Patent Application
20090131982
This invention generally relates to a method and apparatus for changing spinal alignment to treat spinal column deformity.
Human spines are formed from vertebrae spaced by intervertebral discs arranged in a gently curving column. Viewed from the side, the column has several curves defining different regions of the spine. Abnormal spinal curvatures occasionally occur in individuals. These abnormal curvatures of the spine include scoliosis (lateral curvature), kyphosis (exaggerated curvature usually in an upper portion of the spine), lordosis (exaggerated curvature usually in a lower portion of the spine), and combinations of these conditions. Although these abnormal curvatures may be cosmetically undesirable, in some cases they can lead to organ problems, reduce mobility of the individual and cause significant pain. Thus, correction of the abnormal spinal curvatures is frequently desirable.
Spinal column deformities are treated with a variety of approaches. In some cases, spinal implants are used to rigidly fix the vertebrae relative to one another. When the vertebrae are held in a rigid position and bone graft material is added, the vertebrae fuse leading to loss of spinal mobility and potentially accelerating degeneration of areas of the spine adjacent the fused portion. Thus, fusion is undesirable in many cases, and there is a need for a method and apparatus for correcting abnormal spinal curvatures without fusing vertebrae.
Because the abnormally curved spines can be out of alignment laterally, as well as forward and rearward, there is a need for a method and apparatus enabling surgeons to modify spinal column alignment simultaneously in multiple directions. Most conventional methods for treating spinal column deformities without fusion are only capable of correcting alignment in one direction at a time. Further, it is generally recognized that corrective methods and apparatus should be minimally invasive to reduce an opportunity for complications during and following the procedures, and to reduce healing times. In addition, there is a need for a method and apparatus allowing progressive adjustment of vertebrae to obtain a desirable optimal alignment of the spinal column for the patient.
The present invention relates to an anchor for attaching an elongate member to bone. The anchor comprises a longitudinal shaft having a tip at one end adapted to enter bone. A thread extends along the shaft for advancing the shaft into the bone and holding the shaft in place in the bone. The anchor also includes a head mounted on the shaft at a position spaced from the tip. Further, the anchor comprises a plurality of connector mounts spaced along the head. Each of the mounts is adapted to connect the elongate member to the head.
The invention also relates to a system for changing alignment of vertebrae of a spinal column. The system comprises a plurality of elongate members. Each of the members has a length sufficient to span at least one pair of vertebrae in the spinal column. In addition, the system includes a plurality of anchors. Each anchor includes an elongate threaded shaft having a tip at one end adapted to enter bone and a head on the shaft at a position spaced from the tip. The head has a plurality of connector mounts spaced along the head. Each mount is adapted to connect one of the elongate members to the head.
In yet another aspect, the invention includes a system for changing alignment of vertebrae of a spinal column. The system comprises a plurality of elongate members. Each of the members has a length sufficient to span at least one pair of vertebrae in the spinal column. The plurality of elongate members includes a first member having a first stiffness and a second member having a second stiffness greater than the first stiffness. Further, the system includes a plurality of anchors. Each anchor includes a head having a plurality of connector mounts spaced along the head. Each mount is adapted to connect one of the elongate members to the head.
Still further, the invention includes a system for changing alignment of vertebrae of a spinal column. The system comprises a plurality of elongate rods. Each rod has a length sufficient to span at least one pair of vertebrae in the spinal column. The system also comprises a plurality of anchors. Each anchor includes a head having a plurality of connector mounts spaced along the head. Each mount is adapted to connect one of the rods to the head.
In a further aspect, the invention includes a method of changing alignment of vertebrae of a spinal column. A first anchor is attached to an upper vertebra and a second anchor is attached to a lower vertebra. At least two rigid rods are connected to both the first anchor and the second anchor so each of the rods spans between the upper vertebra and the lower vertebra.
Moreover, the invention includes a method of changing alignment of vertebrae of a spinal column in which a first anchor is attached to an upper vertebra and a second anchor is attached to a lower vertebra. A rod is connected to both the first anchor and the second anchor so the rod spans between the upper vertebra and the lower vertebra. A flexible tether is connected to both the first anchor and the second anchor so the tether spans between the upper vertebra and the lower vertebra.
