Bone Infections For PM

Infections of Bone
(Osteomyelitis)
Definition:
 Inflammation of bone and marrow
cavity.
 The most common etiologic agents:

1-pyogenic bacteria
2-mycobacterium tuberculosis.
A. Pyogenic Osteomyelitis
(Pyogenic infection of bone and marrow cavity)
Predisposing factors:
1-Age: More common in children
2-Sex: Boys are more susceptible than

girls.
3-Trauma: Its frequency increases
after compound fractures or orthopedic
surgical procedures.
 4-Immunodeficiency and debility
 5-Intravenous drug abusers
 6-Osteomyelitis may develop in an

otherwise healthy individual
without a known primary infection.
:Causative organisms
 Staphylococcus aureus in 80%-

90% of cases.
 Inup to 50% no organism could

be isolated.
:Routes of infection
 1-Haematogenous spread: Is the most

common route of infection e.g. from a
boil, otitis media or tonsillitis.
 2-Direct extension: From a neighboring
infection e.g.soft tissue abscess and
suppurative arthritis.
 3-Direct inoculation (implantation) of
the organism in surgery or open fracture
:Sites
 Metaphysis of long bones (distal

femur, proximal tibia, proximal
humerus, and distal radius), due
to high vascularity and liability to
trauma.
 Vertebrae, clavicle, and ribs.
 In hematogenous spread, the
infection usually starts in the marrow
cavity (because it is the site of the
slowest capillary flow where the
organisms are most likely to settle
out).
 In direct spread or implantation
(due to trauma), the initial infection
starts as periosteitis followed by
osteitis then the bone marrow is
affected.
:Pathogenesis and morphology
 a. Acute osteomyelitis
Suppurative reaction in the
bone marrow.
 the infection extends to the
periosteum
 Then in a longitudinal
direction along the bone
shaft.
In children
periosteum is
loosely attached to
cortex
periosteal
abscess
opening to the
surface leading to
sinus formation.
Sequestrum
 Definition:
Necrosis of the segment of bone
 Pathogenesis :
 the inflammatory exudation and edema

will lead to compression of the blood
vessels.
 Vascular thrombosis, suppurative and
ischemic injury will lead to necrosis of
the segment of bone affected
Fate :
1-Sequestrum may be:
resorbed (if it is small)
 larger ones are surrounded by a

rim of reactive bone and called
"involucrum".
sloughed to form a free foreign
body that may dissect through a
sinus in the skin
removed surgically
2-The joint cavity:
there is non-suppurative effusion
 the joint is spared.
3-Head of the bone, epiphysis, or joint cavity

infection do not extends (because the periosteum
is firmly attached to the articular margins)
.
4- Suppurative arthritis in infants less than one year:
the periosteum is loosely attached and the epiphyseal
cartilage is traversed by capillaries so that both
subperiosteal and transepiphyseal spread of infection
b-Chronic osteomyelitis:
 Develops as a sequel of acute
infection.
 In the course of time, acute
reaction is followed by a reparative
reaction (including osteoclastic
activation, fibroblastic proliferation,
and new bone formation).
 Brodie's abscess
 When a residual abscess

is surrounded by a rim of
sclerotic bone it will form
what is called "Brodie's
abscess"
 Clinical features:
 Acute pyogenic osteomyelitis
presents by:
 Systemic manifestations: fever,
malaise, and leukocytosis.
 Local : pain, swelling, redness,
tenderness and sometimes
discharging pus occur.
Complications of pyogenic
:osteomyelitis
I. Local complications:
Brodie's abscess
Sinus formation
If the epiphyseal cartilage is destroyed,
growth is retarded
Spontaneous fracture of the weakened
bone.
Septic arthritis
Squamous cell carcinoma within sinus
tracts.
II. Systemic complications:
Septic focus.
Pyemia and pyemic abscesses.
Reactive systemic amyloidosis.

B. Tuberculous Osteomyelitis
Routes of infection:
 Hematogenous spread: It
originates from a focus of active
pulmonary disease.
 Direct extension: From a caseous
focus in the lung to the rib or
extension of infection from caseating
mediastinal lymph nodes to the
vertebrae.
Sites:
Bones affected are:
Spine especially of thoracic and
lumbar vertebrae.
Knees and hip affecting the growing
end of long bones
Small bones of feet and hands.
 The lesion is usually solitary, but in
AIDS it may be multicentric.
 Affects children and young adults.
 Insidious onset and chronic course.
 More destructive than pyogenic
osteomyelitis and more resistant to
control
 Morphology and
pathogenesis:
 starts in the
marrow cavity
 causes extensive
inflammation and
necrosis of the cortex
of bone
 multiple skin
sinuses.
Tuberculosis (Pott's Disease) Of The
Spine Tuberculous Spondylitis
 It affects children
and young adults.
 Males are more
affected than
females.
 The vertebrae
affected are the
thoracic, followed by
the lumbar, then the
cervical.
 The infection starts
in the centre of the
vertebrae destroys
their bodies, and
extends through
epiphyseal cartilage
into the joint space
destroying the
intervertebral discs
thus infecting more
than one vertebra
 Morphology:
Grossly,
destructive, caseous,
necrotizing reaction
with characteristic
large areas of cheesy,
granular, necrotic
debris.
 Microscopically, both destructive
and reparative processes are present
at the same time accompanied by
caseous necrosis and tubercles.
:Fate and complications
 1-Severe destruction
of the vertebrae:
 Leads to compression
fractures with collapse and
deformity of bone:
 in front (kyphosis)
 to one side (scoliosis). his
will lead to permanent
damage because the
reactive bone formation
will fix the spines of the
vertebrae in this
malposition
 2-Tuberculous exudation: May extend
from the vertebral bodies into the
paravertebral muscles, and along the
psoas muscle to produce
 "psoas abscess".
 This abscess does not contain pus, but it
contains caseous material i.e. “
 cold abscess".
3-Pott's paraplegia:
follow tuberculous spondylitis
from compression of the spinal
cord by:
 extradural abscess
granulation tissue
sequestrated bone
disc material
 intradural abscess formation, or

it may involve the cord directly.
4-Secondary amyloidosis.
Tuberculous Dactylitis
 Tuberculosis of the small bones

of the feet and hands
 manifested by fusiform swelling
of the digits due to subperiosteal
reactive bone formation.
 The shafts of the phalanges and
metacarpals are destroyed and
replaced by tuberculous
granulomatous reaction.

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Infections of Bone

 The most common etiologic agents:

(Pyogenic infection of bone and marrow cavity)

2-Sex: Boys are more susceptible than

 5-Intravenous drug abusers

 6-Osteomyelitis may develop in an

 Staphylococcus aureus in 80%-

 Inup to 50% no organism could

 1-Haematogenous spread: Is the most

 Metaphysis of long bones (distal

 the inflammatory exudation and edema

 larger ones are surrounded by a

3-Head of the bone, epiphysis, or joint cavity

 When a residual abscess

Pyemia and pyemic abscesses.

Reactive systemic amyloidosis.

 intradural abscess formation, or

 Tuberculosis of the small bones

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