Why We Are Taller in the Morning than Going to Bed at Night – An in vivo and in vitro Study

Intradiscal and intervertebral pressure transducers were developed. They were used to map the pressures in the nucleus and within the annulus of the human spinal segments. Their stressrelaxation were recorded over a period of time for nucleus pressure, applied load, and peripherial strain against time. The results show that for normal discs, pressures in the nucleus are viscoelastic in nature with the applied compressive load. Mechanical strains which develop around the periphery of the vertebral body are also viscoelastic with the applied compressive load. Applied compressive load against time also shows viscoelastic behavior. However, annulus does not respond viscoelastically with the applied load. It showed a linear response to compressive loading.

Authors:

• Harcharan Singh Ranu

Keywords:

• Intradiscal pressure transducer (IDPT)
• intervertebral pressure transducer (IVPT)
• mechanical strains of vertebral bone
• viscoelasticity of human spinal disc.

References:

[1] H S Ranu. "Multipoint determination of pressure-volume curves in
human pressure-volume curves in human intervertebral discs" Annals of
the Rheumatic Diseases 1993; vol. 52: pp. 142-146
[2] H.S. Ranu, "Viscoelastic behavior of the human spinal disc and the
vertebra." in Proc. Ist Southern Biomedical Engineering Conference.
Pergamon Press, New York. 1982. pp. 85-88.
[3] H.S. Ranu. "Time dependent response of the human inter-vertebral disc
to loading". Engineering in Medicine 1985; 14: 43-5.
[4] H.S. Ranu. "Relation between the nucleus and the annulus pressures of
the lumbar spinal disc". Scand J Rheumatol; suppl 60: pp. 27. 1986
[5] H.S. Ranu, A.I. King "Correlation of intradiscal pressure withvertebral
endplate pressure". In Engineering aspects of the spine. London:
Mechanical Engineering Publications, pp. 37-42, May, 1980.
[6] H.S. Ranu., R.A. Denton, and A.I. King, "Pressure distribution under an
intervertebral discÔÇöan experimental study". J. Biornech..vol. 12. pp.
807-812, 1979.
[7] H.S. Ranu. "The distribution of stresses in the human lumbar spine". In:
Yettram, A L, ed. Material properties and stress analysis in
biomechanics. Manchester: Manchester University Press, Ch. 17, pp.
240-249. 1989.
[8] A. Nachemon. " Lumbar intradiscal pressure.". Acta Orthop. Scand.
1960. Vol. 43. pp. 1-104.