FIELD

The present disclosure relates generally to annular cutting tools, and more particularly to an annular cutting tool designed to resect a bone graft with improved durability, cutting performance, and/or reduced heat generation during use, as well as methods of resecting bone grafts using such annular cutting tools.

BACKGROUND

During the lifetime of a patient, it may be necessary to perform a total shoulder replacement procedure on the patient, for example, as a result of disease or trauma. In a total shoulder replacement procedure, a humeral prosthesis is used to replace the natural head of the patient's humerus. The humeral prosthesis typically includes an elongated post component that is implanted into the intramedullary canal of the patient's humerus and a hemispherically-shaped prosthetic head component that is secured to the post component. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is typically resurfaced or otherwise replaced with a glenoid component that provides a bearing surface upon which the prosthetic head component of the humeral prosthesis articulates.

However, in some cases the patient's natural shoulder, including its soft tissue, has degenerated to a severe degree of joint instability and pain. In many such cases, it can be necessary to change the mechanics of the shoulder. Reverse shoulder implants can be used to do so. As its name suggests, a reverse shoulder implant reverses the anatomy, or structure, of the healthy shoulder. In particular, a reverse shoulder implant is designed such that the prosthetic head (i.e., the “ball” in the ball-and-socket joint), known as a glenosphere component, among other names, is secured to the patient's scapula, with the corresponding concave bearing (i.e., the “socket” in the ball-and-socket joint), known as a humeral cup, among other names, being secured to the patient's humerus. Such a reverse configuration allows the patient's deltoid muscle, which is one of the larger and stronger shoulder muscles, to raise the arm.

To secure the glenosphere component to the patient's scapula, a baseplate, sometimes referred to as a metaglene component, can be implanted onto the glenoid of the patient's scapula. For example, as shown inFIGS. 1A and 1B, a shoulder joint implant can comprise a metaglene component60that includes a platform62having a post64extending outwardly from its distal surface66. The post64can have a bore68formed about a central axis A-A of the metaglene component60and can be configured to engage a locking screw or other coupling element protruding from a distal surface of a glenosphere component (not shown). The bore68can extend through the entire length of the post64. The post64of the metaglene component60can be designed to be implanted into a void formed in a glenoid surface28. Bone screws80can be positioned in some or all of the screw holes or apertures74and driven into, or otherwise secured to, the bone tissue of a patient's scapula30, thereby fixing the metaglene component60in place.

In some patients, the glenoid may be severely eroded to an extent that the metaglene component60cannot be properly implanted. In such situations, surgeons may attach the metaglene component60to a bone graft that fills in the eroded space in the glenoid. The bone graft can be resected from an allograft or a part of the patient's body, such as, for example, the head of the humerus or portion of the femur. As shown inFIGS. 2A and 2B, an exemplary bone graft90for attachment to a metaglene component60can be shaped to have a generally cylindrical body having a proximal end92and a distal end94. The proximal end92can be reamed or otherwise shaped to facilitate attachment to the distal side of the metaglene component60. For example, the reamed proximal end92of the bone graft90can have a generally concave-shaped surface that mates with a generally convex-shaped distal surface66of the metaglene component60. Additionally, or alternatively, the reamed proximal end92of the bone graft can define a bore96that extends at least partially through the graft along a longitudinal axis A1-A1to receive the post64of the metaglene component60. A person skilled in the art will recognize other configurations that are possible.

Existing annular cutting tools for resecting bone grafts typically exhibit a lack of durability, inefficient cutting performance, and/or excessive heat generation. For example, conventional tools are typically configured with pyramid-shaped cutting teeth in a hole saw pattern. Pyramid-shaped cutting teeth limit the useful cutting edge of the tool and are prone to premature dulling. Conventional cutting tools also lack features to accumulate morselized bone debris away from the cutting teeth, resulting in bone debris being packed into the tooth geometry and limiting the advance of the saw, i.e., causing it to bind. For example, the operator may be required to make several approaches, such that the tool is withdrawn between approaches to clear the accumulated bone debris before a cut is complete. Some tools generate excessive heat due to frictional contact between the tool and bone that can be detrimental to the viability of the resected bone graft. Still further, existing designs are also prone to overheating, which can limit the length of time for which the tool can be used, among other undesirable results that occur due to a surgical tool overheating. The overheating results from a number of factors, including but not limited to the amount of pressure, contact area, and rotations necessary to achieve a desired resection.

