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.