Other aspects of the present invention will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring now to the drawings and in particular
The anchor 20 generally comprises a longitudinal shaft 22 having a tip 24 at one end adapted to enter bone. In one embodiment, the tip 24 is rounded to prevent inadvertent damage to tissue as the anchor 20 is being installed in the bone. A screw thread 26 extends along the shaft 22 for advancing the shaft into the bone and holding the shaft in place in the bone. As shown in
As further illustrated in
Although the shaft 22 may have other dimensions without departing from the scope of the present invention, in one embodiment the shaft has a length of between about 20 millimeters (mm) and about 65 mm, and a diameter of between about 3.5 mm and about 7 mm. Shafts 22 having dimensions in these ranges have been found to be particularly desirable for anchoring elongate members to a vertebra by screwing the anchors lengthwise into a pedicle of the vertebra. Further, although the anchor 20 may be made of other materials without departing from the scope of the present invention, in one embodiment the anchor is made of metal such as titanium or stainless steel. Although the anchor 20 may be made by other processes without departing from the scope of the present invention, in one embodiment the anchor is made by machining a metal or synthetic polymer.
The anchor 20 may include or work in combination with a fastener for fastening the corresponding elongate member to the head 28. In some embodiments, the fasteners are operatively connected to the mount. For example, the opposing walls of the mount 32 include threading 34 for receiving a conventional set screw 36 as shown in
The system 50 also includes two anchors 20. A first anchor 20 (e.g., an upper anchor) is mounted on an upper vertebra VU and a lower anchor (e.g., a lower anchor) is mounted on a lower vertebra VL. As will be appreciated by those skilled in the art, more than two anchors may be used to attach a single elongate member (e.g., member 54) to multiple vertebrae or more than one anchor may be used to attach an elongate member in more than one place on a single vertebra. Although the anchors 20 shown in
As further illustrated in
In addition, those skilled in the art will appreciate that different mounts may be used other than those described above. Further, different combinations and types of elongate members may be used without departing from the scope of the present invention. For example, one contemplated embodiment of a system of the present invention is illustrated in
As will be appreciated by those skilled in the art, the anchors and systems described above may be used to change alignment of vertebrae of a spinal column. One method of use includes attaching a first anchor to an upper vertebra and attaching a second anchor to a lower vertebra using standard surgical procedures. For example, a pilot hole may be bored or drilled in the vertebra. The anchors may be threaded into the pilot hole using a wrench. Two or more rigid rods are connected to both the first anchor and the second anchor so each of the rods spans between the upper vertebra and the lower vertebra. Although the rods span adjacent vertebrae in one embodiment, it is contemplated that the rods may span and be connected to non-adjacent vertebrae. It is further contemplated that the more than two anchors and/or more than two rods may be used with this method.
In another embodiment, alignment of vertebrae of a spinal column is altered by attaching a first anchor to an upper vertebra and a second anchor to a lower vertebra as before. Then, two or more flexible tethers are connected to both the first anchor and the second anchor so each of the tethers spans between the upper vertebra and the lower vertebra. Although the tethers span adjacent vertebrae in one embodiment, it is contemplated that the tethers may span and be connected to non-adjacent vertebrae. It is further contemplated that the more than two anchors and/or more than two tethers may be used with this method.
As will be appreciated by those of ordinary skill in the art, the methods and systems described above are capable of correcting abnormal spinal curvatures without fusing vertebrae. Further, the methods and systems described above enable surgeons to modify spinal column alignment simultaneously in multiple directions. In other embodiments, it is envisioned that similar systems may be used to alter the alignment of other types of bones or bone fragments. In addition, the methods and systems described above are minimally invasive thereby reducing opportunity for complications during and following the surgical procedures. Those skilled in the art will appreciate that the methods and systems described above permit progressive adjustment of vertebrae or growth guidance, or modulation in the skeletally immature spine to obtain a desirable optimal alignment of the spinal column for the patient. By shaping the rods, tensioning the tethers and adjusting the rods or tether after the initial surgery, the surgeon may progressively affect the alignment and/or growth of the vertebrae.
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
