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

Clin Orthop Relat Res. 2011 Jan;469(1):244-50. doi: 10.1007/s11999-010-1460-z. Epub 2010 Jul 13.


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.

Publication types

  • Comparative Study

MeSH terms

  • Humans
  • Leg Length Inequality / diagnostic imaging*
  • Lower Extremity Deformities, Congenital / diagnostic imaging*
  • New York City
  • Observer Variation
  • Predictive Value of Tests
  • Radiographic Image Interpretation, Computer-Assisted
  • Radiology Information Systems*
  • Reproducibility of Results
  • Retrospective Studies
  • X-Ray Film*