Spinous process spacer

A spinous process spacer that is designed to maintain a desired spatial relationship between adjacent vertebrae, is configured for introduction into a spinal implant site in a compressed state and then expands in situ. Once expanded, formations of the present spinal spacer form areas, pockets or spaces that receive at least one bony portion of each adjacent vertebra. The present spinous process spacer has a changeable circumferential profile wherein a first circumferential profile is smaller than a second circumferential profile in order to provide/achieve its compressed and expanded states. The first circumferential profile defines the collapsed position or state while the second circumferential profile defines the position or state. Upon implantation, the present spinous process spacer is not fixed to any bony structure of the vertebrae but provides support. In this regard, use of the spinous process spacer, by itself, will not result in vertebral fusion. However, fusion can result with the use of bone graft packed about the spinous processes (and the spinous process spacer) or in conjunction with the use of an intervertebral body spacer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to devices for the spine and, more particularly, to a spinal implant for the treatment of stenotic spinal bone.

2. Background Information

As we age various changes can occur in the body. For instance, the ligaments of the spine can thicken and calcify (i.e. harden from deposits of calcium), bone and joints may enlarge, bone spurs called osteophytes may form, spinal discs may collapse and bulge (i.e. herniate) or one vertebra may slip over another (spondylolisthesis). Any one or these conditions and/or others can cause what is known as lumbar spinal stenosis. Lumbar spinal stenosis is a narrowing of the bony spinal canal. While some people are born with this condition, most often spinal stenosis is the result of one of the above-identified degenerative conditions that develop in mainly the middle-aged and elderly population.

In this regard, spinal stenosis may be considered as the gradual result of aging and “wear and tear” on the spine from everyday activities. Such degenerative or age-related changes in our bodies can lead to compression of nerves (i.e. pressure on the nerves that can cause pain and/or damage). Symptoms of lumbar spinal stenosis include leg pain (“pins and needles”) that can limit standing, walking, self-supporting daily activities, work, social and recreational pursuits. Lack of activity because of lumbar spinal stenosis may lead to obesity, depression and general physical deterioration.

Once diagnosed with lumbar spinal stenosis the doctor will usually try non-surgical treatments first. Such treatments may include anti-inflammatory medications (orally or by injection) to reduce associated swelling or analgesic drugs to control pain. Physical therapy may be prescribed with goals of improving ones strength, endurance and flexibility so that you can maintain or resume a more normal lifestyle. Spinal injections such as an epidural injection of cortisone may also be used. Such non-surgical treatments do not correct the spinal canal narrowing of lumbar spinal stenosis itself but may provide long-lasting pain control and improved life function without requiring a more invasive treatment. However, as a last resort for those patients who don't respond to non-surgical treatments, surgery will be advised.

Lumbar spinal stenosis is the most common reason for back surgery in people over the age of 50 in the United States. While there are various non-surgical treatments for lumbar spinal stenosis, a surgical procedure known as a laminectomy may be performed in order to reduce or eliminate the symptoms of lumbar spinal stenosis. A laminectomy or lumbar decompression surgery has the goal of opening up the bony canal to improve available space for the spinal nerves. As indicated, however, a laminectomy is usually a last resort for treating lumbar spinal stenosis. This is because a laminectomy is an invasive surgical procedure.

Fortunately, another surgical treatment for lumbar spinal stenosis is known that is less invasive than a laminectomy. This other surgical treatment involves implanting a spinal spacer between bony projections of adjacent vertebrae, particularly, but not necessarily, between spinous processes of adjacent vertebrae. It can be appreciated that the more compact the spinal spacer, the less invasive the surgical implantation procedure.

In view of the foregoing, it is therefore desirable to provide a compact spinal spacer. Moreover, it is desirable to provide a spinal spacer that is compact during implantation and expandable in situ.

SUMMARY OF THE INVENTION

A spinal implant, spinal spacer or stenotic device for maintaining a desired spatial relationship between adjacent vertebrae is provided that is configured for introduction into a spinal implant site in a compressed, collapsed, compacted or un-expanded state and then expands, un-compacts, or un-compresses in situ. Once expanded, formations of the present spinal spacer form areas, pockets or spaces that receive at least one bony portion of each vertebra.

The present spinal implant is embodied as a bony spinal protrusion spacer, spinous process spacer, interlaminar spacer, or inter-joint spacer (collectively, “spinous process spacer”) that is configured to be received in and fit between at least one bony spinal protrusion, of adjacent vertebrae of the spine and hold them apart. The present spinous process spacer may be made of titanium, PEEK, bone, a biocompatible elastomeric or other biocompatible material or compound.

