Osteomyelitis Flashcards
Osteomyelitis Definition
An inflammation of bone, usually cause by bacteria (occasionally by mycobacteria) but sometimes by fungi.
Osteomyelitis Pathogensis Spread
- Haematogenous spread
- Extension of contiguous infection
- Direct Surgical/Traumatic introduction
- Diabetes
Main sources of bacteria in haematogenous osteomyelitis are infections of?
- Cutaneous
- Dental
- Sinus
- Aural
Typical case description of osteomyelitis?
- Previously healthy, active individual
- Osteomyelitis caused by Staphylococcus Aures which reached the bone haematogenously
- No apparent point of entry for the microorganism
- The bacteraemia is subclinical
Haematagenous bacteria entry common in?
a. Infants
b. Children
c. Elderly
Haematogenous Osteomyelitis Pathogenesis
- Subclinical transient bacteraemia
- Bacteria reaches the bone; an acute inflammatory focus develops in the bone.
- Necrosis of bone fragments
- Reactive bone Growth
- Sinus Formation
Haematogenous Osteomyelitis Pathogenesis Stage 1?
-Subclinical transient bacteraemia (source often unknown)
Haematogenous Osteomyelitis Pathogenesis Stage 2
- Bacteria reaches the bone; an acute inflammatory focus develops in the bone.
a. Children = metaphysis of long bones
b. Adults = spine, pelvis or small bones
Haematogenous Osteomyelitis Pathogenesis Stage 3
- Necrosis of Bone Fragments:
- The inflammation spread (oedema) spreads through the Haversian canals and compresses adjacent vessels
- Vascular thrombosis occurs followed by osteonecrosis
- The dead bone separates from the living and is called the Sequestrum
Haversian Canals
Are a series of microscopic tubes in the outermost region of bone called cortical bone that allow blood vessels and nerves to travel through them.
Each haversian canal generally contains one or two capillaries and nerve fibres. The channels are formed by concentric layers called lamellae.
The haversian canals surround blood vessels and nerve cells throughout bones and communicate with bone cells (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculi.
Haematogenous Osteomyelitis Pathogenesis Stage 4
Reactive Bone Growth
A. in children the inflammatory exudate may extend to the surface of the cortical bone; abscesses and oedema form and may cause periosteal elevation
B. Periosteal elevation disrupts blood vessels that enter the bone from the periosteum thus depriving the bone of a bloody supply.
C. Lifting of the periosteum also stimulates intense osteoblastic activity that results in the formation of new bone (the involcrum) which may surround the infected bone
Involcrum
Involucrum (plural involucra) is a layer of new bone growth outside existing bone seen in pyogenic osteomyelitis. It results from the stripping-off of the periosteum by the accumulation of pus within the bone, and new bone growing from the periosteum.
Haematogenous Osteomyelitis Pathogenesis Stage 5
Sinus Formation:
-Pus and necrotic tissue from the infection focus may drain towards the skin surface. The superficial drainage sit is called a CLOACA
Haematogenous Osteomyelitis Pathogenesis Adults Vs Children?
Reactive bone, periosteal elevation and sinus formation are rare in adults because growth is rare. Growth is rare because the periosteum is firmly attached to the coretex and resists displacement.
In Adults osteomyelitis disrupts and weakens the cortex, predisposing it to pathological fractures.
Clinical manifestations depend on?
- Age of patient
- Site of Involvement
- Initiating Event
- Infecting Organism
- State of Condition (If the infection is acute, subacute or chronic)
