Patent Description:
In total shoulder arthroplasty, a glenoid implant is attached to a prepared glenoid or scapula, and a humeral implant is attached to a prepared humerus. The humeral implant usually includes a ball or convex articular surface at a proximal end thereof which engages and moves relative to a socket or concave articular surface formed in a lateral aspect of the glenoid implant, although this arrangement is sometimes reversed so that the humeral implant includes the convex articular surface and the glenoid implant includes the convex articular surface. The ligaments and muscles of the shoulder surround the implants and maintain the humeral implant against the glenoid implant, while at the same time allowing relative movement therebetween.

Current implants frequently have a central peg or keel, occasionally with two or three small peripheral supporting pegs. These implants rely on the centrally placed anchoring element to provide the majority of the fixation. In situations where the surgeon encounters bone defects, bone cysts, or where a prior component has been removed, there is often a central defect in the bone where fixation is not possible.

Current instruments for standard glenoid arthroplasty, including drill bits, reamers, and trial implant components, and final implant components are frequently designed for the surgeon to approach the scapula along a direction perpendicular to the face of the glenoid portion of the scapula; this may be referred to as a direct lateral trajectory. However, the standard incisions and safest surgical approach for glenoid arthroplasty provide exposure for the surgeon which is more oblique, or antero-lateral. In order to facilitate the insertion of instruments perpendicular to the face of the glenoid, the surgeon may find it necessary to resect the articular portion of the humeral head and forcefully retract the patient's skin, muscle and remaining humerus out of the way posteriorly to obtain adequate exposure. In doing so, the surgeon may potentially injure nerves or blood vessels. Often the surgeon will purposely cut the biceps tendon or portions of the pectoralis major tendon to improve exposure to facilitate this step, as well as releasing the glenohumeral ligaments. All of this dissection, retraction, and removal of bone and soft tissue is done in order to allow the surgeon enough room to implant the glenoid prosthetic component.

Thus, there is a need for an implant anchoring mechanism that can be inserted from an oblique angle to allow for a less invasive and technically simpler surgical operation, for example, for anchoring a glenoid prosthetic component to scapular bone.

<CIT> discloses a reamer for use in minimally invasive hip replacement surgery. The reamer spindle comprises an elongate housing portion extending along a first axis, a distal neck portion extending along a second axis and a reamer head removably connected to the distal neck portion, wherein the second axis is disposed at an angle of between about <NUM> degrees and <NUM> degrees relative to the first axis.

The present disclosure sets forth an oblique-insertion anchoring mechanism for securing a glenoid prosthetic component to scapular bone. The anchoring mechanism can be inserted from an oblique angle to allow for a less invasive and technically simpler surgical operation. The anchoring mechanism is formed from a rounded dowel which projects from the medial aspect of a glenoid prosthetic component. The dowel projects at an angle which is not perpendicular to, or normal to, the medial side of the glenoid component, but is instead an acute angle less than <NUM> degrees. In the acute angle between the dowel and the medial side of the glenoid component there is a triangular reinforcement plate which buttresses the dowel and arises at a supplementary angle from the medial side of the glenoid component. The dowel and the edge of the reinforcement plate meet at the apex of the triangle.

It is contemplated that the number and location or placement of the anchoring elements will vary to accommodate different clinical situations.

The anchoring elements disclosed herein may be placed peripherally in a ring orientation, avoiding a bony central defect. Anchoring elements placed more peripherally provide more resistance to the effects of shear forces caused by the pressure of the humeral head during edge loading, as the distance and resultant lever arm decrease.

Biomechanically, the triangular arrangement of the dowel with the reinforcement plate allows the anchoring element to stabilize the body of the prosthesis from both legs of the triangular base to protect against both anterior and posterior eccentric forces. The triangular base of the anchoring element provides balanced anchoring to resist the anterior and posterior directed forces. The disclosed technology has fixation at both legs of the triangle, symmetric in distance from the edges of the body of the prosthesis, and all along the base of the triangle as well. The triangular shape also provides much larger surface area to resist superior and inferior directed forces than pegs alone. This is in contrast to a simple obliquely oriented peg which places the point of fixation of implant off center, allowing liftoff at the side farthest from the peg.

The disclosed design of the anchoring element may be even more preferable than traditional designs when glenoid deformity is present. Glenoid retroversion and glenoid vault bone loss are commonly seen in cases of advanced arthritis and the present design better fits the bony anatomy in these cases. This technology may also be preferable for revision glenoid arthroplasty operations.

The anchoring elements disclosed herein allow the prosthetic component to be inserted at an oblique angle. Therefore, there is less need to forcefully retract bone or soft tissues to obtain adequate exposure. The surgeon may be able to implant the prosthetic component without cutting the pectoralis major, the biceps tendon, or the glenohumeral ligaments. These tendons and ligaments serve as static and dynamic stabilizers of the humeral head during normal motion. If left intact, humeral motion remains more controlled and centered, reducing the incidence of humeral translation and contact with the far peripheral edges of the glenoid component. Reducing edge-loading results in less loosening forces transmitted to the anchoring elements, which is a common mode of failure of glenoid prosthetic components and total shoulder arthroplasty overall. Furthermore, the surgeon may not be compelled to resect the humeral head and may choose instead to use a bone-preserving humeral resurfacing arthroplasty component during the operation, which may further reduce operative time, blood loss and bone removal.

The inferior chamfer design of the lateral bearing surface of the glenoid component minimizes the incidence of impingement between the humeral component and the inferior articular margin of the glenoid prosthesis, thus reducing the likelihood of implant loosening and wear. Humeral impingement on the inferior glenoid is reported to be a cause of implant loosening and wear. Retrieval studies of loose failed glenoid implants have repeatedly demonstrated deformation at this inferior location.

For at least these reasons, the disclosed technology may simplify the operation, shorten the length of the operation, reduce soft-tissue dissection, reduce risk of neurovascular injury, reduce blood loss, reduce the need for bone resection, and may improve implant longevity.

Preservation of soft-tissues in glenoid preparation, optionally combined with the use of a humeral resurfacing component, may make shoulder arthroplasty more appealing for younger patients with significant degenerative disease, a patient group currently generally discouraged from undergoing shoulder arthroplasty.

An objective of the technology is to disclose a unique positioning of a dowel with planar buttress element in a glenoid prosthetic component.

Another objective of the technology is to disclose an improved glenoid prosthetic component that permit placement of anchoring elements in locations to better replicate normal human anatomy.

Yet another objective of the technology is to disclose an improved glenoid component that is inserted obliquely.

Yet another objective of the technology is to disclose an improved glenoid component having a dowel designed to match the specific anatomic shape of the surrounding bone.

Yet another objective of the technology is to disclose an improved glenoid prosthetic component having unique differential radius of curvature in the superior-inferior and anterior-posterior directions.

Yet another objective of the technology is to disclose an improved glenoid prosthetic component having a unique inferior chamfer.

Reamers are used in various medical procedures to prepare or shape bone surfaces. For example, reamers are used in various joint arthroplasty procedures. One example of an arthroplasty procedure is shoulder arthroplasty. Reamers may be used in shoulder arthroplasty procedures to prepare or shape bone surfaces on the glenoid or on the humeral head. Reamers may be used to prepare or shape bone surfaces which are planar, concave, convex, spherical, conical, or other surfaces of revolution.

