Biomedical Engineering Reference
In-Depth Information
damage [
6
]. Therefore, it is hypothesized that the degeneration process starts by a
labral tear and may lead to articular damages. However, different factors can be at
the origin of hip joint damage.
Although genetics, obesity, injury and infections have been identified as marginal
factors, the abnormal joint morphologies including femoroacetabular impingement
(FAI) and dysplasia are considered as the most common reasons of the cartilage and
the labrum degeneration [
7
-
9
]. Nevertheless, the exact mechanisms of degeneration
are still unknown because the development process of this pathology generally takes
a significant amount of time [
6
,
10
]. Therefore, different hypotheses were suggested
as potential factors. Some studies highlighted the physical activities that produce
high forces or stresses on the hip joint [
11
], while others focused on repetitive micro-
trauma (e.g., hip dislocation) and extreme movements [
12
,
13
]. Indeed, athletes may
practice sports which are stressful for joints (e.g., golf, hockey, football), as well
as ballet dancers who perform some excessive motions such as twisting, pivoting
and hyper-abduction/extension. Therefore, they are considered as a population at a
higher risk for developing hip labral tears or cartilage damage [
14
,
15
]. This risk
can be more important for athletes in the presence of other factors such as structural
abnormalities [
16
,
17
].
Thus, various hypotheses related to dynamics and kinematics were proposed to
explain the mechanisms of degeneration. The difficulty of establishing a link between
the causes and the degeneration of the labrum or cartilage is because they often
remain undiagnosed for a period of time [
18
]. Nevertheless, these hypotheses need
to be investigated by analyzing the hip mechanics such as the labrum and cartilages
stresses during activities [
10
].
10.1.2 Biomechanical Background
Several biomechanical studies were conducted to assess the intra-articular contacts of
the hip joint. These studies are classified in two categories: experimental and compu-
tational methods. Experimental methods based on
in vitro
and
in vivo
measurements
have been performed on cadaver hips by using different techniques (e.g., miniature
pressure transducers [
19
], pre-scaled sensitive films [
10
] and stereo-photogrammetry
[
20
]) or by using pressure transducers implanted into patients' hip prostheses [
21
].
Direct measurements presented valuable results but unfortunately these methods
present some limitations. Indeed, it is evident that the mechanical behavior of cadav-
eric and living hip tissue will be different. Moreover, the direct measurement is highly
invasive and not feasible in non-operated hips.
Nowadays, there is no direct and noninvasive method to directly assess the hip
contact. Consequently, computational methods based on analytical and numerical
models were proposed as non-invasive alternatives. Analytical models are based on
mathematical functions [
22
,
23
], while the numerical models are based on Mass-
Springs systems [
24
] or Finite Element methods [
8
,
25
]. Compared to numerical
models, analytical models are less accurate because they neglect different aspects of
