HK1118005A - Implant device used in mimimally invasive facet joint hemi-arthroplasty - Google Patents

Description

Implant device for minimally invasive facet joint hemi-arthroplasty

Technical Field

The present invention generally relates to a device for use in minimally invasive spinal surgery. And more particularly to a preformed, pre-formed metal implant for implantation using an arthroscopic portal or conventional open surgical approach to effect facet joint hemi-joint replacement to recreate the superior facet of any or all 48 vertebrae from the inferior occiput-C1 to L5-S1.

Background

In the united states alone, about 10% of the total population suffers from back pain at some point in the next 12 months. More people will contract back pain in the next year than any other injury or illness besides the common cold and flu. About one third of patients do not recover and have to live with persistent disabling symptoms. This number will increase year by year.

One of the root causes of back pain, particularly persistent disabling back pain, is the facet joints, also called facet joints, located behind adjacent vertebrae in the spine that allow spinal motion.

The surgical protocols currently available for millions of people with facet joint dysfunction are complex, invasive, high-risk procedures requiring pedicle screw fixation, substantial reduction or removal of the natural joint, and replacement with prosthetic devices such as those described in us patent 6610091, 6579319, 6132464, 6113637 and us patent application 2003/0028250. Typically, this prior art requires a recovery period of 6 months to 24 months long, and the consequences are uncertain. High risk equates to frequent complaints, driving the development of non-surgical symptomatic treatments as the consequences of the disease or injury become increasingly worse.

With the advent of new, safer, less invasive surgical methods and techniques, the development of spinal surgery now outpaces the speed of any other orthopedic component. Its development is further driven by a great demand. There is a need for improvements in devices for spinal joints.

Disclosure of Invention

The present invention provides a preformed metal implant for use in minimally invasive spinal surgery. The present invention uses a preformed metal overlay for a spinal facet joint for a resurfacing of a diseased, painful, necrotic or deformed articular surface, with three advantages over larger prosthetic implants; that is, (1) the use of a thin metal coating allows for minimally invasive insertion, which is safer, less traumatic, and recovery time much shorter than the revision surgery method; (2) the overlay does not require the use of cement, pedicle screws, or other fixation methods that loosen their fixation over time; and (3) the implant has two fins or blades to provide lateral stability, and two teeth to provide temporary fixation, and a rough or porous inner surface, which may be adapted to the growing bone, providing permanent natural fixation. The insert also has a polished outer surface to allow smooth, natural, painless articulation of the joint.

The insert is specifically designed for use in arthroscopic type portals for independent procedures, but may also be used in traditional open surgery. The implant provides unique stronger and better resurfacing and is useful in, but not limited to: (1) assisted spinal instrumented fusion, when inserted directly into two facet joints above and below the two joints adjacent to the instrumentation used, thereby eliminating the risk of concomitant post-operative facet joint pain due to additional stress applied to the facet joints, (2) adjacent facet joint resurfacing surfaces directly above and below the disc replacement, concomitant post-operative facet joint pain generated by the elimination of additional stress applied to the facet joints by the disc replacement, and (3) as a stand-alone treatment for diseased, painful, or necrotic facet joints.

The present invention accomplishes its goal of resurfacing a painful, diseased or necrotic facet joint by providing an implant for resurfacing to replace the articular surface with a small metal-on-bone overlay. The overlay is constructed of cobalt chromium or other biocompatible metal or metal alloy suitable for joint hemi-arthroplasty, is one of a plurality of sizes for each vertebra of the spinal column, is likewise sized for different facet joints or joint groups in the spinal column, and is attached to the joint using simple methods without the need for screws or cements. An arthroscopic type portal may be used to access the facet joints without the need for open surgery, hospitalization, and long recovery periods. The method may also be used as an adjunct to other procedures, such as fusion by instruments and disc replacement in traditional open surgery. Since the side of the implant that is attached to the bone is porous, the bone heals on it, permanently fixing it in place. A uniquely designed set of blades and teeth provide temporary fixation to the joint, preventing movement. The crimping system holds the implant in place, holding it firmly until the bone is fully grown. The side in contact with the joint is highly polished, providing a smooth, virtually frictionless surface with little wear and tear. The interior is rough or porous to provide a compliant surface for the growing bone.

In accordance with one broad aspect of the present invention, a unique metallic repair coating is provided. The metal overlay is generally shaped to the natural-shaped contours of the bone surface it reproduces and is highly polished on the outside surface to provide frictionless articulation of the joint and internally rough or porous to provide a surface to encourage natural bone growth into the overlay, thereby providing permanent fixation. In the interim between implantation and bone in-growth, the coating is mechanically bent into position using two teeth opposite each other and one to two blades on the inner surface of the implant that encroach into the bone to prevent lateral movement. The overlay is also held in place by the natural pressure of the upper and lower sides of the joint coming together in their natural position.

