Reamer for augmented glenoid implant

A reaming device for preparing a glenoid of a patient may include a base configured for mounting to bone and an oscillatory rasp configured to be translatable in a proximal-distal direction relative to the base while the base is coupled to the glenoid of the patient.

BACKGROUND

Eccentric glenoid erosion occurs in as much as 40% of shoulder arthroplasty candidates. Wear can present anteriorly, superiorly, and posteriorly, with superior being most common in reverse shoulder arthroplasty (“RSA”) candidates, and posterior being most prevalent in total shoulder arthroplasty (“TSA”) candidates. As the articular surface of the glenoid wears or degrades over time, the glenoid surface may take a biconcave shape. The worn or degraded portion of the glenoid may be referred to as the neoglenoid and the original portion of the glenoid may be referred to as the paleoglenoid.

Any glenoid implant that does not have a biconvex design to match the concave surface of a glenoid with eccentric glenoid erosion may require removal of a relatively large amount of bone stock, including portions of the paleoglenoid, which may be undesirable. As eccentric glenoid erosion progresses, the relative sizes and shapes of the paleoglenoid and the neoglenoid may also change. Therefore, to minimize removal of bone stock, a range of biconvex designs corresponding to various stages of erosion may be used. One exemplary biconvex design is illustrated inFIGS.1A and1B. The implant1ofFIGS.1A and1Bincludes a biconvex bone-facing surface3and an opposing concave surface5. The concave surface5serves as a replacement for the natural glenoid cavity after the implant1is placed on the bone. The bone-facing surface3includes a first convex portion3aconfigured to mate to the prepared paleoglenoid, and a second convex portion3bconfigured to mate to the prepared neoglenoid. The second convex portion3bis angled relative to the first convex portion3bto match the anticipated angle between the prepared paleoglenoid and neoglenoid surfaces. As shown inFIG.1C, the implant1may be provided in multiple variations corresponding to different degrees along a typical eccentric erosion pattern for a natural glenoid cavity. The second convex portion3bis larger compared to the first convex portion3ain implants1corresponding to progressively greater degrees of erosion. Three implants1corresponding to three different degrees of erosion are shown inFIG.1C, but more or fewer implants may be provided in various examples. Preparation of a glenoid for such biconvex implants may be facilitated by a tool able to accommodate both the stage of erosion and the selected implant.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure relates to a device that may be used for preparing a glenoid cavity exhibiting eccentric erosion for a biconvex glenoid implant. The device may include a base and a rasp being adjustable relative to one another. Specifically, the base and the rasp may be adjustable relative to one another along a proximal-distal axis such that a distance that the rasp extends distally beyond the base may be varied. The rasp may be configured to oscillate about a pivot axis, and the adjustment of the base and rasp relative to one another may include movement or translation of the features defining the pivot axis relative to the base, or movement or translation of the base relative to the features defining the pivot axis. The base and rasp may be adjusted relative to one another before fixing the base to the paleoglenoid. The base and rasp may be adjusted again after the rasp has removed some of the neoglenoid, such as by moving the rasp distally further beyond the base to reengage the new surface of the neoglenoid.

The device may include an assembly for converting rotational input into oscillating output. The assembly may include a shaft arranged to be driven rotationally about the shaft's centerline. The shaft may include a hammer offset from the shaft's centerline. An anvil may include a pair of prongs extending along opposite sides of the hammer, and the anvil may be arranged and constrained such that rotation of the shaft causes the hammer to strike the prongs in alternation, which may in turn cause the anvil to pivot back and forth in an oscillating pattern relative to the pivot axis. The pivot axis may be defined by a pivot pin suspending the anvil relative to the device. Alternatively, the pivot axis may be defined by a guidewire or post disposed through the rasp and extending into the patient's glenoid. Because the rasp may be connected to the anvil, the oscillation of the anvil may cause the rasp to oscillate along with the anvil. The oscillation of the rasp may smooth the neoglenoid in preparation for a glenoid implant.

