# Patent

## Title
Coordinate mapping system for joint treatment

## Abstract

A coordinate mapping system is provided for locating a defect in a bone. The system comprises a positioning instrument for controlled delivery of a device to a target site, the instrument comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predefined grid lines, and a template configured to overlay an image of a bone having a defect at the target site, the template including a predefined grid for determining a set of coordinates to locate the target site using the positioning instrument. A method of accessing a target site near a defect in a bone using the radial coordinate mapping system is also provided.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional No. 61/311,632, filed Mar. 8, 2010, and entitled “COORDINATE MAPPING SYSTEM FOR KNEE JOINT REPAIR AND METHODS OF USE,” and U.S. Provisional No. 61/263,170 filed Nov. 20, 2009, and entitled “METHOD FOR TREATING JOINT PAIN AND ASSOCIATED INSTRUMENTS,” all of which are herein incorporated by reference in their entirety.


This application also relates to co-pending and co-owned U.S. patent application Ser. No. 12/950,355, filed Nov. 19, 2010 and entitled “SUBCHONDRAL TREATMENT OF JOINT PAIN,” the content of which is herein incorporated in its entirety by reference.
FIELD
The present invention relates to devices and tools for surgical treatment of joints, and more particularly to instruments and associated methods for the surgical repair and treatment of bone tissue at these joints. Even more particularly, the present invention relates to a coordinate mapping system for locating a bone defect using anatomical landmarks.
BACKGROUND
Human joints, in particular the knee, hip and spine, are susceptible to degeneration from disease, trauma, and long-term repetitive use that eventually lead to pain. Knee pain, for example, is the impetus for a wide majority of medical treatments and associated medical costs. The most popular theory arising from the medical community is that knee pain results from bone-on-bone contact or inadequate cartilage cushioning. These conditions are believed to frequently result from the progression of osteoarthritis, which is measured in terms of narrowing of the joint space. Therefore, the severity of osteoarthritis is believed to be an indicator or precursor to joint pain. Most surgeons and medical practitioners thus base their treatments for pain relief on this theory. For example, the typical treatment is to administer pain medication, or more drastically, to perform some type of joint resurfacing or joint replacement surgery.
However, the severity of osteoarthritis, especially in the knee, has been found to correlate poorly with the incidence and magnitude of knee pain. Because of this, surgeons and medical practitioners have struggled to deliver consistent, reliable pain relief to patients especially if preservation of the joint is desired.
Whether by external physical force, disease, or the natural aging process, structural damage to bone can cause injury, trauma, degeneration or erosion of otherwise healthy tissue. The resultant damage can be characterized as a bone defect that can take the form of a fissure, fracture, lesion, edema, tumor, or sclerotic hardening, for example. Particularly in joints, the damage may not be limited to a bone defect, and may also include cartilage loss (especially articular cartilage), tendon damage, and inflammation in the surrounding area.
Patients most often seek treatment because of pain and deterioration of quality of life attributed to the osteoarthritis. The goal of surgical and non-surgical treatments for osteoarthritis is to reduce or eliminate pain and restore joint function. Both non-surgical and surgical treatments are currently available for joint repair.
Non-surgical treatments include weight loss (for the overweight patient), activity modification (low impact exercise), quadriceps strengthening, patellar taping, analgesic and anti-inflammatory medications, and with corticosteroid and/or viscosupplements. Typically, non-surgical treatments, usually involving pharmacological intervention such as the administration of non-steroidal anti-inflammatory drugs or injection of hyaluronic acid-based products, are initially administered to patients experiencing relatively less severe pain or joint complications. However, when non-surgical treatments prove ineffective, or for patients with severe pain or bone injury, surgical intervention is often necessary.
