Biomedical Engineering Reference
In-Depth Information
studies have associated some occupational conditions with low back pain symptoms, such as
physically heavy work, static work postures, repetitive work, exposure to vibration, and so on
(Shirazi-Adl and Parnianpour 2001).
Epidemiological investigations have suggested that WBV contributes significantly to injuries
and functional disorders of the skeleton and joints (Frymoyer et al. 1980). Long-term WBV has
been found to pose health risks for the lumbar spine, especially for the lower lumbar motion seg-
ment L3-L5 (Frymoyer et al. 1980; Pankoke, Hofmann, and Wolfel 2001; Cheung, Zhang, and
Chow 2003). It has also been shown that dynamic loads pose a greater risk and could induce a
twofold (Kasra, Shirazi-Adl, and Drouin 1992; Keller, Colloca, and Beliveau 2002) and threefold
(Lee, Esler, and Midren 1993) increase in stress, strain, and joint force in comparison with static
conditions. Many studies have explored the link between lower back pain and WBV in special
working populations (Fairley 1995; Chen, Chang, and Shih 2003; Cann, Salmoni, and Eger 2004).
Accumulated loads were found to be risk factors for occupational lower back pain during prolonged
dynamic asymmetric tasks (Mientjes et al. 1999; Kumar 2001).
In view of the harmfulness of vibration to the human body, many studies have reported on the
problem of WBV (Pope and Novotny 1993; Goel, Park, and Kong 1994; Pankoke, Hofmann, and
Wolfel 2001; Kong and Goel 2003; Guo and Teo 2005) to provide insights into spinal injury and
degeneration and to investigate therapeutic methods for the treatment of diseases of the human
spine. Pankoke, Hofmann, and Wolfel (2001) built a nonlinear FE reduced model of a seated man
with considerations for body stature, body mass, and postures for investigating WBV. Guo and
Teo (2005) developed a detailed FE model of the spine T12-Pelvis segment, obtained the resonant
frequencies of different spinal segments, and also predicted the dynamic trend of the spine T12-
Pelvis segment in the sagittal plane under WBV. Kong and Goel (2003) built a head-to-sacrum FE
model to predict the frequency response properties of the human upper body. Goel, Park, and Kong
(1994) developed a three-dimensional FE model of the ligamentous L4-S1 segment with an upper-
body mass of 40 kg and analyzed the dynamic response of the spine under loading with different
frequencies.
Considering injury or degeneration of the human spine, the effects of loss of intradiscal pres-
sure have been analyzed under static conditions using FE analysis (Kim et al. 1991; Goto et al.
2002) and experimental studies (Frei et al. 2001). In addition, Goel and Kim (1989) predicted that
total denucleation might induce laminae separation of intervertebral discs. Shirazi-Adl and col-
leagues (Shirazi-Adl, Shrivastava, and Ahmed 1984; Shirazi-Adl and Drouin 1987) demonstrated
that degenerated discs caused high loads to be distributed around the edges of the disc. Sharma,
Langrana, and Rodriguez (1995, 1998) investigated the roles of facets and ligaments in spinal stabil-
ity by addressing the facet load transmission. Goto et al. (2002), using FE methods, also indicated
that decreased intradiscal pressure might increase the burden on facet joints and cause deformation
of these joints, and concluded that disc degeneration occurs before facet joint osteoarthritis (Adams
and Hutton 1980; Butler et al. 1990).
This chapter introduces FE modeling, model validation, modal analysis, response analysis, and
material sensitivity analysis of the human spine, which can be used to further understand the biody-
namic characteristics of the human spine and provide a reference for the prevention and treatment
of WBV-related spine diseases.
15.2 FInIte element modelIng oF the human SPIne
A detailed and validated FE model of the human spine is a key prerequisite for analyzing the
mechanical characteristics of the spine. To date, the spine has been modeled numerous times for dif-
ferent motion segments, such as the cervical spine, thoracic spine, and lumbar spine. In this study, a
detailed ligamentous FE model of the spinal segment T12-Pelvis is developed and used to analyze
biomechanical characteristics of the spine, including static and dynamic characteristics, as well as
material property sensitivity and spinal injuries.
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