In another aspect, a method of preparing a glenoid of a patient for receiving a biconvex glenoid implant may include fastening a base of a reaming device to a paleoglenoid portion of the glenoid, and translating a rasp of the reaming device in a proximal-distal direction relative to the base while the base is fastened to the paleoglenoid portion of the glenoid. The method may further include driving the rasp to ream a neoglenoid portion of the glenoid.

In some arrangements, translating the rasp may include translating the rasp between a first pre-set position and a second pre-set position.

In some arrangements, the first pre-set position may correspond to a first size biconvex glenoid implant, and the second pre-set position corresponds to a second size biconvex glenoid implant, the second size being different than the first size.

In some arrangements, driving the rasp may include driving the rasp to move repeatedly relative to a pivot axis.

In some arrangements, the reaming device may include an assembly for transferring rotational input on a shaft into oscillating motion of the rasp about a pivot axis.

In some arrangements, the assembly may include a hammer offset from a central axis of the shaft and an anvil connected to the rasp, the anvil including a pair of prongs extending adjacent to the hammer.

In another aspect, a reaming device for preparing a glenoid of a patient may include a base configured for mounting to bone and an oscillatory rasp configured to be translatable in a proximal-distal direction relative to the base while the base is coupled to the glenoid of the patient.

In some arrangements, the device may include a shaft drivable to rotate about its centerline and including a hammer offset from the centerline, and an anvil to which the rasp is mounted. The anvil may be rotatable about a pivot axis and including two prongs extending along the hammer.

In some arrangements, the prongs may extend along opposite sides of the hammer.

In some arrangements, the centerline of the shaft may extend parallel to the proximal-distal direction.

In some arrangements, the anvil may be adjustable along the proximal-distal direction relative to the base.

In some arrangements, the rasp may be adjustable along the proximal-distal direction between a plurality of discrete lockable positions.

In some arrangements, the discrete lockable positions may be defined by a peg and hole interface including a plurality of holes in the device. The holes may be mutually spaced apart relative to one another along the proximal-distal direction.

In some arrangements, the rasp may be pivotably connected to the peg of the peg and hole interface.

In some arrangements, the discrete lockable positions may correspond to appropriate reaming depths of a preselected plurality of glenoid implants having biconvex surfaces mimicking differing degrees of eccentric glenoid erosion.

In some arrangements, the rasp may extend at an angle relative to a surface of the base configured to mate to a paleoglenoid corresponding to an angle at which a portion of a glenoid implant configured to mate to a prepared neoglenoid extends relative to a portion of the glenoid implant configured to mate to a prepared paleoglenoid.

In some arrangements, the angle at which the rasp extends relative to the surface of the base configured to mate to the paleoglenoid may be between 20° and 40°.

In some arrangements, the angle at which the rasp extends relative to the surface of the base configured to mate to the paleoglenoid may be 30°.

In another aspect, a reaming device for preparing a glenoid of a patient may include a shaft drivable to rotate about its centerline and including a hammer offset from the centerline. The device may further include an anvil including two prongs extending along the hammer. The anvil may be rotatable about a pivot axis. A rasp may be connected to the anvil so that rotating the shaft causes oscillation of the rasp, the rasp including a raised portion and a recessed portion both including teeth. The teeth included in the raised portion may have a greater height relative to a base of the rasp than the teeth included in the recessed portion. The rasp may be configured to be translated in a proximal-distal direction parallel to the centerline of the shaft while the reaming device is coupled to the glenoid of the patient.

In another aspect, a bone reaming device may include a base fastenable to bone and extending generally parallel to a proximal-distal axis and a rasp rotatably drivable about a rasp axis. The rasp axis may be translatable relative to the base and the rasp receives driving input from a drive shaft through at least one ball joint.

