second configuration. (4) The backout prevention mechanism according to any one of the first to third embodiments, wherein the cavity defines a cylindrical inner wall and the flange is a radial flange. (5) The backout prevention mechanism of embodiment 4, wherein the inner wall of the cavity defines a width greater than a diameter of the head portion of the fastener plus twice the extension distance of the lock body from the head portion in the second configuration.

[0060] (6) The backout prevention mechanism according to any one of the first to fifth embodiments, wherein the radially extending channel is configured to hold the lock body in the radially extending direction. (7) The backout prevention mechanism according to any one of claims 1 to 6, wherein the lower socket defines a cylindrical inner wall. (8) A backout prevention mechanism as described in any one of embodiments 1 to 7, wherein the upper socket defines a shape configured to cooperate with a shape of the drive portion of the first driver and the second driver and to enable transmission of torque from the drive portion to the fastener to adjust the position of the fastener within the body. (9) A backout prevention mechanism according to any one of claims 1 to 8, wherein the body includes a threaded portion configured to receive the threaded portion of the fastener. (10) A backout prevention mechanism as described in any one of embodiments 1 to 9, wherein in the first configuration, a maximum engagement position between the driving portion of the first driver and the upper socket of the head portion is defined by contact between a drive shaft of the first driver and the upper socket.

[0061] (11) A backout prevention mechanism as described in any one of embodiments 1 to 10, wherein 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. (12) A backout prevention mechanism as described in any one of embodiments 1 to 11, wherein in at least one of the first configuration or the second configuration, a maximum engagement position of the drive portion is defined by contact between a drive function of the drive portion and an end of a corresponding drive function in the upper socket. (13) A surgical instrument, a retractor body configured to couple to an implantable anchor; a first tissue manipulation tool coupled to the retractor body and capable of multi-axis movement relative to the retractor body; a second tissue manipulation tool coupled to the retractor body and capable of multi-axial movement relative to the retractor body; each of the first tissue manipulation tool and the second tissue manipulation tool is coupled to the retractor body via a multi-axis joint; each joint including a screw for selectively locking said multi-axis joint against movement; A surgical instrument, wherein each manipulating implant and screw are provided with a backout prevention mechanism according to any one of embodiments 1 to 12, the manipulating implant including the body of the backout prevention mechanism, and the screw including the fastener. (14) The apparatus of embodiment 13, wherein the first tissue manipulation tool and the second tissue manipulation tool are opposed to each other so that they can be moved either toward or away from each other. (15) The instrument of any one of claims 13 to 14, further comprising a lock coupled to the body and configured to interface with the anchor extension to selectively lock the position of the body relative to the anchor extension.

[0062] (16) The instrument according to any one of embodiments 13 to 15, wherein each of the first tissue manipulation tool and the second tissue manipulation tool is coupled to the main body via a ball-and-socket joint. (17) The device of any one of embodiments 13 to 16, wherein each of the ball and socket joints includes an extension member configured to selectively lock the ball and socket joint against movement. (18) A backout prevention system comprising: 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 within the body, the cavity defining an inwardly extending flange proximal to the cavity; 1. 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; The lower socket, at least one channel extending radially from said lower socket, said channel sized and shaped to permit translation of a lock body therethrough; a locking body disposed in each of the at least one radially extending channel of the screw; a lock driver comprising a distal end region sized and shaped to engage both the upper and lower sockets, the distal end region having a drive portion and a lock portion distal to the drive portion, the drive portion configured to interface with the upper socket to transmit torque to the fastener to adjust the position of the fastener within the body, the lock portion configured to be disposed within the lower socket when the drive portion is interfaced with the upper socket, and sized and shaped to displace the lock body radially outwardly to a position that prevents the lock body within the fastener from moving proximally beyond the flange; A backout prevention system in which a standard driver having a distal end having a drive portion without a locking portion sized and shaped to move the lock body radially outward is capable of transmitting torque to the upper socket to adjust the position of a fastener within the body proximally and distally without interference between the lock body and the flange. (19) The body is a first body, and the system further comprises a second body configured to couple to an implantable anchor; the first body defines at least a portion of a manipulation implement connected to the second body and configured for multi-axis movement relative to the second body; the tissue manipulation tool is coupled to the second body via a polyaxial joint; 19. The backout prevention system of claim 18, wherein the position of the fastener within the first body selectively locks the multi-axis joint against movement. (20) A method for assembling and adjusting the position of a fastener in a locking mechanism, comprising the steps of: Inserting the fastener into a body of the locking mechanism; coupling the first driver to the fastener such that a locking body disposed within a radially extending channel of the fastener is disposed distally of an inwardly extending flange within a cavity of the body, and using the first driver to thread the fastener distally into engagement with the body; coupling a second driver to the fastener with the fastener in threaded engagement with the body, the second driver displacing the locking body radially outwardly such that the locking body interferes with the flange of the channel to prevent proximal movement of the fastener beyond a point where the locking body interferes with the flange; and adjusting the position of the fastener within the body using the second driver by threading the fastener between a maximum proximal position and a maximum distal position defined by the interference between the lock body and the flange.

