The Reliability of a Posterior-to-Anterior Spinal Stiffness Measuring System in a Population of Patients With Low Back Pain
Received 20 June 2006; received in revised form 7 September 2006; accepted 21 September 2006.
Abstract
Objective
A system for measuring posterior-to-anterior spinal stiffness (PAS) was developed for use in clinical trials of manipulation for low back pain. The reliability of this device is under investigation in this study.
Methods
The PAS system uses electronic sensors to record displacement and force while a human operator provides the force of indentation. A test-retest design was used with measures repeated by the same operator within 5 minutes. Posterior-to-anterior loads were applied to each lumbar spinous process of patients lying prone on a hard flat bench. Force and displacement were recorded and used to calculate PAS.
Results
The subjects consisted of 22 males and 14 females; average age was 49.1 years (SD, 14.2). All subjects had low back pain of at least 4 weeks duration, with mean Roland-Morris scores of 7.6 (SD, 3.3). Spinal stiffness ranged from 4 to 26 N/mm (average, 11.2; SD, 3.5). Stiffness in the first and second tests varied on the average by 0.31 N/mm (P = .03). Standard error of the measurement was 1.62 N/mm. The single measures intraclass correlation coefficient (3,1) was 0.790 (95% confidence interval, 0.739-0.832).
Conclusions
The equipment and method produced repeatable results over the short-term. The system may be sensitive enough to detect changes in spinal stiffness that occur with care.
aAssociate Professor of Research, Palmer Center for Chiropractic Research, Davenport, Iowa
bIowa Spine Research Center, 1408 SC, Biomedical Engineering Department, The University of Iowa, Iowa City, Iowa
cVice President for Research, Palmer Center for Chiropractic Research, Davenport, Iowa
Submit requests for reprints to: Edward F. Owens Jr., MS, DC, Associate Professor of Research, Palmer Center for Chiropractic Research, Davenport, IA 52803.
ABSTRACT