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

Abstract

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.

1 . A tissue prosthesis, comprising:
 an envelope expandable under the force of a fluent filler material to expand from a relaxed state to an inflated state;   said envelope being sized to expand up to 100 times its relaxed state to facilitate said envelope self anchoring to an irregularly shaped set of walls within a nucleus pulposus cavity of an intervertebral disc when said envelope reaches said inflated state;   said envelope and said filler material forming an integrated structure when said envelope reaches said inflated state and said fluent filler material cures to form a structure for mimicking natural, healthy cartilaginous tissue within said nucleus pulposus cavity;   wherein said envelope includes a neck defining an inlet to a filler material receiving space within said envelope;   wherein said envelope further includes a sleeve having a zone of weakness, said sleeve defining a valve disposed in said inlet;   wherein said envelope still further includes a bead formed adjacent to said inlet to form a fluid passageway to enable air within said filler material receiving space to be discharged under the force of said fluent filler material as it charges into said filler material receiving space;   wherein said valve and said fluid passageway cooperate to inhibit the formations of air bubbles in said fluent filler material and to inhibit a back-flow of said fluent filler material from said envelope as said envelope transforms from its relaxed state to its inflated state; and   wherein said zone of weakness helps to facilitate the separation of said valve from said envelope when said envelope has reached its inflated state to form an occlusion member for occluding a nucleus pulposus aperture dimensioned to permit the passage of said envelope in its relaxed state into said nucleus pulposus cavity.   
     
     
         2 . A prosthesis for a tissue site, comprising:
 an envelope defining member for facilitating replacement of a nucleus pulposus;   a silicone-rubber material for inflating said envelope defining member so it self anchors to a set of irregularly shaped walls disposed within a nucleus pulposus cavity of an intervertebral disc;   a sleeve bonded to said envelope defining member by an annular adhesive layer, said sleeve having a zone of weakness to facilitate its separation from said envelope defining member to form an occlusion member for closing an annulus fibrosis aperture providing said envelope defining member access to said nucleus pulposus cavity prior to being inflated;   a bead defining air passageway for facilitating fluid discharge from said envelope defining member as it transforms from a relaxed state within said nucleus pulposus cavity to an inflated state within said nucleus pulposus cavity;   wherein said occlusion member is constructed for separation to occlude said annulus fibrosis aperture after said envelope defining member is in said inflated state;   wherein said sleeve defines a valve, said valve and said bead defining air passageway cooperating to inhibit the formation of air bubbles in said silicone-rubber material as it expands to transform said envelope defining member from its relaxed state to its inflated state; and   wherein said valve and said bead defining air passageway further cooperate to inhibit the back-flow of said silicone-rubber material from said envelope defining member as said envelope defining member is transforming from its relaxed state to its inflated state.   
     
     
         3 . A prosthesis for a tissue site, comprising:
 deformable envelope means for facilitating replacement of a nucleus pulposus;   filler material means for inflating said deformable envelope means so it self anchors to a set of irregularly shaped walls disposed within a nucleus pulposus cavity of an interverterbral disc;   occluding means for closing an annulus fibrosis aperture providing deformable envelope means access to said nucleus pulposus cavity prior to being inflated by said filler material means;   venting means for facilitating fluid discharge from said deformable envelope means as it transforms from a relaxed state within said nucleus pulposus cavity to an inflated state within said nucleus pulposus cavity;   wherein said occluding means is constructed for separation to form a blocking occlusion in said annulus fibrosis aperture after said deformable envelope means is in said inflated state; and   wherein said occluding means and said venting means cooperate to inhibit the formation of air bubbles in said filler material means as said filler material means inflates said deformable envelope means and to inhibit the discharge of filler material means from said deformable envelope means as it is transformed from said relaxed state to said inflated state.   
     
     
         4 . The prosthesis according to  claim 3  wherein said occluding means is bonded to said deformable envelope means;
 wherein said venting means includes a bead for defining an air passageway to permit air trapped within an interior space of said deformable envelope means to escape; and 
 wherein said deformable envelope means is sized in its relaxed state to pass through said annulus fibrosis aperture and into said nucleus pulposus cavity. 
 
