The reliability of clinical tools with and without ultrasound guidance to measure leg-length inequality

Purpose: To determine and compare the reliability and efficiency of various methods of leg-length measurement. Methods: A total of 88 leg-lengths were measured among 50 subjects (79%–84% female, mean age = 30–33 years). Leg-lengths were measured in both supine and standing positions using multiple devices, including a tape measure, a LASER distance meter, and diagnostic ultrasound. Results: All methods of leg-length measurement using the middle of the femoral head as a reference point, identified via ultrasound, demonstrated excellent reliability (intraclass correlation coefficient = 0.95–1.00). Measurements performed in supine, using the anterior superior iliac spine as a reference point, with a tape measure, demonstrated good-to-excellent reliability (intraclass correlation coefficient = 0.86–0.95, standard error of the measurement = 16.1–19.9 cm). Standing measurements using the anterior superior iliac spine as a reference point, using a tape measure, demonstrated fair-to-excellent reliability (intraclass correlation coefficient = 0.71–0.95). Conclusion: Ultrasound-guided landmark identification appear to be a more reliable method compared to palpation of the anterior superior iliac spine for measurement of leg-length using clinical tools. When coupled with ultrasound guidance, a hand-held LASER distance meter/pitch locator apparatus or a retractable tape measure appears to be acceptable alternatives to a fixed LASER distance meter on a linear actuator for leg-length measurement.