Patent Description:
A shoulder joint comprises the juncture of the scapula, the clavicle and the humerus. The head of the humerus fits into a shallow socket of the scapula called the glenoid fossa to form a mobile joint. When the joint is articulated, the humeral head moves in the glenoid fossa to provide a wide range of motion. The shoulder joint may suffer from various maladies including rheumatoid arthritis, osteoarthritis, rotator cuff arthropathy, avascular necrosis, bone fracture or failure of previous joint implants. If severe joint damage occurs and no other means of treatment is found to be effective, then shoulder reconstruction may be necessary.

A shoulder joint prosthesis generally includes the replacement of the ball (glenosphere) of the humerus and, optionally, the socket (glenoid) of the shoulder blade with specially designed artificial components. The bio-kinematics, and thus the range of motion in the shoulder vary greatly among prospective patients for reconstruction shoulder surgery. The humeral component typically can have a metal shaft or stem with a body portion that can be embedded in the resected humerus and a generally hemispherical head portion supported on the stem. The head portion can slidingly engage a glenoid implant on the glenoid fossa. During reconstructive surgery, the components of the prosthesis can be matched with the bio-kinematics of the patient in an effort to maintain the natural range of motion of a healthy shoulder joint. Thus, a shoulder prosthesis design can be readily adaptable to a wide range of bio-kinematics for prospective patients.

In this regard, shoulder prostheses are generally available as either unitary structures or modular components. With unitary shoulder prosthesis, a large inventory of differently sized prostheses must sometimes be maintained to accommodate the different bone sizes and joint configurations of the prospective patients. With such unitary shoulder prosthesis, the patient can typically be evaluated by X-ray to determine approximate sizes of prostheses needed for reconstruction. A number of differently sized prostheses can be selected as possible candidates based upon this preliminary evaluation. Final selection of the appropriately sized prosthesis can be made during the surgery. With unitary shoulder prosthesis, each design can represent a compromise that is unable to achieve all of the natural range of motion of a healthy shoulder joint because of the fixed geometric configuration in their design.

Modular prostheses systems that can reduce the need to maintain large inventories of various sized components are known in the art. Conventionally, a humeral prosthesis can include two components: a humeral stem component and a spherical head releasably coupled to the stem Alternatively, a three component design is known in which the stem and spherical head are interconnected with an adapter. In either of the two-piece or three-piece designs, a radial offset or angulator inclination of the head relative to the stem can be provided in individual components. Different radial offsets or angular inclinations are achieved through the use of different adapters or heads. In this regard, conventional modular shoulder prosthesis kits can include multiple components such as adapters and heads to achieve a range of prosthetic options.

While providing an advantage over the unitary design in reducing the number of components needed, an inventory of head components and/or adapter components must sometimes be maintained to provide the desired range of geometric configurations with the conventional modular shoulder prostheses. These components can be readily adaptable to provide a range of geometric configurations, i.e. radial offsets of angular inclination while minimizing the number of components required.

Examples of humeral head trialing devices are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

For example, <CIT> discloses methods, instrumentation and devices for humeral implant positioning, including a trialing system utilizing an adjustment instrument and orientation indicia.

According to the invention, there is provided a trial apparatus as set out in claim <NUM>.

The present inventors have recognized, among other things, that a problem to be solved relates to the need for surgeons to have to select a desired position (i.e. location and orientation) of a humeral head and a corresponding humeral head trial. This process can be complex and can involve the movement of several components that are intricately attached to each other, marking of bone in several locations, cross-referencing different types of indicia on the humeral head and on the humeral head trial, cross-referencing various other criteria (e.g., bone coverage, location of a top dead center, location of a maximum offset, etc.) in order to properly position the humeral head for the shoulder prosthesis. Because of the complexity involved, the surgeon can be left with making an informed estimate of the desired humeral trial position when positioning the humeral head prosthesis. Thus, translating the position of the humeral head trial to that of the humeral head may not always be accurately performed.

