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A biomechanical approach for dynamic hip joint
analysis
Lazhari Assassi and Nadia Magnenat-Thalmann
MIRALab, University of Geneva,Battelle, Building A, 7 Route de
Drize CH-1227 Carouge, Geneva Switzerland
{assassi,thalmann}@miralab.ch,
http://www.miralab.ch
Abstract. Hip osteoarthritis (OA) is one of the most common
formsof musculoskeletal disorders. Although, different factors were
identifiedas potential causes of the laberal tear and cartilage
degeneration, theexact pathogenesis for idiopathic OA is still not
completely delineated.Given the crucial role of the mechanical
behavior in the degenerativeprocess, analyzing the contact
mechanics in the articular layers duringactivities could contribute
to understanding the pathology. This paperpresents subject-specific
and non-invasive methods which jointly encom-pass anatomy,
kinematics and dynamics. This unique combination offersnew ways to
individualize the diagnostic by using a physically-based
sim-ulation of articular layers during motion. The simulation
results showedthat strong deformations and peak stresses were
observed in extreme hippostures. Medical experts correlated these
simulation findings with thelocations of detected abnormalities.
These observations strongly suggestthat extreme and repetitive
stresses within the joint could lead to earlyhip OA.
Keywords: Hip osteoarthritis, physically based simulation,
anatomicalmodeling, kinematics and dynamics, computer graphics
1 Introduction
The musculoskeletal system (MS) is composed of various and
heterogeneous el-ements with complex geometries, mechanical
behaviors and interactions. Thissystem provides form, support,
stability, protection and locomotion to the hu-man body. Because of
these these important functions, research into MS andand into
related pathologies is of great interest. Indeed, musculoskeletal
disor-ders (MSDs) are common causes of different pathologies and
physical disability,affecting many people across the world [1].
With the aging population, the so-cial impact and economic burden
(e.g., medical institutions and health insurancecompanies) of MSDs
are becoming more and more important to the society [2].Therefore,
a significant amount of effort has to be put into maintaining
thefunctional capabilities of the aging population to allow them to
have a betterquality-of-life. For young people the focus is on
prevention in order to reduce the
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2 A biomechanical approach for dynamic hip joint analysis
impact of MSDs and on the development of new tools which can
provide usefulinformation for medical experts to improve medical
procedures (e.g., diagnosis,surgery planning and
rehabilitation).
Among these pathologies, osteoarthritis (OA), also known as a
degenerativejoint disease, is the most common form of arthritis
(articular disease). OA ischaracterized by the breakdown or the
degeneration of the articular cartilagewhich becomes brittle and
splits. Consequently, bones are uncovered and rubagainst each
other, causing symptoms such as pain, muscle weakness and
limita-tion of movement in the joint. The most common sites of OA
include the hands,spine, hips and knees.
To understand the human joints mechanism and thoroughly
investigate thedevelopment of OA, several studies were conducted.
Different disciplines (e.g.,medicine, biology, biomechanics and
applied sciences) are involved in the ex-change and combination of
knowledge from different expertise domains. Despitethe growing
advancements, limitations still exist and much work remains to
bedone to better respond to the complexity of both the human
anatomy and med-ical procedures.
1.1 Medical context
This study focuses on the hip joint, which is crucially
important in the muscu-loskeletal system. The hip joint supports
the weight of the body in both staticand dynamic postures. It
allows for a large range of movement and for the trans-fer of high
forces between the femur and the pelvis during daily activities
[3]. Thehip joint is classified as a ball and socket joint, with
the acetabulum acting as thesocket in which the spherical femur
head articulates (see Fig.1). Both bone sur-faces are covered with
an articular cartilage which prevents direct bone-to-bonecontact
and allows a uniform pressure distribution inside the joint.
Connected tothe acetabulum rim, the acetabular labrum is a
fibrocartilaginous structure thatincreases the acetabulum depth,
grips the femoral head and provides stabilityto the hip joint. The
hip joint is moreover reinforced by ligaments [4]. Given itsrole in
the MS, the hip joint is especially vulnerable to different
pathologies andmostly OA. Although the frequency of hip OA
increases with age, OA is notexclusively an aging process as it is
also seen in younger patients [5]. In fact,the damage of the labrum
or labral tear was associated with the developmentof hip OA.
Studies have shown that a labral tear is frequently found in
youngerpatients, while for older patient the labral tear is more
often associated withchondral damage [10]. Therefore, they suppose
that the degeneration processstarts by a labral tear and may lead
to articular damages. In any case, differentfactors can be at the
origin of hip joint damage.
Although, genetics, obesity, injury and infections were
identified as marginalfactors, the abnormal joint morphologies
including femoroacetabular impinge-ment (FAI) and dysplasia are
considered as the most common reasons of thecartilage and the
labrum degeneration [68]. Nevertheless, the exact mecha-nisms of
degeneration are still unknown because the development process of
this
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A biomechanical approach for dynamic hip joint analysis 3
Fig. 1. Hip joint anatomy: bones and cartilage layers.
pathology generally takes a significant amount of time [9, 10].
Therefore, differ-ent hypotheses were suggested as potential
factors. Some studies highlighted thephysical activities that
produce high forces or stresses on the hip joint [11], whileothers
focused on repetitive micro-trauma (e.g., hip dislocation) and
extrememovements [12, 13]. Indeed, athletes may practice sports
which are stressful forjoints (e.g., golf, hockey, football), as
well as ballet dancers who perform someexcessive motions such as
twisting, pivoting and hyper-abduction/extension.Therefore, they
are considered as a population at a higher risk for developinghip
labral tears or cartilage damage [14, 15]. This risk can be more
importantfor athletes in the presence of other factors such as
structural abnormalities [16,17].
