• Cortical bone trajectory
• Lumbar interbody fusion
• Minimally invasive
• Robot-assisted surgery

• Humans
• Bone Screws
• Cortical Bone/surgery
• Cortical Bone/diagnostic imaging
• Lumbar Vertebrae/surgery
• Lumbar Vertebrae/diagnostic imaging
• Minimally Invasive Surgical Procedures/methods
• Pedicle Screws
• Psoas Muscles/surgery
• Robotic Surgical Procedures/methods
• Spinal Fusion/methods
• Spinal Fusion/instrumentation

• diseases
• medical research

• Humans
• Spinal Fusion/methods
• Spinal Fusion/adverse effects
• Male
• Female
• Lumbar Vertebrae/surgery
• Middle Aged
• Minimally Invasive Surgical Procedures/methods
• Retrospective Studies
• Intervertebral Disc Degeneration/surgery
• Aged
• Treatment Outcome
• Pedicle Screws

• No. Q19058 Youth Innovation Project of the Sichuan Medical Association

• cortical screw
• pedicle screw
• robot-assisted navigation
• satellite rod
• vertebral compression fracture

• Globus Medical, Inc.

• Adjacent segment disease
• Facet joint fusion
• Fusion rate
• In situ fusion
• Posterolateral fusion
• Revision surgery

• Humans
• Spondylolisthesis/surgery
• Male
• Female
• Spinal Fusion/methods
• Spinal Fusion/instrumentation
• Middle Aged
• Lumbar Vertebrae/surgery
• Aged
• Pedicle Screws
• Retrospective Studies
• Treatment Outcome
• Cortical Bone/surgery
• Adult
• Bone Screws

• case report
• cortical bone trajectory
• neuronavigation
• new technologies in neurosurgery
• new technology in spine surgery
• operative technique
• pedicle screw
• spine revision
• spine surgery

• Cortical bone trajectory technique
• clinical outcome
• complication
• posterior lumbar interbody fusion

• Humans
• Pedicle Screws/adverse effects
• Lumbar Vertebrae/surgery
• Spinal Fusion/methods
• Bone and Bones
• Cortical Bone/surgery

• Cortical bone trajectory
• Finite element analysis
• Hybrid fixation
• Modified cortical bone trajectory
• Transforaminal lumbar interbody fusion

• Cortical bone trajectory pedicle screw
• Prospective
• Randomized controlled trial
• Traditional trajectory pedicle screw
• Transforaminal lumbar interbody fusion

• Humans
• Pedicle Screws/adverse effects
• Spinal Fusion/methods
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/surgery
• Prospective Studies
• Treatment Outcome
• Cortical Bone/diagnostic imaging
• Cortical Bone/surgery
• Pain/etiology

• Y20220211 Wenzhou Science and Technology Bureau Foundation
• No. LY21H060009 Zhejiang Provincial Natural Science Foundation
• No. SAHoWMU-CR2017-08-106 Clinical Scientific Research Project of the Second Affiliated Hospital of Wenzhou Medical University

• Humans
• Follow-Up Studies
• Retrospective Studies
• Cervical Vertebrae/diagnostic imaging
• Cervical Vertebrae/surgery
• Bone Screws
• Tomography, X-Ray Computed
• Spinal Fusion/methods
• Pedicle Screws

• Cortical bone trajectory screw
• Lumbar degenerative disease
• Posterior lumbar interbody fusion
• Titanium-coated PEEK cage

• Humans
• Titanium
• Retrospective Studies
• Cortical Bone/diagnostic imaging
• Cortical Bone/surgery
• Pedicle Screws
• Polyethylene Glycols
• Ketones
• Spinal Fusion/methods
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/surgery
• Treatment Outcome
• Benzophenones
• Polymers

• lumbar spine surgery
• pedicle screw placement
• posterior spinal fixation and fusion
• posterior spinal instrumented fusion
• spine instrumentation

• cortical bone trajectory screw
• bone cement screw
• biomechanical analysis
• porcine spinal model

• Animals
• Swine
• Bone Cements/pharmacology
• Prospective Studies
• Lumbar Vertebrae/surgery
• Bone Screws
• Cortical Bone/surgery

• Finite element analysis
• Hybrid fixation
• Modified cortical bone trajectory
• Pedicle screw
• Transforaminal lumbar interbody fusion

• 2022-JKCS-19 Central-class Public Welfare Research Institute Project of Chinese Academy of Medical Sciences

• Cortical bone trajectory
• Cortical screw
• Cross-link
• Interbody fusion
• TLIF