[0063] (21) The method of claim 20, wherein the lock body is a ball bearing. (22) The method of any one of claims 20 to 21, wherein the body includes a collet disposed within a socket, and inserting the fastener into the body includes coupling a distal end of the fastener to an expansion member disposed within the collet, whereby adjusting the position of the fastener within the body expands and contracts the collet within the socket to adjust a level of frictional engagement between the collet and the socket. (23) The method of embodiment 22, wherein the body is a first body defining at least a portion of a manipulation tool and the socket is part of a second body configured to couple to an implantable anchor, the method further comprising coupling the collet to the socket after inserting the fastener into the first body with the first driver, the collet and the socket defining a multi-axis joint, and adjusting the position of the fastener within the body using the second driver includes selectively locking the multi-axis joint against movement.

Claims

1. A backout prevention mechanism that prevents a fastener from coming off a main body, the body configured to receive the fastener, the body defining a cavity configured to receive a head portion of the fastener when the fastener is disposed within the body, the body having an inwardly extending flange defining a proximal opening of the cavity; The fastener having a threaded portion and the 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; The lower socket, the fastener comprising at least one channel extending radially from the lower socket, the at least one channel sized and shaped to permit translation of a lock body through the at least one channel; the locking body disposed in each of the at least one channel of the fastener; A first driver; a second driver; the backout prevention mechanism has a first configuration when the head portion of the fastener is engaged by the first driver and a second configuration when the head portion of the fastener is engaged by the second driver; in the first configuration, the head portion of the fastener is not engaged with the second driver, in the second configuration, the head portion of the fastener is not engaged with the first driver, when the backout prevention mechanism is in the first configuration, the backout prevention mechanism is not in the second configuration, when the backout prevention mechanism is in the second configuration, the backout prevention mechanism is not in the first configuration; in the first configuration, engagement of the drive portion of the first driver with the upper socket of the head portion allows the locking body to move radially inward within the at least one channel such that the fastener may be inserted distally into and removed proximally from the body without interference between the locking body and the flange of the body; a backout prevention mechanism including engagement of a distal end portion of the second driver with the locking body such that when the fastener is disposed within the body such that the at least one channel is disposed distally relative to the flange of the body, in the second configuration, engagement of the drive portion of the second driver with the upper socket displaces the locking body radially outwardly such that the locking body interferes with the flange of the body when the fastener is advanced proximally by the second driver such that the fastener cannot be removed from the body by the second driver.

2. 2. The backout prevention mechanism of claim 1, wherein the lock body is a ball bearing.

3. 3. The backout prevention mechanism of claim 1, wherein the cavity defines a cylindrical inner wall and the flange is a radial flange.

4. 4. The backout prevention mechanism of claim 3, wherein the inner wall of the cavity defines a width greater than a diameter of the head portion of the fastener plus twice the extension of the lock body from the head portion in the second configuration.

5. The backout prevention mechanism according to any one of claims 1 to 4, wherein the at least one channel is configured to retain the lock body in the radially extending direction.

6. The backout prevention mechanism of any one of claims 1 to 5, wherein the lower socket defines a cylindrical inner wall.

7. 7. The backout prevention mechanism of claim 1, wherein the upper socket defines a shape configured to cooperate with a shape of the drive portion of the first driver and the second driver and to allow torque transfer from the drive portion to the fastener to adjust the position of the fastener within the body.

8. The backout prevention mechanism of any one of claims 1 to 7, wherein the body comprises a threaded portion configured to receive the threaded portion of the fastener.

9. 1. A surgical instrument comprising: a retractor body configured to couple to an implantable anchor; a first tissue manipulation tool coupled to the retractor body and capable of multi-axis movement relative to the retractor body; a second tissue manipulation tool coupled to the retractor body and capable of multi-axis movement relative to the retractor body; each of the first tissue manipulation tool and the second tissue manipulation tool is coupled to the retractor body via a multi-axis joint; each multi-axis joint including a screw for selectively locking said multi-axis joint against movement; Each of the first tissue manipulation tool and the second tissue manipulation tool and the screw are provided with a backout prevention mechanism according to any one of claims 1 to 8, wherein each of the first tissue manipulation tool and the second tissue manipulation tool includes the body of the backout prevention mechanism and the screw includes the fastener.

10. 10. The apparatus of claim 9, wherein the first and second tissue manipulation tools oppose each other such that they may be moved either toward or away from each other.

11. 11. The instrument of claim 9 or 10, further comprising a lock coupled to the body and configured to interface with an anchor extension coupled to the anchor to selectively lock a position of the body relative to the anchor extension.

Images