Thus, various hypotheses related to dynamics and kinematics were
proposedto explain the mechanisms of degeneration. The difficulty
of establishing a linkbetween the causes and the degeneration of
the labrum or cartilage is becausethey often remain undiagnosed for
a period of time [18]. Nevertheless, thesehypotheses need to be
investigated by analyzing the hip mechanics such as thelabrum and
cartilages stresses during activities [9].
1.2 Background
Several biomechanical studies were conducted to assess the
intra-articular con-tacts of the hip joint. These studies are
classified in two categories: experimentaland computational
methods. Experimental methods based on in vitro and invivo
measurements have been performed on cadaver hips by using different
tech-niques (e.g., miniature pressure transducers [19], pre-scaled
sensitive films [20]and stereo-photogrammetry [21]) or by using
pressure transducers implantedinto patients hip prostheses [22].
Direct measurements presented valuable re-sults but unfortunately
these methods present some limitations. Indeed, it isevident that
the mechanical behavior of cadaveric and living hip tissue will
be
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4 A biomechanical approach for dynamic hip joint analysis
different. Moreover, the direct measurement is highly invasive
and difficult toimplement in non-operated hips.
Nowadays, there is no direct and noninvasive method to directly
assess thehip contact. Consequently, computational methods based on
analytical and nu-merical models were proposed as non-invasive
alternatives. Analytical modelsare based on mathematical functions
[23, 24], while the numerical models arebased on Mass-Springs
systems [25] or Finite Element methods [7, 26]. Com-pared to
numerical models, analytical models are less accurate because
theyneglect different aspects of biomechanics such material
properties and cartilageslayers. Numerical models are widely used
in numerous domains and were thusadopted for medical applications.
Moreover, the evolution of computing power,the accessibility of
high resolution data images and segmentation techniques
re-constructing accurate 3D subject-specific models have
contributed to the growinguse of computational models. These models
were successfully used in differentapplications, such as the
analysis of symptomatic and asymptomatic hips dur-ing daily
activities [16, 17]. Nevertheless, the models used in these studies
arenot fully subject-specific. In fact, studies exploit generic
[16] or subject-specificanatomical models [17] but combine them
with generic kinematical and phys-ical data resulting from others
experimental studies [3]. Moreover, the studiedmovements are often
artificial (e.g., variation of anatomical angles) or limited
toroutine activities (e.g., walking, climbing stairs) which are
characterized by lowamplitude [16, 24]. Finally, the results of
these computational models are oftenpresented without clinical
validation [17].
Therefore, there is a lack of studies combining subject-models
(anatomical,kinematical and physical data) to analyze the hip joint
during excessive move-ments. Nevertheless, the biomechanical
modeling of a subject-specific hip jointis a difficult task and
requires an adapted pipeline.
To address this issue, this paper presents a functional approach
based onsubject-specific models to simulate the mechanical behavior
of the hip jointunder excessive movement. The analysis of the
deformation location and theassessment of the stress on the
articular layers (cartilage and labrum) duringsuch movements will
be helpful to determine whether such activities can be afactor of
hip joint degeneration.
2 Functional approach
The proposed functional approach is based on non invasive
acquisition modali-ties. Magnetic Resonance Imaging (MRI) is used
for anatomical modeling, a mo-tion capture system (Mocap) for
kinematical modeling and simulation models forphysical modeling.
Techniques which have their base in computer graphics areused to
reconstruct subject anatomical, kinematical and physical models.
Thesemodels are used to set up the simulation model to achieve
accurate physically-based simulation of the hip joint.
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A biomechanical approach for dynamic hip joint analysis 5
2.1 Anatomical modeling
Given the numerous differences that exist between individuals,
the use of subject-specific anatomical models is of paramount
importance to clinical diagnosis. Toreconstruct the subject models,
the first step is to select medical modalities thatallow the best
imaging of the structures to model. Compared to other
modalities(e.g., Computed Tomography (CT)), MRI is a good choice
for musculoskeletalimaging, because it offers the simultaneous
examination of soft and bony tissue.The next step consists of
devising the best imaging protocol to satisfy imagingand clinical
constraints. This is achieved by an adapted MRI protocol basedon an
adequate trade-off between the image quality and acquisition time
[27].From the acquired medical images, a segmentation approach
needs to be usedto identify the anatomical structures of interest.
Despite the numerous studies,a universal segmentation approach has
not yet been proposed, due to noise andartifacts inherently present
in medical images. To overcome this problem, thesegmentation needs
to be regulated by the introduction of constraints and
prior-knowledge.
A segmentation approach based on robust deformable models is
devised toaccurately segment bones and soft tissue of the hip
[2830]. In this approach, eachmodels vertex is considered as a
particle that is subjected to various internal andexternal forces.
Internal forces constrain the shape evolution, while the
externalforces attract the shape toward the anatomical boundaries.
The segmentationevolution is then performed by the integration of a
system of discrete differentialequations. A stable implicit
integration scheme [31] based on a conjugate gradienttechnique is
used. To avoid the inter-penetration of the different evolving
shapes,collisions methods are implemented as well as
post-processing techniques [32].Figure 2 shows various results
(bone, cartilage and muscles) of the segmentationapproach.
Fig. 2. MRI dataset volume used to segment hip joint anatomical
structures (bonesand cartilage) and leg muscles.
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6 A biomechanical approach for dynamic hip joint analysis
Once segmented, models need to be converted to volumetric meshes
in orderto be used in physically-based simulations. Various methods
are proposed to gen-erate volumetric meshes based on
tetrahedral/hexahedral (Tet/Hex) elements.Nevertheless, Tet
elements are more preferable than Hex elements for meshingcomplex
geometry. Three main approaches are commonly used: an
octree-basedmethod [33], advancing front method [34] and a method
based on a Delaunaycriterion [35]. Despite the performance of
classical approaches, the quality of theresulting meshes is not
totally guaranteed, especially for complex geometries.In fact, a
large number of Tet elements (potentially with a low quality such
asslivers) is often generated.