The present subject matter can help provide a solution to various problems associated with the trialing of a humeral head by providing a trialing apparatus that can be configured to couple directly to a humeral stem. The trialing apparatus can also be positionally adjustable (relative to bone and the humeral stem) in a manner similar to that of the humeral head and stem adaptor. The trialing apparatus can include indicia that are the same as or very similar to those of the humeral head and stem adaptor. These indicia can be more widely spaced apart so incremental sizes can be easier to achieve. The configuration of the trialing apparatus makes selecting a proper location of the humeral head and stem adaptor easier and more intuitive. Furthermore, the present subject matter contemplates that one or more components of the trialing apparatus can be transparent or translucent. This allows one or more indicia on a bone facing side of the trialing apparatus to be visible to the surgeon during adjusting of a relative position between components of the trial apparatus. This enhanced visibility also allows the surgeon to adjust positions and mark the bone more accurately with reference to the one or more indicia.

<FIG> is a perspective view of a total shoulder arthroplasty system <NUM> comprising implanted a prosthetic glenoid <NUM> and an implanted humeral head prosthetic system <NUM>. The prosthetic glenoid <NUM> can include a glenoid <NUM> and humeral head prosthetic system <NUM> can include a humeral head <NUM>. The glenoid <NUM> can be secured to scapula bone S using any suitable means, such as a center post and a plurality of peripheral posts. The humeral head <NUM> can be secured to humerus bone H via a stem adaptor <NUM> (<FIG>) that connects to the humeral head <NUM> and to a humeral stem <NUM> (<FIG>, <FIG> and <FIG>).

The scapula bone S and the humerus bone H are typically reamed, resected or otherwise prepared to receive the glenoid <NUM> and the humeral stem <NUM>.

As can be seen in <FIG>, the humeral head <NUM> can be mounted to humerus bone H such that the perimeter <NUM> of humeral head <NUM> can be substantially aligned with edge <NUM> of humerus bone H. It can be desirable for the humeral head <NUM> to be properly centered on humerus bone H to achieve correct anatomic operation, for example, so that the humeral head <NUM> can smoothly rotate against glenoid <NUM>. As such, the position and size of the humeral head <NUM> can be selected so that the diameter of perimeter <NUM> substantially matches that of edge <NUM>. As described previously, it can be a complex process for the humeral head <NUM> to be optimally aligned with edge <NUM> upon implantation. As such, the present disclosure provides a system, apparatus and method for trialing, positioning and aligning the humeral head <NUM> with the humerus bone H.

<FIG> is a schematic illustration of a plurality of the humeral stems <NUM> that can be used with the total shoulder arthroplasty system <NUM>. The humeral stems <NUM> are available in different sizes and lengths as necessary based upon patient factors such as bone size and bone quality. The humeral stems <NUM> can optionally include different stem lengths, can have portions coated or otherwise formed of porous material to facilitate bony ingrowth. Each of the humeral stems <NUM> can include a proximal end <NUM>.

As shown in <FIG>, the proximal end <NUM> can protrude slightly from or be flush with the glenoid surface of the humerus bone H when the humeral stem <NUM> is positioned in the humerus bone H. Positioning of the humeral stem <NUM> into a reamed recess in the humerus bone H can be performed by an inserter or guide as shown in <FIG>.

The proximal end <NUM> of the humeral stem <NUM> can include a trunnion <NUM> (<FIG>), morse taper or other feature the facilitates connection of the humeral stem <NUM> to the stein adaptor <NUM> (<FIG>), and hence, the humeral head <NUM> as shown in <FIG>.

<FIG> shows a plan view of a front (i.e. surgeon facing or non-bone facing) of a humeral trial apparatus <NUM> according to an embodiment of the invention. The humeral trial apparatus <NUM> includes a body <NUM> and a thimble <NUM>. The body <NUM> and the thimble are moveably connected relative to one another via a joint <NUM>.

The body <NUM> can have a front surface <NUM> (sometimes referred to herein as a non-bone facing surface, proximal surface or top surface). The body <NUM> can be puck shaped, dome or hemispherical shaped according to some examples. The front surface <NUM> can terminate at a perimeter <NUM> of the body <NUM>. The body <NUM> can be circular in cross-section and can have a size and shape similar to that of the humeral head <NUM> (<FIG>).

As shown in <FIG>, the body <NUM> can have a recess <NUM> forming an opening in the front surface <NUM>. This opening can provide access, via the recess <NUM>, to a proximal end of the thimble <NUM> when the thimble <NUM> is inserted in and captured by the body <NUM> as shown in <FIG>. The proximal end of the thimble <NUM> can have a head <NUM>, recess or other feature that can be engaged (via the recess <NUM>) with a driver (shown in <FIG> and <FIG>). The driver can engage or otherwise couple with the thimble <NUM> to rotate the thimble <NUM> relative to the body <NUM> (and/or the humeral stem) as further described herein.

