Patent Application
20090234392
The present invention relates to spinal fixation and methods for use during orthopedic surgery. More particularly, the present invention relates to inserting a spinal fixation element, such as a rod, using guide tabs extending from bone anchor implanted along a patient's spine.
Spinal fixation systems may be used in surgery to align, adjust and/or fix portions of a spinal column, i.e., vertebrae, in a desired spatial relationship relative to each other. Many spinal fixation systems employ a spinal rod for supporting the spine and for properly positioning components of the spine for various treatment purposes. Implants, such as vertebral bone anchors, comprising pins, bolts, screws, and hooks, engage the vertebrae and connect the supporting spinal rod to different vertebrae. Spinal rods can be anchored to specific portions of the vertebra. Since each vertebra varies in shape and size, a variety of anchoring devices have been developed to facilitate engagement of a particular portion of the bone.
Pedicle screw assemblies, for example, have a shape and size that is configured to engage pedicle bone. Such screws typically include a threaded shank that is adapted to be threaded into a vertebra, and a head portion having a spinal fixation element-receiving portion, which, in spinal rod applications, is usually in the form of a U-shaped slot formed in the head portion for receiving the rod. A set-screw, plug, cap or similar type of closure mechanism is used to lock the rod into the rod-receiving portion of the pedicle screw.
In conventional spinal surgery, first, anchoring devices are attached to vertebra, and then a spinal rod is aligned with the anchoring devices and secured. For example, for conventional pedicle screw assemblies, first the engagement portion of each pedicle screw is threaded into a vertebra. Once the pedicle screw assembly is properly positioned, a spinal fixation rod is connected in the rod-receiving portion of each pedicle screw head. The rod is locked into place by tightening a cap or similar type of closure mechanism to securely interconnect each pedicle screw to the fixation rod. This type of conventional spinal surgical technique usually involves making a surgical access opening in the back of the patient that is almost as long as the length of the spinal rod to be implanted. Because exact placement of the screw assemblies depends on a patient's particular bone structure and bone quality, the exact position of all screw assemblies cannot be known until after all the assemblies are positioned. Adjustments, such as bending, are made to the spinal rod to ensure that it aligns with each screw assembly.
Recently, the trend in spinal surgery has been moving toward providing minimally invasive surgical (MIS) devices and methods for implanting spinal fixation elements. In minimally invasive surgical techniques, the anchors and rod are typically inserted through small incisions. For example, the anchors and rod may be delivered percutaneously to an implant site through a small access port such as a cannula. In other methodologies, a mini-open technique may be used to place the spinal fixation system.
However, such minimally invasive procedures introduce other issues. Because the bone anchors and spinal fixation element are inserted through small incisions, such as percutaneously, there is reduced visibility of the surgical site. Placement of the spinal fixation element becomes more difficult when there is no direct view of the surgical site. Thus, what is needed is a means for being able to accurately insert a spinal fixation element along a patient's spine when using minimally invasive surgical techniques.
Embodiments of the present invention provide methods for inserting a spinal fixation element using minimally invasive surgical techniques. The methods use implants having guide tabs. The guide tabs are used to locate the spinal fixation element along a patient's spine. The guide tabs may be orientated in different ways to accommodate different insertion techniques for the spinal fixation element.
In accordance with one aspect, a method is provided for inserting a spinal fixation element along a patient's spine, the method involves inserting a first implant having a guide tab into a first vertebra. A second implant having a guide tab may then be inserted into a second vertebra. The spinal fixation element may then be inserted using the guide tabs of the first and second implants to locate the spinal fixation element along the patient's spine.
In other embodiments, the spinal fixation element may be inserted before the first or second implant. After the implants are inserted, the spinal fixation element may be moved into position using the guide tabs to locate the spinal fixation element along the patient's spine.
In certain embodiments, the bone anchor is an anchor bolt. The anchor bolt has a bone engagement portion; a threaded head portion for receiving a locking member; and a rod connector body disposed between the bone engagement portion and the threaded head portion for connector bodying a rod. In certain embodiments the anchor bolt may include a detachable extension shaft that extends from the threaded head portion opposite the bone engagement portion.
