# Patent

## Title
Patient-specific numerically controlled instrument

## Abstract

A method for preparing a bone of a joint of a patient includes mounting a patient-specific reference guide on a bone of a joint of a patient. A connecting portion of the reference guide is coupled to a miniaturized numerically controlled instrument having a housing including a controller, a processor and a tool driver. The patient-specific reference guide has a three-dimensional inner surface preoperatively configured to mirror and mate with a corresponding surface of a bone of a joint of a patient in only one position. The patient-specific reference guide is configured to automatically register the numerically controlled instrument to the patient's bone portion intraoperatively. The cutting tool is guided by the controlled with signals from the processor along a patient-specific tool path determined during the preoperative plan for preparing a portion of the bone.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser. No. 13/087,854 filed on Apr. 15, 2011. The disclosure of the above application is incorporated herein by reference.


INTRODUCTION
The present teachings are directed to a numerically controlled instrument that can register automatically on a bone of a patient without intraoperative registration using computer-aided navigation or other intraoperative registration markings. The numerically controlled instrument includes a housing removably connected to a patient-specific reference guide, and a cutting tool removably coupled to a tool driver of the numerically controlled instrument. The patient-specific reference guide is designed preoperatively from medical scans of the patient. The cutting tool can move along a patient-specific tool path determined during the preoperative plan for preparing a bone portion of the patient's joint.
SUMMARY
The present teachings provide a medical device for preparing a bone of a joint of a patient includes a numerically controlled instrument having a housing including a controller, a processor and a tool driver, a patient-specific reference guide removably couplable to the housing, and a cutting tool removably coupled to the tool driver. The patient-specific reference guide has a three-dimensional inner surface preoperatively configured to mirror and mate with a corresponding surface of a bone of a joint of a patient in only one position. The patient-specific reference guide is configured to automatically register the numerically controlled instrument to the patient's bone portion intraoperatively. The cutting tool is movable along a patient-specific tool path determined during the preoperative plan for preparing a bone portion of the patient's joint.
The medical device of the present teachings can be used for various arthroplasty procedures, such as, for example, joint replacement, resurfacing or other bone preparation procedures for hip, shoulder, knee or other joints. In one exemplary embodiment, the patient-specific reference guide is a femoral reference guide mating with a femoral head of the patient for a femoral acetabular impingement procedure. In another exemplary embodiment, the patient-specific reference guide is an acetabular guide for preparing an acetabulum for an implant.
The present teachings also provide a method for preparing a bone of a joint of a patient. The method includes mounting a patient specific reference guide on a bone of a joint of a patient, coupling a housing of a numerically-controlled instrument to a connecting portion coupled to an outer surface of the reference guide and coupling a cutting tool to the housing. The patient specific reference guide has a three-dimensional inner surface preoperatively configured to mate and closely nest to a corresponding surface of the bone only in one position. The patient-specific reference guide automatically registers the numerically controlled instrument to the bone without intraoperative computer-aided navigation by coupling the housing to the reference guide. The cutting tool is guided along a patient-specific tool path that is determined preoperatively and stored in the numerically-controlled instrument for preparing a portion of the bone.
Further areas of applicability of the present teachings will become apparent from the description provided hereinafter. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings.



BRIEF DESCRIPTION OF THE DRAWINGS
The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 a block diagram a patient-specific numerically controlled instrument according to the present teachings;
FIG. 2 is an environmental perspective view of a patient-specific numerically-controlled instrument according to the present teachings and illustrated in a procedure for femoral acetabular impingement;
FIG. 3 is an environmental exploded view of a patient-specific numerically-controlled instrument according to the present teachings and illustrated in a procedure for acetabular socket preparation;
FIG. 3A is detail of the patient-specific numerically-controlled instrument of FIG. 3; and
FIG. 4 is an environmental perspective view of the patient-specific numerically-controlled instrument of FIG. 3 illustrated in a procedure for acetabular socket preparation.



Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
DETAILED DESCRIPTION
The following description is merely exemplary in nature and is in no way intended to limit the present teachings, applications, or uses.
The present teachings generally provide a patient-specific computer numerically controlled instrument (“CNC instrument”) for preparing a joint surface in joint arthroplasty, resurfacing or other orthopedic procedure. The CNC instrument is operable to guide a tool along a patient-specific tool path of the joint surface and references the joint surface using a removable patient-specific portion or reference guide. The patient-specific tool path is determined during a preoperative plan of the patient based on medical scans of the patient and is inputted and stored in the CNC instrument. The patent-specific reference guide can be removably coupled to the CNC instrument and is configured to be mateable only in one position with the joint surface of the specific patient. The patient-specific reference guide of the CNC instrument is disposable, while the remaining CNC instrument can be sterilized and re-used in different procedures for different patients with corresponding patient-specific reference guides.
The patient-specific reference guide can be designed preoperatively using computer-assisted image methods based on three- or two-dimensional images of the patient's joint anatomy reconstructed from medical scans of the patient's anatomy. 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.
Patient-specific devices are generally configured to match in a mirror-like fashion a portion of the anatomy of a specific patient. The patient-specific devices are generally formed using computer modeling based on the patient's 3-D anatomic image and have an engagement surface that is made to conformingly contact and match a three-dimensional image of the patient's anatomy, such as a joint surface, in only one position, using imaging software, as discussed above. The patient-specific devices are designed and prepared preoperatively using anatomic landmarks, such as, for example, osteophytes or other bone features, and can be mounted intra-operatively, without any other registration aid, navigation or other guidance, based solely on their unique patient-specific surface that is guided and matches the patient's anatomic landmarks.
Various patient specific devices 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. 12/389,901, filed Feb. 20, 2009, U.S. patent application Ser. No. 12/571,969, filed Oct. 1, 2009, U.S. patent application Ser. No. 12/893,306, filed Sep. 29, 2010, 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, imaging data of the relevant anatomy of a patient can be obtained at a medical facility or doctor's office, using a medical imaging method. 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, joint surface preparation, implant selection, patient-specific implant and/or tool creation or other 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. The medical scans can be obtained using MRI, CT, X-ray, ultrasound or other imaging methods. Computer instructions for preparing the patient's joint surface using a cutting tool can be generated during the preoperative plan and stored in a tool path data file. The tool path file can be provided as an input to the CNC instrument for preparing the patient's joint surface for arthroplasty, resurfacing, defect removal, or other procedure.
The patient-specific devices can be manufactured by various stereolithography methods, selective laser sintering, fused deposition modeling or other rapid prototyping methods. The patient-specific devices can be made of any biocompatible material, including metal, metal alloys or plastic. Generally, the patient-specific devices are disposable and can be made of lightweight materials, including polymers. The patient-specific devices and other reusable instruments and tools can be sterilized and shipped to the surgeon or medical facility in a kit assembled for a specific patient and/or specific surgeon for use during the surgical procedure.
Referring to FIG. 1, a block diagram of an exemplary CNC instrument 100 is illustrated according to the present teachings. The CNC instrument 100 is a miniaturized instrument for guiding a single tool at a time for preparing, for example, an acetabular socket for receiving an acetabular cup, or for resurfacing a portion of an articulating femoral or humeral head, or for removing impinging bone growths, or other joint preparation procedures, as discussed below. The power requirements and travel area of the CNC instrument 100 are accordingly quite small, such that the CNC instrument 100 can have minimal dimensions, small motor and weight and can be operated as a unitary device with a small onboard motor 104 and an onboard battery or other power supply 102. In some embodiments, if further weight reduction is desired, the motor 104 and or power supply 102 can be housed separately and coupled to the CNC instrument 100 with a flexible connector.
With continued reference to FIG. 1, the patient-specific CNC instrument 100 can generally include a body or housing 101, a power supply 102, a motor 104 and a controller 106. The power supply 102 can be a disposable or rechargeable battery and/or DC or AC adapter/cable connection for supplying the power needs of the CNC instrument 100. The controller 106 can communicate with a tool driver 114 and a computing module that includes a processor 108, memory storage 110 and an input/output device or module 112. The tool driver 114 can be removably coupled to a cutting tool 150 directly or by using a tool connector 120. The cutting tool 150 can be, for example, a burr, drill, mill or other cutting tool. For weight reduction, the cutting tool 150 can be a single cutting instruments adapted for a single cutting operation. If two or more different cutting tools 150 are used for a patient-specific procedure, the cutting tools 150 can be used sequentially, one at a time. The cutting tool 150 is numerically controlled by the CNC instrument 100 to perform a pre-programmed cutting procedure along a tool path that is determined during the preoperative plan of the patient, as discussed below.
