# Patent

## Title
Patient-specific guide for partial acetabular socket replacement

## Abstract

A device for partial acetabular replacement includes a patient-specific acetabular guide. The acetabular guide has a first surface configured to nestingly mate in only one position to the patient's acetabulum. The acetabular guide includes a patient-specific guiding formation configured to guide a cutting tool to remove damaged tissue from a defect of the patient's acetabulum and prepare a patient-specific implantation slot corresponding to the defect after removal of the damaged tissue. A patient-specific partial acetabular implant can be configured to nestingly mate with the patient-specific implantation slot.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part application of U.S. patent application Ser. No. 12/893,306, filed Sep. 29, 2010. The entire disclosure of the above application is incorporated herein by reference.


INTRODUCTION
The present teachings provide a patient-specific guide and an associated implant and methods for preparing the acetabulum to receive a partial acetabular socket replacement. The patient-specific guide and implant are prepared preoperatively for the specific patient based on medical scans of the relevant anatomy of the patient.
SUMMARY
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
The present teachings provide a device for partial acetabular replacement that includes a patient-specific acetabular guide. The acetabular guide has a first surface configured to nestingly mate in only one position to the patient's acetabulum. The acetabular guide includes a patient-specific guiding formation configured to guide a cutting tool to remove damaged tissue from a defect of the patient's acetabulum and prepare a patient-specific implantation slot corresponding to the defect after removal of the damaged tissue. In some embodiments, a patient-specific partial acetabular implant can be configured to nestingly mate with the patient-specific implantation slot.
The present teachings also provide a method for a partial socket replacement. The method includes mounting a patient-specific acetabular guide on an acetabulum of a patient and guiding a cutting tool through a patient-specific bore of the acetabular guide. The acetabular guide is configured to mate to the patient's acetabulum in only one position and the patient-specific bore of the acetabular guide is configured to overlay a defect in the acetabulum of the patient. The method includes removing damaged tissue of the defect, and forming a patient-specific implantation slot by removing the damaged tissue. A patient-specific partial acetabular implant can be configured to nestingly mate with the patient-specific implantation slot.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.



DRAWINGS
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
FIG. 1 is an exploded environmental perspective view of a patient-specific guide according to the present teachings;
FIG. 2 is another exploded environmental perspective view of the patient-specific guide of FIG. 1;
FIG. 3 is an environmental perspective view of the patient-specific guide of FIG. 1;
FIG. 4 is an environmental sectional view of the patient-specific guide of FIG. 1;
FIG. 4A is an environmental sectional view of a patient-specific guide according to the present teachings;
FIG. 5 is an exploded environmental view of an implant according to the present teachings;
FIG. 6 is an environmental view of the implant of FIG. 5;
FIG. 7 is an environmental view of an inverse patient-specific guide showing how to make a patient-specific allograft implant from allograft tissue according to the present teachings;
FIG. 7A is a patient-specific implant made from allograft tissue using the inverse patient-specific guide of FIG. 7; and
FIGS. 7B-7D are snapshot diagrams of extracting the allograft implant of FIG. 7A using the inverse patient-specific guide of FIG. 7.



Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
DETAILED DESCRIPTION
Exemplary embodiments will now be described more fully with reference to the accompanying drawings.
The present teachings generally provide a patient-specific (custom) guide, and associated implant and method for partial arthroplasty, including partial acetabular socket replacement, partial glenoid socket replacement or other similar procedure. More specifically, the present teachings provide a patient-specific guide for the acetabulum of the patient, when the acetabulum includes a defect that can be corrected by a partial socket replacement or a partial implant.
Generally, patient-specific devices can be designed preoperatively using computer-assisted image methods based on three- or two-dimensional images of the patient's knee anatomy reconstructed from MRI, CT, ultrasound, X-ray, or other three- or two-dimensional medical scans of the patient's anatomy and in some cases complemented with digital photography methods and/or anthropometry databases. Various CAD programs and/or software can be utilized for three-dimensional image reconstruction, such as, for example, software commercially available by Materialise USA, Plymouth, Mich.
Various alignment guides and pre-operative planning procedures are disclosed in commonly assigned and co-pending U.S. patent application Ser. No. 11/756,057, filed on May 31, 2007, U.S. patent application Ser. No. 12/211,407, filed Sep. 16, 2008; U.S. patent application Ser. No. 11/971,390, filed on Jan. 9, 2008, U.S. patent application Ser. No. 11/363,548, filed on Feb. 27, 2006; U.S. patent application Ser. No. 12/025,414, filed Feb. 4, 2008, U.S. patent application Ser. No. 12/571,969, filed Oct. 1, 2009, and U.S. patent application Ser. No. 12/955,361, filed Nov. 29, 2010. The disclosures of the above applications are incorporated herein by reference.
In the preoperative planning stage for a partial socket replacement, imaging data of the relevant anatomy of a patient can be obtained at a medical facility or doctor's office, using one of medical imaging methods described above. The imaging data can include, for example, various medical scans of a relevant joint portion or other relevant portion of the patient's anatomy, as needed for joint modeling and, optionally, for implant alignment axis determination or for other alignment purposes. The imaging data thus obtained and other associated information can be used to construct a three-dimensional computer image of the joint or other portion of the anatomy of the patient.
According to the present teachings, the patient-specific guides and implants are generally configured to match the anatomy of a specific patient and are generally formed using computer modeling based on the patient's reconstructed three-dimensional anatomic image. The patient-specific guides have an engagement surface that is made to conformingly contact and match a three-dimensional image/model of the patient's bone surface (with or without cartilage or other soft tissue), by the computer methods discussed above. In this respect, a patient-specific guide can nestingly mate with the corresponding bone surface (with or without articular cartilage) of the specific patient in only one position.
According to the present teachings, the patient-specific guide can include a custom-made (patient-specific) guiding formation, such as, for example, a guiding bore for guiding a joint preparation tool, such as a reamer, cutter, broach, mill, drill or other cutting tool, according to the pre-operative plan for the patient. In some embodiments, the guiding formation can have a patient-specific size and shape configured during the preoperative plan for the patient to guide a milling tool, a reamer, a broach or other cutting tool, as discussed below. The preoperative plan can include planning for bone or joint preparation, including extent and area for defect removal, by milling, reaming, broaching or other cutting method, as well as implant selection and fitting.
The patient-specific guide described herein can be manufactured by various stereolithography methods, selective laser sintering, fused deposition modeling or other rapid prototyping methods. The patient-specific guide can be made of any biocompatible material, including metal, metal alloys or plastic. Generally, the patient-specific guide is disposable and made of lightweight materials, including polymers. The patient-specific implant can be made of any biocompatible materials, including metals and alloys. The patient-specific guide, implant and associated tools can be sterilized and shipped to the surgeon or medical facility in a kit for a specific patient and surgeon for use during the surgical procedure.
Referring to FIGS. 1-6, a patient-specific acetabular guide 100 for preparing an acetabulum to receive a partial acetabular implant 300 (partial acetabular socket replacement) is illustrated. As shown in FIG. 1, the acetabulum of the pelvis of the patient includes an articular cartilage 84 and an acetabular fossa 83 in the acetabulum or acetabular socket 80. A representative defect, such as damaged cartilage, is illustrated at 82. The patient-specific acetabular guide 100 is designed during the preoperative plan of the patient for the specific patient. The patient-specific acetabular guide 100 is configured to guide a cutting tool 200 to mill, burr or otherwise remove the damaged tissue of the defect 82 and prepare the acetabulum 80 for receiving a partial acetabular implant 300. The cutting tool 200 can include a handle 202 and a cutting portion or cutting shaft 204, as shown in FIGS. 1 and 2. The partial acetabular implant 300, shown in FIGS. 5 and 6, is also designed during the preoperative plan in coordination with the patient-specific acetabular guide 100. As described below, the partial acetabular implant is also patient-specific, although non custom implants can be used, if desired, by selecting an appropriate size and shape from a non-custom database during the preoperative planning stage.
With continued reference to FIGS. 1-4, the acetabular guide 100 can be formed as a shell having a curved three-dimensional surface 102 (or first surface 102) and bounded by an opposite substantially planar second surface 104. The first surface 102 is patient-specific and designed to nestingly mate with the patient's acetabulum 80, including the articular cartilage 84 and the acetabular fossa 83 only in one position, as shown in FIGS. 3 and 4. In this regard, the patient's acetabulum 80 provides reference landmarks, including, for example, the transition or boundary between the articular cartilage 84 and the acetabular fossa 83 of the specific patient. The acetabular guide 100 includes a patient-specific guiding formation 106 in the form of a through slot or bore that extends between first and second openings 108 and 110 on the first and second surfaces 102, 104 of the acetabular guide 100, as shown in FIG. 4. In some embodiments, the second surface 104 may be omitted such that the acetabular guide 100 is in the form of an open shell and the first opening 108 is the only opening of the guiding formation 106.
