The objective of the study was to evaluate the reliability of frontal plane lower limb alignment measures using a landmark-based method by (1) comparing inter- and intra-reader reliability between measurements of alignment obtained manually with those using a computer program, and (2) determining inter- and intra-reader reliability of computer-assisted alignment measures from full-limb radiographs. An established method for measuring alignment was used, involving selection of 10 femoral and tibial bone landmarks. (1) To compare manual and computer methods, we used digital images and matching paper copies of five alignment patterns simulating healthy and malaligned limbs drawn using AutoCAD. Seven readers were trained in each system. Paper copies were measured manually and repeat measurements were performed daily for 3 days, followed by a similar routine with the digital images using the computer. (2) To examine the reliability of computer-assisted measures from full-limb radiographs, 100 images (200 limbs) were selected as a random sample from 1,500 full-limb digital radiographs which were part of the Multicenter Osteoarthritis Study. Three trained readers used the software program to measure alignment twice from the batch of 100 images, with two or more weeks between batch handling. Manual and computer measures of alignment showed excellent agreement (intraclass correlations [ICCs] 0.977–0.999 for computer analysis; 0.820–0.995 for manual measures). The computer program applied to full-limb radiographs produced alignment measurements with high inter- and intra-reader reliability (ICCs 0.839–0.998). In conclusion, alignment measures using a bone landmark-based approach and a computer program were highly reliable between multiple readers.
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The second study, using full-limb radiographs, was supported by the National Institutes of Health Grants AR47785 and AG18820 and MOST Ancillary Study Grant AP07-04. The authors wish to acknowledge the contribution of Mr. Christopher Wale, BSc (I-M Innovations, Inc.), in the design of the computer software tools and analysis program. The support of OAISYS Inc. in provision of the Horizon Surveyor Software Program used in these studies is appreciated.
Conflict of interest statement
T. Derek V. Cooke, President and Principle Share Holder of OAISYS Inc.
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