Optimized the stress shielding reduction of different lattice structures in cervical spine implants using FEA and VIKOR fuzzy MCDM analysis Jegan Jayakumar, Pechimuthu Susai Manickam, Goldina Ghosh, S. Balamurugan, Bedanka Ray, Sandipan Roy Mechanics of Advanced Materials and Structures, 2026 The difference in material properties between bone and implants might cause the bone surrounding the implant to weaken as a result of stress shielding, which prevents the required stress for bone remodeling. Integrating lattice structures into implants is an effective method to reduce the negative effects of stress shielding. This study investigates the characteristics of three lattice structures (Diamond, Gyroid, and Primitive) with different levels of porosity ranging from 25% to 95%. The lattice structures are standardized for representation, and finite element analysis is performed on the C5–C6 segment of the cervical spine using the implant model. The VIKOR Fuzzy Multi Decision Making technique is used to maximize stress levels in the interbody fusion cage and identify the best appropriate lattice structure. The findings suggest that Diamond and Gyroid structures exhibit superior performance compared to the Primitive lattice, with an ideal porosity range of 5% for cage implants.
Finite Element Analysis Comparing the Biomechanical Parameters in Multilevel Posterior Cervical Instrumentation Model Involving Lateral Mass Screw versus Transpedicular Screw Fixation at the C7 Vertebra Arvind Gopalrao Kulkarni, Priyambada Kumar, Gautam Manjayya Shetty, Sandipan Roy, Pechimuthu Susai Manickam, Raja Dhason, Aditya Raghavendra Sai Siva Chadalavada, Yogesh Madhavrao Adbalwad Asian Spine Journal, 2024 Study Design: Basic research.Purpose: This finite element (FE) analysis (FEA) aimed to compare the biomechanical parameters in multilevel posterior cervical fixation with the C7 vertebra instrumented by two techniques: lateral mass screw (LMS) vs. transpedicular screw (TPS).Overview of Literature: Very few studies have compared the biomechanics of different multilevel posterior cervical fixation constructs.Methods: Four FE models of multilevel posterior cervical fixation were created and tested by FEA in various permutations and combinations. Generic differences in fixation were determined, and the following parameters were assessed: (1) maximum moment at failure, (2) maximum angulation at failure, (3) maximum stress at failure, (4) point of failure, (5) intervertebral disc stress, and (6) influence of adding a C2 pars screw to the multilevel construct.Results: The maximum moment at failure was higher in the LMS fixation group than in the TPS group. The maximum angulation in flexion allowed by LMS was higher than that by TPS. The maximum strain at failure was higher in the LMS group than in the TPS group. The maximum stress endured before failure was higher in the TPS group than in the LMS group. Intervertebral stress levels at C6–C7 and C7–T1 intervertebral discs were higher in the LMS group than in the TPS group. For both models where C2 fixation was performed, lower von Mises stress was recorded at the C2–C3 intervertebral disc level.Conclusions: Ending a multilevel posterior cervical fixation construct with TPS fixation rather than LMS fixation at the C7 vertebra provides a stiff and more constrained construct system, with higher stress endurance to compressive force. The constraint and durability of the construct can be further enhanced by adding a C2 pars screw in the fixation system.
Biomechanical analysis of the novel S-type dynamic cage by implementation of teaching learning based optimization algorithm - An experimental and finite element study Pechimuthu Susai Manickam, Goldina Ghosh, Gautam M. Shetty, Amit Roy Chowdhury, Sandipan Roy Medical Engineering and Physics, 2023 Anterior Cervical Discectomy and Fusion (ACDF) is the most popular and effective procedure for patients with intervertebral disc degeneration, where the degenerated disc is replaced with an interbody implant (widely known as cage). The design of the cage plays a vital role since it has to provide stability for the anterior cervical column without any side-effects. We designed a novel S-type dynamic cage for C4-C5 level, using Polyetheretherketone (PEEK) material considering four different shapes namely: square, circle, rectangle and elliptical, for the central window to occupy bone graft. The major design constrain for a successful cage is minimized cage stress, in order to avoid subsidence. Finite Element (FE) analysis results revealed that the cage stress values obtained during the physiological motion varied depending upon the shape of the central window provided for bone graft. The objective of this study is to optimize the central window shape using the Teaching Learning Based Optimization (TLBO) algorithm. It was found that square and elliptical shape bone graft cavity resulted in better outcomes. Additional experimental study was also conducted with a six-axis spine simulator. Based on the optimization results, we manufactured two PEEK cage models with square and elliptical shaped central window using additive manufacturing. A prototype model of the C4-C5 level made of Polyvinylchloride (PVC) was used for experiment due to the existing constraints for using a cadaveric model. The experimental results were cross-verified using FE analysis. Thus, we would like to conclude that square and elliptical shape of the central window were the better design factor for our novel dynamic cage.
