The Journal of Bone and Joint Surgery, Vol 74, Issue 6 897-902, Copyright © 1992 by Journal of Bone and Joint Surgery, Inc
Comparison of orthoroentgenography and computed tomography in the measurement of limb-length discrepancy
A Aaron, D Weinstein, D Thickman and R Eilert
Department of Orthopaedic Surgery, Children's Hospital, Denver, Colorado 80218.
To determine the most accurate roentgenographic technique for the
measurement of limb-length discrepancy, the twenty lower extremities of ten
cadavera were measured with use of both orthoroentgenograms and lateral
scout computed-tomographic scanograms. The actual anatomical limb length
also was measured, to serve as a control. The effects of flexion of the
knee joint, use of an external fixator, cost and time of the examination,
and exposure to radiation also were determined. No statistically
significant difference in the measurements of the length of the femur was
found between the two methods at neutral or at 15, 30, or 45 degrees of
flexion of the knee. However, computed tomography was significantly more
accurate than orthoroentgenography in the measurements of length of the
tibia and of total length of the limb when the knee was flexed to 30
degrees or more (p less than 0.01). The placement of an Ilizarov fixator
did not alter the results. The cost and time necessary to complete an
examination were comparable for the two methods. However, computed
tomography delivered only 20 per cent of the radiation needed for
orthoroentgenography. Computed tomography is more accurate than
orthoroentgenography for the measurement of limb-length discrepancy in
patients who have a flexion deformity of the knee.
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