Patent Description:
Arthroplasty is the standard of care for the treatment of shoulder joint arthritis. A typical humeral head replacement which attempts to mimic anatomic conditions involves a metallic humeral stem and a modular head replacement, capable of multiple positions for optimal bony coverage. Such humeral head replacement might articulate with the native bone or an opposing glenoid resurfacing device, which may be manufactured from UHMWPE or any other acceptable material. Such humeral stem is usually offered in one or several inclination angles ranging from <NUM> degrees to <NUM> degrees.

For more severe cases of shoulder arthritis, the standard treatment is a reverse reconstruction, which includes reversing the kinematics of the shoulder joint. This is performed by securing a semi-spherical device to the glenoid, referred to as a glenoid sphere, and implanting a humeral stem with a modular cavity capable of receiving the glenoid sphere. The humeral stem is usually offered in one fixed inclination angle between <NUM> degrees and <NUM> degrees, with <NUM> degrees being the angle currently preferred by a majority of surgeons.

As patient disease may progress after anatomic treatment, revision surgery may be necessary to perform a reverse reconstruction of the shoulder. Removal of anatomic devices that have integrated into the patient's bony anatomy may prove to be difficult for the surgeon, and could potentially cause excessive patient bone loss.

The subject matter of the invention is a system for a modular reverse shoulder prosthesis, as defined in claim <NUM>. Embodiments of the present invention include a convertible prosthesis that is capable of conversion from a humeral head replacement to a reverse reconstruction without any removal of parts integrated into the patient's bony anatomy (e.g. implant stems). A desired overall implant inclination angle may be achieved by matching various implant stems with various reverse inserts, thus permitting a resection surface to be matched with an implant stem selection while also permitting a desired overall implant inclination angle to be achieved through the selection of an appropriate insert.

Additional features of the invention are recited in the other claims.

In the drawings, <FIG>, <FIG>, <FIG> and <FIG> illustrate the present invention, whereas the remaining FIGS. illustrate tools and other implants, not forming part of the invention.

While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, falling within the scope of the invention as defined by the appended claims.

<FIG> illustrates an exploded perspective view of an assembly <NUM> of a tray <NUM> and an insert <NUM>, according to embodiments of the present invention. The assembly <NUM> forms part of a reverse shoulder prosthesis. In implanting such a reverse shoulder prosthesis, a humeral head is resected and a stem is implanted into the resected end of the humerus. The tray <NUM> is coupled with the stem, and the insert <NUM> is coupled with the tray <NUM>. Because various types of inserts <NUM> may be used with tray <NUM>, for example inserts with different shapes, sizes, and/or inclination angles, the insert <NUM> couples with the tray <NUM> in a snap-fit configuration once the desired insert <NUM> has been selected. The insert <NUM> may include an articular surface <NUM>, for example a concave articular surface <NUM> that is configured to receive and abut a convex prosthetic head component or other head component for articulation therewith.

<FIG> illustrates a bottom perspective view of insert <NUM>, according to embodiments of the present invention. <FIG> illustrates a top perspective view of a tray <NUM>, according to embodiments of the present invention. <FIG> illustrates a cross-sectional view of the tray <NUM> and insert <NUM> before the insert <NUM> has been affixed to the tray <NUM>, according to embodiments of the present invention. The insert <NUM> includes a snap-fit ring <NUM> seated within a channel <NUM>. Ring <NUM> may be included with the insert <NUM> and seated in channel <NUM> when the insert <NUM> is packaged and/or shipped, as part of a kit for example. The ring <NUM> may have an irregular cross-sectional shape, for example the ring <NUM> may include a chamfered edge <NUM> which is configured to interact with a chamfered edge <NUM> of the tray <NUM> when the insert <NUM> is inserted into the tray <NUM>. The outer diameter <NUM> of the channel <NUM> may be smaller than the inner diameter <NUM> of the ring <NUM>, thereby permitting the ring <NUM> to become compressed within the channel <NUM> as the ring <NUM> passes edge <NUM> and edge <NUM> when insert <NUM> is inserted into tray <NUM>. The ring <NUM> may also include a discontinuity <NUM> (see <FIG>), which assists the ring <NUM> in compressing and becoming recessed within the channel <NUM>. Alternatively, the ring <NUM> may be a continuous ring rather than a C-shaped ring. The inner diameter of <NUM> of the recess <NUM> being smaller than the inner diameter <NUM> of the snap-fit ring <NUM> also helps to keep the ring <NUM> centered with respect to the tray <NUM> and the insert <NUM>. The channel <NUM> may be deep enough to fully accommodate the ring <NUM> when the ring is compressed.

The tray <NUM> includes a channel <NUM> configured to receive the ring <NUM>. At a proximal edge of the channel <NUM>, a retaining ridge <NUM> extends inwardly. Due to the cross-sectional shape of ring <NUM>, and the protrusion of retaining edge <NUM>, when the insert <NUM> is inserted into the tray <NUM>, the ring <NUM> compresses to clear retaining edge <NUM> but then expands back to its original diameter and/or shape within channel <NUM>, which deters dislodgement of the insert <NUM> from the tray <NUM>. The retaining edge <NUM> and/or channel <NUM> may be circular and may extend around an entire periphery of the insert <NUM>, according to embodiments of the present invention. <FIG> shows the insert <NUM> and tray <NUM> in the locked position. In the locked position, the insert <NUM> remains snugly engaged with the tray <NUM> during movement and use of the implant by the patient. This locking, which may also be referred to as a snap-fit, of the insert <NUM> with the tray <NUM> may be reversible. For example, apertures <NUM> (see <FIG>) are included in order to permit a tool to be inserted through the tray <NUM> from outside the tray <NUM> to compress the ring thereby loosening the insert <NUM> and pushing the insert <NUM> out of the tray <NUM>.

