ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

1. ABSTRACT
LOADS ON THE LUMBAR SPINE
A. Rohlmann 1
Little is known about the realistic loads which act on the lumbar spine during activities
of daily living. This paper gives a short overview about the measuring techniques used
in in vivo studies and about analytical methods used to estimate spinal loads. A
complete measurement of the spinal loads is not yet possible but the intradiscal pressure
and the loads acting on spinal implants have still been measured in vivo. These data
allow a comparison of the relative loads of different activities, e.g. sitting and standing.
Analytical models of the spine allow an estimation of spinal loads; however, their
validation remains a difficult task due to a lack of in vivo measured data. Furthermore,
recommendations are provided for the loads, in order to simulate motions in the three
main anatomical planes.
2. INTRODUCTION
The mechanical behaviour of the lumbar spine can be estimated using numerical
models. Some of these finite element models are used as an effective tool for analysing
phenomena that cannot be clarified by experimental methods, e.g. degenerative
processes or age-related muscle dysfunction. Numerical models require knowledge of
the geometry and material properties of the different structures, the boundary conditions
and the loads. Unfortunately, loading of the spine is still not well understood and the
applied loads differ strongly in the literature. The various loads applied for simulation of
a certain posture may lead to considerable differences in the results, and these are often
much higher than those occurring due to other factors such as material properties or
geometrical parameters of the different structures.
In the case of the lumbar spine, the loads affect intervertebral motion, intradiscal
pressure, forces in the facet joints as well as stresses and strains in the various
structures. For static positions, the spinal loads depend on gravitational forces and
muscle forces required to maintain equilibrium. Spinal loads can be estimated by using
analytical models or by measuring partial loads. The following paragraphs summarize
several in vivo measuring methods and analytical approaches to estimate the overall
spinal loads and how to simulate them within in vitro and numerical studies.
1
Dr.-Ing., Julius Wolff Institut, Charité – Universitätsmedizin Berlin, Augustenburger Platz 1, 13353
Berlin, Germany