Spinal prosthesis and facet joint prosthesis

Abstract

A lumbar disc prosthesis is provided including a pair of disc members. The first member of the disc pair has a vertebral disc contact surface and a recessed portion on an opposing surface thereof. The second member of the disc pair has a vertebral disc contact surface and a protruding portion on an opposing surface thereof. The protruding portion of the second member engages with the recessed portion of the first member in use. Each of the first and second disc members are provided with at least three sections; a middle section and two end sections. The recessed and protruding portions are provided in the middle section of the respective disc members and each of the two end sections have a narrowing taper towards the ends of the disc members. The facet joint prosthesis includes a first member for attachment to a first posterior lumbar disc in use and a second member for attachment to a second posterior lumbar disc in use. At least a part of the first member is telescopically mounted in at least a part of the second member in use.

1 . A disc prosthesis, said disc prosthesis including a pair of disc members, a first member of said disc pair having a vertebral end plate contact surface and a recessed portion on an opposing surface thereof, a second member of said disc pair having a vertebral endplate contact surface and a protruding portion on an opposing surface thereof, the protruding portion of the second member engaging with the recessed portion of the first member in use, and wherein the inner or opposing surface of at least the first disc member is provided with at least three sections including a middle section and at least two end sections, the recessed portion being provided in the middle section and the thickness or depth of the middle section being less than the thickness or depth of the at least two end sections.  
   
   
       2 . A disc prosthesis according to  claim 1  wherein the recessed portion is substantially curved in form.  
   
   
       3 . A disc prosthesis according to  claim 1  wherein the end sections are substantially planar in form.  
   
   
       4 . A disc prosthesis according to  claim 1  wherein the inner or opposing surface of the second disc member is provided with at least three sections; a middle section and at least two end sections, the protruding portion being provided in the middle section of the disc member.  
   
   
       5 . A disc prosthesis according to  claim 1  wherein the boundaries of the middle and end sections are provided in the medial-lateral plane.  
   
   
       6 . A disc prosthesis according to  claim 1  wherein the boundaries of the middle and end sections are provided in the anterior-posterior plane.  
   
   
       7 . A disc prosthesis according to  claim 1  wherein the middle and end sections are arranged along substantially the entire length of the disc member.  
   
   
       8 . A disc prosthesis according to  claim 1  wherein the middle and end sections are arranged in a substantially central part of the disc member.  
   
   
       9 . A disc prosthesis according to  claim 1  wherein the vertebral endplate contact surface of the first and/or second members is provided with attachment means.  
   
   
       10 . A disc prosthesis according to  claim 9  wherein the attachment means includes any or any combination of one or more screws, one or more apertures for the location of screws, one or more tapered members, spikes or fins.  
   
   
       11 . A disc prosthesis according to  claim 1  wherein one or both of the end sections of the inner or opposing surfaces of the first and/or second disc members are provided at an acute angle to the horizontal.  
   
   
       12 . A disc prosthesis according to  claim 1  wherein the outer and/or inner surfaces of the second disc member form a narrowing taper towards one or both ends of the disc member.  
   
   
       13 . A disc prosthesis according to  claim 1  wherein one or both ends of the prosthesis has a narrowing taper towards the outer edges thereof.  
   
   
       14 . A disc prosthesis according to  claim 13  wherein the slope of the taper at the posterior end is opposite to the slope of the taper at the anterior end.  
   
   
       15 . A disc prosthesis according to  claim 1  wherein the height of the prosthesis at an anterior end of the disc is greater than the height of the prosthesis at a posterior end of the disc.  
   
   
       16 . A disc prosthesis according to  claim 1  which is provided for anterior insertion.  
   
   
       17 . A disc prosthesis according to  claim 1  which is provided for posterior insertion.  
   
   
       18 . A disc prosthesis according to  claim 16  wherein the protrusion portion of the second member is substantially the same shape and/or dimensions as the recessed portion of the first member.  
   
   
       19 . A disc prosthesis according to  claim 16  wherein the radius of the curvature of the protrusion portion in the medial to lateral plane is greater than the radius of the curvature of the protrusion portion in the anterior to posterior plane.  
   
   
       20 . A disc prosthesis according to  claim 16  wherein the protrusion portion in the medial to lateral plane is asymmetrical to the protrusion portion in the anterior to posterior plane.  
   
   
       21 . A disc prosthesis according to  claim 16  wherein the curvature of the medial part of the recessed portion is symmetrical to the curvature of the lateral part of the recessed portion.  
   
