1
Pathology
Pathology
of
of
the
the
locomotor
locomotor
system
system
Skeletal system
Pathology
Pathology
of
of
the
the
bones
bones
• Transformation of the vertebrae and
bones
• Osteopathies
– abnormalities of the osteogenesis
• Disturbances of the mineralization
• Regressive changes of the bones
Transformation of the vertebrae
Transformation of the vertebrae
and bones
and bones
• Spondylolisthesis

• Tibiarotation
• Twisted leg syndrome
• Spread leg syndrome
Transformation of the vertebrae
Transformation of the vertebrae
• Spondylolisthesis
– devolution of the vertebra
– and tilting at the same time
Anatomy
• functional anatomy
– The spinal column is parallel with the ground in a
newly hatched chick on the first day
– the physiological lordosis develops on the first
week
– and so does the position, pose typical for the
species
Photo: Dr. Dobos-Kovács, Mihály
Spondylolisthesis
Spondylolisthesis
(
(
devolution
devolution
of
of
the
the
vertebra
vertebra
)

)
• The chicks develop fastest in the first 3
weeks of age
– The pectoral muscles grow considerably
– later it is even more explicit
• the large pectoral musculature….
– pulls the 6. thoracic vertebra and moves it
from its normal position….
– The spinal column suffers refraction at the
level of the 6th vertebra….
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Photo: Dr. Dobos-Kovács, Mihály
Spondylolisthesis
Spondylolisthesis
(
(
devolution
devolution
of
of
the
the
vertebra
vertebra
)
)
During walking
• from the direction of the hind legs
• power acts forward and downward
– On the previously tilted vertebra

• the back of the vertebra moves
– up and forward
• the front of the vertebra moves
– down and backwards
• the 6. thoracic vertebra moves downwards
– slips (devolution)
• and tilts from its original pose
Photo: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály
Spondylolisthesis
Spondylolisthesis
(
(
devolution
devolution
of
of
the
the
vertebra
vertebra
)
)
• Typical lesion in large meat type chicken hybrids with
huge pectoral musculature
– affects smaller or larger part of the flock
– husbandry problems (keeping and nutrition factors) are also
involved
• The 6th vertebra which moved from its original
position…

– compresses the ventral part of the spinal cord
– Waller-degeneration occurs in the motoric nerve tracts
– weakness and paralysis develops in the hind legs
• consequences:
• the affected animals first limp, later are not able to
move
– no drinking (uricosis)
– exsiccosis
– starving to death
Photo: Dr. Dobos-Kovács, Mihály
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Transformations
Transformations
of
of
the
the
spinal
spinal
column
column
• Lordosis
– the spinal column bends up
• Kyphosis
– the spinal column bends down
• Scoliosis
– the spinal column bends in S shape
Transformations
Transformations
of

of
the
the
spinal
spinal
column
column
• In case of spondylolisthesis
– and during spondylosis too
• pain occurs
– due to the compression of the spinal cord
• and due to the compression of the nerve tracts too
• The bird tries to reach the less painful pose
(position of the spinal column)
– in most cases immediately gets paralyzed
• The abnormal pose of the spinal column
– ossifies soon and gets fastened
– according to the abnormal, but less painful position!
Scoliosis
Photo: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály
Transformation
Transformation
of
of
the
the
bones
bones
• Tibiarotation

– the tibiotarsal bone gets twisted
around its longitudinal axis
– usually turns laterally
• 45-90-180°
– the distal part of the join turns with
– and so does the lower part of the
leg
– The joint turns too
The tendon follows the joint, it
remains in the pit!!!
• Twisted leg syndrome
• Spread leg syndrome
Photo: Dr. Dobos-Kovács, Mihály
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Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
Tibiarotation
Tibiarotation
• The cause is not known
– genetic predisposition?
– malnutrition?
– husbandry problems?
• Increasingly often seen in young poult
– according to field experiences
– malsecretion maldigestion and malabsorption
increases the possibility of the lesion
– in young age
• Rickets is the predisposing factor in guinea
fowl chicks for the tibiarotation
Twisted leg
Twisted leg

