The Optimum Spine
Gracovetsky S, Farfan H.
Spine
11(6) : 543-573, 1986.
Abstract
System theory is used to describe the mechanism of the lumbar spine. The role
of the spine in vertebrate evolution is presented. The importance of the intervertebral
joint for the survival of the species is shown to be crucial. The mechanical behavior of
the joint is derived, and from this the corresponding spinal motion and muscular responses
is calculated. It is shown that physiologic behavior implies that the stress at the
intervertebral joints is equalized and minimized. From this simple condition, the motion
of the spine in the sagittal plane is calculated. From the analysis of sagittal plane
motion together with a knowledge of the energy transfer through the intervertebral joint,
a new theory of locomotion is derived. This theory of locomotion differs in important
respects from current theories, but nevertheless explains available experimental data.
This unified theory of the function of the human spine permits the determination of the
level of safe loads that can be lifted and transported. It predicts the conditions of load
transfer through a joint. It proposes a new approach to the mechanism of arthritis and to
the repair of fractures.
