Patent Application
20120109208
Various devices and methods for stabilizing bone structures have been used for many years. For example, the fracture of an elongated bone, such as a femur or humerus, can be stabilized by securing a plate to the fractured bone across the fracture. The plate extends across the fractured area and thus stabilizes the fractured components of the bones relative to one another in a desired position. When the fracture heals, the plate can be removed or left in place, depending on the type of plate that is used.
Another type of stabilization technique uses one or more elongated rods extending between components of a bony structure and secured to the bony structure to stabilize the components relative to one another. The components of the bony structure are exposed and one or more bone engaging fasteners are placed into each component. The elongated rod is then secured to the bone engaging fasteners in order to stabilize the components of the bony structure.
One problem associated with the above described stabilization structures is that the skin and tissue surrounding the surgical site must be cut, removed, and/or repositioned in order for the surgeon to access the location where the stabilization device is to be installed. This repositioning of tissue causes trauma, damage, and scarring to the tissue. There are also risks that the tissue will become infected and that a long recovery time will be required after surgery for the tissue to heal.
Minimally invasive surgical techniques are particularly desirable in, for example, spinal and neurosurgical applications because of the need for access to locations deep within the body and the presence of vital intervening tissues. The development of percutaneous minimally invasive spinal procedures has yielded a major improvement in reducing recovery time and post-operative pain because they require minimal, if any, muscle dissection and can be performed under local anesthesia. These benefits of minimally invasive techniques have also found application in surgeries for other locations in the body where it is desirable to minimize tissue disruption and trauma. However, there remains a need for further improvements in instruments, systems and methods for stabilizing bony structures using minimally invasive techniques.
There are provided systems and methods for positioning a connecting member adjacent the spinal column that include at least one anchor assembly having an anchor engageable to bony structure and a receiver for receiving the connecting member. An extension is removably engaged to the receiver and extends proximally from the receiver to a proximal end located outside the patient. The extension and at least a portion of the receiver are removable from the remaining portion of the receiver of the bone anchor after the connecting member is positioned in the receiver to provide a low profile anchor assembly when the connecting member and bone anchor are finally implanted in the patient.
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.
Anchor assemblies are provided that are engageable to a bony structure, such as one or more vertebrae of a spinal column, to guide placement of one or more connecting members from a location outside patient, or within the patient but remote from an implantation location, to or more adjacent to an implantation location in the patient. The connecting member can be an elongated spinal rod, tether, bar, plate, wire, or other suitable device that is to be engaged to one or more bone anchors. The anchor assemblies are particularly suited for minimally invasive surgical procedures, but are not restricted to such procedures. Furthermore, although its use and application is described with regard to spinal surgery, applications in surgeries other than spinal surgery are also contemplated.
In one form, surgical systems are provided that include at least one anchor assembly engageable to a spinal column. The anchor assembly includes a bone anchor with a bone engaging portion and a receiver for receiving the connecting member. An elongated extension is engaged to and extends proximally from the receiver to a proximal end located so that it is readily accessible by the surgeon. The extension includes first and second elongated extension members that define a space between the elongate members that extends proximally from a proximal end opening of the receiver located between the elongate members. The elongate members can provide a path for insertion of the connecting member that is referenced to the location of the receiver, or a platform for engagement of an inserter to proximal ends of the elongate members so that the inserter is references to the receiver locations within the patient. The connecting member is positionable into the space defined by the elongate members and movable along the extension through a proximal end opening of the receiver and into the receiver. The connecting member can also be positioned directly into the receiver from a side of the receiver. The connecting member can then be secured to the bone anchor with an engaging member engaged to the receiver. The elongate members of the extension are removable from the receiver so that the anchor assembly has a low-profile in the patient post-surgery. In one embodiment, a proximal portion of the receiver member is separated from a distal portion of the receiver to remove the elongate member mounted to the proximal portion of the receiver.
