Measuring leg length and leg length difference with the method of real time sonography

Abstract

A brief presentation of the clinical and radiological methods to measure the leg length and the leg length difference is followed by an outline of the new diagnostic method for measuring the leg length and the leg length difference by means of real-time sonography. Tests conducted on corpses, as well as clinical examples, show that sonography is an ideal method for determining the exact lengths of the femur and tibia. The joint gaps on the hip joint, knee joint and upper ankle joint can be visualised by means of a 5 MHz linear scanner. A 1 mm strong metal bar on the skin and under the scanner are positioned at a right angle to the longitudinal axis of the body so that the bar can be seen in the centre of each joint gap by means of real-time sonography. A measuring device gives the distances of the joint gaps in cm so that the differences correspond to the real length of femur and tibia. This standardised measuring procedure is done by a specially developed bearing and measuring device. The results of the sonographical measurings on 20 corpses and checking after consecutive dissections showed in 75% of the cases a 100% sonographic measuring accuracy of the total leg length. The separately considered results for femur (85%) and tibia (90%) were even better. The maximum sonographic measuring fault was 1.0 cm for the femur (in one case) and 0.5 cm for the tibia, respectively. Thus, sonographic measuring of the leg length offers a reliable, non-invasive and easily performed new method that can be repeated any number of times. It is ideal for the development control of therapeutically influenced as well as spontaneous transformations of leg length differences.