According to the invention and as shown in <FIG>, a portion <NUM> of the body <NUM> that can include all or part of the body <NUM> is transparent or translucent. This can facilitate the surgeon being able to view the position of the thimble <NUM>, for example. The body <NUM> includes a plurality of indicia <NUM>. The plurality of indicia <NUM> can be on one or more of the front surface <NUM>, can be within a recess of the body as further illustrated in <FIG>, and are on an opposing bone facing surface from the front surface <NUM>. The plurality of indicia <NUM> can be circumferentially arranged along or adjacent the perimeter <NUM> and can be arranged circumferentially around a centerline axis A of the body <NUM> as shown in <FIG>.

<FIG> shows the humeral trial apparatus <NUM>, in particular the thimble <NUM>, mounted to the trunnion <NUM> of the humeral stem <NUM>. As shown in <FIG>, the thimble <NUM> is configured to rotate (via the joint <NUM>) to adjust a position of the body <NUM> relative to the prosthetic stem <NUM>. To this end, <FIG> shows a driver <NUM> engaging the head <NUM> of the thimble <NUM> to facilitate the rotation of the thimble <NUM> relative to the body <NUM> and/or the humeral stem <NUM>. Put another way, the driver <NUM> can rotate the thimble <NUM> relative to the body <NUM> and can also be used to rotate the body <NUM> and thimble <NUM> relative to the humeral stem <NUM>.

<FIG> illustrate a recess <NUM> (part of joint <NUM>) within the body <NUM>. This recess <NUM> can be configured (sized and shaped) to receive the thimble <NUM>. The recess <NUM> can have an opening on a distal surface <NUM> (also referred to herein as a bone interfacing surface or stem facing surface) of the body <NUM> and can communicate with the recess <NUM> at a proximal portion.

<FIG> shows the hemisphere shape of the body <NUM> extending from the perimeter <NUM> to a domed peak that can be located at the centerline axis A of the body <NUM>. The recess <NUM> can be located at the domed peak, can oppose the recess <NUM> and can communicate with the recess <NUM>. In <FIG>, the thimble <NUM> is illustrated received in the recess <NUM> and can be rotatably captured by the body <NUM> in a snap-fit engagement. As show in <FIG>, a portion of the recess <NUM> can be formed by the one or more fingers <NUM>.

The snap-fit engagement can be facilitated by the one or more fingers <NUM> of the body <NUM>. The thimble <NUM> along the perimeter <NUM> can have a larger proximal diameter and then a smaller distal diameter. This change in diameter can form a lip <NUM> on the thimble <NUM>. The lip <NUM> can have a chamfer of about <NUM> to <NUM> degrees between the larger diameter proximal portion and the smaller diameter distal portion. These fingers <NUM> (also illustrated in <FIG>) can be figured to elastically deform slightly outward to receive the thimble <NUM>. As shown in <FIG>, the fingers <NUM> can have chamfers, projections or other features configured to engage with mating features (e.g., a chamfer or lip <NUM>) of the thimble <NUM> when the thimble <NUM> is fully inserted in the recess <NUM>. The lip <NUM> can be configured to be engaged by the one or more fingers <NUM> when the thimble <NUM> is inserted in the recess <NUM>. This engagement can retain the thimble <NUM> within the body <NUM> but can allow the thimble <NUM> to be rotated relative to the body <NUM>, for example.

<FIG> shows the body <NUM> with the thimble <NUM> removed to better illustrate the recess <NUM> and the one or more fingers <NUM>. The distal surface <NUM> can be substantially flat and can include some or all of the plurality of indicia <NUM>, for example. As shown in <FIG>, some of the plurality of indicia <NUM> can also be located within the recess <NUM>. As shown in <FIG>, a recess <NUM> can be located outward (as measured from centerline axis A) of the recess <NUM> and the one or more fingers <NUM>. This recess <NUM> can allow the one or more fingers <NUM> to elastically flex outward as previously described to receive the thimble <NUM> (<FIG>).

<FIG> show the thimble <NUM> in further detail. The thimble <NUM> can include the lip <NUM> along a periphery thereof and the head <NUM> as previously described. The thimble <NUM> can include a proximal surface <NUM> and indicia <NUM> as shown in <FIG>. The proximal surface <NUM> can extend from a periphery of the thimble <NUM> to the head <NUM>, for example. The indicia <NUM> can comprise a line or other marking on the proximal surface <NUM>, for example.

