Retro guidewire reamers include a drill having a tubular shaft configured to be disposed over a guidewire and at least one cutting member movably disposed adjacent the distal end of the shaft. A slide actuator is moveably coupled to the shaft and to an actuator wire slidable along the shaft. The actuator wire is operative to move the at least one cutting member between a closed position and a deployed position when the slide actuator is moved along the shaft. The retro guidewire reamers include mechanisms to protect the mechanical joint between the actuator wire and the slide actuator which prevent the actuator wire from disengaging from the slide actuator when the cutting member is obstructed by a guidewire.

TECHNICAL FIELD

The present disclosure relates generally to surgical instruments and, more specifically, to surgical instruments for creating tunnels through bone during arthroscopic ligament reconstruction surgery.

BACKGROUND

Desired outcomes for arthroscopic ligament reconstruction surgery are generally achieved by establishing the proper shape and placement of torn tissue. While performing such surgery, a surgeon typically makes a small incision in a patient's skin covering the surgical site (e.g., a bone joint) to allow a surgical instrument to be placed in the bone joint and manipulated through arthroscopic visualization. One such instrument, sometimes known as a retro guidewire reamer, can be configured to operate in both an antegrade drilling mode and a retrograde cutting mode. The reamer is used to create tunnels through the patient's bone which are subsequently filled with a tissue graft, replicating the original damaged tissue.

For a torn anterior cruciate ligament (ACL) reconstruction, for example, one approach to achieving proper placement of the tissue graft includes creating a tunnel from the outside to the inside (i.e., from the “outside in”) of the patient's femur. With this approach, a surgeon places a guidewire through bone along an established path for creation of the bone tunnel. The surgeon then determines the size of a primary bone tunnel as well as the size of a counterbore through the bone appropriate to fit the replacement tendon graft. Once the proper size of the bone tunnel is established, the surgeon places the reamer with an appropriately sized drill bit over the guidewire to create the primary bone tunnel in an antegrade manner. The surgeon then retracts the guidewire and activates a mechanism to open or deploy a cutting member of the retro guidewire reamer within the bone joint. The surgeon then uses the cutting member to create a counterbore through the bone in a retrograde manner. Once the counterbore is drilled, the surgeon activates the mechanism to close the cutting member, allowing the reamer to be withdrawn through the primary bone tunnel created by the drill bit.

In some instances, device failure can occur when the surgeon attempts to deploy the cutting member before the guidewire is fully retracted from the device. A similar error can occur when the surgeon attempts to rotate the cutting member back to its original position while the guidewire is still engaged with the cutting member. These errors can potentially cause damage to the mechanical joint which allows the cutting member to deploy and retract, rendering the device inoperable and requiring a replacement device.

SUMMARY

Described herein are retro guidewire reamers including a drill having a tubular shaft configured to be disposed over a guidewire and at least one cutting member movably disposed adjacent the distal end of the shaft. A slide actuator is moveably coupled to the shaft and to an actuator wire slidable along the shaft. The actuator wire is operative to move the at least one cutting member between a closed position and a deployed position when the slide actuator is moved along the shaft. The retro guidewire reamers of this disclosure advantageously include mechanisms to protect the mechanical joint between the actuator wire and the slide actuator which prevent the actuator wire from disengaging from the slide actuator when the cutting member is obstructed by a guidewire. Because of the mechanisms, the surgeon would see that motion of the slide actuator does not result in deployment of the cutting member and would recognize that the guidewire is obstructing the movement of the cutting member.

Examples of the retro guidewire reamer of this disclosure may include one or more of the following, in any suitable combination.

In examples, the retro guidewire reamer of this disclosure includes a tubular shaft having a distal end and a proximal end and configured to be disposed over a guidewire. At least one cutting member is movably disposed adjacent the distal end of the shaft and a slide actuator moveably coupled to the shaft. An actuator wire is slidable along the shaft. The actuator wire has a first end coupled to the slide actuator and a second end coupled to the at least one cutting member. The actuator wire is operative to move the at least one cutting member between a closed position and a deployed position when the slide actuator is moved along the shaft. One of the actuator wire and the slide actuator includes a plurality of teeth configured to engage a flexible member extending from the other of the actuator wire and the slide actuator. The flexible member is configured to allow for movement of the slide actuator relative to the shaft at a preselected force when the actuator wire is prevented from sliding along the shaft. In examples, the preselected force is between about 1 lbf and about 8 lbf. In further examples, the plurality of teeth are formed integrally with the one of the actuator wire and the slide actuator. In other examples, the plurality of teeth are formed separately and bonded to the one of the actuator wire and the slide actuator.

