Facet joint prosthesis measurement and implant tools

Abstract

The present invention provides tools and methods designed to aid in the placement of facet joint prostheses at virtually all spinal levels. One aspect of the present invention is a measurement tool for installing a cephalad facet joint prosthesis including a fixation measurement element and a support arm element. This measurement tool assists in the selection and/or configuration of a cephalad facet joint prosthesis for implantation in a patient. Another aspect is a measurement tool for installing a caudal facet joint prosthesis including a stem element and a trial caudal bearing surface element. This measurement tool assists in the selection and/or configuration of a caudal facet joint prosthesis for implantation in a patient. Yet another aspect is a measurement tool holder including a measurement surface connected to a holder element. This tool holder assists in determining the measurements obtained with the caudal facet joint prosthesis measurement tool.

1 . A system for conducting surgery on a spine of a patient, the system comprising: 
 a frame comprising: 
 a first anchoring feature attachable to a first bone portion of the patient;  
 a second anchoring feature attachable to a second bone portion of the patient, wherein the first and second bone portions are spaced apart from each other;  
   a first registration feature shaped to guide a surgical instrument, wherein the surgical instrument comprises a measurement tool configured to measure a displacement between the first registration feature and a bony landmark of the spine; and    a bridging structure configured to couple the first and second anchoring features and the first registration feature together such that the second anchoring feature is positionable at any of a variety of positions with respect to the first anchoring feature,    wherein the first and second anchoring features are configured to be attached to pedicles of the spine.    
     
     
         2 . A system for conducting surgery on a spine of a patient, the system comprising: 
 a frame comprising: 
 a first anchoring feature attachable to a first bone portion of the patient;  
 a second anchoring feature attachable to a second bone portion of the patient, wherein the first and second bone portions are spaced apart from each other;  
   a first registration feature shaped to guide at least one surgical instrument, the first registration feature comprising a guide post that is receivable by a corresponding bore of the surgical instrument, the guide post having a non-circular cross section selected to substantially prevent rotation of the surgical instrument about an axis of the guide post; and    a bridging structure configured to couple the first and second anchoring features and the first registration feature together such that the second anchoring feature is positionable at any of a variety of positions with respect to the first anchoring feature,    wherein the first and second anchoring features are configured to be attached to pedicles of the spine.    
     
     
         3 . A method for measuring a bony landmark on a spine of a patient, the method comprising: 
 attaching a frame to a first bone portion and a second bone portion of the spine, wherein the first and second bone portions are spaced apart from each other;    registering a measurement tool with respect to the frame; and    guiding the registered measurement tool with the frame to measure at least one of a position of the bony landmark, and an orientation of the bony landmark.    
     
     
         4 . The method of  claim 3 , wherein the frame comprises a first registration feature, wherein registering the measurement tool with respect to the frame comprises coupling the measurement tool to the first registration feature.  
     
     
         5 . The method of  claim 4 , wherein the frame further comprises a second registration feature, wherein attaching the frame to the first and second bone portions comprises: 
 positioning the first and second registration features on opposite sides of a sagittal plane of the patient to guide instrumentation to enable performance of two distinct measurement functions substantially symmetrically across the sagittal plane.    
     
     
         6 . The method of  claim 3 , further comprising replacing at least a portion of a facet of a vertebra of a spine of the patient with at least one prosthesis.  
     
     
         7 . A method for measuring a bony landmark on a spine of a patient through the use of a system comprising a frame having an external anchoring feature, and a stationary external support comprising a fixed end and a grip, the method comprising: attaching the fixed end to a stationary structure; positioning the frame at a desired location with respect to the spine; attaching the grip to the external anchoring feature to restrict motion of the frame; registering a measurement tool with respect to the frame; and guiding the registered measurement tool with the frame to measure at least one of a position of the bony landmark, and an orientation of the bony landmark.  
     
     
         8 . The method of  claim 7 , wherein the frame comprises a first registration feature, wherein registering the measurement tool with respect to the frame comprises coupling the measurement tool to the first registration feature.  
     
     
         9 . The method of  claim 8 , wherein the frame further comprises a bridging structure that movably couples the first registration feature to the external anchoring feature, the method further comprising: manipulating the bridging structure to move the first registration feature with respect to the external anchoring feature; and locking the bridging structure to restrict further motion of the first registration feature with respect to the external anchoring feature.  
     
     
         10 . The method of  claim 7 , further comprising replacing at least a portion of a facet of a vertebra of a spine of the patient with at least one prosthesis.