A Pull-Out Resistant Pedicle Screw for the Osteoporotic Spine

Pedicle screws are commonly used in spine surgery to implant and affix metal devices to the spine. These screws are most commonly associated with cases that require rod or plate implantation. Use of pedicle screws in osteoporotic patients, however, is limited because they suffer from low bone mass density (BMD). The low BMD is harmful to patients in two ways — it leads to increased incidence of spinal trauma and also prevents surgeons from instrumenting osteoporotic patients because screws do not achieve the required fixation in osteoporotic patients [1]. The risk of trauma is increased due to the brittle bone and vertebral compression fractures, resulting in spinal misalignment and increased risk of future trauma. Instrumenting these cases with rods or plates, however, is impossible because osteoporotic bone is not strong enough to “hold” pedicle screws in, i.e., prevent screws from pulling out [2, 3].