Biomechanical comparison of the K-ROD and Dynesys dynamic spinal fixator systems – A finite element analysis

Lin, Hsiu‐Mei; Pan, Yung Ning; Liu, Chien Lin; Huang, Li; Huang, Chang Hung; Chen, Chen Sheng

doi:10.3233/bme-130766

Cited by 17 publications

(16 citation statements)

References 29 publications

(40 reference statements)

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“…Screw lengths were 45 mm. The thread on the pedicle screws was underestimated [29][30][31][32] to reduce the computational weight of the models. The 'tie' constraint was created between the pedicle screws and the vertebraes to be permanently bonded together by full constraint.…”

Section: Fe Model Creationmentioning

confidence: 99%

Finite element modelling of hybrid stabilization systems for the human lumbar spine

Eylul

Éltes

Castro

et al. 2020

Proc Inst Mech Eng H

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Intersomatic fusion is a very popular treatment for spinal diseases associated with intervertebral disc degeneration. The effects of three different hybrid stabilization systems on both range of motion and intradiscal pressure were investigated, as there is no consensus in the literature about the efficiency of these systems. Finite element simulations were designed to predict the variations of range of motion and intradiscal pressure from intact to implanted situations. After hybrid stabilization system implantation, L4-L5 level did not lose its motion completely, while L5-S1 had no mobility as a consequence of disc removal and fusion process. BalanC hybrid stabilization system represented higher mobility at the index level, reduced intradiscal pressure of adjacent level, but caused to increment in range of motion by 20% under axial rotation. Higher tendency by 93% to the failure was also detected under axial rotation. Dynesys hybrid stabilization system represented more restricted motion than BalanC, and negligible effects to the adjacent level. B-DYN hybrid stabilization system was the most rigid one among all three systems. It reduced intradiscal pressure and range of motion at the adjacent level except from motion under axial rotation being increased by 13%. Fracture risk of B-DYN and Dynesys Transition Optima components was low when compared with BalanC. Mobility of the adjacent level around axial direction should be taken into account in case of implantation with BalanC and B-DYN systems, as well as on the development of new designs. Having these findings in mind, it is clear that hybrid systems need to be further tested, both clinically and numerically, before being considered for common use.

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Section: Fe Model Creationmentioning

confidence: 99%

Finite element modelling of hybrid stabilization systems for the human lumbar spine

Eylul

Éltes

Castro

et al. 2020

Proc Inst Mech Eng H

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“…8 Many in vitro and biomechanical studies have shown that this system can restrain the amount of flexibility through polyethylene terephthalate cords and polycarbonate urethane spacers. 9 10 11 Contrary to PLIF, which may lead to a rigid connection of the operative level, this system is designed to stabilize the operated segment while allowing some mobility, therefore, it may preserve a better of lumbar mobility than PLIF. 12 …”