In other examples, the retro guidewire reamer of this disclosure includes a tubular shaft having a distal end and a proximal end and configured to be disposed over a guidewire. At least one cutting member is movably disposed adjacent the distal end of the shaft and a slide actuator is moveably coupled to the shaft. An actuator wire is slidable along the shaft. The actuator wire has a first end disposed within the slide actuator and a second end coupled to the at least one cutting member. The actuator wire is operative to move the at least one cutting member between a closed position and a deployed position when the slide actuator is moved along the shaft. A spring mechanism including a rod is fixedly disposed within the slide actuator and a shuttle member is configured to move along the rod adjacent at least one compression element. The shuttle member is coupled to the first end of the actuator wire and configured to compress the at least one compression element, allowing for movement of the slide actuator relative to the shaft when the actuator wire is prevented from sliding along the shaft. In examples, the at least one compression element is two compression elements, and the shuttle member is disposed between the two compression elements. In further examples, the at least one compression element is a spring. In other examples, the first end of the actuator wire is rigidly coupled to the shuttle member.

In further examples, the retro guidewire reamer of this disclosure includes a tubular shaft having a cannulation extending from a distal end to a proximal end and configured to be disposed over a guide wire. At least one cutting member is moveably disposed adjacent the distal end of the shaft. A sheath member is axially aligned with the shaft. The sheath member includes a pin having an outer portion projecting radially from the sheath member and an inner portion extending through a transverse hole in the shaft in communication with the cannulation. A slide actuator is moveably coupled to the shaft and operatively coupled to the at least one cutting member for moving the at least one cutting member between a retracted and a deployed position. The slide actuator includes an internal slot configured to receive the outer portion of the pin such that the outer portion of the pin is slideable within the slot, and at least one opening in communication with the slot. The at least one opening is configured to receive the outer portion of the pin. When the outer portion of the pin is not engaged with the at least one opening, the slide actuator is moveable relative to the shaft, and when the outer portion is engaged with the at least one opening, the slide actuator is fixed relative to the shaft. In examples, the at least one opening in the slide actuator is two openings corresponding to the retracted and deployed position of the cutting member, respectively. In other examples, the pin is attached to a spring element of the sheath. The spring element controls a displacement path of the pin. In further examples, the spring element is a beam spring.

In yet further examples, the retro guidewire reamer of this disclosure includes a tubular shaft having a cannulation extending from a proximal end to a distal end, and at least one cutting member moveably disposed adjacent the distal end of the shaft. A slot extends through a surface of the shaft in communication with the cannulation. A diameter of a proximal region and a distal region of the slot is selected to be wider than a diameter of an intermediate region of the slot. A slide actuator is slideably coupled to the shaft and operative to move the at least one cutting member between a retracted and a deployed position. The slide actuator includes a transverse opening in communication with the slot. The reamer also includes a pin having an outer portion and an inner portion terminating in a foot portion. A diameter of the foot portion is selected to be wider than a diameter of the inner portion. The pin is at least partially disposed within the opening of the slide actuator such that the foot portion extends into one of the proximal or distal regions of the slot. The pin is actuable from a first position, in which interference between the foot portion of the pin and the intermediate region of the slot prevents the slide actuator from axial movement along the shaft, to a second position, in which the foot portion of the pin extends into the cannulation of the shaft and the slide actuator is axially moveable along the shaft. In examples, a spring is radially disposed about the inner portion of the pin and configured to bias the outer portion of the pin away from the shaft. In examples, the inner portion of the pin is configured to axially slide along the intermediate portion of the slot. In other examples, the proximal and distal portions of the slot correspond to the retracted and deployed positions of the cutting member, respectively.

