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Tissue prosthesis and a method of, and equipment for, forming a tissue prosthesis

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Tissue prosthesis and a method of, and equipment for, forming a tissue prosthesis


A tissue prosthesis 100 comprises an envelope 38 of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity 36 formed at a site 10 in a patient's body. A filler material 60 is received in a fluent state in the envelope 38. The filler material 60 is of the same class of material as the envelope 38 to form, when cured, together with the envelope 38, a unified structure.
Related Terms: Fluent

Browse recent Spinecell Private Limited patents - Kogarah, AU
Inventors: ASHISH D. DIWAN, ZORAN MILIJASEVIC, JOHNATHON CHOI, SANDRA FISHER
USPTO Applicaton #: #20120290095 - Class: 623 1716 (USPTO) - 11/15/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Implantable Prosthesis >Bone >Spine Bone >Including Spinal Disc Spacer Between Adjacent Spine Bones

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The Patent Description & Claims data below is from USPTO Patent Application 20120290095, Tissue prosthesis and a method of, and equipment for, forming a tissue prosthesis.

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CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/AU2006/001176, filed on Aug. 15, 2006, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/708,670, filed on Aug. 15, 2005, the full disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the repair of tissue in a body and, more particularly, to a method of, and equipment for, forming a tissue prosthesis in situ and to a tissue prosthesis. The invention has particular, but not necessarily exclusive, application in the field of minimally invasive intervertebral disc nucleus repair.

Joints of the musculoskeletal system of the human or animal body rely on the presence of healthy cartilaginous tissue for proper operation. Cartilaginous tissue can degenerate due to a number of causes, eg. age or injury. Degradation of the tissue can reach a point where movement can cause severe discomfort and pain.

In the case of the spinal column, it comprises a series of 26 mobile vertebral bones or vertebrae connected by 75 stable articulations that control motion. The vertebrae are generally divided into posterior and anterior elements by thick pillows of bone called pedicles. The anterior element of the vertebra is a kidney shaped prism of bone with a concavity directed posteriorly and has flat superior and inferior surfaces called end plates. An intervertebral disc is sandwiched between adjacent pairs of vertebrae forming a joint between the adjacent pair of vertebrae. These discs are viscoelastic structures comprising a layer of strong deformable soft tissue. The intervertebral discs are subjected to a considerable variety of forces and moments resulting from the movements and loads of the spinal column. Each intervertebral disc has two components being the annulus fibrosis circumscribing a nucleus pulposus. The intervertebral disc cooperates with the end plates of the vertebrae between which it is sandwiched.

The primary function of the nucleus pulposus of the disc is to give the disc its elasticity and compressibility characteristics to assist in sustaining and transmitting weight. The annulus fibrosis contains and limits the expansion of the nucleus pulposus during compression and also holds together successive vertebrae, resisting tension and torsion in the spine. The end plates of the vertebrae are responsible for the influx of nutrients into the disc and the efflux of waste products from within the disc.

With age or injury, a degenerative process of the disc may occur whereby its structures undergo morphological and biological changes affecting the efficiency with which the disc operates. Thus, the nucleus pulposus may reduce in volume and dehydrate resulting in a load reduction on the nucleus pulposus, a loss in intradiscal pressure and, hence, additional loading on the annulus fibrosis. In a normally functioning disc, the intradiscal pressure generated results in deformation of the end plates of the adjacent vertebrae generating the natural pumping action which assists in the influx of the nutrients and the efflux of waste products as stated above. A drop in intradiscal pressure therefore results in less end plate deformation. The nutrients supplied to the discal tissue is reduced and metabolic wastes are not removed with the same efficiency. This contributes to a degenerative cascade.

Radial and circumferential tears, cracks and fissures may begin to appear within the annulus fibrosis. If these defects do not heal, some of the nuclear material may begin to migrate into the defects in the annulus fibrosis. Migration of the nuclear material into the annulus fibrosis may cause stretching and delamination of layers of the annulus fibrosis resulting in back pain due to stimulation of the sinu-vertebral nerve. An intervertebral disc without a competent nucleus is unable to function properly. Further, since the spine is a cooperative system of elements, altering the structure and mechanics at one location of the spinal column may significantly increase stresses experienced at adjacent locations thereby further contributing to the degenerative cascade.

In the past, operative intervention has occurred to relieve lower back pain arising from intervertebral disc degeneration. Most of this operative intervention has been by way of a discectomy where leaking nuclear material is removed or, alternatively, fusion. The primary purpose of a discectomy is to excise any disc material that is impinging on the spinal nerve causing pain or sensory changes. Fusion means eliminating a motion segment between two vertebrae by use of a bone graft and sometimes internal fixation. Biomechanical studies show that fusion alters the biomechanics of the spine and causes increased stresses to be experienced at the junction between the fused and unfused segments. This promotes degeneration and begins the degenerative cycle anew. Clearly, being an invasive operative procedure, fusion is a risky procedure with no guarantee of success.

