WO2008062397A1

WO2008062397A1 - Articulating spinal spacer

Info

Publication number: WO2008062397A1
Application number: PCT/IL2007/001288
Authority: WO
Inventors: Boris Silberstein; Alex Feldman; Anatoly Konik; Eduard Batkilin
Original assignee: Flexsis Surgical Ltd.
Priority date: 2006-11-24
Filing date: 2007-10-25
Publication date: 2008-05-29

Abstract

An intra-articular spinal spacing device (100) having a longitudinal axis, the device comprising: i) an upper elongate element (20) having a lower surface; ii) a lower elongate element (30) having an upper surface; and iii) a pivot joint (40) operatively associated with said upper surface and said lower surface, said pivot joint offsetting said upper surface from said lower surface at least in the vicinity of said pivot joint. Disclosed is a method for installing a spinal spacer, the, method comprises placing a human in a. prone position, reducing a lordotic angle between two adjacent vertebrae, incising an incision in epidermal tissue adjacent to a posterior portion of a spine of the human, boring two bores through the incision between two spinal vertebrae, and placing a pivot within each of the two bores.

Description

ARTICULATING SPINAL SPACER

This application claims the benefit of provisional application 60/860,707, filed November 24, 2006, which is incorporated herein in its entirety by reference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to spinal support devices configured to restore and/or maintain intervertebral disk space and preserve partial motion between the vertebrae.

Intervertebral discs facilitate motion between adjacent spinal vertebrae so that the spine has overall mobility. Motions between adjacent spinal vertebrae include, inter alia, flexion, extension, lateral bending, and axial rotation. Additionally, intervertebral discs serve as spacers between adjacent vertebrae, allowing spinal nerve roots to freely exit without vertebral impingement.

Injury, disc herniation, or degenerative disorders may cause an intervertebral space to partially collapse, resulting in painful impingement of the spinal nerve roots by the adjacent vertebrae. Impingement of spinal nerve roots may be accompanied by disabling pain, and/or paralysis of upper and/or lower limbs.

One common method of relieving spinal nerve impingement uses an artificial spinal disc replacement that installs between two adjacent vertebrae and restores the height of the intervertebral space. In addition to restoring the intervertebral space height, many artificial disc replacements are designed to restore the above-noted motions of flexion, extension, lateral bending, and axial rotation of the implanted intervertebral vertebral space.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method for installing a spinal spacer, the method comprising placing a human in a prone position, reducing a lordotic angle between two adjacent vertebrae, incising an incision in epidermal tissue adjacent to a posterior portion of the spine of the human, boring two bores through the incision between two spinal vertebrae, and placing a pivot within each of the two bores. In embodiments, pivoting motion between the two spinal vertebrae is limited to flexion and extension.

In embodiments, the method includes restoring the lordotic angle between the two spinal vertebrae. In embodiments, the at least one of the pivots is configured to duplicate at least one parameter associated with the two spinal vertebrae, the at least one parameter comprising at least one of a maximum intervertebral flexion angle, and a maximum intervertebral extension angle.

According to a further aspect of the invention, there is provided a method for installing a spinal spacer, the method comprising incising an incision in epidermal tissue adjacent to a posterior portion of a spine of a human, boring a first bore through the incision between two spinal vertebrae, a spinal process, and a first spinal facet, placing a first pivot within the first bore, boring a second bore between the two spinal vertebrae, the spinal process, and a second spinal facet, placing a second pivot within the second bore, and pivoting the two spinal vertebrae on the pivot.

In embodiments, the method includes pivoting the first pivot in at least one of flexion and extension, lateral bending, and axial rotation.

In embodiments, the pivoting occurs around a virtual center of rotation.