In other examples, the retro guidewire reamer of this disclosure includes a tubular shaft having a distal end, a proximal end, and a longitudinal axis extending therebetween. The distal end of the shaft defines a drilling tip. A cutting member is disposed within a cavity formed adjacent the distal end of the shaft. The cutting member has a first end pivotally attached to the shaft at a distal end of the cavity and a second end defining a cutting end. The cutting member is pivotable about an axis of rotation that is perpendicular to the longitudinal axis. An actuator wire extends along a groove in the shaft and is coupled to the first end of the cutting member. A slide actuator is operatively coupled to the actuator wire such that longitudinal movement of the slide actuator along the shaft is effective to pivot the cutting member about the axis of rotation between a retracted position, in which the cutting end does not protrude from the cavity, and a deployed position, in which the cutting end protrudes from the cavity. The deployed position of the cutting end is distal to the retracted position of the cutting end. In examples, the cavity includes holes on opposing sides of the shaft configured for the passage of pivot pins attached to the cutting member. In other examples, a pivot direction of the cutting member between the retracted and deployed positions is away from a user. In further examples, in the deployed position, the first end of the cutting member rests against a distal wall of the cavity such that the distal wall provides resistance to the cutting member during retrograde drilling.

DETAILED DESCRIPTION

In the description that follows, like components have been given the same reference numerals, regardless of whether they are shown in different examples. To illustrate example(s) in a clear and concise manner, the drawings may not necessarily be to scale and certain features may be shown in somewhat schematic form. Features that are described and/or illustrated with respect to one example may be used in the same way or in a similar way in one or more other examples and/or in combination with or instead of the features of the other examples.

As used in the specification and claims, for the purposes of describing and defining the invention, the terms “about” and “substantially” are used to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms “about” and “substantially” are also used herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. “Comprise,” “include,” and/or plural forms of each are open ended and include the listed parts and can include additional parts that are not listed. “And/or” is open-ended and includes one or more of the listed parts and combinations of the listed parts.

For a better understanding of the retro guidewire reamer of this disclosure,FIGS. 1a-2cshow an example of prior art retro guidewire reamer100for securing a tissue to bone.FIG. 1adepicts a side view of the retro guidewire reamer100, as well as a detailed view of a drill bit102having a tubular (cannulated) shaft103disposed over a guidewire114.FIG. 1bdepicts a further side view of the retro guidewire reamer100, as well as a detailed view of the drill bit102and the cutting member108in its fully-opened or deployed position. As shown inFIGS. 1aand 1b, the shaft103extends through a sheath104with the cutting member108being operatively coupled within an opening or cavity106near a distal end of the shaft103. The shaft103is coupled to a mechanism including, for example, a slide actuator172, a lock knob174, a plunger support176, and a depth slide180, for manually opening or deploying the cutting member108, as further described below. The cutting member108can further include at least one through hole (not shown) allowing for the passage of the guidewire114through the cutting member108in its closed and/or open positions. In examples, the guidewire could be a 2.4 mm guidewire, or any other suitable guidewire or guide pin, designed to provide more accurate bone tunnel placement during arthroscopic ligament reconstruction surgery.

FIGS. 2aand 2bdepict various components of the retro guidewire reamer100, including the drill bit102, the shaft103, the sheath104, the slide actuator172, the lock knob174, the plunger support176, and the depth slide180. The depth slide180can be used to determine the desired length of the counterbore formed by the cutting member108.FIGS. 2aand 2bfurther include an actuator wire130connectable between the cutting member108and the slide actuator172. The lock knob174can have a pin136configured to engage a hole178in the shaft103, and to make contact with a guidewire disposed in the shaft103. The shaft103can furthermore have a groove or slot138(FIG. 2b) extending along a surface for slidably accommodating the actuator wire130. A projection140at the proximal end of the actuator wire130is configured to slide into a slot hole145formed in the slide actuator172, forming a mechanical joint. During use, the mechanical joint allows the slide actuator172and the actuator wire130to cooperate to move the cutting member108from a closed position to its opened or deployed position, and vice versa. Further, during use, the lock knob174and the plunger support176cooperate to secure the guidewire within the shaft103. The plunger support176also acts to limit proximal travel of the slide actuator172.