The snap-fit engagement of the insert <NUM> with the tray <NUM> maintains the insert <NUM> within the tray <NUM> after implantation. The tray <NUM> may also include fins <NUM> formed on an inner diameter of the tray <NUM>. A sidewall portion <NUM> of the insert <NUM> may be cylindrical in shape, and may have an outer diameter <NUM> that is slightly larger than an inner diameter formed by the tips of fins <NUM>. As such, when insert <NUM> is inserted into tray <NUM>, the fins <NUM> interfere with the sidewall <NUM> in order to prevent rotation of the insert <NUM> with respect to the tray <NUM>. In some embodiments, the fins <NUM> are of a stiffer or harder material than sidewall <NUM> and cut into the sidewall <NUM> in order to inhibit rotation. In other embodiments, the fins <NUM> and/or the sidewall <NUM> deform in order to increase friction and/or gripping to inhibit rotation. The cross-sectional views of <FIG>, and <FIG> are taken along a diameter that passes directly through the fins <NUM>, and the overlap and/or interference between the fins <NUM> and the sidewall <NUM> is shown in <FIG>. The cross-sectional view of <FIG> is taken along a diameter that does not pass through the fins <NUM>.

Due to the configuration of the snap-fit ring <NUM> locking mechanism and fin <NUM> locking mechanism, the insert <NUM> may be locked to the tray <NUM> at any rotational angle of the insert <NUM> with respect to the tray <NUM>. This performance may be referred to as "infinitely dialable," in other words, the insert <NUM> may be "dialed" or rotated to any desired rotational angle about the tray <NUM> and then locked to the tray <NUM>.

The tray <NUM> may be made of metal, for example titanium. The insert <NUM> may be made of polymer, for example, polyethylene. The snap-fit ring may be made of an elastic material, for example titanium, titanium alloy, metal alloy, PEEK, and the like.

According to some embodiments of the present invention, a gap <NUM> is formed between an underside <NUM> of the insert <NUM> and a top surface <NUM> of the tray <NUM> when the insert <NUM> is fully seated in the tray <NUM>. In other words, the bottom surface <NUM> of the insert <NUM> is always in contact with the bottom surface <NUM> of the tray <NUM>, according to embodiments of the present invention. A recess <NUM>, for example a circular recess <NUM>, may be formed in the bottom surface <NUM>, in order to accommodate a small lug due to material left on the insert <NUM> due to the machining process, according to embodiments of the present invention.

<FIG> illustrate an alternative tray <NUM>', according to embodiments of the present invention. Tray <NUM>' includes teeth <NUM>' formed on a bottom surface of the tray <NUM>', which interact with a bottom surface <NUM> of insert <NUM> to inhibit rotation of the insert <NUM> when insert <NUM> is inserted into snap-fit engagement with tray <NUM>'. According to some embodiments of the present invention, a tray may include both teeth <NUM> around an inside sidewall periphery and teeth <NUM>' protruding from a bottom surface of the tray.

According to some embodiments of the present invention, the insert <NUM> and snap-fit ring <NUM> are delivered pre-assembled. The snap-fit ring <NUM> may include an asymmetrical cross-sectional shape such that the ring <NUM> includes a chamfer <NUM> that cooperates with the chamfer <NUM> of the tray. The chamfer <NUM> or <NUM> angle may be forty-five degrees, for example. In some cases, the chamfer <NUM> or <NUM> angle may be forty to fifty degrees; in other cases, the angle may be thirty to sixty degrees, and in yet other cases this angle may be twenty to seventy degrees.

According to embodiments of the present invention, during at least one point in the assembly of the insert <NUM> to the tray <NUM>, the ring <NUM> is fully recessed into the insert <NUM>. According to some embodiments of the present invention, the retaining edge <NUM> is more than <NUM> and less than <NUM> millimeters thick. The inner diameter <NUM> of the channel <NUM> may be smaller than the inner diameter <NUM> of the ring <NUM>, according to embodiments of the present invention. The teeth <NUM> may be cut into a peripheral internal diameter of the tray <NUM>, and the outer diameter of the cylindrical sidewall <NUM> of the insert <NUM> is between <NUM> and <NUM> millimeters smaller than the inner diameter of the cylindrical portion <NUM> of the tray <NUM> with which the sidewall <NUM> interfaces when the insert <NUM> is locked into the tray <NUM>. The inner diameter of the tips of teeth <NUM> may be <NUM> to <NUM> millimeters smaller than the outer diameter of the cylindrical sidewall <NUM> of the insert <NUM>, according to embodiments of the present invention. The tray <NUM> may include a number of teeth spaced radially at equidistant angles, for example six teeth <NUM> spaced sixty degrees apart. According to embodiments of the present invention, the teeth <NUM> are <NUM> millimeters high. The residual gap <NUM> between surfaces <NUM> and <NUM> when the insert <NUM> is fully engaged with the tray <NUM> is no more than <NUM> millimeters, according to embodiments of the present invention. The recess <NUM> formed in the bottom <NUM> of the tray <NUM> may be <NUM> to <NUM> millimeters deep and may extend outwardly from a central axis to a diameter of less than six millimeters, according to embodiments of the present invention.

When making an anatomical cut in bone B, an implant stem must be implanted to match the resection angle of the resection surface R. This involves the use of instrumentation that measures the angle so the proper stem may be selected. Typically, this angle is read with an instrument connected to a reamer that is coaxial to the intramedullary canal. This approach may sometimes lead to inaccuracy, as the broach body may often fit differently in the cavity than the reamer. In other systems, the broach has marks that must be visually aligned with the resection surface, which may be prone to user error. Once the angle is determined, a trial is often assembled to match this angle. Often, this angle is incorrect, necessitating removal of the trial and insertion of a different assembly. These steps may often lead to inaccuracy and the increasing of operating time.