Surgical options include arthroscopic partial meniscectomy and loose body removal. Most surgical treatments conventionally employ mechanical fixation devices such as screws, plates, staples, rods, sutures, and the like are commonly used to repair damaged bone. These fixation devices can be implanted at, or around, the damaged region to stabilize or immobilize the weakened area, in order to promote healing and provide support. Injectable or fillable hardening materials such as bone cements, bone void fillers, or bone substitute materials are also commonly used to stabilize bone defects.
High tibial osteotomy (HTO) or total knee arthroplasty (TKA) is often recommended for patients with severe pain associated with osteoarthritis, especially when other non-invasive options have failed. Both procedures have been shown to be effective in treating knee pain associated with osteoarthritis.
However, patients only elect HTO or TKA with reluctance. Both HTO and TKA are major surgical interventions and may be associated with severe complications. HTO is a painful procedure that may require a long recovery. TKA patients often also report the replaced knee lacks a “natural feel” and have functional limitations. Moreover, both HTO and TKA have limited durability. Accordingly, it would be desirable to provide a medical procedure that addresses the pain associated with osteoarthritis and provides an alternative to a HTO or TKA procedure.
In current practice, surgeons typically “eyeball” the target site on a bone to be repaired. Most conventional targeting and location methods are crude and provide little guidance to a surgeon during the actual surgical procedure. Accordingly, it would be desirable to provide methods and systems in which a bone defect can be accurately located and provide a reference framework that can be used in a surgical procedure irrespective of the approach.
SUMMARY
The present disclosure relates to a coordinate mapping system for locating a bone defect using anatomical landmarks. The system allows the surgeon to accurately locate the bone defect with a reference framework and access the defect using a positioning instrument during surgery.
In one exemplary embodiment, a coordinate mapping system is provided for locating a defect in a bone. The system comprises a positioning instrument for controlled delivery of a device to a target site, the instrument comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predefined grid lines, and a template configured to overlay an image of a bone having a defect at the target site. The template can include a predefined grid for determining a set of coordinates to locate the target site using the positioning instrument. The grid may be, for example, a radial grid.
In another exemplary embodiment, a method of accessing a target site near a defect on a bone is provided. The method comprises the step of providing a template having a predefined grid for determining a set of coordinates to locate a target site on a bone having a defect, overlaying the template on an image of the bone, the template being aligned with an anatomical landmark on the bone, determining a set of coordinates of the location of the defect from the grid, providing a positioning instrument for controlled delivery of a device to the target site, comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predefined grid lines on the template, aligning the positioning instrument to the anatomical landmark on the bone so that the indicia on the positioning instrument are consistent with the grid of the template, and accessing the target site using the set of coordinates.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.
FIGS. 1A and 1B show an exemplary embodiment of a radial coordinate template superimposed over a top-down image of a bone, such as the tibia, having a defect;
FIG. 2 conceptually illustrates the implementation of the radial coordinate template of FIGS. 1A and 1B by an exemplary embodiment of an positioning instrument of the present disclosure;
FIG. 3A shows a top-down view of an exemplary embodiment of an positioning instrument of the present disclosure;
FIG. 3B shows a perspective side view of the positioning instrument of FIG. 3A;
FIG. 4A shows a top-down view of another exemplary embodiment of an positioning instrument of the present disclosure;
FIG. 4B shows a perspective side view of the positioning instrument of FIG. 4A;
FIG. 5A shows a top-down view of yet another exemplary embodiment of an positioning instrument of the present disclosure;
FIG. 5B shows a perspective side view of the positioning instrument of FIG. 5A;
FIG. 6 shows an exemplary embodiment of a radial coordinate template superimposed over an image of a side view of a bone, such as the femur, having a defect;
FIGS. 7A-7D show an exemplary use of another positioning instrument of the present disclosure on a femur; and
FIGS. 8A-8C show an exemplary use of yet another exemplary positioning instrument of the present disclosure on a femur.