DETAILED DESCRIPTION

When referring to specific directions and planes in the following disclosure, it should be understood that, as used herein, the term “proximal” means closer to the operator/surgeon, and the term “distal” means further away from the operator/surgeon. The term “anterior” means toward the front of the body or the face, and the term “posterior” means toward the back of the body. With respect to the longitudinal axis of the spine, the term “superior” refers to the direction towards the head, and the term “inferior” refers to the direction towards the pelvis and feet. The “transverse plane” is that plane which is orthogonal to the longitudinal axis of the spine. The “coronal plane” is a plane that runs from side to side of the body along the longitudinal axis of the spine and divides the body into anterior and posterior portions. The “sagittal plane” is a plan that runs along the longitudinal axis of the spine and defines a plane of symmetry that separates the left and right sides of the body from each other. Finally, “medial” refers to a position or orientation toward the sagittal plane, and lateral refers at a position or orientation relatively further from the sagittal plane.

A bone preparation device10is shown inFIG.2. The device10includes a shaft14extending along an axis of rotation X, which is also the shaft's centerline in the illustrated example. In the illustrated arrangement, the axis of rotation X is aligned with a proximal-distal axis of the device10. However, in other arrangements, the axis of rotation may be transverse to or offset from the proximal-distal axis of the device10. A drive head16provides a proximal end of the shaft14. The drive head16shown inFIG.2has a hexagonal axial cross-section, but other shapes of drive head16are contemplated.

The shaft14extends through a grip18and a tube22extending distally beyond the grip18. A rasp26and base30extend distally beyond a distal end of the tube22. The rasp26may be configured to ream or otherwise prepare bone on the neoglenoid portion of a native glenoid with eccentric glenoid erosion. In the illustrated example, and as may be better appreciated by the close view provided byFIG.2B, the rasp26extends at an angle relative to the base30that corresponds to the angle at which the second convex surface3bof a selected implant extends relative to the first convex surface3a.The base30shown inFIGS.2A and2Bincludes a hole31, such as for encircling a bone screw for fixing the base to the paleoglenoid portion of a native glenoid with eccentric glenoid erosion. The tube22may include two windows34on opposite sides of the tube22(only one window34being visible in the view presented inFIG.2).

The grip18and tube22are not shown inFIG.3. As shown inFIG.3, the shaft14includes a cap17afor sitting atop the grip18, thereby restraining movement along the proximal-distal axis X of the shaft14relative to the grip18. Two bearings17bencircle the shaft14to maintain alignment of the shaft14within the grip18and the tube22while allowing the shaft14to rotate. A hammer38extends from a distal end of the shaft14. The hammer38extends along an axis that is offset from the axis of rotation X of shaft14.

An anvil42is disposed distally of the shaft14and supported on a generally cylindrical pivot pin44. The pivot pin44may extend through a generally cylindrical channel within the anvil42, tube22, and/or a connecting apparatus connected to the anvil42or tube22, such that the anvil42is pivotable relative to the tube22. The anvil42includes two prongs43extending proximally on opposite sides of the hammer38in a horseshoe or general “U”-shape. When the shaft14rotates about axis X, the hammer38also rotates about axis X. However, due to the offset between the axis of hammer38and axis X, the hammer38follows a relatively large arcuate pathway during rotation, alternately striking the two prongs43as the hammer38traverses the path of rotation. In some alternative arrangements, the anvil42may have only one prong43, resulting in a relatively low oscillation speed.

In the illustrated arrangement, when the shaft14rotates, the hammer38moves along a path of travel. The anvil42is constrained relative to the shaft14such that neither prong43can travel closer to the axis of rotation X than the hammer's38path of travel. Instead, the prongs43may only move so far toward the axis of rotation X such that an inner edge of a prong43, relative to the axis of rotation X, may be contacted by an outer edge of the hammer38while the shaft14rotates. When the hammer38strikes the inner edge of a prong38, the prong38is driven away from the axis of rotation X, causing the anvil44to pivot about the pivot axis. The pivoting of the anvil44brings the opposite prong43into the hammer's38striking range. Thus, the hammer38strikes the prongs43in alternation.

