How to reduce stress on the pedicle screws in thoracic spine? importance of screw trajectory: a finite element analysis

Güvenç, Yahya; Akyoldaş, Göktuğ; Şentürk, Salim; Erbulut, Deniz Ufuk; Yaman, Onur; Özer, Ali Fahir

doi:10.5137/1019-5149.jtn.21895-17.2

Cited by 6 publications

(7 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9 Furthermore, the von Mises stress distributions on screws were calculated which ranged from 48.7 to 317.3 MPa in agreement with previous studies. 34,35 The average von Mises stresses for shaft of screws in the level with maximum experienced applied force/moment are listed in Table 6.…”

Section: Resultsmentioning

confidence: 99%

A finite element study on intra-operative corrective forces and evaluation of screw density in scoliosis surgeries

Musapoor

Nikkhoo

Haghpanahi

2018

Proc Inst Mech Eng H

View full text Add to dashboard Cite

Scoliosis is an abnormal sideways curvature of the spine and rib cage, which may need surgical treatments. Most of the corrective maneuvers in scoliosis surgeries are based on surgeon's experience; hence, there is great interest of understanding how the correction ratio can be influenced by the magnitude of forces and moments. Therefore, the objective of this study was to develop and validate a detailed finite element model of the thoracolumbar which can be used to simulate the scoliosis surgeries based on patient-specific clinical images. The validated models of five patients were carefully developed, and the surgery procedures were simulated and the corrective forces were estimated using inverse finite element analysis during the surgery. Furthermore, parametric studies including the influences of the corrective force magnitude and screw density were evaluated. The results showed that the maximum estimated correction force and moment were 173 (655.43) N and 10.67 (62.02) N m, respectively, which were aligned with measured clinical observations. The sensitivity analysis on the magnitude of applied force to the screws showed that correction ratio was slightly increased in level 1 (i.e. F B = 1.3 3 F) but decreased in level 2 (i.e. F B = 1.6 3 F). In addition, the parametric study on increasing the number of pedicle screws showed that there was no significant difference between lower and higher screw density. However, the stress distribution was significantly greater using higher screw density during correction maneuvers. In conclusion, this study shows a direct relationship between the applied force/moment and screw density and the correction ratio up to a border line which should be defined accurately. This detailed computational modeling can be used in clinic in hope of achieving the optimum outcome of scoliosis surgery using individual patient-specific characterization.

show abstract

Section: Resultsmentioning

confidence: 99%

A finite element study on intra-operative corrective forces and evaluation of screw density in scoliosis surgeries

Musapoor

Nikkhoo

Haghpanahi

2018

Proc Inst Mech Eng H

View full text Add to dashboard Cite

show abstract

“…In clinical practice, screw loosening and breakage are common reasons for revision of internal spinal fixation. Reducing the stress on the screws could reduce the risk of screw breakage and loosening 33 , 34 , 35 . Therefore, we also investigated the peak stress in the interbody cage and screw‐bone interface in Models A, B, and C with different implantation regions.…”

Section: Discussionmentioning

confidence: 99%

Effect of the In Situ Screw Implantation Region and Angle on the Stability of Lateral Lumbar Interbody Fusion: A Finite Element Study

Zhu

Fang

et al. 2022

Orthopaedic Surgery

View full text Add to dashboard Cite

Objective: 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.Methods: 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. Results: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.

show abstract

“…For the stress of internal fixation system, flexing, extension, left axial rotating and right axial rotating were the noteworthy working conditions that caused stress concentration. The difference of the pedicle screws’ points and orientations contributed mostly to the difference in stress distribution 39 , 40 . When the different points and orientations were selected, stress distribution of pedicle screws and rods would be changed consequently.…”

Section: Discussionmentioning

confidence: 99%

“…This study result tied well with previous studies wherein the same was observed from all the three different postoperative models. Similarly, the rods connecting two pairs of pedicle screws up and down were under the major stress 39 . In the FE study section, the mean stress values of the three groups (Roy-Camille, Magerl, and Krag) were 80.12 MPa, 92.77 MPa and 66.80 MPa, respectively.…”

Section: Discussionmentioning

confidence: 99%

Stress distribution of different lumbar posterior pedicle screw insertion techniques: a combination study of finite element analysis and biomechanical test

Song

Sun

Zong

et al. 2021

Sci Rep

View full text Add to dashboard Cite

At present, the pedicle screw is the most commonly used internal fixation device. However, there are many kinds of common posterior pedicle screw insertion techniques performed to reconstruct the lumbar stability. Therefore, spinal surgeons often face a difficult choice. The stress distribution of internal fixation system is an important index for evaluating safety. Unfortunately, little had been known about the difference of stress distribution of screw-rod systems that established by Roy-Camille, Magerl and Krag insertion techniques. Here, combination of finite element analysis and model measurement research was adopted to evaluate the difference of stress. Following different pedicle screw insertion techniques, three lumbar posterior surgery models were established after modeling and validation of the L1–S1 vertebrae finite element model. By analyzing the data, we found that stress concentration phenomenon was in all the postoperative models. Roy-Camille and Magerl insertion techniques led to the great stress on screw-rod systems. Then, fresh frozen calf spines were selected as a model for subsequent measurements. Fitted with a specially designed test pedicle screw, L5–L6 vertebrae were selected to repeat and verify the results of the finite element analysis. With the aid of universal testing machine and digital torque wrench, models simulated flexion, extension, lateral bending and rotation. Finally, the strain value was captured by the strain gauge and was then calculated as the stress value. Krag and Magerl were found to be the safer choice for pedicle screw insertion. Overall, our combination method obtained the reliable result that Krag insertion technique was the safer approach for pedicle screw implantation due to its relatively dispersive stress. Therefore, without the consideration of screw size, pedicle fill, bone density, and bone structures, we recommend the Krag insertion technique as the first choice to reconstruction of lumbar stability. Additionally, the combination method of finite element analysis and strain gauge measurement can provide a feasible way to study the stress distribution of spinal internal fixation.

show abstract

How to reduce stress on the pedicle screws in thoracic spine? importance of screw trajectory: a finite element analysis

Abstract: AT decreased the von-Mises stress of the pedicle screws, thereby reducing the rates of screw breakage and fatigue risks. In addition, we believe that AT could protect against screw loosening because the von-Mises stress of the internal fixation was scattered.

Cited by 6 publications

References 12 publications

A finite element study on intra-operative corrective forces and evaluation of screw density in scoliosis surgeries

A finite element study on intra-operative corrective forces and evaluation of screw density in scoliosis surgeries

Effect of the In Situ Screw Implantation Region and Angle on the Stability of Lateral Lumbar Interbody Fusion: A Finite Element Study

Stress distribution of different lumbar posterior pedicle screw insertion techniques: a combination study of finite element analysis and biomechanical test

Contact Info

Product

Resources

About