Comparison of PACS and hard-copy 51-inch radiographs for measuring leg length and deformity.

BACKGROUND The picture archiving and communication system (PACS) eventually will replace the use of standard hard-copy radiographs. It is unknown whether measurements of limb length discrepancy (LLD) and deformity on PACS compare in accuracy and reproducibility with those from hard-copy radiographs. QUESTIONS/PURPOSES We compared the reproducibility and reliability of LLD and deformity measurements for each of these two media. METHODS We retrospectively reviewed 51-inch standing lower extremity images obtained for LLD or deformity analysis from 40 patients to compare the measurements and their reliability on hard-copy film with those performed on soft-copy PACS. Two observers independently performed measurements twice using each system at 1-week intervals to minimize interobserver or intraobserver bias. Intraclass correlation coefficients (ICCs) were determined to test intraobserver and interrater reliability of Rater 1 and Rater 2. RESULTS Interrater reliability of measurements made on hard copy ranged from 0.69 to 0.99 and PACS-derived measurements ranged from 0.66 to 0.98. Intraobserver reliability for Rater 1 for measurements made on hard copy ranged from 0.853 to 0.999 and PACS-derived measurements ranged from 0.80 to 0.996. Intraobserver reliability for Rater 2 for measurements made on hard copy ranged from 0.931 to 0.999 and PACS-derived measurements ranged from 0.962 to 0.999. CONCLUSIONS Each system yielded comparable reliability for measurements, therefore, transition to PACS to perform measurements in patients with LLD or deformity can be made with confidence. LEVEL OF EVIDENCE Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.