DESCRIPTION OF THE EMBODIMENTS
The present disclosure provides a methodology, devices and instruments for diagnosing and treating joint pain to restore natural joint function and preserving, as much as possible, the joint's articular and cartilage surface. Treatments through the joint that violate the articular and cartilage surface often weaken the bone and have unpredictable results. Rather than focusing on treatment of pain through the joint, the embodiments diagnose and treat pain at its source in the subchondral region of a bone of a joint to relieve the pain. Applicants have discovered that pain associated with joints, especially osteoarthritic joints, can be correlated to bone defects or changes at the subchondral level rather than, for example, the severity of osteoarthritic progression or defects at the articular surface level. In particular, bone defects, such as bone marrow lesions, edema, fissures, fractures, hardened bone, etc. near the joint surface lead to a mechanical disadvantage and abnormal stress distribution in the periarticular bone, which may cause inflammation and generate pain. By altering the makeup of the periarticular bone (which may or may not be sclerotic) in relation to the surrounding region, it is possible to change the structural integrity of the affected bone and restore normal healing function, thus leading to a resolution of the inflammation surrounding the defect.
Applicants have discovered that treatment of the bone by mechanical and biological means to restore the normal physiologic stress distribution, and restore the healing balance of the bone tissue at the subchondral level, is a more effective way of treating pain than conventional techniques. That is, treatment can be effectively achieved by mechanically strengthening or stabilizing the defect, and biologically initiating or stimulating a healing response to the defect. Accordingly, the present disclosure provides methods, devices, and systems for a subchondral procedure. This procedure and its associated devices, instruments, etc. are also marketed under the registered trademark name of SUBCHONDROPLASTYTM. The SUBCHONDROPLASTYTM procedure is a response to a desire for an alternative to patients facing partial or total knee replacement.
In general, the SUBCHONDROPLASTYTM or SCPTM technique is intended to both strengthen the bone and stimulate the bone. In SCPTM, bone fractures or non-unions are stabilized, integrated or healed, which results in reduction of a bone defect, such as a bone marrow lesion or edema. In addition, SCPTM restores or alters the distribution of forces in a joint to thereby relieve pain. SCPTM can be performed arthroscopically or percutaneously to treat pain by stabilizing chronic stress fracture, resolving any chronic bone marrow lesion or edema, and preserving, as much as possible, the articular surfaces of the joint. SUBCHONDROPLASTYTM generally comprises evaluating a joint, for example, by taking an image of the joint, detecting the presence of one or more subchondral defects, diagnosing which of these subchondral defects is the source of pain, and determining an extent of treatment for the subchondral defect. The present technique is particularly suited for treating chronic defects or injuries, where the patient's natural healing response has not resolved the defect. It should be noted, however, that the technique is equally applicable to treatment of defects in the subchondral region of bone where the defect is due to an acute injury or from other violations. The present disclosure provides several exemplary treatment modalities for SCPTM for the different extents of treatment needed. Accordingly, a medical practitioner may elect to use the techniques and devices described herein to subchondrally treat any number of bone defects as he deems appropriate.
In some embodiments, detection and identification of the relevant bone marrow lesion or bone marrow edema (BML or BME) can be achieved by imaging, e.g., magnetic resonance imaging (MRI), X-ray, manual palpation, chemical or biological assay, and the like. A T1-weighted MRI can be used to detect sclerotic bone, for example. Another example is that a T2-weighted MRI can be used to detect lesions, edemas, and cysts. X-ray imaging may be suitable for early-stage as well as end-stage arthritis. From the imaging, certain defects may be identified as the source of pain. In general, defects that are associated with chronic injury and chronic deficit of healing are differentiated from defects that result, e.g., from diminished bone density. SCPTM treatments are appropriate for a BML or BME that may be characterized as a bone defect that is chronically unable to heal (or remodel) itself, which may cause a non-union of the bone, stress or insufficiency fractures, and perceptible pain. Factors considered may include, among other things, the nature of the defect, size of the defect, location of the defect, etc. For example, bone defects at the edge near the articular surface or periphery of a joint may be often considered eligible for treatment due to edge-loading effects as well as the likelihood of bone hardening at these locations. A bone defect caused by an acute injury would generally be able to heal itself through the patient's own natural healing process. However, in such situations where the bone defect is due to an acute injury and either the defect does not heal on its own, or the medical practitioner decides that the present technique is appropriate, SCPTM treatments can be administered on acute stress fractures, BML or BME, or other subchondral defects, as previously mentioned.
According to the embodiments, the SCPTM treatment may continue after surgery. In particular, the patient may be monitored for a change in pain scores, or positive change in function. For example, patients are also checked to see when they are able to perform full weight-bearing activity and when they can return to normal activity. Of note, if needed, the SCPTM procedure can be completely reversed in the event that a patient requires or desires a joint replacement or other type of procedure. The SCPTM treatment may also be performed in conjunction with other procedures, such as cartilage resurfacing, regeneration or replacement, if desired.
