Article

Articulated or hinged ankle-foot orthosis (AFO) allow more range of
motion. However, quantitative investigation on articulated AFO is still sparse.
OBJECTIVE: The objective of the study was to quantitatively investigate effects
of alignment and joint types on mechanical properties of the thermoplastic
articulated AFO. STUDY DESIGN: Tamarack dorsiflexion assist flexure joints with
three durometers (75, 85 and 95) and free motion joint were tested. The AFO joint
was aligned with the center of the motor shaft (surrogate ankle joint), 10 mm
superior, inferior, anterior and posterior with respect to the motor shaft
center. METHODS: The AFO was passively moved from 20 degrees plantar flexion to
15 degrees dorsiflexion at a speed of 10 degrees /s using a motorized device.
Mechanical properties including index of hysteresis, passive resistance torque
and quasi-static stiffness (at neutral, 5 degrees , 10 degrees and 15 degrees in
plantar flexion) were quantified. RESULTS: Significant effects of joint types and
joint alignment on the mechanical properties of an articulated thermoplastic AFO
were revealed. Specifically, center alignment showed minimum resistance and
stiffness while anterior and posterior alignment showed significantly higher
resistance and stiffness. The dorsiflexion assist torques at neutral position
ranged from 0.69 +/- 0.09 to 1.88 +/- 0.10 Nm. Conclusions: Anterior and
posterior alignment should be avoided as much as possible. CLINICAL RELEVANCE:
The current study suggested that anterior and posterior alignment be avoided as
much as possible in clinical practice due to potential skin irritation and
increase in stress around the ankle joint.

Langue : ANGLAIS