Upon implantation, the present spinous process spacer is not fixed to any bony structure of the vertebrae but provides support. In this regard, use of the spinous process spacer, by itself, will not result in vertebral fusion. However, fusion can result with the use of bone graft packed about the spinous processes (and the spinous process spacer) or in conjunction with the use of an intervertebral body spacer.

The present spinous process spacer has a changeable circumferential profile wherein a first circumferential profile is smaller than a second circumferential profile in order to provide/achieve its compressed and expanded states. The first circumferential profile defines the collapsed, compressed, un-expanded or compacted position or state (compressed position) while the second circumferential profile defines an expanded, un-compressed, un-compacted position or state (expanded position).

In one form, the present spinous process spacer comprises a plurality of plates, each plate having a plurality of hinged flanges. When the flanges are folded, the spinous process spacer is in the compressed position. When the flanges are unfolded, the spinous process spacer is in the expanded position.

In a particular form, each plate defined by a center, core or central plate portion with a plurality of hinged flanges, protrusions, petals or leafs (collectively, ‘flanges’). The spinal spacer is thus formed of a stack of plates wherein flanges of one plate register with flanges of an adjacent plate to collectively form legs. The flanges fold or bend relative to the core.

Unlike decompressive surgery/laminectomy, the procedure for implanting the present spinal spacer is completely reversible, leaving all anatomical structures intact. Thus, the implantation procedure for the present spinal spacer can be used as a first line surgical approach without compromising any therapeutic alternatives, including laminectomy.

Because extension (e.g. standing upright) provokes spinal stenosis symptoms, the present spinal spacer is designed to impose what is referred to as acute kyphosis of the lumbar spine. This kyphosing of the vertebral bodies opens the foramen (of which are usually stenotic in the elderly) and allows the nerves to move a little more. Inserted through a small incision, the present spinal spacer is preferably placed posterior to neural structures to minimize the risk of neural injury. Other manners of implantation may be used.

This is a minimally invasive procedure whereby the compressed process spinal spacer is inserted into the space between adjacent bony spinal protrusions to provide localized distraction to the lamina. Once positioned, compressed flanges are expanded to provide an “X” shaped body. Legs of the X-shaped body allow receipt of the bony spinal protrusions.

Like reference numerals indicate the same or similar parts throughout the several figures.

A discussion of the features, functions and/or configurations of the components depicted in the various figures will now be presented. It should be appreciated that not all of the features of the components of the figures are necessarily described. Some of these non discussed features as well as discussed features are inherent from the figures. Other non discussed features may be inherent in component geometry and/or configuration.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 3depict a portion of a human spine wherein a spinous process spacer10, fashioned in accordance with the present principles, has been implanted between bony protrusions of adjacent vertebrae. Particularly, there is depicted adjacent vertebra V1and V2of a portion of the spine, with a spine disc D1situated between the vertebrae. Vertebra V1has a spinous process SP1and vertebra V2has a spinous process SP2. The spinous process spacer10is shown situated between the spinous processes SP1and SP2of respective adjacent vertebrae V1and V2in the expanded position. It should be appreciated that while the present spinal process spacer10is shown situated between spinal processes SP1and SP2, the present spinal process spacer10may be used as an interlaminar, interbody, or interbony spinal protrusion spacer. As such, while the present spinal process spacer10is shown and described in relation to the spinal processes of adjacent vertebrae, the spinal process spacer may be used between relevant bony structures of the vertebrae. It should thus be appreciated that while the present spinal process spacer10is shown and described with respect to the spinous process, the spinous process spacer may be used with other bony structures, the spinous process being only exemplary.

The spinal process spacer10is made from a biocompatible material such as titanium. Other biocompatible materials or compounds may be used such as PEEK, bone or an elastomeric. The spinal process spacer10is configured and/or adapted to receive, hold and maintain a desired spacing between adjacent vertebrae V1, V2(and spinous processes SP1, SP2) and this is accomplished by receipt of the spinous process spacer10between the spinous process SP1and spinous process SP2. The spacing is defined by the dimensions of the spinal process spacer10. As such, the spinal process spacer10may be made in various sizes or dimensions to accommodate various anatomies.

The spinous process spacer10has a body12formed of a plurality of individual plates16held together by a carrier/expansion assembly14. The carrier assembly14includes a top or first end cap20, a bottom or second end cap22, and a post24, the nomenclature top, bottom, first and second being arbitrary. The stack of plates12is held onto the post24between the bottom end cap22and the top end cap20. Each plate16has four (4) flanges18a,18b,18cand18dextending from a base32(see, e.g.,FIG. 9). A stack of flanges defines a leg. As seen in the figures, the four (4) stacks of flanges are situated about the cores32so as to define four (4) legs in an ‘X’ configuration. Other configurations are contemplated.