Accordingly, there is a need for improved annular cutting tools having, for example, improved cutting geometry, debris removal features, and a design that limits the amount of heat generated by the tool in use, and related methods of resecting a bone graft using the various embodiments of an annular cutting tool provided for herein, or otherwise derivable from the present disclosures.

SUMMARY

The present disclosure is generally related to annular cutting tools, and represents improvements over existing designs of such tools. Annular cutting tools are used in the medical field to resect a cylindrically-shaped bone graft, e.g., from a humeral head for attachment to a metaglene component in reverse shoulder procedures. However, existing designs for such conventional tools typically exhibit a lack of durability, inefficient cutting performance, and/or excessive heat generation.

As discussed in greater detail below, the provided for embodiments of an annular cutting tool, sometimes referred to as a reamer, can include an annular body having cutting teeth with an improved geometry. The improved geometry exists in various aspects of the tool, including but not limited to the design of the teeth, the design of the cutting body or head on which the teeth are disposed (often cylindrical in design), and the cannulated drill or drill bit disposed within a circumference of the cutting head, or perimeter defined by the shape of the cutting head. For example, with respect to the teeth, in some embodiments, each cutting tooth can include a flared distal tip that is substantially flat to provide a greater cutting surface and greater durability. Alternatively, or additionally, one or more gullets having an extended vertical depth can be disposed between groups of adjacent cutting teeth to facilitate removal of bone debris away from the cutting teeth and thus prevent or reduce binding of the tool during use. Alternatively, or additionally, the cutting body can have a recessed surface portion to reduce the area of direct contact to bone, thus decreasing the amount of frictional heat generated during use. The recessed surface portion can also provide an area in which bone debris can accumulate away from the cutting teeth to prevent, or further reduce, binding of the tool during use. The annular cutting body can also include a centrally-disposed drill bit (e.g., a cannulated drill bit) that can be inserted over a guide pin to align the tool with respect to a target bone in addition to drilling a hole in the bone graft, e.g., to receive a post of the metaglene component.

One exemplary embodiment of an annular cutting tool includes an annular cutting body, a plurality of cutting teeth, a drill bit, and a drive shaft. The annular cutting body has a proximal end, a distal end, and a central portion disposed between the proximal end and the distal end. Further, a central longitudinal axis of the annular cutting body extends from the proximal end to the distal end. The plurality of cutting teeth are disposed at the distal end of the annular cutting body, the teeth extending radially outward beyond the central portion of the annular cutting body with respect to the central longitudinal axis such that the central portion includes a recessed surface area. The drill bit extends distally from the proximal end of the annular cutting body, along the central longitudinal axis. The drive shaft extends proximally from the proximal end of the annular cutting body and is coaxial with the central longitudinal axis of the annular cutting body. In some embodiments, the drill bit can be a cannulated drill bit.

One or more teeth of the plurality of cutting teeth can have a substantially flat distal tip. In some embodiments, the plurality of cutting teeth can extend radially inward from the central portion of the annular cutting body. One or more extended gullets can be located in the central portion of the annular cutting body. Each extended gullet of the one or more extended gullets can be disposed between adjacent teeth of the plurality of cutting teeth, and the one or more extended gullets can have more than one tooth of the plurality of cutting teeth disposed between an adjacent gullet when more than one extended gullet is located in the central portion of the annular cutting body.

The annular cutting body can have one or more cleaning apertures located in the central portion, with such apertures being configured to allow bone debris to pass through the aperture(s). In some such embodiments, at least one cleaning aperture can include a distal terminal end that has an inverted V-shape. An annular protrusion can be disposed at the proximal end of the annular cutting body, which allows the recessed surface area to be bounded by a proximal end of the plurality of cutting teeth and the annular protrusion. One or more blades can be transversely disposed at the proximal end of the annular cutting body.

The drill bit can have a distal cutting tip that includes a plurality of planer cutting surfaces. Some such embodiments can have an interior angle between one or more pairs of the plurality of planer cutting surfaces that is approximately 120 degrees.