In shoulder arthroplasty, the humeral head is in close proximity to the glenoid. The humeral head can interfere with an axial reamer (a conventional straight shaft instrument whose cutting face is perpendicular to the shaft axis) for preparation of the glenoid socket. Similar conditions exist in other joints of the body, such as the elbow, wrist, hip, knee, ankle, or joints of the hand, foot, spine, jaw, or pelvis. Tight joint spaces or interfering bony or soft tissue structures may be dealt with by increasing the size of the surgical incision, performing more extensive dissection to increase exposure of the surgical site, or using retractors or other tools to move interfering structures out of the way, but these techniques increase surgical trauma to the joint, increase the risk of collateral damage beyond that essential to the arthroplasty procedure, and may destabilize the reconstructed joint.

There is a need for reamers adapted for use in tight joint spaces, which would need little to no joint distraction, dissection, retraction, or exposure. This disclosure presents four reamers, each adapted for use in tight joint spaces by having an offset shaft arrangement. The present invention, which is defined in claim <NUM>, concerns a system comprising an arthroplasty implant and a reamer system.

Other objectives and advantages of this technology will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate examples of this technology. The drawings constitute a part of this specification and include examples of the present technology and illustrate various objects and features thereof.

While examples of the present technology are shown and described in detail below, it will be clear to the person skilled in the art that variations, changes and modifications may be made without departing from its scope. As such, that which is set forth in the following description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is to be defined by the following claims.

Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature or a feature with similar functionality. Not every feature of each example is labeled in every figure in which that example appears, in order to keep the figures clear. Similar reference numbers (e.g., those that are identical except for the first numeral) are used to indicate similar features in different examples.

Exemplary embodiments of the technology will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the technology, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the present system is not intended to limit the scope of the invention, as claimed, but is merely representative exemplary of exemplary embodiments of the technology.

The phrases "connected to," "coupled to" and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be functionally coupled to each other even though they are not in direct contact with each other. The term "abutting" refers to items that are in direct physical contact with each other, although the items may not necessarily be attached together. The phrase "fluid communication" refers to two features that are connected such that a fluid within one feature is able to pass into the other feature.

Standard medical planes of reference and descriptive terminology are employed in this specification. A sagittal plane divides a body into right and left portions. A mid-sagittal plane divides the body into bilaterally symmetric right and left halves. A coronal plane divides a body into anterior and posterior portions. A transverse plane divides a body into superior and inferior portions. Anterior means toward the front of the body. Posterior means toward the back of the body. Superior means toward the head. Inferior means toward the feet. Medial means toward the midline of the body. Lateral means away from the midline of the body. Axial means toward a central axis of the body. Abaxial means away from a central axis of the body. Ipsilateral means on the same side of the body. Contralateral means on the opposite side of the body. These descriptive terms may be applied to an animate or inanimate body.

<FIG>, and the corresponding description below, come from <CIT>.

Referring to <FIG>, a glenoid component <NUM> includes a body <NUM> with a lateral articular surface <NUM> and an opposite medial bone-facing surface <NUM>. Glenoid component <NUM> includes the following features, which may be substantially similar to, or the same as, the corresponding features of glenoid component <NUM> of <CIT>: peripheral wall <NUM>, lateral peripheral edge <NUM>, lateral peripheral relief <NUM>, medial peripheral edge <NUM>, medial peripheral relief <NUM>, superior portion <NUM>, inferior portion <NUM>, anterior portion <NUM>, posterior portion <NUM>, S-I radius of curvature <NUM>, A-P radius of curvature <NUM>, inferior chamfer <NUM>, superior anchoring element <NUM>, inferior anchoring element <NUM>, middle anchoring element <NUM>, dowel or mast <NUM>, mast angle <NUM>, triangular reinforcement plate or sail <NUM>, supplementary angle <NUM>, pedestal <NUM>, face <NUM>, fixation features <NUM>, ridge <NUM>, groove <NUM>, slot <NUM>, flat surface <NUM>, and fenestration <NUM>. Glenoid component <NUM> also includes a chamfer blend radius <NUM> and a hole <NUM>. The chamfer blend radius <NUM> is adjacent to the inferior chamfer <NUM>. The chamfer blend radius <NUM> is more centrally located than is the inferior chamfer <NUM>. The hole <NUM> extends lengthwise into the dowel <NUM> of middle anchoring element <NUM>, and may receive a radiographic marker (not shown). Glenoid component <NUM> lacks an anterior relief or a posterior relief.

Referring to <FIG>, a reamer <NUM> includes a coupling <NUM>, a shaft <NUM>, and a working portion <NUM>. The coupling <NUM> and the working portion <NUM> are arranged at opposite ends of the shaft <NUM>, which is straight in this example. The coupling <NUM> connects the reamer <NUM> to a torque source, such as a power handpiece or a T-handle, so that the reamer <NUM> may be rotated or spun about a central longitudinal axis <NUM> of the shaft <NUM> by the torque source. The working portion <NUM> includes a body <NUM> with a first surface <NUM> and an opposite bone-facing surface <NUM>. The bone-facing surface <NUM> may match the bone-facing surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of one of the glenoid components disclosed in <CIT>. The body <NUM> may be described as bi-lobular, the two lobes <NUM>, <NUM> established by opposing indentations <NUM>, <NUM>. In other examples, the body <NUM> may be round or nearly round. The bone-facing surface <NUM> includes bone removal features <NUM>, which may be teeth, serrations, ridges and grooves, knurling, a sandpaper texture, or the like. In the example shown, the bone removal features <NUM> are alternating ridges <NUM> and grooves <NUM>. The cutting edges of the ridges <NUM> are interrupted or scored by cross grooves <NUM>. The bone removal features <NUM> on lobe <NUM> are oriented opposite to the bone removal features <NUM> on lobe <NUM> so that the bone removal features <NUM> on each lobe <NUM>, <NUM> are oriented to efficiently remove bone as the reamer <NUM> spins in one direction. A trough <NUM> separates the bone removal features <NUM> on lobe <NUM> from the bone removal features <NUM> on lobe <NUM>. A drill tip <NUM> protrudes from the bone-facing surface <NUM>. The drill tip <NUM> may be end-cutting, side-cutting, or both; an end-cutting example is shown. A second, larger diameter, drill feature <NUM> may protrude from the bone-facing surface <NUM> around the base of the drill tip <NUM>. The drill feature <NUM> may be end-cutting, side-cutting, or both; an end-cutting example is shown.

Referring now to <FIG>, a method of using the reamer <NUM> to prepare an implantation site for the glenoid components will now be described. One of skill in the art will appreciate that there are many methods for preparing a glenoid to receive the disclosed glenoid components, and that the method shown below represent a few examples of the methods available. Other methods contemplated may include the use of a saw, such as a reciprocating or oscillating saw; a burr, which may be motorized; a punch; an osteotome; and/or a curette, used alone or in combination with one or more drills, guides, and/or cutting jigs. These tools may be used to prepare the glenoid to receive one or more dowels and/or reinforcement plates. Furthermore, while the illustrated method and corresponding instruments include three anchoring elements, in other examples of the technology, the method and corresponding instruments include one or more anchoring elements corresponding to the number and location of the anchoring elements that are present on the selected glenoid prosthetic component.