The guiding formation 106 is designed during the preoperative plan such that when the acetabular guide 100 can be seated in a unique position in the acetabulum 80 of the patient, the guiding formation 106 can provide a guiding surface for guiding the cutting portion 204 of the cutting tool 200 to remove the damaged cartilage associated with the defect 82. Accordingly, the patient-specific acetabular guide 100 and guiding formation 106 stabilize and guide the cutting tool 200 intraoperatively, enabling the surgeon to remove the damaged tissue associated with the defect 82 and/or other surrounding or underlying tissue in a conservative manner, as determined according to the preoperative plan with the approval of the surgeon. In this regard, the procedure can minimize tissue removal and conserve healthy patient tissue.
Referring to FIG. 4A, another embodiment of the acetabular guide 100A with a depth stop or depth control feature is illustrated. The acetabular guide 100A is in other respects similar to the acetabular guide 100, and the description of features common to those of the acetabular guide 100 is not repeated. The depth control feature of the acetabular guide 100A can be, for example, a three dimensional depth control surface 103 extending from the planar second surface 104 of the acetabular guide 100A. The depth control surface 103 is configured to mate with a corresponding outer surface 203 of a distal portion 201 of a handle 202 of a cutting tool 200A, similar in other respects to the cutting tool 200, as shown in FIG. 4A. The position and location of the depth control surface 103 relative to the acetabular guide 100A is determined during the preoperative plan for the patient such that when the outer surface 203 of the handle 202 abuts the depth control surface 103, defect removal and/or cutting by the cutting tool 200A does not exceed a predetermined cutting depth.
Using the cutting tool 200 (or 200A) and acetabular guide 100 (Or 100A), an implant-receiving site 86 is cut, milled or otherwise prepared in the acetabulum 80 of the patient for receiving the partial acetabular implant 300, as shown in FIGS. 5 and 6. The implant-receiving site can be a blind bore formed by removing the defect 82 and having a patient-specific wall 88 that is substantially an envelope of removed defect 82. The acetabular implant 300 can be patient-specific and include a peripheral wall 304 configured to engage the wall 88 of the implant-receiving site or slot 86. The partial acetabular implant 300 includes an outer (articulating) surface 302 configured to continuously transition to the health portion of the articular cartilage 84, replace the damaged cartilage 82 (FIG. 1) and re-create a patient-specific continuous articular cartilage surface without a defect. The partial acetabular implant 300 can include one or more anchoring elements 306, such as pegs, keels, pins or other protrusions, extending from the acetabular implant opposite to the outer surface 302 for anchoring the implant into the acetabulum 80.
It should be appreciated that the wall 88 of the patient-specific implant-receiving site 86 and the peripheral wall 304 of the implant 300 can either follow and match the outline of the original defect 82 or can follow and match a de-burred or smoother envelope of the defect 82. The acetabular implant 300 can be made of any biocompatible material including, for example, pyrocarbon or cobalt chromium alloy with a polished outer surface 304 for articulation with the femoral head of the joint. Additionally, the acetabular implant can be made of allograft tissue, as discussed below in reference to FIGS. 7 and 7A.
Intraoperatively, the patient-specific acetabular guide 100 is mounted on the patient's acetabulum 80 in a unique position determined by the patient's acetabular geometry, which is referenced by the first surface 102 of the acetabular guide, as shown in FIGS. 3 and 4. By design, during the preoperative plan of the patient, the patient-specific guiding formation 106 is configured to be aligned with and overlay the defect 82 when the acetabular guide 100 is seated on the acetabulum. A cutting tool 200 can be guided by the guiding formation 106 to remove the damaged tissue of the defect 82 and create the implantation site 86 for implanting the partial acetabular implant 300. The acetabular implant 300 is then inserted into the implantation site 86 and replaces the damaged tissue of the defect 82.
Example embodiments are provided so that this disclosure is thorough, and fully conveys the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure.
In some embodiments, the partial acetabular implant can be made of allograft tissue. An exemplary partial patient-specific allograft implant 300A (or allograft implant 300A, for short) is illustrated in FIG. 7A. Similarly to the partial acetabular implant 300 of FIG. 5, the allograft implant 300A has a peripheral wall 304 configured to engage the wall 88 of the implant-receiving site or slot 86. The allograft implant 300A includes an outer (articulating) surface 302 configured to continuously transition to the health portion of the articular cartilage 84, replace the damaged cartilage 82 (FIG. 1) and re-create a patient-specific continuous articular cartilage surface without a defect.
To extract a patient-specific allograft from allograft tissue, an “inverse” acetabular guide 400 can be used as a guide. The inverse acetabular guide 400 is configured during the preoperative plan of the patient for extracting wherein a patient-specific implant, i.e., the allograft implant 300A, from allograft tissue. The inverse acetabular guide 400 can be shell-like in shape with a curved surface 401 that engages an allograft tissue (such as a cadaveric acetabulum) 80A. An external protrusion 404 is defined by a curved guiding slot 402 through the inverse acetabular guide 400 and is connected to the acetabular guide through a neck portion 406. The guiding slot 402 and protrusion 404 are patient-specific and designed and configured during the preoperative plan for the patient to trace the shape and size of the peripheral wall 304 of the allograft implant 300A. The guiding slot 402 can guide the cutting tool 200 along the guiding slot 402 and around the protrusion 404, as shown in FIGS. 7 and 7A-7C, to cut the allograft portion for the allograft implant 300A having a peripheral wall 304, but still attached to the allograft issue 80A along an uncut portion corresponding to the neck portion 406 of the protrusion 404. The inverse acetabular guide 400 can then be removed and the allograft implant 300A can be separated from the allograft tissue by cutting through any remaining uncut portion.
It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Accordingly, individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

