Field of the Invention

[0001] The present invention relates to methods and devices for creating a patient-specific (i.e., patient-matched) bone graft that can be used to reconstruct a glenoid deformity surgically, and in particular an in vivo or ex vivo surgical guide for reverse total shoulder arthroplasty.

[0002] The current state of the art for managing glenoid bone defects and/or erosion in the setting of reverse total shoulder arthroplasty (RSA) involves the use of either metallic augments or bone grafting techniques.

[0003] Patient-matched metallic glenoid augments can be created using a preoperative computer tomography (CT) scan, and the glenoid baseplate combined with the custom metal augment is then manufactured for intraoperative use. However, this process is costly, time intensive and laborious. In addition, this method does not restore glenoid bone stock. The CT scans may be limited or of inadequate quality to allow creation of a custom implant, particularly in the revision setting.

[0004] The use of metallic glenoid augments requires that the glenoid be prepared with custom instrumentation to fit a standard-sized, wedge-shaped implant. Such wedged implants typically have a slope in the range of 15 to 30 degrees and are not considered ‘patient-matched’ and are therefore considered a generic ‘one size fits all’ solution to the problem. Disadvantages of this method is that severe or large glenoid defects cannot be reconstructed. Furthermore, similar to patient-matched metallic implants, bone stock in the glenoid vault is not restored by this method. [0005] The advantages of using bone graft are multiple, but one principal advantage is that the graft allows the surgeon to rebuild/reconstitute glenoid bone stock for future operations (i.e., revision cases) if required. The currently accepted method for glenoid bone grafting is BIO-RSA™ (bony-increased offset - RSA, Tomier/Stryker). Three- dimensional computer tomography (3D CT) based planning software allows the user to create a digital version of the bone graft that is required to address the glenoid deformity in the operating room. However, there is currently no reliable or reproducible method that permits surgeons to recreate the exact dimensions of the graft intraoperatively (i.e., replicate the preoperative 3D plan). Typically, the graft is shaped freehand by the surgeon with a bone saw or other hand-held surgical instruments.

[0006] Freehand bone graft creation is imprecise and is also cumbersome and timeconsuming. Once the graft is successfully created, the graft is placed over the central post of a glenoid baseplate, which is then implanted into the glenoid. Screws are inserted through the periphery of the baseplate and bone graft to compress and stabilize the combined construct (i.e., baseplate and bone graft) into the native glenoid. The current process does not consistently allow the axis of glenoid preparation to be the same as the axis for implantation. Because the bone graft does not accurately represent the preoperative 3D plan with respect to its size/shape/orientation, and the axis used for glenoid preparation does not match, the graft does not fit well and is compressed unevenly. This can lead to incomplete implant seating and support as well as graft fracture and/or extrusion. Furthermore, the joint line is often excessively lateralized during this process resulting in excessive soft-tissue tension and difficulty in joint reduction which subsequently increases the risk of intraoperative and/or postoperative fracture. [0007] There is a need in the art for improvements to surgical devices and methods which may mitigate these and other difficulties in the prior art.

[0008] This background information is provided simply to facilitate understanding of the invention described herein, and is not an admission that any particular art is relevant prior art.

Summary of the Invention

[0009] In general terms, the invention comprises methods and systems for performing reverse total shoulder arthroplasty. Embodiments of the invention allow a surgeon to create a bone graft to an exact specification, which will match the preoperative plan that has been made. Embodiments of the invention allow the axis of preparation and axis of implantation to be the same, simplifying the process of inserting the graft. After the prepared graft is implanted, it will be loaded evenly under the glenoid baseplate. The surgeon can choose to lateralize the joint line or not, and create the graft (i.e., dimensions/shape) which corresponds to this choice.

[0010] Thus, in one aspect, the invention may comprise a method of creating a patientspecific bone graft using a surgical guide for preparing the bone graft during RS A. The desired bone graft comprises a trapezoidal or wedge shape, and thus has a lower flat surface and a wedge surface. In preferred embodiments, the bone graft comprises a step and wedge shape, which adds a step element to the base of the graft.

[0011] Thus, in one aspect, disclosed is a bone graft cutting guide for creating a custom bone graft having pre-determined shape and dimensions in reverse shoulder arthroplasty, comprising a:

(a) a first cutting guide surface for creating a first bone graft planar surface; (b) a second cutting guide surface for creating a second bone graft planar surface, which is non-parallel to the first bone graft planar surface; wherein the cutting guide surfaces are implemented in an adjustable external guide apparatus, a non- adjustable ex vivo guide, or at least two non- adjustable in vivo guide elements.

