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 fixation devices to one or more vertebrae and connecting the devices 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 fixation devices 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, a fixation device 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.
Typically, fixation devices may include a bone fastener (e.g., bone screw, hook, etc.) for coupling the fixation device to vertebra. Fixation devices further may include a tulip element for coupling the bone fastener to the elongated rod. Clamp and/or wedge elements may be used to secure the bone fastener in the tulip element. A locking cap may be used to secure the rod in the tulip element. While these designs can be used in the treatment of spinal irregularities, they typically require loading of the bone fastener from the top of the tulip element. One drawback to this top-loading design is that different sizes of the tulip element must be used based on the diameter of the bone fastener to accommodate passage of the fastener through the tulip element, as the inner bore of the tulip element will generally need to be larger than either the combined size of the bone fastener head and clamp element or the bone fastener diameter. Another drawback to this top-loading design is that bone hooks cannot be used as they will generally not pass through the tulip element. Yet another drawback to this top-loading design is that bone fastener must be installed in the bone while attached to the tulip element.
Accordingly, there exists a need for new and improved orthopedic fixation devices.