Avascular necrosis (AVN) of the femoral neck is a degenerative condition thought to be caused by increased interstitial pressure within the femoral head leading to reduced blood supply to the region and eventually bone necrosis. In the later stages III and IV of the disease, the spherical femoral heads collapses into a non-spherical shape usually with cartilage damage, ultimately requiring a total hip replacement. The challenge is to remove the necrotic bone and replace it with a viable graft or bone graft substitute before the femoral head collapses or cartilage is damaged.
To remove the necrotic bone, while removing as little of the surrounding healthy bone as possible, bone removal is done though the bone tunnel using curettes or buns. Their use is guided, primarily, by tactile feedback and fluoroscopy. One prior approach to bone removal involves a surgeon placing an endoscope down the bone tunnel to see the necrotic bone. In this prior approach, however, the surgeon does not remove bone and view at the same time. Various grafts are then used including autologous bone, allografts, bone graft substitutes, and free vascularized fibula autografts to fill in the void left from removing the necrotic bone. Such grafts are then press fit in or are held in place via mixing with blood, or by screws and plates.
Core decompression is the most common treatment for AVN. The procedure consists of placing a guide-wire from the lateral aspect of the greater trochanter into the femoral head followed by over drilling to form a 9-12 mm diameter bone tunnel, also referred to as a“core decompression tunnel.” The guide-wire is placed by taking multiple orthogonal fluoroscopy images. Challenges with the current core decompression technique include the possibility of drilling through the femoral head and the possibility of leaving some necrotic bone behind preventing a successful graft. What is needed is an approach that places an endoscope into the core decompression tunnel and uses bone removal tools to extract necrotic bone under direct visualization.
Described herein are examples of an approach for removing necrotic bone under direct visualization is provided that address the foregoing shortcomings and others as well. In one aspect, at least one example described herein provides a sheath. The sheath includes a body including a proximal end and a distal end, and an inlet disposed at the proximal end of the body through which inflow fluid is provided. The body further includes a first passageway extending, longitudinally, between the proximal and distal ends of the body. The body still further includes a second passageway extending, longitudinally, from the distal end of the body towards the proximal end of the body. The second passageway defines an axis of rotation of a bone removal tool. The first and second passageways are spaced apart such that the axis of rotation of the bone removal tool is offset from the centerline of a bone tunnel. A working length of the body has a diameter smaller than the diameter of the bone tunnel.
In other examples, the sheath may further include one or more of the following, alone or in any combination. In some examples of the sheath, the first passageway is curved with the first passageway and the second passageway spaced apart a first distance at the distal end of the body and spaced apart a second distance greater than the first distance at the proximal end of the body. In other examples of the sheath, at the distal end of the body, the first passageway terminates with a rounded end. In some examples of the sheath, the second passageway is a U-shape trough. In other examples of the sheath, the first passageway and the second passageway are stacked on one another along a lateral axis defined by the inlet.
Some examples of the sheath further include a stop integrally formed with the body. The integrally formed stop includes a first stop surface and an opposed second stop surface. The first and second stop surfaces cooperate with a corresponding bead formed around a shaft of the bone removal tool to limit movement of the bone removal tool along a length of the second passageway. Alternatively, the first and second stop surfaces cooperate with a corresponding bend formed in a shaft of the bone removal tool to limit movement of the bone removal tool along a length of the second passageway.
Other examples of the sheath further include an inclined wall formed between the first passageway and the second passageway. The inclined wall defines a conduit with the wall of the bone tunnel for conducting outflow fluid carrying portions of removed bone.
In another aspect, at least one example described herein provides a system including a sheath and a visualization device received in a first passageway of the sheath. The sheath including a body comprising a proximal end and a distal end and an inlet disposed at the proximal end of the body through which inflow fluid is provided. The body further comprising a first passageway extending, longitudinally, between the proximal and distal ends of the body, and a second passageway extending, longitudinally, from the distal end of the body towards the proximal end of the body. The second passageway defines an axis of rotation of a bone removal tool. The first and second passageways are spaced apart such that the axis of rotation of the bone removal tool is offset from the centerline of the bone tunnel. A working length of the body has a diameter smaller than the diameter of the bone tunnel.
In other examples, the system may further include one or more of the following, alone or in any combination. In some examples, the first passageway of the sheath is curved with the first passageway and the second passageway spaced apart a first distance at the distal end of the body and spaced apart a second distance greater than the first distance at the proximal end of the body. In other examples, the first passageway of the sheath and the visualization device have different cross-sections. The difference in cross-sections defines a conduit for the inflow fluid. In some examples, the visualization device is an endoscope.