Section: Introductionmentioning

confidence: 99%

Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases

Yang

Chen

et al. 2014

IJOO

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Background:Decompression and fusion is considered as the ‘gold standard’ for the treatment of degenerative lumbar diseases, however, many disadvantages have been reported in several studies, recently like donor site pain, pseudoarthrosis, nonunion, screw loosening, instrumentation failure, infection, adjacent segment disease (ASDis) and degeneration. Dynamic neutralization system (Dynesys) avoids many of these disadvantages. This system is made up of pedicle screws, polyethylene terephthalate cords, and polycarbonate urethane spacers to stabilize the functional spinal unit and preserve the adjacent motion after surgeries. This was a retrospective cohort study to compare the effect of Dynesys for treating degenerative lumbar diseases with posterior lumbar interbody fusion (PLIF) based on short term followup.Materials and Methods:Seventy five consecutive patients of lumbar degenerative disease operated between October 2010 and November 2012 were studied with a minimum followup of 2 years. Patients were divided into two groups according to the different surgeries. 30 patients underwent decompression and implantation of Dynesys in two levels (n = 29) or three levels (n = 1) and 45 patients underwent PLIF in two levels (n = 39) or three levels (n = 6). Clinical and radiographic outcomes between two groups were reviewed.Results:Thirty patients (male:17, female:13) with a mean age of 55.96 ± 7.68 years were included in Dynesys group and the PLIF group included 45 patients (male:21, female:24) with a mean age of 54.69 ± 3.26 years. The average followup in Dynesys group and PLIF group was 2.22 ± 0.43 year (range 2-3.5 year) and 2.17 ± 0.76 year (range 2-3 year), respectively. Dynesys group showed a shorter operation time (141.06 ± 11.36 min vs. 176.98 ± 6.72 min, P < 0.001) and less intraoperative blood loss (386.76 ± 19.44 ml vs. 430.11 ± 24.72 ml, P < 0.001). For Dynesys group, visual analogue scale (VAS) for back and leg pain improved from 6.87 ± 0.80 to 2.92 ± 0.18 and 6.99 ± 0.81 to 3.25 ± 0.37, (both P < 0.001) and for PLIF, VAS for back and leg pain also improved significantly (6.97 ± 0.84–3.19 ± 0.19 and 7.26 ± 0.76–3.56 ± 0.38, both P < 0.001). Significant improvement was found at final followup in both groups in Oswestry disability index (ODI) score (both P < 0.001). Besides, Dynesys group showed a greater improvement in ODI and VAS back and leg pain scores compared with the PLIF group (P < 0.001, P = 0.009 and P = 0.031, respectively). For radiological, height of the operated level was found increased in both groups (both P < 0.001), but there was no difference between two groups (P = 0.93). For range of motion (ROM) of operated level, significant decrease was found in both groups (P < 0.001), but Dynesys showed a higher preservation of motion at the operative levels (P < 0.001). However, no significant difference was found in the percentage change of ROM of adjacent levels between Dynesys and PLIF (0.74 ± 8.92% vs. 0.92 ± 4.52%, P = 0.91). Some patients suffered from degeneration of adjacent intervertebral dis...

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“…Lin et al 11 performed a comparative FE analysis between two dynamic stabilization Dynesys (DY) and K-ROD (KD) systems based on controlling parameters of flexion, extension, bending, and axial rotation of 12°, 10°, 20° and 8°, respectively. They also focused the disc von Mises stress and Ti Pedicle screw von Mises stress for both systems.…”

Section: Discussionmentioning

confidence: 99%

Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study

et al. 2020

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The aim of this study is to design a novel expanding flexible rod device, for pedicle screw fixation to provide dynamic stability, based on strength and flexibility. Three-dimensional finite-element models of lumbar spine (L1-S) with flexible rod device on L3-L4-L5 levels are developed. The implant material is taken to be Ti-6Al-4V. The models are simulated under different boundary conditions, and the results are compared with intact model. In natural model, total range of motion under 10 Nm moment were found 66.7°, 24.3° and 13.59°, respectively during flexion–extension, lateral bending and axial rotation. The von Mises stress at intact bone was 4 ± 2 MPa and at bone, adjacent to the screw in the implanted bone, was 6 ± 3 MPa. The von Mises stress of disc of intact bone varied from 0.36 to 2.13 MPa while that of the disc between the fixed vertebra of the fixation model reduced by approximately 10% for flexion and 25% for extension compared to intact model. The von Mises stresses of pedicle screw were 120, 135, 110 and 90 MPa during flexion, extension, lateral bending, and axial rotation, respectively. All the stress values were within the safe limit of the material. Using the flexible rod device, flexibility was significantly increased in flexion/extension but not in axial rotation and lateral bending. The results suggest that dynamic stabilization system with respect to fusion is more effective for homogenizing the range of motion of the spine.

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Biomechanical comparison of the K-ROD and Dynesys dynamic spinal fixator systems – A finite element analysis

Cited by 17 publications

References 29 publications

Finite element modelling of hybrid stabilization systems for the human lumbar spine

Finite element modelling of hybrid stabilization systems for the human lumbar spine

Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases

Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study

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