Broaches according to embodiments of the present invention include a pivoting neck that can be unlocked to allow movement between various angle selections. <FIG> illustrates a front elevation view of a broach <NUM>, according to embodiments of the present invention. <FIG> illustrates a lateral elevation view of the broach <NUM>, according to embodiments of the present invention. Broach <NUM> includes a proximal plate <NUM> having a proximal surface <NUM>, the proximal plate <NUM> pivoting about a stem <NUM> about pivot point <NUM>, according to embodiments of the present invention. The proximal plate <NUM> may be pivoted continuously between medial and lateral extents, but may be lockable to the stem <NUM> at a selected number of angles, for example three.

As illustrated in greater detail in <FIG>, the stem <NUM> may include three pockets <NUM> under the proximal plate <NUM> configured to receive a tip <NUM> of a screw <NUM> placed through locking hole <NUM>; the angle of the plate <NUM> may be locked with respect to the stem <NUM> by seating screw <NUM> through hole <NUM> and into one of the three angle pockets <NUM>, for example using a screw driver <NUM> as shown in <FIG> by inserting the driver end of the screw driver through hole <NUM> and into mating engagement with a receptacle <NUM> on the set screw <NUM>. The set screw <NUM> may be threadably engaged with a threaded inner portion of hole <NUM> as shown in <FIG>, such that it may be selectively, reversibly, and removably advanced into and out of engagement with one of the three pockets <NUM>, with each of the three pockets <NUM> corresponding to a different inclination angle of the plate <NUM> face <NUM>. The three pockets <NUM> may be shaped and/or placed so as to provide tactile feedback to the surgeon who is holding the driver tool <NUM> that is engaged with the set screw <NUM>, in order to permit the surgeon to feel when the set screw <NUM> is seated in one of the pockets <NUM> to lock the plate <NUM> with respect to the stem <NUM>. The screw <NUM> used for this locking may be a set screw <NUM> which remains in hole <NUM> during pivoting of the plate <NUM> with respect to stem <NUM>, according to embodiments of the present invention. The stem <NUM> may include pegs <NUM> fixedly coupled with the stem <NUM>, and the plate <NUM> may include slots <NUM> in which the pegs <NUM> slide in order to help constrain and limit the pivoting of the plate <NUM> with respect to the stem <NUM>, according to embodiments of the present invention.

The lateral surface of the broach <NUM>, as seen in <FIG>, includes a reference mark <NUM> on the stem <NUM> and index marks <NUM> on the lateral surface of the plate <NUM> to indicate at which angle the plate <NUM> has been locked with respect to the stem <NUM>. The plate <NUM> may include lateral and distal grooves <NUM>, <NUM> configured to receive prongs for coupling to an inserter <NUM>. Inserter <NUM> may be coupled to broach <NUM> and used to broach a cavity into the resected surface R of the bone B, as shown in <FIG>.

Inserter <NUM> includes an impaction head <NUM> to receive impaction forces from, for example, a mallet. Inserter <NUM> may further include a handle <NUM> configured to actuate the gripping and release mechanism for coupling the inserter <NUM> to the broach <NUM> and uncoupling the inserter <NUM> from the broach <NUM>, according to embodiments of the present invention. The inserter <NUM> may also include a removable depth stop <NUM>. During the broaching process, various sizes of broaches <NUM> may be coupled with inserter <NUM> and used to sequentially expand the cavity in bone B, for example from smallest to largest broach <NUM>. During the broaching process, the plate <NUM> (which is coupled with the inserter <NUM>) is free to rotate about pivot point <NUM>. Once the cavity of desired size is obtained, the broach <NUM> is inserted into the cavity until an underside of the depth stop <NUM> contacts the proximal resection surface R, as shown in <FIG>. As shown in <FIG>, a screwdriver is inserted into hole <NUM>, through inserter <NUM>, in order to lock the plate <NUM> to the stem <NUM> at the angle which is closest to the angle at which the plate <NUM> extends with respect to the stem <NUM> when the stem <NUM> is seated in the cavity and the depth stop <NUM> abuts the resection surface R, according to embodiments of the present invention. According to some embodiments of the present invention, this angle at which the plate <NUM> is locked to the stem <NUM> is the angle at which the plate <NUM> (or face of the broach <NUM>), resection surface R, and the distal surface of the depth stop <NUM> are all parallel. The handle <NUM> may be rotated to release the inserter <NUM> from the broach <NUM>, leaving the proximal surface <NUM> of the broach <NUM> substantially flush with the resection surface R, as shown in <FIG>. The broach <NUM> may also be used as a trial implant in order to test positioning and kinematic articular motion with various combinations of trays <NUM> and/or inserts <NUM>, or trial trays <NUM> and/or trial inserts <NUM>, according to embodiments of the present invention.

