Review of Cortical Bone Trajectory: Evidence of a New Technique

Abstract

This article summarizes recent evidence on the cortical bone trajectory (CBT) obtained from published anatomical, biomechanical, and clinical studies. CBT was proposed by Santoni in 2009 as a new trajectory that can improve the fixation of pedicle screws in response to screw loosening in osteoporotic patients. Recently, research interest has been growing with increasing numbers of published series and frequent reports of new applications. We performed an online database search using the terms "cortical bone trajectory," "pedicle screw," "CBT spine," "CBT fixation," "MISS CBT," and "traditional trajectory." The search included the PubMed, Ovid MEDLINE, Cochrane, and Google Scholar databases, resulting in an analysis of 42 articles in total. These covered three aspects of CBT research: anatomical studies, biomechanical parameters, and clinical cases or series. Compared to the traditional trajectory, CBT improves pullout strength, provides greater stiffness in cephalocaudal and mediolateral loading, and shows superior resistance to flexion/extension; however, it is inferior in lateral bending and axial rotation. CBT seems to provide better immediate implant stability. In clinical studies, CBT has shown better perioperative results for blood loss, length of stay in hospital, and surgery time; similar or better clinical postoperative scores; and similar comorbidity, without any major fixation system complications due to instrumentation failure or screw misplacement. In addition, advantages such as less lateral exposure allow it to be used as a minimally invasive technique. However, most of the clinical studies were retrospective case series or case-control studies; prospective evidence on this technique is scarce, making a definitive comparison with the traditional trajectory difficult. Nevertheless, we can conclude that CBT is a safe technique that offers good clinical results with similar biomechanical and perioperative parameters to those of the traditional trajectory. In addition, new applications can improve its results and make it useful for additional pathologies.

Keywords: CBT anatomy; CBT biomechanics; CBT complications; Cortical bone trajectory; Pedicle screw; Traditional trajectory.

Fig. 1. Comparison of the traditional trajectory (A, B) and cortical bone trajectory (C, D). (A, B) Axial and sagittal views of the traditional trajectory following the pedicle axis in a lateral-to-medial trajectory parallel to the superior and inferior endplates. (C, D) Axial and sagittal views of the cortical bone trajectory with a medial-to-lateral disposition and a 25°–30° cranial direction along the inferior border of the pedicle.