Due to the minimal success rate of the previous two procedures, as well as their inability to restore complete function to the spinal column, alternative treatments have been sought in the form of artificial disc replacements. Theoretical advantages of artificial disc replacement over a fusion procedure include preservation or restoration of segmental motion in the spine, restoration of intervertebral architecture and foraminal height, sparing of adjacent segments of the spine from abnormal stresses and restoration of normal biomechanics across the lumbar spine. The established artificial disc replacement procedure consists of techniques that require a surgical incision on the abdomen, retraction of large blood vessels, a total excision of the anterior longitudinal ligament, anterior and posterior annulus along with the nucleus and near total removal of the lateral annulus and implantation of an articulated prosthesis. This is a major spinal column reconstruction operation.

There is therefore a need for a surgical procedure which, as far as possible, restores the biomechanics of joints such as those between adjacent vertebrae of the spine by the provision of a tissue prosthesis mimicking natural, healthy cartilaginous tissue.

2. Brief Summary of the Invention

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

According to a first aspect of the invention, there is provided a tissue prosthesis which comprises: [0013] an envelope of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at a site in a patient\'s body; and [0014] a filler material received in a fluent state in the envelope, the filler material being of the same class of material as the envelope to form, when cured, together with the envelope, a unified structure.

The envelope may be of an elastomeric material capable of expanding to up to 100 times its relaxed state. Further, the filler material may be of an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. The envelope may be expanded to be stretched and retained under tension after being charged with the filler material.

In this specification, the term “expanded” and its variations is to be understood as meaning “stretched elastically”.

Both the envelope and the filler material may be of an elastomeric material having a Shore Hardness in the range of between about 5 to 90 A. Preferably, the envelope and the filler material are of a silicone rubber material. However, to promote bonding between the envelope and the filler material, the envelope and the filler material may be of different grades of silicone rubber material and may be pre-treated in different ways prior to use.

The envelope may include a neck portion, the neck portion defining a zone of weakness for facilitating separation of the envelope from a delivery device. Further, the envelope may include a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. In an embodiment, the prosthesis may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

The envelope may carry a marker arrangement on an exterior surface for enabling the envelope to be used to assess dimensions and a shape of the cavity and positioning of the envelope in the cavity.

According to a second aspect of the invention, there is provided a tissue prosthesis which comprises:

an envelope of a foraminous, chemically inert material shaped to conform to an interior surface of a cavity formed at a site in a patient\'s body in which the envelope is to be placed; and

a filler material received in a fluent state in the envelope, the filler material being of an elastomeric material which, prior to being cured, is urged into foramens of the envelope to form an integrated structure which inhibits relative movement between the envelope and the filler material, in use, and once the filler material has cured.

The envelope may be of a knitted biological or synthetic polymeric material. More particularly, the envelope may be of a knitted polyester material, such as polyethylene terephthalate (PET). Further, the envelope may be coated with a material of the same class as the filler material.

Once again, the envelope may include a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. The prosthesis may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

According to a third aspect of the invention, there is provided a method of forming a tissue prosthesis in situ at a site in a patient\'s body, the method comprising:

accessing the site in the patient\'s body;

if necessary, removing tissue from the site to form a cavity;

inserting an envelope of a biologically inert, elastically deformable material into the cavity;

charging a filler material, in a fluent state, into the envelope to cause the envelope to expand and conform to the shape of the cavity; and

allowing the filler material to cure, the filler material being of the same class of material as the envelope so that, when the filler material has cured, a unified prosthesis is formed.

The method may include accessing the site by inserting an introducer through an aperture formed in tissue associated with the site and removing nuclear tissue, if required, from the site. The nuclear material may be removed by mechanical, ultrasonic, laser, Argon gas or radio frequency ablation, or the like, in combination with suction and irrigation. For example, mechanical removal may be effected by using a reaming-type tool.

Once the nuclear tissue has been removed, the method may include checking dimensions of the cavity so formed. Thus, the method may include using the envelope, containing suitable markers, to check the dimensions of the cavity. This may be effected by inflating the envelope using a suitable fluid such as a water/saline solution. Instead of using the envelope with markers, the method may include using a flexible wire fed down the introducer and checking the position of the wire using a fluoroscopic x-ray technique once the wire is in position. In yet a further way of checking the dimensions of the cavity, the method may include deploying a jacket of similar dimensions to the envelope in the cavity, inflating the jacket with the water/saline solution and, using a fluoroscope, detecting the periphery of the jacket by radio opaque markers on an outer surface of the jacket.

Once the envelope has been placed in position, the method may include checking the integrity of the envelope, i.e. to ensure that the envelope does not have any leaks or other defects. This may be effected by filling the envelope with the water/saline solution.

The method may include evacuating an interior of the envelope to inhibit the formation or entrapment of fluid bubbles in the filler material. Instead, the method may include commencing filling of the envelope from a distal end of the envelope and progressively filling the envelope towards a proximal end of the envelope (by withdrawing a filler tube or allowing the material buoyancy to lift the filler tube) to inhibit the formation or entrapment of fluid bubbles in the filler material. In the latter case, either a delivery device by which the envelope is introduced into the cavity or the envelope may define a formation allowing the escape of air as the envelope is charged with the filler material.