In other words, various broaches <NUM> of various sizes may be provided in a system or kit along with inserter <NUM> and corresponding implants. This design of broach <NUM> allows impaction while in the unlocked configuration. The inserter <NUM> connects to the broach <NUM> in a manner that allows full articulation of the plate <NUM> (which may also be referred to as a "neck") without interference with the bone B. The inserter <NUM> has a depth stop <NUM> whose bottom surface is flush with the face <NUM> of the broach <NUM>. During sequential broaching, the final broach is impacted until the depth stop <NUM> lays flat on the resection surface R. Since the inserter <NUM> / depth stop <NUM> is connected to the proximal pivoting neck <NUM>, it will automatically manipulate the proximal portion <NUM> so that face <NUM> is substantially coplanar to the resection surface R. A screwdriver can then be reached through the inserter to lock the plate <NUM> of broach <NUM> at the particular angle, and the inserter <NUM> may be removed. The broach <NUM> now replicates the implant stem at the proper angle, without additional insertion or removal of additional components that could jeopardize the press fit of the final implant stem. The trial head or trial adapter may then be connected to the broach <NUM>, and the entire construct removed from the bone B. The surgeon may compare the index marks <NUM> with the reference mark <NUM> (see <FIG>) of the locked broach <NUM> in order to determine the proper implant stem with the same inclination angle, and the trial eccentricity may also be read and replicated when selecting and/or creating the final implant. The various angular rotation positions at which the plate <NUM> may be locked to the stem <NUM> may correspond to the number of different implant stems offered in the same kit or system, according to embodiments of the present invention. In other words, the plates <NUM> rotate to selective positions with respect to the stem <NUM> in order to exactly replicate the inclination angle of a definitive implant. According to alternative embodiments of the present invention, the plate <NUM> may be locked at a particular angle with respect to the stem <NUM> prior to insertion if the resection angle is predetermined, such that the broach <NUM> acts as a rigid monoblock body. In some cases, the angle position of the plate <NUM> with respect to the stem <NUM> can be modified after insertion of the broach <NUM>, for example by loosening the set screw and locking the set screw into a different hole.

As discussed above, a shoulder implant involves insertion into and extraction from (during surgery) the humerus with an inserter / handle instrument. This instrument helps in the correct placement of the stem with respect to the patient's natural retroversion of the humerus, and also provides a method of removing the implant stem (and/or broach <NUM>) during surgery. Because the implant stem according to embodiments of the present invention is configured to be substantially flush with a resection surface R of the humerus, there is no collar or other mechanism above the resection surface to provide additional room for gripping by the inserter. Adding additional material to the stem may compromise desired biomechanics.

<FIG> illustrate an implant stem <NUM>, according to embodiments of the present invention. Stem <NUM> includes a stem portion <NUM> and two recessed grooves <NUM>, <NUM> on the proximal face <NUM> of the implant <NUM>. These grooves <NUM>, <NUM> provide for attachment to the inserter <NUM>, in a manner similar to the attachment of inserter <NUM> to grooves <NUM>, <NUM> of broach <NUM>. For example, the geometry of the grooves <NUM>, <NUM>, including their shape and/or arrangement with respect to the proximal face <NUM> of stem <NUM>, may be similar to or the same as the geometry of the grooves <NUM>, <NUM> of the broach <NUM>, including their shape and/or arrangement with respect to the proximal face <NUM> of the broach <NUM>. These grooves <NUM>, <NUM> are configured to work on a stem <NUM> that does not have any material resting above the resection surface R, according to embodiments of the present invention. According to some embodiments of the present invention, no contact is made with the implant taper connection <NUM>, because the taper <NUM> is often a critical component for locking the assembly of implant components to the stem <NUM> (e.g. the direct locking of the tray <NUM>, or a convex articulation surface bearing component, to the stem <NUM>, as well as the indirect locking of the inserter <NUM> to the stem <NUM> via the tray <NUM>). Impaction forces applied to inserter <NUM> are directed onto the proximal face <NUM> of the implant <NUM> (e.g. at locations <NUM>) and along the medial edge <NUM> of the medial groove <NUM>. According to some embodiments of the present invention, the medial groove <NUM> is tapered at ten degrees (e.g. the medial and lateral walls of the medial groove <NUM> are tapered ten degrees with respect to each other in a distally-converging manner as shown in <FIG>) to increase the stability of the implant groove and mating feature of the inserter <NUM> and guide the location of the impaction force to the top of the groove <NUM>. According to some embodiments of the present invention, the proximal surface <NUM> itself takes most of the impaction force via direct contact with a distal surface <NUM> of inserter. Both grooves <NUM>, <NUM> are angled with respect to the proximal face <NUM> in order to achieve better gripping and holding power for resisting forces during insertion, impaction, and/or extraction.

As illustrated in <FIG>, the inserter includes a lateral peg <NUM> which is fixed with respect to the rest of the inserter <NUM> and does not move, and also a medial peg <NUM> which is at least partially extendable and retractable from the distal surface <NUM> via actuation of the handle <NUM> of the inserter. The lateral peg <NUM> may be inserted into lateral groove <NUM>, and the medial peg <NUM> may be extended from surface <NUM> into the medial groove <NUM> in order to solidly grip the implant <NUM> with the inserter <NUM>. The converging angle of the lateral peg <NUM> with respect to the medial peg <NUM> draws the proximal surface <NUM> against the distal surface <NUM>, which also serves to better distribute impaction forces across a larger surface area of the proximal surface <NUM>, according to embodiments of the present invention.

<FIG> provide additional illustration about the operation of the inserter <NUM>, according to embodiments of the present invention. The inserter <NUM> includes two assemblies, the stationary assembly <NUM> and the movable assembly <NUM>. The movable assembly <NUM> includes a handle <NUM>, a spring link <NUM>, and a peg actuation link <NUM>. The peg actuation link <NUM> includes the lateral peg <NUM>. The handle <NUM> is rotatably (e.g. pivotably) coupled to the spring link <NUM> at pivot <NUM>, and the spring link <NUM> is rotatably (e.g. pivotably) coupled to the peg actuation link <NUM> at pivot <NUM>, according to embodiments of the present invention. The stationary assembly <NUM> includes a pivot location <NUM> at which the handle <NUM> pivotably attaches to the stationary assembly <NUM>, such that pivot <NUM> is at pivot location <NUM> and handle <NUM> pivots about stationary assembly <NUM> at pivot location <NUM>. Pivots <NUM> and <NUM> are not coupled to the stationary assembly <NUM>. Pivot <NUM> includes an axle or rod which is seated within the slot <NUM> of stationary assembly <NUM>, such that peg actuation link <NUM> rotates with respect to stationary assembly <NUM> at pivot <NUM> and also slides or translates with respect to stationary assembly <NUM> along slot <NUM>, according to embodiments of the present invention.