[0012] Therefore, in some embodiments, the guide comprises:

(a) a graft holder, a bottom surface of which corresponds to the lower flat surface of the graft;

(b) an upper plane surface, parallel to the bottom surface, which corresponds to the step surface, and

(c) an inclined plane surface which corresponds to the wedge surface.

[0013] In some embodiments, the guide may either be a non-adjustable or monolithic element which may be formed by an additive manufacturing process, such as 3D printing. In alternative embodiments, the guide may comprise an adjustable mechanical device.

[0014] In some embodiments, the guide may comprise two or more elements configured to be used in vivo by attachment to graft stock. The guide elements may be formed by an additive manufacturing process, such as 3D printing.

[0015] In another aspect, the invention comprises a method of using an external or internal guide, as described herein, to prepare a bone graft having a pre-determined shape and predetermined dimensions. The method may comprise the steps of:

(a) designing a bone graft having predetermined dimensions and shape; (b) producing the bone graft by cuting graft stock along guide surfaces presented by a guide which has been manufactured or adjusted to achieve the predetermined dimensions and angles.

Brief Description of the Drawings

[0016] In the drawings shown in the specification, like elements may be assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention.

[0017] Fig. 1 shows a step and wedge bone graft which may be produced by the devices and methods described herein.

[0018] Fig. 2A shows a non-adjustable monolithic guide for ex vivo use. Fig. 2B shows schematically the insertion of bone stock and the biplanar and non-parallel cuting planes designed specifically to create a ‘step and wedge’ shaped bone graft. Fig. 2C shows an alternative configuration of the guide designed to create a ‘trapezoidal’ shape bone graft.

[0019] Fig. 3A shows a non-adjustable monolithic guide for in vivo use, positioned on the humeral head. Fig. 3B shows a second guide for in vivo use, creating a second plane of a biplanar bone graft.

[0020] Fig. 4 shows a trapezoidal bone graft positioned over the central post of a glenoid base plate, with an insertion tool.

[0021] Fig. 5 A shows an embodiment of an adjustable guide apparatus. Fig. 5B shows the embodiment of Fig. 5 A and the creation of a second cut plane. [0022] Figs. 6A and 6B shows preoperative graft planning images including the graft angle and dimension.

[0023] Fig. 7 shows a mock-up of a bone graft and glenosphere in position after installation.

Detailed Description of Embodiments

[0024] The following describes exemplary embodiments of the invention and is not intended to limit the scope of the claimed invention.

[0025] As used herein, all technical terms have their commonly accepted meaning in the art of orthopaedic surgery. The guides and methods described herein are configured for use to create bone grafts of cancellous or corticocancellous bone tissue, and are not suitable for use with other tissue grafts such as osteochondral grafts.

[0026] The reverse shoulder arthroplasty (RSA) procedure and the anatomy of a shoulder joint described herein are well known to an orthopaedic surgeon skilled in the art. The bone graft is used to support and align the glenoid baseplate which thereby aligns the glenosphere. Disclosed herein are physical guides to produce a bone graft having a predetermined shape and pre-determined dimensions. The method of using the guide includes the steps of preoperative graft planning (producing a "virtual graft"), manufacturing a custom cutting guide or determining the settings for an adjustable cutting guide, and cutting the graft to shape.

[0027] In preferred embodiments, the bone graft 10 comprises a bi-planar step and wedge shape, as illustrated in Fig. 1. The bone graft has a base surface 12, an upper step surface 14 which is parallel to the base surface 12, and a wedge surface 16 which is in a plane non-parallel to the base surface. A transverse cross-section close to the base surface 12 will preferably be substantially cylindrical.

[0028] This biplanar graft is preferred because it allows a specific amount of lateralization, reconstructs the glenoid bone toss (in any location), and contributes to the stability of the graft prior to final insertion of the baseplate. In alternative embodiments, the bone graft may have a trapezoidal shape, again with a base surface and a wedge surface, but without a step portion.

[0029] Bone graft may be harvested from either the humeral head (autograft and allograft), the iliac crest (typically autograft), or another location of the surgeon's choosing.

