Patent Application
20110172715
Orthopedic devices such as spinal rods, plates, tethers, staples and other devices can be secured along the spinal column between one or more vertebral levels to stabilize the one or more vertebral levels. While surgical procedures along the spinal column for placement of such devices are becoming less invasive, the decrease in space available in the approach to the surgical site and at the surgical site for handling and manipulating of the devices increases the difficulty in maneuvering, maintaining and finally positioning of the devices during the procedure. Furthermore, the small and intricate parts commonly associated with such orthopedic devices can increase the difficulty of the installation procedure. Accordingly, systems and devices which facilitate placement of orthopedic devices along the spinal column are desirable.
There are provided systems and methods for positioning a connecting member adjacent the spinal column that include at least two anchor assemblies having an anchor engageable to bony structure and an extended receiver having a guide portion and an implantation portion. A connecting member is movable along the guide portion from a location outside the patient to the implantation portion in the patient, where the connecting member is secured to the anchor assembly with an engaging member. The guide portion is formed as a single unit with but separable from the implantation portion to provide a modified low-profile anchor assembly after implantation of the connecting member.
These and other aspects will be apparent from the following description of the illustrated embodiments.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated devices and described methods, and any such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Referring to
In one embodiment, each of the at least a pair of extended receivers 50 includes a distal implantation portion 52 adjacent the respective anchor 120 for receiving the connecting member 100 in an implantation position to stabilize one or more vertebral levels. A proximal guide portion 54 extends from opposite sides of the implantation portion 52 for guiding the connecting member 100 from a location outside the patient to its implantation location in the implantation portion 52 adjacent the anchors 120. The guide portion 54 defines a channel therethrough that opens along opposite sides of the extended receiver 50, and extends from the proximal end of the extended receiver 50 to the implantation portion 52. In another embodiment, guide portion 54 is formed as a single unit with implantation portion 52 portion at a break-off segment therebetween. The break-off segment provides a separation location between the implantation portion 52 and the guide portion 54 so that when sufficient force is applied to guide portion 54 it can be removed to modify the extended receiver 50 to an implantation configuration. In another embodiment, the at least a pair of anchor assemblies 45 includes three anchor assemblies 45.
In one embodiment, the connecting member 100 is an elongated rod and the anchors 120 are bone screws. The bone screws can be a multi-axial type screw positioned in the implantation portion 52 of extended receiver 50 so that the receiver and bone screw are pivotal relative to one another. In another embodiment, the bone screws are non-pivotal or fixed relative to the receiver. Connecting member 100 can be received in, on, or about the implantation portion 52 of extended receiver 50 for engagement thereto. The connecting member 100 can be rigid, semi-rigid, flexible, elastic, non-compression load bearing, or of other suitable form for extending between and stabilizing adjacent portions of the spinal column when secured thereto.
In
Referring now to
Implantation portion 52 forms a saddle that houses anchor 120 and receives the connecting member 100 therethrough in an orthogonal or transverse orientation to central axis 51 and in an orientation generally parallel with the spinal column. Implantation portion 52 includes a pair of opposite side members 66, 68 sized and spaced to accommodate elongate member 100 therein. Arms 55, 57 form an extension of respective ones of the side members 66, 68, and are singularly formed therewith at the respective break-off region 56, 58. Arms 55, 57 include a length extending proximally from side members 66, 68 so that the proximal ends of arms 55, 57 are located outside the patient when anchor 120 is engaged to the spinal column. In one embodiment, this length is at least 30 millimeters. In another embodiment, the length of arms 55, 57 is at least 50 millimeters.