<FIG> illustrates a normal intact right shoulder joint including a scapula <NUM> and a humerus <NUM>. The scapula includes a glenoid fossa <NUM>, a coracoid process <NUM>, and an acromion process <NUM>.

<FIG> illustrates the step of forming a pilot hole <NUM> in the glenoid fossa. A small drill or reamer (not shown) may be used freehand at this point to expand the pilot hole <NUM>.

<FIG> illustrates the step of reaming the glenoid fossa with the reamer <NUM>. The reamer <NUM> may be insinuated between the humeral head and the glenoid fossa <NUM> by first engaging the drill tip <NUM> in the pilot hole <NUM> with one of the indentations <NUM>, <NUM> cradling the humeral head. The reamer shaft <NUM> may be inclined at an acute angle with respect to the glenoid fossa at this point. With the drill tip <NUM> in the pilot hole, there is sufficient leverage to push the humeral head posteriorly with the reamer <NUM>. The reamer shaft <NUM> may end up perpendicular to the glenoid fossa at this point. Once the reamer shaft <NUM> is properly aligned with the glenoid fossa <NUM> and the scapula <NUM>, the reamer <NUM> may be spun to prepare a reamed surface <NUM> in the glenoid fossa <NUM>. At the same time, the drill tip <NUM> and drill feature <NUM>, if present, prepare hole <NUM> in the former location of the pilot hole <NUM>. <FIG> shows the scapula <NUM> after the reaming step.

The components disclosed herein may be fabricated from metals, alloys, polymers, plastics, ceramics, glasses, composite materials, or combinations thereof, including but not limited to: PEEK, titanium, titanium alloys, commercially pure titanium grade <NUM>, ASTM F67, Nitinol, cobalt chrome, stainless steel, ultra high molecular weight polyethylene (UHMWPE), biocompatible materials, and biodegradable materials, among others. Different materials may be used for different parts. Coatings may be present. Different materials may be used within a single part. Any component disclosed herein may be colored, coded or otherwise marked to make it easier for a user to identify the type and size of the component, the setting, the function(s) of the component, and the like.

The reamers disclosed herein may be used to prepare a bone bed to receive or support an arthroplasty implant. The prepared bone bed may be smooth. The reamers may also create a central pilot hole; the pilot hole may be used to locate subsequent bone preparation guides and/or tools. The reamers may be designed with various offset shaft arrangements, such as the following examples, to adapt the reamers for use in tight joint spaces where a conventionally designed reamer would meet with interference from body structures. In one example, the disclosed reamers may be used for glenoid preparation in shoulder arthroplasty. In this example, one interfering structure is the humeral head. Of course, the disclosed reamers may also be used in other arthroplasty procedures for other skeletal joints.

In this specification, an axis is a straight line which has infinite length, zero breadth, and zero thickness. An object may rotate about an axis or move along an axis. Two coplanar axes are collinear if they have more than one point in common; in fact, all of their points are in common. Two coplanar axes intersect if they have exactly one point in common. Two coplanar axes are parallel if they have zero points in common. Two non-coplanar axes are skew if they do not intersect and are not parallel; they also have zero points in common.

In this specification, polyaxial means movement which occurs about multiple axes. Polyaxial and multiaxial are synonymous. A ball-and-socket joint is one example of a joint which provides polyaxial movement about a point, a center point of rotation. The range of motion of a polyaxial joint may be conical, wherein the vertex of the cone lies at the center point of rotation of the polyaxial joint. The range of motion of a polyaxial joint may be expressed as the included angle of the cone, or as the half-angle of the cone. The skeleton includes polyaxial joints, such as the shoulder joint and the hip joint.

Design objectives for the disclosed reamers include: prepare a smooth surface of revolution, where the axis of revolution may be perpendicular to the natural bony feature being reamed; minimize contact with surrounding body structures, such as the opposing bone of the joint, so that the reamer is not used as a pry bar to distract the joint; and ease of use equivalent to a conventional straight reamer. Any of the disclosed reamers may prepare the glenoid fossa of the scapula <NUM> as shown in <FIG>.

Referring to <FIG>, an offset reamer <NUM> includes a reamer head <NUM>, a reamer coupler <NUM>, a working tip <NUM>, a shaft <NUM>, and a handle <NUM>. <FIG> show various views of offset reamer <NUM>.

The reamer head <NUM> is a round part with a central longitudinal rotational axis <NUM>, a convex obverse side <NUM>, or bone-facing side or cutting side (<FIG>), and a reverse side <NUM> (<FIG>). The obverse side <NUM> may be flat or concave in other examples devoted to other joints around the body. The obverse side <NUM> includes bone removal features <NUM>, which may be teeth, serrations, ridges and grooves, knurling, a sandpaper texture, or the like. In the example shown, the bone removal features <NUM> are sharpened edges on radial arms <NUM> of the reamer head <NUM>. Eight arms <NUM> are shown in the example, although any number of arms may be provided. The arms <NUM> in the example are separated by windows <NUM> or apertures. In other examples, the reamer head <NUM> may share some or all of the characteristics of body <NUM> disclosed above. The reamer head <NUM> includes a central aperture <NUM> (<FIG>), which may include a drive portion <NUM> adjacent to the reverse side <NUM> and a circular portion adjacent to the obverse side. The drive portion <NUM> may be a hex socket, as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction.

Referring to <FIG>, the reamer coupler <NUM> includes a central longitudinal rotational axis <NUM>, a head <NUM>, a flange <NUM> under the head, a drive feature <NUM> under the flange, and a shaft <NUM> under the drive feature. The reamer coupler <NUM> may be referred to as a coupling which connects the offset reamer <NUM> to a prime mover or torque source such as a power driver or T-handle so that the reamer head <NUM> may be rotated or spun about the axis <NUM>. The head <NUM> may include a drive portion <NUM>, which may be a hex socket, as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The drive feature <NUM> may be a hex key, as illustrated in <FIG>, or another configuration for cooperation with the drive portion <NUM> of the aperture <NUM> of the reamer head <NUM> for torque transmission in at least one rotational direction. The shaft <NUM> may include cutting flutes at least along the leading tip, and may therefore be called a drill tip. <FIG> illustrates this configuration. The shaft <NUM> may be spring loaded, and may be biased to be normally extended or normally retracted. In the latter situation, the shaft <NUM> may only extend outwardly when a driver (discussed below) is engaged with the drive portion <NUM>.

The working tip <NUM> may be coupled to one end of the shaft <NUM> and the handle <NUM> may be coupled to the other end of the shaft <NUM> to form a handle assembly. The working tip <NUM>, the shaft <NUM>, and the handle <NUM> may be permanently or temporarily coupled together. For example, the working tip <NUM> and/or handle <NUM> may be permanently welded to the shaft <NUM>. Alternatively, the working tip <NUM> and/or handle <NUM> may be temporarily threaded or snapped to the shaft <NUM>. The working tip <NUM> includes a shaft portion <NUM> for connection to the shaft <NUM> and a plate portion <NUM> that extends obliquely from the shaft portion. The shaft <NUM> includes a central longitudinal axis <NUM>, with which the shaft portion <NUM> aligns when the shaft <NUM> and the shaft portion <NUM> are connected. The plate portion <NUM> includes an obverse side <NUM>, or bone-facing side, and a reverse side <NUM> opposite the bone-facing side. The plate portion is pierced by an aperture <NUM> or hole which may extend through the obverse side <NUM> and the reverse side <NUM>.

