Polyaxial pedicle screw having a rotating locking element

#The invention relates generally to screws and coupling element assemblies for use with orthopedic fixation systems. More particularly, the invention relates to a screw and coupling element assembly, for use with an orthopedic rod implantation apparatus, that includes a locking element that simultaneously locks a head of the screw within a seat of the coupling element so that a shaft of the screw is fixed at an angle relative to the coupling element and a rod, of the orthopedic rod implantation apparatus, disposed within a rod-receiving channel of the locking element is fixed relative to the coupling element.

#The bones and connective tissue of an adult human spinal column consists of more than twenty discrete bones coupled sequentially to one another by a tri-joint complex which consist of an anterior disc and the two posterior facet joints, the anterior discs of adjacent bones being cushioned by cartilage spacers referred to as intervertebral discs. These more than twenty bones are anatomically categorized as being members of one of four classifications: cervical, thoracic, lumbar, or sacral. The cervical portion of the spine, which comprises the top of the spine, up to the base of the skull, includes the first seven vertebrae. The intermediate twelve bones are the thoracic vertebrae, and connect to the lower spine comprising the five lumbar vertebrae. The base of the spine is the sacral bones (including the coccyx). The component bones of the cervical spine are generally smaller than those of the thoracic and lumbar spine.

#Referring now to FIGS. 1, 2, and 3, top, side, and posterior views of a vertebral body, a pair of adjacent vertebral bodies, and a sequence of vertebral bodies are shown, respectively. The spinal cord is housed in the central canal 10, protected from the posterior side by a shell of bone called the lamina 12. The lamina 12 includes a rearwardly and downwardly extending portion called the spinous process 16, and laterally extending structures which are referred to as the transverse processes 14. The anterior portion of the spine comprises a set of generally cylindrically shaped bones which are stacked one on top of the other. These portions of the vertebrae are referred to as the vertebral bodies 20, and are each separated from the other by the intervertebral discs 22. The pedicles 24 comprise bone bridges which couple the anterior vertebral body 20 to the corresponding lamina 12.

#FIG. 1 is a top view of a human vertebra.

#FIG. 2 is a side view of a pair of adjacent vertebrae of the type shown in FIG. 1.

#FIG. 3 is a posterior view of a sequence of vertebrae of the type shown in FIGS. 1 and 2.

#While the invention will be described more fully hereinafter with reference to the accompanying drawings, in which particular embodiments and methods of implantation are shown, it is to be understood at the outset that persons skilled in the art may modify the invention herein described while achieving the functions and results of this invention. Accordingly, the descriptions which follow are to be understood as illustrative and exemplary of specific structures, aspects and features within the broad scope of the invention and not as limiting of such broad scope.

#In an embodiment, the invention provides a screw and coupling element assembly for use with an orthopedic rod implantation apparatus. The assembly includes a securing element such as, for example, a screw, that has a head and a shaft that extends from the head. Other securing elements can include, for example, lamina hooks and sacral blocks.

#Accordingly, FIG. 4a illustrates a side view of a screw 120 suitable for use in the invention. The screw 120 includes a head 122 and a shaft 126 that extends from the head 122. The shaft 126 is shown as having a tapered shape with a high pitch thread 128. It shall be understood that a variety of shaft designs are interchangeable with the screw of the invention. The specific choice of shaft features, such as thread pitch, shaft diameter to thread diameter ratio, and overall shaft shape, should be made be the physician with respect to the conditions of the individual patient's bone, however, the invention is compatible with a wide variety of shaft designs.