Technology Background: Pedicle Screws

Here's background information on pedicle screws, which are used to facilitate spinal fixation. We review recent developments, how the technology is used, what product specifications are important, and more.

Pedicle screws facilitate spinal fixation and are most often used to promote fusion between spinal levels in order to treat degradation and deformities. Once driven into the pedicles—stemlike projections on each vertebral body that connect the front and back sections of the vertebra—they affix rods between multiple vertebrae. This provides stabilization to the anatomy and encourages eventual fusion of the vertebral bodies in conjunction with other implant materials, such as bone grafts, demineralized bone matrix, bone morphogenic proteins, and specialized cages. Pedicle screws are indicated for use in the thoracic, lumbar, or sacral (i.e., noncervical) regions of the spine.

Pedicle screws are metallic—typically titanium alloy, pure titanium, cobalt chromium, or stainless steel. They have threads of varying design (e.g., dual thread, square, reverse thread, buttress) to grip the prepared anatomical site and minimize the risk of postoperative implant loosening. They feature a tulip-shaped head that can be either fixed or mobile and provide a space for spinal rod fixation to promote spinal stability during the fusion process. Pedicle screw implants are accompanied by required proprietary surgical instrumentation such as awls, bores, taps, and probes to prep the vertebral body for screw insertion.

Pedicle screws were first used in the 1950s. Over time, the technology has added rods to affix multiple levels of the spine together, as well as evolving screw geometries to optimize fixation, ease of implantation, and patient range of motion. More recent developments include screws with thicker inner diameters to improve fatigue strength, conical screws to promote additional compression in the bone around the screw, and dual-threaded screws for faster insertions.

Pedicle screws are considered the gold standard for achieving spinal stability during fusion. However, osteoporotic vertebral bone can still make...