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Journal of Long-Term Effects of Medical Implants

ISSN Print: 1050-6934
ISSN Online: 1940-4379

Journal of Long-Term Effects of Medical Implants

DOI: 10.1615/JLongTermEffMedImplants.2014006264
pages 99-108

Optimization of Spinal Implant Screw for Lower Vertebra through Finite Element Studies

Jayanta Kumar Biswas
Indian Institute of Engineering Science and Technology
Santanu Karmakar
Department Mechanical Engineering, Bengal Engineering & Science University, Shibpur, Howrah, India
Santanu Majumder
Department of Aerospace Engineering & Applied Mechanics, Bengal Engineering & Science University, Shibpur, Howrah, India
Partha Sarathi Banerjee
Central Mechanical Engineering Research Institute, Durgapur
Subrata Saha
Department of Biomedical Engineering, Florida International University, Miami, FL 33174; Affiliated Professor, Department of Restorative Dentistry, Affiliated Faculty, Department of Oral & Maxillofacial Surgery, School of Dentistry, University of Washington, Seattle, WA 98195
Amit Roy Chowdhury
Department of Orthopaedic Surgery and Rehabilitation Medicine, SUNY Downstate Medical Center, USA; Department of Aerospace Engineering and Applied Mechanics, Bengal Engineering and Science University, India


The increasing older population is suffering from an increase in age-related spinal degeneration that causes tremendous pain. Spine injury is mostly indicated at the lumbar spine (L3−L5) and corresponding intervertebral disks. Finite element analysis (FEA) is now one of the most efficient and accepted tools used to simulate these pathological conditions in computer-assisted design (CAD) models. In this study, L3−L5 spines were modeled, and FEA was performed to formulate optimal remedial measures. Three different loads (420, 490.5, and 588.6 N) based on three body weights (70, 90, and 120 kg) were applied at the top surface of the L3 vertebra, while the lower surface of the L5 vertebra remained fixed. Models of implants using stainless steel and titanium alloy (Ti6Al4V) pedicle screws and rods with three different diameters (4, 5, and 6 mm) were inserted into the spine models. The relative strengths of bone (very weak, weak, standard, strong, and very strong) were considered to determine the patient-specific effect. A total of 90 models were simulated, and von Mises stress and strain, shear stress, and strain intensity contour at the bone-implant interface were analyzed. Results of these analyses indicate that the 6-mm pedicle screw diameter is optimal for most cases. Experimental and clinical validation are needed to confirm these theoretical results.