Load distribution crown

Abstract

An apparatus for distributing the load caused by the insertion of a fastening device into bony tissue is disclosed. In one embodiment, the apparatus comprises a crown having a plurality of protrusions. The protrusions may have any desired physical properties, and function to obtain purchase in the bony tissue. Preferably, the crown includes an opening that is selectively engageable with a spherical head of the fastening device. The opening preferably comprises a spherical curvature that allows the surfaces of the spherical head and the opening to maintain flush contact, even when the fastening device is inserted into the bony tissue at a non-orthogonal angle. When the fastening device is inserted into the bony tissue, the crown distributes the load over a wider section of the bone, allowing the bone to maintain its structural integrity.

What is claimed is: 
     
         1 . A surgical method comprising:
 providing a fastener having a head member and a shaft member;   providing a crown, wherein the crown comprises an upper surface, a bottom surface and an opening formed between the upper and bottom surfaces, wherein the crown further comprises a first notch in the crown; and   inserting the fastener through the opening of the crown and into a bone member, wherein the head member of the fastener applies a pressure to the surface of the crown to secure the crown against the bone member.   
     
     
         2 . The method of  claim 1 , wherein the crown further comprises a second notch. 
     
     
         3 . The method of  claim 2 , wherein the first notch is disposed on the upper surface of the crown. 
     
     
         4 . The method of  claim 3 , wherein the second notch is disposed on the bottom surface of the crown. 
     
     
         5 . The method of  claim 4 , wherein the second notch is a diagonal slit extending from the opening of the crown to the outer perimeter of the crown. 
     
     
         6 . The method of  claim 1 , wherein the first notch is a diagonal slit diagonal slit disposed on the upper surface of the crown and extending from the opening of the crown to the outer perimeter of the crown. 
     
     
         7 . The method of  claim 1 , wherein the notch is configured to allow sufficient deformation of the crown to match a contour of the bone member. 
     
     
         8 . The method of  claim 1 , wherein the bottom surface of the crown includes a plurality of protrusions. 
     
     
         9 . The method of  claim 8 , wherein the plurality of protrusions include protrusion of varying length. 
     
     
         10 . The method of  claim 9 , wherein the plurality of protrusions are configured to achieve sufficient purchase in the bone member while maintaining structural integrity of the bone member. 
     
     
         11 . An apparatus for distributing a load in a spinal fixation system, comprising:
 a fastener having a head member and a shaft member; and   a crown, wherein the crown comprises an upper surface, a bottom surface and an opening formed between the upper and bottom surfaces, wherein the crown further comprises a first notch in the crown,   wherein the fastener is configured to be inserted through the opening of the crown and into a bone member, wherein the head member of the fastener applies a pressure to the surface of the crown to secure the crown against the bone member.   
     
     
         12 . The apparatus of  claim 11 , wherein the crown further comprises a second notch. 
     
     
         13 . The apparatus of  claim 12 , wherein the first notch is disposed on the upper surface of the crown. 
     
     
         14 . The apparatus of  claim 13 , wherein the second notch is disposed on the bottom surface of the crown. 
     
     
         15 . The apparatus of  claim 14 , wherein the second notch is a diagonal slit extending from the opening of the crown to the outer perimeter of the crown. 
     
     
         16 . The apparatus of  claim 11 , wherein the first notch is a diagonal slit diagonal slit disposed on the upper surface of the crown and extending from the opening of the crown to the outer perimeter of the crown. 
     
     
         17 . The apparatus of  claim 11 , wherein the notch is configured to allow sufficient deformation of the crown to match a contour of the bone member. 
     
     
         18 . The apparatus of  claim 11 , wherein the bottom surface of the crown includes a plurality of protrusions. 
     
     
         19 . The apparatus of  claim 18 , wherein the plurality of protrusions include protrusion of varying length. 
     
     
         20 . The apparatus of  claim 19 , wherein the plurality of protrusions are configured to achieve sufficient purchase in the bone member while maintaining structural integrity of the bone member.