Validation of the flexible electrogoniometer for measuring thoracic kyphosis.
METHODS
Three experiments to validate the use of the flexible electrogoniometer (FEG) as a tool to measure thoracic kyphosis.


OBJECTIVE
To investigate the accuracy, test-retest reliability, and concurrent validity of the FEG as applied to the thoracic spine.


BACKGROUND
Thoracic kyphosis is commonly measured by the Cobb angle from lateral radiograph. Other less-invasive tools have been developed, but all yield only static measurements or are restricted to the laboratory. The FEG, which can record joint angles over time outside the laboratory, has been used to measure other joints but has not yet been validated for measurement of the thoracic spine.


METHODS
First, the FEG was bench-tested against a plurimeter for accuracy. Second, 12 subjects performed 7 functional activities 1 week apart to assess the test-retest reliability. Finally, to examine concurrent validity, 12 subjects underwent radiography in "upright" and "slumped" standing with the FEG attached to the skin over their thoracic spine. Three Cobb angles, which corresponded with the inner, mid, and outer margins, respectively, of the overlying FEG end blocks were compared with the FEG angles.


RESULTS
The correlation between the FEG and the plurimeter was excellent (r > 0.99, P < 0.0001), although some accuracy was lost at extremes of range. The mean correlation between the first and second measurements was very strong (intraclass correlation coefficient(2,1) 0.92, P < 0.0001; range, 0.89-0.95). The mid-Cobb angle showed the least absolute angular difference from, and was highly correlated with, the FEG angle (r = 0.81, P < 0.01).


CONCLUSIONS
The FEG demonstrated excellent accuracy and test-retest reliability and correlated very well with the Cobb angle. The FEG measurement seemed to correspond most closely with the Cobb angle measured between the middle of the FEG end blocks.
Perriman
Diana M
DM
Trauma and Orthopaedic Research Unit, Canberra Hospital and the Australian National University, Canberra, Australia. diana.perriman@anu.edu.au
Scarvell
Jennifer M
JM
Hughes
Andrew R
AR
Ashman
Bryan
B
Lueck
Christian J
CJ
Smith
Paul N
PN
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053587:Arthrometry, Articular / Q000295:instrumentation* / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D015203:Reproducibility of Results; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology*