39 research outputs found
The Scapula in Musculoskeletal Modelling of Extreme Activities
This
thesis
presents
a
musculoskeletal
model
that
predicts
the
muscle
and
joint
forces
in
the
upper
limb
during
an
extreme
activity.
The
scapula
is
an
important
link
in
the
kinematic
and
dynamic
chain
of
the
upper
limb;
with
its
muscles
acting
as
the
primary
stabilisers
to
the
inherently
unstable
glenohumeral
joint,
thus
allowing
effective
transmission
of
load
through
the
kinematic
chain
of
the
shoulder.
This
bone
is
poorly
represented
in
musculoskeletal
models
during
these
activities.
Large
soft-Ââtissue
artefacts
are
a
key
reason
for
this.
The
shoulder
is
particularly
prone
to
injury
in
overhead
activities
of
the
upper
limb.
Heavily
loaded
activities
in
these
positions
are
of
interest
because
they
represent
a
limit,
in
that
few
people
are
capable
of
performing
them.
Pull-Ââups
are
a
common
training
activity
that
involve
the
movement
of
a
large
load
with
the
arms
overhead.
Predicting
the
forces
involved
in
such
an
activity
allows
a
testing
of
current
model
limits
and
hypotheses
on
the
function
and
biomechanics
of
the
scapula.
A
novel
methodology
to
track
the
dynamically
moving
scapula
is
validated
using
motion
capture
technology.
This
method
is
shown
to
improve
measurement
accuracy
when
compared
to
the
literature.
Kinematics
of
the
scapula
and
upper
limb
are
thus
measured,
presented
and
discussed
for
three
types
of
pull-Ââup
activity.
The
modelling
aspects
of
the
work
build
on
a
previous
upper
limb
model,
primarily
adapting
the
kinematics
representation.
This
better
respects
the
measured
kinematics
through
a
relaxation
of
the
closed-Ââchain
mechanism
as
well
as
improving
the
ability
to
non-Ââhomogeneously
scale
the
model.
The
inverse
dynamics
description
is
modified
to
allow
a
variable
hand
load,
muscle
wrapping
parameters
and
changed
to
prevent
sudden
unphysiological
changes
in
moment
arms
and
muscle
bounds
are
increased
to
allow
equilibrium
to
be
reached
with
the
inter-Ââsegmental
moments.
Musculoskeletal
loads
are
thus
presented
using
a
model
that
allows
the
dynamic
analysis
of
extreme
activities.
Eccentric
loading
of
the
supraspinatus,
deltoid
and
triceps
was
found
to
exist
in
potentially
vulnerable
positions,
coinciding
with
a
high
incidence
of
impingement
injury
in
pull-Ââup
type
activities.
The
glenohumeral
joint
reaction
force
is
seen
to
be
more
centralised
with
a
general
increase
in
rotator
cuff
activation,
although
teres
major
and
posterior
deltoid
seem
to
be
key
stabilisers.
Pectoralis
major
was
detrimental
to
stability,
highlighting
the
importance
of
the
scapula
in
positioning
muscles
during
overhead
activities.
