Patent Application
20070270962
The present invention is generally related to tools and instruments for installation of spinal prostheses.
Many kinds of spinal prostheses have been described in the literature. Posterior spinal prostheses are described in U.S. patent application Ser. No. 10/750,860 to Arnin et al., assigned to Impliant Ltd. One of the posterior spinal prostheses described therein is illustrated in
A spinal prosthesis 50 may include an upper (superior) vertebral attachment member 52 and a lower (inferior) vertebral attachment member 54. The attachment members 52 and 54 may be attached to adjacent spinous processes (not shown), or to pedicles (not shown) without having to attach the attachment members 52 and 54 to the spinous processes.
A flexure assembly 56 may be placed between and may be integrally formed with or attached to upper and lower vertebral attachment members 52 and 54. An elastomeric boot 58 may be placed around the flexure assembly 56. The flexure assembly 56 permits flexure of prosthesis 50 about mutually orthogonal axes as well as other directions for omnidirectional flexure in any degree of freedom.
It is noted that the spinal prostheses 50 may be constructed as a unitary body with at least three attachment points attachable to spinal structure. By “unitary body” it is meant that the spinal prosthesis may be attached to the spinal structure as one pre-assembled, contiguous assembly. The surgeon can simply hold the entire unitary body in place during attachment to the spinal structure. This is in contrast to other known prostheses that must be attached to the spinal structure as at least two separate parts, which may or may not articulate with one another. With those prostheses, the surgeon must attach each part separately to some spinal structure and merely “hope” that the parts fit together properly after installment. The unitary construction of the present invention eliminates this problem and greatly facilitates installation of the prosthesis.
One way of installing prosthesis 50 is by means of pedicle screws (not shown), e.g., polyaxial pedicle screws. The swivel heads of the polyaxial pedicle screws may be rotatably attached to rounded prongs 76 jutting from upper and lower vertebral attachment members 52 and 54, such as by means of lock nuts (not shown) that mate with the swivel heads.
In order to install prosthesis 50, a laminectomy may be performed, thereby creating a gap between the spinous processes. The pedicle screws may be screwed into the pedicles. The prosthesis 50 may be inserted in the gap between the spinous processes, with the rounded prongs 76 aligned with the heads of the pedicle screws. The lock nuts may then secure the prosthesis 50 to the pedicle screws.
The configuration of prosthesis 50 may be tailored by the manufacturer to particular vertebrae and to the specific spinal anatomy of a patient. Various design parameters may thus change, such as but not limited to, the angle and length of the prongs 76, size and height of the prosthesis 50, and other factors. Various anatomical parameters may vary, such as but not limited to, configuration and size of the lamina, pedicles, and other spinal anatomical features. It is thus desirable to have a tool or set of tools to facilitate and insure correct installation of prosthesis 50 (or in general any posterior spinal prosthesis).
The present invention seeks to provide tools and instruments for installation of spinal prostheses, as is described more in detail hereinbelow. The tools disclosed herein are particularly advantageous for installing the posterior spinal prostheses shown in
There is thus provided in accordance with an embodiment of the present invention an article including an insertion angle tool for aligning insertion of pedicle screws into spinal structure, the insertion angle tool including one or more extension arms that each include a tool receiving portion adapted to receive therein an instrument, and a level indicator, the tool receiving portion being angled such that when the level indicator indicates the insertion angle tool to be level, an instrument held in the tool receiving portion is properly aligned for a particular spinal structure. The level indicator may be a pendulum arranged for oscillating between markers, wherein a center mark is provided to indicate the insertion angle tool to be level. Alternatively or additionally, the level indicator may be a bubble vial adapted to indicate when the insertion angle tool is level. The tool receiving portion may include a through hole formed through the extension arm. Alternatively, the tool receiving portion may include a bent extremity of the extension arm, or a hooked portion adapted for hooking on to a receiving member of an instrument.
There is also provided in accordance with an embodiment of the present invention an article including a prosthesis-fastener orientation tool for properly aligning a posterior prosthesis with fasteners that fasten the prosthesis to spinal structure, including structure that mimics attachment of the posterior prosthesis to pedicle screw heads and which is rotationally alignable about an axis with respect to the pedicle screw heads. The prosthesis-fastener orientation tool may include structure receivable in the pedicle screw heads and an angular gauge adapted to measure rotational alignment about the axis with respect to the pedicle screw heads.
There is also provided in accordance with an embodiment of the present invention an article including a prosthesis-holder tool including a grasping portion that includes a pair of jaws rotatingly mounted on a handle, and an actuator for opening and closing the jaws, the jaws including one or more teeth receivable in holding structure found in a prosthesis.
There is also provided in accordance with an embodiment of the present invention an article including a spinal prosthesis adapted for installation in spinal structure, the spinal prosthesis being formed with a recess, and a prosthesis-holder tool including a grasping portion that grasps the recess, the grasping portion when received in the recess not extending beyond an upper surface of the recess. For example, the grasping portion may be flush with or below the upper surface of the recess.
There is also provided in accordance with an embodiment of the present invention an article including a tool for installing a posterior spinal prosthesis including a template portion affixed to a handle, the template portion including protrusions that match corresponding portions of posterior spinal anatomical structure so as to help align and seat the tool in the spinal structure. There may be provided a plurality of the tools, wherein the tools have different sized template portions for different sized posterior spinal prostheses.
In the drawings:
Reference is now made to
In preparation, prior to installing the posterior spinal prosthesis, a posterior midline incision may be made in the back of the patient, and as is known in the art, a laminectomy may be performed to create a gap between the spinous processes (e.g., between L4 and L5). Tool 10 may be used to make sure the gap is sized correctly for the type of posterior spinal prosthesis selected (e.g., normal size or low profile). Tool 10 may include a jig or template portion 12 affixed to a handle 14. Template portion 12 may include protrusions 16 that match corresponding portions (e.g., recesses) in the posterior spinal anatomical structure or which may abut against spinal structure so as to help correctly align and seat tool 10 in the spinal structure. The width and size of template portion 12 are chosen to make sure the gap is sized correctly for the type of posterior spinal prosthesis selected.
After the laminectomy has been performed, pedicle screws may be installed in the pedicles. As is known in the art, the pedicle screws may be inserted and screwed into the bone tissue directly or may be inserted by means of a Kirschner wire (K-wire; not shown), the insertion being monitored and guided by x-ray imaging or the like. It is important for the pedicle screws to be inserted at the correct insertion angle for the particular spinal structure (e.g., L5), or at least within a tolerance of the recommended insertion angle, e.g., ±15°, so that the polyaxial head of the pedicle screw can properly compensate for any angular misalignment (the tolerance for the angle between the polyaxial head and the shank of the screw is typically ±20°). It is noted that the invention is not limited to these angular ranges.
Reference is now made to
The insertion angle tool 20 also includes a level indicator 23, such as but not limited to, a pendulum 24 arranged for oscillating between two markers 25 and is centered at a center mark 26. The tool receiving portion 22 is angled such that when the pendulum 24 is at the center mark 26, the insertion angle tool 20 is level and any instrument held in the tool receiving portion 22 is properly aligned for the particular vertebra. For example, in the illustrated embodiment, when the pendulum 24 is at the center mark 26, any instrument held in the tool receiving portion 22 is properly aligned for the L5 vertebra. The level indicator 23 of insertion angle tool 20 may alternatively or additionally include a bubble level 19 (e.g., a straight bubble vial or a circular omnidirectional bubble vial).
After determining the proper insertion angle with insertion angle tool 20, the pedicle screws may be inserted into the spinal structure. The pedicle screws should preferably be left several turns proud of the spinal structure to allow for further alignment with the next tool, which is now described.
Reference is now made to
The orientation tool 30 may include two identical or near identical tools, each including a structural member, such as prongs 31 that mimic the size, spacing and angular orientation of prongs 76 of prosthesis 50. Prongs 31 are situated at the end of a shaft 32 at the other end of which is a handle 33. Adjacent prongs 31 may be a hook portion 34 for supporting and pivoting orientation tool 30 against spinal structure. An angular gauge 35 may be placed at some point on shaft 32, such as a scale with graduations near handle 33.
In use, the prongs 31 of one of the orientation tools 30 may be placed into adjacent pedicle screw heads 72, as seen in
Aligning the two orientation tools 30 may be easily accomplished by removing one of the orientation tools 30 from its pedicle screw heads 72 and further screwing one or both of the pedicle screws 70 further into the bone. This changes and fine-tunes the angular orientation until upon re-attachment of the orientation tool 30 to the pedicle screws 70, the two orientation tools 30 are exactly aligned as seen in
Reference is now made to
Reference is now made to
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
Although the invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations are apparent to those skilled in the art. Accordingly, all such alternatives, modifications and variations fall within the spirit and scope of the following claims.