In embodiments, the method includes limiting the pivoting motion between the two spinal vertebrae to flexion and extension. In embodiments, at least one of the first pivot and the second pivot is configured to duplicate at least one parameter associated with the two spinal vertebrae, the at least one parameter comprising at least one of a maximum intervertebral flexion angle, and a maximum intervertebral extension angle. According to another aspect of the invention, there is provided a method for installing a spinal spacer, the method comprising incising an incision in epidermal tissue adjacent to a posterior portion of a spine of a human, boring two bores through the incision between two spinal vertebrae, placing a pivot assembly within each of the bores, limiting a pivot motion provided by the pivots to flexion and extension, and pivoting the two spinal vertebrae in flexion and extension.

In embodiments, the human is placed in the prone position in a manner that reduces an intervertebral angle between adjacent surfaces of the two spinal vertebrae. In embodiments, the pivoting occurs around a static center of rotation.

According to still another aspect of the invention, there is provided an intraarticular spinal spacing device having a longitudinal axis, the device comprising an upper elongate element having a lower surface, a lower elongate element having an upper surface, and a pivot joint operatively associated with the upper surface and the lower surface, the pivot joint offsetting the upper surface from the lower surface at least in the vicinity of the pivot joint.

In embodiments, pivot movement around the pivot joint is limited by contact between the lower surface and the upper surface at adjacent longitudinal ends. In embodiments, the pivot joint is located eccentric along the longitudinal axis.

In embodiments, during pivoting motion, the maximum offset between the upper and lower surfaces on a first side of the pivot is greater than the maximum offset between the upper and lower surfaces on a second side of the pivot. In embodiment, the device includes an outer surface having at least one stabilizing extension extending outwardly therefrom.

In embodiments, the device includes an outer surface comprising a round cylinder.

In embodiments, the outer surface includes at least one screw thread extending outwardly therefrom.

According to a further aspect of the invention, there is provided an intraarticular spinal spacing system, the system comprising two elongate pivoting elements, a first elongate pivoting element having a first longitudinal axis and a first average cross-sectional diameter, and a second elongate pivoting element having a second longitudinal axis and a second average cross-sectional diameter, wherein the sum of the first and second average cross-sectional diameters is less than a transverse distance across a human intervertebral space.

In embodiments, at least one of the two elongate pivoting elements includes an upper member, a lower member, and a pivot joint operatively associated with the upper member and the lower member. In embodiments, the upper member includes a lower surface, the lower member includes an upper surface, and the upper surface is offset from the lower surface at least in the vicinity of the pivot joint.

In embodiments, the pivot joint comprises a pivot axis that is transverse to the longitudinal axis of the at least one elongate pivoting element.

In embodiments, the pivot joint includes a spherical extension and the pivot joint moves in at least one of flexion and extension, lateral bending, and axial rotation.

In embodiments, the spacing system includes an axis passing through said pivot joint of said first elongate pivoting element and said pivot joint of said second elongate pivoting element; said axis being transverse to the longitudinal axis of said at least one elongate pivoting element.

In embodiments, at least one of the two elongate pivoting elements includes an outer surface having at least one stabilizing extension extending outwardly therefrom. In embodiments, at least one of the two elongate pivoting elements includes an outer surface comprising a round cylinder.

In embodiments, the outer surface includes at least one screw thread extending radially outwardly therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

Figure IA shows a spinal spacer, according to embodiments of the invention; Figure IB shows a cross-sectional view of a pivot joint of the spinal spacer of Figure IA, according to embodiments of the invention;

Figure 1C shows dual spinal spacers of Figure IA installed between two vertebrae, shown in a posterior-lateral view, according to embodiments of the invention;

Figure 2 A shows a side view of the spinal spacer of Figure IA, according to embodiments of the invention;

Figures 2B-2D show side views of vertebrae, according to embodiments of the invention; Figure 3 shows the spinal spacer of Figure 2 A installed between two vertebrae, shown in a side cross-section, according to embodiments of the invention;

Figure 4 shows an installation tool for installing the spinal spacer of Figure 3, according to embodiments of the invention;

Figures 5-7 show the installation tool shown in Figure 4 coupling with the spinal spacer of Figure 3, according to embodiments of the invention;

Figures 8-14 show details for surgically installing the spinal spacer of Figure 3, according to embodiments of the invention; and

Figures 15-16 show alternative configurations of the spinal spacer of Figure 3, according to embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are to an intervertebral disk spacer, the principles of which may be better understood with reference to the drawings and accompanying descriptions. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. Spinal Spacer Design

Referring now to the drawings:

Figure IA shows a spinal spacer 100 comprising an upper elongate element 20 and a lower elongate element 30. Upper elongate element 20 articulates with lower elongate element 30 with a pivot joint 40; alternatively referred to herein as pivot element 40, or pivot 40.