Referring to FIG. 1, the CNC instrument 100 can also be removably coupled to a patient-specific reference guide 200 directly or by using a guide connector 116. It should be appreciated that the patient-specific guide 200 and the guide connector 116 are configured such that they do not interfere with the controlled motion of the cutting tool 150, as controlled by the tool path that is transmitted/implemented by the tool driver 114. The housing 101 can include the controller 106, the tool driver 114, the processor 108, memory storage 110 and an input/output device or module 112. In some embodiments, the housing 101 can also include the motor 104 and/or a portable power supply 102, in the form of a rechargeable, reusable, disposable or single-use battery, for example.
With continued reference to FIG. 1, the patient-specific reference guide 200 is designed during the preoperative plan of the patient using three-dimensional images of the patient's joint reconstructed from medical scans of the patient, as discussed above. The reference guide 200 is designed to nestingly mate and conform to a bone of a joint of the patient in only one position. Because of the reference guide 200 is designed to fit and mate in a unique position that references the patient's corresponding joint anatomy, the reference guide 200 provides a reference coordinate system XYZ for the tool path and also registers the CNC instrument 100 and the tool path automatically without using any other intraoperative navigation aids. As discussed above, the tool path can be determined from the three dimensional images of the patient's joint during the preoperative plan and a tool path file can be created. The tool path file can be provided through the input/output (I/O) module 112 of the CNC instrument as data file or other computer file. The I/O module 112 can be a USB flash drive, an SD port or other device that can receive digital data, including a wireless communication module for wireless transfer of data. The I/O module 112 can also incorporate a display, a keyboard or other user interface (not shown). The processor 108 can convert the tool path file into machine language or CNC code for the tool path. The controller 106 can convert the tool path code to electrical signals for the tool driver 114 to control the motion of the tool 150 according to the patient-specific preoperative plan.
An exemplary embodiment of the patient-specific CNC instrument 100 for a femoral procedure is illustrated in FIG. 2. In this embodiment, the CNC instrument 100 is used intraoperatively for guiding a milling, burring or other cutting instrument 150 to remove a bony growth or defect 90 of the proximal femoral bone to correct a bone abnormality, such as, for example, a femoral acetabular impingement or other abnormality or defect that may cause excessive acetabular over coverage and asymmetric junction between a femoral head 80 and a femoral neck 84. In the exemplary embodiment of FIG. 2, the patient-specific reference guide 200 is configured to mate with a portion of the outer surface 82 of the femoral head 80 of the specific patient for removing the femoral acetabular impingement abnormality or defect associated with the bony growth 90. Other defect corrections can include, for example, removal of osteophytes, removal of various bone protrusions, corrections associated with CAM and Pincer impingements, including acetabular retroversion, coxa profunda, coxa vara, protrusio acetabuli, elliptical femoral head, slipped capital femoral epiphysis (SCFE), malunited femoral neck fractures and other bone abnormalities.
With continued reference to FIG. 2, the cutting tool 150 can be removably coupled to the housing 101 using an optional tool connector 120, such as a socket coupling, a snap-on connection or other type of connection. The tool connector 120 provides an interface for merely changing cutting tools 150 and does not interfere with the motion of the cutting tool 150 as determined by the tool path. The cutting tool 150 can include a rotatable shaft 152 and a cutting head 156, such as a burr head or mill head that can be coupled to the shaft 152 and rotate with shaft 152. A collar or sleeve or a tubular bushing 154 can surround and slidably receive the shaft 152 to allow the cutting head 156 to be optionally moved along the shaft 152.