In some arrangements, a stem38athat connects the hammer38to the shaft14enables the hammer38to rotate relative to the stem38a.The rotatable connection between the hammer38and the stem38aenables the hammer38to roll across the prongs43as it strikes them.

The alternating striking of the prongs43causes the anvil44to pivot back and forth about a pivot axis defined along the pivot pin44in an oscillating pattern45. The pivoting of the anvil42transfers to oscillation of the rasp26, which is connected to the anvil42. The arrangement of the hammer38and anvil44thereby converts rotational input on the drive head16of the shaft14to oscillation of the rasp26. In the illustrated arrangement, the oscillating pattern45includes the prongs43alternatingly passing through a respective one of the windows34.

The rasp26and base30are moveable proximally and distally relative to one another. In some arrangements, the base30is moveably coupled to the tube22. In some such arrangements, the base30has an interference fit within a part of the tube22such that the base30may slide relative to the tube22while generally being held frictionally in place. In further such arrangements, such as shown inFIGS.4A and4B, the tube22has a series of detents or holes22afor selectively engaging the base30at various positions. In the arrangement shown inFIG.4A, the base30includes a peg30athat may engage any of the holes22ato fix the base30at one of multiple discrete positions relative to the tube22. The portion of the tube22containing the holes22aor portion of the base30to which the peg30ais attached may be elastically deformable so that the peg30amay be selectively engageable with any of the holes22a.In the arrangement shown inFIG.4B, the base30includes an opening30band a fastener32extends through the opening30band one of the holes22ato fix the base30at one of multiple discrete positions relative to the tube22. In various other arrangements, the base30includes a series of detents or holes similar to the holes22ashown inFIGS.4A and4B, and either the tube22includes a peg or the device10is provided with a fastener for engaging the tube22to the base30.

In other arrangements, axial motion of the rasp26relative to the base30may be accomplished by movement of the anvil42relative to the tube22. In various embodiments, the tube22includes multiple possible points of fixation for the pivot pin44, or the pivot pin44is connected to the tube22by other suitable adjustable features.

Turning toFIG.5, the device10is shown positioned on a native glenoid48such that the base30is fastened to a paleoglenoid52, while the rasp26is disposed against a neoglenoid56. The rasp26extends distally beyond the base30to reach the neoglenoid56, enabling the raps26to prepare the neoglenoid56largely without affecting the paleoglenoid52.

A method of using the device10includes fastening the base to the paleoglenoid52. The base30may be fastened to the paleoglenoid52before or after the paleoglenoid52is smoothed, reamed, and/or otherwise prepared for a glenoid implant, such as an augmented biconvex glenoid implant similar to the implant illustrated inFIGS.1A-B. The paleoglenoid may be smoothed or prepared with any known suitable reaming method. The rasp26is adjusted relative to the base30before, after, or both before and after the base30is fastened to the paleoglenoid52such that the rasp26is disposed against the neoglenoid56. It should be understood that augmented glenoid implants may be provided in different sizes that may generally correspond to different levels of eccentric glenoid erosion. For example, a native glenoid with a relatively small amount of eccentric glenoid erosion may be treated with an augmented glenoid implant with a relatively small neoglenoid portion, while a native glenoid with a relatively large amount of eccentric glenoid erosion may be treated with an augmented glenoid implant with a relatively large neoglenoid portion. The plunge depth of the rasp26relative to the base30(i.e. the distance which the rasp26extends distally beyond the base30) may be set to generally correspond to the size of the augmented glenoid implant and the level of eccentric glenoid erosion. For example, if the augmented glenoid is provided in three sizes that correspond to three levels of eccentric glenoid erosion, the rasp26may have three pre-set plunge depths relative the base30, each plunge depth corresponding to an available size of the augmented glenoid implant. Still further, it should be understood that the different levels of reaming of the neoglenoid (resulting from the particular plunge depth of the rasp26) may generally follow the progression of eccentric glenoid erosion. In other words, as eccentric glenoid erosion progresses and/or worsens, the depth of the neoglenoid increases, while the transition line between the paleoglenoid and the neoglenoid also shifts. The different plunge depths of the rasp26result in reaming that generally follows the anatomic progression of eccentric glenoid erosion, allowing a relatively small amount of bone stock to be removed during preparation of the glenoid to receive an augmented glenoid implant.