In embodiments, an external portion of pivot joint 40 comprises a semicircular extension 41 that extends from lower elongate element 30 and moves within a semicircular depression 43 associated with upper elongate element 40. As seen in Figure IB, a cross-sectional view of pivot joint 40, upper element

20 and lower element 30 form an internal pivot interface 82. Internal pivot interface 82 is configured so that a space 84 is formed between semi-circular depression 43 and semi-circular extension 41 when upper elongate element 20 and lower elongate element 30 are parallel. Space 84 allows the pivoting motion associated with pivot joint 40 with respect to transverse axis 47 and along pivot interface 82.

As used herein, transverse axis 47 refers to any axis passing transversely through a center of rotation 103 of pivot joint 40, including axes that are skewed with respect to a horizontal axis represented by transverse axis 47, including, for example, a first skewed transverse axis 47¹ and a second skewed transverse axis 47". Additionally, in embodiments, longitudinal axis 49 passes through center of rotation 103. In some embodiments, the spherical shape of internal pivot interface 82 allows longitudinal skewing of upper elongate element 20 with respect to lower elongate element 30.

For example, longitudinal axis 49 of upper elongate element may assume a first longitudinal skewed axis 49' or a second longitudinal skewed axis 49" with respect to longitudinal axis 49 of lower elongate element 30, also seen in Figure IA.

There are many alternative configurations and designs for pivot joint 40, some of which will be discussed below.

Implanted Spinal Spacers

Figure 1C shows dual spinal spacers 100 installed between an upper vertebra 70 and a lower vertebra 80, with left spinal spacer 100 between a spinous process 199 and a left facet 117 and right spinal spacer 100 between spinous process 199 and a right facet 119.

Dual spinal spacers 100 provide a pivot axis 47 that is transverse to longitudinal axis 49 passing through either one of spinal spacers 100. Dual pivot joints 40 preserve flexion and extension motions 51 while substantially preventing lateral bending 53, and axial rotation 59 motions between spinal vertebrae 70 and 80. Possible advantages to limiting some motions of vertebrae

70 and 80, while preserving other motions, are discussed below in the section entitled

"Experimental Examples". Spinal spacer 100 is configured to easily install into vertebrae 70 and 80. In embodiments, upper elongate element 20 and lower elongate element 30, together, form a cylindrical shape, which allows easy installation of: a) first spinal spacer 100 within a first bore drilled between spinous process 199 and right facet 119; b) second spinal spacer 100 within a second bore drilled between spinous process 199 and left facet 117, wherein c) both bores are between upper vertebra 70; and lower vertebra

80, as explained below.

While first spinal spacer 100 is between spinous process 199 and right facet 119 andsecond spinal spacer 100 is between spinous process 199 and left facet 117, the opposite could occur, with first spinal spacer 100 between spinous process 199 and left facet 117 and second spinal spacer 100 between spinous process 199 and right facet 119.

Positional stability of implanted spinal spacers 100 may be ensured through any number of design configurations. For example, in embodiments, spinal spacers

100 include one or more recesses 110 that permit bone ingrowth to promote stabilization of spinal spacer 100. In embodiments, cylindrically shaped spinal spacer

100 is encircled by screw threads 90 that anchor spinal spacer 100 in position between vertebrae 70 and 80, using techniques described below. In further embodiments, recesses 110 and/or threads 90 include osteogenic- promoting materials that promote bony ingrowth from vertebrae 70 and 80.