Referring to FIG. 2, the patient-specific reference guide 200 has an outer surface 202 and an inner surface 204 forming a three-dimensional shell-like structure that extends from a first end surface 208 to a second end surface 210. The inner surface 204 is a three-dimensional curved surface that is patient-specific to a corresponding outer surface 82 of the femoral head 80, such that the inner surface 204 conforms and mates with the femoral head 80 only in one position, based on natural asymmetry and other natural landmarks of the femoral head 80 of the patient (landmarks not shown in FIG. 2). Further, the patient-specific reference guide 200 is configured and dimensioned to leave the bony growth 90 exposed and to provide clearance for the motion of the cutting tool 150. The patient-specific reference guide 200 can include, integrally (monolithically) or modularly, a connecting portion 206 extending from or coupled to the outer surface 202 of the reference guide 200 for coupling the reference guide 200 to a guide connector 116 of the housing 101. The connecting portion 206 and the guide connector 116 provide a non-custom interface for coupling the same housing 101 of the CNC instrument 100 for repeated use with different patients and procedures by using a corresponding disposable patient-specific guide 200 for each patient. The connecting portion 206 and the guide connector 116 can be configured for quick-connect coupling, tapered connection, snap-on connection, removable fastener or screw connection or other removable coupling.
The patient-specific reference guide 200 can also establish and reference a fixed XYZ coordinate system with a predetermined origin C, such as, for example the center of the femoral head 80. The axis Z can coincide with an alignment axis A of the femoral head 80 and can be parallel to the axis of the shaft 152 of the cutting tool 150 and can also be centered about the connecting portion 206 of the reference guide 200. By positioning intraoperatively the patient-specific reference guide 200 uniquely on the femoral head 80, the CNC instrument 100 is automatically registered to the XYZ coordinate system without using computer-aided or other intraoperative navigation.
Referring to FIGS. 3, 3A and 4, another embodiment of the CNC instrument 100A is illustrated for an acetabular procedure, such as, for example, reaming or milling an acetabulum 72 of a pelvis 70 of a patient. Similarly to the above embodiment of the CNC instrument 100 of FIG. 2, the CNC instrument 100A includes a tool connector 120A and a plurality of guide connectors 116A for connecting with a patient-specific reference guide 300 at a plurality of locations. The patient-specific reference guide 300 is an annular ring having first and second opposing surface 302, 304 and an opening with an inner wall surface 306 between the first and second surfaces 302, 304. The second or inner surface 304 is designed and configured during the preoperative plan of the patient to nestingly conform and mirror (as a negative of) a corresponding annular surface around a rim 74 of the acetabulum 72 of the patient in only one position, establishing automatically an XYZ coordinate system with origin C centered in the acetabulum 72 of the patient.
With continued reference to FIGS. 3-4, the patient-specific reference guide 300 can include a plurality of holes 310 that receive bone screws 140 for securing the patient-specific reference guide 300 to the pelvis 70 of the patient. Each bone screw 140 can include a screw head 142 that receives a connecting adaptor 145 for removably connection with a corresponding guide connector 116A in the housing 101. A distal end of each connecting adaptor 145 can engage the screw head 142 of the bone screw 140. Each adaptor 145 and optionally the screw head 142 of the corresponding bone screw 140 can be received in a corresponding guide connector 116A, which can be in the form of a receptacle for a snap-on connection or other quick-connect/quick-disconnect connection. It is contemplated that other types of connections can also be used, including other supporting frames or rigs or structures and other removably fastening mechanisms, including tongue-and-slot, dovetail, ball-and-socket or rotatable or universal links and joints.
The cutting tool 150 of FIG. 2 can also be used with this embodiment of the CNC instrument 100A. The shaft 152 of the cutting tool 150 can be removably coupled to a tool connector 120A with a removable connection, as discussed above. The cutting tool 150 can be guided by the tool program of the CNC instrument 100A to move along a pre-programmed tool path, as determined during the preoperative plan of the patient, for milling, reaming or otherwise preparing the acetabulum 72 of the patient for receiving an acetabular implant or for other purposes. By coupling the housing 101A of the CNC instrument 100A to the patient-specific reference guide 300, the CNC instrument 100A is automatically registered intraoperatively to the patient's acetabulum without using computer aided navigation or other type of intraoperative navigation. The patient-specific reference guide 300 can also establish a fixed XYZ coordinate system with a predetermined origin C, such as, for example the center of the acetabulum 72. The axis Z can coincide with an alignment axis A of the acetabulum 72 and can be parallel to the axis 152 of the cutting tool 150 and to the bone screws 140. The tool driver 114 (FIG. 1) can guide the cutting tool 150 to prepare the acetabulum 72 according to the patient-specific tool path that has been prepared during the preoperative plan for the patient.
The medical devices and methods described above can be used for various arthroplasty procedures, such as, for example, joint replacement, resurfacing or other bone preparation procedures for hip, shoulder, knee or other joints. The patient-specific reference guide and/or cutting tool can be replaced each time with a patient-specific reference guide and a cutting tool for each patient and procedure while using the same housing and other non-patient-specific components of the CNC instrument.
The foregoing discussion discloses and describes merely exemplary arrangements of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein, so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the present teachings as defined in the following claims.