Some examples of the system further include a bone removal tool. The bone removal tool includes a shaft and a working end at an end of the shaft. At least a portion of the shaft of the bone removal tool is received in the second passageway of the sheath. The shaft of the bone removal tool may be flexible. The working end of the bone removal tool may include a three-dimensional rasp comprising two cutting edges meeting at a leading point. The leading point meets the wall of the bone tunnel at a 32° angle and contacts bone before the two cutting edges as the working end is rotated. Other examples of the bone removal tool include rotary rasp, articulating rotary curette, articulating planer curette, and rotary wireform.
Other examples of the system further include an inlet port including a first end adapted to mate with the inlet of the sheath and a second end adapted to mate with an inflow fluid source. The inlet port may be in the shape of a handle. Some examples of the second end include a coupling member with a breakaway feature, such that when the second end of the inlet port is being disconnected from an inflow fluid source the coupling member breaks away from the second end.
In yet another aspect, at least one example described herein provides a bone removal tool. The bone removal tool includes a shaft having a length, a portion of which is supported by a passageway of a sheath, and a working end at an end of the shaft. In some examples, the working end has an axis of rotation defined by a second passageway of the sheath and is offset from the centerline of a bone tunnel. The shaft may be flexible. Some examples of the bone removal tool include a bead formed around the shaft. The bead cooperates with a first stop surface and an opposed second stop surface of a stop integrally formed with the sheath. Other examples of the bone removal tool include a bend formed in the shaft. The bend cooperates with a first stop surface and an opposed second stop surface of a stop integrally formed with the sheath.
The working end of the bone removal tool may include a three-dimensional rasp comprising two cutting edges meeting at a leading point. The leading point meets the wall of the bone tunnel at a 32° angle and contacts bone before the two cutting edges as the working end is rotated. Other examples of the bone removal tool include rotary rasp, articulating rotary curette, articulating planer curette, and rotary wireform.
In still yet another aspect, at least one example described herein provides a procedure for removing bone under direct visualization. The procedure includes a) forming a bone tunnel, b) inserting an assembly into the bone tunnel, the assembly including an visualization device received in a first passageway of a sheath and a bone removal tool received in a second passageway of the sheath, c) rotating the bone removal tool about an axis of rotation defined by the second passageway and that is offset from the centerline of the bone tunnel to remove a portion of the bone, and d) viewing the portion of bone being removed while the bone removal tool is being rotated.
In other examples, the procedure may further include one or more of the following, alone or in any combination. Some examples include changing a field of view of the visualization device by rotating the visualization device within the first passageway of the sheath. Other examples include providing an inflow fluid to where bone is being removed through a conduit defined by a difference in cross-section of the visualization device and cross-section of the first passageway of the sheath. Some examples include conducting an outflow fluid carrying portions of removed bone through a conduit defined by the wall of the bone tunnel and an inclined wall formed between the first passageway and the second passageway of the sheath.
Other examples include moving the bone removal tool along a length of the second passageway of the sheath. Some other examples may further include moving a bead formed around a shaft of the bone removal tool between a first stop surface and a second stop surface of a stop integrally formed in the sheath. The bead and the first and second stop surfaces corporate to limit movement of the bone removal tool along the length of the second passageway. Alternative examples may include moving a bend formed in a shaft of the bone removal tool between a first stop surface and a second stop surface of a stop integrally formed in the sheath. The bend and the first and second stop surfaces corporate to limit movement of the bone removal tool along the length of the second passageway.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate examples of the present disclosure and together with the written description serve to explain the principles, characteristics, and features of the disclosure. In the drawings:
In the following detailed description of the illustrated examples, reference is made to accompanying drawings, which form a part thereof, and within which are shown by way of illustration, specific examples, by which the subject matter can be practiced. It is to be understood that other examples can be utilized and structural changes can be made without departing from the scope of the disclosure.
The particulars shown herein are by way of example and for purposes of illustrative discussion of the examples only and are presented in the case of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the disclosure. In this regard, no attempt is made to show structural details of the subject matter in more detail than is necessary for the fundamental understanding of the disclosure, the description taken with the drawings making apparent to those skilled in that how the several forms of the present disclosure can be embodied in practice. Further, like reference numbers and designations in the various drawings indicate like elements.
