The Journal of Bone and Joint Surgery, Vol 64, Issue 5 713-720, Copyright © 1982 by Journal of Bone and Joint Surgery, Inc
Loads on the lumbar spine. Validation of a biomechanical analysis by measurements of intradiscal pressures and myoelectric signals
A Schultz, G Andersson, R Ortengren, K Haderspeck and A Nachemson
We studied the validity of predictions of compressive loads on the lumbar
spine and contraction forces in lumbar trunk muscles based on a
biomechanical model. The predictions were validated by quantitative
measurements of myoelectric activities at twelve locations on the trunk and
of the pressure in the third lumbar disc. Twenty-five tasks were performed
isometrically by four healthy volunteers. The model predicted that the
tasks imposed mean compressive loads on the spine of as much as 2400
newtons and required contraction forces of the posterior muscles of the
back of as much as 1800 newtons. Intradiscal pressures of as much as 1600
kilopascals were measured. The predicted and measured quantities were well
correlated. It appears that the model adequately predicted the compressive
loads on the lumbar spine and the tensions in the back muscles. Clinical
Relevance: Patients with low-back disorders limit their physical
activities, which indicates that loading on the spine must be a factor in
those disorders. This study shows that the loads imposed on the spine by
physical activities need not be measured. They can easily be calculated.
This will significantly accelerate biomechanics research on low-back
disorders. The calculation techniques that we validated for predicting
loads on the spine can be used to calculate the loads on any skeletal
structure. Those loads are largely determined not by the externally applied
loads, but by the moments of those applied loads and by the moments of the
weights of the body segments that the structure must support.