The present disclosure provides a number of treatment modalities, and associated devices, instruments and related methods of use for performing SUBCHONDROPLASTYTM. These treatment modalities may be used alone or in combination.
In one treatment modality, the subchondral bone in the region of the bone marrow lesion or defect can be strengthened by introduction of a hardening material, such as a bone substitute, at the site. The bone substitute may be an injectable calcium phosphate ensconced in an optimized carrier material. In SCPTM, the injected material may also serve as a bone stimulator that reinvigorates the desired acute bone healing activity.
For example, polymethylmethacrylate (PMMA) or calcium phosphate (CaP) cement injections can be made at the defect site. PMMA injection may increase the mechanical strength of the bone, allowing it to withstand greater mechanical stresses. CaP cement injection may also increase the mechanical strength of the bone, while also stimulating the localized region for bone fracture repair. In one embodiment, the injection can be made parallel to the joint surface. In another embodiment, the injection can be made at an angle to the joint surface. In yet another embodiment, the injection can be made below a bone marrow lesion.
In another treatment modality, the subchondral bone region can be stimulated to trigger or improve the body's natural healing process. For example, in one embodiment of this treatment modality, one or more small holes may be drilled at the region of the defect to increase stimulation (e.g., blood flow, cellular turnover, etc.) and initiate a healing response leading to bone repair. In another embodiment, after holes are drilled an osteogenic, osteoinductive, or osteoconductive agent may be introduced to the site. Bone graft material, for example, may be used to fill the hole. This treatment modality may create a better load-supporting environment leading to long term healing. Electrical or heat stimulation may also be employed to stimulate the healing process of a chronically injured bone. Chemical, biochemical and/or biological stimulation may also be employed in SCPTM. For instance, stimulation of bone tissue in SCPTM may be enhanced via the use of cytokines and other cell signaling agents to trigger osteogenesis, chondrogenesis, and/or angiogenesis to perhaps reverse progression of osteoarthritis.
In yet another treatment modality, an implantable device may be implanted into the subchondral bone to provide mechanical support to the damaged or affected bone region, such as where an insufficiency fracture or stress fracture has occurred. The implant may help create a better load distribution in the subchondral region. In the knees, the implant may support tibio-femoral compressive loads. In addition, the implant may mechanically integrate sclerotic bone with the surrounding healthy bone tissue. The implant may be placed in cancellous bone, through sclerotic bone, or under sclerotic bone at the affected bone region. The implant may also be configured as a bi-cortical bone implant. In one embodiment, one side of the implant can be anchored to the peripheral cortex to create a cantilever beam support (i.e., a portion of the implant is inserted into bone but the second end stays outside or near the outer surface of the bone). The implant may be inserted using a guide wire. In one example, the implant may be inserted over a guide wire. In another example, the implant may be delivered through a guide instrument.
The implant may further be augmented with a PMMA or CaP cement injection, other biologic agent, or an osteoconductive, osteoinductive and/or osteogenic agent. The augmentation material may be introduced through the implant, around the implant, and/or apart from the implant but at the affected bone region, such as into the lower region of a bone marrow lesion or below the lesion. For example, the implant may act as a portal to inject the augmentation material into the subchondral bone region.
While each of the above-mentioned treatment modalities may be administered independent of one another, it is contemplated that any combination of these modalities may be applied together and in any order so desired, depending on the severity or stage of development of the bone defect(s). Accordingly, the present disclosure also provides suitable implantable fixation devices for the surgical treatment of these altered bone regions or bone defects, especially at the subchondral level. Applicants have also discovered devices and instruments that can be used in combination with cements or hardening materials commonly used to repair damaged bone by their introduction into or near the site of damage, either to create a binding agent, cellular scaffold or mechanical scaffold for immobilization, regeneration or remodeling of the bone tissue.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. Additional features of the disclosure will be set forth in part in the description which follows or may be learned by practice of the disclosure.
Referring now to FIGS. 1A and 1B, embodiments of the present disclosure employ a coordinate mapping system 10 comprising a template 20 and a positioning instrument 100. In the present examples, the template 20 may include radial coordinates having a radial component and an angular component. This coordinate mapping system 10 may be used to locate a bone defect with the positioning instrument 100. The coordinate mapping system 10 more naturally resembles the various approaches that may be employed by a surgeon.
