Method of making a prosthetic intervertebral disc joint assembly

Abstract

A prosthetic intervertebral disc joint assembly for replacing at least a portion of an intervertebral disc between first and second adjacent vertebrae comprising: a first component 20, 120 for engaging a first vertebra, the first component having an intervertebral portion 20a, 120a insertable between adjacent vertebrae and having a bone-engaging side for engaging an endplate of the first vertebra and an inner side opposite the bone-engaging side, the inner side of the intervertebral portion 20a, 120a having an articulating surface 22, 122 comprising a generally convex surface; a second component 30, 130 for engaging a second vertebra, the second component having an intervertebral portion 30a, 130a insertable between adjacent vertebrae and having a bone-engaging side for engaging an endplate of the second vertebra and an inner side opposite the bone-engaging side, the inner side of the intervertebral portion 30a, 130a having an articulating surface 32, 132 comprising a generally concave surface; wherein the convex articulating surface 22, 122 of the first component is sized and shaped to pivot in the concave articulating surface 32, 132 of the second component, and wherein the first component 20, 120 further comprises a fixation portion 20b, 120b for securing the first component to the anterior side of the first vertebra, said fixation portion 20b, 120b extending from the trailing end of the intervertebral portion 20a, 120a of the first component and wherein the second component 30, 130 further comprises a fixation portion 30b, 130b for securing the second component to the anterior side of the second vertebra, said fixation portion 30b, 130b extending from the trailing end of the intervertebral portion 30a, 130a of the second component.

1 .- 57 . (canceled) 
     
     
         58 . A method of making a prosthetic intervertebral disc joint assembly for replacing at least a portion of an intervertebral disc between first and second adjacent vertebrae at a site of installation in a subject, each vertebra having an anterior side and a posterior side, the assembly having a leading end which leads as the assembly is inserted into the intervertebral space and a trailing end opposite the leading end, and an intervertebral plane passing therebetween which aligns with the intervertebral plane between the adjacent vertebrae when installed, the method comprising:
 providing a first component for engaging a first vertebra, the first component having an intervertebral portion insertable between adjacent vertebrae and having a bone-engaging side for engaging an endplate of the first vertebra and an inner side opposite the bone-engaging side, the intervertebral portion of the first component further having a leading end and a trailing end, the inner side of the intervertebral portion of the first component having an articulating surface comprising a generally convex surface;   providing a second component for engaging a second vertebra, the second component having an intervertebral portion insertable between adjacent vertebrae and having a bone-engaging side for engaging an endplate of the second vertebra and an inner side opposite the bone-engaging side, the intervertebral portion of the second component further having a leading end and a trailing end, the inner side of the intervertebral portion of the second component having an articulating surface comprising a generally concave surface;   wherein the first component further comprises a fixation portion for securing the first component to the anterior side of the first vertebra, said fixation portion extending from the trailing end of the intervertebral portion of the first component and wherein the second component further comprises a fixation portion for securing the second component to the anterior side of the second vertebra, said fixation portion extending from the trailing end of the intervertebral portion of the second component, and   providing the first and second components each with a bearing insert and a supporting body, each bearing insert having the component's articulating surface thereon and assembling each bearing insert in a recess in the corresponding supporting body, and   shaping the generally convex articulating surface of the first component such that it is spherically curved, and shaping the generally concave articulating surface of the second component such that it is correspondingly spherically curved such that the articulating surface of the first component can pivot in the concave articulating surface of the second component when assembled, and   predetermining the size radius of curvature of the articulating surface of the first component and the articulating surface of the second component to match that of the subject's natural radius of curvature at the intervertebral disc joint in the sagittal plane,   thereby providing a common center of rotation, at least in the sagittal plane, for flexion/extension for the articulating surfaces of the prosthetic intervertebral disc joint assembly and for each of the articulating surfaces of the two facet joints between said first and second vertebrae, to ensure that contact is maintained between the bones at the facet joints either side of the intervertebral disc joint during the full range of flexion and extension of the joint.   
     
     
         59 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the fixation portion of the first component has a bone-engaging side presenting towards the first vertebra when implanted and an outer side opposite the bone-engaging side, the method further comprising shaping and sizing at least part of the outer side of the fixation portion of the first component being substantially aligned with or substantially within a notional arc the perimeter of which aligns with the convex articulating surface of the first component in the sagittal plane, such that said at least part of the fixation portion of the first component does not impinge against the second component during flexion of the intervertebral disc joint assembly in use. 
     
     
         60 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein each fixation portion is provided with at least one through hole for receiving a bone screw. 
     
     
         61 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein said at least one through hole is at least partially internally threaded for receiving a bone screw therein with a correspondingly externally threaded head. 
     
     
         62 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein each fixation portion has first and second through holes each through hole having a longitudinal axis, the longitudinal axis of each through hole being angled at a predetermined angle relative to the fixation portion such that first and second bone screws will diverge from one another when installed in the first and second through holes. 
     
     
         63 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the fixation portion of the first component is angled relative to an intervertebral plane passing through the intervertebral portion of the first component and the fixation portion of the second component is angled relative to an intervertebral plane passing through the intervertebral portion of the second component. 
     
     
         64 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the radius of curvature of the articulating surfaces of the first component is sized to be between about 10 and 25 mm. 
     
     
         65 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the first component is provided with a bearing insert made from cobalt chrome. 
     
     
         66 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the supporting body of the first component is made from titanium or titanium alloy. 
     
     
         67 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the second component is provided with a bearing insert made from a polymeric material. 
     
     
         68 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the supporting body of the second component is made from titanium or titanium alloy. 
     
     
         69 . A method of making prosthetic intervertebral disc joint assembly according to claim  1 , wherein the method comprises making a set of implant components for assembly into a prosthetic intervertebral disc joint assembly, wherein the set comprises a plurality of first components, the plurality of first components each having an articulating surface with a different radius of curvature, and making a plurality of second components having articulating surfaces with a radii of curvature matching those of the corresponding first components, such that the first and second components with the radius of curvature closest to a subject's natural radius of curvature can be selected for implantation.