Detailed Modelling of the Lumbar Spine for Investigation of Low Back Pain

Comfort of car seats is becoming an increasingly important issue in the design of vehicles for professional use as well as for personal use. People using cars professionally, like drivers of taxis, trucks, and busses, often have to drive for prolonged periods sometimes leading to physical complaints, like e.g. low back pain. Apart from experimental investigations, virtual testing is becoming more important to get more insight in the problem of low back pain. This paper presents a finite element (FE) model of the lumbar spine (L1-L5). The model contains a detailed geometric description of the lumbar spine and realistic material properties. On a segmental level and as a whole, the model's response was verified for quasi-static and dynamic conditions based on experimental data published in literature. The quasi-static segmental validation comprised of compression, posterior, anterior and lateral shear, flexion and extension, lateral bending and axial torque. Additionally, the frequency-dependent transmissibility behaviour of a motion segment was checked for vertical vibrations. The verification of the whole lumbar spine model's response included flexion, extension, lateral bending and axial torque. The validation shows that the response of the FE lumbar spine model corresponds reasonably with the experimental results. Based on hypotheses in literature regarding low back pain, guidelines are proposed for linking numerical results with the physical phenomenon of low back pain. The numbers of loading cycles to injury is predicted by usage of fatigue models that are based on the calculation of so-called equivalent cyclic stresses.