An approach for removing necrotic bone under direct visualization is provided. Examples of the approach include accessing necrotic bone and removing necrotic bone. It is noted that some examples of the approach include both accessing and removing necrotic bone while other examples include one or the other. The tools and procedures for accessing necrotic bone are described first. The necrotic bone is accessed through a bone tunnel. As overview, to form the bone tunnel, a surgeon places a guide-wire through bone and into necrotic bone. The surgeon then guides a cannulated drill bit along the guide-wire to drill the bone tunnel through the bone and into the necrotic bone. The surgeon selects a location for the guide-wire based on the shape and size of the necrotic bone. In some examples of the approach, the surgeon uses a three-dimensional guide to assist in placing the guide-wire in the selected (desired) location in the necrotic bone.
In more detail with reference to
In another example of the approach, the surgeon places the guide-wire in the selected location completely under fluoroscopic control. The challenge with this approach is maintaining the trajectory of the guide-wire that was found acceptable in a first plane (e.g. AP or lateral), while redirecting it (or a second guide-wire) to an acceptable trajectory in a second plane (e.g. lateral or AP). The surgeon may need to continue to optimize placement of the guide-wire through continuous toggling between AP and lateral views (i.e., taking multiple orthogonal fluoroscopy images), losing alignment in one plane while adjusting the alignment in the other plane. This adds time to the procedure, and increases the radiation dose to the patient, surgeon, and supporting staff.
The three-dimensional guide 16 allows the surgeon to hold the proper orientation of the guide wire in one plane (e.g. AP or lateral) while adjusting the position in the other plane (e.g. lateral or AP). One can readily appreciate that contrasted with the “freehanded” approach described immediately above, using the three-dimensional guide 16 can reduce the number of fluoroscopy images taken and, thus, lessens the radiation dose to the patient, surgeon, and supporting staff.
Turning now to a description of removing necrotic bone,
It should be readily apparent that in other examples of the approach, the surgeon may use bone removal tools with any number of different types and sizes of working ends. For example,
While the surgeon is removing the necrotic bone, the surgeon can see the material being removed at the same time using the endoscope 42. Advantageously, removing bone under direct visualization, as described above, provides the surgeon with real-time visual feedback. The surgeon adjusts the bone removal process (e.g., remove more or less bone) in response to what the surgeon sees. Additionally, the approach also allows for direct visualization of the underside of the cartilage layer covering the femoral head. This is beneficial because such visualization prevents or at least minimizes the undesirable chance of breaking through the femoral head.
The prior approach requires the surgeon to stop removing bone (and possibly remove a bone removal tool from a bone tunnel) in order to insert an endoscope to inspect the progress and then to restart the process. The discontinuous nature of the prior approach makes the procedure tedious and time consuming Additionally, the prior approach requires the surgeon to remember what the surgeon saw and then remove bone based on that memory. In contrast, the bone removal under direct visualization approach is continuous. The endoscope 42, coupled to the bone removal tool 44 by the sheath 46, remains in the bone tunnel 32 during the bone removal process. In turn, the procedure is less tedious, less time consuming, and does not require the surgeon to remember what the surgeon saw and then remove bone based on that memory.
In some examples of the approach, the surgeon rotates the bone removal tool 44 manually. The manual examples provide the surgeon with tactile feedback.
In other examples of the approach, the surgeon rotates a powered bone removal tool 44c by using a powered device, such as power drill. In the example shown in
In addition to the examples of the working end 48 described above, another example of the bone removal tool 44 includes a rasp 100 with a three-dimensional geometry, as shown in the
Some examples of the bone removal tool 44 are offered in a series of steps, increasing the cutting size so as to minimize the torque required to turn them. Other examples of the bone removal tool 44 expand to increase the cutting size, again, to minimize the torque required to turn them. In still other examples, a combination of drill bit and bone removal tool forms a bone tunnel with a distal tunnel shape with minimum stress concentrations, i.e. , a continuous, curved surface. This is contrasted with a traditional drill bit that leaves a distinct edge between the distal conical face and cylindrical hole of the bone tunnel.
As shown in
As further shown in
In some examples of the sheath 46 that are used in conjunction with an endoscope, the first passageway 54 (endoscope passageway) is curved to accommodate the relatively larger camera portion at the proximal end of the endoscope. The first passageway 54 and second passageway 56 are spaced apart a first distance at the distal end 50 of the body 47 and are spaced apart a second distance greater than the first distance at the proximal end 49 of the body 47.
In a convenient example of the sheath 46 for use with an endoscope shown in
In a convenient example, an outer surface 42a of the endoscope 42 and an inner surface 54a of the first passageway 54, which houses the endoscope 42, form a conduit 64 for inflow fluid (liquid or gas). As shown, the endoscope 42 has a circle-shaped cross-section and the first passageway 54 has an oval-shaped cross-section. The inflow fluid conduit 64 is formed by the “difference” between the two cross-sections. It should be readily apparent that in other examples, the inflow fluid conduit 64 is formed by the endoscope 42 and first passageway 54 having cross-sections of a variety of shapes with a difference between the cross-sections.