As shown in <FIG>, when handle <NUM> is in an open position, the peg <NUM> is retracted or substantially retracted with respect to a distal surface <NUM> of the inserter <NUM>. In this open position, the peg <NUM> is situated in a proximal end of the slot <NUM>. When the inserter is in this open position, the surgeon may easily pass the medial peg <NUM> into the slot <NUM> on the plate <NUM> of broach <NUM> (or into the slot <NUM> on the stem <NUM>), and may align the lateral peg <NUM> with the lateral slot <NUM> on the plate <NUM> of the broach <NUM> (or with the lateral slot <NUM> on the stem <NUM>). While the distal surface <NUM> of the inserter <NUM> is kept adjacent to the proximal surface <NUM> of plate <NUM> (or the proximal surface <NUM> of stem <NUM>), the handle <NUM> may be moved toward the closed position (e.g. back toward the stationary assembly <NUM>). Between the open position of <FIG> and the partially closed position of <FIG>, the movable assembly <NUM> advances the peg <NUM> along a substantially linear path into the slot <NUM> (or slot <NUM>) as the peg <NUM> translates from the proximal end of the slot <NUM> to the distal end of the slot <NUM>. Once the peg <NUM> reaches the distal end of the slot <NUM>, and the handle <NUM> is moved toward the closed position shown in <FIG>, the motion of the peg actuation link <NUM> shifts from one of primarily translation to one of primarily rotation, as the proximal end of link <NUM> (e.g. at pivot <NUM>) moves outwardly in a lateral direction and the link <NUM> rotates about peg <NUM> to angle the peg <NUM> within the slot <NUM> (or slot <NUM>) closer to the other peg <NUM>, so as to apply a gripping force to the broach <NUM> (or the implant <NUM> as the case may be). In the closed position of <FIG>, the spring link <NUM> has been compressed (e.g. the spring gap <NUM> has been slightly closed), and provides a spring force which helps to hold the peg <NUM> closed against the broach <NUM> (or implant <NUM>) when the handle <NUM> is in the closed position of <FIG>.

<FIG> also illustrates the removable connection of the depth stop <NUM> to the inserter <NUM>, via a set screw <NUM> which may be selectively advanced to engage with a receptacle in the inserter <NUM>. As described above, the distal surface <NUM> of the depth stop <NUM> may be aligned in parallel to the resection surface R in order to help select an angle for the pivoting plate <NUM> of the broach <NUM> which, in turn, may be used to select an inclination angle for a stem implant <NUM>, according to embodiments of the present invention.

Often, the humeral head is resected without angle guidance. The trial stems and implants are often set at particular inclination angles. As such, there is often some degree of resection correction that occurs in order to ensure that the resection surface is substantially coplanar with the face of the trial and the implant stem. Additionally, the resection cut may not be adequately flat, and/or may include bony features that would prevent proper assembly of the trial or implant stem with the head or reverse adapter trials or implants. To mitigate this issue, a planer may be used to flatten the resection surface. In order to decrease the risk of impingement with bone B prior to the planer sitting flush on the trial or implant stem face, the planer may be actuated in an elevated position parallel to the trial or implant stem face. The planer may maintain this parallel relationship through the entire reaming process until the planer is flush on the proximal face <NUM>, according to embodiments of the present invention.

Some reamer systems use a cannulated approach in which a post is threaded into a trial stem perpendicular to the implant face and a cannulated planer is engaged with and translates down the post to complete the reaming process. This involves a secondary instrument and two additional surgical steps (insertion and removal of the post). And typically such systems do not permit an ability to thread the post into the definitive implant, and thus permit reaming only with respect to the trial implant.

As illustrated in <FIG>, a reamer <NUM> includes a post <NUM> that maintains perpendicularity with the trial or implant stem face <NUM>. Post <NUM> is made of a material that does not damage the taper <NUM> but which rigidly engages the taper <NUM>. The post <NUM> moves axially independently of the reamer blade <NUM>, and may be spring loaded. The spring may bias the post <NUM> toward a normally extended position with respect to the reamer blade <NUM>. This permits the user to engage the taper <NUM> with the post <NUM>, apply power causing a reaming action of the reaming blade <NUM>, and then depress the reamer <NUM> (to load the spring) independent of the post <NUM>, to remove any bone that is proud of the trial or implant stem face <NUM> plane, according to embodiments of the present invention. The reamer <NUM> may function similarly with respect to a trial stem <NUM> and an implant stem <NUM>, and can be operated by hand or under power, for example via a Hudson connection. Various diameters of reamer heads <NUM> may be used to accommodate different resection diameters, according to embodiments of the present invention. A color-coded band <NUM> may be included on the reamer shaft <NUM> in order to distinguish it from other reamers or reamer heads <NUM> of different diameters.