In accordance with another aspect, a method is provided for inserting a spinal fixation element along a patient's spine. The method involves percutaneously inserting a first implant having a guide tab into a first vertebra. A second implant having a guide tab may then be percutaneously inserted into a second vertebra. The guide tabs of the first and second implants may then be orientated to define a channel along the patient's spine for receiving the spinal fixation element. The spinal fixation element may then be percutaneously inserted within the channel defined by the guide tabs of the first and second implants to locate the spinal fixation element along the patient's spine.
In accordance with another aspect, a method is provided for inserting a spinal fixation element along a patient's spine. The method involves making a mini-open incision along the patient's spine. A first implant having a guide tab may then be inserted, through the mini-open incision, into a first vertebra proximal to a first end of the mini-open incision. A second implant having a guide tab may then be inserted, through the mini-open incision, into a second vertebra proximal to a second end of the mini-open incision. The guide tabs may then be orientated to receive and guide the ends of the spinal fixation element. The spinal fixation element may then be inserted between the guide tabs, wherein the guide tabs of the first and second implants receive the first and second ends of the spinal fixation element and guide the insertion of the spinal fixation element along the patient's spine.
These and other features and advantages of the mechanisms and methods disclosed herein will be more fully understood by reference to the following detailed description in conjunction with the attached drawings in which like reference numerals refer to like elements through the different views. The drawings illustrate principles of the instruments and methods disclosed herein and, although not to scale, show relative dimensions.
Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the adaptable clamping mechanisms and methods disclosed herein. Examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.
As discussed above, embodiments of the present invention provide methods for inserting a spinal fixation element using minimally invasive surgical techniques. The implants used in exemplary embodiments have a guide tab which is used to locate the spinal fixation element along the patient's spine. Exemplary embodiments described herein concern implants for securing spinal fixation elements and methods of use. As such, exemplary embodiments of implants are formed of suitable materials for use in a human body. Suitable materials include, but are not limited to, stainless steel, titanium, or the like. Exemplary embodiments of implants are sized and dimensioned for insertion through a minimally invasive surgical access port, such as a cannula.
An example of one embodiment of a suitable implant can be seen in
The bone anchor 110 comprises a joint portion, illustrated as a proximal anchor head 112, for coupling the bone anchor 110 to the connector body 120 and an anchoring portion, illustrated as a distal shaft 114 configured to engage bone. The distal shaft 114 of the bone anchor 110 extends along a longitudinal axis 116. The distal shaft 114 may include one or more bone engagement mechanisms to facilitate gripping engagement of the bone anchor to bone. In the illustrated embodiment, the distal shaft 114 includes an external thread 118 extending along at least a portion of the shaft for engaging bone. In the illustrated embodiment, the external thread 118 is a single lead thread that extends from a distal tip 119 of the shaft to the anchor head 112, though one skilled in the art will recognize that the external thread may extend along any selected portion of the shaft and have any suitable number of leads. Other suitable bone engagement mechanisms include, but are not limited to, one or more annular ridges, multiple threads, dual lead threads, variable pitched threads and/or any conventional bone engagement mechanism.
The anchor head 112 of the bone anchor 110 may be configured to facilitate adjustment of the bone anchor 110 relative to the connector body 120 of the implant 100. For example, the illustrative anchor head 112 may be substantially spherical to permit pivoting of the bone anchor 110 relative to the connector body 120 in one or more selected directions. In some embodiments, the anchor head 112 may also have surface texturing, knurling and/or ridges.
In this example, the connector body 120 forms a seat 124 for receiving a spinal fixation element. A cavity 122 passes through the connector body 120 and is configured for receiving the bone anchor 110 and engaging the proximal head 112 of the bone anchor 110.