Comparison
of
model
predictions
with
literature
EMG
results
show
good
agreement
Scaling and kinematics optimisation of the scapula and thorax in upper limb musculoskeletal models
Accurate representation of individual scapula kinematics and subject geometries is vital in musculoskeletal models applied to upper limb pathology and performance. In applying individual kinematics to a modelŚłs cadaveric geometry, model constraints are commonly prescriptive. These rely on thorax scaling to effectively define the scapulaŚłs path but do not consider the area underneath the scapula in scaling, and assume a fixed conoid ligament length. These constraints may not allow continuous solutions or close agreement with directly measured kinematics. A novel method is presented to scale the thorax based on palpated scapula landmarks. The scapula and clavicle kinematics are optimised with the constraint that the scapula medial border does not penetrate the thorax. Conoid ligament length is not used as a constraint. This method is simulated in the UK National Shoulder Model and compared to four other methods, including the standard technique, during three pull-up techniques (n=11). These are high-performance activities covering a large range of motion. Model solutions without substantial jumps in the joint kinematics data were improved from 23% of trials with the standard method, to 100% of trials with the new method. Agreement with measured kinematics was significantly improved (more than 10° closer at p<0.001) when compared to standard methods. The removal of the conoid ligament constraint and the novel thorax scaling correction factor were shown to be key. Separation of the medial border of the scapula from the thorax was large, although this may be physiologically correct due to the high loads and high arm elevation angles
Analysis of shoulder compressive and shear forces during functional activities of daily life
Background: Knowledge of forces acting through the glenohumeral joint during activities of daily living is a prerequisite for improving implant design and aiding rehabilitation planning. Existing data are limited by the number of activities performed and, in some cases, the lack of representation of the glenohumeral loading direction, although high shear force components may cause joint dislocation or implant loosening. This study aims to analyse shoulder compression and shear force components during essential functional activities of daily living. Methods: This is a combined modelling and experimental study. Motion data and external forces measured from 25 participants for 26 activities of daily living serve as input into an upper limb musculoskeletal model that quantifies glenohumeral loading. Findings: The shoulder contact force exceeds 50% of the body weight in 10/26 activities of daily living with a maximum contact force of 164% of the body weight (SD 69%) for a sit to stand task. The ratio of glenohumeral shear force component to compression force component exceeds 0.5 in 8/26 functional activities, with maximum ratios for reaching across the body (1.09; SD 0.41) and pick and place an everyday object (0.88; SD 0.36). Interpretation: This study demonstrates substantial loads through the glenohumeral joint during activities of daily living. The ratios of glenohumeral shear force component to compression force component are considerable when high loads act at long lever arms and at high angles of arm elevation. These glenohumeral ratios represent a key component of loading that should be considered when designing implants, surgical procedures, or rehabilitation protocols
A Subject-Specific EMG-Driven Musculoskeletal Model for the Estimation of Moments in Ankle Plantar-Dorsiflexion Movement
In traditional rehabilitation process, ankle movement ability is only qualitatively estimated by its motion performance, however, its movement is actually achieved by the forces acting on the joints produced by muscles contraction. In this paper, the musculoskeletal model is introduced to provide a more physiologic method for quantitative muscle forces and muscle moments estimation during rehabilitation. This paper focuses on the modeling method of musculoskeletal model using electromyography (EMG) and angle signals for ankle plantar-dorsiflexion (P-DF) which is very important in gait rehabilitation and foot prosthesis control. Due to the skeletal morphology differences among people, a subject-specific geometry model is proposed to realize the estimation of muscle lengths and muscle contraction force arms. Based on the principle of forward and inverse dynamics, difference evolutionary (DE) algorithm is used to adjust individual parameters of the whole model, realizing subject-specific parameters optimization. Results from five healthy subjects show the inverse dynamics joint moments are well predicted with an average correlation coefficient of 94.21% and the normalized RMSE of 12.17%. The proposed model provides a good way to estimate muscle moments during movement tasks
Validity and reliability of 3D marker based scapular motion analysis : a systematic review
Methods based on cutaneous markers are the most popular for the recording of three dimensional scapular motion analysis. Numerous methods have been evaluated, each showing different levels of accuracy and reliability. The aim of this review was to report the metrological properties of 3D scapular kinematic measurements using cutaneous markers and to make recommendations based on metrological evidence.
A database search was conducted using relevant keywords and inclusion/exclusion criteria in 5 databases. 19 articles were included and assessed using a quality score. Concurrent validity and reliability were analyzed for each method.
Six different methods are reported in the literature, each based on different marker locations and post collection computations. The acromion marker cluster (AMC) method coupled with a calibration of the scapula with the arm at rest is the most studied method. Below 90â100° of humeral elevation, this method is accurate to about 5° during arm flexion and 7° during arm abduction compared to palpation (average of the 3 scapular rotation errors). Good to excellent within-session reliability and moderate to excellent between-session reliability have been reported. The AMC method can be improved using different or multiple calibrations. Other methods using different marker locations or more markers on the scapula blade have been described but are less accurate than AMC methods.