<FIG> further illustrate the operation of reamer device <NUM>, according to embodiments of the present invention. An inner shaft <NUM> is coupled to a proximal connector <NUM> such that manual or motorized rotation of connector <NUM> rotates shaft <NUM> within sleeve <NUM>. Shaft <NUM> is also coupled to reamer blade <NUM>, such that rotation of shaft <NUM> rotates reamer blade <NUM>. A post shaft <NUM> is coupled to the shaft <NUM> such that post shaft <NUM> translates along a proximal-distal direction (e.g. axially) with respect to shaft <NUM>, but such that shaft <NUM> rotation is not imparted to post shaft <NUM>. As such, post shaft <NUM> freely rotates about shaft <NUM>. A spring <NUM> is situated between shaft <NUM> and post shaft <NUM>, and operates to bias the post shaft <NUM> in an extended position with respect to the shaft <NUM>. The post <NUM> is shaped so as to mate with the hole <NUM> in the implant <NUM> such that the central axes of post <NUM> and post shaft <NUM> are maintained substantially perpendicular to the proximal face <NUM> of the implant <NUM>. The post <NUM> may be threadably engaged with a distal end of the post shaft <NUM>, as illustrated in <FIG>. A force in the distal direction to push the shaft <NUM> and reamer blade <NUM> downward compresses spring <NUM> and moves the reamer blade <NUM> into contact with bone to ream the bone. The post shaft <NUM> may include a slotted portion <NUM> along a portion of its axial length, which may interact with a depth stop <NUM>. The slotted portion <NUM> may be, for example, a portion of the post shaft <NUM> with a smaller diameter along a certain axial length. The depth stop <NUM> may be, for example, a ring having an inner diameter that is larger or the same as the outer diameter of the post shaft <NUM> along the slotted portion <NUM>, but smaller than the outer diameter of the post shaft <NUM> immediately above and below the slotted portion <NUM>, according to embodiments of the present invention. When the shaft <NUM> and reamer blade <NUM> is pushed distally far enough, the distal advancement of the reamer blade <NUM> with respect to the post <NUM> will be stopped by the depth stop <NUM> hitting against the distal end of slotted portion <NUM>.

As an additional or alternative depth stop mechanism, the distal surface of the reamer blade <NUM> may include a non-cutting portion <NUM> that may be configured to halt the distal advancement of the reamer blade <NUM> with respect to the post <NUM> when the non-cutting portion <NUM> contacts a proximal surface <NUM> of the implant stem <NUM>, according to embodiments of the present invention. The non-cutting portion <NUM> may correspond in diameter to a minimum or maximum dimension of the radial extent of the proximal surface <NUM> of the implant stem <NUM> as measured from the central axis <NUM> of the hole <NUM> (see <FIG>), which prevents the cutting teeth <NUM> from roughening or damaging the proximal surface <NUM>, according to embodiments of the present invention. The non-cutting portion <NUM> may, in some embodiments, have an axial depth that is slightly greater than the axial extent of the cutting teeth <NUM>, in order to ensure that the teeth <NUM> do not contact the implant <NUM> face <NUM>. The reamer blade <NUM> may further include discontinuities <NUM> to permit cut bone to pass from the distal surface to the proximal side of the reamer blade <NUM>, according to embodiments of the present invention.

Varying philosophies exist among surgeons regarding the preferred inclination angle that should be used for a reverse shoulder prosthesis. For various reasons, <NUM> degrees is believed to be a compromise between high inclination angles that may cause scapular notching and low inclination angles that may result in more limited abduction or range of motion. A shoulder implant system that is capable of achieving a range of angles is optimal. Such a system provides surgeons with options to permit them to utilize their ideal configuration to provide optimum biomechanics, range of motion, and patient outcomes.

As shown in <FIG>, a reversed implant prosthesis according to embodiments of the present invention includes a humeral stem <NUM>, which may be made of metal, a reverse tray <NUM>, which may be made of metal, and a reverse insert <NUM>, which may be made of polymer such as polyethylene. According to some embodiments of the present invention, the humeral stem <NUM> may be offered in a number of different inclination angles, for example <NUM> degrees, <NUM> degrees, and <NUM> degrees. Stems <NUM> with additional or different inclination angles may be used. <FIG> illustrates stems <NUM> with three different inclination angles superimposed upon each other. As illustrated in <FIG>, an inclination angle is measured from a center axis of the stem portion <NUM> to a center axis of the taper <NUM>. According to some embodiments of the present invention, the center axis of stem portion <NUM> is a central axis of the distal end of the stem portion <NUM>. According to some embodiments of the present invention, the center axis of the stem portion <NUM> is the axis which, as an engineering constraint, is selected to coincide with a central axis of a long bone into which the stem <NUM> is designed to be implanted.

The reverse insert <NUM> may be offered in a number of different inclination angles, for example <NUM> degrees, <NUM> degrees, and <NUM> degrees. Inserts <NUM> with additional or different inclination angles may be used. As shown in <FIG>, the inclination angle of an insert <NUM> is measured as the angle between the bottom flat surface and the top flat surface. <FIG> illustrates an insert <NUM> with inclination angle of <NUM> degrees; <FIG> shows an insert <NUM>' with an inclination angle of <NUM> degrees; and <FIG> illustrates an insert <NUM>" with an inclination angle of <NUM> degrees.

As shown in <FIG>, different stem <NUM> and insert <NUM> combinations may be coupled together (e.g. via tray <NUM>) to achieve various total implant inclination angles. For example, using the stems <NUM> with inclination angles of <NUM>, <NUM>, and <NUM> degrees with inserts of <NUM>, <NUM>, and <NUM> degrees leads to total possible implant inclination angles of <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> degrees. <FIG> illustrates an implant assembly with a total inclination angle of <NUM> degrees; <FIG> illustrates an implant assembly with a total inclination angle of <NUM> degrees; and <FIG> illustrates an implant assembly with a total inclination angle of <NUM> degrees. <FIG> illustrates the various combinations of stem <NUM> angles with insert <NUM> angles to result in various total inclination angles, according to some embodiments of the present invention.

