The Lumbar Spine Model¶
The Lumbar spine contains 5 vertebrae with 3 DoF spherical joints in between, 188 muscle fascicles and a model of intra-abdominal pressure.
Since it is impractical to measure or specify the motions of individual segments within the spine (termed functional spinal units or FSU), these motions are prescribed by default as a function of overall lumbar curvature. These functions are known as kinematic rhythms.
Facet joints are also not employed by default, since most applications do not focus on the lumbar spine
section. However, several examples in
AMMR/Applications folder demonstrate possible mechanisms of
facet joint incorporation and detailed modeling of the lumbar spine.
The spinal muscles do not include the force-length-velocity relations (i.e. we use the so-called simple muscle model). The only input parameter in the muscle model is the cross-sectional area multiplied by a factor. Daggfeldt and Thorstensson (J.Biomech. 2003, 36: 815-825) didn’t include the force-length-velocity relations either.
The inclusion of the lumbar spine ligaments is optional and can be defined as a cumulative stiffness of FSUs or as separate elastic elements. Similarly, the intervertebral disc (IVD) stiffness can be defined as a single cumulative value for a FSU or as linear and nonlinear functions for the disc alone. This, however, is mostly utilized for the spine specific applications, where such a level of detail is important.
In other cases, it has been shown that the torque production from ligaments might not be very important (Cholewicki and McGill, J.Biomech. 1992, 25: 17-28). The data of vertebrae dimensions and whole body parameters is taken from: Nissan and Gilad (J.Biomech. 19: 753-758, 1986) and mechanical properties of ligaments were taken from: Pintar et al. (J.Biomech. 25(11): 1351-1356, 1992).
The spine model contains a preliminary model of the Intra Abdominal pressure (IAP). In short the abdomen is modeled as constant volume, which, when squeezed from the side by the transversus muscles extends the spine by pushing on the rib thorax and the pelvic floor.
From the mathematical point-of-view, this lets the abdominal muscles function as spine extensors, and they become part of the whole recruitment problem. The limit of the IAP was set to 26600 Pa, which was based on measurements on well-trained subjects (Essendrop, M., 2003. Significance of intra-abdominal pressure in work related trunk-loading. Ph.D. Thesis, National Institute of Occupational Health, Denmark.) and using geometric/anatomical estimates of pressure surface area and area centroids, which in turn determines the effective moment arm of the resulting forces.
The lumbar spine model is always part of the AnyBody Human model. The muscles can be enabled/disabled, and the lumbar disc stiffness can be controlled.
#define BM_TRUNK_MUSCLES ON #define BM_TRUNK_DISC_STIFNESS _DISC_STIFFNESS_LINEAR_
The Trunk configuration parameters for a full list of Trunk parameters.
More details on the lumbar spine model can be found online:
Presentation about the Abdominal pressure Presentation
PowerPoint presentation Spine Rhythm Presentation (PDF with videos click to activate them)
You can read more about this lumbar spine model and some preliminary validation in the following article:
de Zee, M., L. Hansen, C. Wong, J. Rasmussen, and E.B. Simonsen. A generic detailed rigid-body lumbar spine model. J.Biomech. 40: 1219-1227, 2007.
Andersson,E., Oddsson,L., Grundstrom,H.,Thorstensson,A., The role of the psoas and iliacus muscles for stability and movement of the lumbar spine, pelvis and hip, Scand. J. Med. Sci. Sports,5 (1995) 10-16.
Bogduk,N., Clinical anatomy of the lumbar spine and sacrum, Churchill Livingstone, Edinburgh, 1997.
Bogduk,N., Macintosh,J.E., Pearcy,M.J., A universal model of the lumbar back muscles in the upright position, Spine, 17 (1992) 897-913.
Bogduk,N., Pearcy,M.J., Hadfield,G., Anatomy and biomechanics of psoas major, Clin. Biomech., 7 (1992) 109-119.
Daggfeldt,K., Thorstensson,A., The role of intraabdominal pressure in spinal unloading, J. Biomech., 30 (1997) 1149-1155.
Daggfeldt,K., Thorstensson,A., The mechanics of back-extensor torque production about the lumbar spine, J. Biomech., 36 (2003) 815-825.
Heylings,D.J.A., Supraspinous and interspinous ligaments of the human lumbar spine, J. Anat., 125 (1978) 127-131.
Hodges,P.W., Cresswell,A.G., Daggfeldt,K., Thorstensson,A., In vivo measurement of the effect of intra-abdominal pressure on the human spine, J. Biomech., 34 (2001) 347-353.
Macintosh,J.E., Bogduk,N., The biomechanics of the lumbar multifidus, Clin. Biomech., 1 (1986) 205-213.
Macintosh,J.E., Bogduk,N., 1987 Volvo award in basic science. The morphology of the lumbar erector spinae, Spine, 12 (1987) 658-668.
Macintosh,J.E., Bogduk,N., The attachments of the lumbar erector spinae, Spine, 16 (1991) 783-792.
Macintosh,J.E., Bogduk,N., Munro,R.R., The morphology of the human lumbar multifidus, Clin. Biomech., 1 (1986) 196-204.
McGill,S.M., Norman,R.W., Effects of an anatomically detailed erector spinae model on L4/L5 disc compression and shear, J. Biomech., 20 (1987) 591-600.
Pearcy,M.J., Bogduk,N., Instantaneous axes of rotation of the lumbar intervertebral joints, Spine, 13 (1988) 1033-1041.
Penning,L., Psoas muscle and lumbar spine stability: a concept uniting existing controversies. Critical review and hypothesis, Eur. Spine J., 9 (2000) 577-585.
Prestar,F.J., Putz,R., Das Ligamentum longitudinale posterius - morphologie und Funktion, Morphol. Med., 2 (1982) 181-189.
Prilutsky,B.I., Zatsiorsky,V.M., Optimizationbased models of muscle coordination, Exerc. Sport Sci. Rev., 30 (2002) 32-38.
Stokes,I.A., Gardner-Morse,M., Lumbar spine maximum efforts and muscle recruitment patterns predicted by a model with multijoint muscles and joints with stiffness, J. Biomech., 28 (1995) 173-186.
Stokes,I.A., Gardner-Morse,M., Quantitative anatomy of the lumbar musculature, J. Biomech., 32 (1999) 311-316.
Pintar et al., “Biomechanical properties of human lumbar spine ligaments”, J Biomech, Vol. 25(11), 1992, pp.1351-1356.