The connector body 120 receives the proximal head 112 of the bone anchor in the cavity 122 to couple the bone anchor 110 thereto. An example of this can be seen in
The cavity 122 of the connector body 120 is configured to interact with the spherical shape of the proximal head 112 of the bone anchor 110 to allow the bone anchor 110 to rotate and pivot independently of the connecter body 120 providing a polyaxial implant 100. Likewise, once the distal shaft 114 of the bone anchor 110 has been implanted in a bone (not shown) the interaction of the cavity 122 and proximal head 112 allow the connecter body 120 to be positioned to engage a spinal fixation element (not shown).
The detachable guide tab 130 extends from the connector body 120 in the longitudinal axis 116 opposite and offset of the distal shaft 114 of the bone anchor 110. Having the guide tab 130 offset provides reduced access to the proximal head 112 of the bone anchor 110 for inserting and potentially re-adjusting the height of the bone anchor 110. This is particularly beneficial in longer segment constructs where the bone anchor heights may need to be adjusted to match the curve of the spinal fixation element. Having one offset tab allows adjustment with the spinal fixation element not having to be removed from the site, rather just shifted lateral to the tab. Having the guide tab 130 offset also allows for side and top loading of a spinal fixation element (not shown) upon the seat 124 while still providing a guide for locating the spinal fixation element (not shown).
The detachable guide tab 130 is configured to extend outside the patient through the patient's skin while providing clear access to the connector body 120 and the proximal head 112 of the bone anchor 110. Accordingly, the guide tab 130 may form a partial cannula extending through the skin wherein the guide tab has a crescent shaped cross section. In some embodiments, additional components could be mated to the guide tab to more fully enclose the access site. In certain embodiments, the detachable guide tab 130 has a break-away feature 132 that may be fragile or weakened allowing the detachable guide tab 130 to be detached and removed. Alternatively, the detachable guide tab 130 can be detached by cutting the guide tab away from the implant 100. In still other embodiments, a secondary support could be used in conjunction with the guide tab to provide additional strength until breaking and removal is required. Other possible configurations and techniques will be apparent to one skilled in the art given the benefit of this disclosure. For example, the strength of the tab could be varied to provide enough force to maneuver the bone anchor and the spinal fixation elements together thereby potentially correcting spinal vertebral segments by adjusting their relative positions. The guide tabs may also be flexible to allow easier access of instrumentation and less crowding in the incisions. Alternatively, the guide tabs may also be a combination of stiffness. For example, the distal end could be stronger to provide the strength required for adjustments, while the proximal end exiting the skin incision could be flexible or malleable.
In certain embodiments, the detachable guide tab 130 may have one or more surface configurations 134 for engaging tools, spinal fixation elements, and/or closure mechanisms to further assist in the insertion and guidance of the tools, spinal fixation elements, and/or closure mechanisms. The surface configurations 134 may be one or more tracks on the guide tab 130. In some such embodiments, the tracks may be keyed to mate with specific tools, spinal fixation elements, and/or closure mechanisms. Other possible configurations and techniques will be apparent to one skilled in the art given the benefit of this disclosure.
It should be understood that the steps set forth above are provided in one possible order, the steps can be performed in any order, for example, the spinal fixation element may be inserted into the patient before either the first and/or second implant. If the implants are inserted after the spinal fixation element, the guide tabs of the implants can still be used to locate the previously inserted spinal fixation element along the patient's spine.
