Application study of three-dimensional printed navigation template between traditional and novel cortical bone trajectory on osteoporosis lumbar spine

Cortical bone trajectory (CBT) is increasingly used in spinal surgery. Although there are many biomechanical studies, the biomechanical effect of CBT in combination with traditional pedicle screws is not detailed. Therefore, the purpose of this study was to investigate the effects of the traditional pedicle screw and CBT screw implantation on the lumbar spine using finite element methods. Based on the combination of the traditional pedicle screw and the CBT system implanted into the lumbar spine, four finite element spinal lumbar models were established. The models were given four different load conditions (flexion, extension, lateral bending, and axial rotation), and the deformation and stress distribution on the finite element model were observed. The results show that there was no significant difference in the structural stability of the lumbar spine model between the traditional pedicle screw system and the CBT system. In addition, CBT may reduce stress on the endplate. Different movements performed by the model may have significant biomechanical effects on the spine and screw system. Clinical spinal surgeons may also consider using the CBT system in revision spinal surgery, which may contribute to smaller wounds.

Download Full-text

Risk of pedicle and spinous process violation during cortical bone trajectory screw placement in the lumbar spine

BMC Musculoskeletal Disorders ◽

10.1186/s12891-020-03535-4 ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Lilian Zhang ◽

Naifeng Tian ◽

Jian Yang ◽

Wenfei Ni ◽

Liya Jin

Keyword(s):

Lumbar Spine ◽

Cortical Bone ◽

Spinous Process ◽

Screw Placement ◽

Cortical Bone Trajectory

Download Full-text

Validation of a freehand technique for cortical bone trajectory screws in the lumbar spine

Journal of Neurosurgery Spine ◽

10.3171/2019.1.spine181402 ◽

2019 ◽

Vol 31 (2) ◽

pp. 201-208 ◽

Cited By ~ 1

Author(s):

Zachary Tan ◽

Stewart McLachlin ◽

Cari Whyne ◽

Joel Finkelstein

Keyword(s):

Lumbar Spine ◽

Cortical Bone ◽

Pedicle Screw ◽

Ex Vivo ◽

Screw Placement ◽

Anatomical Landmarks ◽

Cortical Bone Trajectory ◽

Screw Insertion ◽

Freehand Technique ◽

Ex Vivo Study

OBJECTIVEThe cortical bone trajectory (CBT) technique for pedicle screw placement has gained popularity among spinal surgeons. It has been shown biomechanically to provide better fixation and improved pullout strength compared to a traditional pedicle screw trajectory. The CBT technique also allows for a less invasive approach for fusion and may have lower incidence of adjacent-level disease. A limitation of the current CBT technique is a lack of readily identifiable and reproducible visual landmarks to guide freehand CBT screw placement in comparison to the well-defined identifiable landmarks for traditional pedicle screw insertion. The goal of this study was to validate a safe and intuitive freehand technique for placement of CBT screws based on optimization of virtual CBT screw placement using anatomical landmarks in the lumbar spine. The authors hypothesized that virtual identification of anatomical landmarks on 3D models of the lumbar spine generated from CT scans would translate to a safe intraoperative freehand technique.METHODSCustomized, open-source medical imaging and visualization software (3D Slicer) was used in this study to develop a workflow for virtual simulation of lumbar CBT screw insertion. First, in an ex vivo study, 20 anonymous CT image series of normal and degenerative lumbar spines and virtual screw insertion were conducted to place CBT screws bilaterally in the L1–5 vertebrae for each image volume. The optimal safe CBT trajectory was created by maximizing both the screw length and the cortical bone contact with the screw. Easily identifiable anatomical surface landmarks for the start point and trajectory that best allowed the reproducible idealized screw position were determined. An in vivo validation of the determined landmarks from the ex vivo study was then performed in 10 patients. Placement of virtual “test” cortical bone trajectory screws was simulated with the surgeon blinded to the real-time image-guided navigation, and the placement was evaluated. The surgeon then placed the definitive screw using image guidance.RESULTSFrom the ex vivo study, the optimized technique and landmarks were similar in the L1–4 vertebrae, whereas the L5 optimized technique was distinct. The in vivo validation yielded ideal, safe, and unsafe screws in 62%, 16%, and 22% of cases, respectively. A common reason for the nonidealized trajectories was the obscuration of patient anatomy secondary to severe degenerative changes.CONCLUSIONSCBT screws were placed ideally or safely 78% of the time in a virtual simulation model. A 22% rate of unsafe freehand trajectories suggests that the CBT technique requires use of image-guided navigation or x-ray guidance and that reliable freehand CBT screw insertion based on anatomical landmarks is not reliably feasible in the lumbar spine.

Download Full-text

Double-trajectory lumbar screw placement guided by a set of 3D-printed surgical guide templates: a cadaver study

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-04149-0 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Yonghui Zhao ◽

Jinlong Liang ◽

Haotian Luo ◽

Yongqing Xu ◽

Sheng Lu

Keyword(s):

Lumbar Spine ◽

Cortical Bone ◽

Pedicle Screws ◽

Ct Scanning ◽

Cadaver Study ◽

Screw Placement ◽

Depth Of Penetration ◽

Cortical Bone Trajectory ◽

Surgical Guide ◽

3D Printed

Abstract Background To improve the strength of posterior spine fixation in patients with osteoporosis, some scholars have proposed a method of simultaneously inserting traditional pedicle screws and cortical bone trajectory screws into the pedicle. However, due to the difficulty of the operation and few clinical applications, the safety and accuracy of this method are still unclear. The purpose of this study was to investigate the safety and accuracy of double-trajectory lumbar screw placement guided by surgical guide templates. Methods Six wet lumbar specimens were selected for computed tomography (CT) scanning, a three-dimensional (3D) model of the lumbar spine was established using computer software, and surgical guide templates for double-trajectory [traditional pedicle trajectory (TPT) and cortical bone trajectory (CBT)] lumbar screw placement at various segments of the lumbar spine were designed and printed using a 3D printer. Screw placement was guided only by the surgical guide template, with no fluoroscopy. Postoperative CT examination was performed to determine whether the screw penetrated the screw path and the location and depth of penetration of the cortex. The preoperative and postoperative sagittal and axial angles of CBT screws or TPT screws were also measured and compared. Results Four screws were placed in each vertebral body of six lumbar specimens for a total of 120 screws. Screw grades: 99 screws as grade 0, 15 as grade 1, six as grade 2, and zero as grade 3. Thus, grade 0 accounted for 82.5% of the screws. No significant differences in the preoperative and postoperative angles of the screws were found (P > 0.05). Conclusions 3D-printed surgical guide templates for double-trajectory screw placement can reduce the difficulty of surgery and the use of intraoperative fluoroscopy. Using such templates is a safe, feasible, and accurate screw placement method.

Download Full-text