Branch connector for spinal fixation systems

#This invention relates to an implantable spinal fixation system for the surgical treatment of spinal disorders. More specifically, it relates to branch connectors for attaching the spine rods of spinal fixation systems to one another.

#Various types of spinal column disorders are known and include scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal backward curvature of the spine), excess lordosis (abnormal forward curvature of the spine), spondylolisthesis (forward displacement of a lumbar vertebra) and other disorders, such as ruptured or slipped discs, broken or fractured vertebrae and the like. Patients who suffer from such conditions usually experience extreme and debilitating pain. A technique known as spinal fixation uses surgical implants which mechanically immobilize areas of the spine assisting the eventual fusion of the treated vertebrae. Such techniques have been used effectively to treat the above-described conditions and, in most cases, to bring to the patient relief from pain.

#One particular technique for spinal fixation includes the immobilization of the spine by the use of a pair of spine rods that run generally parallel to the spine. In practicing this technique, bone screws are first fastened to the pedicles of the appropriate vertebrae or to the sacrum and act as the anchor points for the spine rods. The bone screws are generally placed two per vertebra, one at each pedicle on either side of the spinous process. Clamp assemblies join the spine rods to the screws. The spine rods are generally custom-bent to achieve the desired curvature of the spinal column. Examples of such spinal fixation devices can be found in U.S. Pat. Nos. 4,653,481 and 5,030,220, which are incorporated herein by reference. For some applications, rather than using bone screws, lamina hooks can be fastened to a spine rod to connect the rod to a vertebra for distraction or compression.

#Features, aspects and advantages of the invention will be more fully understood when considered with respect to the following detailed description, appended claims and accompanying drawings where:

#FIGS. 1 and 1a are diagrammatic posterior views of portions of two different spinal fixation systems, each of which includes a branch connector of the present invention installed on a portion of the spinal column;

#FIG. 2 is a diagrammatic posterior view of a spinal fixation system including a cross brace assembly of the present invention installed on a portion of the spinal column;

#The present invention relates to branch connectors for use in connecting spine rods, the spine rods being part of a spinal fixation system useful for treating various spinal disorders. Such branch connectors can have various functions. A branch connector can be used as a branch clamp to connect a pair of spine rods that run in series in the same general direction along the spine, each rod being fastened to a different portion of the spine. A pair of modified branch connectors can also be used along with a transverse rod to form a cross brace assembly. Such a cross brace assembly is useful for providing additional lateral support to a pair of parallel spine rods fastened to the same general portions of the spine, but on opposite sides of the spinous process.

#FIGS. 1, 1a, 2 and 3 illustrate various embodiments of branch connectors in place on a spine. These figures illustrate spinal fixation systems that generally use rods, pedicle screws, lamina hooks and clamps to provide the necessary support for immobilizing a spine. Screw-and-clamp or "screw-clamp" assemblies 12 are fastened to the sacrum and in FIGS. 1, 1a and 2, to the pedicles of the fifth lumbar. The details of such general screw-clamp assemblies are known, for example, as described in U.S. Pat. Nos. 4,653,481 and 5,030,220. In FIGS. 1 and 1a, two pairs of spine rods provide the vertical support for each system. Spine rods 14 fasten to the screw-clamp assemblies 12 at the sacrum and the lower lumbar vertebra. In FIG. 1, spine rods 16 fasten to the screw clamp at the third lumbar vertebra and could extend further, possibly into the thoracic region of the spine (not shown). In FIG. 1a, spine rods 16 fasten to lamina hooks 17 at the second lumbar vertebra.

#Segmented spine rods can be used for various reasons. They are particularly useful when the spine rods are to be attached over a large number of vertebrae. In such an application, a long spine rod can be very cumbersome and difficult to install. It is easier to attach a number of different segments of spine rods to various portions of the spine. Once fastened to their respective screw clamp assemblies, the rods can then be clamped to one another in series by branch connectors of this invention. Another reason for using segments of spine rod rather than one continuous spine rod is that in the lower lumbar and sacral region, the screw clamp assemblies are generally installed a greater distance laterally from the centerline of the spine as compared to the screw-clamp assemblies or lamina hooks located higher on the spine. As a result, a sharp bend in the spine rod would often be required to properly position the rod. To avoid such a sharp bend in the spine rod, it is easier to use segmented spine rods which are first fastened to the appropriate screw-clamps, and then fastened to one another with a branch connector of the present invention. Because the spine rods are received in slightly spaced apart openings of the branch connector, less bending of the rods is necessary. Of course, the ends of the spine rods that are to be joined must be appropriately bent a small amount so that the spine rods will properly seat in the openings.