[Sonographic imaging of leg geometry].

Area of Science:

• Orthopedics
• Medical Imaging
• Biomedical Engineering

Background:

• Posttraumatic malalignments frequently occur after intramedullary (IM) nailing of lower extremity fractures.
• Conventional ultrasound (US) is less accurate than computed tomography (CT) for measuring tibial or femoral length and torsion.

Purpose of the Study:

• To introduce and evaluate a novel 3-D ultrasound (US) technique for precise, single-step determination of lower extremity length and torsion.
• To compare the accuracy and reliability of the 3-D US method against CT (Ulm's method).

Main Methods:

• A 3-D US method utilizing a standard US machine, a 5 MHz linear probe, and an US localizer was developed.
• Reference markers were used to mitigate errors from patient position or motion.
• The 3-D US technique was compared with CT (Ulm's method) in 50 adults and 50 children for measuring tibial and femoral length and torsion.

Main Results:

• The 3-D US method demonstrated high accuracy, with maximum differences of 7 degrees for torsion and 7 mm for length compared to CT.
• Excellent reproducibility was observed, with maximum standard deviations of 1.6 mm for length and 1.5 degrees for torsion.
• The 3-D US technique proved superior to CT in reliability and reproducibility.

Conclusions:

• The new 3-D US technique provides accurate, reliable, and reproducible measurements of lower extremity length and torsion without ionizing radiation.
• Clinical advantages include speed, independence from patient movement, and radiation avoidance, making it suitable for fracture follow-up and pediatric evaluations.