The system for inserting the prosthetic overlay includes any number of instruments for preparing the joint and the implant to be placed using minimally invasive surgical arthroscopic techniques to access the joint, including a guide probe for determining the correct facet joint angle; distractors to assist in distraction of the vertebrae to better access the joint; osteotomes, for making small cuts in bone to prepare a surface for an implant; a hand drill for matching the bone to the implant shape; a hammer for striking the implant in position; and a crimper for securing the implant against movement prior to healing; and an implant. By way of example only, the guide probe may include a planar blade or rasp to remove any bone spurs or hyperosteogeny and flatten the facet joint surface in preparation for placement of the implant.

Drawings

Many advantages of the present invention will be apparent to those skilled in the art upon reading this specification in light of the accompanying drawing figures, in which like reference numerals are used to designate like parts, and in which

FIG. 1 shows a top perspective view of the right side of an implant;

FIG. 2 shows a bottom, left side perspective view of the implant;

FIG. 3 shows a cross-sectional view taken along line 3-3 of FIG. 1;

FIG. 4 shows a tool for preparing the facet joint to receive the implant;

FIG. 5 shows a tool inserted into a facet joint;

FIG. 6 shows the insert about to be installed in a facet joint;

FIG. 7 shows the insert embedded in a facet joint;

fig. 8 shows a cross-sectional view taken along line 8-8 of fig. 7.

Detailed Description

Referring to fig. 1, a prosthetic implant 10 of the present invention has a highly polished concave outer back portion 12 and a highly polished convex surface on a top portion 14. The highly polished surface is a cobalt-chromium alloy, titanium alloy, or other biocompatible material capable of forming a smooth highly polished surface. Referring to fig. 2, the inner convex surface is a rough surface 18 to promote new bone growth and attachment. Blades 20 and 22, secured to inner surface 16, bite into the bone to facilitate fixation. The lower surface 24 of the top of the implant 10 is recessed to form a tight fit over the bone, as shown in fig. 7 and 8. The teeth 26 and 28 are intended to embed into the adjacent bone to prevent migration of the implant 10.

A preparation tool 30 is used to slightly distract the facet joint 32 prior to embedding the implant in the joint 32. The tool end 34 is inserted into the joint 32 to provide sufficient space for insertion of the implant 10 into the joint 32, as shown in fig. 7 and 8.

The use of the prosthetic implant 10 has two advantages over the prior art:

(1) it is small, low risk, fast (20 minutes per clinic visit, compared to 3 hours of hospitalization and three subsequent days) and has a short recovery period of several weeks (compared to 6 to 24 months); and

(2) it has a high success rate, does not exclude other surgical operations, and is not limiting and permanent.

The object of the present invention is to overcome or at least ameliorate the disadvantages of the prior art by:

reversing the risk/profitability of prior methods as opposed to the present invention;

independent minimally invasive approaches, compared to major open surgery;

as an adjunct to major open surgery associated with long fusion and disc replacement surgery to strengthen adjacent facet joints;

outpatient surgery compared to hospitalized surgery (about 20 minutes per joint compared to hours);

the morbidity is reduced;

reducing blood loss;

shortening the time under the arthroscope;

the risk is reduced;

the recovery period is obviously shortened;

the scars are minimal, reducing the risk of unsuccessful back syndrome and improving the outcome of revision surgery;

the risk of postoperative infection is reduced by significantly reducing operating room time and soft tissue damage;

the functional life of long vertebra fusion and intervertebral disc replacement is prolonged;

other surgical or non-invasive treatment options are not excluded; and

high success rates have been shown by the use of approved procedures facilitated by arthroscopic techniques and resurfacing implants.

It is anticipated that the utility of the method, instruments and implants will increase the number of surgeries performed, as it provides a first safe outpatient solution for the primary cause of joint pain. The inventors also expect that almost all patients receiving this procedure will be able to walk the day of surgery and fully recover function within a few weeks. The prior art surgical protocol requires hospitalization for about three days and a recovery period of six to twenty-four months.

In addition to the apparent absolute clinical outcome, the significant beneficial effects on disability, worker reimbursement, and financing of medical insurance are also considerable.

The facet implant units of the spine are calculated for each joint. Each patient had two joints per vertebra, six vertebrae in the lumbar spine (T12-L1 to L5-S1), or 12 lumbar, 14 cervical and 28 thoracic joints. Each procedure may involve multiple joints with an average probability of 4 per patient.

The present invention achieves the objects of the invention of reducing, preventing or eliminating spinal facet joint pain by providing a resurfacing implant that replaces the articular surface with a small metal coating on the bone. The overlay is constructed of cobalt chromium, a material previously approved by the FDA for other hemi-arthroplasty procedures, or other metal construct that can be safely used, is sized for one of a plurality of sizes of individual vertebrae of the spine, is similarly sized for different joints, and is secured to the joint using simple methods without the aid of screws, cements, and conventionally designed instruments. The joint is accessed using an arthroscopic portal, eliminating the need for open surgery, hospitalization, and long recovery periods (unless the procedure is used to assist other procedures such as instrumented fusion and disc replacement in traditional open surgery). Because the side that is fixed to the bone is porous, the bone heals on it, permanently fixing it in place. The uniquely designed blades and teeth are used for the joint and the unique crimping system secures the implant in place, holding it firmly until bone growth is complete. The side in contact with the joint is highly polished, providing a smooth, virtually frictionless surface with little wear and tear. Resurfacing implants are firmly anchored porous hemiarthroplasty of the facet joints of the spine.