## Claims

1. A method for preparing a bone of a joint of a patient comprising:
mounting a patient specific reference guide on a bone of a joint of a patient, the patient specific reference guide having a three-dimensional inner surface preoperatively configured to mate and closely nest to a corresponding surface of the bone only in one position, wherein mounting the patient specific reference guide on a bone of a joint of a patient includes mounting the reference guide on a femoral head surface of the patient, and wherein the reference guide is configured for mating with the femoral head surface of the patient;
coupling a housing of a numerically-controlled instrument to a connecting portion coupled to an outer surface of the reference guide;
automatically registering the numerically controlled instrument to the bone by coupling the housing to the reference guide and without intraoperative computer-aided navigation;
coupling a cutting tool to the housing;
guiding the cutting tool along a patient-specific tool path using the numerically-controlled instrument while the housing is mounted to the reference guide, the patient-specific tool path determined preoperatively and stored in the numerically-controlled instrument; and
preparing a portion of the bone using the cutting tool.

2. The method of claim 1, wherein preparing the portion of the bone includes removing a femoral acetabular impingement defect from a femoral neck of the bone.

3. A method for preparing a bone of a joint of a patient comprising:
mounting a patient specific reference guide on a bone of a joint of a patient, the patient specific reference guide having a three-dimensional inner surface preoperatively configured from preoperative scans of the bone of the joint to mirror and mate with a corresponding surface of the bone only in one position;
coupling a guide connector of a housing of a miniaturized numerically-controlled instrument to a connecting portion coupled to an outer surface of the reference guide, the housing including the guide connector, a controller, a processor and a tool driver;
automatically registering the numerically controlled instrument to the bone by coupling the housing to the reference guide;
converting by the processor a patient-specific tool path to signals for the controller, the patient-specific tool path determined preoperatively and stored in the numerically-controlled instrument; removably coupling a cutting tool to the housing;
operating by the controller the tool driver from the signals; and
guiding the cutting tool along the patient-specific tool path using the numerically-controlled instrument while the housing is mounted to the reference guide.

