Patho Exam 2 Osteonecrosis and osteomylitis Flashcards Preview

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Flashcards in Patho Exam 2 Osteonecrosis and osteomylitis Deck (16)
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Avascular necrosis or aeptic necrosis


What is osteonecrosis and its causes?

Loss of blood supply to bone resulting in death of the tissue ISCHEMIA!

o Death of the bone and the marrow in the absence of infection!
• Osteomyelitis can cause necrosis but it due to infection.


what are some of the causes of osteonecrosis

• Trauma – blood vessels ruptured, decreased blood supply

• Steroids – do not allow growth of blood vessels or collagen, may have > purport

• Thrombus/embolism

• Vessel injury/radiation

• Increased intra-osseous pressure → vascular compression: Tumor around bone would increase pressure causing vascular compression

• Venous hypertension: Not draining that part and therefore blood is not going in or out, its just pooling


What are the two types of infacts that arise with osteonecrosis?

Medullary (center): Involve cancellous bone and marrow (hematopoietic bone)
• Cortex is not affected because of its collateral blood flow

Subchondral: Cause triangular segment of tissue undergoes necrosis
-Overlying articular cartilage remains viable as it receives nutrition from synovial fluid (glucose, ions, etc.)


Medullary Necrosis may present silent except for when?

• Present clinically silent except for large ones occurring in Gaucher disease (autoimmune disease), dysbarism (change in pressure – scubadiving), sickle cell anemia
• Remains stable over time


How will Subchondral Necrosis present?

-Present with pain that is initially associated only with activity but becomes progressively more constant as secondary changes occur

-Often collapse and predispose to severe, secondary osteoarthritis

-More than 10% of joint replacements performed are for treatment of complications of osteonecrosis.



PYOGENIC Bacterial Osteonecrosis

What type of bacteria is the cause of osteomyelitis? Remember pyogenic=bacterial

o Staph is most common (80-90%)
E. coli, pseudom, kleb-

think bacteria you will get pus and fever


more common with GU infections or IVDA

E. Coli, pseudo, kleb


Mixed infection common in

Mixed infection common in surgical procedures or open fractures
• Due to mixed infections on skin that are brought inside, into bone


in neonates

H. influ and group B strep


common with sickle cell



Routes in which things get in the bone
Pyogenic transfer

Other 2 types

o Hematogenous: most common site is metaphyseal area due to rich blood supply. Most common source in otherwise healthy children.
If No abrasion, laceration over this bone, how did it arise? This area of bone is so vasculature, any organism that gets into body (dental abrasion), is a route for anything to get into bloodstream and cause osteomyelitis.

Contiguous: Compound fracture

Direct implantation: Surgical route, not aseptic technique

TB : Usually blood borne- spine (most common place affected) is known as POTTS disease

Syphilis: “Sabre” shins, Congenital (kids can get it from mother transferring to the fetus)
Tertiary: Long term. (SABRE SHINS), shins look like sabre saws


Vertebral osteomyelitis is associated with

septicemia, bacterial arthritis, pathologic fracture, squamous cell carcinoma, and amyloidosis.


How do you diagnose osteomyelitis?

X-ray, Bone scan


What are complications of osteomyelitis?

Subperiosteal abscess

Draining sinus: Cloaca is the hole formed in the bone during formation of a draining sinus that eventually can go out to the surface of the skin.

Meduallary infection can go out the cortex and to surface of skin

Joint involvement


What is the difference of sequestrum and involvucrum

Sequestrum is fragments of necrotic bone embedded in the pus (WBC that died off) Depending on where this is, may need surgery.
If involve joint → surgery

Involucrum forms a sheath around necrotic sequestrum. Encapsulated new bone around necrotic area.