• Facet-sparing
• Interbody fusion
• PLIF
• TLIF
• Unilateral

• endplate stress
• finite element
• lumbar interbody fusion
• osteoporosis
• porous scaffold

• 3D patient-matched template guides
• Cortical bone trajectory
• Degenerative disc disease
• Minimally invasive spine surgery
• Screw accuracy

• Adult
• Humans
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/surgery
• Retrospective Studies
• Bone and Bones
• Cortical Bone/diagnostic imaging
• Cortical Bone/surgery
• Pedicle Screws
• Spinal Fusion/methods

The cortical bone trajectory (CBT) is a novel technique in lumbar fixation and fusion. The unique caudocephalad and medial-lateral screw trajectories endow it with excellent screw purchase for vertebral fixation via a minimally invasive method. The combined use of CBT screws with transforaminal or posterior lumbar interbody fusion can treat a variety of lumbar diseases, including spondylolisthesis or stenosis, and can also be used as a remedy for revision surgery when the pedicle screw fails. CBT has obvious advantages in terms of surgical trauma, postoperative recovery, prevention and treatment of adjacent vertebral disease, and the surgical treatment of obese and osteoporosis patients. However, the concept of CBT internal fixation technology appeared relatively recently; consequently, there are few relevant clinical studies, and the long-term clinical efficacy and related complications have not been reported. Therefore, large sample and prospective studies are needed to further reveal the long-term complications and fusion rate. As a supplement to the traditional pedicle trajectory fixation technique, the CBT technique is a good choice for the treatment of lumbar diseases with accurate screw placement and strict indications and is thus deserving of clinical recommendation.

• Cortical bone trajectory
• Management of midle line fusion
• Lumbar interbody fusion
• Lumbar surgery
• Review

Lumbar degenerative disc disease (DDD) in the elderly population remains a global health problem, especially in patients with osteoporosis. Osteoporosis in the elderly can cause failure of internal fixation. Cortical bone trajectory (CBT) is an effective, safe and minimally invasive technique for the treatment of lumbar DDD in patients with osteoporosis. In this review, we analyzed the anatomy, biomechanics, and advantages of the CBT technique in lumbar DDD and revision surgery. Additionally, the clinical trials and case reports, indications, advancements and limitations of this technique were further discussed and reviewed. Finally, we concluded that the CBT technique can be a practical, effective and safe alternative to traditional pedicle screw fixation, especially in DDD patients with osteoporosis.

• Lumbar degenerative disc diseases
• Cortical bone trajectory screw
• Anatomy
• Biomechanics
• Indications
• Clinical trials and case reports
• Advancements

• cortical bone trajectory
• functional spinal unit
• pedicle screws
• porcine model
• screw pullout test

To provide reference data on CBT pedicle screws from CT measurements of L1 to L5 in the Chinese Han population and to assess the treatment efficacy of CBT pedicle screws in cases of lumbar degenerative disease.

In total, 100 patients were identified from the CT database for CBT morphometric measurement of the lumbar spine. According to sex and age, patients were divided into four groups. The diameter, length, and angle of the vertebral pedicle and trajectory were measured. Then, a total of 36 patients with lumbar degenerative disease were included in this study for clinical and radiographic evaluation. Demographic characteristics, health-related quality of life (HRQOL), and extent of intervertebral disc herniation and spondylolisthesis were evaluated.

The mean diameter and the mean length varied from L1 to L5 in Groups I to IV. The lateral angles ranging from L1 to L5 were 8.9 to 9.2°, 8.7 to 12.2°, 8.7 to 11.2°, and 9.2 to 10.1° in Groups I to IV, respectively. The cephalad angles from L1 to L5 were 23.5 to 28.6°, 24.7 to 26.6°, 25.0 to 28.2°, and 24.7 to 27.9° in Groups I to IV, respectively. In the case series, all patients’ neurological function and HRQOL were significantly improved at the final follow-up (p < 0.0001), and 75% of patients achieved satisfaction.

The morphology of the lumbar vertebral pedicle varied from L1 to L5, and the trajectory was feasible and safe. CBT pedicle screws were effective in treating lumbar degenerative diseases and benefited the patients.

• cortical bone trajectory
• lumbar spine
• nomogram
• screw loosening
• spine

Oblique lateral interbody fusion (OLIF) is widely used to treat lumbar degenerative disc disease. This study aimed to evaluate the biomechanical stability of OLIF, OLIF including posterior pedicle screw and rod (PSR), and OLIF including cortical screw and rod (CSR) instrumentation through finite element analysis.

A complete L2-L5 finite element model of the lumbar spine was constructed. Surgical models of OLIF, such as stand-alone, OLIF combined with PSR, and OLIF combined with CSR were created in the L3-L4 surgical segments. Range of motion (ROM), end plate stress, and internal fixation peak stress were compared between different models under the same loading conditions.

