Fully-Adjustable Bone Fixation Device

Abstract

An orthopedic stabilization system of implants that includes a bone attachment means that provides poly-axial fixation of the system to the vertebrae, and a connector means that connects the bone attachment means to the spinal rod in a fashion that allows variable height adjustment of the spinal rod (dorsal in the case of posterior spinal pedicle fixation). The orthopedic stabilization system includes a locking means with a tightenable ball-joint arrangement that locks a post means to the bone attachment means in a desired relative spatial orientation. Several embodiments are disclosed, some using traditional mechanical locking means such as screw fasteners, taper-locking interfaces and collets. Embodiments are described that use the austenitic transformation of shape memory alloy (SMA) material to effect a locking of both the ball-joint arrangement and the connector means.

1 . An orthopedic stabilization system to attach a spinal rod to vertebrae, comprising:
 a bone attachment means, including:   a spherical cup member forming one end of said bone attachment means;   
       and a bone interface member that is integral to said spherical cup member and forms the other end of said bone attachment means, and interfaces to the vertebrae;
 a post means, including: 
 a spherical ball member forming one end of said post means and interfaces with said spherical cup member to form a ball-joint arrangement; and 
 a post member integral to said spherical ball member and forming the other end of said post means, the post member having a post height; a locking means to lock said bone attachment means to said post means in a determined spatial orientation; and a connector means to attach the spinal rod to said post member, the connector means having a connector height less than the post height such that the connector means can be positioned in a plurality of positions along the post height to provide a variable height adjustment between the spinal rod and bone attachment means. 
 
     
     
         2 . The system of  claim 1 , wherein said locking means includes a thin-walled portion to close and lock the ball-joint arrangement. 
     
     
         3 . The system of  claim 2 , wherein said locking means comprises a shape memory alloy (SMA) ring positioned circumferentially around said spherical cup member. 
     
     
         4 . The system of  claim 1 , wherein said spherical cup member includes a plurality of fingers that define a plurality of slots. 
     
     
         5 . The system of  claim 3 , wherein said locking means comprises a SMA ring circumferentially around said spherical cup member. 
     
     
         6 . The system of  claim 1 , wherein said bone attachment means comprises a threaded bone screw. 
     
     
         7 . The system of  claim 1 , wherein said bone attachment means, said locking means, said connector means and said post means comprise metals and polymers. 
     
     
         8 . The system of  claim 1 , wherein said locking means includes the use of ultrasonic welding and adhesives. 
     
     
         9 . An orthopedic stabilization system to attach a spinal rod to vertebrae, comprising:
 a bone attachment means, including:   a spherical cup member forming one end of said bone attachment means; and   a bone interface member that is integral to said spherical cup member and forms the other end of said bone attachment means, and attaches to the vertebrae;   
       wherein, said spherical cup member includes a plurality of fingers that define a plurality of slots;
 a post means, including: 
 a spherical ball member forming one end of said post means and interfaces with said spherical cup member to form a ball-joint arrangement; and 
 a post member forming the other end of said post means; a locking means comprised of a SMA ring positioned circumferentially around said spherical cup member and locks said ball-joint arrangement in a determined spatial orientation; and a connector means. 
 
     
     
         10 . The system of  claim 9 , wherein said connector means includes a rod clamp means comprising a set screw locking mechanism to rigidly connect the spinal rod to said post means. 
     
     
         11 . The system of  claim 9 , wherein said set screw locking mechanism promotes mechanical interdigitation when rigidly connected to the spinal rod. 
     
     
         12 . The system of  claim 9 , wherein said bone attachment means, said rod clamp means and said post means comprise metals and polymers. 
     
     
         13 . An orthopedic stabilization system to attach a spinal rod to vertebrae, comprising:
 a bone attachment means, including:   a spherical cup member forming one end of said bone attachment means; and   a bone interface member that is integral to said spherical cup member and forms the other end of said bone attachment means, and attaches to the vertebrae;   
       wherein, said spherical cup member includes a plurality of fingers that define a plurality of slots;
 a post means, including: 
 a spherical ball member forming one end of said post means and interfaces with said spherical cup member to form a ball-joint arrangement; and 
 a post member forming the other end of said post means; 
 a locking means comprised of a SMA ring positioned circumferentially around said spherical cup member and locks said ball-joint arrangement in a determined spatial orientation; and 
 a rod clamp means, including: 
 a collet locking mechanism to rigidly connect the spinal rod to said post means; and 
 a post nut to tighten said collet locking mechanism, hereby locking the spinal rod and said post member in a desired relative position. 
 
     
     
         14 . The system of  claim 13 , wherein said collet locking mechanism includes a screw thread section to position said post nut on said post member. 
     
     
         15 . The system of  claim 13 , wherein said spherical cup member includes a thin-walled portion. 
     
     
         16 . An orthopedic stabilization system to attach a spinal rod to vertebrae, comprising:
 a bone attachment means, including:   a spherical cup member forming one end of said bone attachment means; and   a bone interface member that is integral to said spherical cup member and forms the other end of said bone attachment means, and attaches to the vertebrae; wherein, said spherical cup member includes a plurality of fingers that define a plurality of slots;   a post means, including:   a spherical ball member forming one end of said post means and interfaces with said spherical cup member to form a ball-joint arrangement; and   a post member forming the other end of said post means;   a locking means comprised of a SMA ring positioned circumferentially around said spherical cup member and locks said ball-joint arrangement in a determined spatial orientation; and   a rod clamp means including a SMA connector to rigidly connect the spinal rod to said post means in a desired relative position.   
     
     
         17 . An orthopedic stabilization system to attach a spine rod to vertebrae, comprising:
 a bone screw having a screw thread on a bone attachment portion and a partially spherical cup on an opposing end portion;   a post member having a ball member on one end and a post extending from the ball member, the post having a post height and the ball member positioned in the partially spherical cup;   a locking member connected to said partially spherical cup, the locking member moveable from an unlocked position allowing movement between the ball member and the partially spherical cup, and a locked position maintaining the ball member in a fixed position within the partially spherical cup; and   a rod connector for attaching the spine rod to the post, the rod connector having a post engaging portion defining an aperture sized to receive the post, the post engaging portion having a height less than the post height such that the post engaging portion can be positioned in a plurality of locations along the post height to vary the distance between the rod and the bone screw.   
     
     
         18 . The system of  claim 17 , wherein the locking member comprises a shape memory alloy and the locking member moves between the unlocked position and the locked position by austenitic transformation due to a change in temperature. 
     
     
         19 . The system of  claim 17 , wherein the locking member is formed of at least one of a metal or a polymer and the locking occurs by use of ultrasonic welding or adhesives to bond the locking member to the ball member. 
     
     
         20 . The system of  claim 17 , wherein the locking member is formed of a deformable material and the transition from the unlocked position to the locked position occurs by material deformation.