Article

Hip rotation from gait analysis informs clinical decisions regarding correction
of femoral torsional deformities. However, it is among the least repeatable due
to discrepancies in determining the medial-lateral axis of the femur.
Conventional or functional calibration methods may be used to define the axis but
there is no benchmark to evaluate these methods. Freehand 3D ultrasound, the
coupling of ultrasound with 3D motion capture, may provide such a benchmark. We
measured the accuracy in vitro and repeatability in vivo of determining the femur
condylar axis from freehand 3D ultrasound. The condylar axis provided the
reference medial-lateral axis of the femur and was used to evaluate one
conventional method and three functional calibration methods, applied to three
calibration movements. Ten healthy subjects (20 limbs) underwent 3D gait analysis
and freehand 3D ultrasound. The functional calibration methods were a
transformation technique,
a geometrical method and a method that minimises
variance of knee varus-valgus kinematics (DynaKAD). The conventional method used
markers over the femoral epicondyles. The condylar axis determined by 3D
ultrasound showed good accuracy in vitro, 1.6 degrees (SD: 0.3 degrees ) and good
repeatability in vivo, 0.2 degrees (RSMD: 2.3 degrees ). The DynaKAD method
applied to the walking calibration movement determined the medial-lateral axis
closest to the ultrasound reference. The average angular difference in the
transverse plane was 3.1 degrees (SD: 6.1 degrees ). Freehand 3D ultrasound
offers an accurate, non-invasive and relatively fast method to locate the
medial-lateral axis of the femur for gait analysis.
CI - Copyright (c) 2016 Elsevier B.V. All rights reserved.

Langue : ANGLAIS