FIGS. 3a-3cdepict the deployment of the retro guidewire reamer100ofFIGS. 1a-2c. As shown inFIG. 3a, the shaft103is configured to be disposed over the guidewire114. As shown inFIG. 3b, once the guidewire114is at least partially retracted within the shaft103, the slide actuator172can be moved along the shaft103toward the distal end of the shaft103in a single manual motion to move the cutting member108to its deployed position. As shown inFIG. 3c, once the cutting member108is in its fully-deployed position, the lock knob174can be rotated to secure, stabilize, and strengthen the guidewire114, the shaft103, and the cutting member108as a unit. To move the cutting member108from its opened or deployed position back to its closed position, the surgeon can move the slide actuator172along the shaft103toward the proximal end of the shaft103, thereby closing the cutting member108. However, attempts by the user to move the slide actuator172while the guidewire114is still engaged with the cutting member108causes the actuator wire130to decouple from the slide actuator172, potentially damaging the mechanical joint between the two.

Having described the above example of a retro guidewire reamer100, it should be noted that the retro guidewire reamers of this disclosure can take the form of any retro guidewire reamer in which a mechanical joint exists between the actuator wire130and the slide actuator172. Non-limiting examples of suitable retro guidewire reamers are further described in U.S. Publication No. 2014/0276844 to Smith & Nephew, Inc. (Memphis, Tenn.), incorporated herein by reference.

Turning now toFIGS. 4aand 4b, an example of the retro guidewire reamer200of this disclosure is shown in a detailed, cross-sectional view. The retro guidewire reamer200is substantially similar to the retro guidewire reamer100shown inFIGS. 1a-3c, except as described below. As stated above, the retro guidewire reamer200provides a mechanism to protect the joint between the actuator wire230and the slide actuator272when the cutting member (not shown) is obstructed by a guidewire by allowing limited movement of the slide actuator272along the drill shaft203before the actuator wire230is forced to decouple from the slide actuator272. Specifically, as shown inFIGS. 4aand 4b, the retro guidewire reamer200includes a drill having a shaft203configured to be disposed over a guidewire, and a slide actuator272moveably coupled to the shaft203. A proximal end of the actuator wire230comprises a plurality of teeth232configured to engage the tip of a flexible member234extending from the slide actuator272toward the teeth232. The plurality of teeth232can be formed integrally with the actuator wire230in one piece, or can be formed separately as a plastic mold and bonded to the metal actuator wire230. The tip of the flexible member234can be straight, as shown inFIG. 4a, or can be angled to allow for easier motion in one direction than another, as shown inFIG. 4b. The flexible member234can comprise a flexible material, such as spring steel or a flexible plastic.

The retro guidewire reamer200is configured to allow for movement of the slide actuator272relative to the shaft203at a preselected force when the actuator wire230is prevented from sliding along the shaft203, e.g., when the cutting member is obstructed by the guidewire. In examples where the normal operation force to actuate the cutting member is less than 1 lbf, the mechanism will allow actuation of the cutting member up to this force threshold. In further examples, the force that decouples the actuator wire230from the slide actuator272is between about 4-8 lbf. The retro guidewire reamer200is therefore designed such that the approximate force to decouple the flexible member234from the teeth232of the actuator wire230is above 1 lbf and below 4-8 lbf, allowing the cutting member to be actuated within its design window. It is contemplated by this disclosure that the mechanism could be combined with a spring (not shown) such that the flexible member234could ratchet and then be forced back into its original position by the spring. In an alternative example, shown inFIG. 4c, the projection240of the actuator wire230could be designed to take the place of the flexible member234, with the teeth232′ molded into the slide actuator272.

Turning now toFIG. 5a, an alternative example of the retro guidewire reamer300of this disclosure is shown in an exploded view. The retro guidewire reamer300is substantially similar to the retro guidewire reamer100shown inFIGS. 1a-3c, except as described below. As shown inFIG. 5a, the retro guidewire reamer300includes drill having a shaft303configured to be disposed over a guidewire. An actuator wire330is slidable along the shaft303, having a projection340disposed within a slide actuator372. The retro guidewire reamer300further includes a spring mechanism including a rod342fixedly disposed within the slide actuator372, and a shuttle member344configured to move along the rod342. Two compressions springs346a,346bare disposed on the rod342on opposite sides of the shuttle member344. The shuttle member344contains a slot350to receive the projection340of the actuator wire330. In examples, proximal motion of the slide actuator372relative to the shaft303is limited by the plunger support376, while distal motion is restricted by a stop surface348aon an internal bore of the slide actuator372and a corresponding stop surface348bon the shaft303. Under normal use conditions (i.e., the cutting member is unobstructed by the guidewire), the spring force of the compression springs346a,346bexceeds the normal operation force needed to deploy the cutting member (e.g., less than 1 lbf). Therefore, the compression springs346a,346bwould not be compressed by the shuttle member344under normal use conditions. However, in the event that the cutting member is obstructed by the guidewire, the force applied by the user to the slide actuator372would cause the shuttle member344to compress one of the compression springs346a,346bprior to generating forces sufficient to compromise the joint strength between the shuttle member344and the actuator wire330.

