biomechanics of musculoskeletal system.pdf
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Biomechanics of
Musculoskeletal System
Strahinja Dosen, [email protected]
University of Novi Sad, Dec 2010
Biomechanics of Musculoskeletal System
Lecture 1: Human body: Basic anatomy and physiology
Lecture 2: Human movement recording
Lecture 3: Muscle modeling and simulations
Lecture 4: Musculoskeletal modeling and simulations
Lecture 5: Modeling for functional electrical stimulation
1. Skeleton (bones, joints)
2. Tendons
3. Ligaments
4. Muscles (structure, properties)
5. Peripheral nerves and receptors
6. Central nervous system
Bones
• Mechanical functions
– Support
– Transfer forces (lever)
– Protection of internal organs
• Physiological functions
– Forming blood cells (hematopoiesis)
– To store calcium (mineral homeostasis)
NAME OF BODY “REGION" No of
Bones
VERTEBRAL COLUMN, SACRUM,
AND COCCYX
26
CRANIUM 8
FACE 14
AUDITORY OSCICLES 6
HYOID BONE, STERNUM AND RIBS 26
UPPER EXTREMITIES 64
LOWER EXTREMITIES 62
TOTAL 206
Bones
Bone Composition
• Connective tissue
• Biphasic (composite) material
(~fiberglass)
• Composition:
– Cells (osteocyte)
– Extracellular matrix of fibers (collagen)
– Ground substance (proteoglycans)
– Water (25 %)
– Mineral salts
Microscopic Structure
Macroscopic Structure
Frontal longitudinal section through the head neck, great trochanter, and
proximal shaft of the adult femur. Cancellous bone, with the trabeculae
oriented in a lattice, lies within the shell of cortical bone. (From 13th
American Ed. Of Anatomy of the Human Body, Philadelphia, 1985.)
Material testing
F/A
(L – Lo)/Lo
Bone characteristics
ANISOTHROPY
Loading modes
Bone Fractures
Bone Remodeling
JOINTS
JOINTS
Joints
Cartilage
• Transferring forces between bones
• Distributing forces (loads) in the joints
• Relative movement with minimal friction
• Highly specialized tissue
– Typical thickness (1 – 5 mm)
– Isolated tissue (without blood vessels, lymph
channels, nerves)
– Lowest cellular density
Cartilage Composition
• Biphasic (composite) material (~ stiff
sponge): fibrous organic matrix and tissue
fluid (60%, mostly water)
• Extracellular matrix of collagen fibrils
enmeshed in concentrated solution of
proteoglycans
• Cell (chondrocytes)
Microscopic Structure
Collagen
Microscopic Structure
Proteoglycan Aggregates
Macroscopic Structure
Viscoelastic Properties
Self-Lubrication
BOOSTED LUBRICATION
MIXED LUBRICATION
Wear of the Cartilage
Muscle, Tendon, Bone
Tendons
• Attach muscles to the bones and transmit
tensile loads from muscles to bone,
thereby producing joint motion.
• The tendon enables the muscle to act at a
mechanically optimal point that can be
very distant from the actual muscle body
Tendon composition
• Parallel-fibered collagenous tissue
• Cells (fibroblasts)
• Water (70%)
• Solid (30%):
– Collagen (>75%)
– Proteoglycans (much less then in cartilage)
Structure
Muscle – Tendon – Bone
OSTEO-TENDON JUNCTION
MYO-TENDON JUNCTION
Tensile Properties
Ligaments
• To attach articulating bones to one
another across a joint
• To guide joint movement
• To maintain joint congruency
Ligament Composition
• Very similar to tendons
Ligament – Bone Junction
Ligament Function
Ligament Properties
MUSCLES
Skeletal Muscle
Structure
Contraction
Contraction
Muscle fiber properties Length – Active Tension
Muscle fiber properties Length – Total Tension
Muscle fiber properties Velocity – Tension
Muscle fiber properties Velocity – Length – Tension
Muscle Activation – Twitch
Muscle Activation – Tetanus
Motor units
SIZE
The smallest motor units are in muscles that
must produce very fine gradations of force (e.g.,
lumbricals - 100 fib/unit, eye muscles - 5 fib/unit).
DISTRIBUTION WITHIN MUSCLE
The fibers which make up a motor unit are not
adjacent to one another, but they inhabit the
same general region of the muscle.
MOTOR UNITS ARE ORGANIZED
ACCORDING TO:
Motor unit types
MOTORNEURON /
MUSCLE FIBERS
Small diameter
motorneurons innervate
slow oxidative fibers.
Intermediate sized
motorneurons innervate
fast oxidative/glycolitic
fibers
Large diameter
motorneurons innervate
fast glycolitic fibers.
SIZE PRINCIPLE
Small diameter motorneurons
are more easily excited
compared with the large
diameter motorneurons.
Therefore:
1. Slow oxidative motor units
are recruited by relatively low
level of excitatory synaptic
input.
2. Fast glycolitic motor units
are recruited by high levels of
excitatory synaptic input.