To generate Tet meshes, meshing approaches based on 2D and 3D
deformablemodels are proposed in this work. For models which can be
approximated bytheir medial surface (MS), a 2D deformable
medial-axis based approach [36,37] is used. This approach exploits
the thickness information included into themedial surface to
generate Tet meshes. For more complex shapes, where the MSis not
easily computed, a 3D deformable models approach [38] based on
octreesubdivision with a body centered cubic lattice [39] of the
surfacic mesh is used.These approaches produce Tet meshes of
satisfactory quality (with respect tothe dihedral angle and aspect
ratio) and complexity (low number of Tet) whichensure the
simulation accuracy and stability (see Fig.3).
Fig. 3. a) Tet meshing of the femoral cartilage based on the use
of the 2D deformablemedial surface approach where color present the
thickness of the model. b) Tet meshof Acetabulm cartilage and
Labrum generated by the 3D deformable models approach.
To set up the mechanical model, appropriate mechanical
properties andboundary conditions are assigned to mesh elements.
These parameters are de-fined according to the tissue properties
and their attachments.
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A biomechanical approach for dynamic hip joint analysis 7
2.2 Kinematical modeling
The description of the skeletal system movement involves the
definition of specificsets of axes for each bone segment [40]. This
is achieved by setting a geometricrule that constructs the axes by
using selected anatomical landmarks defined onthe reconstructed 3D
surface of the subjects hip and femur bones. The samebone models
are used to compute the hip joint center (HJC) position [41].
The subjects movements are then recorded with an optical motion
capturesystem (Vicon MX 13i, Oxford Metrics, UK) using 8 infrared
cameras, samplingat 120 Hz and tracking markers in a 45.3 m3
measurement volume (3.6x4.2x3m) (see Fig.4). The set of spherical
markers (7 mm) are placed according toan appropriate protocol to
ensure their visibility to the cameras [20]. Unlikeother motion
acquisition devices (e.g., intra-cortical pins [42], external
fixators[43], fluoroscopy [44]), the optical system is not invasive
and allows the record-ing of larger ranges of motion. However, due
to muscle activities and inertialmovements, the skin markers move
over the underlying structures. This rela-tive movement represents
an artifact, typically referred to as soft tissue artifact(STA)
[45]. Consequently, rigid motion of the bone segment cannot be
robustlyestimated from the markers trajectories. Correcting these
errors is thus necessaryfor clinical relevance.
To minimize STA, a nonlinear optimization algorithm [46] is used
to find,for each segment and for each frame of movement, the best
rigid transformationthat minimizes the error made globally on all
the markers. Since it was observedthat joint dislocation may occur
due to STA, kinematic constraints allowingsome shifts at the joint
are also applied (see Fig.4 (c) and (d)). The proposedapproach [47,
48] ensures an accurate kinematical modeling for the hip joint
[27].
Fig. 4. a) Movement recording by using the Mocap system and b)
computed subjectposture. c) An Error position (dislocation) due to
the STA and d) a corrected positionby applying the optimization and
constraint approach.
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8 A biomechanical approach for dynamic hip joint analysis
2.3 Physical modeling
In addition to anatomical and kinematical models, the forces
acting on the hipjoint as well as a simulation model are needed to
achieve physically-based sim-ulation of the hip joint.
Hip Loads estimation: Hip forces or loads were measured in the
literatureexperimentally by using telemetric implants [3, 49].
Unfortunately this in vivomethod cannot be used in a non operated
hip. Moreover, the resulting datacannot be considered as
subject-specific. In fact, measured forces concern agedpersons who
underwent hip replacement surgery (cartilage and labrum
removed).Finally, the studied movements are limited to routine
activities which are notuseful in our case study.
To overcome this problem, a neuromuscular simulation [5052] is
exploited asan alternative. This kind of simulation offers the
possibility to estimate internalparameters (e.g., muscle
activations, forces) by analyzing the subject kinematicsand
kinetics during the performance of activities. Such simulations
were used indifferent applications like gait analysis [53],
simulation of neuromuscular abnor-malities [54], or design of
ergonomic furniture [55]. In neuromuscular simulations,several sets
of data measured experimentally (e.g., motion capture, force
platesand Electromyography (EMG)) are exploited into a specific
process [56].
In this study, a neuromuscular model is adopted [57] to analyze
the dynamicsimulations of movements. A specific pipeline is
required to estimate forces act-ing on the hip joint. The first
step consists of scaling the generic model to matchthe
anthropometry of the subject-specific anatomical model. The
achieved scal-ing is based on a hybrid method using measured data
resulting from differentapproaches (3D body scan model [48], 3D
anatomical models, MRI data and ini-tial marker positions). These
sets of data are combined and processed to realizean anisotropic
scaling by calculating the scaling factors for each part of the
body.From the resulting model and motion capture data, the joint
coordinate values(e.g., joint angles) that reproduce the subject
movement (markers positions) arecalculated by using an inverse
kinematic (IK) approach (see Fig.5).
To complete the process, the ground reaction force (GRF) is
required. In ourcase, a computational method based on Newtonian
analysis is used to replace theunavailability of the force plates
data. A dynamic 3D model using the motioncapture data and the
scaling model data (body segment weights) is used to esti-mate GRF.
This approach is conceivable due the nature of studied
movements.Indeed, the studied movements are characterized by the
static foot position ofone leg and the air position of the other
leg (e.g., arabesque movement), or staticposition of both feet
(e.g., bending movement). Estimated GRF FLG of the legacting on the
ground is expressed as:
i
Fi = FLG +m.g =i
mi.ai (1)
where m is the subject mass, g denotes the gravity vector, mi
and ai are themasses and the accelerations of the body segments,
respectively.
