Cranial clamp with torque-limiting feature

Abstract

A clamp assembly according to the invention can be fixed through an opening between adjacent members. The clamp assembly includes a base, a cap opposing the base, and a post connecting the cap and the base in a fastening position on the adjacent members. The post includes a torque-limiting feature to prevent over tightening of the cap and base. The clamp assembly may further include an applier interacting with the post to position the cap and base in the fastening position. A method according to the invention includes placing the base and cap on opposing internal and external surfaces of the adjacent members. The post is rotated to bring the base and cap to the fastening position, and a torque-limiting feature prevents over tightening. The method may further include removing a distal portion of the post projecting from the cap and leaving a proximal portion of the post projecting from the cap and which can be deformed to secure the base and cap in the fastening position.

What is claimed is:  
     
         1 . A clamp assembly for repairing a bone defect in a cranium and operable to fix a bone plate relative the surrounding cranium, each of the bone plate and surrounding cranium having a near face and a far face, the clamp assembly comprising: 
 a cap;    a base opposing the cap;    a post having an elongate body rotatably attached to the base and the cap and including a torque-limiting feature, the post engaging the cap and base to fasten the cap and base relative one another.    
     
     
         2 . The clamp assembly of  claim 1 , further comprising an applier operable to rotate the post to position the cap relative to the base in a fastening position.  
     
     
         3 . The clamp assembly of  claim 2 , wherein the applier is removable from the post while leaving the cap and base interconnected.  
     
     
         4 . The clamp assembly of  claim 2 , wherein the applier includes a body having a keyed bore.  
     
     
         5 . The clamp assembly of  claim 4 , wherein the post includes a key for engaging the keyed bore of the applier.  
     
     
         6 . The clamp assembly of  claim 1 , wherein the post includes external threads.  
     
     
         7 . The clamp assembly of  claim 6 , wherein the cap includes an internally threaded collar for mating engagement with the threads of the post.  
     
     
         8 . The clamp assembly of  claim 1 , wherein the post includes external ribs.  
     
     
         9 . The clamp assembly of  claim 8 , wherein the cap includes a collar for ratcheting the cap along the threads on the post.  
     
     
         10 . The clamp assembly of  claim 1 , wherein the cap and base have opposing inner faces that face each other when assembled in use.  
     
     
         11 . The clamp assembly of  claim 10 , wherein the cap includes teeth extending from the inner face to inhibit rotation of the cap relative to the adjacent members.  
     
     
         12 . The clamp assembly of  claim 1 , wherein the torque-limiting feature prevents over tightening of the cap relative to the base.  
     
     
         13 . The clamp assembly of  claim 1 , wherein the post further includes a key disposed at a distal end of the elongate body.  
     
     
         14 . The clamp assembly of  claim 13 , wherein the key is operable to matingly engage the applier.  
     
     
         15 . The clamp assembly of  claim 13 , wherein the torque-limiting feature is disposed at a junction between the elongate body and the key.  
     
     
         16 . The clamp assembly of  claim 1 , wherein at least one of the cap, base and post includes resorbable material.  
     
     
         17 . The clamp assembly of  claim 16 , wherein the cap, base and post include resorbable material.  
     
     
         18 . The clamp assembly of  claim 1 , wherein at least one of the cap, base and post includes non-resorbable, biocompatible material.  
     
     
         19 . The clamp assembly of  claim 18 , wherein the cap, base and post include non-resorbable, biocompatible material.  
     
     
         20 . The clamp assembly of  claim 18 , wherein the non-resorbable, biocompatible material is titanium.  
     
     
         21 . A method of fixing a bone plate in a bony defect, wherein the bone plate has opposing internal and external surfaces that are to be held in position with internal and external surfaces of surrounding bone, and a transverse face of the bone plate is to be fixed in apposition against a transverse face of the surrounding bone along a border of junction between the bone plate and surrounding bone, the method comprising: 
 rotatably connecting an elongated externally threaded post to a base;    extending the post through a cap to engage the threaded post with the cap;    positioning the base and cap on opposing internal and external surfaces of the bone plate, with a portion of each of the base and cap overlapping the border of junction;    rotating the post to position the cap and base in a fastening position; and    limiting the torque applied by the post in the fastening position.    
     
     
         22 . The method of  claim 21 , further comprising removing a distal end of the post projecting from the cap.  
     
     
         23 . The method of  claim 22 , further comprising leaving a proximal portion of the post projecting from the cap.  
     
     
         24 . The method of  claim 23 , further comprising deforming the proximal portion of the post projecting from the cap to secure the base and cap in the fastening positioning.  
     
     
         25 . The method of  claim 21 , further comprising rotating an applier to cause the post to rotate in the base and position the cap and base in a fastening position.  
     
     
         26 . The method of  claim 21 , wherein limiting the torque prevents over tightening of the cap and base.  
     
     
         27 . The method of  claim 21 , wherein limiting the torque includes severing the post.