As further shown in
In the particular illustrated embodiment of implantation portion 52, implantation portion 52 includes an inner groove 74. As illustrated, groove 74 extends about side members 66, 68 and around hole 64. Groove 74 is configured to accommodate snap ring 76 in a compressed condition. Groove 74 can have a height that is, in one form, greater than a thickness of snap ring 76. Snap ring 76 can retain a crown 78 in implantation portion 52 about the proximal side of head 122 of anchor 120. Connecting member 100 is seated against crown 78 when secured in implantation portion 52 with engaging member 90. In one embodiment, seating of crown 78 locks anchor 120 in position relative to extended receiver 50. In such an embodiment, crown 78 and/or head 122 can include engagement structures that engage one another to provide the locked arrangement. In a further embodiment, at least some motion between the connecting member and anchor 120 is maintained by crown 78 when connecting member is secured in implantation portion 52. Still other embodiments contemplate that crown 78 can be omitted and that the connecting member 100 is seated directly against head 122 of anchor 120.
Referring now to
In
In
In
Break-off regions 56, 58 provide an area of reduced wall thickness adjacent the distal end of the respective arm 55, 57 that extends between the arm 55, 57 and the respective side member 66, 68. Break-off regions 56, 58 can be located between the internal thread profiles defined by side members 66, 68 and the adjacent arm 55, 57. In the illustrated embodiment, the outer surface of each of the break-off regions 56, 58 forms a concave depression or recess that extends completely about arm 55, 57 and the respective adjacent side member 66, 68. Each of the arms 55, 57 is joined to the respective side member 66, 68 with a break-off region having a wall thickness that is reduced comparatively to an adjacent wall thickness of the respective arm and the respective side member. Other embodiments contemplate other techniques for reducing the wall thickness to provide a break-off region, such as by providing perforations or undercuts between the arms 55, 57 and the respective adjacent side member 66, 68. In any event, the break-off regions provide a separation location that is generally uniform and substantially free of sharp of jagged edges after separation of the respective arms 55, 57. Other embodiments contemplate a break-off region that is in a thread-free-zone.
It may also be desirable to provide a desired alignment between vertebrae by reducing the connecting member into the implantation portion of the extended receivers of the anchor assemblies. For example, the vertebrae may be misaligned as a result of spondylolisthesis, anatomical differences between the vertebrae, or some other condition. Also, there may be slight misalignments between the receiver members that make manually positioning the connecting member into each of the receiver members difficult. In such situations, the engaging members 90 can be employed to provide a mechanical advantage to seat the connecting member in the implantation portions as the engaging members are threadingly advanced along the arms 55, 57 and into the side members 66, 68.
System 40 may employ various instruments to facilitate selection of the connecting member, placement of the connecting member through the extenders and to the anchors, securement of the connecting member to the anchors, and manipulation of the vertebrae and/or anchors to a desired position or condition. For example, a driver can be provided that is positionable through any one of the extended receivers to engage the anchor to the vertebra. A driver for positioning the engaging member through the extended receiver and into engagement with the implantation portion can also be provided. A counter-torque device such as a wrench or handle arm, can be secured to any one of the extended receivers to hold the extended receiver in position relative to the anchor attached thereto as torque is applied to seat the engaging member into contact with the connecting member in the implantation portion of the extender receiver. Compressors and distractors can also be provided to facilitate application of a compressive or distraction force between anchors before final attachment of the connecting member to each anchor. Calipers can be provided to measure a distance between the outermost extended receivers for sizing of the length of the connecting member to be positioned between the anchors. A holding instrument can be provided that is adapted to grasp and hold the connecting member placed between the extenders, and can be employed to facilitate moving the connecting member distally along the extenders toward and into the anchors. A reduction instrument can be provided that is positionable along or about the extender receiver to provide a mechanical advantage for reduction of the connecting member into one or more of the implantation portions of the extended receivers.
Examples of suitable connecting members that extend between the anchors include rods, wires, tethers, strands, cables, bands, plates, and struts. The connecting member may include one component, or may include two or more components. One embodiment connecting member is shown in
Each of the anchor assemblies can be attached to the respective vertebra using any one of a number of techniques. By way of example and not limitation, one embodiment of a procedure contemplates an incision over the target location of the spinal column, and that the skin and tissue are sequentially dilated to provide a minimally invasive pathway for anchor assembly insertion and engagement to each vertebra.
In another example procedure, a cannulated outer needle with an inner stylet can first be inserted to the targeted regions of the vertebrae, such as the pedicle in a posterior procedure, and aligned to provide the desired trajectory into the pedicle. Alignment can be monitored and checked with any viewing system, including radiographic, fluoroscopic, microscopic, endoscopic, loupes, naked eye, or any other suitable viewing system or instrument. After the cannulated needle and stylet are inserted into the vertebra, the inner stylet is withdrawn with the cannulated outer needle remaining engaged to the vertebra. A guidewire is positioned through the cannulated outer needle and engaged in the vertebra. The outer needle is then withdrawn so that the guidewire remains in place. The tissue around the guidewire is sequentially dilated with a number of tubular dilators of increasing diameter. When desired opening size is obtained, the guidewire and inner dilators are removed and the last inserted dilator provides a protected pathway to the pedicle or other targeted portion of the vertebra. The anchor assembly can then be positioned through the dilated pathway and engaged to the vertebra. The procedure is then repeated to position the desired number of anchor assemblies, whether it be two, three or four or more. Incisions can be made between the adjacent anchor assemblies to provide a pathway for insertion of the connecting member. Alternatively, the connecting member can be inserted axially into one of the extended receivers and then manipulated below the skin and musculature by rotating it to extend between the anchor assemblies, avoiding incisions through the skin and musculature between the anchor assemblies.
In another embodiment, the anchor assemblies are inserted percutaneously without sequential dilation. The guidewire is positioned as discussed above, and the anchor can be cannulated for positioning over the guidewire. The anchor and extended receivers are assembled and then positioned together over the guidewire, which guides the anchor assembly to the pedicle or other targeted portion of the vertebra. A cannulated driver tool is positioned over the guidewire and through the extended receiver to engage the head of the anchor and drive it into the vertebra.
In another embodiment, a pathway to the target location is prepared as discussed above. The guidewire and any dilators are removed. A cannula or other suitable retractor may remain in the incision to provide a protected pathway to the target location, although direct insertion through a micro-incision is also contemplated. An anchor driver is inserted through the extended receiver and engaged to the head of the anchor. The anchor driver can maintain the anchor in rigid alignment with the axis of the extended receiver if the anchor assembly is multi-axial. The anchor and extended receiver are inserted percutaneously to the target location of the vertebra, such as the pedicle. Insertion and alignment of the anchor assembly may be monitored fluoroscopically or with any suitable surgical navigation system. The anchor is then engaged to the vertebra at the target location with the extended receiver extending proximally therefrom through the skin level of the patient. Anchor assembly insertion and engagement is repeated for each vertebra along the instrumented levels.
In any embodiment, placement of the anchor assemblies can be conducted through a micro-incision, through a retracted opening formed in the tissue approaching the targeted location on the vertebra, or through a tubular member providing a protected passageway to one or more of the adjacent vertebrae. It is also contemplated that nerve monitoring can be performed through the extended receivers to guide placement of the anchors in the appropriate locations in the vertebrae. In one embodiment, the anchor assemblies are engaged to pedicles of the respective vertebrae. Each pedicle can be drilled and, if necessary or desired, tapped to receive a threaded screw portion of the anchor assembly. Formation and tapping of the holes in the pedicles can be monitored with an electrical stimulus applied through a guidewire, tap, probe, or anchor driver prior to and during anchor assembly insertion. Response of the patient can be monitored to determine that anchor placement does not impinge upon any nerves. The guidewire, tap, probe, driver or other instrument can be placed through a sleeve or dilator made from plastic material to provide a non-conductive insulator. In still a further form, an electrical signal is applied through the anchor assembly to guide placement of the anchor into the vertebrae without impinging on neural structures. The extended receivers can be insulated with a protective, non-conductive coating, sleeve or other layer to prevent the current from straying.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, and that all changes and modifications that come within the spirit of the invention are desired to be protected.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11341274 | Jan 2006 | US |
| Child | 13073325 | US |