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A biomechanical approach for dynamic hip joint analysis 9
Based on kinematical data, the body segments velocity vi and
accelerationai are computed from their mass center positions
pi:
vi = (pi+1 pi)/t (2)
ai = (vi+1 vi)/t (3)
where t denotes the time step.The force contact point pLG is
finally computed by using the moment equa-
tion: i
Mi = FLG pLG +m.g pmc =i
mi.ai pi (4)
where pmc =
imi.pi/m is the mass body center.The output of IK and the
computed GRF are used as input in an inverse
dynamic (ID) procedure to compute muscle activation, which are
involved in theproduced movement. Finally, the results of the ID
step are used in the analyzeprocedure step to compute forces acting
upon joints. The resulting forces areexported from the
neuromuscular coordinate system to the hip joint coordinatesystem
which is used in the physically-based simulation.
Fig. 5. IK and ID steps of the neuromuscular simulation:
Computation of the move-ment with estimated GRF and muscles
activation presented by curves.
Simulation model: A physical simulation model is required to
compute the de-formation of the mechanical objects. However,
different criteria should be takeninto account to achieve an
accurate simulation, which faithfully reflects the me-chanical
behavior of biological tissues. Indeed, biomechanical constraints
suchas the nonlinearity, large displacements and deformations of
soft tissue have to
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10 A biomechanical approach for dynamic hip joint analysis
be considered. Different models based on mass-spring systems
[25], the FiniteElement Method [16] and Finite Volume Method [58]
were used to simulate thedeformations of soft tissue.
To simulate the mechanical behavior of deformable objects, our
simulationmodel [37, 38] is based on a fast 1st-order Finite
Element system implementa-tion, which offers a good trade-off
between accuracy and computation speed.This model based on a
particle-system representation, allows for the
accuraterepresentation of anisotropic nonlinear viscoelastic
deformation models and isparticularly well suited for modeling the
behavior of highly deformable materi-als. Thanks to its lumped mass
approximation, such models can be integratedwith high-efficiency
numerical integration methods typically used in particle sys-tems,
as well as easy and efficient integration of collision effects and
geometricalconstraints. Moreover, an efficient numerical
integration technique is used to pro-vide good performance in the
computation of these mechanical models, both inthe context of
dynamic animation and quasi-static relaxation. Concretely
speak-ing, the different techniques considered to build an
efficient simulation model are[5961]:
A fast 1st-order Finite Element implementation system for non
linear be-havior.
3D specific improvements of the Co-rotational element
transformation whichis appropriate to simulate anisotropic and
isotropic materials and allow ac-curate computation of the large
deformations.
Pseudo-Dynamic Stop-and-Go relaxation for fast convergence for
large dis-placements.
Modeling elasticity strain-stress relationships with polynomial
formulationsfor simple and efficient modeling of the non-linear
material behavior.
Efficient collision processing techniques based on incremental
computationmethod.
The developed simulation model is implemented in a framework
offering anadequate compromise between efficiency and versatility.
The accuracy of the me-chanical model has been validated through
simulation comparisons with publiclyavailable Finite Element
packages (FEBio [62], SOFA[63] and Code-Aster [64],and has shown to
offer similar accuracy (see Fig.6). Meanwhile, computationtimes are
kept very low (a few seconds per frame) thanks to ad-hoc tuning
ofthe numerical integration parameters, as well as to a specific
handling of colli-sions which ensures high simulation
stability.
Finally, the resulting aforementioned models (meshes,
kinematics, loads, etc.)are used as input for the simulation model
to analyze the mechanical behaviorof the subjects hip joint.
3 Clinical Analysis
To validate the simulation results, a clinical study based on
morphological andradiological analysis was performed by medical
experts. To eliminate the typical
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A biomechanical approach for dynamic hip joint analysis 11
Fig. 6. Accuracy comparison between the developed model and
available FEM models.Computation of deformation by applying loads
on a) a simple object, b) 2 objects andc) a generic hip joint.
abnormalities of the hip joint that could lead to hip joint
degeneration, a mor-phological analysis was performed to evaluate
the prevalence of the subjects hipjoint. To this end, standard
morphological measurements were performed [65,8] (see Fig.7). The
first measurement consists of computing the depth of theacetabulum.
If the acetabulum is too deep, the excessive over-coverage of
thefemoral head by the acetabulum causes abutment against the
acetabular rim.The depth is defined as the distance in mm between
the center of the femoralhead (O and the line ARPR connecting the
anterior (AR) and posterior (PR)acetabular rim. The value is
considered as positive and normal if O is lateralto the line AR PR.
The second measure related to the femur geometry isthe femoral
alpha () neck angle. A non-spherical head damages the
articularcartilages by abutting the acetabulum rim. The angle is
defined by the angleformed by the line O O connecting the center of
the femoral head (O) andthe center of the femoral neck (O) at its
narrowest point; and the line O Pconnecting O and the point P where
the distance between the bony contour ofthe femoral head and O
exceeds the radius (r) of the femoral head. Deviationfrom the
normal geometry is usually associated with larger angles (>
60).
Based on subject-specific data (MRI and 3D bones
reconstruction), thesestandard measurement methods were numerically
implemented, improving the(subjective) reading of medical images.
The dancer hip was thus analyzed, ac-cording to those 2 anatomical
parameters. No morphological abnormalities weredetected and it was
concluded that the measured hips have an average positivedepth
(left hip: 8.16 mm, right hip: 7.89 mm) and an average angle in
thenormal range (36.15 < < 54.43). The results were validated
by radiologicalexperts.
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12 A biomechanical approach for dynamic hip joint analysis
Fig. 7. Standard morphological measurement based on
subject-specific 3D models andMRI data. Devision of the acetabulum
in 8 sectors for radiological analysis.
