Investigation On The Effect Of Human Body Weight On Biomechanical Behaviour Of Facet Joints Using Finite Element Analysis

Lee, Khar Chun (2019) Investigation On The Effect Of Human Body Weight On Biomechanical Behaviour Of Facet Joints Using Finite Element Analysis. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

Obesity is a globally increasing health problem which normally would associate with various kind of diseases such as hypertension, osteoarthritis (OA) and degeneration of soft tissues especially facet joints and intervertebral disc. It is proven that obesity is one of the key contributions that cause low back pain where excessive loading due to obese would change the mechanical behaviour of lumbar spine. The spinal facet joints which serve as one of the load bearers are highly exposed to the risk of joint damage and degeneration when subjected to high mechanical compressive load. Since the concern in studies of facet joints under mechanical compressive load is only given attention in recent years due to difficulties in retrieving its geometrical data and contact pressure. Hence, there is a need to carry out analysis on facet joints especially the effects of human weight on the spinal facet joint. Finite element analysis (FEA) is one of the most suitable method in the study of facet joint since FEA allows repeated simulation which greatly reduce the time consumed and expenditures without compromising the reliability of the results. The main objectives of this study were to improve and verify the FE lumbar spine model and investigate the effects of human weight on the biomechanical behaviour of facet joints through finite element analysis. The ligaments were modelled into the FE lumbar spine model and verified by comparing the intersegmental rotation of the FE lumbar spine model under pure moment of 7.5 Nm in flexion and extension with previous in vitro study. The verified FE model was then subjected to compressive follower load of 700 N, 900 N and 1300, which represented the normal weight, overweight and obese weight to investigate the effect of human weight on the kinematics of lumbar spine, stress at capsular ligament and facet contact pressure. The results shown that as compressive load increased, the range of motion for lumbar spine under flexion-extension motion will decrease up to 12%. Besides, it was shown that the stress at capsular ligament and facet contact pressure would increase with increasing compressive load. Under obese weight, the stress at capsular ligament has increased up to 66.75% while facet contact pressure has maximum increment of 19.24% at left superior facets of L3-L4 vertebrae. Therefore, an increase in body weight can change the kinematics lumbar spine and causes an increase in stress at capsular ligament and facet contact pressure. This could be a factor that lead to muscular dystrophy, degeneration of facet joints and osteoarthritis, which are the potential risks for low back pain and chronic low back pain.

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