     
     
         5 . The prosthesis according to  claim 4 , wherein said deformable envelope means is further sized to expand up to 100 times its relaxed state to facilitate said deformable envelope means conforming closely to the shape and size of said cavity when it reaches said inflated state when disposed in said cavity. 
     
     
         6 . The prosthesis according to  claim 5 , wherein said deformable envelope means includes:
 a valve defining sleeve for defining a one way passageway for said filler material means as it is charged in a fluent state into said interior space of said deformable envelope means; and   an envelope defining member, wherein said envelope defining member is bonded to said valve defining sleeve by an annular adhesive layer.   
     
     
         7 . The prosthesis for a tissue site according to  claim 6 , wherein said valve defining sleeve permits the passage of air from the interior receiving space of said envelope defining member but inhibits the passage of said filler material means from the interior receiving space of said envelope defining member when said filler material means is in a fluent state as said envelope defining member transforms from said relaxed state to said inflated state. 
     
     
         8 . The prosthesis according to  claim 7  wherein said envelope defining member is composed of a knitted polyethylene terephthalate material so that when said filler material means is charged in its fluent state into said envelope, said filler material means fills foramens and interstices in said envelope to form an integrated structure with said envelope defining member when said filler material means cures;
 wherein said integrated structure resists relative movement between said filler material means and said envelope defining member when said filler material means is cured. 
 
     
     
         9 . The prosthesis according to  claim 8 , wherein said polyethylene terephthalate material is coated with silicon to facilitate integration between said filler material means and the coating of silicon. 
     
     
         10 . The prosthesis according to  claim 9 , wherein said inflated state is a substantially inflated state. 
     
     
         11 . The prosthesis according to  claim 10 , wherein said substantially inflated state is a fully inflated state; and
 wherein said relaxed state is a substantially relaxed state; and   wherein said substantially relaxed state is a collapsed state.   
     
     
         12 . The prosthesis according to  claim 9 , wherein said envelope defining member is composed of a material that has been post cured for a period of about 1 hour to about 4 hours at a temperature of between about 150 degrees centigrade and about 180 degrees centigrade to further facilitate its replacement of a nucleus pulposus. 
     
     
         13 . The prosthesis according to  claim 7 , wherein said filler material means is composed of two separate parts, the two separate parts when combined in a ratio of 1:1 and cured having a Shore hardness of between about  20 A to about  40 A, and more preferably between about  25 A and about  30 A, and most preferably at about  28 A. 
     
     
         14 . The prosthesis according to  claim 13 , wherein said filler material means when cured has a tensile strength in the range of about 7000 kPa to about 9500 kPa and more preferably between about 8000 kPa to about 9000 kPa, and most preferably at about 8500 kPa. 
     
     
         15 . The prosthesis according to  claim 14 , wherein said filler material means when cured has an elongation in the range of about 550% to about 700% and more preferably between about 600% and about 650%, and most preferably at about 640%. 
     
     
         16 . The prosthesis according to  claim 15 , wherein said filler material means when cured has a tear strength in the range of about 1000 kg/m to about 2000 kg/m and more preferably between about 1240 kg/m and about 1750 kg/m, and most preferably at about 1500 kg/m. 
     
     
         17 . The prosthesis according to  claim 6 , wherein said envelope defining member includes a neck portion;
 wherein said neck portion defines a zone of weakness; and   wherein said zone of weakness helps to facilitate the separation of said sleeve defining valve from said envelope defining member to form a separated occlusion in said annulus fibrosis aperture.   
     
     
         18 . The prosthesis according to  claim 17 , wherein said zone of weakness is a circumferential groove. 
     
     
         19 . The prosthesis according to  claim 18 , wherein said filler material means is an elastomeric material capable of absorbing shock and withstanding compressive, tensile, bending and torsional forces. 
     
     
         20 . The prosthesis according to  claim 19 , wherein said filler material means is a silicone-rubber material.