[0030] The surgical guides provided herein guide a cutting tool to precisely cut the bone graft to pre-determined dimensions and angles, which are specific to a patient's anatomy, as determined by a preoperative planning process. Once the dimensions of the patientspecific bone graft are defined as part of the preoperative planning phase, for example by using commercially available software to create a ‘digital graft’ or 'virtual graft', the graft may be prepared with one of the guides described herein.

[0031] Therefore, in some embodiments, the guide 1 comprises:

(a) graft holder 12, a bottom surface of which corresponds to the base surface of the graft;

(b) an upper plane surface 22, parallel to the bottom surface, which corresponds to the step surface, and

(c) an inclined plane surface 24 which corresponds to the wedge surface. [0032] In some embodiments, the guide 1 may be a non- adjustable or monolithic guide which may be formed by an additive manufacturing process, such as 3D printing. As exemplified in Fig. 2A, the guide may comprise a holder and upper guide surfaces which exactly replicates the shape and dimensions of the graft that was determined during the preoperative planning phase. The virtual graft may be used to design the guide as a 3D model, which can then be used to produce the guide. The cutting guide is then 3D-printed using a biocompatible material that is validated for sterilization and approved for surgical use.

[0033] As shown in Fig. 2B, a cylinder of bone 2 is harvested from the humeral head or alternate location of surgeon’s choice, which is then recessed and fully seated within the graft holder 12 of cutting guide 1. A first cut with a saw S to remove the excess bone is made along the guide step plane 22 to create the step surface, and then a second cut is made along the guide inclined plane 24 to create the wedge surface. The desired bone graft 10 is that portion remaining within the guide 1.

[0034] An alternative embodiment is exemplified in Fig. 2C, which would result in a trapezoidal-shaped bone graft, without a step portion.

[0035] Thus, because the guide 1 was made to specific pre-determined patient-specific dimensions, the resulting bone graft will be shaped and sized as determined in the planning stage.

[0036] In some embodiments, the guide may comprise two or more elements configured to be used in vivo by attachment to graft stock. In some embodiments, at least two singleuse patient-specific 3D-printed cutting guide elements are developed to create sequential bone cuts of the proximal humerus. The minimum and maximum heights and angle are used from the preoperative plan to determine the cutting plane(s) to create the desired graft. A first guide element 3 fits exactly on the intended graft source with a guide surface positioned to produce a graft of desired pre-determined dimension. The guide element 3 is held in place, partly because of its exact fit over the surface of the humeral head and surrounding osteophytes, and also as it is temporarily held in place with Kirschner wires 32, which are inserted through guide holes formed in the guide element 3. The guide element 3 comprises a guide surface, such as integrally formed slot 34, to guide a first cut, as shown in Fig. 3 A. The slot 34 then guides the saw blade S. The resulting cut produces a planar surface 36 on the humeral head, as may be seen in Fig. 3B, which surface 36 will be either the base surface or the wedge surface of the resulting graft.

[0037] The first guide element 3 is then removed, and a second guide element 4 is then positioned and affixed in place with Kirschner wires 42. The second guide element 4 also comprises a guide surface, such as an integral slot 44 which guides a saw S along a plane which is not parallel to the plane of the first cut. After the second cut, a trapezoidal bone graft 10 is produced.

[0038] The guide elements may be formed by an additive manufacturing process, such as 3D printing from a virtual model, to produce guide elements precisely shaped to fit the patient's anatomy and to produce a bone graft of pre-determined shape and pre-determined dimensions. The material must comprise a biocompatible material that is validated for sterilization and approved for surgical use. The slot for guiding a saw blade is preferably lined with an abrasion-resistant material, such as titanium or a carbide, to avoid damage during the sawing portion of the operation.

[0039] As shown in Fig. 4, the bone graft 10 may then be positioned over the central post 52 of the glenoid base plate 50, ready to be inserted into the glenoid with an insertion handle 54. [0040] As may be appreciated by one skilled in the art, successive guide elements may be designed and used to create a bone graft with different planes and surfaces. A minimum of two guide elements are required to create a trapezoidal shape, while three guide elements may be used to create a preferred step and wedge shape. Each guide element will have the guide slot positioned in a desired location and angle to create the necessary cutting plane.

[0041] In some embodiments, the guide may comprise an adjustable external cutting guide 60, comprising:

(a) a base 62 supporting a central housing having a graft holding platform 64 and four upright comer posts 66, each comer post comprising at least one lock nut 68 which may be moved vertically along the comer post, and

(b) an adjustable top plate 70 for guiding a saw, having a central opening through which the central housing may pass, and comer openings through which the comer posts may pass.