In one embodiment, the template 20 utilizes a predefined radial grid that corresponds to indicia 30 for keyed angles on the positioning instrument 100. The template may be implemented in tangible form, such as a transparency, that may be placed over an image of the bone to be treated. The image could be for example, an MRI, an X-ray, other scanned image, or a combination of one or more of these images. Alternatively, the template 20 may be implemented using software that displays the predefined grid as an overlay onto a display of the image. The template 20 may be customized to account for variations in the dimensions and angle of the image.
While the present examples of templates 20 employ a radial grid, it is understood that other types of grids and coordinate systems may be employed with the template 20 of the present disclosure. Another type of grid may include a Cartesian grid, for instance. Further, any combination of grids or coordinate systems may be utilized in combination together with the present system 10 for even more precise location of the bone defect.
FIGS. 1A and 1B show an exemplary embodiment of a template 20 of the coordinate mapping system 10 superimposed over an image of a bone, such as the tibia 2, having a defect 8. As shown, the template 20 comprises a series of radial grid lines 22 spanning 180 degrees. The radial grid lines 22 extend from a common starting point at vertex 24, and terminate at an outer edge 26. Each radial grid line 22 includes a set of interval markings 28 designating a predetermined distance or length. In addition, the radial grid lines 22 are labeled by indicia 30.
As shown for one embodiment, the radial grid lines 22 may be distributed in 15 degree intervals. However, it is understood that the radial grid lines 22 may be separated by other degrees of intervals, such as 5, 10, 20, etc. degree intervals as appropriate for the surgical application of the system 10.
Interval markings 28 on each of the radial grid lines 22 may serve as a convenient indicator of distance from either the vertex 24 or the outer edge 26. The interval markings 28, for example, may represent a predetermined distance of 2, 5, or 10 mm.
To implement the coordinate mapping system 10, the template 20 is positioned such that its vertical grid line G-A aligns with the tubercle 6 of tibia 2, as shown in FIGS. 1A and 1B. Depending on the desired approach angle (e.g., medial, lateral, etc.), the horizontal grid line A-G of template 20 may be adjusted up or down until the defect 8 falls within the desired coordinates represented by the angular position of the two most adjacent grid lines 22 as well as the interval markings 28 of the closest of the two grid lines 22. For example, in FIG. 1A the defect 8 can be located along grid line F, which provides a relatively shallow angle of approach. Alternatively, in FIG. 1B, the horizontal line A-G of the template 20 is moved down, and the same defect 8 can be located between grid lines C and D, which provides a relatively wider angle of approach.
FIG. 2 conceptually illustrates the implementation of the template 20 of FIGS. 1A and 1B onto a positioning instrument 100 of the coordinate mapping system 10 of the present disclosure. For purposes of clarity, certain portions of the template 20 are not shown to allow more space for viewing. As can be seen, the positioning instrument 100 comprises a main body 102 from which extends an arm 104 that terminates at contact pad 106 configured to seat against tubercle 6. Of note, the vertical axis G-A of the template 20 is aligned with the central axis of arm 104. The positioning instrument 100 also includes a rail 140 that extends from the main body 102. As shown, the outer edge 26 of the template 20 matches the outer surface 142 of rail 140. In some embodiments, the outer edge 26 of the template 20 can be matched to the inner surface 144 of the rail 140.
In use, the template 20 provides a mechanism for determining a set of three coordinates for locating the defect 8 based on the patient's own anatomy (i.e., tubercle). For example, as shown in FIG. 2, the template 20 indicates a first coordinate, distance d1, represented by the number of interval markings 28 between the outer edge 26 to tubercle 6 along vertical axis G-A. The second coordinate may represent the angular component corresponding to radial grid line 22 as indicated by the indicia labeled “E” in this example. The third coordinate may represent the distance d2 represented by the number of interval markings 28 between the outer edge 26 to the location of the defect 8 along the “E” radial grid line 22. Accordingly, the example shown in FIG. 2 may have a coordinate set of 2-60-2.5.
FIGS. 3A and 3B illustrate in greater detail the positioning instrument 100 of coordinate mapping system 10. As shown in FIG. 3B, the positioning instrument 100 may further include a brace component 120. The brace component 120 may comprise a shaft 122 hinged to brace 126. The brace 126 may pivot relative to the shaft 122, which can also be adjusted relative to the main body 102 such that the brace can be adjusted to accommodate and bear against the patient's leg.
As also shown, the rail 140 may be circular. However, it is understood that the rail 140 may be configured with any other shape. The height of the rail 140 may be adjustable relative to the main body 102. In one embodiment, a pointer or indicator (not shown) could be provided that points to the joint from the vertically adjustable portion of the body 102 that can be visible with use of a C-arm during surgery. The surgeon would align the pointer with a C-arm visible landmark such as the joint line by adjusting the vertical location of the upper portion of the instrument 100.
Rail 140 may comprise an open slot 146 for receiving an alignment guide 150. Though not shown, the alignment guide 150 may have a protrusion or tab that allows it to seat within and slide inside the open slot 146. The alignment guide 150 may also include device portals 152 for receiving a device, as well as tool-receiving holes 154 for receiving a tool such as a pin 50, for example. The device portals 152 may be arranged parallel to each other. It is understood that these portals 152 may be provided in other arrangements such as in an arc pattern or these portals 152 may be angled to converge.
