Methods and apparatuses for promoting fusion of vertebrae

Abstract

Methods and apparatuses for promoting fusion of vertebrae are provided. The apparatuses comprise interconnecting plates that fixate vertebrae to each other and provide for a predetermined amount of subsidence where the fusion occurs. Allowing for this predetermined amount of subsidence increases bone to bone contact at the graft, which promotes fusion without having excessive settling of the two vertebrae onto the graft. The predetermined amount of subsidence is achieved by the placement of a plate spacer between each of two interconnecting plates when the plates are attached to the vertebrae. The plate spacer has a height equal to the maximum amount of subsidence desired. After affixing the plates to the vertebrae, the plate spacer is removed, leaving a space between the plates, which allows the vertebrae to subside by a distance equal to the height of the plate spacer.

1 - 95 . (canceled)  
   
   
       96 . A method for promoting fusion of a first vertebra with a second vertebra in a spinal column, the method comprising, 
 providing an apparatus, the apparatus comprising    a first plate mountable to the first vertebra comprising at least two edges parallel to the long axis of the vertebrae, and    a second plate mountable to the second vertebra comprising at least two edges parallel to the long axis of the vertebrae,    wherein the first plate comprises integral means for slidably interconnecting with the second plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column, said means preventing rotational movement of the first vertebra relative to the second vertebra,    and wherein the plates can overlap only at the integral means for slidably interconnecting at said edges of each plate when the plates are slidably interconnected.    
   
   
       97 . The method of  claim 96 , wherein the first and second vertebrae are cervical vertebrae.  
   
   
       98 . The method of  claim 96 , wherein the first vertebra is adjacent to the second vertebra in the spinal column.  
   
   
       99 . The method of  claim 96 , wherein the first plate and the second plate each further comprise holes passing through the plate, and fastening means capable of passing through the holes for attaching the plate to the vertebra.  
   
   
       100 . The method of  claim 96 , wherein the apparatus further comprises a removable plate spacer mounted between the first plate and the second plate, said plate spacer comprising a height.  
   
   
       101 . The method of  claim 100 , wherein the plate spacer further comprises a holder and the height of the plate spacer is between about 1 mm and 5 mm.  
   
   
       102 . The method of  claim 96 , wherein the apparatus further comprises means for limiting axial extension of the first plate with respect to the second plate.  
   
   
       103 . The method of  claim 96 , wherein 
 the first plate has a first base mountable to the first vertebra, the first plate also having a tongue protruding from the first base with an end distal to the first base and two sides perpendicular to the end, and    the second plate has a second base, the second base having two sides and a top, wherein the second base is capable of attachment to the second vertebra, the second plate having a groove formed by a top of the second base and inner edges of the two sides of the second base,    wherein the tongue of the first plate and the groove of the second plate slidably interconnect when attached to the first and second vertebrae, the interconnection occurring at the two sides of the tongue of the first plate and the inner edges of the two sides of the second plate, and    wherein the end of the tongue and the top of the second base are capable of touching, preventing compression of the first vertebra with the second vertebra.    
   
   
       104 . The method of  claim 103 , wherein the apparatus further comprises a removable plate spacer suitable for placing between the first plate and the second plate, said plate spacer comprising a height, wherein the plate spacer fits between the end of the tongue and the top of the second base.  
   
   
       105 . The method of  claim 103 , wherein the apparatus further comprises means for limiting axial extension of the first plate with respect to the second plate.  
   
   
       106 . The method of  claim 105 , wherein the means for limiting axial extension is provided with at least one of the two sides of the tongue of the first plate comprising an indentation and at least one of the inner edges of the two sides of the second base comprising a tab or a setscrew, the tab or setscrew engagable into the indentation when the tongue of the first plate and the groove of the second plate slidably interconnect.  
   
   
       107 . A method for promoting fusion of a first vertebra with a second vertebra in a spinal column, the method comprising 
 providing an apparatus, the apparatus comprising 
 means for attaching the apparatus to the first vertebra at a first member;  
 means for attaching the apparatus to the second vertebra at a second member;  
 means for preventing rotational movement of the first vertebra relative to the second vertebra; and  
 a plate spacer comprising a height, the plate spacer capable of insertion into the apparatus between the first member and the second member, wherein the plate spacer can be removed from the apparatus after the apparatus is attached to both the first vertebra and the second vertebra;  
   attaching the apparatus to the first vertebra at the first member;    partially engaging the means for preventing rotational displacement of the first vertebra from the second vertebra;    placing the plate spacer between the first member and the second member;    substantially fully engaging the means for preventing rotational displacement such that the first member and the second member each abut the plate spacer;    attaching the apparatus to the second vertebra at the second member; and    removing the plate spacer from between the first member and the second member.    
   