FIGS. 4 through 8depict the expanded spinous process spacer10as seen inFIGS. 1-3.FIGS. 9 through 11depict a single plate16only of the spinous process spacer10. As seen inFIGS. 9-11, each plate16has a core or base32defining a central portion or hub with a bore34extending through the base32. While the base32is shown as being rectangular it should be appreciated that the base may take other shapes as desired and/or is appropriate. The plate16further includes a plurality of flanges (panels, sections, portions, leaves, petals or the like)18that extend radially from the base32. The plate16(and thus the implant10) is shown with four (4) flanges18a,18b,18cand18dit being understood that the implant may have more or less flanges. Each flange18(i.e. flanges18a,18b,18cand18d) is connected to the base32via a hinge or hinge structure, which in this case is a resilient coupling of the flange to the base. Each resilient coupling is defined by a strip of the elastic material that extends from an edge of the base32to a flange18. Each strip is reduced in thickness relative to the other portions of the implant and/or particularly is of a thickness that allows elastic bending thereof without breaking in order to form an elastic or resilient hinge. As seen inFIGS. 1 through 8, the hinges allow their respective flanges18a,18b,18cand18dto fold inward toward an axis of the base32to thereby define the compressed, closed or folded position.

The flanges may be formed so as to normally be in the uncompressed or open position wherein a biasing force (i.e. deformation bias) is necessary to move the flanges into the compressed, folded or closed position. Once the deformation bias is removed, the closed position of the implant10automatically (e.g. through the elasticity of the material or the application of an external biasing force) becomes the deployed, uncompressed, expanded or open position. The flanges may alternatively be formed so as to normally be in the compressed or closed position wherein a biasing force (i.e. opening bias or force) is necessary to move the flanges into the open position.

Each plate16is configured to engage a like, adjacent plate16. The configuration of a plate16provides for rotational stability of one plate16relative to an adjacent plate16and the positive axial joining thereof. Particularly, each flange18is configured to engage the like, adjacent flange18of the adjacent plate16. The configuration of a flange18provides for rotational stability of one flange18relative to an adjacent flange18and the positive axial joining thereof. It should be appreciated that the configurations of the plate16and flanges18may differ from that shown in the figures.

Each flange18may include a curved concave inner surface and a curved convex outer surface. A ridge25(i.e.25a,25b,25cand25d) is formed on each inner surface. The flange ridge25extends radially from the base32and along the inner surface thereof. A channel19(i.e.19a,19b,19cand19d) is formed on each outer surface and is configured to receive a flange ridge25of an adjacent flange18. It should be appreciated that the configuration of each flange18may change. Different configurations are contemplated.

With reference again toFIGS. 4 through 8, the spinous process spacer10is shown in the expanded position. The end cap20is held in frictional engagement with the post24via four (4) spokes27a,27b,27cand27dextending from a ring26. The post24has a side for each spoke27. This may not necessarily be the case. The ends of the four (4) spokes27are in frictional engagement with respective four (4) sides of the post24. The post may have more or less sides as is the case with the number of spokes. In a different configuration, the post24is rectangular and the number of spokes is three (3).

The bottom end cap22defines a generally cup-shaped body23that holds the post24(i.e. the bottom end cap22is fixed relative to the post24). The top end cap20is movable relative to the post24. As the top end cap20is moved axially down the post24the top end cap24pushes against the top compressed plate16. This, in turn, pushes against an adjacent plate16until an adjacent plate16pushes against a bottom-most plate16. As the bottom-most plate16pushes against the bottom end cap22, the compressed plates16expand.

It should be appreciated that the spinous process spacer10may come in various sizes/dimensions to accommodate various bony structure anatomies as well as provide a desired spacing therebetween. Also, the body of the present spinous process spacer10may be otherwise shaped.

The present spinous process spacer10is implanted between adjacent bony protrusions through an incision made in the patient proximate the area of implantation. Adjacent vertebrae are distracted and an appropriate dimensioned spinous process spacer10is situated between adjacent bony structures. The spinous process spacer10is inserted between the desired bony structures of adjacent vertebrae in the collapsed, closed or compressed position. Once in the desired location, the implant10is deployed into the expanded, open or un-compressed position in order to maintain space between the bony structures. The amount of space is determined by the dimensions of the implant10. Because the implant10is introduced into the implant site in a compressed state and then expanded in situ, the implant10provides a smaller profile upon introduction of the implant than would an un-compressed implant. The smaller implant profile translates into use of the implant in minimally invasive surgery. It also provides other surgical benefits.

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, it being understood that only a preferred embodiment has been shown and described and that all changes and/or modifications that come within the spirit of the invention are desired to be protected.