syndrome
syndrome
• The disease starts with the lateral or medial rotation
of the distal part of the tibiotarsal joint
– the leg follows the turning part of the joint with the tarsal
bone
– the distal part of the leg turns out or in together with the
tibiotarsal joint
– It looks like the joint was twisted
• Diagnosed in broiler chicken and turkey
Twisted leg
Twisted leg
syndrome
syndrome
• The pathogenesis is
not cleared yet
• The appearance of
the syndrome
increases with the
appearance of new
genetic lines in
broiler chicken and
turkey industry
• It highlights the
predisposition of the
modern hybrids
towards this
condition
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Spread

Spread
leg
leg
syndrome
syndrome
• The legs are spread to the side or to the
back
– the legs turn from the coxofemoral joint
– it can occur uni- or bilateral
• Causes – not clear
– high humidity during hatching?
– according to observations it develops in
newly hatched birds on slippery floor
• In some cases the lesion develops only
in 2-3 weeks old birds
Photo: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály
Osteopathies
Osteopathies
• Several different substances are needed for the
normal development of the bones
– In case some materials are not available in proper amount,
typical lesions develop in the bones
• Forms:
– Osteopathy due to lack of vitamin D3 (rickets)
– Osteopathy due to lack of calcium
• Rickets due to Ca deficiency
– Osteopathy due to lack of phosphorus
• rickets due to P deficiency
– Osteopathy due to lack of proteins

– Osteopathy due to lack of vitamins
– Osteopathy due to lack of minerals
– Osteopathy due to lack of viral infection
– Other osteopathies
Osteopathy due to lack of
Osteopathy due to lack of
vitamin D3 (rickets)
vitamin D3 (rickets)
• this is the original disease
– lack of sunshine – not enough vitamin D was produced in the skin
– vitamin D supply was not enough for the animal
• the original meaning of the disease:
– rickets is the incomplete development and ossification of the
growing bones
• incomplete development and ossification of the growing bones
due to lack of vitamin D
– there is enough Ca and P in the feed
– no vitamin D3, no transport proteins are produced which are
eccential for the Ca absorption from the gut
• In broader meaning:
– Besides the rachitis caused by lack of vitamin D
– We call rickets the osteopathies due to lack of Ca- and/or P!!!
• In case of rachitis lesions develop in all growing bones
• Most important to check
– The long bones, the ribs and the sternum
Rickets
Rickets
• In the long bones of birds
– enchondral ossification is
examined in the proximal

epiphysis
• The parts of the proximal
epiphysis:
– Epiphyseal cartilage
– Proliferation zone
• production of cartilage
• necrotizes and calcification
occurs
– Growth zone
• With the active bone marrow
• resorption of the calcified
cartilage
• new bone replaces the
cartilage
Photo: Dr. Dobos-Kovács, Mihály
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Rickets
Rickets
due
due
to
to
lack
lack
of vitamin D
of vitamin D
or
or
Ca
Ca

• In the deep layers of the epiphyseal cartilage new
chondrocytes and cartilage is formed
– later the chondrocytes necrotize and the cartilage calcifies
– active bone marrow intrudes into that layer
– and it resorps the necrotized and calcified cartilage
• Production of new bone tissue
– At the beginning osteoid is formed
– This calcifies
– 1:9 - Ca-carbonate and Ca-phosphate
– + small amount of Mg-phosphate and calcium-fluoride
• In case of rickets due to lack of vitamin D3 in the long
bones
– epiphyseal cartilage is produced
– The other processes are slower or do not floolw the cartilage
prodution
• So the epiphyseal cartilage becomes thicker
– The cartilage extends due to the bodyweight
– The end becomes butt, and painful, the bone bends
Photos: Dr. Dobos-Kovács Mihály
Rickets
Rickets
due
due
to
to
lack
lack
of
of
Ca

