Article

Relative movement of skin markers to underlying bone limits a valid
interpretation of axial femorotibial rotation in noninvasive optoelectronic gait
analysis. A distal femoral clamp is a practical solution for thigh marker
placement, however, existing devices are still susceptible to measurement errors
at increased angles of knee flexion. We developed the Femoral Epicondylar Frame
(FEF), which should result in less femoral rotational measurement error due to
its anatomic fitting and controlled pressure adjustment. Seven subjects with a
total knee replacement in situ, mean age 71 years, mean body mass index 28, were
equipped with the frame mounted with a set of tantalum markers. Fluoroscopic data
was collected during a step-up motion. A three-dimensional model fitting
technique was used to compare the in vivo position and orientation of the frame
and the femoral prosthesis component of the prosthesis. The frame rotational
measurement error appeared to be linearly dependent on the knee flexion angle.
When considering knee flexion angles lower than 40 degrees of flexion, the
highest measurement error was 3.3 degrees on average, with an absolute extreme of
6.2 degrees . It is concluded that the accuracy of the FEF is sufficient to
evaluate axial knee rotation with optoelectronic gait analysis at group level in
clinical studies.
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Langue : ANGLAIS