With the rasp26positioned at the desired plunge depth relative to the base30, the shaft14is driven to rotate about the axis of rotation X, thereby causing the rasp26to oscillate. The oscillation of the rasp26grinds or cuts away portions of the neoglenoid56to leave a smoother surface and to prepare the neoglenoid56for reception of the augmented glenoid implant. If necessary, the rasp26may be adjusted after some initial reaming of the neoglenoid56to re-engage the rasp26with the neoglenoid56to facilitate further grinding or cutting of the neoglenoid56. This change in plunge depth may be performed without needing to disengage the base30from the paleoglenoid52. Positioning and grinding steps may be alternated as necessary until the neoglenoid56is prepared for implantation of the glenoid implant.

The particular geometry of the rasp26illustrated inFIGS.2A-5is merely exemplary. The rasp26may be replaced between each procedure, and rasps26used with the device may have varying sizes and angles as appropriate for the patient. For example, a rasp26may be selected based on the respective geometry of the patient's paleoglenoid52and neoglenoid56, or the rasp26may be selected based on the biconvex profile of a chosen glenoid implant. In various exemplary arrangements, the rasp26extends at a 30° angle relative to the axis of rotation X, or at an angle between about 20° and about 40° relative to the axis of rotation X, or at an angle that is adjustable, for example by adjustment of a connection between the rasp26and the anvil42. However, in the illustrated embodiment, the angle is fixed and the axial adjustment of the rasp26is sufficient to provide the desired level of glenoid preparation based on the level of eccentric glenoid erosion in the patient.

A bone preparation device110according to a second arrangement as shown inFIG.6similarly includes a tube122, rasp126, and base130. The base130further includes an arm132extending proximally from the base130to connect to the tube122through features not shown. The arm132includes an offset portion132athat provides clearance so that the rasp126can oscillate. Like the base30of the device10ofFIGS.2-5, the base130of the device110illustrated inFIG.6is moveable proximally or distally relative to the rasp126. However, the base130is connected to the tube122and rasp126by features located proximally from the rasp126and distal end of the tube122.

A bone preparation device210according to a third arrangement as shown inFIG.7includes a tube222, base230, and arm232with an offset portion232asimilar to those of the device110shown inFIG.6. In contrast to the devices10,110shown inFIGS.2-5, the device210of the arrangement shown inFIG.7includes a rotary rasp226. The device210lacks the hammer38and anvil42of device10. Instead, rotational input to the device210, such as on features similar to the shaft14and drive head16, is used to drive the rasp226to rotate. The offset portion232baccommodates the rotation of the rasp226.

A bone preparation device310according to another embodiment is shown inFIG.8. The device310includes a carriage318that holds parallel, or generally parallel, a drive shaft314and a base shaft332. The base shaft332includes an anchor331, which includes a spike and screw thread in the illustrated arrangement, at its distal end. The base shaft332further includes a cap330that limits the distance the base shaft can be driven into a paleoglenoid352. After insertion into the paleoglenoid352, the base shaft332is inserted into a threaded sleeve333that is engaged with a threaded bore364within the carriage318. A knob334, located at a proximal end of the threaded sleeve333in the illustrated arrangement, facilitates rotation of the threaded sleeve333relative to the carriage318. Rotation of the threaded sleeve333within the threaded bore364pushes down against the base shaft332and causes the carriage318, the drive shaft314, and a reamer326to translate relative to the base shaft332and paleoglenoid352. A ball joint342joins the reamer326to the drive shaft314. The ball joint342is configured to allow the reamer326to be rotatable with two degrees of freedom relative to the ball joint342, but transmits rotation from the drive shaft314to the reamer326such that rotational input from a motor or power tool360engaged with a drive head316at a proximal end of the drive shaft314causes the reamer326to rotate.

