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Measuring Limb Length

This is the first study to use MRI to measure limb length. Scientists used 12 cadavers (body preserved after death for study). They used four different methods of limb measurement and compared the results. Just the length of the femur (thigh) bone was measured. Standard X-rays were used along with CT scans, MRIs, and electronic calipers.

All three types of imaging gave reliable and accurate results. X-rays were the most accurate but X-ray exposes the person to ionizing radiation. MRIs don't expose to radiation but take longer and cost more. The electronic caliper is a direct measurement of the bone. It's the gold standard measurement used to compare the imaging results.

The authors conclude MRI might be a good tool to use when making serial measurements of limb length in children. Children with leg length differences often need new X-rays every six months for many years. Using MRIs, which are both reliable and accurate, can reduce the amount of ionizing radiation.

References: Anne H. Leitzes, MD, et al. Reliability and Accuracy of MRI Scanogram in the Evaluation of Limb Length Discrepancy. In Journal of Pediatric Orthopaedics. November/December 2005. Vol. 25. No. 6. Pp. 747-749.

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