Adjustable trial for sizing a spinal implant

An adjustable trial for spinal implant sizing. The trial has a first and second plate that is adjustable between zero and degrees by use of continuously sloped edges that interface with a positioning band having reciprocal sloped edges. Protrusions are attached to each plate and the positioning band, the rotation of which is used to change the angle of the plates. A tool used to rotate the protrusions is marked with the angle of movement.

FIELD OF THE INVENTION

The present disclosure generally relates to medical devices for the treatment of musculoskeletal disorders, and more particularly to an adjustable trial to provide spinal implant sizing.

BACKGROUND OF THE INVENTION

Spinal disorders such as degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and/or aging. The front or anterior portions of adjacent vertebrae between which an intervertebral disc normally resides are referred to as “vertebral bodies.” The anterior space between adjacent vertebral bodies where a disc normally resides is referred to as “intervertebral disc space.” The vertebral bodies provide support and structure of the spine while spinal discs, located between the vertebrae, act as cushions. These discs contribute to the flexibility and motion of the spinal column. Over time, the spinal disorders may cause the discs to become diseased, infected, develop deformities such as tears/cracks, or simply lose structural integrity. These impaired discs can affect the anatomical functions of the vertebrae, due to the resultant lack of proper biomechanical support, and are often associated with chronic back pain, nerve damage and in severe cases partial or complete loss of mobility. In cases where an intervertebral disc becomes abnormal, the intervertebral disc is usually surgically removed and replaced with an intervertebral implant device into the vacated intervertebral disc space.

The common approach to the removal of a diseased intervertebral disc and replacement with an intervertebral implant is usually via a posterior or an anterior approach. Disc replacement surgery usually includes posterior laminectomy to first decompress the posterior neural elements and to gain access either through a direct posterior approach, or through a transpedicular approach, or through a posterior-lateral or transforaminal approach. After posterior exposure, the intervertebral disc is removed and the intervertebral disc space prepared to receive an implantable device inserted through a posterior-lateral approach or through a lateral transforaminal approach.

Commonly the intervertebral disc space is prepared to receive an implant by use of trials devices. Once the intervertebral disc is removed from the body during the lateral lumbar interbody fusion, the surgeon tries different sized trial implants to determine the appropriate size of the implant for maintaining a distance between the adjacent vertebrae. A trail implant kit conventionally holds numerous trail implants of various heights and geometric options to fit the anatomical needs of a patient. Another consideration is to maintain the natural angle between lumbar vertebral bodies to accommodate the lordosis, or natural curvature, of the spine. Therefore, during selection of an implant, both intervertebral disc height and lordosis must be considered.

A conventional trial implant kit contains multiple trial implants. Each implant preferably has a different shape and/or size, which is identical to, or similar to, a shape and size of an available prosthesis to be implanted. Each trial implant includes a body having a size and shape adapted to fit within or adjacent to an anatomical structure, and at least one marker strip associated with the body and formed from a radio-opaque material. This procedure is generally conducted using fluoroscopy and tactile feel.

What is lacking in the art is an adjustable trial for implant sizing.

SUMMARY OF THE INVENTION

An adjustable trial for spinal implant sizing formed a first plate having a substantially flat outer surface spaced apart from an inner surface with a centrally disposed coupling member extending outwardly from the inner surface. First and second apertures extend from the outer surface to the inner surface on each side of the coupling member. A first cylindrical shaped member is secured to the first plate having a continuous sloped edge with a converging angle. A centrally disposed aperture coincides with the first and second apertures of the first plate wherein a first protrusion extends into the first cylindrical shaped member aperture. A positioning band having a sloped upper surface and a sloped lower surface is rotatable with the continuous sloped edge of the first cylindrical shaped member forming a converging angle. The positioning band having a centrally disposed aperture that coincides with the first and second apertures of the first plate and employs a second protrusion extending into positioning band centrally disposed aperture. A second cylindrical shaped member rotatable having a continuous slope edge converging at an angle forming a mirror image to said first cylindrical shaped member, the second cylindrical shaped member having an aperture with an inner diameter that coincides with the positioning band aperture wherein a third protrusion extends into the aperture for alignment with the first protrusion. A second plate forming a mirror image of said first plate includes a substantially flat outer surface spaced apart from an inner surface which is secured to the second cylindrical shaped member. A coupling member extends outwardly from the inner surface and the second plate includes a first aperture and a second aperture placed in alignment with the first aperture and second aperture of the first plate. A coupling element having a top end is attached to the first plate by a pin; a bottom end of the coupling element is attached to the second plate by a second pin.

An objective of the invention is to provide an adjustable trial device determining the correct sized implant.

Another objective of the invention is to provide plates that are adjustable between an angle of zero degrees and 20 degrees.

Still another objective of the invention is to provide a tool that rotate protrusions to provide an angular reading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Now referring to the Figures, an adjustable trial10for spinal implant sizing is constructed from a first plate12,FIGS.5A-5E, having a substantially rectangular shape defined by a front edge14, a rear edge16and opposing side edges18and20. The first plate12further defined by a substantially flat outer surface22spaced apart from an inner surface24with a centrally disposed coupling member28extending outwardly from the inner surface24. The first plate12having a first aperture30and a second aperture32extending from the outer surface22to the inner surface24formed on each side of the coupling member28.

