[The deformation behavior of human lumbar intervertebral discs subjected to long term axial dynamic compressive forces (author's transl)]

Lumbar range of motion: influence of time of day and individual factors on measurements

STUDY DESIGN

Influence of time of day and individual factors on the measurements of the lumbar range of motion was investigated.

OBJECTIVES

To investigate factors that influence lumbar range of motion.

SUMMARY OF BACKGROUND DATA

Twenty-nine patients with chronic low back pain participated in the study.

METHODS

The lumbar range of motion was measured by inclinometer technique, Schober sign, modified-Schober sign, and fingertip-to-floor method in the morning, at noon, and in the afternoon. The lumbar range of motion was correlated with patients' gender, age, and body weight.

RESULTS

Total lumbar range of motion measured by the inclinometer technique and the modified-Schober sign increased significantly throughout the day from morning to afternoon. Extension lumbar range of motion was shown to be independent of the time of measurement. There were no significant correlations between lumbar range of motion and gender, age, and body weight of the patients.

CONCLUSION

For the reliability of a measurement, it is important to investigate lumbar range of motion at the same time of day.

Slow deformation of intervertebral discs

Intervertebral discs exhibit pronounced time-dependent deformations when subjected to load variations. These deformations are caused by fluid flow to and from the disc and by viscoelastic deformation of annulus fibres. The fluid flow is caused by differences between mechanical and osmotic pressure. A mechanical model of lumbar disc functions allows one to calculate both the extent of fluid flow and its implications for disc height as well as the role played by viscoelastic deformation of annulus fibres. From such calculations changes in body height are estimated. Experimental results already documented in the literature offer bases for the determination of the parameters involved. Body height variations are studied, both those related to normal diurnal rhythmicity and those related to somewhat exceptional circumstances. The normal diurnal fluid flow is found to be about +/- 40% of the disc fluid content late in the evening. Viscoelastic deformation of annulus fibres contributes approximately one quarter of the height change obtained after several hours normal activity, but dominates during the first hour.

Biomechanical properties of human intervertebral discs subjected to axial dynamic compression--influence of age and degeneration

This investigation was performed to study biomechanical properties of human intervertebral discs as a function of age. 178 specimens from 21 spinal sections (Th9-S1, 5-84 yr) were subjected to axial dynamic compression; the load being 950 +/- 540 N. The results revealed three distinct age ranges: From the first to the middle of the third decade: axial deformability decreases within the thoracic region, and remains almost constant within the lumbar spine; creep decreases in both parts. From the middle of the third to the beginning of the sixth decade: the biomechanical behavior scarcely alters. Afterwards: axial deformability remains unchanged; creep, however, again increases within the lumbar spine. The results reveal the discs behave most efficiently within the age range where the incidence of back pain is maximal.