## Claims

1. A method for a partial socket replacement comprising:
mounting a patient-specific acetabular guide on an acetabulum of a patient, wherein the acetabular guide is configured to mate to the patient's acetabulum in only one position;
guiding a cutting tool through a patient-specific bore of the acetabular guide, wherein the patient-specific bore of the acetabular guide is configured to overlay a defect in the acetabulum of the patient;
removing damaged tissue of the defect;
forming a patient-specific implantation slot by removing the damaged tissue,
engaging a patient-specific inverse acetabular guide to allograft tissue;
guiding a cutting tool along a guiding slot of the patient-specific inverse acetabular guide, the guiding slot configured during the preoperative plan to mate with a wall of the patient-specific implantation slot; and
extracting a patient-specific partial acetabular implant from the allograft tissue; and
implanting the patient-specific partial acetabular implant in the patient-specific slot, wherein the implant is the allograft tissue implant.

2. The method of claim 1, wherein the partial acetabular implant has a peripheral surface configured to mate with a wall of the patient-specific implantation slot.

3. The method of claim 2, wherein the partial acetabular implant has an outer surface configured to be continuous with a surrounding cartilage after implantation.

4. The method of claim 1, further comprising anchoring the patient-specific partial acetabular implant in the acetabulum using an anchoring element.

5. The method of claim 1, wherein the acetabular guide has a first curved three-dimensional surface configured to nestingly mate in only one position to the patient's acetabulum, and a second planar surface opposite the first surface, and wherein the bore is an open bore extending between the first and second surfaces.

6. The method of claim 5, further comprising controlling a depth of the patient-specific implantation slot.

7. The method of claim 6, wherein controlling a depth of the patient-specific implantation slot includes engaging a three-dimensional depth control surface of the acetabular guide to a corresponding outer surface of a distal portion of a handle of the cutting tool.

8. The method of claim 7, wherein the depth control surface extends from the planar second surface of the acetabular guide.

9. A method for a partial socket replacement comprising:
mounting a patient-specific acetabular guide on an acetabulum of a patient, wherein the acetabular guide has a first curved three-dimensional surface configured to nestingly mate to the patient's acetabulum, including the acetabulum's articular cartilage and acetabular fossa in only one position;
guiding a cutting tool through a patient-specific bore of the acetabular guide, wherein the patient-specific bore passes through the first surface of the acetabular guide and is configured to overlay a defect in the acetabulum of the patient;
removing damaged tissue of the defect;
forming a patient-specific implantation slot; and
controlling a depth of the patient-specific implantation slot by the acetabular guide physically constraining the cutting tool from advancing further into the acetabulum.

10. The method of claim 9, wherein the acetabular guide has a second planar surface opposite the first surface, and wherein the bore is an open bore extending between the first and second surfaces.

11. The method of claim 10, wherein controlling a depth of the patient-specific implantation slot includes engaging a three-dimensional depth control surface of the acetabular guide to a corresponding outer surface of a distal portion of a handle of the cutting tool.

12. The method of claim 11, wherein the depth control surface extends from the planar second surface of the acetabular guide.

13. The method of claim 9, further comprising implanting a patient-specific partial acetabular implant in the patient-specific implantation slot.

14. The method of claim 13, wherein the partial acetabular implant has a peripheral surface configured to mate with a wall of the patient-specific implantation slot.

15. The method of claim 14, wherein the partial acetabular implant has an outer surface configured to be continuous with a surrounding cartilage after implantation.

16. The method of claim 13, further comprising anchoring the patient-specific partial acetabular implant in the acetabulum using an anchoring element.

17. A method for a partial socket replacement comprising:
mounting a patient-specific acetabular guide on an acetabulum of a patient, wherein the acetabular guide has a first curved three-dimensional surface configured to nestingly mate to the patient's acetabulum, including the acetabulum's articular cartilage and acetabular fossa in only one position, and a second planar surface opposite the first surface;
guiding a cutting tool through a patient-specific bore of the acetabular guide, wherein the patient-specific bore extends through the first and second surfaces of the acetabular guide and is configured to overlay a defect in the acetabulum of the patient;
removing damaged tissue of the defect;
forming a patient-specific implantation slot; and
controlling a depth of the patient-specific implantation slot by the acetabular guide physically constraining the cutting tool from advancing further into the acetabulum.