The reamer head <NUM>, the reamer coupler <NUM>, and the working tip <NUM> are operatively assembled by inserting the head <NUM> through the aperture <NUM> so that the flange <NUM> contacts the bone-facing side <NUM> of the plate portion <NUM>, and inserting the shaft <NUM> through the circular portion of the aperture <NUM> of the reamer head <NUM> so that the drive feature <NUM> engages the drive portion of the aperture <NUM> of the reamer head <NUM>; in the illustrated example, this involves inserting the hex key <NUM> into the hex socket drive portion <NUM> of aperture <NUM>. The working tip <NUM> may be said to carry the reamer coupler <NUM> and the reamer head <NUM>. The head <NUM>, the plate portion <NUM>, the shaft <NUM>, the drive feature <NUM>, and/or the aperture <NUM> may include a retention element, such as a ball detent, clip, retaining ring, groove, taper, twist, or the like, to keep the head <NUM>, the plate portion <NUM>, the shaft <NUM>, the drive feature <NUM>, and/or the aperture <NUM> coupled together until intentionally disassembled. The operative assembly of the reamer head <NUM>, the reamer coupler <NUM>, and the working tip <NUM> may be referred to as a working portion of the offset reamer <NUM>.

When the reamer head <NUM>, the reamer coupler <NUM>, and the working tip <NUM> are operatively assembled, at least the reamer head <NUM> and the reamer coupler <NUM> may be rotationally coupled or fixed together with axes <NUM>, <NUM> collinear. Together, the reamer head <NUM> and the reamer coupler <NUM> may rotate freely relative to the working tip <NUM> about axis <NUM>. The handle assembly of the working tip <NUM>, the shaft <NUM>, and the handle <NUM> may be manipulated by a user to control the location and orientation of the reamer axis <NUM>.

A driver, such as the reamer driver <NUM> shown in <FIG>, may include a Hudson connector or torque bit which couples to a prime mover or torque source, such as a power driver or a T-handle. The tip of the driver may be directly engaged with the reamer coupler <NUM>, and the driver may be rotated by the prime mover about a central longitudinal rotational axis of the driver, or driver axis, to turn the reamer coupler <NUM> and the reamer head <NUM> about axis <NUM>. In other words, the driver may be rotationally coupled to the reamer coupler <NUM> and the reamer head <NUM>. For example, the driver may have a straight hex key drive tip to engage the hex socket drive portion <NUM> so that the driver axis is in line with, or coaxial with, the axis <NUM>. The driver may alternatively have a ball drive tip, such as the ball hex key drive tip <NUM> shown in <FIG>, which permits the driver axis to be polyaxially obliquely angled, or polyaxially angularly offset, relative to the rotational axis <NUM> of the reamer head <NUM> in the manner discussed below for offset reamer <NUM>. In this example with the ball hex key drive tip, the driver axis may be described as being angularly offset from, or noncollinear with, the rotational axis <NUM> of the reamer head <NUM>, so that the driver axis and the axis <NUM> have no more than a single mathematical point in common, and that only if the driver axis and the axis <NUM> intersect. Therefore, the driver may be referred to as an offset driver or an offset drive shaft due to the unconstrained angular offset between the driver axis and the rotational axis <NUM> of the reamer head <NUM>. The driver may alternatively include other adaptations to permit the driver to be obliquely angled, or angularly offset, relative to the rotational axis <NUM> of the reamer head <NUM>, such as a universal joint, a flexible shaft portion, a bevel gear acting against the reamer head <NUM> and/or the reamer coupler <NUM>, a ball Torx drive (hexalobular), a ball star drive, or various other ball polygonal or polylobular design. More specifically, the driver may have a ball drive tip with five or more corners or points, which may provide a smooth feel with less turbulence or kicking during actuation. While the ball hex key drive tip is an example which provides polyaxial angular offset, other examples may provide a fixed angular offset. In use, the driver may be angularly repositioned relative to the axis <NUM> at any time the user desires, whether or not the driver is being actuated or rotated. The driver may be repositioned independently of any manipulation of the reamer head axis <NUM> or the handle assembly, so that the angular offset between the axis <NUM> and the driver axis is continuously variable.

Referring to <FIG>, another offset reamer <NUM> includes a reamer head <NUM>, a reamer coupler <NUM>, a working tip <NUM>, a shaft <NUM>, and a handle <NUM>. <FIG> show various views of offset reamer <NUM>. Offset reamer <NUM> also includes a first bushing <NUM> and a second bushing <NUM>, which are seen best in <FIG>. Offset reamer <NUM> is shown with a reamer driver <NUM>, which may be used interchangeably with offset reamers <NUM>, <NUM>.

The reamer head <NUM> is a round part with a central longitudinal rotational axis <NUM>, a convex obverse side <NUM>, or bone-facing side or cutting side (<FIG>), and a reverse side <NUM> (<FIG>). The obverse side <NUM> may be flat or concave in other examples devoted to other joints around the body. The obverse side <NUM> includes bone removal features <NUM>, which may be teeth, serrations, ridges and grooves, knurling, a sandpaper texture, or the like. In the example shown, the bone removal features <NUM> are sharpened edges on radial arms <NUM> of the reamer head <NUM>. Eight arms <NUM> are shown in the example, although any number of arms may be provided. The arms <NUM> in the example are separated by windows <NUM> or apertures. In other examples, the reamer head <NUM> may share some or all of the characteristics of body <NUM> disclosed above. The reamer head <NUM> includes a central socket <NUM> in the reverse side <NUM> (<FIG>). The central socket <NUM> may include a drive portion <NUM> adjacent to the reverse side <NUM>, and may include a circular portion adjacent to the obverse side. The drive portion <NUM> may be a threaded socket, as illustrated in <FIG> and <FIG>, or another configuration for torque transmission in at least one rotational direction. The reamer head <NUM> is illustrated with a central drill point <NUM> protruding from the obverse side <NUM>. In this example, the central drill point <NUM> is integral with the reamer head <NUM>. Alternately, the central drill point may be separate from the reamer head <NUM>, and may be integral with the reamer coupler <NUM>, and may protrude through a circular portion of the central aperture <NUM> in the manner described above for reamer head <NUM> and reamer coupler <NUM>. The central drill point <NUM> may include cutting flutes at least along the leading tip. The central drill point <NUM> may be spring loaded, and may be biased to be normally extended or normally retracted. In the latter situation, the central drill point <NUM> may only extend outwardly when a driver (discussed below) is engaged with the reamer coupler <NUM>.

Referring to <FIG>, the reamer coupler <NUM> includes a central longitudinal rotational axis <NUM>, a head <NUM>, a drive feature <NUM> under the head, and a shaft <NUM> between the head <NUM> and the drive feature <NUM>. The reamer coupler <NUM> may be referred to as a coupling which connects the offset reamer <NUM> to a prime mover or torque source such as a power driver or T-handle so that the reamer head <NUM> may be rotated or spun about the axis <NUM>. The head <NUM> may include a drive portion <NUM>, which may be a hex socket, as illustrated in <FIG>, a hexalobular socket, or another configuration for torque transmission in at least one rotational direction. The drive feature <NUM> may be a threaded shaft, as illustrated in <FIG>, or another configuration for cooperation with the drive portion <NUM> of the socket <NUM> of the reamer head <NUM> for torque transmission in at least one rotational direction.

