Many types of spinal irregularities can cause pain, limit range of motion, or injure the nervous system within the spinal column. These irregularities can result from, without limitation, trauma, tumor, disc degeneration, and disease. Often, these irregularities are treated by immobilizing a portion of the spine. This treatment typically involves affixing a plurality of screws and/or hooks to one or more vertebrae and connecting the screws or hooks to an elongate rod that generally extends in the direction of the axis of the spine.
Treatment for these spinal irregularities often involves using a system of pedicle screws and rods to attain stability between spinal segments. Instability in the spine can create stress and strain on neurological elements, such as the spinal cord and nerve roots. In order to correct this, implants of certain stiffness can be implanted to restore the correct alignment and portion of the vertebral bodies. In many cases, an anchoring member such as a pedicle screw along with a vertical solid member can help restore spinal elements to a pain free situation, or at least may help reduce pain or prevent further injury to the spine.
As the science and technology of spine surgery continues to progress, there is an increasing interest in developing alternative, minimally invasive, methods to conventional “open” spine surgery. The goals of these less invasive alternatives are to avoid the surgical exposure, dissection, and retraction of muscles and tissues that is necessary with “open” surgery. In general, a minimally invasive spine surgery system should be able to perform the same procedure as the traditional open technique, but through smaller incisions instead of one longer incision. As a result, some physicians feel that using a minimally invasive spine surgery system generally causes less soft tissue damage, reduces blood loss and reduces recovery time. In addition, patients generally prefer the smaller scars that are left using a minimally invasive approach
Historically, spine fusion surgery including pedicle screw fixation with deep placement of rods has been one area that has presented significant challenges for minimally invasive approaches. However, advancement in technologies such as fluoroscopy and improvements in optics have contributed to the advent of a few minimally invasive spine fusion surgery techniques.
One example of instruments and techniques for performing surgery using minimally invasive techniques is found in U.S. Pat. No. 6,530,929 to Justis et al. The '929 patent discloses a brace installation instrument that is mounted to anchors secured in an animal subject. The installation instrument includes anchor extensions coupled to the anchors. The instrument is movable with respect to the anchors to position a brace in a position more proximate the anchors. The brace can be indexed for insertion at a predetermined orientation with respect to the installation instrument. The brace is inserted through an independent incision in the animal subject and swings along an arc that has a radius of curvature equal to the distance between the anchors and the end of the anchor extensions. While these techniques are steps in the right direction, there remains a need for instruments and methods for vertebral stabilization using minimally invasive techniques.