Specifically, as shown in more detail inFIG. 5b, under normal use conditions (i.e., the cutting member308is not obstructed by the guidewire314), the user moves the slide actuator372distally to deploy the cutting member308to its retrograde position. In this scenario, the compression spring346ais not compressed by the shuttle member344. However, as shown inFIG. 5c, when the cutting member308is obstructed by the guidewire314and the user attempts to move the slide actuator372distally to deploy the cutting member308, the compression spring346ais compressed by the shuttle member344and exerts a counterforce on the shuttle member344, causing the slide actuator372to spring back to its original position. Ideally, the user would see that motion of the slide actuator372does not result in deployment of the cutting member308and would recognize that the guidewire314is obstructing the motion of the cutting member308. Similarly, as shown inFIG. 5d, under normal use conditions, the user moves the slide actuator372proximally to retract the cutting member308to its closed position. In this scenario, the compression spring346bis not compressed by the shuttle member344. However, as shown inFIG. 5e, when the cutting member308is obstructed by the guidewire314and the user attempts to move the slide actuator372proximally to retract the cutting member308, the compression spring346bis compressed by the shuttle member344and exerts a counterforce on the shuttle member344.

It should be noted that, while two compression springs346a,346bare shown inFIGS. 5a-e, a single-spring alternative would suit those applications that only require single-direction protection of the mechanical joint between the slide actuator372and the actuator wire330. It is further contemplated by this disclosure that the compression springs346a,346bcould be substitute with alternative spring types. In other examples, not shown, it is contemplated that the shuttle member344is rigidly fixed to the actuator wire330by means such as over-molding a plastic shuttle member344to the metal actuator wire330. Finally, it is contemplated that the actuator wire330could be coupled to the slide actuator372via a compliant flexure (not shown), thus eliminating the need for the compression springs346.

It should also be noted that, while the mechanisms described above with regard toFIGS. 4a-5erelate to the protection of a mechanical joint between an actuator wire and a slide actuator of a retro guidewire reamer, the mechanisms could also be configured for use in any type of linear motion device that requires a force limiter. Furthermore, the mechanisms described above with regard toFIGS. 4a-5eare designed to protect the mechanical joint between the actuator wire and the slide actuator by allowing for limited movement of the slide actuator relative to the shaft when the cutting member is obstructed by the guidewire. Other mechanisms, described in more detail below, provide protection to the mechanical joint by preventing movement of the slide actuator relative to the shaft when the cutting member is obstructed by the guidewire.

Turning now toFIG. 6a, an alternative example of the retro guidewire reamer400of this disclosure is shown in a detailed, perspective view. The retro guidewire reamer400is substantially similar to the retro guidewire reamer100shown inFIGS. 1a-3c, except as described below. As shown inFIG. 6a, the retro guidewire reamer400includes drill having a shaft403configured to be disposed over a guidewire, a sheath404, a slide actuator472, and a plunger support476. As further shown inFIG. 6a, the slide actuator472comprises a distal hole452aand a proximal hole452b, as described in more detail below. As shown inFIG. 6b, the sheath404has a spring element456, such as a beam spring, that extends proximally toward the plunger support476. A lock pin454is fixed to the spring element456of the sheath404. The sheath404is coaxial with the shaft403and its position is fixed relative to the shaft403.

As shown inFIG. 6c, the lock pin454includes an outer portion454aprojecting radially from the spring element456and an inner portion454bextending through the spring element456and through a transverse hole458in the shaft403in communication with the interior of the shaft403. The distal and proximal holes452a,452bin the slide actuator472align with the transverse hole458in the shaft403when the slide actuator472is positioned in either the retrograde or antegrade position, respectively. While the distal and proximal holes452a,452bare shown inFIG. 6cas circular holes, slots or tapered holes are also contemplated by this disclosure. Furthermore, the holes452a,452bare not limited to through holes, depending on method of manufacture. A diameter of the outer portion454aof the lock pin454is selected to be greater than a diameter of the inner portion454bof the lock pin454. Furthermore, a size of the distal and proximal holes452a,452b, as well as a size of an interior slot460of the slide actuator472, are selected to provide a clearance fit with the outer portion454aof the lock pin454. Under normal use conditions (i.e., when the cutting member is not obstructed by the guidewire), radial clearance between the top surface of the lock pin454and the upper surface of the interior slot460allows the slide actuator472to move freely over the outer portion454aof the lock pin454to deploy and retract the cutting member. However, as shown inFIG. 6d, when the guidewire414is present in the shaft403and the slide actuator472is in the antegrade position, the guidewire414causes the lock pin454to be displaced radially by flexing of the spring element456, the spring element456controlling the displacement path of the lock pin454. When the lock pin454is displaced, the outer portion454aengages with the distal hole452aof the slide actuator472, thus locking the slide actuator472in the antegrade position. Similarly, as shown inFIG. 6e, when the guidewire414is present in the shaft403and the slide actuator472is in the retrograde position, the outer portion454aof the lock pin454engages with the proximal hole452bof the slide actuator472, locking the slide actuator472in the retrograde position. Such impeded movement of the slide actuator472will cause the user to recognize that the guidewire414is obstructing motion of the cutting member and will retract the guidewire414.

In an alternative example, shown inFIG. 6f, the spring element456of the sheath404and the lock pin454could be replaced with a formed spring460. The formed spring460is fixed at one end to the plunger support476and aligned with the transverse hole458in the shaft403to provide for communication with the interior of the shaft403. When a guidewire414is present in the shaft403(FIG. 6g), the spring460would deflect, causing the top bend of the spring460to engage with one of the proximal and distal holes452a,452bin the slide actuator472. Alternatively, the spring element456of the sheath404could be replaced with a separate spring component462fixed to the plunger support476, as shown inFIG. 6h. The spring component462extends distally from the plunger support476such that the attached lock pin454is aligned with the transverse hole458in the shaft403, allowing for communication of the lock pin454with the guidewire414. The guidewire414radially displaces the lock pin454, causing the lock pin454to engage with one of the distal and proximal holes452a,452bin the slide actuator472. In yet another example, the lock pin454could be omitted in lieu of an additional bend or tab464formed at the proximal end of the spring element456of the sheath404, as shown inFIG. 6i. The tab464would engage with a mating slot466a,466bin the slide actuator472. In this example, the slot466in the slide actuator472could be round or could have an oval shape to more closely approximate the geometry of the tab464.

In further examples, not shown, it is contemplated by this disclosure that the spring element456of the sheath404could include alternative spring geometries. For example, the spring element456could be constructed to minimize flexure, with the lock pin454slidingly engaging a hole in the spring element456. The hole in the spring element456would act as a bushing, whereby the lock pin454would float radially until a guidewire414was present in the shaft403, forcing the lock pin454radially outward to engage one of the distal and proximal holes452a,452bin the slide actuator472.

Turning now toFIGS. 7aand 7b, an alternative example of the retro guidewire reamer500of this disclosure is shown in an exploded view (FIG. 7a) and an assembled view (FIG. 7b). The retro guidewire reamer500is substantially similar to the retro guidewire reamer100shown inFIGS. 1a-3c, except as described below. As shown inFIGS. 7aand 7b, the retro guidewire reamer500includes a drill having a shaft503, a slide actuator572, a pushbutton568and a spring570, as further described below. The slide actuator572includes an opening584in communication with an interior of the slide actuator572. A cut-out or slot582extends through a surface of the shaft503in communication with the interior of the shaft503.

As shown in more detail inFIG. 7c, the pushbutton568includes an outer portion568aand an inner portion568bterminating in a foot portion568c. A diameter of the foot portion568cis selected to be wider than a diameter of the inner portion568b. As further shown inFIG. 7d, the slot582in the shaft503has an “I” shape, such that a diameter of a proximal region582aand a distal region582bof the slot582is selected to be wider than a diameter of an intermediate region582cof the slot582. In particular, the diameter of the proximal and distal regions582a,582bof the slot582are selected to accommodate the foot portion568cof the pushbutton568, while the diameter of the intermediate region582cof the slot582is selected to accommodate the inner portion568bof the pushbutton568, while prohibiting travel of the foot portion568calong the slot582, as further described below. The proximal region582aand the distal region582bof the slot582correspond to the retracted and deployed positions of the cutting member, respectively.

Turning now toFIG. 7e, a cross-sectional view of the retro guidewire reamer500is shown. The spring570is disposed within the opening584of the slide actuator572and the pushbutton568is snap-fitted over the spring570while the slide actuator572is aligned with the slot582. Alternatively, the pushbutton568could be incorporated into the slide actuator572in a one-piece design. InFIG. 7e, the slide actuator572is shown in the antegrade position and the pushbutton568is at rest such that the foot portion568cof the pushbutton568is disposed within the proximal region582aof the slot582. The pushbutton568is in a raised position due to the force of the spring570such that the foot portion568cdoes not protrude into the interior of the shaft503. To advance the slide actuator572to the retrograde position, the user holds down the pushbutton568, as illustrated inFIG. 7f. Where no guidewire is present within the shaft503, the pushbutton568allows for movement of the slide actuator572as the foot portion568cof the pushbutton568enters the shaft503and the inner portion568bof the pushbutton568is slidable along the intermediate region582cof the slot582until the pushbutton568is aligned with the distal region582bof the slot582(FIG. 7g). However, when a guidewire514is present within the shaft503(FIG. 7h), the interference between the foot portion568cof the pushbutton568and the guidewire514will prevent the foot portion568cof the pushbutton568from entering the shaft503, thus preventing movement of the slide actuator572.

As stated above, the mechanisms described with regard toFIGS. 4a-7hrelate to the protection of a mechanical joint between an actuator wire and a slide actuator of a retro guidewire reamer when the cutting member is obstructed by the guidewire. In the retro guide wire reamers described above, the guidewire is necessary to support the cutting member in place during retrograde drilling, since deploying the cutting member requires flipping the cutting member towards the user, leaving the cutting member unsupported by the surrounding structures. Other mechanisms, described in more detail below, provide protection to the mechanical joint by allowing the cutting member to deploy away from the user such that the cutting member is supported by the surrounding regions of the shaft. In such examples, a guidewire would not required for use of the device.

Turning now toFIG. 8a, an alternative example of the retro guidewire reamer600of this disclosure is shown in a detailed, perspective view. The retro guidewire reamer600is substantially similar to the retro guidewire reamer100shown inFIGS. 1a-3c, except as described below. As shown inFIG. 8a, the retro guidewire reamer600includes a drill having a shaft603, the distal end of the shaft603defining a drilling bit602. The cutting member608is disposed within a cavity606formed adjacent the distal end of the shaft603. The cavity606comprises holes610for pins612on opposite sides of the shaft603to keep the cutting member608in place. In its closed position, the cutting member608has a first end608apivotally attached to the shaft603at a distal end of the cavity606and a second end608bdefining a cutting end disposed within a proximal end of the cavity606. The cutting member608is pivotable about an axis of rotation that is perpendicular to a longitudinal axis A of the shaft603.

As shown inFIG. 8b, the actuator wire630extends along a slot638in the shaft603with a distal end630bof the actuator wire630being operatively coupled to the first end608aof the cutting member608. A slide actuator (not shown) is operatively coupled to the proximal end of the actuator wire630such that longitudinal movement of the slide actuator along the shaft603is effective to pivot the cutting member about the axis of rotation between a retracted position, in which the second end608bdoes not protrude from the cavity606(FIG. 8a), and a deployed position, in which the second end608bprotrudes from the cavity606(FIG. 8c). As such, the cutting member608flips in a deployment direction away from the user such that the deployed position of the second end608bof the cutting member608is distal to the retracted position of the second end608b. Once deployed, the first end608aof the cutting member608rests against a distal wall607of the cavity606, providing sufficient resistance to the cutting member608so that the cutting member608can be used to form the counterbore without a guidewire in place.