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Motion analysis of lumbar vertebrae for different rod materials and flexible rod device – An experimental and finite element study

Rana Masud, Biswas Jayanta Kumar, Roy Sandipan, Biswas Palash, Karmakar Santanu Kumar, Roychowdhury Amit

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 1

415--425

EN

Different stabilization devices have been used for treating lumbar spine disorders, including fusion, dynamic stabilization devices, flexible rods etc., which possess a different level of limitations. A simple experimental procedure is developed using a prototype lumbar spine specimen (L1-S), to evaluate the biomechanical performance of the lumbar spine. The range of motions (ROM) are tested for pedicle screw made of stainless steel (SS) fixation, using Teflon rod, ultra high molecular weight poly ethylene (UHMWPE) rod, poly ether ether ketone (PEEK) rod and SS flexible rod device (FRD). SS pedicle screw is used for fixation on the prototype lumbar spine. Experimental results are validated and compared with finite element (FE) results. It is observed that, in both flexion and extension, reduction in ROM is higher for Teflon and UHMWPE as compared to PEEK and FRD system. Differences between experimental and numerical results are found to be within an acceptable limit of 5–11%. For flexibility study, both numerical and experimental results support that PEEK rod plays an effective and important role among all the semi-rigid rods. The FRD devices are found to preserve the flexibility of the segment considerably better than PEEK rod.

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Design factors of lumbar pedicle screws under bending load: A finite element analysis

Biswas Jayanta Kumar, Sahu Tikeshwar Prasad, Rana Masud, Roy Sandipan, Karmakar Santanu Kumar, Majumder Santanu, Roychowdhury Amit

Biocybernetics and Biomedical Engineering

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2019

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Vol. 39, no. 1

52--62

EN

Loosening and breakage of lumbar pedicle screw are the most common complications affecting the spinal stability. The design factors of the pedicle screw that may affect the fixation strength under bending load are pitch length, major diameter, thread profiles and geometry. In this study, 84 finite element (FE) models of the pedicle screw were generated having 7 pitch lengths, 3 major diameters, 2 thread profiles and 2 geometries. The assembly of pedicle screw and CT scan based half section FE model of 4th lumbar vertebra was loaded with a 200 N force on the screw head which is equivalent to a bending moment of 11 Nm. With triangular thread profile and cylindrical geometry, for 300% increase in pitch length (1–4 mm), von Mises stress in screw and von Mises strain in bone increased by 65% and 117% respectively, for a 26% decrease in major diameter (7.6 mm to 5.6 mm) and correlations were proposed among screw stress (r2 = 0.992) or bone strain (r2 = 0.986), pitch length and major diameter. Similar correlations were also proposed for trapezoidal thread profile and tapered geometry (r2 = 0.994 for screw stress and r2 = 0.986 for bone strain). Hence, a combination of tapered pedicle screw with lower pitch length, higher diameter and trapezoidal thread profile may serve better under bending load for lumbar vertebral implant.

3

Zastosowanie metod inżynierii odwrotnej do projektowania sztucznego krążka międzykręgowego

Mańko M., Zubrzycki J., Karpiński R.

Journal of Technology and Exploitation in Mechanical Engineering

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2015

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Vol. 1, nr 1-2

33--58

PL

W pracy przedstawiono budowę anatomiczną kręgu i krążka międzykręgowego. Opisano funkcjonowanie kręgosłupa, jego kinematykę oraz oddziaływania międzykręgowe. Stworzono pełny trójwymiarowy model kręgów lędźwiowych L2 – L4. Na ich podstawie skonstruowano model endoprotezy krążka międzykręgowego (pomiędzy L2 i L3). Opracowano uproszczony model sztucznego krążka międzykręgowego sformułowany metodą elementów skończonych, który posłużył do analizy biomechanicznej. Dokonano obliczeń wytrzymałościowych oraz wyciągnięto odpowiednie wnioski. Prezentowane wyniki przedstawiają zachowanie się trójwymiarowego modelu kręgu lędźwiowego przy zastosowaniu endoprotezy krążka międzykręgowego pod wpływem działania obciążeń.

EN

In the hereby thesis the anatomy of the lumbar vertebra and intervertebral disc were presented. Functioning and kinematics of the spine and intervertebral forces were described.Full three – dimensional model of the lumbar vertebrae L2 – L4 was created. On the basis of it model of artificial intervertebral disc was constructed (between L2 and L3). The simplified model of vertebra L2 was formulated via finite elements method. Processed model has been used for biomechanical analysis.Strength calculations were made and appropriate conclusions were drawn. Presented results show behavior influenced of three – dimensional model of the lumbar vertebra with artificial intervertebral disc by operation of loads.