Determination of leg length discrepancy: A comparison of weight-bearing and supine imaging

Leg length discrepancy (LLD) may be determined by comparison of leg (lower extremity) lengths measured during physical exami-nation or by radiographic means. Leg lengths may be measured with the patient in standing, weight-bearing position or in supine position. We used a low dose digital radiographic unit to test the hypothesis that there is a difference in LLD determined from radiographs obtained with the patient standing and those obtained with the patient supine. Conventional physical examination mea-surements also were compared with the radiographic measure-ments. The amount of LLD that is clinically meaningful has not been established, although 10 to 12 mm has been used as a threshold difference of clinical meaningfulness in the past. Analy-sis of our data, using 10 mm as the threshold of difference, reveals high level correlation by linear regression analysis and no signifi-cant difference by t-test between measurements obtained from standing and supine radiographs. A weak correlation and statistical difference existed between each set of radiographic measurements and physical examination measurements.