Cortical bone trajectory screws used to save failed traditional trajectory screws in the osteoporotic lumbar spine and vice versa: a human cadaveric biomechanical study

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Traditional trajectory (TT) screws are widely used in lumbar fixation. However, they may require revision surgery in some instances, especially in patients with osteoporotic spines. Cortical bone trajectory (CBT) screws may potentially be used to rescue a failed TT screw and vice versa in nonosteoporotic spines. This study aimed to investigate whether a CBT screw can salvage a compromised TT screw in osteoporotic lumbar spines and vice versa.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>A total of 42 vertebrae from 17 cadaveric lumbar spines were obtained. Bone mineral density was measured, and a CBT screw was randomly inserted into one side of each vertebra. A TT screw was then inserted into the contralateral side. The biomechanical properties of the screws were tested to determine their insertional torque, pullout strength, and fatigue performance. After checking the screws for the failure of each specimen, the failed screw track was salvaged with a screw of the opposite trajectory. The specimen was then subjected to the same mechanical tests, and results were recorded. A repeat pullout test on TT and CBT screws was also performed.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>When CBT screws were used to rescue failed TT screws, the original torque increased by 50%, an average of 81% of the pullout strength of the initial TT screws was retained, and the fatigue performance was equal to that of the original screws, which were considerably stronger than the loose TT screws—that is, the TT repeat screws/TT screws were 33% of the pullout strength of the initial TT screws. When the TT screws were used to salvage the compromised CBT screws, the TT screws retained 51% of the original torque and 54% of the original pullout strength, and these screws were still stronger than the loose CBT screws—that is, the loose CBT screws retained 12% pullout strength of the initial CBT screws. Fatigue performance and the ratio of the pullout strength considerably decreased between the CBT rescue screws and the original CBT screws but slightly changed between the TT rescue screws and the original TT screws.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>CBT and TT screws can be applied in a revision technique to salvage each other in osteoporotic lumbar spines. Additionally, CBT and TT screws each retain adequate insertional torque, pullout strength, and fatigue performance when used for revision in osteoporotic lumbar spines.</jats:p></jats:sec>

Biomechanical Analysis of Cortical Bone Trajectory Screw Versus Bone Cement Screw For Fixation In Porcine Spinal Low Bone Mass Model

“…Through CT examination, Teo et al found that the thickness, number and space of bone trabeculae in porcine spine and human spine were very similar [21] , as shown in Table .4. In addition, the study of Zhang et al used spinal specimens of human with osteoporosis, and the results of maximum insertional torque and pullout load were similar to those of this study [22] , as shown in Table .5. On the other hand, rapid decalcitration of porcine spine with EDTA solution is also a common method, which can be used to prepare a reproducible in vitro model of osteoporotic animal vertebral body in a simple and rapid manner [8] .…”

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

“…The CBT is a relatively new spinal fixation technique involving a unique caudocephalad and medial-to-lateral screw trajectory (Santoni et al, 2009). The biomechanical properties of CBT screws are superior to those of traditional pedicle screws (Santoni et al, 2009;Sansur et al, 2016;Zhang et al, 2019). Therefore, CBT is a better choice in treating osteoporotic patients (Ueno et al, 2013).…”

Evaluating Minimally Invasive Spine Surgery With Midline Cortical Bone Trajectory Screw Fixation for Lumbar Degenerative Disease in a Retrospective Study of 200 Patients

“…In addition, in vivo insertion torque of the CBT screws increased by 1.71 times compared to that of conventional PS. Zhang et al 12 found that CBT screws had better biomechanical performance in pullout strength and toggle tests than did conventional PS. It is known that CBT screw/rod structures provide almost the same stability as conventional PS-rod structures.…”