Compared to the intact model, ROM was reduced in the OLIF model under all loading conditions. The surgical models in order of increasing ROM were PSR, CSR, and stand-alone; however, the difference in ROM between BPS and CSR was less than 0.4° and was not significant under any loading conditions. The stand-alone model had the highest stress on the superior L4 vertebral body endplate under all loading conditions, whereas the end plate stress was relatively low in the BPS and CSR models. The CSR model had the highest internal fixation stress, concentrated primarily at the end of the screw.

OLIF alone significantly reduces ROM but does not provide sufficient stability. Addition of posterior PSR or CSR internal fixation instrumentation to OLIF surgery can significantly improve biomechanical stability of the segment undergoing surgery.

To investigate the effect of the in situ screw implantation region and angle on the stability of lateral lumbar interbody fusion (LLIF) from a biomechanical perspective.

A validated L2‐4 finite element (FE) model was modified for simulation. The L3‐4 fused segment undergoing LLIF surgery was modeled. The area between the superior and inferior edges and the anterior and posterior edges of the vertebral body (VB) is divided into four zones by three parallel lines in coronal and horizontal planes. In situ screw implantation methods with different angles based on the three parallel lines in coronal plane were applied in Models A, B, and C (A: parallel to inferior line; B: from inferior line to midline; C: from inferior line to superior line). In addition, four implantation methods with different regions based on the three parallel lines in horizontal plane were simulated as types 1–2, 1–3, 2–2, and 2–3 (1–2: from anterior line to midline; 1–3: from anterior line to posterior line; 2–2: parallel to midline; 2–3: from midline to posterior line). L3‐4 ROM, interbody cage stress, screw‐bone interface stress, and L4 superior endplate stress were tracked and calculated for comparisons among these models.

The L3‐4 ROM of Models A, B, and C decreased with the extent ranging from 47.9% (flexion‐extension) to 62.4% (lateral bending) with no significant differences under any loading condition. Types 2–2 and 2–3 had 45% restriction, while types 1–2 and 1–3 had 51% restriction in ROM under flexion‐extension conditions. Under lateral bending, types 2–2 and 2–3 had 70.6% restriction, while types 1–2 and 1–3 had 61.2% restriction in ROM. Under axial rotation, types 2–2 and 2–3 had 65.2% restriction, while types 1–2 and 1–3 had 59.3% restriction in ROM. The stress of the cage in types 2–2 and 2–3 was approximately 20% lower than that in types 1–2 and 1–3 under all loading conditions in all models. The peak stresses at the screw‐bone interface in types 2–2 and 2–3 were much lower (approximately 35%) than those in types 1–2 and 1–3 under lateral bending, while no significant differences were observed under flexion‐extension and axial rotation. The peak stress on the L4 superior endplate was approximately 30 MPa and was not significantly different in all models under any loading condition.

Different regions of entry‐exit screws induced multiple screw trajectories and influenced the stability and mechanical responses. However, different implantation angles did not. Considering the difficulty of implantation, the ipsilateral‐contralateral trajectory in the lateral middle region of the VB can be optimal for in situ screw implantation in LLIF surgery.

• Finite element analysis
• In situ screw
• Lateral lumbar interbody fusion
• Stability
• Surgical procedures

The cortical bone trajectory (CBT) screws follow a caudocephalad and lateral path from the pedicle to the vertebral body. The bone fusion rate of CBT fixation is equal to or lower than conventional pedicle screw fixation. It remains unclear whether or not CVT screws exert equally compressive forces across the vertebral column. In this study, we intraoperatively examined the insertional torque of CBT screws, and investigated the compression loading and pressure distribution in conventional and CBT fixation using pig bones.

The insertional torque was measured for a total of 115 CBT screws. Detailed positions of these screws were retrospectively confirmed using CT scans. Screw loosening and interbody fusion were examined 1 year after surgery. In the experiment using pig bones, we inserted screws by conventional trajectory (n = 3) and CBT (n = 4).

Multiple regression analysis showed that the total screw length, the distance from the screw to the medial border of the pedicle and the distance from the superior endplate of the vertebrae were significant independent factors affecting the insertional torque. There was no significant association between the insertional torque and the radiographic bone fusion rate 12 months after surgery. The average pressure and the compression loading in the anterior column were significantly lower in CBT group.

These results suggested that the long CBT screws as close to the endplate had high insertional torque, but the anterior column in CBT fixation showed low compression force leading to the insufficient holding intervertebral cage. CBT screws may cause the micromotion of cages, which lowers the bone fusion rate.

• cortical bone trajectory
• lumbar fusion surgery
• meta-analysis
• traditional pedicle screws

• augmentation
• hydroxyapatite granules
• minimally invasive spinal treatment
• minimally invasive spine stabilization
• osteoporosis
• pedicle screw
• percutaneous pedicle screw
• screw loosening
• spine
• spine surgery

• Benzophenones
• Bone Screws
• Cortical Bone/surgery
• Humans
• Lumbar Vertebrae/surgery
• Polymers
• Retrospective Studies
• Spinal Fusion/methods
• Titanium

Cortical bone trajectory (CBT) for posterior fixation with pedicle screws is considered a relatively new alternative trajectory that travels in the medio-lateral direction in the transverse plane and in the caudo-cephalad path in the sagittal plane. Various biomechanical studies have already validated its superior pullout strength and mechanical stability over the traditional trajectory of convergent pedicle screws. Due to the relatively medial starting point of this trajectory, the CBT also poses the clinical advantage of requiring a smaller surgical field of exposure, thus minimizing tissue and muscle injury while reducing operative time and intraoperative blood loss. The evolution of CBT through time has closely been linked to the unwavering philosophy of prioritizing patient outcomes, advancements in neuronavigational technology, and the mounting biomechanical, morphometric, and clinical evidence. In this historical review, we provide a unique perspective on how CBT surgical technique has developed through time, highlighting key milestones and attempting to explain its explosive rise in popularity.

• bone fusion
• cortical bone trajectory
• degenerative
• long trajectory
• posterior lumbar interbody fusion
• screw insertion depth

• Cortical bone trajectory screw technique
• Polyetheretherketone cage
• Posterior lumbar interbody fusion
• Titanium-coated polyetheretherketone cage
• Traditional trajectory pedicle screw technique

Purpose: This study aims to elucidate the radiological outcome after Cortical bone trajectory (CBT) screw fixation and whether dual-threaded (DT) screws should be used in the fusion surgery. Methods: 159 patients with degenerative lumbar disorder who had undergone midline lumbar inter-body fusion surgery by CBT screw-fixation technique (2014 to 2018). Patient subgroups were based on single-threaded (ST) or DT screw, fixation length, as well as whether fixation involved to sacrum level (S1). Serial dynamic plain films were reviewed and an appearance of a halo phenomenon between screw–bone interfaces was identified as a case of screw loosening. Results: 29 patients (39.7%) in ST group and 10 patients (11.6%) in DT group demonstrated a halo phenomenon (p < 0.0001 ****). After subgrouping with fixation length, the incidence rates of a halo phenomenon in each group were 11.1%:3% (ST-1L vs. DT-1L), 37%:13.8% (ST-2L vs. DT-2L), and 84.2%:23.5% (ST-3L vs. DT-3L). Among the 85 patients with a fixation involved in S1, 26 patients (52%) with single-threaded screw (STS group) and 8 patients (22.8%) with dual-threaded screw (DTS group) demonstrated a halo appearance (p = 0.0078 **). After subgrouping the fixation level, the incidence of a halo appearance in each group was 25%:0% (STS-1L vs. DTS-1L), 40.9%:26.3% (STS-2L vs. DTS-2L), and 87.5%: 30% (STS-3L vs. DTS-3L). Conclusion: Both fixation length and whether fixation involved to S1 contribute to the incidence of screw loosening, the data supports clinical evidence that DT screws had greater fixation strength with an increased fixative stability and lower incidence of screw loosening in CBT screw fixation compared with ST screws. Level of evidence: 2.

• cortical bone trajectory
• fixation length
• midline lumbar inter-body fusion
• screws loosening
• screws thread

• PEEK
• adjacent-segment degeneration
• adjacent-segment disease
• axial rotation
• cortical screw
• degenerative
• extension
• flexion
• lateral bending
• lateral lumbar interbody fusion
• pedicle screw
• transforaminal lumbar interbody fusion

Midline lumbar interbody fusion is performed for treatment of various lumbar degenerative diseases, with good clinical outcomes and few complications. However, there are no large-scale or long-term studies regarding midline lumbar interbody fusion. Therefore, the purpose of this study was to evaluate the clinical results of midline lumbar interbody fusion and to compare the results according to surgical level.

Between January 2013 and December 2015, 200 patients with lumbar degenerative disease undergoing midline lumbar interbody fusion surgery were enrolled. The mean patient age was 69.9 ± 15.8 years (range, 40–85 years). The patients were divided into groups according to surgical level: (1) level 1 operation (136 patients), (2) level 2 operation (43 patients), (3) level 3 operation (12 patients), and (4) level 4 or higher (9 patients). Clinical outcomes, fusion rates, and complications were compared among the 4 groups.