In one embodiment, the rail 140 may extend at an angle to a transverse plane of the tibia 2. The angle could be in the range of about 1 to 15 degrees, more preferably about 2 to 10 degrees, and even more preferably about 3 to 7 degrees. In one example, the rail 140 may be configured to extend at an angle of about 7 degrees to a transverse plane of the tibial plateau. This slight angle enables the rail 140 to be oriented parallel to the tibial plateau (which typically has a natural, inherent slope), thereby allowing the user to have instrumentation that better matches the natural contours of the bone to be treated and which allows for the correct angular access to the target site. Accordingly, the angular orientation of the rail 140 allows the user a greater angular opening to access the bone clear of ligament and other surrounding soft tissue, and prevents inadvertent angular insertion of any instruments or devices through cartilage or other unintended bone or soft tissue, causing damage to the joint.
FIGS. 4A and 4B illustrate another exemplary embodiment of a positioning instrument 100 whereby there are two main bodies 102 on either end of the rail 140, each main body 102 having an arm 104 with contact pad 106 for seating against the tibia 2. As further shown, the arms 104 may be configured to extend through the contact pads 106 and into the tibia 2 in order to secure the positioning instrument 100 to the bone.
FIG. 5A and FIG. 5B show another exemplary embodiment of a positioning instrument 100 in which the arm 104 is adjustable in height along the length of main body 102. An optional pointer or indicator (not shown) could be provided on the body 102 that points to the joint such that C-arm imaging can be used for vertical positioning of the instrument 100 during surgery. The pointer would be aligned with anatomy seen under C-arm such as the joint line, for example.
In this example, the rail 140 may be provided with a series of portals 148 that may be used as an alternative to the device portals 152 of alignment guide 150. Accordingly, in this embodiment no alignment guide 150 would be necessary and the surgeon could insert a device or tool directly through the rail 140 by way of these portals 148.
In one embodiment, the rail 140 could be configured to slidably adjust in the medial lateral direction with respect to the main body 102 to allow for fine tuning adjustment of the system 100. The adjustment would correspond to a medial or lateral shift of the template 20 from the G-A vertical line. In addition, the rail 140 could be straight instead of curved, and angled (i.e., angled linear rail), such that the portals 148 are parallel in arrangement. This would allow the use of a rotated X-Y coordinate grid on the template 20 rather than a radial grid. The linear rail 140 could be configured to angularly adjust relative to the main body 102. The main body 102 could be stabilized with a plurality of fixation pins to the bone, or additional arms 104 may be provided on the positioning instrument 100 for more stability as desired.
FIG. 6 shows an exemplary embodiment of a template 20′ configured for use with a femur 4. As shown, this template 20′ is superimposed over an image of a side view of the femur 4 having a defect 8. Similar to template 20, the femoral template 20′ comprises again a series of radial grid lines 22 spanning 180 degrees. Of course, it is understood that the template 20 may be configured with radial grid lines 22 that span any variety of degrees, such as for example 90, 270, 360, etc. as desired. The radial grid lines 22 extend from a common starting point at vertex 24, and terminate at an outer edge 26. In this embodiment, the radial grid lines 22 may be distributed in 18 degree intervals represented by indicia 30 labeled A to F.
In use, the axis F-A of the femoral template 20′ is aligned with the axis 12 of the femur 4. The axis F-A is central to the distal portion of the shaft of the femur 4. Like template 20, the femoral template 20′ provides for a set of three coordinates for locating the defect 8 in the femur 4 using the patient's own anatomical landmarks (i.e., axis of femoral shaft). For example, as shown in FIG. 6, the template 20′ indicates a first coordinate, distance d3, represented by the number of interval markings 28 between the vertex 24 to the joint line 14. The second coordinate may represent the angular component corresponding to radial grid line 22 as indicated by the indicia labeled “C” in this example. The third coordinate may represent the distance d4 represented by the number of interval markings 28 between the vertex 24 to the location of the defect 8 along the “C” radial grid line 22. Accordingly, the example shown in FIG. 6 may have a coordinate set of 8-36-7.25, representing radial grid components and an angular component.
FIGS. 7A-7D show an exemplary use of another positioning instrument 200 of the present disclosure on a femur 4. As shown, the positioning instrument 200 may comprise an elongate body 202 terminating in a hub 208. The elongate body 202 may be attached along a portion of its length to braces 204, as illustrated in FIGS. 7A to 7D. Braces 204 are configured for use with a lower limb, such as a lower leg portion. It is understood, however, that other mechanisms may be employed instead of braces 204, such as for example, straps for securing the positioning instrument 200 to a lower leg portion.
Tool-engaging holes 206 may also be provided on the elongate body 202 for receiving a tool such as a pin 50. In use, the center C1 of hub 208 is placed at a distance d3 from joint line 14 of the femur 4, as indicated by template 20′ (see FIGS. 7A and 7B). In one example, a slidable arm 210 having an open-ended slot 212 for easy removal may be employed to position the elongate body 202 such that the center C1 of hub 208 is a distance d3 from the joint line 14, which can be determined from an anterior-posterior view of a C-arm image during the surgery. The elongate body 102 is aligned with the axis 12 of the femoral shaft. Pins 50 may be placed in order to secure the elongate body 102 to the femur 4 along its axis 12, as shown. After the elongate body 102 is secured, the slidable arm 210 may be removed, as shown in FIGS. 7C and 7D.