4. The method of claim 3, further comprising:
removing a femoral acetabular impingement defect with the cutting tool.

5. The method of claim 3, further comprising:
removing a bony growth of a femoral neck with the cutting tool.

6. The method of claim 3, further comprising:
preparing an acetabular socket of the joint for receiving an acetabular cup with the cutting tool.

7. The method of claim 3, further comprising:
resurfacing a femoral head of the joint with the cutting tool.

8. The method of claim 3, further comprising:
resurfacing a humeral head of the joint with the cutting tool.

9. The method of claim 3, further comprising:
removing a defect of a femoral head of the joint with the cutting tool.

10. The method of claim 3, wherein the reference guide is an annular ring and wherein mounting the patient specific reference guide on a bone of a joint of a patient further includes mating the annular ring to an annular area around a rim of the acetabulum of the patient.

11. The method of claim 10, further comprising preparing the acetabulum of the patient for receiving an implant.

12. The method of claim 3, wherein mounting the patient specific reference guide on a bone of a joint of a patient includes mounting the reference guide on a femoral head surface of the patient, and wherein the reference guide is a shell-like structure configured for mating with the femoral head surface of the patient.

13. A method for preparing a bone of a joint of a patient comprising:
mounting a patient specific reference guide on a bone of a joint of a patient, the patient specific reference guide having a three-dimensional inner surface preoperatively configured from preoperative scans of the bone of the joint to mirror and mate with a corresponding surface of the bone only in one position, the reference guide including a connecting portion;
coupling a housing of a miniaturized numerically-controlled instrument to the connecting portion of the reference guide, the housing including a controller, a processor and a tool driver;
automatically registering the numerically controlled instrument to the bone by coupling the housing to the inner surface of the reference guide;
processing and converting a patient-specific tool path to signals for the controller, the patient-specific tool path determined preoperatively and stored in the numerically-controlled instrument;
removably coupling a cutting tool to the housing;
controlling the tool driver from the signals; and
guiding the cutting tool along the patient-specific tool path using the numerically-controlled instrument while the housing is mounted to the reference guide.

14. The method of claim 13, further comprising:
removing a femoral acetabular impingement defect with the cutting tool.

15. The method of claim 13, further comprising:
removing a bony growth of a femoral neck with the cutting tool.

16. A method for preparing a bone of a joint of a patient comprising:
mounting a patient specific reference guide on a bone of a joint of a patient, the patient specific reference guide having a three-dimensional inner surface preoperatively configured to mate and closely nest to a corresponding surface of the bone only in one position, wherein mounting the patient specific reference guide on a bone of a joint of a patient includes mounting the reference guide on an acetabulum of the patient;
coupling a housing of a numerically-controlled instrument to a connecting portion coupled to an outer surface of the reference guide;
automatically registering the numerically controlled instrument to the bone by coupling the housing to the reference guide and without intraoperative computer-aided navigation;
coupling a cutting tool to the housing;
guiding the cutting tool along a patient-specific tool path using the numerically-controlled instrument while the housing is mounted to the reference guide, the patient-specific tool path determined preoperatively and stored in the numerically-controlled instrument; and
preparing a portion of the bone using the cutting tool.

17. The method of claim 16, wherein the reference guide is an annular ring and wherein mounting the patient specific reference guide on a bone of a joint of a patient further includes mating the annular ring to an annular area around a rim of the acetabulum of the patient.

18. The method of claim 17, wherein preparing the portion of the bone includes preparing the acetabulum of the patient for receiving an implant.

19. The method of claim 17, wherein coupling the housing of a numerically-controlled instrument to a connecting portion coupled to an outer surface of the reference guide includes coupling the housing with a plurality of connecting adaptors coupled to the reference guide.