Alignment and articular orientation of lower limbs: manual vs computer-aided measurements on digital radiograms.

PURPOSE: To compare the manual measurements of lower limbs on digital images with those obtained with dedicated software.

MATERIALS AND METHODS: Forty patients with a clinical suspicion of lower limb deformity were enrolled. Eighty digital radiographs were produced with a remote-controlled radiography system (Philips Omnidiagnost). The measurements were taken separately by an Orthopaedic Surgeon and by a Radiologist, by hand and with the aid of software, respectively. Five parameters were assessed: femoral length, tibial length, distal-medial femoral angle, proximal-medial tibial angle and tibial-femoral angle. The statistical analysis of the comparison was based on Student's t-test. The inter-observer variability of the methods, manual and computer-aided, was evaluated with Fisher's F-test on a sample of measurements (20 lower limbs), taken by 5 different Orthopaedic Surgeons and Radiologists, respectively.

RESULTS: There were no statistically significant differences between the measurements taken with the manual and computer-aided methods (p<0.05). The overall reproducibility of both methods was similar; conversely, the separate evaluation of angles and lengths showed that the computer-aided method was less variable in the measurement of angles and a little more variable in the measurement of lengths than the manual method.

CONCLUSIONS: The computer-aided evaluation of the alignment and articular orientation parameters of lower limbs is as accurate and reliable as the traditional manual method, but is faster and allows better-quality images.