Ca
Photos: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
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Photo: Dr. Dobos-Kovács, Mihály Felvétel: Dr. Dobos-Kovács Mihály
The
The
bone
bone
can
can
be
be
broken
broken
without
without
sound
sound
• There is constant ossification and the depots
are used up
• The compacta of the bone becomes thinner
and the bone is spongy
– juvenile osteoporosis
Rickets
Rickets
due
due
to
to

lack
lack
of P
of P
Photo: Dr. Dobos-Kovács, Mihály
Osteopathies
Osteopathies
• Osteopathy due to lack of proteins
– Lack of amino acids
• Lysine
– hypoplastic type of bones are produced
• Osteopathy due to lack of vitamins
– Lack of vitamin C
– Lack of nicotinic acid
• vitamin B5, niacin
• rickets-like lesions
– Lack of vitamin A
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Osteopathy due to lack of vitamins
Osteopathy due to lack of vitamin C
• the malfunction of the mesenchymal cells
• because of their fatty infiltration
– cartilage and osteoid production
– deceased production of the basic substance
• no problem with the calcification
Osteopathy due to lack of vitamin niacin
(rickets-like lesion)
• the lesions are similar like in case of osteopathy due
to lack of P
• in geese

Osteopathy due to lack of vitamin A
• the enchondral ossification is decreased
– In some case the skull and the vertebrae are also affected
Osteopathy due to lack of
Osteopathy due to lack of
minerals
minerals
• Osteopathy due to lack of manganese (Mn)
– perosis
• the Achilles-tendon slips from the sulcus to the side
• the distal end of the leg turns lateral
– appears in young chicks and poult
– rarely in pheasant and other birds
• Osteopathy due to lack of zinc (Zn)
– Zn is essential to the development of the
skeleton
• when Zn is missing, the lesions appear in the distal
epiphysis of the tibia
Perosis
Perosis
• Osteopathy due to lack of Manganese (Mn)
– this lesion is mainly seen in case inadequate
amount of manganese is available
– but lack of other substances can also induced
similar lesions
• pyridoxine (vitamin B6)
• biotin (vitamin B7 or H)
• nicotinic acid (vitamin B5 or niacin)
• folic acid /folacin/- (vitamin Bc or M)
• choline (vitamin B komplex)

– alone or in combination
• the manganese influences the enchondral
ossification
– the extracellular substance (the matrix) of the
cartilage is produced in decreased amount
Perosis
Perosis
• In a classic case the lateral part of sulcus
tendinis at the distal end of the tibiotarsal
bone grows slower
– the lateral part becomes shorter
– the Achilles-tendon can easily slip to the
lateral side
– the distal end of the leg turns out
• because of these processes
– the distal end of the tibiotarsal bone is more
smooth then normally
– the sulcus and the bone condyles are flat
Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
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Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály
Osteopathy
Osteopathy
due
due
to
to
lack
lack

of
of
Zn
Zn
• The lateral epyphyseal cartilage grows and ossifies faster then
the medial
– The distal epyphisis of the tibia bends inward
– the Achilles-tendon slip to the middle from the sulcus tendinis
Photo: Dr. Dobos-Kovács, Mihály
Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
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Photo: Dr. Dobos-Kovács, Mihály Photo: Dr. Dobos-Kovács, Mihály
Osteopthies
Osteopthies
caused
caused
by
by
viruses
viruses
• Short beak and dwarfism syndrome of mule duck
– SBDS
• Mulard = pekin duck ♀ x Muscovy duck ♂ hybrid,
„mule duck”
• Pathogenesis
– the mulard ducklings develop slowly and heterogenously
• from young age already
– Lack of development shows on the bones of the beak and
tarsus
• the beak becomes shorter then normally, the head is

deformed
• looks like the beak and head of goose
– the tongue grows normally, so it hangs out from the beak
– and dries out on the air
– the animals look smaller, underdeveloped
• because of the shortness of the tarsus
Photo: Dr. Palya, Vilmos
Photo: Dr. Palya, Vilmos
Other
Other
osteopathies
osteopathies
• Lack of salt
– the waterfowl are very sensitive
• especially duck
– In NaCl (table salt, especially natrium)
deficency rickets-like lesions develop
• similar to osteopathies due to lack of Ca and
vitamin D
• the proliferation zone of the epiphyseal
cartilage becomes thicker
• the osteoid tissue is not properly calcified,
and the matrix is less
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Disturbances
Disturbances
of
of
mineralization
mineralization

