Posteroanterior spinal stiffness at T5, T10, and L3 levels in normal subjects

To measure, by using standardized device and protocol, posteroanterior (PA) spinal stiffness at the 5th and 10th thoracic (T5 and T10) and 3rd lumbar (L3) vertebral levels in asymptomatic adult volunteers.

A cross-sectional study.

Osteopathic Heritage Foundation Physical Medicine Core Research Laboratory where the Therapeutic Spinal Mobilizer was fabricated to standardize the testing protocol.

Sixteen asymptomatic adult volunteers.

Volunteers were in the prone position on the treatment plinth and the loading block of the loading piston was placed at T5, T10, and L3. The subjects were instructed to remain still, to not contract any muscle, and to stop breathing mid cycle for 15 seconds when the data acquisition was initiated for a 10-second test cycle. The force was measured by using the load cell, and the spinal deformation was measured by the linear variable differential transducer. The data were extracted and subjected to descriptive statistics and analysis of variance to determine the effect of independent variables on spinal stiffness.

The PA spinal stiffness at 3 spinal levels was significantly different (P < .0001). The spinal stiffness was significantly affected by the testing load, age, gender, and body weight of the subjects (P < .0001). The PA stiffness of the entire sample at 3 spinal levels ranged from 4.8-8.8 N/mm. The spinal stiffness values could be predicted as the function of testing load and body weight (P < .01).

Results of this experiment suggest that the standardized and repeatable methodology will result in reliable stiffness values. Because the spinal stiffness is an indicator of patient's symptoms and it is an important variable in selection of treatment regimen, it is important to be able to measure this variable with a standardized protocol. Values from asymptomatic subjects can be used to study and to compare the symptomatic patients.