Skeletal structures are formed of bones and adjoining structures which include cartilage, for instance. For various reasons, these skeletal structures may require artificial support or stabilization. For example, the human spine is composed of a column of thirty-three bones, called vertebrae, and their adjoining structures. The twenty-four vertebrae nearest the head are separate bones capable of individual movement and generally are connected by anterior and posterior longitudinal ligaments and by discs of fibrocartilage, called intervertbral discs, positioned between opposing faces of adjacent vertebrae. The twenty-four vertebrae are commonly referenced in three sections. The cervical spine, closest to the head and often referenced as the “neck,” comprises the first seven vertebrae of the spine. The thoracic spine and the lumbar spine are below the cervical spine. Each of these vertebrae include a vertebral body and a dorsal arch that enclose an opening, called the vertebral foramen, through which the spinal cord and spinal nerves pass. The remaining nine vertebrae located below the lumbar spine are fused to form the sacrum and the coccyx and are incapable of individual movement.
Pedicle screws can be used in spinal surgeries for various applications such as fusion of vertebra, correction of spinal deformities, and treatment of fractures. In these uses, the pedicle screw is inserted into the vertebral body via the narrowed pillar portion of the spine, the pedicle, and extends through the pedicle when properly positioned. The pedicle comprises a cancellous or spongy, porous, bone structure. The introduction of a pedicle screw to a vertebral body can result in various complications, including but not limited to the “break-out” of the pedicle screw through the pedicle wall. Where the pedicle screw is implemented in the thoracic spine, injury to the thoracic spinal cord can occur. A lateral break-out can result in damages to surrounding blood vessels and other structures. In order to minimize the likelihood of such complications surgeons often use a pedicle screw that is greatly reduced in size as compared to the pedicle such as to provide a safety margin in the insertion.
However, particularly in the thoracic and lumbar spine, eighty percent of the pull out strength is obtained by the fit of the pedicle screw into the pedicle. As such, the maximum size pedicle screw for the size pedicle lends the maximum pull out strength. Insertion of rigid members, such the pedicle screw and a typical pedicle tap, into a pedicle that are of such a desired size can result in perforation of the pedicle.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.