The annular cutting body, the drill bit, and the drive shaft can be manufactured as a single unitary body.

Another exemplary embodiment of an annular cutting tool also includes an annular cutting body, a plurality of cutting teeth, a drill bit, and a drive shaft. The annular cutting body has a proximal end and a distal end, with a central longitudinal axis of the annular cutting body extending from the proximal end to the distal end. The plurality of cutting teeth are disposed at the distal end of the annular cutting body. One or more teeth of the plurality of teeth have a flared and substantially flat distal tip. The drill bit extends distally from the proximal end of the annular cutting body, along the central longitudinal axis. The drive shaft extends proximally from the proximal end of the annular cutting body and is coaxial with the central longitudinal axis of the annular cutting body. In some embodiments, the drill bit can be a cannulated drill bit.

In some embodiments, the plurality of cutting teeth can extend radially inward from the annular cutting body. One or more extended gullets can be located in the annular cutting body. Each extended gullet of the one or more extended gullets can be disposed between adjacent teeth of the plurality of cutting teeth, and the one or more extended gullets can have more than one tooth of the plurality of cutting teeth disposed between an adjacent gullet when more than one extended gullet is located in the annular cutting body.

The annular cutting body can have one or more cleaning apertures located in the annular cutting body, with such apertures being configured to allow bone debris to pass through the aperture(s). In some such embodiments, at least one cleaning aperture can include a distal terminal end that has an inverted V-shape. An annular protrusion can be disposed at the proximal end of the annular cutting body such that a recessed surface area of the annular cutting body is bounded by a proximal end of the plurality of cutting teeth and the annular protrusion. One or more blades can be transversely disposed at the proximal end of the annular cutting body.

The drill bit can have a distal cutting tip that includes a plurality of planer cutting surfaces. Some such embodiments can have an interior angle between one or more pairs of the plurality of planer cutting surfaces that is approximately 120 degrees.

The annular cutting body, the drill bit, and the drive shaft can be manufactured as a single unitary body.

One exemplary method of resecting a bone graft includes positioning an annular cutting tool with respect to a bone. The annular cutting tool has a drill bit and an annular cutting body that is disposed circumferentially around at least a portion of the drill bit. Further, the annular cutting body has a plurality of cutting teeth disposed at a distal end of the body. The method further includes applying a torque to the annular cutting tool to cause the plurality of cutting teeth to rotate about a longitudinal axis of the cutting tool. The method further includes distally advancing the annular cutting tool into the bone while the torque is being applied to cause the plurality of cutting teeth to contact and cut the bone, thereby defining a bone graft. During distal advancement, a portion of the annular cutting body directly proximal to the plurality of cutting teeth does not contact the bone from which the bone graft is being removed. Further, distally advancing the annular cutting tool into the bone while the torque is being applied causes the drill bit to ream a hole in the defined bone graft.

The annular cutting tool can be configured in a manner similar to described above with respect to various exemplary embodiments, or as otherwise provided for throughout the present disclosure. For example, the drill bit can be cannulated. In such embodiments, positioning the annular cutting body can include distally inserting the cannulate drill bit over a guide pin that extends from the bone. By way of further non-limiting example, the plurality of cutting teeth can extend radially outward beyond a central portion of the annular cutting body with respect to the central longitudinal axis of the cutting tool, thereby defining a recessed surface area on the central portion, proximal to the plurality of cutting teeth. In some such embodiments, one or more teeth of the plurality of cutting teeth can have a substantially flat distal tip.

Portions of the bone that are cut can pass through one or more cleaning apertures located on the annular cutting body. In some embodiments, distally advancing the annular cutting tool into bone while the toque is being applied can further cause one or more blades of the annular cutting tool disposed proximal of the plurality of cutting teeth to shape a proximal surface of the bone graft. The methods provided for herein can also include additional steps that are included as part of a resection procedure, such as using resection guides and oscillating saws to form and remove the graft, as provided for in greater detail below. Distally advancing the annular cutting tool can result in formation of the bone graft in a single distal advancement of the annular cutting tool, without having to pull back the annular cutting tool.