In another aspect, surgical systems are provided that include at least a pair of anchor assemblies engaged to the spinal column. The anchor assemblies each include an extension engaged to a receiver of the bone anchor so that the extension extends proximally from the receiver. The anchor assemblies are implanted into the patient while the extensions extend proximally away from the implantation location. The extensions provide a platform for engagement of an inserter, or can serve as a guide for the placement of a connecting member from a position remote from implantation location to a position more adjacent the spinal column, such as the implantation location. The extensions are configured so that when the connecting member is guided adjacent to the spinal column, the connecting member extends through the bone anchors of the anchor assemblies. The connecting member is secured to the bone anchor assemblies and provides stabilization of the spinal column segment to which the bone anchors assemblies are attached. The extensions are removed from the bone anchor assemblies after implantation of the connecting member so that the connecting member implantation and extension removal is accomplished without invasively accessing the patient's body. In one embodiment, a portion of the receiver member to which the extension is mounted is separated from the remaining portion of the receiver in order to remove a corresponding member of the extension engaged thereto. In a further embodiment, a connecting member inserter is mounted to the proximal end of one or more the extensions to reference the connecting member to the anchor assembly locations and to guide placement of the connecting member to the bone anchor assemblies in the patient.
Referring to
In one embodiment, elongate members 20, 22 include a length sufficient to locate proximal end 16 outside the skin and tissue of the patient when bone anchor 12 is secured to bony structure within the patient. In the illustrated embodiment, elongate members 20, 22 form a proximal opening 28 therebetween to allow the connecting member to be placed through the proximal end opening 28 into space 26 between elongate members 20, 22. In an alternative embodiment, a proximal portion can be provided that extends between and connects elongate members 20, 22 to close the proximal end opening, requiring connecting member 100 to be positioned into space 26 from the side opening between members arms 20, 22 with connecting member 100 oriented in a length-wise manner that is transverse to longitudinal axis 24.
Referring further to
In the illustrated embodiment, receiver 50 forms a saddle that houses a portion of bone engaging member 52 and connecting member 100. Receiver 50 receives the connecting member 100 therethrough in an orthogonal or transverse orientation to longitudinal axis 24 and in an orientation that extends generally parallel with the spinal column. In one embodiment, connecting member 100 is an elongated spinal rod, and bone anchor 12 includes a bone screw portion extending from a distally facing end of receiver 50. The bone screw portion can be a multi-axial type screw pivotally received and carried by receiver 50 so that the receiver and bone screw are pivotal relative to one another. In another embodiment, the bone screw portion is non-pivotal or fixed relative to the receiver. Furthermore, connecting member 100 can be received in, on, or about receiver 50 for engagement thereto with an engaging member 90. Engaging member 90 is shown in
In the illustrated embodiment, receiver 50 includes a pair of opposite side arms 66, 68 sized and spaced to accommodate connecting member 100 and engaging member 90 therebetween. Arms 66, 68 each include a removable break-off portion 67, 69 extending to a proximal end of receiver 50. Elongate members 20, 22 of extension 14 form an elongated extension of respective ones of the side arms 66, 68, and are mounted thereto along the outer surface of the respective break-off portion 67, 69. Break-off portions 67, 69 are joined to a respective distal portion 70, 72 of arms 66, 68 at a separation location formed by a reduced thickness in the respective arm 66, 68 at break-off recess 71, 73, respectively. Recesses 71, 73 extend into and form an indentation in the outer surfaces of arms 66, 68 and a groove in the inner surfaces of arms 66, 68. Break-off recesses 71, 73 provide an area of reduced wall thickness along arms 66, 68 so that the break-off portions 67, 69 can be removed by application of a threshold torque and/or shear force to the respective elongate member 20, 22 mounted thereto. When the break-off portion 67, 69 is separated, it is removed by withdrawing the respective elongate member 20, 22 from the patient since, as discussed further below, the break-off portion 67, 69 is mounted to the elongate member 20, 22. In one embodiment, recesses 71, 73 extend completely about the respective arm 66, 68, including its outer and inner surfaces, and interrupt the inner thread profiles 74, 76 thereof. Further examples of suitable receivers are disclosed in U.S. Patent App. Pub. No. 2007/0191840, which is incorporated herein by reference in its entirety.
Elongate members 20, 22 each include a length extending proximally from break-off portions 67, 69 so that the proximal ends of elongate members 20, 22 are located outside the patient when anchor 12 is engaged to the spinal column. In one embodiment, this length is at least 30 millimeters. In another embodiment, the length of extension members 20, 22 is at least 50 millimeters. Other lengths are also contemplated. In one specific embodiment, the length is at least 100 millimeters, and extends about 120 millimeters from the anchor 12 to the proximal end 16 of extension 14.
