Bone fixation assembly

#It is often necessary due to various spinal disorders to surgically correct and stabilize spinal curvatures, or to facilitate spinal fusion. Numerous systems for treating spinal disorders have been developed.

#One method involves a bone fixation system including a pair of elongated members, typically spinal rods, longitudinally placed on the posterior spine on either or both sides of the spinous processes of the vertebral column. Each rod is attached to various vertebrae along the length of the spine by way of bone fixation or bone anchor assemblies, e.g. pedicle screws. The body of the pedicle screw often has a rod-receiving channel and receives a locking cap to secure the spinal rod to the pedicle screw.

#To facilitate insertion of the spinal rod into the rod-receiving channels of the pedicle screws, pedicle screws have been developed wherein the body is separate from and pivotable with respect to the bone anchor (commonly known as polyaxial pedicle screws).

#The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. The preferred embodiments of a bone anchor system including a bone anchor assembly are shown in the drawings for the purposes of illustration. It should be understood, however, that the application is not limited to the precise arrangements, structures, features, embodiments, instrumentalities, and methods shown and described, and the arrangements, structures, features, embodiments, instrumentalities, and methods shown and described may be used singularly or in combination with other arrangements, structures, features, embodiments, instrumentalities, and methods. In the drawings:

#FIG. 1 illustrates a side perspective view of a first embodiment of a bone anchor assembly configured with a side-loading, rod-receiving channel, in accordance with the present invention;

#FIG. 1A illustrates a side cross-sectional view of the anchor assembly of FIG. 1;

#Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower”, “upper”, “below”, “above”, “top”, and “bottom” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center of the bone anchor system and/or assembly, the described instruments and designated parts thereof. The words, “anterior”, “posterior”, “superior”, “inferior”, “medial”, and “lateral” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

#Certain exemplary embodiments of the invention will now be described with reference to the drawings. In general, such embodiments relate to a preferred bone anchor system including preferred bone anchor assemblies and related instruments by way of non-limiting example for use in spinal fixation which generally includes a rod-receiving channel configured and arranged to receive and secure the position of a spinal rod. Preferably the system may include (1) bone anchor assemblies that have a channel for receiving the spinal rod from the side, referred to as a side-loading bone anchor or side-loading bone anchor assembly, and/or (2) bone anchor assemblies that have a channel for receiving the spinal rod from the top, referred to as a top-loading bone anchor or top-loading bone anchor assembly. Preferably, the top-loading bone anchor assemblies can be used with side-loading bone anchor assemblies in the same system, and for the same spinal rod. The bone anchor assemblies may also include bodies having integral spinal rod elements or the bone anchor assemblies of the present invention may be used with bone anchor assemblies that have integral spinal rod elements.

#Referring to FIGS. 1-3, bone anchor or bone fixation assembly 100 generally includes a bone anchor 10 (shown as a bone screw), a body 20, a bushing 40, and a locking cap 92, which includes a saddle 70. As will be described in greater detail below, the anchor assembly 100 preferably enables in-situ assembly of the bone anchor 10 to the body 20. That is, preferably, the bone anchor assembly 100 is configured so that in use, the bone anchor 10 may be secured to a patient's vertebra 200 prior to being received within the body 20. The bone anchor assembly 100 preferably enables a surgeon to implant the bone anchor 10 without the body 20 and bushing 40 pre-assembled to the bone anchor 10. By enabling the surgeon to implant only the bone anchor 10 without the body 20, the anchor assembly 100 maximizes visibility and access around the anchoring site.