The first bushing <NUM> includes a tubular body, or tube <NUM>. A flange <NUM> projects circumferentially outwardly around one end of the tube <NUM>.

The second bushing <NUM> includes a tubular body, or tube <NUM>. A flange <NUM> projects circumferentially outwardly around one end of the tube <NUM>.

The working tip <NUM> may be coupled to one end of the shaft <NUM> and the handle <NUM> may be coupled to the other end of the shaft <NUM> to form a handle assembly. The working tip <NUM>, the shaft <NUM>, and the handle <NUM> may be permanently or temporarily coupled together. For example, the working tip <NUM> and/or handle <NUM> may be permanently welded to the shaft <NUM>. Alternatively, the working tip <NUM> and/or handle <NUM> may be temporarily threaded or snapped to the shaft <NUM>. The working tip <NUM> includes a shaft portion <NUM> for connection to the shaft <NUM> and a plate portion <NUM> that extends obliquely from the shaft portion. The shaft <NUM> includes a central longitudinal axis <NUM> with which the shaft portion <NUM> aligns when the shaft <NUM> and the shaft portion <NUM> are connected. The plate portion <NUM> includes an obverse side <NUM>, or bone facing side, and a reverse side <NUM> opposite the bone-facing side. The plate portion <NUM> is pierced by an aperture <NUM> or hole which may extend through the obverse side <NUM> and the reverse side <NUM>.

The reamer head <NUM>, the first bushing <NUM>, the working tip <NUM>, the second bushing <NUM>, and the reamer coupler <NUM> are operatively assembled by inserting the tube <NUM> of the first bushing <NUM> into the aperture <NUM> of the working tip <NUM> so that the flange <NUM> rests against the reverse side <NUM>; inserting the tube <NUM> of the second bushing <NUM> into the aperture <NUM> of the working tip <NUM> so that the flange <NUM> rests against the obverse side <NUM>; inserting the reamer coupler <NUM> into the tubes <NUM>, <NUM> so that the head <NUM> rests against the flange <NUM> and the drive feature <NUM> extends beyond the flange <NUM>; and coupling the drive feature <NUM> to the drive portion <NUM> of the central socket <NUM> of the reamer head, for example by threading the drive feature <NUM> into the drive portion <NUM>. The working tip <NUM> may be said to carry the reamer coupler <NUM> and the reamer head <NUM>, as well as the first bushing <NUM> and the second bushing <NUM>. The reamer head <NUM>, the first bushing <NUM>, the working tip <NUM>, the second bushing <NUM>, and/or the reamer coupler <NUM> may include a retention element, such as a ball detent, clip, retaining ring, groove, taper, twist, or the like, to keep the reamer head <NUM>, the first bushing <NUM>, the working tip <NUM>, the second bushing <NUM>, and/or the reamer coupler <NUM> coupled together until intentionally disassembled. The operative assembly of the reamer head <NUM>, the first bushing <NUM>, the working tip <NUM>, the second bushing <NUM>, and the reamer coupler <NUM> may be referred to as a working portion of the offset reamer <NUM>.

When the reamer head <NUM>, the first bushing <NUM>, the working tip <NUM>, the second bushing <NUM>, and the reamer coupler <NUM> are operatively assembled, at least the reamer head <NUM> and the reamer coupler <NUM> may be rotationally coupled or fixed together with axes <NUM>, <NUM> collinear. Together, the reamer head <NUM> and the reamer coupler <NUM> may rotate freely relative to the working tip <NUM> about axis <NUM>; the bushings <NUM>, <NUM> may also rotate freely relative to the reamer coupler <NUM> and/or the working tip <NUM>, or they may be rotationally coupled or fixed to the reamer coupler <NUM> or the working tip <NUM>. The handle assembly of the working tip <NUM>, the shaft <NUM>, and the handle <NUM> may be manipulated by a user to control the location and orientation of the reamer axis <NUM>.

The reamer driver <NUM>, shown in <FIG>, may be used interchangeably with offset reamers <NUM>, <NUM>. The reamer driver <NUM> includes a Hudson connector <NUM> or torque bit, a shaft <NUM>, a drive tip <NUM> opposite the torque bit, and a central longitudinal rotational axis <NUM>. The Hudson connector <NUM> of the reamer driver <NUM> may couple to a prime mover or torque source, such as a power driver or a T-handle. The drive tip <NUM> may be directly engaged with the reamer coupler <NUM>, and rotated by the prime mover about the axis <NUM> to turn the reamer coupler <NUM> and the reamer head <NUM> about axis <NUM>. In other words, the reamer driver <NUM> may be rotationally coupled to the reamer coupler <NUM> and the reamer head <NUM>. For example, the reamer driver <NUM> may have a straight hex key drive tip to engage the hex socket drive portion <NUM> so that axis <NUM> is in line with, or coaxial with, the axis <NUM>. The reamer driver <NUM> may alternatively have a ball drive tip <NUM> as shown, which permits the rotational axis <NUM> of the reamer driver <NUM> to be polyaxially obliquely angled, or polyaxially angularly offset, relative to the rotational axis <NUM> of the reamer head <NUM>. <FIG> illustrates an example in which the axis <NUM> is obliquely angled, or angularly offset, relative to the axis <NUM>. In this example with the ball drive tip, the driver axis <NUM> may be described as being angularly offset from, or noncollinear with, the rotational axis <NUM> of the reamer head <NUM>, so that the driver axis <NUM> and the axis <NUM> have no more than a single mathematical point in common, and that only if the driver axis <NUM> and the axis <NUM> intersect. Therefore, the reamer driver <NUM> may be referred to as an offset driver or an offset drive shaft due to the unconstrained angular offset between the axis <NUM> and the axis <NUM>. The reamer driver <NUM> may alternatively include other adaptations to permit the reamer driver <NUM> to be obliquely angled, or angularly offset, relative to the rotational axis <NUM> of the reamer head <NUM>, such as a universal joint, a flexible shaft portion, a bevel gear acting against the reamer head <NUM> and/or the reamer coupler <NUM>, a ball Torx drive (hexalobular), a ball star drive, or the like. Various ball drive tips may be substituted for the ball hex drive tip <NUM> shown, such as Torx, hexalobular, star, or various other polygonal or polylobular shapes. More specifically, the reamer driver <NUM> may have a ball drive tip <NUM> with five or more corners or points, which may provide a smooth feel with less turbulence or kicking during actuation. While the ball hex key drive tip is an example which provides polyaxial angular offset, other examples may provide a fixed angular offset. In use, the reamer driver <NUM> may be angularly repositioned relative to the axis <NUM> at any time the user desires, whether or not the driver is being actuated or rotated. The driver <NUM> may be repositioned independently of any manipulation of the reamer head axis <NUM> or the handle assembly, so that the angular offset between the axis <NUM> and the driver axis <NUM> is continuously variable.

With continued reference to <FIG>, axis <NUM> and axis <NUM> may intersect at a point <NUM>. As explained above, in some instances axis <NUM> and axis <NUM> do intersect at a single mathematical point. In other examples, axis <NUM> and axis <NUM> may be skew, in which case point <NUM> may be referred to as a virtual intersection point, or a point where axis <NUM> and axis <NUM> are closest together. In any case, axis <NUM> may move relative to axis <NUM> due to manipulation of the reamer driver <NUM> while the point <NUM> remains at a fixed distance or depth relative to the reamer head <NUM> (particularly a fixed distance from the cutting side, measured along axis <NUM>) or the reamer coupler <NUM> (particularly a fixed distance within the drive portion <NUM>, when the drive portion <NUM> is a socket as shown).

