Biomedical Engineering Reference
In-Depth Information
positioning of anatomical landmarks, both of which affect the
estimation of joint kinematics.
4.2.1
. Soft tissue artifacts
The movement of soft tissues, typically called “Soft Tissue
Artifacts”, causes much greater errors than instrumental
errors, which makes these the biggest problem in motion
analysis [LEA 05]. These artifacts correspond to the
superposition of several phenomena: effects of inertia,
muscular contractions, deformation and sliding of the skin
over the underlying bone structure, especially that close to
joints [CAP 96]. They depend not only on the body
segment but also on the location of the marker on the
body segment, and their amplitude is much greater than
that of instrumental errors. Moreover, these artifacts are
extremely difficult to correct since their frequency is very
close to that of the analyzed motion (which makes filtering
inefficient), and they are also very dependent on the task
performed [FUL 97] or even on the morphology of the
subject.
4.2.1.1
. Assessment
Peters
et al
. [PET 10] proposed a literature review of the
quantification of soft tissue artifacts on the lower limb. They
pointed out the low number of the samples analyzed (often
around five subjects, the maximum being 18) and the fact
that most of the time the subjects are young and rather thin
(body Mass Index (BMI) less than 25). In the studies selected
for this review, the reference data (gold standard) were
usually obtained by using intracortical pins [BEN 06,
FUL 97, HOU 04, REI 97] or external fixators [ALE 01,
CAP 97, CAP 96]. Although these techniques make it
possible for the skeletal movements to be directly measured,
they are invasive and susceptible to alterations in