• Osteoporosis
• Osteomalatia
• Osteodystrophia fibrosa
Osteoporosis
Osteoporosis
• develops in case the balance between the bone
remodelling (resorption and formation) splits and
the resorption exceeds formation
– faulty mineralization of the bones
– which cause the bones to become porous within, with a
lot of embedded hollow-like spaces
– the cortex of the bone becomes thinner
– osteoporosis often develops in the epiphysis of the bone
– more brittle bones, and get fractured easily
• appears in all ages
• in young age it is called juvenile osteoporosis
– in broilers the malsecretion, maldigestion, malabsorption
syndrome can lead to osteoporosis
– in poult the PEMS or other independent viral enteritides
– the nutrirent supply is not adequate in these cases
• proteins, vitamins, minerals
Osteoporosis
Osteoporosis
• In pullets or adult the quality and the
quantity iof the feed influences the
appearance of osteoporosis
– the most often seen causes are lack of protein,
vitamins A, B2 and C, lack of Cu, Mn, Zn
– In this case the osteoporosis effect
multitudinous birds and bones! – systemic,

generalized lesion
• Solitary osteoporosis
– partial (affects few bones only) osteoporosis
– In case of disuse (paralysis, mechanical trauma)
– atrophia ex inactivitate
– osteoporosis occurs on areas where the
remodelling is very intense
• f.e. epiphysis
Osteoporosis
Osteoporosis
In cage layers
• osteoporosis occurs usually at the end of the
egg laying season
– It is called „caged layer fatigue”
– involving bone brittleness, paralysis, and death
– the bone loss results in increased bone fragility
and susceptibility to fracture
• affected bones are the pelvis, vertebrae, sternum, ribs,
humerus and femur
• the fractures cause compression of the
nerves, resulting in innervation problems and
decreased loadability
– „caged layer paralysis”
Osteomalacia
Osteomalacia
• the softening of the bones caused by defective bone
mineralization secondary to inadequate amounts of available
phosphorus and calcium
– it develops in adult birds – in bones finished growing
• in case inadequate amounts of Ca and P are available

• The body resorps the wanted minerals from the already
formed bone to cover the needs
– f.e. Ca required for egg laying
• generalized bone condition in which there is inadequate
mineralization of the bone
• the compact and the spongy (trabecular) bones loose their
strength
• the bones of the adult bird are
– easily cut, sawed
– the spongy bone is more visible
– the bone bend
– With histopathology:
• broad, not calcified, elastic, soft osteoid can be observed
Osteodystrophia
Osteodystrophia
fibrosa
fibrosa
• In case the statics of the bones is disturbed
• the trabecules move from the normal position
• The organism tries to get back the balance
• It can occur in both growing or finished bones
– in different forms of rickets
– in case of osteomalacia, osteoporosis
• Appears in different bones
– the bones might enlarge
• The regular lamellar structure of the bone disappears, the
lamellae of the bone are thin and - in certain areas - dissolved
due to the vigorous osteolysis
• Pathogenesis
– Increased activity of the osteoclasts (resorption)

– The compact and the trabecular bone become porous
• thin, irregularly positioned spicules
– Angiofibroblast replaces the bone tissue
– proliferating osteoblasts are present in great number, and
osteoid tissue produced by them can be seen without
calcification
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Regressive
Regressive
changes
changes
in
in
the
the
bones
bones
• Atrophy (atrophia ossium)
• Usuration of the bone
– lacunar resorption following constant pressure (soft tumor)
• Osteochondrosis
• Epiphysiolysis
• Dyschondroplasia
• Remnant of the embryonic cartilage
• Discoloration, pigmentation of the bones
– Melanosis
– Discoloration caused by accumulation of tetracycline
• Necrosis of the bone
– femoral head necrosis
Atrophy

Atrophy
• occurs in long bones following disuse of the leg
– the compact becomes thinner
– the trabecules become thinner and decrease in number too
– atrophy of the exposed muscles usually also seen
• It can be observed if chronic inflammation develops
in the hind legs (joints or tendon sheets)
– orthoreoviral arthritis/tenosynovitis
– lesions of the bones
– tibiarotation, lack of Zn or Mn
• It is painful
• the animal does not stand on this side
– atrophia ex inactivitate
Osteochondrosis
Osteochondrosis
• Regressive change in the bones
– Disturbance of the normal development of the bone
– different forms of the disease
– appears in fast growing broiler chickens
• Described in several bones
– In the cervical and thoracic vertebraa
– In the femur and in the antitrochanter
• The lesions are microscopic and occur between the
epiphyseal cartilage and the proliferation zone
– serous infiltration, degeneration and blockage of the blood
vessels (thrombosis) can be seen in the proliferation zone
• According the data in some broiler flock 50% of the
chickens is affected to some extent
– most of them show clinical signs too
• osteochondrosis often occur togetehr with some

other skeletal lesions
Epiphysiolysis
Epiphysiolysis
• Mainly in the proximal epiphysis of the femur
– loose structure with decreased strength
– in fast growing broiler chickens
• The two parts (epiphysis and diaphysis) of the bone
separate from each other
– at the proximal epiphysis
– due to a minor trauma (slightly in excess of normal physical
stimulus)
• normal movements (like jumping), handling
– between the two parts degenerative changes and necrosis can
be observed
• if the separation occurs in life, bleeding can be seen
– It can appear in carcasses following preparation for the
dissection
Epiphysiolysis
Epiphysiolysis
Photos:
Dr. Dobos-Kovács, Mihály
Dyschondroplasia
Dyschondroplasia
• In the growing long bones
– most often seen in the proximal epiphysis of the tibiotarsal
bone
– in the proximal and distal epiphysis of the femur
– in the tarsometatarsal bone and in the proximal epiphysis of
the humerus
• Affected: meat-type chicken, duck, turkey

• Characteristics in the long bones:
– in the growth zone of the epiphysis remnant cartilage is
observed without blood vessels
– the abnormal cartilage occurs circumscribed or in the whole
length of the bone
• The cartilage produced in the epiphysis
– does not contain blood vessels
– no calcification is seen
– It does not develop to osteoid and later bone tissue
• The bone are soft, weak, bend under the body weight
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Photo: Dr. Dobos-Kovács, Mihály
Dyschondroplasia
Dyschondroplasia
• Causes
– Genetic factors
• fast growing hybrids
– 5-6 week-old chickens, from 11 weeks of age in turkey
– Malnutrition
• lack of Cu, vitamin C and D
– 1,25-dihydroxicholecalciferol -active metabolite
• fusarochromanon toxisosis, acidosis, inadequate Ca-P ratio
– Husbandry problems
• Light programs with constant lightning
• Special form:
– turkey’65 syndrome (TS-65 syndrome)
– usually follows Mycoplasma meleagridis infection
– in the proximal epiphysis of the tibiotarsal bone
– the epiphysis does not turn to osteoid, later bone
– tibia bends, forms typical „O” shape

Remnant
Remnant
of
of
embryonic
embryonic
cartilage
cartilage
• In long bones and vertebrae
– in newly hatched birds (ostrich,
emu, nandu, great bustard)
– in day-old gooslings aswell
– starting from the epiphysis trough
the metaphysis into the
diaphysis:
– bluish-gray cartilage replaces the
bone marrow
– The cartilage resembles the
normal embryonic cartilage
• this embryonic cartilage is
observed in ratites up to 8 weeks
of age
• In gooslings from the end of the
first week bone marrow is seen
instead of the embryonic cartilage
• This is not dyschondroplasia!
Photo: Dr. Dobos-Kovács, Mihály
Necrosis
Necrosis
of

of
the
the
bone
bone
• Due to circulatory disturbances
– The circulatory disturbances are caused by
• burn, frost bite, trauma, thrombosis,
inflammation
• Femoral head necrosis
– The head of the femur necrotizes due to lack
of enough blood (nutrient) supply
– this lesion is often seen in case of
malsecretion, maldigestion, malabsorption
syndrome
• often in broilers