Abstract
The present paper describes a computer analysis of the motor units from the gluteus maximus, the tibialis anterior and the gastrocnemius muscles, so as to clarify the mechanism of muscular support around the pelvis and the lower extremities in patients with low back pain. The subjects observed consisted of 33 cases with low back pain and 17 normal persons.
One hundred consecutive discharges of each motor unit obtained in relaxed standing posture were automatically displayed in the form of amplitude correlogram, amplitude variation and interval variation. Amplitude correlograms were classified into 4 types, i. e., type A, B, C and D. Amplitude variations were classified into 3 classes, i. e., (-) : amplitude variations within 100 μV, (±) : between 100 and 200 μV, and (+) : over 200 μV. Interval variations were classified into 2 classes, i. e., (-) : discharge intervals within 100 msec and (+) : over 100 msec. The results were as follows:
1) In almost all normal persons, the results of these amplitude correlograms were of type C, whereas amplitude and interval variations were of class (-).
2) In the majority of the patients with intervertebral disc herniation and spinal canal stenosis, amplitude correlograms were of type B or D, amplitude and interval variations were of class (±) or (+) .
3) Almost all the patients with spondylolysis showed type C in amplitude correlograms and (-) in amplitude and interval variations. These results were very similar to those in normal cases.
From these results, it can be stated that the stability of the pelvis and the lower extremity during standing is mainly controled by the ligamentous support in normal persons, while in the patients with low back pain, the muscular support plays an important role in the stabilizing mechanisms around the pelvis and the lower extremities instead of the weakened ligamentous support.