According to embodiments of the present invention, a kit includes at least three stems <NUM> each having a different inclination angle, at least one tray <NUM>, and at least three inserts <NUM> each having a different inclination angle. The fact that various inserts <NUM> can be matched with various stems <NUM> permits the stem to be placed precisely at the anatomic neck resection to best match the patient's anatomy, while still permitting a desired overall implant inclination angle (e.g. <NUM> degrees) to be achieved. This is superior to existing reverse prosthesis systems which often have a fixed angle stem that requires humeral resection at the specific angle, which often does not match the native anatomic neck.

During a normal humeral head replacement surgery, one of the stems <NUM> may be used to anchor the humeral head implant <NUM>. <FIG> illustrates a humeral head implant <NUM> used in an anatomical humeral head replacement and implanted with the same stem <NUM> that may be later re-used in converting the implant arrangement to a reverse shoulder implant. The distal surface <NUM> of the implant <NUM> is configured to abut the proximal surface <NUM> of the implant stem <NUM>, as shown in <FIG>. To fit the normal bony anatomy of the humerus, the stem <NUM> may be offered in several fixed inclination angles in the range of <NUM> to <NUM> degrees. The humeral head <NUM> for the anatomical implant may be offered according to a range of one or more given thicknesses for a given cut / resection diameter. For example, <FIG> illustrate three different sizes of humeral head implants all having the same stem <NUM> geometry - <FIG> shows an implant <NUM> with a humeral head portion <NUM>; <FIG> shows an implant <NUM>' with a humeral head portion <NUM>' that is larger (e.g. has a larger radius of curvature) than humeral head portion <NUM>; and <FIG> shows an implant <NUM>" with a humeral head portion <NUM>" that is larger (e.g. has a larger radius of curvature) than humeral head portion <NUM>'. The different sizes of implants <NUM>, <NUM>', and <NUM>" permit the surgeon to tune the implant to the soft tissue tension in the joint; each head <NUM>, <NUM>', <NUM>" is offered at different thicknesses / radii of curvature. A thicker head <NUM>" puts more tension on the soft tissue of the joint, while a thinner head <NUM> puts less tension on the soft tissue of the joint. The bottom surface <NUM> of the implants <NUM> are configured to be coplanar with the face <NUM> of the stem <NUM>. The assembly of the humeral head to the stem <NUM> may be achieved via a well-known Morse taper <NUM> forming a male protuberance on the humeral head and a female recess into the stem.

A multiplicity of humeral heads may be provided, and each may include a different position of the male protuberance for engaging the taper recess <NUM>. <FIG> shows one example of an implant <NUM>‴ having an angle SA formed between the central axis <NUM> of the stem <NUM>' and the central axis <NUM> of the humeral head portion <NUM>, according to embodiments of the present invention. The implant <NUM>‴ shown in <FIG> includes an angle SA of ten degrees. Anatomical shoulder implant systems according to embodiments of the present invention may include various implants <NUM>‴ having varying angles SA. For example, an anatomical shoulder implant kit may include implants <NUM>‴ having angles SA which pair with the inclination angles of the stems <NUM> offered, in order to permit the surgeon to pair a particular anatomical implant <NUM>‴ with a stem <NUM> having a particular inclination angle to achieve a final anatomical inclination angle that is consistent with commonly targeted final inclination angles in anatomical shoulder replacement, similar to how the inserts <NUM> may be paired with the same stems <NUM> in the manner described below for reverse shoulder implants, according to embodiments of the present invention.

In a reverse reconstruction of such a humeral head implant, the implant kit may include a reverse tray <NUM> of a given diameter featuring the same male taper / protuberance that was previously used with the humeral head implant, as well as at least one insert <NUM> of a diameter corresponding or paired to that of the tray <NUM> and designed to mate with the reverse tray, for example in the manners described above. This is illustrated in <FIG>, for example. The insert <NUM> may be angled accordingly to the stem <NUM> inclination angle such that the final implant inclination angle is in the range of <NUM> to <NUM> degrees, according to embodiments of the present invention. As shown in <FIG>, the center of the radius of curvature or center of rotation of the recess <NUM> in the insert <NUM> is not aligned with the axis of the cylindrical sidewall <NUM>, but is instead slightly offset toward a thinner portion of the insert <NUM>. As shown in <FIG>, a distance between the center of rotation CR (e.g. the origin or center of the radius of curvature or rotation of surface <NUM>) and the stem <NUM> axis may be between <NUM> and <NUM> millimeters, depending on the stem size and inclination angle, according to embodiments of the present invention.

A stem <NUM> according to embodiments of the present invention may be collarless, may be offered with various inclination angles (e.g. <NUM>, <NUM>, and <NUM> degrees), and may include a distance between the entry point of the taper <NUM> and the longitudinal axis of the stem <NUM>. A reverse tray <NUM> according to embodiments of the present invention may include an outer diameter of, for example, <NUM> millimeters. The tray <NUM> may be formed without a skirt, so as to mate with the collarless stem <NUM> design and to reduce the combination of stack-up or overall height. Although tray <NUM> is shown without a skirt, tray <NUM> may alternatively include a skirt in some embodiments. The thickness of the tray <NUM> between the bottom inside surface <NUM> and bottom outside surface <NUM> (see <FIG>) may be between three millimeters (e.g. the minimal thickness to avoid breakage of the tray <NUM>) and four millimeters (e.g. to avoid over-tension of the tray <NUM>), according to embodiments of the present invention. This component may alternatively have other thicknesses. In order to minimize the risk of breakage of the male taper <NUM>, a circular recess <NUM> is formed on the lower surface <NUM> of the tray <NUM> at the base of the taper <NUM>, according to embodiments of the present invention. The recess <NUM> may be between <NUM> to <NUM> millimeters deep (depending on the thickness of the tray <NUM>), and the cross-sectional shape of the recess <NUM> may be a semi-circle with a diameter of three millimeters. Various alternative trays <NUM> may be offered; for example, one tray <NUM> may have a taper <NUM> whose taper axis is aligned with a central axis of the tray <NUM>, while another tray <NUM> may have a taper <NUM> that is offset from the central axis of the tray <NUM>, according to embodiments of the present invention. Tray <NUM> may also be offered in a low offset variation in which the taper <NUM> axis is offset by about <NUM> millimeters with respect to the tray <NUM> axis, and in a high offset variation in which the taper <NUM> axis is offset by about <NUM> millimeters with respect to the tray <NUM> axis.

