Ultrasonic indentation: a procedure for the noninvasive quantification of force-displacement properties of the lumbar spine.
BACKGROUND
Alterations in the normal force-displacement (FD) properties of spinal tissues have been associated with specific forms of pathology, such as degenerative disk disease. Unfortunately, few current procedures exist that assess spinal FD properties in an accurate, reliable, and noninvasive manner. Consequently, the clinical relevance of the relation between spinal disorders and spinal FD properties is not fully understood.


OBJECTIVE
To investigate the accuracy and reliability of spinal FD measures obtained through use of a procedure in which real-time ultrasonic imaging (ultrasonic indentation) is used during load-controlled external indentation.


METHODS
McCaig Centre for Joint Injuries and Arthritis Research, University of Calgary.


METHODS
The bench-top accuracy and reliability of ultrasonic indentation were assessed by cyclic indentation of a spring-mounted platform. These data were compared with criterion data derived from a materials testing machine. A porcine preparation was then used to assess the accuracy of ultrasonic indentation-generated estimates of vertebral displacement in comparison with a criterion of optically tracked displacement. In addition, previously unreported parameters relating to indentation accuracy (frame deflection and off-axis loading) were characterized.


RESULTS
Reliability of ultrasonic indentation ranged between 0.99 and 1.00 (intraclass correlation coefficient). Error values in force, displacement, and stiffness ranged from 0.81% to 13.62% over varying experimental conditions.


CONCLUSIONS
Ultrasonic indentation is a unique procedure that is capable of assessing, noninvasively, FD properties of spinal tissues, including vertebral displacement in the indentation plane. The results of this study suggest that ultrasonic indentation is a potentially useful technique for quantifying spinal FD properties in vivo.
Kawchuk
G N
GN
McCaig Centre for Joint Injury and Arthritis Research, Department of Medical Science, University of Calgary, Alberta, Canada. kawchuk@mccaig.ucalgary.ca
Fauvel
O R
OR
Dmowski
J
J
D000818:Animals; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D013122:Spinal Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D013552:Swine; D014463:Ultrasonography