In some examples, an outer surface of the body 47 and the wall of the bone tunnel 32 form an outflow conduit. For example, an inclined wall 58 formed in the body 47 and extending between the first and second passageways 54, 56 forms an outflow conduit 66. The outflow conduit 66 conveys debris away from the surgical site during the bone removal procedure. This is helpful because it removes debris from the field of view of the endoscope 42 that would otherwise obstruct or at least limit the surgeon's view of the procedure. The inclined wall 58 also reduces the cross-section of the assembly. Advantageously, this geometry minimizes the possibility of debris blocking the outflow between the wall of the bone tunnel and along the side of the assembly. As such, this clog resistant example of the sheath 46 is suitable for procedures in which clogging is likely.
Returning to
As best seen in
To further enhance the disposable nature of the inlet port 70, some examples of the coupling member 74 include a breakaway feature 74a that is best seen in
Returning to
In another example, the stop 57 is formed as a protrusion extending from the second passageway and away from the body. The protrusion cooperates with the bend 45a in the shaft of the bone removal tool 44. In yet another example, the sheath 46 includes an indicator and the bone removal tool 44 includes a depth mark that the surgeon can see. When the depth mark on the bone removal tool 44 lines up with the corresponding indicator on the sheath 46, the surgeon knows the bone removal tool 44 is close to the endoscope and moving past the mark will likely damage the endoscope. In still yet another example, the sheath 46 incorporates a selectively lockable mechanism to retain the bone removal tool 44 within the second passageway 56.
The foregoing discussion describes examples of the bone removal under direct visualization approach in the context of using an assembly including a sheath. Other examples of the approach are described below.
The integral flexing bone removal tool 244 is disposed at the distal end of the body. In the example shown, the integral flexing bone removal tool 244 flexes about an axis substantially perpendicular to the axis of the endoscope passageway.
In the foregoing examples of the integral sheath 82, an axis of rotation of the bone removal tool 244 and the axis of the endoscope passageway, and, thus, the endoscope are axially aligned or coaxial. Bone removal is within the field of view (FOV) of the endoscope. This approach allows the surgeon to actuate the endoscope and bone removal tool with one hand (e.g., by way of a handle, as shown). Some examples of the integral sheath 82 are disposable.
The endoscope remains fixed as the body and expanding bone removal tool rotate 344 around the endoscope. In a convenient example, an inflow liquid or gas passes between the outer surface of the endoscope and the inner surface of the passageway to reduce rotational friction between the endoscope and body. The inflow liquid or gas also keeps the site clear of debris, as described above.
The expanding bone removal tool 344 has a proximal end and a distal end. One or more expansion slits 90 run between the proximal and distal ends of the expanding bone removal tool 344. The expansion slit 90 is at a selected angle relative to the axis of the endoscope passageway. In some examples, the selected angle is 0° i.e., the expansion slit 90 is parallel to the axis of the endoscope passageway. The form, number, angle, and length of the expansion slit 90 are selected to provide an expanding bone removal tool 344 suitable for removing bone under direct visualization. In an expanded state, the expansion slit 90 opens and the bone removal expands to a diameter greater than the diameter of the bone tunnel. The resulting opening in the expansion slit 90 enables the surgeon to see the bone being removed. The expansion slit 90 is shown being a straight line in form but other forms are possible, such as a wave.
In the example of the integral sheath 82 shown in
In some examples, the integral sheath 82 further includes an actuating means for expanding the expanding bone removal tool 344. Such means include push/pull rods, pull-pull cables, and an untwisting tube. In other examples, the expanding bone removal tool 344 expands as it is rotated (i.e., by centrifugal force).
Some curette and wireform examples do not need to be passable along the length of the endoscope. These examples may be permanently assembled in their working configuration. To the extent any of the foregoing examples include an actuating mechanism, such mechanism can take many forms from live hinges to push/pull rods to pull-pull cables to sprung curettes (the natural state of which is bent), just to name a few. Flexing instruments, such as a flexing, motorized arthroscopy burr or a selectively lockable, flexing curettes/rasps are suitable for removing bone laterally from a bone tunnel. It should be readily apparent that these flexing instruments may be used with the bone removal under direct visualization approach just described.
Filing Document | Filing Date | Country | Kind |
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PCT/US14/51643 | 8/19/2014 | WO | 00 |
Number | Date | Country | |
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61867486 | Aug 2013 | US |