The biomechanical study of cervical spine: A Finite Element Analysis Pechimuthu Susai Manickam, Sandipan Roy International Journal of Artificial Organs, 2022 The biomechanical study helps us to understand the mechanics of the human cervical spine. A three dimensional Finite Element (FE) model for C3 to C6 level was developed using computed tomography (CT) scan data to study the mechanical behaviour of the cervical spine. A moment of 1 Nm was applied at the top of C3 vertebral end plate and all degrees of freedom of bottom end plate of C6 were constrained. The physiological motion of the cervical spine was validated using published experimental and FE analysis results. The von Mises stress distribution across the intervertebral disc was calculated along with range of motion. It was observed that the predicted results of functional spine units using FE analysis replicate the real behaviour of the cervical spine.
OPTIMIZATION OF BONE GRAFT SHAPES OF S-TYPE CERVICAL CAGE THROUGH GENETIC ALGORITHM Pechimuthu Susai Manickam, Goldina Ghosh, Sandipan Roy International Journal for Multiscale Computational Engineering, 2022 The fourth and fifth cervical vertebrae are the common sites of injury and disc degeneration. The interbody fusion failure was observed after fusion surgery. The postoperative effects are subsidence, migration, and nonfusion of the implants due to the improper cage design. Finite element analysis is the most efficient tool to simulate the surgical condition using computer-aided design models. In this study, we designed an S-type dynamic cage with a different geometry of bone graft. The objective of our study is to reduce the stresses in the dynamic cage, so the risk of subsidence is controlled and optimized for the best suitable shape. The different geometry of a bone graft designed for the dynamic cage are square, circular, rectangular, and elliptical. In this study, the bone grafts producing higher stress need to be selected for the cage design. A three-dimensional finite element model form C3-C6 was developed, and in the C4-C5 level, the S-type dynamic cage with the bone graft was virtually inserted. The S-type dynamic cage with the elliptical graft exhibited a lower stress in the cage and higher stress in the bone graft. The optimized cage with the graft reduces the risk of subsidence and increases osteointegration so the fusion can be achieved. Keeping this in mind, the genetic algorithm is used for optimizing the stress level and assigning a correct material and shape for the cage and bone graft for a particular patient.
A biomechanical comparative study of cervical spine finite element model using hexahedral mesh and tetrahedral mesh Pechimuthu Susai Manickam, Sandipan Roy Aip Conference Proceedings, 2021 The human cervical spine is a unique structure which connects the cranium and the thoracic region. The intervertebral disc serves as a weight bearing, supports the body and allows the relative motion between the vertebrae. The objective of this work is to compare the influence of hexahedral mesh vs tetrahedral mesh in cervical spine and its effect to measure the biomechanical stresses and its motion at different motion segments. The model was meshed using linear hexahedral mesh and linear tetrahedral mesh. A compressive load of 50 N preload and a moment of 1 Nm is applied at the C3 vertebrae and at the C6 vertebra bottom is fixed in all the directions. The models were used to study the physiological range of motion of the cervical spine. Flexion, extension, lateral bending and axial rotation were simulated. The physiological range of motion and the intervertebral disc stress distribution is studied and compared with the existing in vitro and in silico studies. In this model it was observed that the linear hexahedral and the linear tetrahedral models surrogate the physiological motion. We found the results of the two different meshes were validated with the existing in vitro and in silico studies. The main finding of this work is both hexahedral and tetrahedral mesh have the capability to replicate the natural phenomenon. In this we conclude the tetrahedral mesh is easy to generate and the irregular anatomy of the cervical spine can be modelled and analysed.
The biomechanical effects of S-type dynamic cage using Ti and PEEK for ACDF surgery on cervical spine varying loads Pechimuthu Susai Manickam, Sandipan Roy International Journal of Artificial Organs, 2021 Anterior cervical discectomy with fusion (ACDF) is the common method to treat the cervical disc degeneration. The most serious problems in the fusion cages are adjacent disc degeneration, loss of lordosis, pain, subsidence, and migration of the cage. The objective of our work is to develop the three-dimensional finite element (FE) model from C3-C6 and virtually implant a designed S-type dynamic cage at C4-C5 segment of the model. The dynamic cage design will provide mobility in the early stage after ACDF surgery. Titanium (Ti) and PEEK (polyether ether ketone) were used as the material property for the cages. We applied the physiological motions at different loads from 0.5, 1, 1.5, 2.0 Nm to evaluate the dynamic cage design and the biomechanical performances of the designed S-type dynamic cage. It was observed that in all the loading condition the range of motion in the adjacent level was maintained and the maximum stress at the adjacent disc was reduced. The clinical significance of the S-type dynamic cage is better stress profile at the fusion level and adjacent segments which translates into higher rate of fusion, lower risk of cage subsidence, lower risk of adjacent segment degeneration, and good mechanical stability.