<FIG> show a distal side (also called a bone facing or stem facing side) of the thimble <NUM>. The thimble <NUM> includes a distal surface <NUM>, a recess <NUM>, one or more fingers <NUM> and a recess <NUM>.

As shown in <FIG>, the distal surface <NUM> can be substantially flat and can oppose the proximal surface <NUM>. The recess <NUM> can have an opening at the distal surface <NUM>. The recess <NUM> can extend proximally from the distal surface <NUM> to terminate adjacent or can communicate with the head <NUM>, as shown in <FIG> and <FIG>. The recess <NUM> can be offset from a centerline axis AA (<FIG> and <FIG>) and/or the head <NUM> of the thimble <NUM>. This offset can provide for adjustment of the position of the body <NUM> relative to the humerus bone as previously discussed and further illustrated herein.

The recess <NUM> can be partially formed by the one or more fingers <NUM>. The one or more fingers <NUM> can be configured to elastically deflect outward toward recess <NUM> when the recess <NUM> receives the trunnion <NUM> of the humeral stem <NUM>. The one or more fingers <NUM> can be configured to create a friction fit, snap-fit or other type of engagement with the trunnion <NUM> (<FIG>) as desired. This engagement can allow the thimble <NUM> to rotatably mount to the trunnion <NUM> as shown previously in <FIG>. The recess <NUM> can be tapered in a manner to receive but also allow for removal of the thimble <NUM> from the trunnion <NUM>.

<FIG> show another example of a humeral trial apparatus <NUM>. The humeral trial apparatus <NUM> can be configured in the manner of the humeral trial apparatus <NUM> previously described. Thus, the humeral trial apparatus <NUM> includes a body <NUM> and a thimble <NUM>. The body <NUM> is comprised of a translucent or transparent material (e.g., polysulfone such as Radel® polyphenylsulfone (PPSU)) so as to be fully or partially see through for the surgeon. As shown in <FIG>, due to this translucent or transparent material a plurality of indicia <NUM> are located on a distal surface <NUM> and/or a recess <NUM> of the body <NUM> and can be visible through the body <NUM> from a side opposing the distal surface <NUM>.

Thimble <NUM> can differ from the thimble <NUM> in that the head <NUM> can be a slot <NUM>, for example. Thimble <NUM> can be made of any suitable biocompatible material (e.g., metal, metal alloy such as titanium or titanium alloy, polymer, etc.). Thimble <NUM> need not be translucent or transparent, although the thimble can be translucent or transparent according to some examples.

<FIG> show a method for positioning a prosthetic head component with a prosthetic stem relative to a bone. This method can be performed using one of the humeral trial apparatuses described and illustrated previously herein.

<FIG> shows the driver <NUM> being utilized with one of the humeral trial apparatus <NUM> or <NUM>. As shown in <FIG>, the driver <NUM> can be rotated to rotate the thimble relative to the body <NUM>, <NUM> and the humeral stem (not shown). The surgeon may place a hand on the body <NUM>, <NUM> during rotation of the thimble to discourage the body <NUM>, <NUM> from co-rotating with the thimble. As discussed previously, the thimble <NUM>, <NUM> can be rotated until a perimeter (e.g., perimeter <NUM>) of the body <NUM>, <NUM> substantially matches that of the edge <NUM> of the humerus bone H as shown in <FIG>.

<FIG> shows the surgeon can start with the indicia <NUM> of the thimble <NUM>, <NUM> aligned with the one of the indicia <NUM>, <NUM> labeled "C". The thimble <NUM>, <NUM> can then be rotated as shown in <FIG> to match the edge <NUM> of the humerus bone H. This can change the relative positions of the body <NUM>, <NUM> and the thimble <NUM>, <NUM>. For example, the thimble <NUM>, <NUM> can be rotated to the "D and ½" position shown in <FIG>. Optionally, an amount of maximum offset from the edge <NUM> can be determined and noted if desired. Once the desired position for the body <NUM>, <NUM> on the bone is obtained, the indicia <NUM> of the thimble <NUM>, <NUM> can be extrapolated linearly outward (indicated with dashed line in <FIG>) to the edge <NUM> and the bone (such as the edge <NUM>) can be marked with a mark <NUM> as illustrated in <FIG> using known methods.