The metal overlay is generally shaped to the natural shape of the bone of the resurfacing, with the outer surface being highly polished to provide a frictionless connection of the joint, and the inner surface being rough and porous to provide a surface to encourage natural bone growth into the overlay, thereby providing permanent fixation. In the interim between implantation and solid growth, the coating is mechanically crimped into place by using two teeth opposed to each other that bite into the bone to prevent migration. The overlay is further held in place by the natural pressure of the upper and lower portions of the joint coming together in their natural position.

The system includes any number of instruments 30 for preparing a joint 32 and an implant 10 to be placed for access to the joint using minimally invasive surgical joint replacement techniques, the instruments 30 including a guide probe for determining the correct facet joint angle; distractors to assist in distraction of the vertebrae to better access the joint; osteotomes, for making small cuts in bone to prepare a surface for an implant; a hand drill for matching the bone to the implant shape; a hammer for striking the implant in position; and a crimper for securing the implant against movement prior to healing; and an implant. By way of example only, the guide probe may include a planar blade or rasp to remove any bone spurs or hyperosteogeny and flatten the facet joint surface in preparation for placement of the implant.

Equivalent components may be used in place of the implant components of the present invention to provide substantially the same function in substantially the same way to achieve substantially the same result.

Claims (17)

1. A prosthetic implant for use in minimally invasive facet joint hemi-arthroplasty, the implant comprising:

an inverted L-shaped metal body having a convex top integrally formed with a concave downwardly extending portion at a rear edge, the top and downwardly extending portions having highly polished outer surfaces of a material that is biocompatible with bone;

a concave lower surface below the top, and a convex inner roughened surface on the downwardly extending portion; and

at least one vane integrally formed with the convex inner roughened surface, and a pair of teeth extending from the convex top leading edge.

2. The prosthetic implant as defined in claim 1, wherein said highly polished outer surface is a cobalt-chromium alloy.

3. The prosthetic implant as defined in claim 1, wherein said highly polished outer surface is a titanium alloy.

4. The prosthetic implant as defined in claim 1, wherein said convex inner rough surface is porous and compatible with bone.

5. The prosthetic implant as defined in claim 1, wherein there are two lobes integrally formed with the convex inner roughened surface.

6. A prosthetic implant for installation in a facet joint, the implant comprising:

an inverted L-shaped metal body having a convex top integrally formed at a rear edge with a concave downwardly extending portion, the top and downwardly extending portions having highly polished outer surfaces of a bone biocompatible material;

a concave lower surface below the top, and a convex inner roughened surface on the downwardly extending portion; and

at least one vane integrally formed with the convex inner roughened surface, and a pair of teeth extending from the convex top leading edge.

7. The prosthetic implant mounted in a facet joint according to claim 6, wherein the highly polished outer surface is juxtaposed with oppositely positioned bone in the facet joint.

8. The prosthetic implant for installation in a facet joint according to claim 7, wherein the highly polished outer surface is a cobalt-chromium alloy.

9. The prosthetic implant for installation in a facet joint according to claim 7, wherein the highly polished outer surface is a titanium alloy.

10. The prosthetic implant mounted in a facet joint according to claim 6, wherein the roughened surface conforms to the shape of the juxtaposed bone.

11. The prosthetic implant for installation in a facet joint according to claim 10, wherein there are two blades integrally formed with the convex inner roughened surface, said blades cutting into juxtaposed bone.

12. The prosthetic implant mounted in a facet joint according to claim 6, wherein the pair of teeth extend downwardly into the bone.

13. A system for installing a prosthetic implant in a facet joint using a tool to distract the facet joint sufficiently large to allow entry of the implant, the implant comprising:

an inverted L-shaped metal body having a convex top integrally formed with a concave downwardly extending portion at a rear edge, the top and downwardly extending portions having highly polished outer surfaces of a bone biocompatible material;

a concave lower surface below the top, and a convex inner roughened surface on the downwardly extending portion; and

at least one vane integrally formed with the convex inner roughened surface, and a pair of teeth extending from the convex top leading edge.

14. The system of claim 13, wherein the implant has a highly polished cobalt-chromium alloy outer surface.

15. The system of claim 13, wherein the implant has a highly polished outer surface of titanium alloy.

16. The system of claim 13, wherein the implant has two blades integrally formed with a convex inner rough surface.

17. The system of claim 13, wherein the implant convex inner rough surface is porous and compatible with bone.