The adjustable top plate 70 rests on and is positioned by the lock nuts 68 to create cutting planes at a desired angle and displacement. Each opening may be elongated to permit the top plate to tilt by pivoting about at least one horizontal axis as may be seen in Figs. 5 A and 5B, where the top plate 70 is inclined from front to back. Side-to-side inclination is also possible to create another cut plane if desired.

[0042] The graft holding platform within the central housing 64 is vertically moveable to create the desired depth of the bone graft.

[0043] Similar to the non- adjustable external cutting guide, a cylinder of bone 2 is positioned on the graft holding platform within the central housing 64. The first cutting plane is provided by the upper surface 65 of the central housing, which is positioned to create the cut that will provide the depth position to create the step surface. The second cutting plane is provided by the top plate 70, as may be seen in Fig. 5B.

[0044] In some embodiments, the comer posts 66 may be externally threaded while each lock nut 68 has a complementary internal thread. Thus, each lock nut may be positioned vertically by simply rotating the nut. In other embodiments, the lock nut may simply slide along the comer post and have a clamping mechanism (such as a cam lock) to releasably clamp against the comer post in a desired position. Alternative mechanisms of adjusting and securing the position of the graft holding platform and top plate/cutting surface 70 may be contemplated.

[0045] In preferred embodiments, the parts are assembled from the base 62. The center- bore/housing 64 is threaded into the base. The comer posts 66 are also threaded into the base. In preferred embodiments, the parts of the guide can be detached for convenient and effective sterilization.

[0046] During preoperative planning, the shape and dimensions of the bone graft are determined. The external adjustable guide provides an adjustable graft holding platform that is threaded into the central housing and permits adjustment to a pre-planned depth. Lower lock nuts are placed onto the comer posts at pre-planned heights, which positions the top plate at a precise angle. The top-plate is laid over/through the posts and rests on these four nuts. At this stage, the top-plate is inclined (and can be inclined in two different planes). Upper lock nuts are then placed on top of the top plate to secure it at the desired height.

[0047] In some embodiments, the preoperative planning step may use commercially available ‘surgeon controlled’ 3D planning software, such as Blueprint™ (Stryker), to plan a patient-specific bone graft. The patient’s CT scan is loaded into Blueprint™ and a desired system for the intended procedure is selected (Fig. 6A). The preparation axis is left at zero degrees of ante/retroversion (Fig. 6A), and superior/inferior inclination (Fig. 6B). The glenoid component is positioned appropriately into the glenoid vault. ‘Patientspecific bone graft’ is selected within the planning software and the graft (i.e., ‘digital graft’ or 'virtual graft') is generated including the exact dimensions of the graft (Figs. 6 A and 6B).

[0048] The shape and dimensions of the digital graft may then be used to design a custom bone graft guide which may then be manufactured for either ex vivo or in vivo use, as described above. Alternatively, the desired device settings for an adjustable device 60 may be easily determined from the dimensions of the digital graft. The required depth of the graft and desired amount of lateralization is shown on the digital graft from the preoperative plan. The angle of the slope on the graft is also known, as are the dimensions of the device itself. Therefore, the required heights of the four comer lock nuts to produce the desired incline of the top plate can be determined preoperatively.

[0049] It will be apparent to one skilled in the art that preparation and insertion axes will be identical. During RSA a guide pin is placed into the glenoid. This pin determines the final location and orientation of the glenoid baseplate (Fig. 7). During conventional RSA using BIO-RSA and/or angled BIO-RSA methods, the pin axes used for glenoid preparation and for bone grafting are not always the same. The guide described herein resolves this issue and should result in more even loading of the graft.

Definitions and Interpretation

[0050] Aspects of the present invention may be described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

[0051] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. [0052] The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims appended to this specification are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

[0053] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

[0054] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[0055] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and/or" means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase "one or more" is readily understood by one of skill in the art, particularly when read in context of its usage.

REFERENCES

[0056] The following references are indicative of the level of skill in the art and are incorporated herein by reference as if fully reproduced herein (where permitted).

• Boileau, P. et al. "Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation". Clin Orthop Relat Res (2011)

• Boileau, P. et al. “Angled BIO-RSA (bony-increased offset-reverse shoulder arthroplasty): a solution for the management of glenoid bone loss and erosion”. J. Shoulder Elbow Surg (2017)

• United States Patent Application 20170273795A1

• United States Patent Application 20200188121A1