Offset reamers <NUM>, <NUM> are mechanically simple designs. The reamer heads <NUM>, <NUM> are captured at the end of angled shafts <NUM>, <NUM> respectively. The shafts are used to position and stabilize the reamer heads <NUM>, <NUM>. The reamer heads <NUM>, <NUM> are driven, or turned, by a separate driver, such as reamer driver <NUM>, which directly engages drive portions <NUM>, <NUM> on the reamer couplers <NUM>, <NUM> respectively. The reamer driver <NUM> is shown with a ball hex feature on the distal end that allows the shaft <NUM> to be misaligned, angularly offset, or obliquely oriented, relative to the reamer head axis <NUM>. The specific example shown provides up to <NUM> degrees of angular misalignment, although any amount of misalignment is contemplated as a matter of design choice. In other words, the magnitude of the angular offset or oblique angle may be greater than zero degrees and less than <NUM> degrees. The offset reamers <NUM>, <NUM> may be driven by a prime mover or torque source such as a power instrument, or manually using a T-handle. The prime mover may couple directly to a fitting such as a Hudson connector or torque bit of the driver.

The reamer coupler <NUM> includes a shaft <NUM> which may be a drill tip, and which may protrude through the obverse of the reamer head <NUM>; and the reamer head <NUM> includes a central drill point <NUM>; both features may eliminate a separate step to drill a pilot hole. The drill tips may be face cutting only, lacking any cutting edges along their long axis. This feature may prevent the drill tips from skiving laterally under load.

Offset reamers <NUM>, <NUM> provide easy clearance around interfering structures, due to the angled shafts <NUM>, <NUM> and handles <NUM>, <NUM> relative to the reamer heads <NUM>, <NUM>. The operation of offset reamers <NUM>, <NUM> is stable because the stabilizing action of the handles <NUM>, <NUM> and the torque drive loads are structurally separated. Offset reamers <NUM>, <NUM> may provide effective cutting action due to the direct loading of the cutting head through a separate drive shaft, such as shaft <NUM>. The drive shaft <NUM> need only be angled sufficiently to avoid contact with the interfering structures. The construction of the offset reamers <NUM>, <NUM> is simple and cost effective to manufacture.

A method of using the offset reamer <NUM> to prepare an implantation site for the glenoid components will now be described. The method may include the steps of providing the offset reamer <NUM>, with the handle <NUM>, the shaft <NUM>, and a working portion including the working tip <NUM>, the reamer head <NUM>, and the reamer coupler <NUM>; inserting the working portion into a shoulder joint (<FIG>) along a first trajectory so that the shaft <NUM> is in the pilot hole <NUM>; providing the reamer driver <NUM>, with the shaft <NUM>, the Hudson connector <NUM> or torque bit at one end of the shaft <NUM>, and the drive tip <NUM> at an opposite end of the shaft <NUM> from the Hudson connector <NUM> or torque bit; coupling the Hudson connector <NUM> or torque bit to a prime mover; engaging the drive tip <NUM> of the reamer driver <NUM> with the drive portion <NUM> of the reamer coupler <NUM> along a second trajectory which is angularly offset from the first trajectory; actuating the prime mover to rotate the reamer driver <NUM> about the axis <NUM> to turn the reamer coupler <NUM> and the reamer head <NUM> about the axis <NUM>, thereby preparing a reamed surface <NUM> in the glenoid fossa <NUM> (<FIG>); and removing the working portion and the reamer driver <NUM>.

The step of providing the offset reamer <NUM> may include the steps of coupling the handle <NUM>, shaft <NUM>, and working tip <NUM> together to form a handle assembly; and assembling the reamer head <NUM>, reamer coupler <NUM>, and working tip <NUM> to form a working portion, wherein the reamer head <NUM> and the reamer coupler <NUM> are rotationally coupled or fixed together and free to rotate relative to the working tip <NUM> about axis <NUM>.

The step of inserting the working portion into a shoulder joint may include manipulating the handle <NUM> to orient or re-orient the working portion. The first trajectory may be between the humeral head and the glenoid fossa <NUM> (<FIG>), and aligned with or parallel to the glenoid articular surface. One can appreciate that in the shoulder joint, the first trajectory may be from an anterior or an anterolateral approach to the joint so that the working portion presents its thinnest profile as it enters the joint. The second trajectory may be tangent to the humeral head and aimed at the drive portion <NUM> of the reamer coupler <NUM>. The second trajectory may be from an anterolateral or lateralized approach to the joint so that the drive tip <NUM> presents its smallest profile as it enters the joint. Because the working portion and the reamer driver <NUM> are separate items, introduced into the joint separately or one at a time, and engaged together in the joint, each item may be introduced into the joint along a trajectory that offers the least resistance to insertion or the least amount of joint distraction or dissection. An integral or non-separable design, by contrast, may have a larger insertion profile which may dictate an insertion trajectory which results in relatively more resistance, joint distraction, and/or dissection.

The step of actuating the prime mover may be preceded by, or performed simultaneously with, a step of reorienting the reamer driver <NUM> to lie along a third trajectory which is angularly offset from the first trajectory and the second trajectory. Reorienting the reamer driver <NUM> may involve polyaxial rotation of the reamer driver <NUM> about the drive tip <NUM>. The third trajectory may thus be non-coplanar with the first trajectory and the second trajectory.

The preceding method applies equally to the offset reamer <NUM>. The step of providing the offset reamer <NUM> may include the steps of coupling the handle <NUM>, shaft <NUM>, and working tip <NUM> together to form a handle assembly; and assembling the reamer head <NUM>, first bushing <NUM>, second bushing <NUM>, reamer coupler <NUM>, and working tip <NUM> to form a working portion, wherein the reamer head <NUM> and the reamer coupler <NUM> are rotationally coupled or fixed together and free to rotate relative to the working tip <NUM> about axis <NUM>.

Referring to <FIG>, yet another offset reamer <NUM> includes a reamer head <NUM>, an offset assembly <NUM>, and a Hudson connector <NUM> or torque bit which receives torque from a prime mover. <FIG> show various views of offset reamer <NUM>.

The reamer head <NUM> is a round part with a central longitudinal rotational axis <NUM>, a convex obverse side <NUM>, or bone-facing side or cutting side (<FIG>), and a reverse side <NUM> (<FIG>). The obverse side <NUM> may be flat or concave in other examples devoted to other joints around the body. The obverse side <NUM> includes bone removal features <NUM>, which may be teeth, serrations, ridges and grooves, knurling, a sandpaper texture, or the like. In the example shown, the bone removal features <NUM> are sharpened edges on radial arms <NUM> of the reamer head <NUM>. Six arms <NUM> are shown in the example, although any number of arms may be provided. The arms <NUM> in the example are separated by windows <NUM> or apertures. In other examples, the reamer head <NUM> may share some or all of the characteristics of reamer heads <NUM>, <NUM> or body <NUM> disclosed above. The reamer head <NUM> includes a central drive portion <NUM> protruding from the reverse side <NUM>. The drive portion <NUM> may be a hex key, as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The reamer head <NUM> is illustrated with a central boss or drill point <NUM> protruding from the obverse side <NUM>. In this example, the central boss or drill point <NUM> is integral with the reamer head <NUM>. This feature may include cutting flutes at least along its leading tip. The central boss or drill point <NUM> may be spring loaded, and may be biased to be normally extended or normally retracted.