The same radiological experts performed consensus readings of
the subjectsMR images [5]. The acetabular cartilage and labral
abnormalities were assessedqualitatively. For this subject,
acetabular and labral lesions were diagnosed inthe posterior part
of the acetabular rim (see Fig.8). To describe the exact lo-cation
of the lesions, the acetabulum was divided into 8 sectors (1:
anterior, 2:anterosuperior, 3: superior, 4: posterosuperior, 5:
posterior, 6: inferoposterior, 7:inferior, 8: anteroinferior), as
depicted in Figure 7.
Fig. 8. Radiological analysis: Diagnosis of acetabular and
labral lesions in the posteriorpart of the acetabular rim.
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A biomechanical approach for dynamic hip joint analysis 13
4 Biomechanical analysis of professional ballet dancer hip
joint
This study was conducted in collaboration with doctors from the
departmentof Radiology and department of Orthopedic Surgery of the
University Hospitalof Geneva and female professional ballet dancer
from the ballet of the GreatTheater of Geneva.
The developed approach is used to analyze the mechanical
behavior of artic-ular layers of a dancers hip joint. The choice of
subject is justified by the natureof practiced movements. Indeed,
several dance movements such as Grand-Plie(bending), Circumduction,
Arabesque, Developpe-Lateral (lateral leg bench) andDeveloppe-Avant
(forward leg bench) require intensive hip flexion and/or abduc-tion
with rotation. Given the subject feedback, such movements are
recognizedas excessive. Therefore, the daily practice of these
exercises is assumed to bea potential cause which can contribute to
an early hip osteoarthritis for thesubject.
Subject-specific kinematics and kinetics of the simulated
movements are dis-cretized into several frames. Femoral kinematics
and joint contact forces areexpressed according to standard hip
joint anatomical axes (6 degrees of free-dom) with origin located
at the center of the femoral head [40]. The 3 rotationangles and 3
load components are defined along these three anatomical axes
(seeFig.9).
Fig. 9. Loads (Blue axis) and movement (Flexion/Extension (Y:
green axis), Adduc-tion/Abduction (X: red axis) and
Internal/External rotation (Z: yellow axis))are ex-pressed in hip
joint anatomical axes.
The range of motion in the subject hip joint of the simulated
dancing move-
ments and the estimated GRF magnitude(GRF =GRF 2x +GRF
2y +GRF
2z )
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14 A biomechanical approach for dynamic hip joint analysis
are presented in Table 1. Movements concern the leg in elevated
position (exceptGrand-Plie) and are expressed with anatomical
angles (Flexion/Extension, Ad-duction/Abduction and
Internal/external rotation) according to the hip jointaxes. Each
movement is presented with an average and a standard deviation(SD)
angle. To compare the amplitude of dancing and normal movements,
walk-ing angles during stance phase are presented. The GRF concerns
the second leg(foot on the ground). The forces are presented with
average and SD values andexpressed as a percentage of the subjects
body weight (% BW).
Table 1. Range of motion of the left hip joint and estimated GRF
magnitude on theright foot. Angles are reported in deg and force in
newton (N).
Movement Flex/Ext() Abd/Add() Int/Ext rot() GRF=% BW (N)
Arabe. 0/0/36.1 9.8 0/0/32.1 6.6 0/0/79.5 6.4 97.4 2.0
Circum. 52.4 26.1/0/0 0/0/37.9 24.8 0/0/22.5 9.1 95.9 7.8
Dev.Av. 71.3 17.1/0/0 0/0/22.2 7.9 0/0/34.8 8.1 95.4 10.4
Dev.Lat 72.9 35.8/0/0 0/0/54.5 15.3 0/0/11.3 28.5 96.0 4.6
Gra.Pl. 70.9 49.4/0/0 0/0/8.7 1.7 0/0/1.5 7.1 48.0 3.1
Walk.S-P 30.6 10.9/0/0 0/0/12.2 3.6 0/0/10.4 6.1 95.7 8.3
As shown in Table 1, dancing involves intensive hip flexion and
abduction(except the arabesque where the hip is in extension).
Globally, estimated loadsdepend on movements (angles). Figure 10
shows the evolution of loads accordingto the angles of bending
movement.
Fig. 10. Curves of angles and loads for Bending movement. Angles
are expressed indegree and loads in %BW.
To build the biomechanical model, the mechanical properties of
soft tissueare considered. Given (i) the significant difference of
the Young modulus between
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A biomechanical approach for dynamic hip joint analysis 15
the labrum, articular(20 MPa), cartilage (12 MPa) and cortical
bone (17GPa) [7]and (ii) the small mechanical role of trabecular
bone [17], bone deformation willbe minimal (0.01-0.1%) compared to
cartilage deformation [66]. Therefore, it ismore convenient to
consider bones as rigid and surfacic structures to
reasonablysimplify the model and considerably reduce computation
times [16].
Then, the subject-specific deformable models of the soft tissue
consist of twotetrahedral meshes (see Fig.3). The first mesh (18k
Tet) is composed of boththe labrum and acetabulum cartilages, where
the tetrahedral elements of eachcartilage are defined with
mechanical properties specific to the tissue type. Thesecond mesh
(7k Tet) exclusively represents the femoral cartilage. Such
modeling(2 meshes instead of 3) reduces the computation of
collision detection. Externalsurfaces of tetrahedral meshes are
extracted to define the boundary conditionsin the simulation model:
vertices of the first mesh attached to the hip bone areconsidered
as fixed, while those of the second mesh attached to the femur
willtransfer loads. Since soft tissues are characterized by large
deformations, whichare tackled by the used simulation model, mesh
elements of the labrum, ac-etabulum and femoral cartilages are
parameterized with appropriate mechanicalbehavior [67, 68].
The physically based simulation exploits this model to analyze
articular lay-ers (labrum, acetabular and femoral cartilage)
deformations. For each frame ofsimulated movements, the contact and
the peak stress are computed. The stressrefers to the stress along
the direction of the maximal compression. To analyzethe
intra-articular contacts and especially the labrum deformation,
peak stresseson each layer are reported. Individual analysis of
stresses makes it possible toquantify the load absorbed by labrum
to caracterize its role in the hip jointstructure [69].
On the other hand, the simulation calculates the peak stress
locations, whichare also of paramount importance in the analysis.
Indeed, such examinationprovides insight into which region of
labrum or cartilage is subjected to highstress during movement in
order to investigate regions susceptible to be damaged.
The simulated movements showed that usually the peak stresses
were locatedin the superior and postero-superior (respectively
positions 3 and 4 in Figure 7)parts of the labrum and actebuar
cartilage (see Fig.11 and Fig.12). Some otherparts exhibited high
stress but not in the same significant way.
5 Discussion and conclusion
The morphological measurements were analyzed by a radiological
expert. Theresults of morphological analysis showed that no values
indicating potential mor-phological problems were reported. FAI
(Cam or pincer) morphology was not ob-served, nor was possible hip
dysplasia. However radiological analysis indicatedthat lesions were
observed in the superior part of the labrum and acetabular
car-tilage. By putting in correspondence the location of the
lesions with the stressanalysis of the simulation, high stresses
were located in the superior area of theacetabular rim (see
Fig.12), which corresponds to the localization of diagnosed
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16 A biomechanical approach for dynamic hip joint analysis
Fig. 11. Distribution of the stress on actebular and femoral
cartilage (without thelabrum). Peak stress (red color) on position
3 and 4 of acetabular rim.
lesions (see Fig8). Then, an assumption is that excessive
movements may explainthese lesions of idiopathic OA. This
assumption can be supported by the natureof the dancers
movements.
Fig. 12. Location of the stress peak (red color) observed during
simulation in thesuperior and postero-superior parts of the labrum
and actebuar cartilage.
Nevertheless additional work is required to assess some
simulation compo-nents in order to fully accept the results. In
fact, the accuracy of the differentstages involving anatomy,
kinematics and dynamics can have some impact onthe quality of the
simulation. To improve the significance of the results, analysisof
more subjects is planned.
-
A biomechanical approach for dynamic hip joint analysis 17
6 Acknowlegment
This work is supported by the Swiss National Research Foundation
(SNSF:project 200020-132584/1). We are grateful to the University
Hospital of Genevaand the ballet dancers of the great theater of
Geneva for their collaboration.
References
1. Arthritis foundation, http://www.arthritis.org2. Bevan, S.,
McGee, R., Quadrello, T.: Key findings of the fit for work europe
report
on musculoskeletal disorders and work. In: Occupational Health
at Work 2009. vol.6, pp. 3030. The At Work Partnership (2009)
3. Bergmann, S.G., Deuretzbacher, G., Heller, M., Graichen, F.,
Rohlmann, A.,Strauss, J., Duda,J.N.: Hip contact forces and gait
patterns from routine activi-ties. J. Biomech. 34, 859871
(2001)
4. Standring, S.: Grays anatomy: The anatomical basis of
clinical practice. 39th Ed.,Elsevier Churchill Livingstone
(2005)
5. Duthon, V., Menetrey, J., Kolo-Christophe, F., Charbonnier,
C., Duc, S., Pfirrmann,C., Magnenat-Thalmann, N., Becker, C.b
Hoffmeyer, P.: Professional dancers hip:Correlation of clinical and
mri findings. In: Swiss Med Wkly, EMH. vol. 139, pp.2324.
(2009)
6. Kelly, B.T., Weiland, D.E., Schenker, M.L., Philippon, M.J.:
Arthroscopic labralrepair in the hip: surgical technique and review
of the literature. Arthroscopy. 21,496504 (2005)
7. Russell, M., Shivanna, K., Grosland, N., Pedersen,D.:
Cartilage contact pressureelevations in dysplastic hips: a chronic
overload model. J. Orthop. Surg. Res. 1,169177 (2006)
8. Tannast, M., Goricki, D., Beck, M., Murphy, S., Siebenrock,
K.: Hip damage occursat the zone of femoroacetabular impingement.
J. Clin. Orthop. Relat. 466, 273280(2008)
9. Macirowski, T., Tepic, S., Mann, R.W.: Cartilage stresses in
the human hip joint.:J. Biomech. Eng., 116, 1018 (1994)
10. McCarthy, J.C., Noble, P.C., Schuck, M.R., Wright, J., Lee,
J., Waterman, M.S.:The Otto E Aufranc Award the role of labral
lesions to development of early degen-erative hip disease. Clin.
Orthop. 393, 2537 (2009)
11. Pool, A.R.: Imbalances of anabolism and catabolism of
cartilage matrix compo-nents in osteoarthritis. In: V.M. Goldberg
K.E. Kuettner (eds.). Osteoarthritic Dis-order, pp. 247260.
Rosemont, Illinois: American Association of Orthopaedic Sur-geons
(1995)
12. Narvani, A.A., Tsiridis, E., Tai, C.C., Thomas, P.:
Acetabular labrum and its tears.Br. J. Sports Med. 37, 207211
(2003)
13. Narvani A.A., Tsiridis, E., Kendall. S., Chaudhuri, R.,
Thomas, P.: A preliminaryreport on prevalence of acetabular labrum
tears in sports patients with groin pain.Knee Surg. Sports
Traumatol Arthrosc. 11, 403408 (2003)
14. Binningsley, D.: Tear of the acetabular labrum in an elite
athlete. Br. J. SportsMed. 37, 8488 (2003)
15. Bharam, S.: Labral tears, extra-articular injuries, and hip
arthroscopy in the ath-lete. Clin. Sports Med. 25, 279292
(2006)
-
18 A biomechanical approach for dynamic hip joint analysis
16. Chegini, S., Beck, M., Ferguson, S.: The effects of
impingement and dysplasia onstress distributions in the hip joint
during sitting and walking: A finite elementanalysis. J. Orthop.