The method may include, once filling of the envelope has been completed and a filler element withdrawn, occluding the aperture in the tissue of the site. Occluding the aperture may comprise closing it off by a non-return valve or by crimping closed a neck portion of the envelope. A removable tube may be nested over the delivery device and may be propelled distally to remove the envelope and valve from the delivery device.

The method may include attaching the envelope to a distal end of a tubular delivery device and everting the envelope on the distal end prior to insertion of the delivery device into the introducer for delivery of the envelope into the cavity of the site.

Preferably, the method includes accessing the site percutaneously in a minimally invasive surgical procedure. Hence, the method may be used to perform minimally invasive intervertebral disc nucleus replacement and may comprise: [0038] forming an aperture in an annulus fibrosis of the disc percutaneously; [0039] extracting a nucleus pulposus of the disc to form a disc cavity bounded by the annulus fibrosis of the disc and end plates of vertebrae between which the disc is located; [0040] inserting the envelope, in a relaxed state, into the cavity through the aperture; [0041] charging the filler material into the envelope to cause the envelope to expand and conform to the shape of the disc cavity; [0042] allowing the filler material to cure to form, together with the envelope, the unified prosthesis; and [0043] occluding the aperture.

Preferably, the method includes expanding and stretching the walls of the envelope and retaining the envelope under tension after charging it with filler material.

According to a fourth aspect of the invention, there is provided equipment for forming a tissue prosthesis in situ at a site in a patient\'s body, the equipment comprising: [0046] a delivery device displaceably receivable in a lumen of an introducer, the delivery device defining a passageway; [0047] an envelope carried at a distal end of the delivery device, the envelope being of a biologically inert, elastically deformable material capable of being expanded to conform to an interior surface of a cavity formed at the site; and [0048] a supply of a filler material chargeable in a fluent state into the envelope through the passageway of the delivery device, the filler material being of the same class of material as the envelope to form, when cured, together with the envelope, a unified prosthesis.

The equipment may include an aperture forming element to form an aperture into the site, the aperture forming element being receivable through the introducer for delivery to the site. The aperture forming element may, for example, be a trocar.

Further, the equipment may include a tissue removal mechanism insertable through the aperture for removing tissue, if required, to form the cavity. As indicated above, the tissue removal mechanism may comprise mechanical, ultrasonic, laser, Argon gas or radio frequency ablation mechanisms, or the like in combination with suction and irrigation. For example, the tissue removal mechanism may be a reaming-type tool.

The envelope may be of an elastomeric material capable of expanding to up to 100 times its relaxed state. The envelope is preferably expanded to be stretched and retained under tension after being charged with the filler material.

The envelope may include a neck portion, the neck portion defining a zone of weakness for facilitating separation of the envelope from the delivery device. Further, the envelope may includes a flow control device arranged at an inlet opening to the envelope for inhibiting back flow of the filler material from the envelope. The equipment may include a flow control defining member, the flow control defining member being separate from the envelope and being arranged at the inlet opening to the envelope.

The envelope may carry a marker arrangement on an exterior surface for enabling the envelope to be used to assess dimensions and a shape of the cavity and positioning of the envelope in the cavity.

The filler material may be of an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. More particularly, the envelope and the filler material may be of an elastomeric material having a Shore Hardness in the range of about 5 to 90 A. The envelope and the filler material may be of a silicone rubber material.

The equipment may include a dispenser containing the supply of filler material.

Further, the equipment may include a sensing arrangement configured to sense a parameter of the filler material charged into the envelope. The sensing arrangement may comprise a pressure sensor for sensing the pressure of filler material charged into the envelope, a temperature sensor for sensing the temperature of the filler material charged into the envelope, be configured to sense the quantity of filler material charged into the envelope and/or comprise a flow rate sensor for sensing the rate of flow of the filler material into the envelope. Further, the sensing arrangement may be configured to sense the presence of air bubbles in the filler material charged into the envelope.

According to a fifth aspect of the invention, there is provided equipment for forming a tissue prosthesis in situ at a site in a patient\'s body, the equipment comprising

a tubular delivery device, the delivery device defining a passageway, an envelope of the prosthesis being mountable to a distal end of the delivery device to be received in a cavity at the site;

a filler member receivable in the passageway of the delivery device, the filler member being receivable with clearance in the passageway to define a gap to enable fluid to be evacuated at least from the envelope; and

a removal mechanism carried by the delivery device for enabling the envelope to be removed from the delivery device after the envelope has been charged with filler material via the filler member.

The equipment may include a tubular introducer and an aperture forming element, such as a trocar, to form an aperture at the site, the aperture forming element being receivable through the introducer for delivery to the site.

Further, the equipment may include a tissue removal mechanism insertable through the aperture for removing tissue, if required, to form the cavity.

The introducer and the delivery device may include a retaining arrangement for retaining the delivery device with respect to the introducer.



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stats Patent Info
Application #
US 20120290095 A1
Publish Date
11/15/2012
Document #
13558204
File Date
07/25/2012
USPTO Class
623 1716
Other USPTO Classes
International Class
61F2/42
Drawings
13


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