Reliability of digital radiographs for pediatric lower extremity alignment.
BACKGROUND
Digital radiography is the standard method for sharing and storing radiographs. The purpose of this study was to evaluate the interobserver and intraobserver reliability of computer-based and manual measurement methods in determining lower extremity alignment on digital images of pediatric patients.


METHODS
Thirty-two digital standing long leg radiographs of pediatric patients were evaluated with 9 varus, 11 valgus, and 12 neutral alignment films. Six evaluators measured the digital images with a standard computer-based measurement method twice and a manual paper print out method twice. Measurements included the lateral distal femoral angle (LDFA), the medial proximal tibia angle (MPTA), the joint line congruency angle, and the mechanical axis deviation (MAD). Interobserver and intraobserver reliability for computer-based and manual methods were calculated using intraclass correlation coefficients.


RESULTS
The interobserver reliability for all angular measurements was found to be fair to good for both measurement methods. The MAD had excellent intraobserver and interobserver reliability. LDFA and MPTA interobserver reliabilities were better by the manual method than the computer-based method. Intraobserver reliability was higher in the computer-based LDFA than manual methods, whereas the MPTA measurements were more reliable by manual methods.


CONCLUSIONS
Computer-based and manual methods for determining lower extremity alignment from digital radiographs are not dissimilar and both provide fair to good reliability. The MAD was a highly reliable measurement. Overall, measurement of the digital images was not as reliable by either method as measurement of traditional full-length teloroentgenograms. The observer should be familiar with the measurement program to minimize errors. Digital images can be measured reliably and then used for treatment decisions, however, time and care should be taken with measurements.


METHODS
Diagnostic level II.
Department of Orthopaedic Surgery, Kalamazoo Center for Medical Studies, Michigan State University, Kalamazoo, MI, USA.
Philip D
PD
Nowicki
Kelly L
KL
Vanderhave
Frances A
FA
Farley
Lawrence R
LR
Kuhns
William
W
Dahl
Michelle S
MS
Caird
D000293:Adolescent; D002648:Child; D005260:Female; D005269:Femur / Q000002:abnormalities / Q000000981:diagnostic imaging*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007866:Leg / Q000002:abnormalities / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging* / Q000473:pathology