   
       22 . A disc prosthesis according to  claim 16  wherein a radius of the arc of the curvature of the recessed portion in the medial part thereof is substantially equal to the radius of the arc of the curvature of the recessed portion in the lateral part thereof.  
   
   
       23 . A disc prosthesis according to  claim 16  wherein the anterior part of the recessed portion is symmetrical to the posterior part of the recessed portion.  
   
   
       24 . A disc prosthesis according to  claim 16  wherein attachment means are provided adjacent an anterior edge thereof.  
   
   
       25 . A disc prosthesis according to  claim 16  wherein the prosthesis is in the form of a cervical or lumbar prosthesis.  
   
   
       26 . A disc prosthesis according to  claim 17  wherein the prosthesis is in the form of a lumbar or thoracic prosthesis.  
   
   
       27 . A disc prosthesis according to  claim 17  wherein attachment means are provided adjacent a posterior edge thereof.  
   
   
       28 . A disc prosthesis according to  claim 17  wherein two disc pairs are required to form the prosthesis.  
   
   
       29 . A prosthesis according to  claim 28  wherein the two pairs of disc member are mirror images of each other.  
   
   
       30 . A prosthesis according to  claim 28  wherein each pair of disc members is independently inserted into the disc space in the patient and is located on either side of the dural sac.  
   
   
       31 . A prosthesis according to  claim 17  wherein the recessed portion of the first member is substantially curved and the curvature of a medial part of said recessed portion is asymmetrical to the curvature of a lateral part of said recessed portion.  
   
   
       32 . A prosthesis according to  claim 17  wherein a lateral part of said recessed portion corresponds to an arc of a circle which has a radius greater than that of an arc of a circle corresponding to the curvature of a medial part of the recessed portion.  
   
   
       33 . A prosthesis according to  claim 17  wherein an anterior part of the recessed portion is substantially symmetrical to a posterior part of the recessed portion.  
   
   
       34 . A prosthesis according to  claim 17  wherein the recessed and protrusion portions in each disc member pair are asymmetrical.  
   
   
       35 . A prosthesis according to  claim 17  wherein the protrusion portion in a disc member pair makes contact with only a part of the recessed portion of said disc member pair.  
   
   
       36 . A prosthesis according to  claim 17  wherein the protrusion portion is symmetrical in the medial-lateral plane and the anterior-posterior plane but the curvature in the medial to lateral plane may be different to that in the anterior to posterior plane.  
   
   
       37 . A prosthesis according to  claim 17  wherein the protrusion portion is substantially dome shaped.  
   
   
       38 . A prosthesis according to  claim 17  wherein the recessed portion is substantially inverse dome shaped.  
   
   
       39 . A prosthesis according to  claim 17  wherein the attachment means includes one or more tapered members protruding outwardly of the vertebral endplate contact surface, the taper of said member narrowing from a posterior end towards an anterior end of the disc member.  
   
   
       40 . A prosthesis according to  claim 17  wherein the attachment means are provided towards a medial side of the first and/or second disc members.  
   
   
       41 . A prosthesis according to  claim 17  wherein the end sections of the opposing surface of said first disc member are mildly concave in form.  
   
   
       42 . A prosthesis according to  claim 1  wherein the middle section is located substantially centrally of said first and/or second disc members.  
   
   
       43 . A prosthesis according to  claim 17  wherein the middle and end sections each comprise at least one third of a disc member surface.  
   
   
       44 . A prosthesis according to  claim 1  wherein when one of the disc members moves towards an end of the prosthesis in extension or flexion, a gap between the end sections of the disc members increases at an opposite end of the prosthesis.  
   
   
       45 . A prosthesis according to  claim 1  wherein said prosthesis is used in conjunction with a facet joint prosthesis.  
   
   
       46 . A facet joint prosthesis according to  claim 45  wherein a first member is provided for attachment to a first posterior lumbar disc in use and a second member is provided for attachment to a second posterior lumbar disc in use, and wherein at least a part of said first member is telescopically mounted in at least a part of said second member in use.  
   
   
       47 . A facet joint prosthesis according to  claim 45  wherein the first and/or second members are provided with or are associated with securing means for securing the members to a disc in use.  
   
   
       48 . A facet joint prosthesis according to  claim 47  wherein the securing means includes one or more pedicle screws.  
   
   
       49 . A facet joint prosthesis according to  claim 45  wherein the first member includes an elongate arm portion which is movably located in an elongate channel portion on said second member.  
   
   
       50 . A facet joint prosthesis according to  claim 49  wherein the arm portion and said channel portion are curved in form.  
   
   
       51 . A facet joint prosthesis according to  claim 49  wherein each of said arm portion and said channel portion communicate with a plate portion.  
   
   
       52 . A facet joint prosthesis according to  claim 49  wherein a slot is provided longitudinally of said channel portion.  
   
   
       53 . A facet joint prosthesis according to  claim 52  wherein said slot is of such a width to allow approximately 30% of the arm portion to be visible therethrough.  
   
   
       54 . A facet joint prosthesis according to  claim 52  wherein the slot is open ended.  
   
   
       55 . A facet joint prosthesis according to  claim 52  wherein an enclosed slot is provided on said channel portion and a pin provided on the elongate arm portion is slidably located therein.  
   
   
       56 . A facet joint prosthesis according to  claim 49  wherein the arm portion is of slightly smaller dimensions than the interior dimensions of said channel portion, such that a small gap is provided therebetween to allow some movement between said arm portion and said channel portion.  
   
   
       57 . A facet joint prosthesis according to  claim 49  wherein with the arm portion located in the channel portion, the arm portion can undergo limited rotation, side ways movement and sliding movement to allow flexion and extension with respect to said channel portion.  
   
   
       58 . A facet joint prosthesis according to  claim 49  wherein the end of the arm portion engaging in said channel portion has curved end walls and curved side walls, the curvature of said side walls being less than the curvature of said end walls.  
   
   
       59 . A facet joint prosthesis according to  claim 49  wherein the open end of the channel portion in which the arm portion engages has curved end walls and curved side walls, the curvature of said side walls being less than the curvature of said end walls.  
   
   
       60 . A facet joint prosthesis according to  claim 45  wherein the first and/or second members are provided with guide means for guiding or limiting relative movement between said first and second members.  
   
   
       61 . A facet joint prosthesis according to  claim 45  wherein the first and/or second members are provided with locking means for preventing relative movement between said first and second members.  
   
   
       62 . A facet joint prosthesis according to  claim 61  wherein the locking means is in the form of a locking screw.  
   
   
       63 . A facet joint prosthesis according to  claim 61  wherein the locking screw is located through an aperture defined in the second member and engages in one or more recesses provided in the first member.  
   
   
       64 . A facet joint prosthesis according to  claim 45  wherein a sleeve is provided over said prosthesis.  
   
   
       65 . A facet joint prosthesis according to  claim 45  wherein a pair of facet joint prostheses are used for each disc.  
   
   
       66 . A facet joint prosthesis according to  claim 45  wherein a plurality of first members can be attached to a second member and vice versa to form stacking of said prosthesis.  
   
   
       67 . A facet joint prosthesis, said facet joint prosthesis including a first member for attachment to a first posterior disc in use and a second member for attachment to a second posterior disc in use, and wherein at least a part of said first member is telescopically mounted in at least a part of said second member in use.  
   
   
       68 . A method of attachment of a lumbar disc prosthesis in a patient, said lumbar disc prosthesis including a pair of disc members, a first member of said disc pair having a vertebral endplate contact surface and a recessed portion on an opposing surface thereof, a second member of said disc pair having a vertebral endplate contact surface and a protruding portion on an opposing surface thereof, the protruding portion of the second member engaging in the recessed portion of the first member in use, the prosthesis including a further pair of disc members, said further pair of disc members also including first and second members, said method including the steps inserting each pair of disc members via a posterior route.  
   
   
       69 . A method of attachment of a facet joint prosthesis in a patient, said facet joint prosthesis including a first member and a second member, at least a part of said first member is telescopically mounted in at least a part of said second member in use, said method including attaching a part of said first member to one of an upper or lower vertebrae in use posteriorly and attaching a part of said second member to the other of said upper or lower vertebrae in use posteriorly.  
   
   
       70 . A lumbar disc prosthesis, said lumbar disc prosthesis including a pair of disc members, a first member of said disc pair having a vertebral endplate contact surface and a recessed portion on an opposing surface thereof, a second member of said disc pair having a vertebral endplate contact surface and a protruding portion on an opposing surface thereof, the protruding portion of the second member engaging in the recessed portion of the first member in use, and wherein the prosthesis includes a further pair of disc members, said further pair of disc members also including first and second members.