Additionally, the internal surface of elongate elements 20 and 30 and pivot joint 40 are optionally treated with materials which prevent bone ingrowth.

Spinal spacer 100 can be manufactured from any combination of biologically compatible material of suitable strength and durability, for example, stainless steel, chrome cobalt alloys, plastics and/or composite materials.

Size Considerations

Spinal spacer 100 is optionally manufactured in multiple configurations to fit a variety of shapes and sizes of vertebrae 70 and 80. For example, as seen in Figure 2A, spinal spacer 100 is optionally manufactured in a variety of longitudinal lengths 107 to fit vertebrae 70 and 80 having different anterior-posterior lengths. Additionally, spinal spacer 100 may be manufactured in a variety of diameters 109 to fit larger or smaller intervertebral spaces 97 (Figure 1C).

Flexion and Extension Preservation In additional embodiments, each spinal spacer 100 is optionally manufactured in a variety of flexion ranges of motion 161 and extension ranges of motion 160 to fit the implanted individual with a specific range of flexion and extension 51 (Figure 1C) that duplicates ranges of motion of the natural vertebrae 70 and 80. As seen in Figures 2B-2D, to determine the appropriate ranges of motion for a given spinal spacer 100, the following measurements are taken with the individual standing without any weight load:

«o - a neutral intervertebral angle 169 that is measured between vertebrae 70 and 80 along the adjacent vertebral plates, alternatively referred to herein as vertebral surfaces; f_max - a maximum flexion angle 172 that is measured along the adjacent vertebral plates with vertebrae 70 and 80 maximally flexed in a direction 171; and e_max - a maximum extension angle 132 that is measured along the adjacent vertebral plates with vertebrae 70 and 80 maximally extended in a direction 131.

Table 1, below, shows values for an exemplary adult male patient 98 (Figure 8) who presents for implantation of spinal spacer 100 following an industrial injury that has caused intervertebral space between lumbar 4 (L4) and lumbar 5 (L5) to partially collapse, resulting in intractable nerve pain. Besides injury to L4/L5, our exemplary adult male patient 98 is healthy with appropriate spinal range of motion.

Table 1

Patient 98 presents with following angular measurements with respect to L4/L5 in the table above . αo - neutral intervertebral angle 169 is 6 degrees; fmax - maximum flexion angle 172 is 13 degrees; and β_max - maximum extension angle 132 is 2 degrees.

The above noted values are entered into the two following formulae: 1. Extension range of motion 160 is equal to or greater than maximum extension angle 132, plus the neutral intervertebral angle 169:

[Extension range of motion 160 > e_max+ αo ] therefore, extension range of motion 160 will be equal to or greater than 8 degrees.

2. Flexion range of motion 161 is equal to or greater than maximum flexion angle 172, minus neutral intervertebral angle 169, and greater than or equal to zero:

[Flexion range of motion 161 >f_m^ - αo≥O] therefore, flexion range of motion 161 will be equal to or greater than 7 degrees.

As seen in Figure 3, vertebrae 70 and 80, shown in side cross-section have been implanted with spinal spacer 100 comprising the following ranges of motion: l)Extension range of motion 160 = 8 degrees 2) Flexion range of motion 161 = 7 degrees In addition to angular considerations, spinal spacer 100 can be configured to duplicate axial motion of vertebrae 70 and 80. For example, to substantially duplicate the position of transverse axis 47 with respect to vertebrae 70 and 80, pivot joint 40 may be offset along longitudinal axis 49 so that an anterior portion 22 is longer than a posterior portion 21. To prepare spinal spacer 100 for implantation, a few simple surgical instruments are required.

Surgical Instrumentation

Figure 4 shows an installation tool 24, comprising a handle 31, a tube 33 and a forward receptacle 139.

