Development and Kinematic Verification of a Finite Element Model for the Lumbar Spine: Application to Disc Degeneration

Abstract

The knowledge of the lumbar spine biomechanics is essential for clinical applications. Due to the difficulties to experiment on living people and the irregular results published, simulation based on finite elements (FE) has been developed, making it possible to adequately reproduce the biomechanics of the lumbar spine. A 3D FE model of the complete lumbar spine (vertebrae, discs, and ligaments) has been developed. To verify the model, radiological images (X-rays) were taken over a group of 25 healthy, male individuals with average age of 27.4 and average weight of 78.6 kg with the corresponding informed consent. A maximum angle of 34.40° is achieved in flexion and of 35.58° in extension with a flexion-extension angle of 69.98°. The radiological measurements were 33.94 ± 4.91°, 38.73 ± 4.29°, and 72.67°, respectively. In lateral bending, the maximum angles were 19.33° and 23.40 ± 2.39, respectively. In rotation a maximum angle of 9.96° was obtained. The model incorporates a precise geometrical characterization of several elements (vertebrae, discs, and ligaments), respecting anatomical features and being capable of reproducing a wide range of physiological movements. Application to disc degeneration (L5-S1) allows predicting the affection in the mobility of the different lumbar segments, by means of parametric studies for different ranges of degeneration.

A forward dynamics simulation of human lumbar spine flexion predicting the load sharing of intervertebral discs, ligaments, and muscles

“…The simulation results that were presented in this study showed an increase in angular displacement during flexion in the order L1/2 (2.6 • ) → L2/3 (3.6 • ) → L3/4 (4.4 • ) → L4/5 (4.6 • ). This caudocranial increase in angular IVD joint motion is in accordance with flexion-extension studies by Hayes et al (1989), Ibarz et al (2013), Pearcy and Portek (1984), White and Panjabi (1990): L1/2 (5 − 16 • ) → L2/3 (7.8 − 18 • ) → L3/4 (6 − 17 • ) → L4/5 (9 − 21 • ). Again, only relative changes could be presented (see Fig.…”

“…some present increasing angular motion from cranial to caudal (Hayes et al 1989;Ibarz et al 2013;Pearcy and Portek 1984;White and Panjabi 1990) while others present the opposite (Lee et al 2002;Li et al 2009;Wong et al 2004Wong et al , 2006. The simulation results that were presented in this study showed an increase in angular displacement during flexion in the order L1/2 (2.6 • ) → L2/3 (3.6 • ) → L3/4 (4.4 • ) → L4/5 (4.6 • ).…”

“…13 Angular displacements in the lumbar joints, w.r.t local joint coordinate system, increase from cranial to caudal. In vitro studies (Hayes et al 1989;Ibarz et al 2013;Pearcy and Portek 1984;White and Panjabi 1990) report displacements in the same order; however, they measured flexion-extension movements of higher amplitudes. Note, we did not include studies (Lee et al 2002;Li et al 2009;Wong et al 2004Wong et al , 2006 with the opposite trend in this figure.…”

“…Several studies found in the literature report on full spinal motion or local spine kinematics, cf. Hayes et al (1989), Ibarz et al (2013), Pearcy and Portek (1984), White and Panjabi (1990). Some studies have combined global spine kinematic data with local IVD force data, cf.…”

“…Ibarz et al (2013) Fig. 12 Vertical displacements in the lumbar joints, w.r.t local joint coordinate system, increase from cranial to caudal.…”