Patent Application
20120016424
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 engaged to the receiver and defines a pathway that extends proximally from the receiver. The connecting member is movable along the extension to the receiver of the bone anchor. The extension is removable from 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 enagageable to a spinal column. The anchor assembly includes a bone anchor with a bone engaging portion and a receiver for receiving a connecting member. An extension is engaged to and extends from the receiver. The extension includes a pair of arms that define a space between the arms that extends proximally from a proximal end opening of the receiver. The connecting member is positionable into the space and movable along the arms through a proximal end opening of the receiver and into the receiver. The connecting member can then be secured to the bone anchor with an engaging member engaged to the receiver. The extension is removable from the receiver so that the anchor assembly has a low-profile in the patient post-surgery.
In another form, 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 bone anchor so that the extension extends proximally from the bone anchor. The anchor assemblies are implanted into the patient while the extensions extend proximally away from the implantation location. The extensions guide the placement of a connecting member from a position remote from implantation location to a position more adjacent the spinal column or to 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 anchors after implantation of the connecting member so that the connecting member implantation and extension removal is accomplished without invasively accessing the patient's body.
Referring to
In one embodiment, arms 20, 22 include a length sufficient to locate proximal end 16 outside the skin and tissue of the patient when bone anchor 20 is secured to bony structure within the patient. In the illustrated embodiment, arms 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 arms 20, 22. In an alternative embodiment, a proximal portion 28′ is provided that extends between and connects arms 20, 22 to close the proximal end opening, requiring the connecting member to be positioned into space 26 from the sides of arms 20, 22 with the connecting member 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. 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 the 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 portions 66, 68 sized and spaced to accommodate connecting member 100 and engaging member 90 therebetween. Arms 20, 22 of extension 14 form an elongated extension of respective ones of the side portions 66, 68, and are joined therewith along the outer surface of the respective side portion 66, 68. Arms 20, 22 include a length extending proximally from side portions 66, 68 so that the proximal ends of arms 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 extensions 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 to the proximal end of the extension.
Side portions 66, 68 each include an internal thread profile 67, 69 to threadingly receive engaging member 90. Receiver 60 includes a hole 64 extending on longitudinal axis 24 that opens through a distally facing surface 58 of receiver 50. Hole 64 is sized and shaped to receive bone engaging portion 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 64 is surrounded by a retaining member 74. Retaining member 74 can be C-ring, washer, lip, or flange formed separately from or as an integral part of receiver 50 to support head 54 while allowing bone engaging member 52 to be positioned in any one of an infinite number of angular positions relative to receiver 50 and longitudinal axis 24. Other embodiments contemplate other engagement relationships between the bone engaging member 52 and receiver 50. In one embodiment, bone engaging member 52 is formed as a single, integral unit with receiver 50 and extends along longitudinal axis 24 in a co-axial arrangement. In another embodiment, bone engaging member 52 is captured in receiver 50 with a retaining member that allows pivotal movement relative to receiver 50 in a single plane or in a predetermined number of planes or directions relative to longitudinal axis 24.
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 70 positioned on and around the proximal side of head 54. Crown 70 includes a proximal side that projects into a passage 72 defined between side portions 66, 68. When engaging member 90 is threadingly engaged to receiver 50, it pushes connecting member 100 in passage 72 against the proximal side of crown 70. Crown 70 is in turn pushed against the proximal side of head 54, which seats head 54 firmly against retaining member 74. The proximal side of head 54 may include a plurality of ridges or grooves that bite into a distally facing surface of crown 70 to enhance locking of bone engaging member 52 in position in receiver 50. In another embodiment, at least some motion between the receiver 50 and bone engaging member 52 is maintained by crown 70 when connecting member 100 is secured in receiver 50 with engaging member 90. Still other embodiments contemplate that crown 70 can be omitted and that connecting member 100 is seated directly against head 54 of bone engaging member 52 or against a bottom surface 55 of receiver 50 that extends on a distal side of passage 72 between side portions 66, 68.
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.
Extension 14 includes arms 20, 22 extending parallel to one another distally from proximal end 16 to a distal ring portion 40 that extends around receiver 50. Arms 20, 22 include planar facing surfaces 21, 23 that extend parallel to one another and parallel to longitudinal axis 24 that define space 26 therebetween. In addition, arms 20, 22 include outer, oppositely facing surfaces 25, 27, respectively, that define a convex curvature extending around longitudinal axis 24 and a generally linear profile paralleling longitudinal axis 24. The curved outer surfaces 25, 27 provide a smooth surface contour that holds back tissue from encroaching into space 26 while minimizing trauma to the tissue pressing against arms 20, 22.