Referring to <FIG>, the offset assembly <NUM> includes a first gear assembly <NUM>, a sleeve <NUM>, and an offset drive shaft <NUM>. The offset assembly <NUM> may include a second gear assembly <NUM>.

Referring to <FIG>, the first gear assembly <NUM> includes a drive shaft <NUM>, a first housing <NUM>, a second housing <NUM>, a first gear <NUM>, a second gear <NUM>, a third gear <NUM>, an idler pin <NUM>, an idler bushing <NUM>, a first drive bushing <NUM>, a second drive bushing <NUM>, a bearing assembly <NUM>, a first fastener <NUM>, and a second fastener <NUM>.

Referring to <FIG>, the drive shaft <NUM> includes a central longitudinal rotational axis <NUM>, a head <NUM>, a flange <NUM> under the head, a drive feature <NUM> under the flange, and a shaft <NUM> under the flange. The drive shaft <NUM> may be referred to as a coupling which connects the offset reamer <NUM> to a prime mover or torque source such as a power driver or T-handle so that the reamer head <NUM> may be rotated or spun about the axis <NUM>. The head <NUM> may include a drive portion <NUM>, which may be a hex key, as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The drive feature <NUM> may be a hex socket, as illustrated in <FIG>, or another configuration for cooperation with the drive portion <NUM> of the reamer head <NUM>, or for cooperation with a prime mover or the Hudson connector <NUM> or torque bit, for torque transmission in at least one rotational direction.

The gears <NUM>, <NUM>, <NUM>, idler pin <NUM>, and bushings <NUM>, <NUM>, <NUM> serve to transfer torque laterally between the drive shafts <NUM> and the offset drive shaft <NUM>, and may preserve the clockwise or counterclockwise rotational direction of the torque. Bevel gears, universal joints, flexible shafts, or other torque offset couplings, torque offset apparatus, torque transfer apparatus, or gearboxes may be substituted for the gears <NUM>, <NUM>, <NUM>, idler pin <NUM>, and bushings <NUM>, <NUM>, <NUM>. The gears or equivalents may be said to indirectly couple the drive shaft <NUM> to the offset drive shaft <NUM>. While the offset drive shaft <NUM> is shown parallel to and laterally offset from the drive shafts <NUM> by a non-zero distance, other angular relationships of these parts are contemplated.

The first housing <NUM>, the second housing <NUM>, the first fastener <NUM>, and the second fastener <NUM> serve to enclose and stabilize the drive shaft <NUM>, the gears <NUM>, <NUM>, <NUM>, the idler pin <NUM>, the bushings <NUM>, <NUM>, <NUM>, and the bearing assembly <NUM>.

When the first gear assembly <NUM> is operatively assembled, the drive shaft <NUM> is rotationally coupled to the first gear <NUM>. The second gear <NUM> meshes with the first gear <NUM> and the third gear <NUM> for torque transmission.

The second gear assembly <NUM> may be identical to the first gear assembly <NUM>.

The offset drive shaft <NUM> includes a central longitudinal rotational axis <NUM> and drive feature <NUM> at one end of the offset drive shaft. A second drive feature <NUM> may be included. The drive feature <NUM> may be a hex key as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The drive feature <NUM> may directly receive torque from a prime mover if the second gear assembly <NUM> is not present.

When the offset assembly <NUM> is operatively assembled, the offset drive shaft <NUM> is rotationally coupled to the third gear <NUM> of the first gear assembly <NUM>, and to the third gear <NUM>' of the second gear assembly <NUM>, if present. The axis <NUM> and the axis <NUM> may be described as parallel with a distance offset having a magnitude greater than zero, so that the axis <NUM> and the axis <NUM> have zero mathematical points in common. The same applies to axis <NUM> and axis <NUM>. Axis <NUM> and axis <NUM> may be collinear, as shown in <FIG>, or parallel, or another orientation.

The Hudson connector <NUM> or torque bit receives torque from a prime mover. The Hudson connector <NUM> includes a central longitudinal rotational axis <NUM>, a drive portion <NUM>, and a drive feature <NUM>.

When the offset reamer <NUM> is operatively assembled, the reamer head <NUM> is rotationally coupled or fixed to the drive shaft <NUM> of the first gear assembly <NUM> with axes <NUM>, <NUM> collinear, and the Hudson connector <NUM> or torque bit is rotationally coupled or fixed to the drive shaft <NUM>' of the second gear assembly <NUM>, if present, with axes <NUM>, <NUM>' collinear.

Offset reamer <NUM> uses two gear assemblies <NUM>, <NUM> to establish an offset drive shaft that reaches around interfering structures to deliver torque from a driver to the reamer head <NUM>. The two gear assemblies <NUM>, <NUM> are identical. On one side <NUM>, the reamer head <NUM> is coupled to the drive shaft <NUM> and both components rotate together about axis <NUM>; therefore, the drive shaft <NUM> may be referred to as a reamer coupler <NUM>. On the opposite side <NUM>, a Hudson connector <NUM> couples directly to another drive shaft <NUM>' and thence to a prime mover or torque source, which drives the Hudson connector <NUM> and the drive shaft <NUM>' to rotate about axis <NUM>. The sleeve <NUM> of the offset reamer <NUM> may be used as an offset handle. The offset reamer <NUM> may be operated using a familiar prime mover or torque source, such as a power driver or T-handle, coupled directly to the Hudson connector and indirectly to the offset drive shaft <NUM> by way of the gears. A single size offset reamer <NUM> may be used with all reamer sizes. Multiple driver interfaces may be used instead of the one shown, allowing the offset reamer <NUM> to be used with many instrument brands or styles.

The design of offset reamer <NUM> features ease of use equivalent to a conventional straight reamer while eliminating shaft contact with interfering structures. The prime mover or torque source axis of rotation is co-axial with the reamer head axis of revolution. This provides a good visual reference to ensure that the reamer is oriented properly relative to the bone surface. Additionally, this feature allows all axial force to be transferred to the reamer along its natural axis.

Referring to <FIG>, yet another offset reamer <NUM> includes a reamer head <NUM>, an offset assembly <NUM>, a shaft <NUM>, and a handle <NUM>. <FIG> show various views of offset reamer <NUM>.

Referring to <FIG>, the offset assembly <NUM> includes a gear assembly <NUM>, a sleeve <NUM>, an offset drive shaft <NUM>, a Hudson bushing <NUM>, and a bushing cap <NUM>. The offset assembly may include a second gear assembly (not shown) which may be identical to gear assembly <NUM>, and which may be arranged in the offset reamer <NUM> in the manner described above for second gear assembly <NUM> of offset reamer <NUM>.

Referring to <FIG>, the gear assembly <NUM> includes a drive shaft <NUM>, a first housing <NUM>, a second housing <NUM>, a first gear <NUM>, a second gear <NUM>, a third gear <NUM>, an idler pin <NUM>, a first idler bushing <NUM>, a second idler bushing <NUM>, a first drive bushing <NUM>, a second drive bushing <NUM>, a main bushing <NUM>, a shoulder screw <NUM>, a first fastener <NUM>, a second fastener <NUM>, a third fastener <NUM>, and a fourth fastener <NUM>.