Based on current metrological evidence we would recommend (1) the use of an AMC located at the junction of the scapular spine and the acromion, (2) the use of a single calibration at rest if the task does not reach 90° of humeral elevation, (3) the use of a second calibration (at 90° or 120° of humeral elevation), or multiple calibrations above 90° of humeral elevation
Skin-fixed scapula trackers: A comparison of two dynamic methods across a range of calibration positions
A Patient-Specific Foot Model for the Estimate of Ankle Joint Forces in Patients with Juvenile Idiopathic Arthritis
Juvenile idiopathic arthritis (JIA) is the leading cause of childhood disability from a musculoskeletal disorder. It generally affects large joints such as the knee and the ankle, often causing structural damage. Different factors contribute to the damage onset, including altered joint loading and other mechanical factors, associated with pain and inflammation. The prediction of patients' joint loading can hence be a valuable tool in understanding the disease mechanisms involved in structural damage progression. A number of lower-limb musculoskeletal models have been proposed to analyse the hip and knee joints, but juvenile models of the foot are still lacking. This paper presents a modelling pipeline that allows the creation of juvenile patient-specific models starting from lower limb kinematics and foot and ankle MRI data. This pipeline has been applied to data from three children with JIA and the importance of patient-specific parameters and modelling assumptions has been tested in a sensitivity analysis focused on the variation of the joint reaction forces. This analysis highlighted the criticality of patient-specific definition of the ankle joint axes and location of the Achilles tendon insertions. Patient-specific detection of the Tibialis Anterior, Tibialis Posterior, and Peroneus Longus origins and insertions were also shown to be important
Shoulder muscle forces during driving: sudden steering can load the rotator cuff beyond its repair limit
Driving is one of the most common everyday tasks and the rotator cuff muscles are the primary shoulder stabilisers. Muscle forces during driving are not currently known, yet knowledge of these would influence important clinical advice such as return to activities after surgery. The aim of this study is to quantify shoulder and rotator cuff muscle forces during driving in different postures.A musculoskeletal modelling approach is taken, using a modified driving simulator in combination with an upper limb musculoskeletal model (UK National Shoulder Model). Motion data and external force vectors were model inputs and upper limb muscle and joint forces were the outputs.Comparisons of the predicted glenohumeral joint forces were compared to in vivo literature values, with good agreement demonstrated (61 SD 8% body weight mean peak compared to 60 SD 1% body weight mean peak). High muscle activation was predicted in the rotator cuff muscles; particularly supraspinatus (mean 55% of the maximum and up to 164 SD 27 N). This level of loading is up to 72% of mean failure strength for supraspinatus repairs, and could therefore be dangerous for some cases. Statistically significant and large differences are shown to exist in the joint and muscle forces for different driving positions as well as steering with one or both hands (up to 46% body weight glenohumeral joint force).These conclusions should be a key consideration in rehabilitating the shoulder after surgery, preventing specific upper limb injuries and predicting return to driving recommendations
Avoiding high-risk rotator cuff loading: Muscle force during three pull-up techniques.
Heavily loaded overhead training tasks, such as pull-ups are an effective strength training and rehabilitation exercise requiring high muscle forces maintained over a large range of motion. This study used experiments and computational modeling to examine loading patterns during three different pull-up variants and highlighted risks to vulnerable musculoskeletal structures. Optical motion tracking and a force platform captured kinematics and kinetics of 11 male subjects with no history of shoulder pathology, during performance of three pull-up variants-pronated front grip, pronated wide grip, and supinated reverse grip. UK National Shoulder model (UKNSM) simulated biomechanics of the shoulder girdle. Muscle forces and activation patterns were analyzed by repeated measures ANOVA with post-hoc comparisons. Motor group recruitment was similar across all pull-up techniques, with upper limb depression occurring secondary to torso elevation. Stress-time profiles show significant differences in individual muscle patterns among the three pull-up variants, with the most marked differences between wide grip and reverse grip. Comparing across techniques, latissimus dorsi was relatively more active in wide pull-ups (PÂ <Â .01); front pull-ups favored activation of biceps brachii and brachialis (PÂ <Â .02); reverse pull-ups displayed higher proportional rotator cuff activation (PÂ <Â .01). Pull-ups promote stability of the shoulder girdle and activation of scapula stabilizers and performing pull-ups over their full range of motion is important as different techniques and phases emphasize different muscles. Shoulder rehabilitation and strength & conditioning programs should encourage incorporation of all three pull-up variants with systematic progression to provide greater global strengthening of the torso and upper limb musculature