A first cylindrical shaped member40, further depicted inFIGS.6A-6D, is juxtapositioned along the inner surface24of the first plate12. The first cylindrical member40having a continuous sloped edge42converging at an angle of about 5 degrees wherein a proximal end44has a thickness that is greater than a distal end46thickness. The first cylindrical shaped member40having a centrally disposed aperture48formed by an inner diameter that coincides with the first and second apertures30,32of the first plate12. A first protrusion50extends into the first cylindrical shaped member aperture48for use rotating the first cylindrical shaped member40changing the angular slope of the outer surface22of the first plate12so as to conform to the position of a spinal disc, not shown.

A positioning band60, further illustrated inFIGS.7A-7D, has a sloped upper surface62and a sloped lower surface64. The sloped upper surface62is rotatable with the continuous sloped edge42of the first plate12formed between a proximal end65and a distal end67converging at an angle of about 10 degrees. The positioning band60having a centrally disposed aperture64that coincides with the first and second apertures30,32of the first plate12and a second protrusion66extending into positioning band centrally disposed aperture64aligned with said second aperture32of said first plate12. As will be further illustrated, rotation of the protrusions50,66provides angular positioning of the first plate12and second plate90.

A second cylindrical shaped member70, further illustrated inFIGS.8A-8D, having a continuous sloped edge72converging at an angle of about 5 degrees wherein a proximal end74has a thickness that is greater than a distal end76thickness with a lower edge73. The continuous sloped edge72forming a mirror image to said first cylindrical shaped member sloped edge42. The second cylindrical shaped member70having an aperture with an inner diameter that coincides with the positioning band aperture64. A third protrusion82extending into the aperture78of said second cylindrical shaped member for adjustable alignment with the first protrusion50and second protrusion66. Illustrated inFIGS.1C,2C and3C, rotation of protrusions50,82together in one direction and protrusion66in the other direction changes the lordosis angle.

A second plate90forming a mirror image of said first plate12having a substantially rectangular shape defined by a front edge, a rear edge and opposing side edges. The second plate90further includes a substantially flat outer surface92spaced apart from an inner surface94which is secured to the second cylindrical shaped member70. A coupling member98extends outwardly from said inner surface94. The second plate90having a first aperture102and a second aperture104placed in alignment with said first aperture30and said second aperture32of the first plate12.

A coupling element100, further illustrated inFIGS.9A-9D, having a top end106attached to the first plate12by a pin108, a bottom end110of the coupling element100is attached to the second plate90by a pin112. A tool can be employed to maintain the first protrusion50and the third protrusion82in alignment while moving the second protrusion allowing said outer surface22of said first plate12and said outer surface92of said second plate90to vary from an angle of zero degrees to an angle of 20 degrees. Upon rotation of the first50and third protrusions82, in relation to the second protrusion66results in the angular placement of the first and second plates which can be measured directly to allow sizing of the implant, or read from the tool used to move the protrusions wherein the position of the protrusions can be translated to markings on the tool allowing the tool to state the plate angle.

The trial implant10is formed from a material that is visible under radiographic imaging, such as titanium, stainless steel, or the like. Alternatively the implant is formed from materials such as polymers, ceramics, composite materials, and combinations thereof. Examples of suitable polymers include polyether sulfone, polycarbonate, and bioabsorbable polymers, and examples of suitable composites include carbon fiber reinforced polymers. The marker strip can also be formed from a variety of radio-opaque materials including, for example, metals, polymers, filling salts, ceramics, and combinations thereof. Examples of suitable metals include titanium, stainless steel, tantalum, cobalt chromium, aluminum, and combinations thereof. Marker strips may also be configured to indicate, on an x-ray image, the size and alignment of the body with respect to the anatomical structure when the implantable trial prosthesis is positioned within or adjacent to an anatomical structure. In use, the surgeon can select an implant from among several implants provided in the kit, and position and x-ray the implant to determine the fit. In the event that the selected trial implant does not fit appropriately, the surgeon simply rotate the protrusions to change the angle. Once the angle is selected the surgeon can then implant the appropriately sized implant for that particular patient.

Referring toFIGS.1A-1F, illustrated is the adjustable trial10in an expanded position.FIGS.1C and1Edepict the rotation of protrusions50,82in relation to protrusion place66.

Referring toFIGS.2A-2F, illustrated is the adjustable trial10in a contracted position.FIGS.2C and2Edepict the rotation of protrusions50,82in relation to protrusion place66.

Referring toFIGS.3A-3F, illustrated is the adjustable trial10in a semi-expanded position.FIG.4Cdepicts the rotation of protrusions50,82in relation to protrusion place66. Indicia101may be placed on the adjustable trial to indicate lordosis angle in relation to the protrusion placement.

The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus 5%. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”

The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) are open-ended linking verbs. As a result, a device that “comprises,” “has,” “includes” or “contains” one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements.