Linearly expanding spine cage for enhanced spinal fusion

• US 20080188941A1
• Filed: 10/31/2007
• Published: 08/07/2008
• Est. Priority Date: 08/12/2005
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Coalign Innovations Inc. (Stryker Corporation)
• Inventors: Grotz, R. Thomas
• Granted Patent: US 7,819,921 B2
• Time in Patent Office: Days
• US Class Current: 623/17.16
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61F 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30784 Plurality of holes
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30878 with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/30975 made of two halves
• CPC Class Codes: A61F 2002/448 comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/4627 with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0019 rectangular
• CPC Class Codes: A61F 2310/00023 Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00796 Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: A61F 2310/00976 Coating or prosthesis-covering structure made of proteins or of polypeptides, e.g. of bone morphogenic proteins BMP or of transforming growth factors TGF

Abstract

A linearly expanding spine cage has a minimized diameter in its unexpanded state that is equal to the diameter of an insertion groove cut into adjacent vertebral bodies. The cage conformably engages between the endplates of adjacent vertebrae to effectively distract the disc space, widen neuroforamina, stabilize the motion segments and eliminate pathologic spine motion. Angular deformities can be corrected, and natural curvatures maintained. The cage enhances spinal arthrodesis by creating a rigid spine segment. Expanding linearly (vertically, along the vertical axis of the adjacent spine) rather than uniformly, the cage height increases and holds the vertebrae with fixation forces greater than adjacent bone and soft tissue failure forces. Stability is thus achieved immediately, enabling patient function by eliminating painful motion. The cage width remains stable, so as to decrease impingement upon a second cage, or upon soft tissue structures in the immediate vicinity, including neural or vascular elements.

Claims

1-8. -8. (canceled)

9. A method for correcting spinal deformities using a linearly expanding spine cage (LEC), being linear in one plane and either parallel and oblong or trapezoidal in another, the LEC comprising two halves joined in an unexpanded state along a common longitudinal axis to form a cylinder having a diameter equal to an insertion bore cut in adjacent vertebral bodies, the LEC including a wedge for expanding the LEC halves linearly and vertically at a desired angle with respect to a spinal column comprising:

determining a desired change in height and angle of alignment in any of three dimensions of a first and second adjacent vertebral body;

selecting one or more expansion wedges, each wedge comprising angled sides joined by a base wherein the sides of the selected wedge are characterized by an appropriate angle for achieving the desired correction;

cutting one or more insertion bores through adjacent vertebral bodies such that each bore extends transversely with respect to the spine;

inserting the LEC with corresponding selected expansion wedge into the one or more bores such that each half of the LEC conformably engages a corresponding half of the bore in the adjacent vertebral bodies; and

advancing the expansion wedge into the LEC to impart desired vertical height and angle of correction while maintaining fixed conformable engagement between each LEC half and corresponding vertebral body.

10. A method for correcting spinal deformities according to claim 9 further comprising the step of varying angulation of the angled sides of the expansion wedge to impart linear symmetrical vertical expansion or offset vertical expansion to the LEC halves for effecting a desired angle of correction to a spinal column in any of three dimensions.

11. A method for correcting spinal deformities using a linearly expanding spine cage (LEC) as in claim 9 further comprising the step of providing a series of bone engaging features, such as ridges, corrugations, points, or the like extending over the surface of each LEC half to provide a maximized bone engaging surface area for enhanced bone fusion and to facilitate locking engagement by force from expansion of each LEC half with its corresponding engaged vertebral body.

12. A method for correcting spinal deformities using a linearly expanding spine cage (LEC) as in claim 9 further comprising the step of:

providing a series of slots or apertures extending through the bone engaging surface of each LEC half to facilitate bone ingrowth into the LEC.

13. A method for correcting spinal deformities using a linearly expanding spine cage (LEC) as in claim 9 further comprising the step of providing a quantity of bone growth enhancing agents in the cylinder formed by the LEC halves to facilitate bone fusion and ingrowth into the LEC with fixation forces greater than adjacent bone and soft tissue failure forces.