7. MOB TCD
Tibia
• The shaft of the tibia is
mainly compact bone
• A central medullary cavity
containing mainly fat
• The ends are compact bone
• With an inner core of
cancellous bone
• The periosteum is the
vascular fibrous connective
tissue investing bone
8. MOB TCD
Trabecular or Cancellous Bone
• Found inside cortical shell
e.g. Vertebrae
• Consists of horizontal and
vertical plates
• Spaces are filled with bone
marrow
• Large surface area
• Porosity is between 30-90%
9. MOB TCD
Trabecular or Cancellous Bone
• Greater capacity to store
energy
• In vitro fractures at strains
>75%
• Metabolically more active
• More sensitive to changes in
endocrine hormones
Carter & Hayes,1976; Einhorn, 1996
10. MOB TCD
Cancellous Bone
• Compressive strength is
proportional to the square of
the apparent density
• Small changes in density
• Large change in strength
Dalen et al., 1976
11. MOB TCD
Bone
• Organic matrix
• Type I collagen forms 90%
of skeletal weight
• Mineral hydroxyapatite ratio
• Calcium 10
• Phosphate 6
• Carbonate 1
12. MOB TCD
Bone Remodelling
• Bone is a living tissue
• Osteoclastic activity i.e.
bone resorption takes
only few days
• Osteoblastic or bone
formation takes several
months
14. MOB TCD
Phases of Bone Remodelling
Normal bone
turnover
Osteoporotic bone
turnover
osteocytes
Quiescence
bone
Activation
osteoclast
Resorption
Formation
osteoblast
osteoid
new bone
Quiescence
D1202
15. A Healthy Skeleton depends
on a Balanced RANK Ligand:
OPG Ratio
RANK
Ligand
NK
RA nd
iga
L
OPG
Increases
Bone Loss
OPG
RAN
Liga K
nd
OPG
Prevents
Bone Loss
1 Hofbauer LC et al. JAMA 2004;292: 490–495; 2 Lacey DL et al. Cell 1998;93:165–176;
3 Boyle WJ et al. Nature 2003;423:337–342
MOB TCD
16. A Healthy Skeleton requires a Balance
of Bone Resorption and Formation
Activation
Resorption: 10 days
When bone turnover is
increased, bone loss
dominates
Reversal
Resting
Formation: 3 months
Adapted from Baron, R. General Principles of Bone Biology. In: Primer on the Metabolic Bone Diseases and Disorders of Mineral
Metabolism. Favus MJ (Ed.) 5th Edition. American Society for Bone and Mineral Research, Washington DC, 2003: 1–8
MOB TCD
21. MOB TCD
Wolff’s Law
• Changes in bone function
lead to changes in bone
• Bone is laid down where
needed
• Bone is resorbed where it
is not needed
Wolff, 1892
22. MOB TCD
Mechanical Strain
• Osteogenesis is induced
by dynamic not static
strains
• The optimal type of
osteogenic activity should
provide relatively high
levels of strain
Rubin & Lanyon, 1984
23. MOB TCD
Bone
• Tensile forces result in
osteoclastic activity
• On the convex side of an
angulated bone
• Compressive force
results in osteoblastic
activity on concave side
24. MOB TCD
Bone
Bones require
• Normal hormones
• Adequate calories
• Particularly protein
• Calcium
• Vitamin D
• Regular weight bearing
exercise
25. MOB TCD
Age Related Changes in Bone Mass1
Attainment of Peak
Bone Mass
Consolidation
Age Related Bone Loss
Menopause
Men
Fracture
threshold
Women
0
10
20
30
Age (years)
40
50
60
1. Compston JE. Clinical Endocrinology 1990;33:653-682
D1202
26. MOB TCD
Peak Bone Mass
•
•
•
•
Genetic
Environmental factors
Mechanical strain
Hormones
27. MOB TCD
Peak Bone Mass
• Weight bearing activity
during adolescence and
early adulthood was a far
more important predictor of
peak bone mass than
calcium intake
Welten et al., 1994
28. MOB TCD
Low Peak Bone Mass
• Growing bone has a greater
capacity to add new bone
to skeleton than mature
bone
Forwood & Burr, 1993
29. MOB TCD
Osteogenesis
• Muscle action is main
stimulus for bone
formation
• Mechanical force
• Weight bearing
Birge et al., 1968
32. MOB TCD
Flat Bones and Irregular Bones
Flat bones
• Usually consist of two layers
of compact bone
• Cancellous bone lies in
between
• Found in the skull and
sternum
Irregular bones
• Occur in the face and
vertebrae
33. MOB TCD
Sesamoid Bones
Sesamoid bones
• Develop in tendons where
they cross bone
• Or articular surfaces,
patella
• Sesamoids in relation to
thumb and hallux
34. MOB TCD
Long Bones
Long bones
• Have a cartilaginous
ossification
• Are found mainly in the limbs
and consist of:
• Shaft (the diaphysis), which is
ossified from the primary center
of ossification during
intrauterine life
• The cavity of the shaft, contains
red marrow in the fetus, yellow
fat in the adult
35. MOB TCD
Bone Growth
• Diaphysis: shaft ossified from
primary center of ossification
which appears 6-8th week of
intrauterine life
• Epiphysis: ossified from
secondary center
• Growth plate is cartilage
• Injury of epiphysis affects
growth
36. MOB TCD
Epiphysis
• Is ossified from a secondary
center of ossification
• These usually appear shortly
after birth
• Except for the lower end of the
femur, which appears 9
months intrauterine life, just
before birth
• Epiphysis unite with the
diaphysis (shaft) from puberty
to early twenties depending on
the bone involved
37. MOB TCD
Metaphysis
• The portion of the diaphysis
beside the epiphysis is called
the metaphysis
• This is the region where
osteomyelitis tends to occur in
young people
• The metaphyseal arteries are
end arteries until ossification is
completed i.e. the epiphyseal
plate is ossified
38. MOB TCD
Bones
• Long bones grow in length from
epiphyseal plates
• Increase in width is from
periosteum
• Damage to the epiphyseal
growth plate can lead to
premature closing and retards
normal growth
• Anabolic steroids will also cause
early closure
39. MOB TCD
Epiphyses
•
•
•
•
Traction epiphyses
The tibial tuberosity
Osgood-Schlatters
Medial epicondyle of the
humerus, in ‘little league
elbow’
• Compression epiphysis
• The distal end of the
humerus
40. MOB TCD
Musculoskeletal Problems
• Younger athletes
• Suffer many of the same
injuries and illnesses as adults
• Differences is the structure of
growing bone
Avulsed epiphysis
43. Growth Plate Fractures
Salter-Harris Classification
• Type 1 and type 2 heal well
• Type 3 and type 4 involve joint
surface as well as growth plate
• Type 5 compression of growth
plate
• Difficult to detect
• Growth ceases
MOB TCD
44. MOB TCD
Blood Supply of Bone
• Periosteal arteries enter bone
at several points to supply the
compact bone
• Nutrient arteries supply spongy
bone and bone marrow
45. MOB TCD
Blood Supply of Bone
• Periosteal arteries enter the
bone at several points to
supply the compact bone
• Nutrient arteries supply the
spongy bone and bone marrow
• Epiphyseal arteries supply the
epiphysis
• Metaphyseal arteries supply
the metaphysis
46. MOB TCD
Blood Supply of Bone
• Periosteal arteries occur particularly
at the sites of attachments of muscles
and tendons
• If a group of muscles inserted into a
bone is paralysed before puberty
• That bone will be shorter than the
equivalent bone on the other side
• Due to reduced blood supply from the
muscles involved
• The lack of stimulus to bone from lack
of muscle contractions
• After puberty only muscle bulk is
reduced
47. MOB TCD
Blood Supply of Bone
• Epiphyseal arteries supply the
epiphysis
• Metaphyseal arteries supply
the metaphysis
• These are end arteries until
epiphysis unites with diaphysis
48. MOB TCD
Avascular Necrosis
• Bones that have a large surface
area covered with articular
cartilage tend to have a poorer
blood supply
• Avascular necrosis occurs if
blood supply is cut off due to
fracture
• e.g. head of femur, due to
fracture of neck of femur
• Proximal portion of the
scaphoid
• Body of talus or dislocation e.g.
lunate
49. MOB TCD
Apophysis
•
•
•
•
Tendon attachment to growth plate
Traction injuries may occur
Medial epicondylitis
Limit numbers of pitches in
baseball
• Osgood-Schlatters lesion of tibial
tuberosity
• 12-16 year olds
51. MOB TCD
Bones in Children
•
•
•
•
More flexible
More elastic
Less brittle
Growth plate is weakest
link
• Periosteum thicker
52. MOB TCD
Bones in Children
• Articular cartilage thicker
• Junction between
• Metaphysis and epiphysis
vulnerable
• Shearing forces
• Tendon attachment to
apophysis weak
53. MOB TCD
Eating Disorders
May result in
• Delayed bone growth
• Delayed menarche
• Low peak bone mass
• Osteopenia or osteoporosis
• Increased musculo-skeletal
problems
54. MOB TCD
Articular Cartilage
• The thickness of the
cartilage depends on the
stress to which it is
normally subjected
• Varies over the joint
surface
• Patella has the thickest
articular cartilage
55. MOB TCD
Articular Cartilage
• Articular cartilage is avascular
• Nourished by synovial fluid,
from capillaries in the synovial
membrane
• When the articular surfaces are
in contact
Hollingshead, 1969
58. MOB TCD
Stress Fractures
•
•
•
•
•
•
•
•
•
Biomechanical causes
Training errors
Athletic triad
Amenorrhea
Eating disorders
Osteoporosisor osteopenia
X-ray many times negative
MRI is extremely sensitive
Stress fracture of the femoral neck
is potentially serious and need
often surgery
59. MOB TCD
Joint
• Junction between two
bones
• Function and movement
depends
• Size and shape of
articular surfaces
• Soft tissues surrounding
the joint
60. MOB TCD
Range of Joint Movement
•
•
•
•
•
•
Shape of articulating surfaces
Restraint due to ligaments and muscles crossing joint
Pain, weakness, spasm or contracture of muscles
Bulk of adjacent soft tissue
Impingement of bony surfaces
Scarring of skin due to injury or burns
61. MOB TCD
Muscles
• Muscle can only act on a joint,
if it crosses the joint
• Muscles that have a common
action on the joint tend to have
same nerve supply
• Usually nerve of compartment
gives an articular branch to
joint
• Exception, flexors of the
elbow, where median, ulnar
and radial all give branches
63. MOB TCD
Fibrous Joints
• Fibrous union
• Slight movement
• Gomphosis i.e. tooth and
its socket
• Sutures
• Syndesmosis
64. MOB TCD
Fibrous (Suture)
• Consists of dense fibrous
connective tissue between
the bones
• Periosteum covering the
opposing surfaces of the
bones
• Synostosis
• Fusion of the bones
across the sutural joints
continues throughout life
65. MOB TCD
Fibrous Syndesmosis
• Interosseous membranes:
radius and ulna, similar in lower
limb and inferior tibio-fibular joint
66. MOB TCD
Primary Cartilaginous
• Cartilage continuous with
bone
• No movement
• Rib and costal cartilage:
costo-chondral joints
• First costal cartilage and
sternum
• Diaphysis and epiphysis
67. MOB TCD
Primary Cartilaginous
• Epiphysis and diaphysis
• Rib and costal cartilage
• 1st costal cartilage and
manubrium sternum
• No movement
76. MOB TCD
Plane Joint
• Surface is flat
• Only allows gliding movement
• Non-axial e.g. facet joints of
vertebrae
• Talo-calcaneal joint
Talo-calcaneal
77. MOB TCD
Hinge Joint
• Movement in one plane
(uniaxial) e.g. elbow
• Interphalangeal joints in
hand and foot
• Strong ligaments on
sides, weaker anterior
and posterior
78. MOB TCD
Pivot Joint
• Allows rotation around a
single axis
• Uni axial
• Atlanto axial
• Superior and inferior
radioulnar joints
79. MOB TCD
Saddle Joint
• Saddle-shaped concavoconvex surfaces
• Movement in two planes
(biaxial) e.g. carpometacarpal of the thumb
(trapezium and base of first
metacarpal)
80. MOB TCD
CondylarJoint
• Two axes at right angles
to each other
• Movement in two planes
(biaxial)
• Meta-carpophalangeal
• Sternoclavicular
• Atlanto-occipital joints
81. MOB TCD
Ball and Socket Joint
• Allows movement in three
axes
• Multiaxial
• Hip
• Shoulder
• Talocalcaneo-navicular
joints
82. MOB TCD
Synovial Joints
• Discs of fibro cartilage or menisci in
some joints
• Blood supply at periphery
• Increase the depth and mobility of the
joint
• Synovial folds in joints
• Synovial membrane
• Nerve endings also in fat
• Infrapatellar fat pad
• Facet joints of lumbar vertebrae
• Elbow
83. MOB TCD
Capsule
• Consists of collagen (type I)
• Thickened to form ligaments
• Expanded quadriceps
tendon
• Sesamoid bone in
quadriceps tendon
• Synovial membrane lines
the inner surface of the
capsule and non articular
structures inside capsule
85. MOB TCD
Haversian Pads of Fat
• Fat pads are semi-liquid at
body temperature
• They fill the changing
spaces that occur during
movement
• These pads help to reduce
friction between moving
tissues
86. MOB TCD
Sensory Supply
• Sensory nerves in fibrous
capsule and ligaments and
synovial membrane
• Information about pain
• The position of the joint
(proprioception)
• Poor proprioception
predisposes to injury
Isakov & Mizrahi, 1997
87. MOB TCD
Synovial Joint
• The epiphyses of many long
bones are intracapsular
• Injury to a joint, before the
cessation of growth, may
damage the epiphyseal
cartilage
• The articular surfaces are
covered by hyaline or
articular cartilage
88. MOB TCD
Hyaline Cartilage
• Hyaline cartilage is avascular
• Nutrition is by diffusion from
the synovial fluid
• Must be in contact with the
opposing articular surface
89. MOB TCD
Open and Closed Kinetic Chain
• Open kinetic chain
• The distal segment is free in
space
• Raising the hand in the air
• Closed kinetic chain
• The distal segment is fixed
90. MOB TCD
The Degrees of Freedom
• Joints can also be classified by
degrees of freedom
• Reflects the axis of movement
• If a joint has only one axis
• It has only one degree of freedom
91. MOB TCD
The Degrees of Freedom
• Nonaxial: no axis of rotation
• Uniaxial: move in one axis
• Have one degree of freedom
• Acromioclavicular 1
• Elbow 1, radioulnar 1
• Proximal and distal
interphalangeal 1
• Biaxial: move in two axes
• Have two degrees of
freedom
• Metacarpophalangeal 2 +
• Wrist 2 +
• Multiaxial: move in
three axes
• Have three degrees of
freedom
• Maximum any joint can
possess
•
•
•
•
Shoulder 3
Sternoclavicular 3
Hip 3
Talocalcaneonavicular 3
93. MOB TCD
Least-Packed
• Joint more likely to be injured in
least-packed position
• Capsule slackest
• Joint held in this
• Position when injured
• Fluid in knee held in 20° flexion
94. MOB TCD
Range of Joint Movement
•
•
•
•
•
•
Shape of articulating surfaces
Restraint due to ligaments and muscles crossing joint
Pain, weakness, spasm or contracture of muscles
Bulk of adjacent soft tissue
Impingement of bony surfaces
Scarring of skin due to injury or burns
Alterations of the RANK Ligand/OPG ratio are critical in the pathogenesis of bone diseases that result in increased bone resorption:
Unopposed RANK Ligand (i.e. an elevated RANK Ligand/OPG ratio) within the skeleton promotes bone loss
Restoring a balanced RANK Ligand/OPG ratio or inhibiting RANK Ligand decreases osteoclast activation and bone resorption.1–3
In many diseases involving increased bone resorption, RANK Ligand expression is upregulated by osteoclastogenic factors (growth factors, hormones, cytokines), while OPG expression is simultaneously downregulated.3
Bone remodelling is the process by which old bone is replaced by new bone.
Bone remodelling consists of four phases: resting, resorption, reversal and formation.1
During the resorption phase, osteoclasts remove both mineral and organic components of bone matrix by generating an acidic microenvironment between the cell and bone.
Once the osteoclasts have resorbed most of the mineral and organic matrix, they undergo apoptosis during the reversal phase and osteoblasts are recruited to the bone surface.
In the formation phase, osteoblasts deposit new, healthy osteoid (unmineralised collagen matrix), which is subsequently mineralised, resulting in good-quality bone.
This figure by Compston (1990), illustrates the changes in bone mass throughout life and shows the rapid bone loss that occurs at the menopause. Bone mass in both men and women increases until a peak is attained at around age 30. In both sexes, a slow rate of bone loss starts at around age 40. However, in women, the accelerated postmenopausal phase of bone loss is superimposed on top of this slow loss phase. Rates of bone loss in postmenopausal women can be as great as 5-6% per year. In women, oestrogen deficiency is the major determinant of bone loss after the menopause due to the removal of the ‘brakes’ from Osteoclastic activity.
The accelerated bone loss is important to remember when looking at preventative therapies for osteoporosis. Unlike treatment for the established disease when relatively large increases in bone mass are observed in response to therapy, a preventative strategy may be said to have been effective if the bone mass is maintained.
National Osteoporosis Society, Menopause and osteoporosis therapy - GP manual 1993.
National Osteoporosis Society, Priorities for Prevention.
Hosking D J et al, J. Bone Miner. Res., 1996: 11 (1); S133, 153.