A bone preparation device410according to another embodiment is shown inFIG.9. The device410includes reamer426that is rotationally drivable through a proximal ball joint442aand distal ball joint442b.The proximal ball joint442aconnects a drive shaft414to an intermediate shaft415, and the distal ball joint442bconnects the intermediate shaft442bto the reamer426. Together, the first ball joint442aand second ball joint442boperate to provide the reamer426with six degrees of freedom relative to an anchor431for securing the device410to the paleoglenoid52. The device410further includes a drive head416, carriage418, cap430, base shaft (not illustrated), sleeve433, knob434, and threaded bore464, which are generally similar to the drive head316, carriage318, cap330, base shaft332, sleeve333, knob334, and threaded bore364ofFIG.8, and are thus not described in greater detail herein.

A rasp526according to another arrangement is shown inFIGS.10A and10B. As shown inFIG.10B, the rasp526includes a raised portion566and a recessed portion567. Both portions include several teeth564, but the teeth564of the raised portion566extend farther from a base570of the rasp526than the teeth566of the recessed portion567. The differing heights of the raised portion566and the recessed portion567enable the rasp526to prepare the neoglenoid and paleoglenoid simultaneously while oscillating. Specifically, the raised portion566can prepare the neoglenoid while the recessed portion567prepares the paleoglenoid. Rasps526according to the arrangement ofFIGS.10A and10Bmay be constructed to correspond to the dimensions of various glenoid implant, such that a height difference between the raised portion566and recessed portion567of a given rasp526corresponds to the biconvex profile of a particular glenoid implant.

The rasp526includes a central channel568in its base570for accommodating a generally cylindrical post or guidewire inserted into the glenoid about which the rasp566may oscillate. A similar hammer and anvil assembly may be used for converting rotation to oscillation as that shown inFIG.3, with the rasp526connected to an anvil, except that the anvil would include no pivot pin, thereby permitting the rasp526to oscillate about the guidewire or post disposed through the channel568.

A bone preparation device610according to another arrangement is illustrated inFIG.11. A tube622of the bone preparation device610is adjustably positionable relative to a housing672that ends distally in a base630. The housing672encloses the tube622, but is shown in cross-section inFIG.11to expose the tube622for illustrative purposes. The tube622is connected to the housing672by a nut674threadingly engaged to an exterior of the tube622and including an annular groove that holds support pins676of the housing672to suspend the nut rotatably at a fixed axial position relative to the housing672. An anvil and rasp assembly (not illustrated) similar to that shown inFIG.3extends beyond a distal end of the tube622. A pivot pin644of the anvil and rasp assembly, generally similar to the pivot pin44for the anvil42and rasp26of the arrangement shown inFIGS.2A-5, protrudes from the tube622to an axial slot678in the housing672(shown in dashed lines, as the slot672is defined in a portion of the housing672rendered transparent for the cross-sectional view ofFIG.11). The extension of the pivot pin644through the slot678prevents the anvil and rasp assembly, and by extension the tube622, from rotating about a proximal-distal axis relative to the housing672when the nut674is turned. Thus, turning the nut674causes the threads of the tube622to advance within the nut674, and moves the tube622axially relative to the housing672and base630. A position of the anvil and rasp assembly and tube622within the housing672is observable by the position of a pivot pin644within the slot678. In the illustrated arrangement, indicia646are provided on the housing672next to the slot678to assist determination of the position of the anvil and rasp assembly and tube622relative to the housing672.