As seen in Figure 5, forward receptacle 139 includes arms 26 that are designed to grasp tool receptacles 111 on spinal spacer 100. As seen in Figure 6, forward receptacle 139 includes a stabilizer rod 28 that is placed between upper elongate element 20 and lower elongate element 30. As seen in Figure 7, arms 26 press radially inward to engage tool receptacles

111. Upper and lower elongate elements 20 and 30 are, thereby, pressed radially inward to secure against stabilizer rod 28; so the surgeon is confident that spinal spacer 100 can be easily manipulated without concern for it disconnecting from installation tool 24. In embodiments, implantation of spinal spacer 100 is relatively straightforward, taking advantage of natural anatomic positions, as seen in Figures 8-

14.

Implantation Technique Spinal spacer 100 is implanted using a posterior or posterior-lateral incision through the epidermal tissue and a bore extending anteriorly from the posterior of intervertebral space 97. Proper positioning of the patient before implantation can aid in proper placement of spinal spacer 100.

As seen in Figure 8, spine 182 on standing person 98 demonstrates curvatures associated with cervical 123, thoracic 125, lumbar 127 and sacral 129 sections. Each lordotic intervertebral angle 169 is angled lordotically so that lumbar vertebrae 70 and 80 have a greater distance between the anterior aspect of adjacent vertebrae 70 and 80 than the posterior aspect of adjacent vertebrae 70 and 80.

The sum of all lordotic intervertebral angles 197 of lumbar section 127 create a lordosis 121. Lordotic intervertebral angle 169 can make it difficult if not almost impossible to implant spinal spacer 100. To reduce lumbar lordosis 121, as seen in Figure 10, patient 98 is placed with the upper torso in a prone position on a surgical table 95, while hips and knees are in a kneeling position (not shown); causing vertebral plates adjacent to intervertebral space 97 to become substantially parallel. Parallel plates on vertebrae 70 and 80 facilitate drilling and tapping. In addition to facilitating drilling and tapping, placing the spine in the prone position in a manner that increases surgeon access to intervertebral space 97, for example in conjunction with the above-noted kneeling position, allows the surgeon to decompress nerve roots 163; remove stenosed bone on vertebrae 70 and 80; and remove any debris within intervertebral space 97, including cartilage and bone fragments.

To begin installation of spinal spacer 100, as seen in Figure 9, a drill bit 32 is bored through a portion of intervertebral space 97, optionally creating a bore having a central axis that is parallel to the adjacent plates of vertebrae 70 and 80.

In spinal spacers 100 having alternative cross-sectional configurations, for example, a rectangular shape, there are a variety of known bone cutting instruments that can be used to fashion a rectangular bore between vertebrae 70 and 80.

As seen in Figure 11, a thread tap 35 is rotated in clockwise direction 149 through the bore in intervertebral space 97.

An alternative to using thread tap 35 is provided by screw threads 90 comprising self-tapping threads that cut into spinal vertebrae 70 and 80 during rotation 149, so that spinal spacer 100 forms taps 93.

The tapped bore in intervertebral space 97 is now ready to receive spinal spacer 100. As seen in Figure 12, spinal spacer 100, previously loaded on installation tool 24, is rotated in direction 149 to pass in an anterior direction through the posterior aspect of intervertebral space 97. Installation tool 24 maintains upper elongate element 20 substantially parallel to lower elongate element 30.

Figure 13 demonstrates spinal spacer 100 fully installed, while Figure 14 demonstrates that spinal spacer 100 now functions with lordotic intervertebral angle 197 substantially duplicating the natural tilt between vertebrae 70 and 80.

While spinal spacer 100 has been described during installation between intervertebral spaces of lumbar section 127, it should be understood that the design of the present invention can be easily modified for installation in thoracic 125, cervical 123 sections and/or between lumber 127 and sacral 129 sections.

Alternative Pivot Joint Configurations

Alternative designs for pivot joint 40 can possibly provide advantages in installation, positioning, long-term stability and/or pain relief using spinal spacer 100. In embodiments, center of rotation 103 through which transverse axis 47 passes remains substantially static during pivoting of vertebrae 70 and 80 and is referred to herein as a static center of rotation 103. However, other configurations of pivot 40 allow some additional movement between vertebrae 70 and 80. Figure 15 shows an optional embodiment of pivot joint 40 wherein upper depression 43 is elongate, thereby forming a shifting center of rotation 101 that shifts along longitudinal axis 49 during pivoting of vertebrae 70 and 80.

Upper depression 43 may be configured in this elongate fashion and/or in a variety of alternative configurations in order to duplicate natural anatomic movement between spinal vertebrae 70 and 80; the term "natural anatomic movement" referring to movement between vertebrae 70 and 80 in the natural human state, without pathology and/or spinal spacer 100. Center of rotation 101 that shifts with respect to vertebrae 70 and 80 whether along longitudinal axis 49 or transverse axis 47, is referred to herein as a virtual center of rotation 101. In embodiments, spinal spacer can be configured to facilitate manipulation of vertebrae 70 and 80 after installing a first spinal spacer. As seen in Figure 16, spinal spacers 100 include ball and socket joints 151. After first spinal spacer 100 is installed, the surgeon has the option to manipulate spinal vertebra 70 with respect to spinal vertebra 80 (not shown) in motions of bending 53, and axial rotation 59 around ball and socket joint 151; motions which aid the surgeon in manipulating vertebrae 70 and 80 to facilitate installation of second spinal spacer 100.

It is expected that during the life of a patent maturing from this application many relevant spinal spacers and/or spinal spacer materials will be developed and the scope of the term spinal spacer is intended to include all such new technologies a priori.

As used herein the term "about" refers to ± 10 %. The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to". This term encompasses the terms "consisting of and "consisting essentially of.

The phrase "consisting essentially of means that the composition or method may include additional ingredients and/or steps, but only if the additional ingredients and/or steps do not materially alter the basic and novel characteristics of the claimed composition or method.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity, and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween. As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

As used herein, the term "treating" includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition. Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

Experimental Examples

The inventors have found that in certain cases, restoration of spinal flexion and extension while stabilizing the spine against lateral and rotatory motion, presents some advantages over artificial intervertebral spacers that additionally restore lateral bending, and axial rotation, of the spine.

Such advantages include maintenance of pain reduction. While the exact mechanism by which the present invention provides pain reduction is not known, it is presumed that the motions of spinal lateral bending and axial rotation can cause temporary narrowing of the intervertebral space that irritates exiting spinal root.

Additionally, the simple posterior installation of the present invention, wherein extensive anterior dissection and/or posterior vertebral manipulation are avoided, appears to possibly play a role in the above-noted observations of maintenance of pain reduction.

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, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the terms intervertebral spacer and/or intervertebral disk include support of all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims

WHAT IS CLAIMED IS:

1. A method for installing a spinal spacer, the method comprising: i) placing a human in a prone position; ii) reducing a lordotic angle between two adjacent vertebrae; iii) incising an incision in epidermal tissue adjacent to a posterior portion of a spine of said human; iv) boring two bores through said incision between two spinal vertebrae; and v) placing a pivot within each of said two bores.

2. The method according to claim 1, wherein pivoting motion between said two spinal vertebrae is limited to flexion and extension.

3. The method according to claim 1, including: step vi) restoring said lordotic angle between said two spinal vertebrae.

4. The method according to claim 1, wherein at least one pivot is configured to duplicate at least one parameter associated with said two spinal vertebrae, said at least one parameter comprising at least one of: i) a maximum intervertebral flexion angle; and ii) a maximum intervertebral extension angle.

5. A method for installing a spinal spacer, the method comprising: i) incising an incision in epidermal tissue adjacent to a posterior portion of a spine of a human; ii) boring a first bore through said incision between two spinal vertebrae, a spinal process, and a first spinal facet; iii) placing a first pivot within said first bore; iv) boring a second bore between said two spinal vertebrae, said spinal process, and a second spinal facet; v) placing a second pivot within said second bore; and vi) pivoting said two spinal vertebrae on said pivot.

6. The method according to claim 5, wherein step iii includes pivoting said first pivot in at least one of: a) flexion and extension; b) lateral bending; and c) axial rotation.

7. The method according to any one of claims 5 and 6 wherein said pivoting occurs around a virtual center of rotation.

8. The method according to claim 5, wherein step v includes limiting the pivoting motion between said two spinal vertebrae to flexion and extension.

9. The method according to claim 5, wherein at least one of said first pivot and said second pivot is configured to duplicate at least one parameter associated with said two spinal vertebrae, said at least one parameter comprising at least one of: i) a maximum intervertebral flexion angle; and ii) a maximum intervertebral extension angle.

10. A method for installing a spinal spacer, the method comprising: i) incising an incision in epidermal tissue adjacent to a posterior portion of a spine of a human; ii) boring two bores through said incision between two spinal vertebrae; iii) placing a pivot assembly within each of said bores; iv) limiting a pivot motion provided by said pivots to flexion and extension; and v) pivoting said two spinal vertebrae in flexion and extension.

11. The method according to any one of claims 5 and 10 wherein prior to step 1, said human is placed in the prone position in a manner that reduces an intervertebral angle between adjacent surfaces of said two spinal vertebrae.

12. The method according to any one of claims I₅ 5, 8, and 10, wherein said pivoting occurs around a static center of rotation.

13. An intra-articular spinal spacing device having a longitudinal axis, the device comprising: i) an upper elongate element having a lower surface; ii) a lower elongate element having an upper surface; and iii) a pivot joint operatively associated with said upper surface and said lower surface, said pivot joint offsetting said upper surface from said lower surface at least in the vicinity of said pivot joint.

14. The device according to claim 13, wherein pivot movement around said pivot joint is limited by contact between said lower surface and said upper surface at adjacent longitudinal ends.

15. The device according to claim 13, wherein said pivot joint is located eccentrically along the longitudinal axis.

16. The device according to claim 15, wherein during pivoting motion, the maximum offset between said upper and lower surfaces on a first side of said pivot is greater than the maximum offset between said upper and lower surfaces on a second side of said pivot.

17. The device according to claim 13, including an outer surface having at least one stabilizing extension extending outwardly therefrom.

18. The device according to claim 13, including an outer surface comprising a round cylinder.

19. The device according to claim 18, wherein said outer surface includes at least one screw thread extending outwardly therefrom.

20. An intra-articular spinal spacing system, the system comprising two elongate pivoting elements: a) a first elongate pivoting element having a first longitudinal axis and a first average cross-sectional diameter; and b) a second elongate pivoting element having a second longitudinalaxis and a second average cross-sectional diameter, wherein: the sum of said first and second average cross-sectional diameters is less than a transverse distance across a human intervertebral space.

21. The system according to claim 20, wherein at least one of said two elongate pivoting elements include: i) an upper member; ii) a lower member; and iii) a pivot joint operatively associated with said upper member and said lower member.

22. The system according to claim 21, wherein: a) said upper member includes a lower surface; b) said lower member includes an upper surface; and c) said upper surface is offset from said lower surface at least in the vicinity of said pivot joint.

23. The system according to claim 21, including an axis passing through said pivot joint of said first elongate pivoting element and said pivot joint of said second elongate pivoting element, said center of rotation being transverse to the longitudinal axis of said at least one elongate pivoting element.

24. The system according to claim 21, wherein said pivot joint includes a spherical extension and said pivot joint moves in at least one of: a) flexion and extension; b) lateral bending; and c) axial rotation.

25. The system according to any one of claims 21, 22, 23 and 24, wherein motion around a center of rotation passing through said pivot joints is limited to flexion and extension.

26. The system according to claim 20, wherein at least one of said two elongate pivoting elements includes an outer surface having at least one stabilizing extension extending outwardly therefrom.

27. The system according to claim 20, wherein at least one of said two elongate pivoting elements includes an outer surface comprising a round cylinder.

28. The system according to claim 26, wherein said outer surface includes at least one screw thread extending radially outwardly therefrom.