Res. 27, 195201 (2008)
17. Anderson, A.E., Ellis, B.J., Maas, S.A., Peters, C.L.,
Weiss,J.A.: Validation offinite element predictions of cartilage
contact pressure in the human hip joint. J.Biomech. Eng. 130, 110
(2008)
18. Byrd, J.W., Jones, K.S., Smith, T.F., Waterman, M.S.:
Prospective analysis of hiparthroscopy with 2-year follow-up.
Arthroscopy. 16, 578587 (2000)
19. Brown, T.: In vitro contact stress distributions in the
natural human hip. J.Biomech. 16, 373384 (1983)
20. Macirowski, T., Tepic, R.M.S.: Cartilage stresses in the
human hip joint. J.Biomech. Eng. 116, 1018 (1994)
21. Ahmad, M.C., Cohen, Z., Levine, W., Ateshian, G., Mow, V.:
Biomechanical andtopographic considerations for autologous
osteochondral grafting in the knee. Amer.J. Sport Med. 29, 201206
(2001)
22. Hodge, W., Carlson, K., Fijan, R., Burgess, R., Riley, P.,
Harris, W., Mann R.:Contact pressures from an instrumented hip
endoprostheses. J. Bone and Joint Surg.71, 13781386 (1989)
23. Mavcic, B., Pompe, B., Antolic, V., Daniel, M., Iglic, A.,
Kralj-Iglic, V.: Mathe-matical estimation of stress distribution in
normal and dysplastic human hips. J.Orthop. Res. 20, 10251030
(2002)
24. Xishi, W., Tianying, W., Fuchuan, J., Yixiang, D.: The hip
stress level analysis forhuman routine activities. Biomed. Eng.
Appl., Bas. Com. 17, 4348 (2005)
25. Maciel, A., Sarni, S., Boulic, R., Thalmann, D.: Stress
distribution visualizationon pre- and post-operative virtual hip
joint. In: Proc. Comp. Assist. Orthop. Surg.(CAOS05). pp. 298301.
(2005)
26. Ahmet, C., Vahdet, U., Recep, K.: Three-dimensional anatomic
finite element mod-elling of hemi-arthroplasty of human hip joint.
Trends Biomat. Artif. Orga. 21, 6372(2007)
27. Magnenat-Thalmann, N., Charbonnier, C., Schmid, J.:
Multimedia application tothe simulation of human musculoskeletal
system: A visual lower limb model frommultimodal captured data. In:
Proc. IEEE Int. Workshop in Sig. Proc., pp. 520525.(2008)
28. Schmid, J., Magnenat-Thalmann, N.: Mri bone segmentation
using deformablemodels and shape priors. In: Proc. Int. Conf. med.
imag. comp. comp. ass. in-ter.(MICCAI), vol. 5241, pp. 119126.
Springer-Verlag, Heidelberg(2008)
29. Gilles, B., Magnenat-Thalmann, N.: Musculoskeletal mri
segmentation using multi-resolution simplex meshes with medial
representations. Med. Image Anal. 14, 291302 (2010)
30. Schmid, J., Kim, J., Magnenat-Thalmann, N.: Robust
statistical shape models formri bone segmentation in presence of
small field of view. Med. Image Anal. 15,155168 (2011)
31. Volino, P., Magnenat-Thalmann, N.: Implicit midpoint
integration and adaptivedamping for efficient cloth simulation.
Comput. Anim. Virt. World. 16, 163175(2005)
32. Schmid, J., Sandholm, S., Chung, F., Thalmann, D.,
Delingette, H., Magnenat-Thalmann, N.: Musculoskeletal simulation
model generation from mri datasets andmotion capture data. In:
Recent advances in the 3D Physiological Human. pp. 320.Springer,
Heidelberg (2009)
33. Shephard, M., Georges, M.: Three-dimensional mesh generation
by finite octreetechnique. Int. J. Num. Meth. Eng. 32, 709749
(1991)
-
A biomechanical approach for dynamic hip joint analysis 19
34. Lohner, R.: Progress in grid generation via the advancing
front technique. Eng.Comput. 39, 501511 (1996)
35. Alliez, P., Cohen-Steiner, D., Yvinec, M., Desbrun, M.:
Variational tetrahedralmeshing. In: SIGGRAPH05. pp. 193204.
(2005)
36. Assassi, L., Guillard., G., Gilles., B., Magnenat-Thalmann,
N.: Volumetric meshesbased on medial representation for medical
applications. In: Proc. Comp. Assist.Orthop. Surg. (CAOS07). pp.
259262. (2007)
37. Assassi, L., Charbonnier, C., Schmid, J., Volino, P.,
Magnenat-Thalmann, N.: Frommri to anatomical simulation of the hip
joint. Comput. Anim. Virt. World. 20, 5366(2009)
38. Magnenat-Thalmann, N., Schmid, J., Assassi, L., Volino, P.:
A comprehensivemethodology to visualize articulations for the
physiological human. In: Cyberworlds.IEEE Computer Society. pp. 18.
(2010)
39. Molino, N., Bridson, R., Teran, J., Fedkiw, R.: A
crystalline red green strategyfor meshing highly deformable object
with tetrahedral. In: Proc. 12th Int. MeshRoundt. pp. 103114.
