Reliability of phase-velocity measurements of tibial bone.

ABSTRACT

BACKGROUND AND PURPOSE: The Bone Stiffness Measurement Device-Swing is capable of measuring the propagation velocity of flexural waves in human tibial bone, which relates to bending stiffness. If the interrater and intrarater reliability of measurements obtained with the device are established, it can be used with confidence in assessing changes in bone. The purposes of this study were to detect potential sources of measurement error and to establish the interrater and intrarater reliability of measurements taken with the device. SUBJECTS AND METHODS: In the first part of the study, a random-effects design was used to obtain phase-velocity measurements in subjects without known orthopedic or neurological impairments. The second part of the study consisted of possible applications of the device with mixed designs on subjects with spinal cord injuries. By means of generalizability theory, multiple sources of error (eg, occasion, clinician, repetition) were estimated. For the clinical trial, 17 persons with spinal cord injuries not older than 5 weeks were tested. RESULTS: The standard error of measurement (SEM) for intrarater reliability measurements ranged from 7.3 to 9.8 m x s(-1) . The SEMs for interrater reliability measurements ranged from 5.7 to 9.5 m x s(-1). The SEMs for measurements obtained by a single clinician in a clinical population ranged from 11.9 to 39.7 m x s(-1). CONCLUSION AND DISCUSSION: The reproducibility of measurements obtained with the device is suitably high for the device to be used for evaluation in clinical and research settings.