Arms 66, 68 each include an internal thread profile 74, 76 that extends along the inner surfaces of the break-off portions 67, 69 and distal portions 70, 72 of arms 66, 68 to threadingly receive and engage engaging member 90. In other embodiments, break-off portions 67, 69 do not include any thread profile. Receiver 50 includes a hole 78 extending on longitudinal axis 24 that opens through a distally facing surface 58 of receiver 50. Hole 78 is sized and shaped to receive bone engaging member 52 therethrough while supporting head 54 of bone engaging member 52 in receiver 50. Near the distally facing surface 58 at the bottom of receiver 50, hole 78 is surrounded by a retaining member 80, as is further shown in
In the particular illustrated embodiment of bone engaging member 52, it includes an initial configuration that allows pivoting movement in receiver 50 and is thereafter rigidly or semi-rigidly fixed in position when connecting member 100 is seated in receiver 50. Receiver 50 includes a crown 82, also shown in
Bone engaging portion 52 is shown as a bone screw with proximal head 54 and an elongated threaded shaft 56 extending distally from head 54 located in receiver 50. Other embodiments contemplate other forms for bone engaging member 52, such as a hook, post, tack, cerclage, staple, anchor, or other suitable bone engaging structure. Bone engaging member 52 can be a separate member that is connected with receiver 50, or formed as an integral, one-piece construct with receiver 50.
Referring further to
Outer surfaces 25, 27 extend generally parallel to longitudinal axis 24 from proximal end 16 to distal end 18. Elongate members 20, 22 are substantially identical to one another, so the description of mounting structure 30 of elongate member 20 applies to mounting structure 32 of elongate member 22. However, other embodiments contemplate embodiments in which elongate members 20, 22 include differing configurations and/or mounting structures. Elongate members 20, 22 include a width that increases along mounting structures 30, 32 to accommodate placement over the respective break-off portion 67, 69. Mounting structures 30, 32 include a lip 34 projecting inwardly therefrom that forms a distally facing surface that contacts the proximal end of the respective break-off portion 67, 69 to limit distal advancement of the elongate member 20, 22 along the respective break-off portion 67, 69. The reduced width proximal portion of members 20, 22 extending proximally from the respective mounting structure 30, 32 provides a low profile footprint that minimizes intrusion into the adjacent tissue. Thus, mounting structures 30, 32 can include a width W1 that is more than 0 percent and up to about 50% larger than width W2 of the proximal portion of member 20, 22. However, embodiments in which width W2 is the same or greater than width W1 are not precluded.
Referring further to
Extension 14 also includes features to facilitate guiding and placement of connecting member 100 into passage 84 of receiver 50. Elongate members 20, 22 include a receiving portion along inner surfaces 21, 23 that can form a location to receive and provide initial guidance of the placement of connecting member 100 into and along space 26. Elongate members 20, 22 also direct connecting member 100 from its initial placement through space 26 into alignment with the space between arms 66, 68 and passage 84. As discussed further below, if connecting member 100 is not entirely located in passage 84, engaging member 90 can be threaded along the inner thread profiles 74, 76 of arms 66, 68 to contact and displace connecting member 100 into passage 84. Providing arms 66, 68 with threaded break-off portions 67, 69 provides a greater range of locations along the arms 66, 68 of receiver 50 through which connecting member 100 can be received and then reduced into passage 84 with engaging member 90.
As shown in
In use, extension 14 is positioned on receiver 50 so that anchor assembly 10 is provided, at least initially to the surgeon, as a unit that includes anchor 12 and extension 14 for simultaneous implantation into the patient. In one embodiment, extension 14 is made from a radiolucent material so that radiographic or fluoroscopic visualization of connecting member 100 is not obscured between members 20, 22, allowing the surgeon to monitor advancement of connecting member 100 along extension 14 and through the tissue of the patient during the procedure. Examples of suitable materials for extension 14 include polyetheretherketone (PEEK), plastics, polymers, or aluminum, for example. Other materials are also contemplated, including radio-opaque materials. Still other embodiments contemplate that extension 14 is made from a non-conductive material so that probes, taps, drivers and other instruments that employ electrical signals for neuro-stimulation are not shunted through extension 14 to the tissue around extension 14. Extension 14 may also include one or more holes, rockers, notches, or other feature to allow attachment of an inserter or a surgical reduction instrument to mechanically facilitate placement of connecting member 100 into passage 84 of receiver 50 and/or to align a vertebra attached to extension 14.
Referring to
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.