(2003)
40. Wu, G., Siegler, S., Allard, P., Kirtley, C., Leardini, A.,
Rosenbaum, D., Whittle,M., DLima, D., Cristofolini, L., Witte, H.,
Schmid, O., Strokes, I.: ISB recommen-dation on definitions of
joint coordinate system of various joints for the reporting ofhuman
joint motion- part I: Ankle, hip and spine. J. Biomech. 35, 543548
(2002)
41. Gilles, B., Kolo-Christophe, F., Magnenat-Thalmann, N.,
Becker, C., Duc, S., Men-etrey, J., Hoffmeyer, P.: Mri-based
assessment of hip joint translations. J. Biomech.12, 12011205
(2009)
42. Benoit, D., Ramsey, D., Lamontagne, M., Xu, L., Wretenberg,
P., Renstroem, P.:Effect of skin movement artifact on knee
kinematics during gait and cutting motionsmeasured in vivo. Gait
and Posture. 24, 152164 (2006)
43. Cappozzo, A., Catani, F., Leardini, A., Benedetti, M.,
Croce, U.D.: Positionand orientation in space of bones during
movement: experimental artefacts. Clin.Biomech. 11, 90100
(1996)
44. Garling, E., Kaptein, B., Mertens, B., Barendregt, W.,
Veeger, H., Nelissen, R.,Valstar, E.: Soft-tissue artefact
assessment during step-up using fluoroscopy andskin-mounted
markers. J. Biomech. 40, 1824 (2007)
45. Kepple, T., Arnold, A., Stanhope, S., Siegel, K.: Assessment
of a method to esti-mate muscle attachments from surface landmarks:
a 3d computer graphics approach.J. Biomech. 27, 365371 (1994)
46. Lawrence, C., Tits, A.: A computationally efficient feasible
sequential quadraticprogramming algorithm. SIAM J. Optim. 11,
10921118 (2001)
47. Charbonnier, C., Lyard, E., Magnenat-Thalmann, N.: Analysis
of extreme hipmotion in professional ballet dancers. In: Proc. of
the 10th Int. Symp. 3D Anal.Human Mov. Amsterdam, Netherlands
(2008)
48. Charbonnier, C., Assassi, L., Volino, P., Magnenat-Thalmann,
N.: Motion studyof the hip joint in extreme postures. The Visual
Computer. 25, 873882 (2009)
49. Park, S., Krebs, D., Mann, R.: Hip muscle co-contraction:
evidence from concurrentin vivo pressure measurement and force
estimation. Gait and Posture. 10, 311322(1999)
50. Delp, S., Loan, J., Hoy, M., Zajac, F., Topp, E., Rosen J.:
An interactive graphics-based model of the lower extremity to study
orthopaedic surgical procedures. IEEETrans. Biomed. Eng. 37, 757767
(1990)
51. Damsgaard, M., Rasmussen, J., Christensen, S., Surma, E., de
Zee, M.: Analysisof musculoskeletal systems in the anybody modeling
system. Simulation ModellingPractice and Theory. 14, 11001111
(2006)
-
20 A biomechanical approach for dynamic hip joint analysis
52. Erdemir, A., McLean, S., Herzog, W., van den Bogert, A.:
Model based estimationof muscle forces exerted during movements.
Clin. Biomech. 22, 131154 (2007)
53. Piazza, S., Delp, S.: The influence of muscles on knee
flexion during the swingphase of gait. J. Biomech. 29, 723733
(1996)
54. Fox, M., Reinbolt, J., Unpuu, S., Delp, S.: Mechanisms of
improved knee flexionafter rectus femoris transfer surgery. J.
Biomech. 42, 614619 (2009)
55. Rasmussen, J., de Zee, M.: Design optimization of airline
seats. SAE Inter. J.Passenger Cars-electronic and electrical
systems. 1, 580584 (2008)
56. Sandholm, A., Pronost, N., Thalmann, D.: Motionlab: A matlab
toolbox for ex-tracting and processing experimental motion capture
data for neuromuscular simu-lations. In: Proc. the Second 3D
Physiological Human Workshop (3DPH). vol. 5903,(2009)
57. Delp, S., Anderson, F., Arnold, A., Loan, P., Habib, A.,
John, C., Guendelman,E., Thelen, D.: Opensim: Open-source software
to create and analyze dynamic sim-ulations of movement. IEEE Trans.
Biom. Eng. 54, 19401950 (2007)
58. Irving, G., Teran, J., Fedkiw, R.: Invertible finite
elements for robust simulationof large deformation. In: ACM
SIGGRAPH04. ACM Press, vol. 131, pp. 131140.(2004)
59. Volino P., Magnenat-Thalmann, N.: Implicit Midpoint
Integration and AdaptiveDamping for Efficient Cloth Simulation.
Comp. Anim. Virt. Worlds. 16, 163175(2005)
60. Volino P., Magnenat-Thalmann, N.: Stop-and-Go Cloth Draping.
Vis. Comput. 23,669677 (2007)
61. Volino P., Magnenat-Thalmann, N., Faure, F.: A Simple
Approach to NonlinearTensile Stiffness for Accurate Cloth
Simulation. In: ACM Trans. on Graph.. ACMPress, vol. 28, pp.
105116. (2009)
62. Finite Element Software: FEBio,
http://mrl.sci.utah.edu/software.php63. SOFA:Simulation
Open-Framework Architecture, http://www.sofa-framework.
org
64. Finite Element Software:Code-Aster,
http://www.code-aster.org65. Pfirrmann, C., Mengiardi, B., Dora,
C., Kalberer, F., Zanetti, M., Hodler, J. : Cam
and pincer femoroacetabular impingement: Characteristic mr
arthrographic findingsin 50 patients. J. Radiol. 240, 778785
(2006)
66. Dalstra, M., Huiskes, R., Van-Erning, L.: Development and
validation of a three-dimensional finite element model of the
pelvic bone. J. Biomech. Eng. 117, 272278(1995)
67. Ferguson, S., Bryant, J., Ito, K.: The material properties
of the bovine acetabularlabrum. J. Orthop. Res. 19, 887896
(2001)
68. Park, S., Hung, C., Ateshian, G.: Mechanical response of
bovine articular carti-lage under dynamic unconfined compression
loading at physiological stress levels.Osteoart. Cart. 12, 6573
(2004)
69. Henak, C.R., Ellis, B.J., Harris, M.D., Anderson A.E.,
Peters C.L., Weiss J.A.:Role of the acetabular labrum in load
support across the hip joint. J. Biomech. 44,22012206 (2011)