As described above, the insert <NUM> may be offered in various angles, for example <NUM>, <NUM>, and <NUM> degrees to interact with the angle of the stem <NUM> and to provide a desired final implant inclination angle (e.g. <NUM> degrees). According to some embodiments of the present invention, the center or origin of the radius of curvature or rotation of the concave articular surface <NUM> is offset from the axis of the engagement cylinder <NUM> by five to eight millimeters, in an offset direction toward the thinnest portion of the insert <NUM>. As described above, the insert <NUM> cooperates and engages with the tray <NUM> at any angular position of the insert <NUM> with respect to the tray <NUM>.

Embodiments of the present invention include stems <NUM> having a taper entry point <NUM> that is eight to eleven millimeters offset from the stem longitudinal axis, a reverse tray <NUM> with a male taper <NUM> being infinitely dialable at any angular position with respect to the stem <NUM>, an angled insert <NUM> having superior and inferior faces that form a given angle, with the superior face including an articular recess of which the center of rotation is offset, from the revolution axis of the engagement cylinder <NUM>, towards the thinner portion of the insert <NUM>. The engagement cylinder <NUM> of such insert <NUM> may be configured to engage with and cooperate with the tray <NUM> at any angular position of the insert <NUM> with respect to the tray <NUM>, according to embodiments of the present invention.

When a humeral head is resected and a trial stem is implanted, the cut surface of the humeral head may beneficially be protected from retractors and other instruments while the surgeon prepares the glenoid side of the joint. A circular plate may be rigidly attached to the trial stem to accomplish this purpose. Typical eccentric cut protectors connect to the trial stem via a screwdriver driving a captured screw. An additional instrument must often be used to connect to the cut protector to dial the eccentricity (e.g. to select the rotational position of the cut protector about its eccentric stem) and hold the cut protector in place while the screw is engaged with the screwdriver. This often requires both hands, multiple surgical steps, and multiple instruments.

As shown in <FIG>, a cut protector <NUM>, which may also be referred to as a cover element <NUM>, is eccentric, such that it has a boss <NUM> that is offset from a central axis of the cut protector <NUM>. Due to this eccentricity, the cut protector <NUM> is rotated to the proper location for maximum or optimal or desired resection coverage, then secured to the trial stem with a captured screw <NUM>. The captured screw <NUM> includes a driver interface recess <NUM> configured to mate with the correspondingly-shaped distal end of the driver tool <NUM>'. The driver tool <NUM>' may include a clip that provides friction and retains the screw, and thus the entire cut protector <NUM>, to the end of the driver tool <NUM>'. <FIG> illustrate a front perspective view of a driver tool used to rotate a cover element, according to embodiments of the present invention. The screw <NUM> includes a keyed proximal portion that mates with a keyed portion of the cut protector <NUM>. The screw is spring loaded (e.g. by spring <NUM>) to maintain this relationship, such that the screw <NUM> and the cut protector <NUM> rotate together.

When the driver tool <NUM>' is rotated, the screw <NUM> and cut protector <NUM> also rotate. Thus, the surgeon can be handed the cut protector <NUM> loaded onto the end (e.g. the hex end) of the driver tool <NUM>'. The surgeon may then mate the boss <NUM> on the bottom of the cut protector <NUM> with the cavity <NUM> in the trial stem, and rotate the driver tool <NUM>' handle so that the cut protector <NUM> is at a proper orientation for maximum or desired resection coverage.

When proper orientation is achieved, the driver tool <NUM>' may be depressed, which pushes down on the spring-loaded screw <NUM>. The proximal end of the screw <NUM> becomes disengaged from the keyed feature in the cut protector <NUM>, and the threaded distal end of the screw <NUM> contacts the mating female threads inside the trial stem. The screw may then be rotated to rigidly connect the two components (the cut protector <NUM> and trial stem), while the eccentricity of the cut protector <NUM> is maintained, according to embodiments of the present invention. The screwdriver may then be disengaged. A hole <NUM> in the boss <NUM> may facilitate cleaning of the cut protector <NUM>.

Various components or features or processes described herein may be used independently, and/or used in combination with one or more of the other components or features or processes described herein, in all possible combinations. Also, some or all of the components or features or processes described herein may optionally be used in combination with components or processes or features described in PCT Patent Application <CIT> and published on <CIT>.

Claim 1:
A system (<NUM>) for a modular reverse shoulder prosthesis, the system comprising:
a tray (<NUM>) having a proximal cavity including an inner sidewall;
an insert (<NUM>) having a distal end and a proximal end, the distal end configured to engage the proximal cavity of the tray, the distal end of the insert including an outer sidewall, the outer sidewall formed about an insert axis, the proximal end including a concave articular surface (<NUM>); and
fins (<NUM>, <NUM>') projecting inwardly from the inner sidewall of the proximal cavity, the fins projecting to an inner diameter that is smaller than the outer diameter of the outer sidewall, the fins arranged with respect to the proximal cavity of the tray such that the fins secure the insert against rotation about the insert axis with respect to the humeral component,
characterized in that
the insert is rotatable to any desired rotational angle about the tray before being locked to the tray by the fins.