Outer surfaces 25, 27 extend generally parallel to longitudinal axis 24 from proximal end 18 to a location 41, 43 of arms 20, 22 along the respective side portions 66, 68 of receiver 50 aligned proximally and distally with passage 72. Outer surfaces 25, 27 taper distally from these locations 41, 43 to ring portion 40. The tapering thickness of the wall of extension 14 continues to distal end 18. Extension 14 is positioned around receiver 50 so that most-distal part of distal end 18 is spaced proximally from the distally facing surface 58 of receiver 50 along the sides of side portions 66, 68. As explained further below, this facilitates removal of extension 14 from receiver 50, and allows pivoting of bone engaging portion 52 relative to receiver 50 without interference from extension 14.
Extension 14 includes ring portion 40 that extends completely around receiver 50 below the passage 72 of receiver 50. The wall thickness of ring portion 40 tapers distally to a minimum width at around ring portion 40. Extension 14 is made from a material with a thickness and/or material properties that allows arms 20, 22 of extension 14 to be separated from one another at a separation location, such as where ring portion 40 aligns with opening of passage 72 at the opposite sides of receiver 50. The surgeon applies sufficient force by twisting or pulling arms 20, 22 to sever arms 20, 22 at the minimum cross-section of extension 14 provided by ring portion 40 at the separation location. In one embodiment, ring portion 40 includes scoring 80, slits or other reduced wall thickness configuration at the separation locations. The scoring provides a separation region to facilitate splitting of ring portion 40 to allow arms 20, 22 to be separated from one another and from the respective side portion 66, 68.
Extension 14 also includes features to facilitate guiding and placement of connecting member 100 into passage 72 of receiver 50. Arms 20, 22 include a receiving portion along parallel surfaces 21, 23 that form a location to receive and provide initial guidance of the placement of connecting member 100 into and along space 26. Arms 20, 22 also include a tapered portion to direct connecting member 100 from its initial placement through space 26 into alignment with passage 72. Arm 20 includes a tapered surface portion 31 extending distally from inner surface 21 and arm 22 includes a tapered surface portion 33 extending distally from inner surface 23. Tapered surfaces portions 31, 33 converge toward one another and join with the respective alignment surface portions 35, 37, respectively, at or near the proximal end of receiver 50. Alignment surface portions 35, 37 extend parallel to one another to form an extension of inner surfaces of side portions 66, 68 defining passage 72 on opposite sides of receiver 50. Alignment surface portions 35, 37 are joined by concave connecting portion 39 that extends around and forms an extension of bottom surface 55 of receiver 50 on opposite sides of receiver 50.
As shown in
Extension 14 also includes a concave recess 32, 34 in respective ones of the tapered surface portions 31, 33. Recesses 32, 34 are concavely curved in a direction between the elongated sides of the respective arm 20, 22 so that the recess aligns with respective ones of side portions 66, 68. Recesses 32, 34 maintain the opening defined between the proximal ends of side portions 66, 68 through which connecting member 100 and engaging member 90 are received. This also allows alignment surfaces 35, 37 of arms 20, 22 to extend around the opposite sides of side portions 66, 68 where passage 72 opens and form an extension of passage 72 without interfering with placement of engaging member 90 through the proximal end opening of receiver 50.
In use, extension 14 is positioned around 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. Side portions 66, 68 can include respective ones of detents 92, 94 so that a portion of the respective arm portion 20, 22 extends therein to enhance the axial engagement of extension 14 to receiver 50. 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 arms 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 and resorbable 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, or other feature to allow attachment of a surgical reduction instrument to mechanically facilitate placement of connecting member 100 into passage 72 of receiver 50 and/or to align a vertebra attached to extension 14.
In yet other embodiments, at least a portion of extension 14 is made from a biocompatible resorbable material. For example, arms 20, 22 each include scoring, a reduced thickness arrangement, material weakness, or other removal feature that is located at or adjacent to the proximal end of the respective side portion 66, 68 of receiver 50. This allows the majority of the length of each arm 20, 22 to be removed from receiver 50, while the portion of extension 14 including ring portion 40 and the part of arms 20, 22 along the side portions 66, 68 remain engaged to receiver 50 post-operatively, i.e. after the surgical procedure is completed and the incision or opening into the patient is closed. At least these post-implantation parts of extension 14 can be made from a resorbable material to resorb post-operatively over time.
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.