In certain embodiments, the method may further include additional steps. After insertion, the spinal fixation element may be further manipulated using the guide tabs of the first and second implants (step 240). Once the implants and spinal fixation element have been inserted (and manipulated), closure mechanisms may be inserted to connect the spinal fixation element to the implants. In the example of
In other embodiments, once the spinal fixation element has been connected to the implants, the guide tabs may be removed. In the example of
Various techniques can be used to insert the first and second implants (steps 210 and 220). For example, a minimally invasive percutaneous incision 302 may be made through the tissue at one or more sites as shown in
In certain exemplary embodiments, one or more of the incisions may be expanded to create a pathway from the incision 302 to proximate a vertebra 300. For example, the incision 302 may be expanded by serial dilation, with a retractor such as an expandable retractor, or by any other conventional techniques. In one exemplary embodiment, blunt finger dissection can be used, as shown in
An implant may be inserted through one or more of the incisions and the pathways to proximate the vertebra 300. Any technique for inserting an implant can be used. In one embodiment, for example, an implant can be inserted over a guidewire, such as a k-wire. As shown in
Once the incision 302 is dilated to the proper size, if necessary, the vertebra 300 may be prepared using one or more bone preparation instruments, such as drills, taps, awls, burrs, probes, etc. In certain exemplary embodiments, one or more cannulae can be used to provide a pathway from the incision 302 to the anchor site for insertion of the bone preparation instruments and/or the anchor. In an exemplary embodiment, a relatively small cannula (not shown) may be used to introduce bone preparation instruments into the surgical site. Once the vertebra 300 is prepared, an implant can be delivered along the k-wire, either through the cannula, or after the cannula is removed, and implanted in the vertebra 300. Alternatively, in embodiments not employing a guidewire, the implant may be advanced through the incision, e.g., through a cannula, to the vertebra 300. A cannula, retractor, or other instrument may be employed to guide the implant to the vertebra 800.
The implants may be oriented in a number of ways to assist in the insertion and targeting of a spinal fixation element.
A variety of techniques can be used to insert a spinal fixation element, such as a rod, to extend along a patient's spine (step 230). The spinal fixation element may also be introduced at various locations along the patient's spine. For example, the spinal fixation element can be introduced through the same incision used to introduce an implant, or alternatively the spinal fixation element can be introduced through an incision that is separate from and located a distance apart from the incisions used to insert the implants. The spinal fixation element may be inserted before or after the implants. The spinal fixation element can also either be directly introduced through the incision to extend up along the patient's spinal column, or it can be introduced through a cannula, access port, or along the guide tab 130 of an implant 100 for guiding the spinal fixation element to extend along the patient's spinal column. Various tools can also be coupled to the spinal fixation element to manipulate and facilitate introduction and positioning of the spinal fixation element in the patient's body. The techniques for the percutaneous insertion of a spinal fixation element are similar to those for inserting implants as discussed above.
In one exemplary embodiment, the guide tabs 130a and 130b of the first and second implants 100a and 100b may be used to guide the spinal fixation element into location along the patient's spine. As discussed above, the guide tabs 130a and 130b of the first and second implants 100a and 100b form partial cannulae through the patient's skin to the implant site. Accordingly, the insertion of the first and second implants 100a and 100b serve to provide the incisions used to insert the first and second implants 100a and 100b with an access port, via the partial cannulae formed by the guide tabs 130a and 130b, for the insertion of a spinal fixation element.
It should be noted that the spinal fixation element 500 need not be introduce though one of the incisions used to insert an implant 100. The spinal fixation element 500 may be introduced through a separate incision. In certain embodiments, the spinal fixation element 500 may be inserted remotely and then the first implant 100a and second implant 100b may be inserted. Alternatively, the first implant 100a and the second implant 100b may be inserted and then the spinal fixation element 500 may be inserted.
Once the first 100a and second 100b implant have been inserted, the spinal fixation element 500 may then be positioned onto the seats 124a and 124b of the first 100a and second 100b implants. In the example of
In certain embodiments, once a spinal fixation element 500 has been inserted, further adjustments may be required. As such, the guide tabs 130a and 130b may be used to manipulate the position of the spinal fixation device 500 (step 240). An example of this can be seen in
As discussed above, the implants 100a and 100b are polyaxial in nature wherein the connector bodies 120a and 120b are pivotable around the proximal heads 112a and 112b of the bone anchors 110a and 110b. As such, the connector bodies 120a and 120b may be pivoted around the proximal heads 112a and 112b to adjust the guide tabs 130a and 130b to different orientations as desired. As the guide tabs 130a and 130b extend outside the patient, the guide tabs 130a and 130b provide a convenient means for manipulating the position of the connector bodies 120a and 120b to which the guide tabs 130a and 130b are attached. In the example of
Once the spinal fixation element 500 has been inserted and positioned as desired, the spinal fixation element 500 may then be connected to the implants 100a and 100b to fix the position of the spinal fixation element 500. To achieve this, closure mechanisms are used.