All clinical outcomes significantly improved after surgery (measured at 3 years postoperatively) in all groups. Mean fusion rate was 90.5% ± 5.21%. Fusion rate was highest in group I (95.8%) and lowest in group IV (85.2%). There were complications in 17 cases (8.5%). Adjacent segment disease occurred in 16 cases, 5 of which required surgery. Group 1 had 1 case, and group 4 had 4 cases. Screw loosening occurred in 1 case in group 4. There were no cases of infection or mechanical complications.

This large, single‐institution, retrospective study demonstrates favorable clinical outcomes after midline lumbar interbody fusion for lumbar degenerative disease regardless of surgical level.

• Clinical outcome
• Cortical bone trajectory screw technique
• Fusion rate
• Lumbar spinal stenosis
• Posterior lumbar interbody fusion

The cortical bone trajectory (CBT) has been introduced with the aim of better screw hold, however, screw-rod constructs with this trajectory might provide less rigidity in lateral bending (LB) and axial rotation (AR) compared to the constructs with the traditional trajectory (TT). Therefore, the addition of a horizontal cross-connector could be beneficial in counteracting this possible inferiority. The aim of this study was to compare the primary rigidity of TT with CBT screw-rod constructs and to quantify the effect of cross-connector-augmentation in both. Spines of four human cadavers (T9 –L5) were cropped into 15 functional spine units (FSU). Eight FSUs were instrumented with TT and seven FSUs with CBT pedicle screws. The segments were tested in six loading directions in three configurations: uninstrumented, instrumented with and without cross-connector. The motion between the cranial and caudal vertebra was recorded. The range of motion (ROM) between the CBT and the TT group did not differ significantly in either configuration. Cross-connector -augmentation did reduce the ROM in AR (16.3%, 0.27°, p = 0.02), LB (2.9%, 0.07°, p = 0.03) and flexion-extension FE (2.3%, 0.04°, p = 0.02) for the TT group and in AR (20.6%, 0.31°, p = 0.01) for the CBT-group. The primary rigidity of TT and CBT single level screw-rod constructs did not show significant difference. The minimal reduction of ROM due to cross-connector-augmentation seems clinically not relevant. Based on the findings of these study there is no increased necessity to use a cross-connector in a CBT-construct.

• Biomechanical Phenomena
• Cadaver
• Cortical Bone/surgery
• Female
• Humans
• Male
• Middle Aged
• Pedicle Screws
• Range of Motion, Articular
• Spine/surgery

• Medacta International (Castel San Peitro, Switzerland) (Instruments used were funded)

• Cortical bone trajectory
• Cortical screw
• Lumbar fusion
• Pedicle screw
• Pedicle screws

• biomechanics
• consensus
• controversy
• in vitro
• mechanical testing
• methodology
• spine

• National Science Foundation

• cbt screw
• digital technology
• ideal trajectory
• lumbar vertebra

• Computer Simulation
• Cortical Bone/diagnostic imaging
• Cortical Bone/injuries
• Cortical Bone/surgery
• Fracture Fixation/instrumentation
• Humans
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/injuries
• Lumbar Vertebrae/surgery
• Models, Anatomic
• Pedicle Screws
• Spinal Fractures/diagnostic imaging
• Spinal Fractures/surgery
• Tomography, X-Ray Computed
• Zygapophyseal Joint/diagnostic imaging
• Zygapophyseal Joint/surgery

• Biomechanics
• Cortical screw
• Laminectomy
• Minimally invasive surgery
• Pedicle screw
• Posterior fixation
• Screw pullout

• C2
• Cortical screw
• High cervical spine surgery
• High riding vertebral artery
• Screw fixation

• Aged
• Bone Screws
• Cervical Vertebrae/diagnostic imaging
• Cervical Vertebrae/surgery
• Cortical Bone/diagnostic imaging
• Cortical Bone/surgery
• Female
• Humans
• Internal Fixators
• Male
• Middle Aged
• Spinal Cord Diseases/diagnostic imaging
• Spinal Cord Diseases/surgery
• Spinal Fractures/diagnostic imaging
• Spinal Fractures/surgery
• Spinal Fusion/instrumentation
• Spinal Fusion/methods

• 3D printed guide
• Cortical bone trajectory
• Cortical pedicle screws
• Minimally invasive surgery
• Planning
• Posterior lumbar fusion

• Length of stay
• Operative time
• Spinal stenosis
• Spondylolisthesis
• Surgical blood loss