Extending from the hub 208 is a linear rail 220 at the angle specified by template 20′. The linear rail 220 comprises markings 224 along a circular portion 222 with a center C2 that aligns with the center C1 of hub 208. The linear rail 220 is configured to cooperate with an alignment guide 250. Alignment guide 250 may be configured with a slot to slidably receive linear rail 220, as shown. The alignment guide 250 may be positioned a distance d4 from the center C1 of hub 208. As shown, the alignment guide 250 may include device portals 252 that are arranged parallel to each other. It is understood that these portals 252 may be provided in other arrangements such as in an arc pattern.
The alignment guide 250 serves as a jig, or a box/frame for guiding a device to the defect. Each portal 252 has a predetermined distance and spatial relationship relative to the other portals 252. The portals 252 serve as spatial references or orientation or location markers for the clinician, and are configured to provide accurate and controlled delivery of a device to the defect. The portals 64 may be configured at any desired angle relative to the alignment guide 250. In one embodiment, the portals 252 may be angularly configured to guide, or direct, the device in a parallel direction relative to the top of the bone being treated, for example. In addition, the device portals 252 can include an anti-rotation feature (not shown). For example, the device portals 252 may be keyed, or shaped with a specific configuration that matches with a shape configuration of the device to be inserted. The keyed device portals 252 allow the device to enter and to move freely in a linear direction in and out of the portals 252, all the while preventing free rotation thereabout. Thus, the anti-rotation feature provides a further level of control for the clinician.
FIGS. 8A-8C show yet another positioning instrument 200′ of the present disclosure on a femur 4. Positioning instrument 200′ is similar in structure to positioning instrument 200′ described above, with like elements having the same reference numerals followed by the mark “′”. However, unlike positioning instrument 200, positioning instrument 200′ may have a relatively short main body 202′ for use without braces. Instead, main body 202′ may include one or more tool-engaging holes 206′ for receiving a tool such as pin 50. These pins 50 may extend through the tool-receiving holes 206′ of the main body 202′ and into the femur 4 to secure the instrumentation to the bone. In addition, the center C1 of hub 208′, along with the center C2 of circular portion 222′ of the linear rail 220′ may include a tool-engaging hole 206 for also receiving a tool such as a pin 50, as shown in FIGS. 8A-8C.
In use, the positioning instrument 200′ may be aligned to an anatomical landmark similar to positioning instrument 200. In the case of this femur 4, the positioning instrument 200′ may be aligned to the adductor tubercle on the distal femur, as shown. Pins 50 may be placed through the tool-engaging holes 206′ of the centers C1, C2 of hub 208′ and circular portion 222′ of the main body 202′ and linear rail 220′, respectively. These pins 50 may extend through the open-ended slot 212′ of the slidable arm 210′ and into bone for securing the instrument 200′ in place (see FIG. 8B). Similar to FIGS. 7A-7D, the slidable arm 210′ of instrument 200′ may be aligned to the joint line 14 of the femur 4 as identified through, for example, C-arm imaging during surgery. The positioning instrument 200′ should be positioned so as to correspond to the template 20′ for the femur 4, like in the previous example. Though not shown, the slidable arm 210′ may be removed at this point if so desired.
After the positioning instrument 200′ has been properly aligned and secured to the femur 4, the linear rail 220′ can be positioned at an angle corresponding to the angular component of the three coordinate set determined by the femoral template 20′ to map the location of the defect 8 on the femur 4. Next, alignment guide 250′ may be slid onto the linear rail 220′ as shown in FIG. 8C. The alignment guide 250′ may be positioned such that the device portals 252′ are aligned with the target site, or defect 8 according to a radial grid component of the three coordinate set. Then, one or more devices may then be inserted through the device portal 252′ of the guide 250′ and to the defect to effect the desired treatment. Positioning instrument 200′ may be used percutaneously, and may serve as a fluoroscopic percutaneous device positioning instrument.
In the examples shown, the device may be a pin 50. However, the term “device” is used herein to refer generally to any number of implantable devices, materials and instruments suitable for bone treatment and/or repair. For example, the device may be an implantable device, an insertion tool, a drill bit, an injection needle, a catheter, or any other surgical instrument. The device may be marked with indicia or colored bands representing depth so that the clinician is better able to control the depth into the bone.
The coordinate mapping system 10 of the present disclosure provides the advantage of precise and repeated access to a target site from a variety of angles or trajectories. It is contemplated that the system 10 may be used to compact bone tissue at the target site from multiple approaches, or angles. For example, it is possible to use the system 10 to target the same area around the defect from different angles to clean up compressed bone tissue at the target site. By approaching the same defect using different trajectories, it is possible to create any number of geometric patterns of compacted bone tissue around or at the target site, such as for example, a starburst-like pattern.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure provided herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