An example using closure mechanisms can be seen in
If the implant 100a and 100b where inserted percutaneously, as describe above, the closure mechanisms 700a and 700b may be inserted through the same incisions used to insert the implant 100a and 100b. In certain embodiments, the closure mechanism 700a and 700b are configured to engage the surface configurations 134a and 134b of the guide tabs 130a and 130b. For example, the closure mechanisms 700a and 700b may be keyed to ride in rails provide by the surface configurations 134a and 134b. Thus, the closure mechanisms 700a and 700b may be slide along the guide tabs 130a and 130b from outside the patient to the connector body 120 inside the body to capture the spinal fixation element 500.
Once the spinal fixation element 500 has been captured by the closure mechanisms 700a and 700b, the closure mechanisms 700a and 700b may be secured using locking mechanisms 710a and 710b. In the example of
Once the spinal fixation element 500 has been connected to the implants 200a and 200b using the closure mechanisms 700a and 700b (steps 250 and 260), the guide tabs 130a and 130b of the implants 100a and 100b may be detached and removed In the case of the embodiments set forth above, this involves detaching the first guide tab 130a from the first implant 100a (step 270) and detaching the second guide tab 130b from the second implant 100b (step 280). As discussed previously, the guide tabs 130a and 130b of the implants 100a and 100b may include fragile or weakened or otherwise breakaway features 132a and 132b allowing for easier detachment and removal.
While the exemplary embodiment of
The guide tabs of the first and second implants may then be orientated to define a channel along the patient's spine for receiving the spinal fixation element (step 830). This orientation is described above in reference to
A spinal fixation element, such as a rod, may then be percutaneously inserted within the channel defined by the guide tabs of the first and second implants to locate the spinal fixation element along the patient's spine (Step 840). This was also discussed above in regard to
As with the method of
In other embodiments, once the spinal fixation element has been connected to the implants, the guide tabs may be removed. In the example of
While the previous examples dealt primarily with percutaneous insertion, it should be understood the method may be practiced using other types of insertion techniques may be used. One possible alternative exemplary embodiment can be seen in
In certain embodiments, the method may further include additional steps. After insertion, the spinal fixation element may be further manipulated using the guide tabs of the first and second implants (step 960). Once the implants and spinal fixation element have been inserted (and manipulated), closure mechanisms may be inserted to connect the spinal fixation element to the implants. In the example of
In other embodiments, once the spinal fixation element has been connected to the implants, the guide tabs may be removed. In the example of
A mini-incision is a minimally invasive surgical (MIS) technique in which a small incision on the patient along the spine is used to insert the implants and spinal fixation element. The incision is larger than used for percutaneous insertion but smaller than used in traditional techniques. In traditional techniques the incision may be span the entire of the patient's spine while a mini incision may just span the distance between two vertebrae on the patient's spine. An example of this can be seen in
In
In the example of
The steps of manipulation (step 960), inserting closure mechanisms (steps 970 and 980), and removing the guide tabs (steps 990 and 1000) may then be performed as discussed above. It will be apparent to one skilled in the art that the techniques and device discussed above for these steps can be modified for the particular orientation and insertion technique shown in
One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
While the methods and instruments of the present invention have been particularly shown and described with reference to the exemplary embodiments thereof, those of ordinary skill in the art will understand that various changes may be made in the form and details herein without departing from the spirit and scope of the present invention. Those of ordinary skill in the art will recognize or be able to ascertain many equivalents to the exemplary embodiments described specifically herein by using no more than routine experimentation. Such equivalents are intended to be encompassed by the scope of the present invention and the appended claims.