   
       108 . The method of  claim 107 , wherein the means for preventing rotational displacement is engaged, the plate spacer is placed between the first member and the second member, and the means for preventing rotational displacement is substantially fully engaged before the apparatus is attached to the first vertebra and the second vertebra.  
   
   
       109 . The method of  claim 108 , wherein the apparatus further comprises means for limiting axial extension of the first plate with respect to the second plate.  
   
   
       110 . The method of  claim 107 , wherein the apparatus comprises 
 a first plate mountable to the first vertebra comprising at least two edges parallel to the long axis of the vertebrae, and    a second plate mountable to the second vertebra comprising at least two edges parallel to the long axis of the vertebrae,    wherein the first plate comprises integral means for slidably interconnecting with the second plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column, said means preventing rotational movement of the first vertebra relative to the second vertebra,    and wherein the plates can overlap only at the integral means for slidably interconnecting at said edges of each plate when the plates are slidably interconnected.    
   
   
       111 . A method for promoting fusion of a first vertebra, a second vertebra and a third vertebra in a spinal column at grafts between (a) the first vertebra and the second vertebra and (b) the second vertebra and the third vertebra, the method comprising 
 providing an apparatus, the apparatus comprising    a first plate mountable to the first vertebra comprising at least two edges parallel to the long axis of the vertebrae,    a second plate mountable to the second vertebra comprising at least two edges parallel to the long axis of the vertebrae, and    a third plate mountable to the third vertebra comprising at least two edges parallel to the long axis of the vertebrae,    wherein the first plate comprises integral means for slidably interconnecting with the second plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column, said means preventing rotational movement of the first vertebra relative to the second vertebra,    wherein the second plate comprises integral means for slidably interconnecting with the first plate and the third plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column, said means preventing rotational movement of the first vertebra relative to the second vertebra and the second vertebra relative to the third vertebra,    wherein the third plate comprises integral means for slidably interconnecting with the second plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column, said means preventing rotational movement of the second vertebra relative to the third vertebra,    and wherein the plates can overlap only at the integral means for slidably interconnecting at said edges of each plate when the plates are slidably interconnected,    mounting the first plate to the first vertebra, the second plate to the second vertebra, and the third plate to the third vertebra, and    engaging the means for slidably interconnecting the first plate with the second plate and the second plate with the third plate.    
   
   
       112 . The method of  claim 111 , wherein the apparatus further comprises 
 a first plate spacer comprising a height, wherein the first plate spacer is inserted between the first plate and the second plate when the first plate and the second plate are mounted, then removed after the first plate and the second plate are mounted, and    a second plate spacer comprising a height, wherein the second plate spacer is inserted between the second plate and the third plate when the second plate and the third plate are mounted, then removed after the second plate and the third plate are mounted.    
   
   
       113 . The method of  claim 111 , wherein the apparatus further comprises means for limiting axial extension of the first plate with respect to the second plate and the second plate with respect to the third plate.  
   
   
       114 . A method for promoting fusion of n adjacent vertebrae in a spinal column at grafts between each of the n vertebrae, the method comprising 
 providing an apparatus, the apparatus comprising    n plates, each plate mountable to a different vertebra, each plate comprising at least two edges parallel to the long axis of the vertebrae,    wherein each plate comprises integral means for slidably interconnecting with the adjacent plate at said edges of each plate that are parallel to the long axis of the vertebrae, said sliding occurring parallel to the long axis of the spinal column,    and wherein the plates can overlap only at the integral means for slidably interconnecting at said edges of each plate when the plates are slidably interconnected,    mounting each plate to that plate's respective vertebra, and    engaging each of the means for slidably interconnecting the with the adjacent plate.    
   
   
       115 . The method of  claim 114 , wherein the apparatus further comprises 
 n−1 plate spacers comprising a height, wherein each plate spacer is inserted between two adjacent plates, where one and only one plate spacer is inserted between each two adjacent plates, and wherein each plate spacer is removed after that plate spacer's two adjacent plates are mounted.    
   
   
       116 . The method of  claim 114 , wherein the apparatus further comprises a means for limiting axial extension of each plate with respect to its adjacent plate.