As shown in <FIG>, the humeral head <NUM> can be placed in into an impactor tray. The stem adapter <NUM> can have a body <NUM> configured to engage the humeral head <NUM>. The stem adaptor <NUM> can have a neck <NUM> configured to engage the humeral stem <NUM> (<FIG>, <FIG> and <FIG>).

In <FIG> and <FIG>, the stem adaptor <NUM> can be selected and can have an indicia <NUM> thereon. The indicia <NUM> can be configured in a similar or identical manner to the indicia <NUM> of the thimble <NUM>, <NUM>. For example, both can be lines. Similarly, the humeral head <NUM> can have a plurality of indicia <NUM>. The indicia <NUM> can be used with the plurality of indicia <NUM> as shown in <FIG> and <FIG>. The plurality of indicia <NUM> can be configured in a same or similar manner to the indicia <NUM>, <NUM> of the body <NUM>, <NUM>. Thus, the plurality of indicia <NUM> can be identical to (i.e. each can be circumferentially arranged about a centerline axis of the humeral head <NUM>, can be identically spaced and positioned, etc.) to the indicia <NUM>, <NUM> of the body <NUM>, <NUM>. Put another way, the body <NUM>, <NUM> can have the plurality of indicia <NUM>, <NUM> configured in an identical manner to those of the plurality of indicia <NUM> of the humeral head <NUM>. Thus, a relative position between the stem adaptor <NUM> and the humeral head <NUM> can be determined by replicating with the indicia <NUM> of the stem adaptor <NUM> and the plurality of indicia <NUM> of the humeral head <NUM>, the relative positions of the thimble <NUM>, <NUM> and the body <NUM>, <NUM> as determined using the indicia <NUM> of the thimble <NUM>, <NUM> and the plurality of indicia <NUM>, <NUM> of the body <NUM>, <NUM>.

As shown in <FIG>, the indicia <NUM> can be extrapolated linearly outward (as indicated with dashed line) to a periphery <NUM> of the humeral head <NUM>. A mark <NUM> can be made on the periphery in this location. In <FIG>, the humeral head <NUM> and the stem adaptor (not shown) can be adjusted to align the mark <NUM> with the mark <NUM> (<FIG>). Thus, the position of the stem adaptor and the humeral head on the humeral stem can be positioned to replicate the position of the body and thimble on the humeral stem.

Thus, the method of <FIG> can position the humeral head <NUM> with the prosthetic stem <NUM> relative to the humerus bone H. The method can include mounting the prosthetic stem to the bone, inserting the thimble within the body, mounting the thimble on the prosthetic stem, adjusting a relative position between the body and the thimble, marking the bone, recreating the relative position with a stem adaptor and the prosthetic head component; marking the prosthetic head component with the aid of an indicia on the stem adaptor once the recreating the relative position with the stem adaptor and the prosthetic head component is achieved, aligning the marking on the bone with the marking on the prosthetic head component, and attaching the prosthetic head component to the prosthetic stem via the stem adaptor.

<FIG> show a thimble <NUM> according to another example. The thimble <NUM> can differ from the thimble <NUM> or <NUM> previously illustrated in that the recess <NUM> can be replaced by a male feature such as a stem <NUM> having one or more flexible fingers <NUM> that define sidewalls <NUM> thereof The stem <NUM> via the one or more flexible fingers <NUM>, which can be separated by slots, can be configured to couple with the proximal head of the prosthetic stem in an adjustable manner as previously discussed. It is further recognized that according to further embodiments the body can include a male feature facilitating adjustable connection with the thimble, for example.

" In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indiciated.

Claim 1:
A trial apparatus (<NUM>) for selecting a position of a prosthetic head component on a humerus, the trial apparatus (<NUM>) comprising:
a body (<NUM>) having a plurality of indicia (<NUM>), wherein the body forms a portion of a joint (<NUM>);
a thimble (<NUM>) couplable to the body (<NUM>) via the joint (<NUM>), wherein the thimble is rotatable relative to the body (<NUM>) via the joint (<NUM>) and includes one or more indicia (<NUM>) for use with the plurality of indicia (<NUM>) of the body (<NUM>), and wherein the thimble is mountable to a prosthetic stem (<NUM>) implanted in the humerus,
wherein the plurality of indicia (<NUM>) are on a distal surface of the body (<NUM>), characterised in that the body (<NUM>) is translucent such that the plurality of indicia (<NUM>) are visible through the body (<NUM>) from a side opposing the distal surface.