The drive shaft <NUM> includes a central longitudinal rotational axis <NUM>, a head <NUM>, a flange <NUM> under the head, a drive feature <NUM> opposite the head, and a shaft <NUM> under the head. The drive shaft <NUM> may be referred to as a coupling which connects the offset reamer <NUM> to a prime mover or torque source such as a power driver or T-handle so that the reamer head <NUM> may be rotated or spun about the axis <NUM>. The head <NUM> may include a drive portion <NUM>, which may be a hex key, as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The drive feature <NUM> may be a hex socket, as illustrated in <FIG>, or another configuration for cooperation with the drive portion <NUM> of the reamer head <NUM> for torque transmission in at least one rotational direction.

The gears <NUM>, <NUM>, <NUM>, idler pin <NUM>, and bushings <NUM>, <NUM>, <NUM>, <NUM>, <NUM> serve to transfer torque laterally between the drive shafts <NUM> and the offset drive shaft <NUM>, and may preserve the clockwise or counterclockwise rotational direction of the torque. Bevel gears, universal joints, flexible shafts, or other torque offset couplings, torque offset apparatus, torque transfer apparatus, or gearboxes may be substituted for the gears <NUM>, <NUM>, <NUM>, idler pin <NUM>, and bushings <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The gears or equivalents may be said to indirectly couple the drive shaft <NUM> to the offset drive shaft <NUM>. While the offset drive shaft <NUM> is shown parallel to and laterally offset from the drive shaft <NUM> by a non-zero distance, other angular relationships of these parts are contemplated.

The first housing <NUM>, the second housing <NUM>, the shoulder screw <NUM>, the first fastener <NUM>, the second fastener <NUM>, the third fastener <NUM>, and the fourth fastener <NUM> serve to enclose and stabilize the drive shaft <NUM>, the gears <NUM>, <NUM>, <NUM>, idler pin <NUM>, and bushings <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Referring to <FIG>, the offset drive shaft <NUM> includes a central longitudinal rotational axis <NUM>, a drive feature <NUM> at one end of the offset drive shaft, and a Hudson connector <NUM> or torque bit at the other end of the offset drive shaft. The drive feature <NUM> may be a hex key as illustrated in <FIG>, or another configuration for torque transmission in at least one rotational direction. The Hudson connector <NUM> or torque bit receives torque from a prime mover.

When the offset assembly <NUM> is operatively assembled, the offset drive shaft <NUM> is rotationally coupled to the third gear <NUM> of the first gear assembly <NUM>, and to the third gear of the second gear assembly, if present. The axis <NUM> and the axis <NUM> may be described as parallel with a distance offset having a magnitude greater than zero, so that the axis <NUM> and the axis <NUM> have zero mathematical points in common.

When the offset reamer <NUM> is operatively assembled, the reamer head <NUM> is rotationally coupled or fixed to the drive shaft <NUM> of the first gear assembly <NUM> with axes <NUM>, <NUM> collinear.

The offset reamer <NUM> is similar to the offset reamer <NUM> in that offset reamer <NUM> utilizes a gear assembly <NUM> to move an offset drive shaft <NUM> which is offset from, but parallel to, the reamer head axis of revolution <NUM>. A handle <NUM> has been added in this example to locate and stabilize the offset reamer <NUM> during use. The handle <NUM> permits the user to exert a counter-moment to compensate for any moment due to the offset shaft arrangement. The handle <NUM> may also be included in offset reamer <NUM>. A drill tip <NUM> is included on the reamer head <NUM> to combine the steps of creating a pilot hole and reaming the bone surface. A three-gear construct <NUM>, <NUM>, <NUM>, similar to that described for offset reamer <NUM>, is employed to create the desired lateral offset between axis <NUM> and axis <NUM>. However, in this case, the ball bearing assemblies <NUM> have been replaced by bushing style bearings <NUM>, <NUM>, <NUM>, <NUM>, <NUM> used throughout to minimize the overall size and volume of the offset reamer <NUM>. Other offset constructs may be substituted.

The design of offset reamer <NUM> features a simple design that may have an attractive cost of goods. Offset reamer <NUM> has a small, compact design. Parallel reamer head and offset shaft axes provide a good visual indicator for reamer orientation. A large handle provides good stability.

It should be understood that the present systems, kits, apparatuses, and methods are not intended to be limited to the particular forms disclosed. Rather, they are to cover all combinations, modifications, equivalents, and alternatives falling within the scope of the claims.

The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) "means for" or "step for," respectively.

The term "coupled" is defined as connected, although not necessarily directly, and not necessarily mechanically.

The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one," but it is also consistent with the meaning of "one or more" or "at least one. " The term "about" means, in general, the stated value plus or minus <NUM>%. The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or.

The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including") and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. As a result, a method or device that "comprises," "has," "includes" or "contains" one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that "comprises," "has," "includes" or "contains" one or more features, possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

In the foregoing Detailed Description, various features are grouped together in several examples for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the examples of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed example. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate example.

Any methods disclosed herein comprise one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified.

Reference throughout this specification to "an embodiment" or "the embodiment" means that a particular feature, structure or characteristic described in connection with that embodiment is included in at least one embodiment.

Similarly, it should be appreciated that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims.

Recitation in the claims of the term "first" with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element. It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the technology.

Claim 1:
A system comprising:
an arthroplasty implant component (<NUM>) comprising an articular surface (<NUM>) and an opposite bone-facing surface (<NUM>); and
a reamer system comprising a reamer head (<NUM>, <NUM>, <NUM>, <NUM>) and an offset drive shaft (<NUM>, <NUM>, <NUM>), wherein the reamer head rotates about a first axis (<NUM>, <NUM>, <NUM>, <NUM>), and the offset drive shaft rotates about a second axis (<NUM>, <NUM>, <NUM>),
wherein
(a) the second axis is obliquely angled relative to the first axis; or
(b) wherein the first axis and the second axis are noncollinear;
wherein the reamer system comprises a reamer coupler (<NUM>, <NUM>, <NUM>, <NUM>), wherein the reamer head (<NUM>, <NUM>, <NUM>, <NUM>) is rotationally coupled to the reamer coupler, wherein the reamer coupler is rotationally coupled to the offset drive shaft (<NUM>, <NUM>, <NUM>);
wherein the reamer system comprises a handle assembly,
wherein the handle assembly comprises a working tip (<NUM>, <NUM>), a handle shaft (<NUM>, <NUM>) coupled to the working tip, and a handle (<NUM>, <NUM>) coupled to the handle shaft opposite the working tip, wherein the working tip carries the reamer head (<NUM>, <NUM>) and the reamer coupler (<NUM>, <NUM>), wherein the reamer head and the reamer coupler rotate freely relative to the working tip about the first axis (<NUM>, <NUM>, <NUM>, <NUM>);
characterized in that a working portion, comprising the working tip (<NUM>, <NUM>), the reamer head (<NUM>, <NUM>, <NUM>, <NUM>) and the reamer coupler (<NUM>, <NUM>) has a thinnest profile along the first axis (<NUM>, <NUM>, <NUM>, <NUM>).