## Claims

1. A coordinate mapping system comprising:
a positioning instrument for controlled delivery of a device to a target site within a bone, comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predetermined grid lines, the instrument further providing a series of device portals configured to guide the device into a subchondral region of the bone for treatment at the target site, the series of device portals provided on the rail for access to the target site; and
a template configured to overlay an image or the bone having a defect at the target site, the template including a predefined grid for determining a set of coordinates to locate the target site using the positioning instrument, wherein at least one of the coordinates represents an interval of a radial grid line and at least one of the coordinates represents an angular component for mapping to the target site within the bone.

2. The system of claim 1, wherein the predefined grid is a radial grid, and the grid lines are radial grid lines.

3. The system of claim 1, further including a detachable brace component.

4. The system of claim 1, wherein the rail is circular.

5. The system of claim 4, wherein the target site is a defect on a tibia.

6. The system of claim 1, wherein the rail is linear.

7. The system of claim 6, wherein the target site is a defect on a femur.

8. The system of claim 1, wherein the set of coordinates comprises three coordinates.

9. The system of claim 8, wherein the set of coordinates comprises two coordinates that represent an interval of a radial grid line, and another coordinate that represents an angular component.

10. The system of claim 1, wherein the template has a shape corresponding to the rail of the positioning instrument.

11. A method of accessing a target site near a defect in a bone:
providing a template having a predefined grid for determining a set of coordinates to locate a target site on a bone having a defect;
overlaying the template on an image of the bone, the template being aligned with an anatomical landmark on the bone;
determining a set of coordinates of the location of the defect from the grid;
providing a positioning instrument for controlled delivery of a device to the target site, comprising a main body and a rail extending from the main body, the rail including a series of indicia corresponding to predefined grid lines on the template;
aligning the positioning instrument to the anatomical landmark on the bone so that the indicia on the positioning instrument are consistent with the radial grid of the template; and
accessing the target site using the set of coordinates.

12. The method of claim 11, wherein the bone is a tibia.

13. The method of claim 12, wherein the anatomical landmark is a tubercle.

14. The method of claim 11, wherein the bone is a femur.

15. The method of claim 14, wherein the anatomical landmark is a femoral shaft axis.

16. The method of claim 11, wherein the grid is a radial grid, and the grid lines are radial grid lines.