SIZE PRINCIPLE
RECRUITMENT
•Flexion/extension
•Abduction/adduction
•Internal/External Rotation
(Medial/Lateral)
____________________
•Monoarticular muscles
(over 1 joint)
•Biarticular muscles
(over 2 joints)
•Multiarticular muscles
(over more than 2 joints)
SKELETAL MUSCLES
plexus
tendon
SKELETAL MUSCLES
Agonist – muscle primarily responsible for
the movement
Antagonist - muscle which opposes the
agonistic action
Synergist – muscle that assists the
agonistic action
Fixator – synerigistic muscle that assists
stabilization of the joint
SKELETAL MUSCLES
A
G
B
C D
E
H
F I
J
K
Muscles controlling the hip joint: medial rotation (left panel) and lateral rotation (right panel). A) Gluteus Medius m. and Gluteus Maximus m; B) The Tensor Fascia Latae m; C) Adductor Magnus; D) Gluteus Minimus m. and m; E) Illipsoas m; F) Gluteus Maximus m; H) Gracilis m; G) Pectineus m; I) Piriformis m; J) Quadratus Femoris m; K) Obturator Internus m.
SKELETAL MUSCLES
Muscle, Tendon, Bone
PERIPHERAL
NERVES
MAIN BRANCHES OF RADIAL NERVE
BRANCHES OF MUSCULO-CUTANEOUS, MEDIAN & ULNAR N.
SUPERFICIAL BRANCH OF
ULNAR N.
DEEP BRANCH OF ULNAR N.
ULNAR N.
MEDIAN N.
CUTANEOUS NERVES
BRACHIAL N. PLEXUS
AXILARY N.
RADIAL N.
DORSAL DIGITAL N.
DEEP BRANCH OF
RADIAL N.
SUPERFICIAL BRANCH OF RADIAL N.
PERIPHERAL
NERVES
Main branches
of radial nerve
(left), and
median and
ulnar nerves
(right).
COMMON
PERONEAL N.
PUDENTAL N.
FEMORAL N.
SCIATIC N.
LUMBAR
PLEXUS
SACRAL
PLEXUS
TIBIAL N. DEEP PERONEAL N.
SUPERFICIAL
PERNOEAL N.
LATERAL SURAL
CUTANEOUS N.
SAPHENOUS N.
LATERAL FEMORAL
CUTANEOUS N.
MEDIAL AND LAT.
PLANTAR N.
PERIPHERAL
NERVES
MUSCLE
TENDON
TENDON
GAMMA MOTOR
NEURON
GOLGI TENDON
ORGAN
AFFERENT
GOLGI TENDON
ORGAN
ALFA MOTOR
NEURON
EXTRAFUSAL
MUSCLE
FIBER
INTRAFUSAL MOTOR
NEURON (MUSCLE
SPINDLE)
PRIMARY
SPINDLE
AFFERENT
SECONDARY
SPINDLE
AFFERENT
FREE
NERVE
ENDING
The muscle spindles (intrafusal fibers) are in
parallel with the extrafusal fibers; the Golgi
tendon organs are in series. The intrafusal
fibers attach actually to the extrafusal fibers, not
to the tendons
PERIPHERAL NERVES
PERIPHERAL NERVES
Control loops
Lateral view of the spinal cord and its location in the spinal canal.
CERVICAL
CORD
THORACIC
CORD
LUMBAR
CORD
SACRAL
CORD
THORACIC
NERVES
CERVICAL
NERVES
LUMBAR
NERVES
SACRAL
NERVES
LUMBOSACRAL
ENLARGEMENT
SPINAL CORD
DORSAL COLUMN
INTERMEDIATE
ZONE
DORSAL MEDIUM
SEPTUM DORSAL INTERMEDIATE
SEPTUM
ZONE OF LISSAEUR
VENTRAL COLUMN
VENTRAL MEDIAN
FISSURE
WHITE MATTER
GRAY MATTER
DORSAL
ROOT GANGLION
DORSAL HORN
VENTRAL HORN
The white matter of the spinal cord is divided into columns, and the gray matter is divided into horns. The Roman numbers show laminae divided
in three major divisions.
SPINAL CORD
DORSOLATERAL
CELL GROUP
INTERMEDIATE ZONE
MOTOR NEURON POOL
TO AXIAL MUSCLES
VENTROMEDIAL
CELL GROUP MOTOR NEURAL POOL TO
LIMB MUSCLES
VENTRAL ROOT
DORSAL HORN
VENTRAL HORN
DORSAL ROOT
GANGLION
Input-output organization of spinal segments and interconnections between segments.
DORSAL ROOT
Central Pattern Generator • Basic rhythm
• Variable response
• Evidence from non-primates
• Local or distributed
• Single-cell or network
SPINAL CORD
THE SPINAL CORD / INTEGRATION &
CINNECDTIVITY
The spinal cord has a lot of clockwork that can be mixed
and matched to perform tasks (This was mostly
postulated by Sherington – reflex)
The brain learns to perform tasks by iteratively optimizing
its use of the spinal clockwork (Optimal control is
inevitable)
Some strategies take more practice and knowledge of
results to discover (coaches can help avoiding local
minima)
No brain ever foregoes a potentially useful strategy to
validate a pet theory (motor physiology tends to be
mechanically inevitable of experimentally falsifiable)
The major division of the central nervous system. The top portion is a cerebral hemisphere. The parts are: cerebral hemispheres, diencephalon, midbrain, pons, medulla and spinal cord.
ACTIVITY OF CORTICAL REGIONS - fMRI
The lateral view of the cerebral cortex of the left hemisphere.
ACTIVITY OF CORTICAL REGIONS - fMRI
HOMUNCULUS (Rasmunsen, 1950)