Cortical bone trajectory for pedicle screws / 中华骨科杂志

ABSTRACT

Pedicle screw fixation is widely used in spine surgery, which allows 3?dimensional fixation with a more rigid construct and permits a shorter fusion length. However, conventional pedicle screw fixation has some drawbacks, including signifi?cant muscle dissection for the exposure of bone marks. Although percutaneous pedicle screw technique can compensate for above defects, it requires an additional approach for decompression and bone graft insertion. Besides, the percutaneous pedicle screw technique depends on intraoperative multiplanar fluoroscopy, which results in high risk of radiation exposure of the surgeons and patients. Screw loosening is a well?known complication, especially in osteoporosis patients. Several methods can enhance screw stability, for example, modifying screw design and augmenting vertebral bodies with reinforcing materials that can improve the structural capacity of the deteriorated tissue, however, they also have some disadvantages. Although we can enhance bone?screw by modifying screw design, it is not useful in severe osteoporosis patients. At the same time, bone cement can increase pedicle screw axial pullout strength and fatigue resistance, however, it is associated with a number of inherent disadvantages such as its high exothermic polymerizing temperature, toxicity of the monomer, and risk of leakage to the spinal canal. Santoni et al. intro?duced cortical bone trajectory (CBT) for lumbar pedicle screw with a new screw design that is shorter and smaller in diameter which has been proposed to maximize the thread contact with this higher density bone surface. In addition, the CBT technique fol?lows a caudocephalad path sagittally and a laterally directed path in the transverse plane, engaging only cortical bone in the pedi?cle without the involvement of the vertebral body trabecular space. Finally, the screw insertion point of this technique locates around lateral pars, enabling less tissue dissection. Therefore, it can be an alternative approach to enhance screw fixation strength, and it may rescue failed pedicle screw and be used in minimally invasive spine surgery.