Osteonecrosis & Infection Flashcards
What term describes the calcification of normal tissue due to increased serum calcium or phosphorus?
Metastatic calcification
What term describes the calcification of damaged/diseased tissues in a localized fashion?
Dystrophic calcification
What term describes the intramembranous bone formed in response to stress on bone or soft tissue?
Reactive bone formation (periosteal reaction)
Name 4 types of periosteal reaction
solid
laminated
spiculated
Codman’s triangle
What occurs in a solid periosteal reaction?
- slow growing, non-aggressive
- as periosteum is lifted slowly, it fills in completely
What occurs in a laminated periosteal reaction?
- aggressive process
- lifts periosteum, stops, lifts again, etc., (allows layering/onion effect)
- lays down bone during rest phase
What occurs in a spiculated periosteal reaction?
- aggressive process
- periosteum lifted rapidly
- bone growth along Sharpey fibers creates hair-on-end (parallel) or sunburst (outward) appearance
What occurs in a Codman’s triangle periosteal reaction?
- aggressive pattern
- strips periosteum away from adjacent uninvolved bone
What term describes the death of bone and bone marrow in the absence of infection?
Osteonecrosis
What is the most common cause of osteonecrosis?
Infarction (loss of blood supply)
Osteonecrosis of the epiphyseal region is called ____
avascular necrosis (AVN)
Osteonecrosis in the metaphyseal/diaphyseal region is called ____
bone infarct
The inflammation of bone due to a bacterial infection is called?
Osteomyelitis
What is the most common etiology of osteomyelitis?
Staphylococcus aureus
What are the 3 routes of spread for osteomyelitis? Which is most common?
- Hematogenous spread (MC)
- Lymphatic
- Contiguous (direct/implantation)
In the case of hematogenous osteomyelitis, bacteria spread from inside the bone to the subperiosteal space using the ____ and ____ canal systems
Haversian
Volkmann’s
What factors play a role in the severity of a bacterial infection?
- Virulence of the bacteria
- Pre-existing health complications
- Patient’s age
What is the most common form of osteomyelitis that comes from skin pustules or infected teeth or gums?
Hematogenous osteomyelitis
What areas does osteomyelitis most commonly affect?
- metaphyseal regions (most metabolically active)
- lower extremity and hands (blood pooling)
When using the term “osteomyelitis” on its own, the implication is…
acute pyogenic osteomyelitis
What pattern of necrosis is found in tissues undergoing osteomyelitis?
Liquefactive necrosis
What type of edema is produced by the tissue necrosis in osteomyelitis?
Purulent exudate
Describe the pathogenesis of osteomyelitis
- bacteria escape vasculature & proliferate -> local necrosis
- edema results in ^medullary pressure
- ^osteoclast activity in infected area
- necrotic debris lifts periosteum -> reactive bone formation
- periostitis -> loss of blood supply -> necrosis of cortical bone
What term describes an inflammation of the periosteum?
Periostitis
During a bacterial infection, increased edema fluid may put pressure on surrounding capillaries and result in what?
Osteolysis
How long does it take for osteomyelitis to appear on x-ray in the extremities versus the spine?
- extremities: 7-10 days
- spine: 21 days
On a radiograph, what is the area of reactive bone formation when them periosteum is lifted called?
Codman’s Triangle
What is a cloaca?
an opening in the cortex of bone that allows bacteria to spread to other tissues
What is a sequestrum?
a piece of necrotic bone tissue
What is an involucrum?
an area of reactive bone formation that forms a sheath around a sequestrum
What is a sinus?
where pus drains from bone into the outside environment
What are some of the cardinal signs of an acute pyogenic osteomyelitis infection?
- Rapid onset, high fever
- Severe throbbing pain that worsens rapidly
- Swelling and redness
- Sharp cortical line may be lost
How is chronic osteomyelitis characterized?
- reactive bone formation -> enlargement, involucrum, sequestrum
- cloaca & possibly sinus
- multiple lytic lesions (porous appearance)
- can destroy multiple bones and tissues over time
What are some of the possible radiographic characteristics seen with osteomyelitis?
- Lytic areas in cortex and medullary cavity
- Decreased disc space and loss of vertebral endplates
- Decreases vertebral height due to pathologic fracture
What are some of possible radiographic characteristics seen with vertebral osteomyelitis?
- decreased/obliterated disc space
- loss of vertebral endplates
- pathological fracture if vertebra
- Favors thoraco-lumbar region, but can be anywhere
- in kids: disc -> vertebrae
- adults: vertebrae -> disc
If multiple bones and tissues are involved, ____ MUST be on your DDX until proven otherwise
infection
What are some of the possible laboratory findings that can help diagnose vertebral osteomyelitis?`
- Leukocytosis
- Elevated ESR and C-reactive protein
What are the possible clinical characteristics of osteomyelitis?
- possible cardinal signs
- pathological fracture
- bone enlargement over time
- squamous cell carcinoma (Marjolin Ulcer) along draining sinus or cloaca
- bone sarcoma
What are the risk factors for spondylodiscitis/vertebral osteomyelitis?
- hematogenous spread from other sites
- intravenous drug use
- upper urinary tract infections
- urological procedures
- diskitis
What is a Brodie’s Abscess?
- subacute metaphysical infection of bone
- reactive bone that surrounds & contains infection
A Brodie’s abscess may result in ____ of the lesion
sterilization
What Hematogenous route does tuberculosis infections utilize to spread to bone? Why?
- Batson’s venous plexus
- basivertebral vv don’t have valves -> blood can flow backwards)
What pattern of inflammation is associated with tuberculosis infections?
Chronic inflammation
What morphological pattern of inflammation is associated with tuberculosis infections?
Granulomatous inflammation
What pattern of necrosis is associated with tuberculosis infections?
Caseous necrosis
What parts of the spine are affected by a tuberculosis infection?
destruction of vertebral body with sparing of discs
What parts of the spine are affected by vertebral osteomyelitis?
destruction of vertebral body and discs
If tuberculosis infection ruptures into soft tissue, this can cause ____
Cold abscesses
What are cold abscesses and how do they appear on x-ray?
- abscesses lacking acute inflammation (subligamentous extension = skip lesions)
- snowflake sign: white dots along psoas muscle
What term describes a sharply angled kyphosis in the thoracic spine often seen in Tuberculosis infections?
Gibbous deformity
(vertebral collapse and destruction of vertebral bodies)
What are the clinical manifestations of Tuberculosis?
- insidious onset (mild -> severe), stiffness
- focal tenderness, decreased ROM in spine
- spinal pain w/ or w/out neuro involvement
- cold (psoas) abscesses
- Gibbous deformity
- paraplegia from vascular insufficiency of spinal nn
A patient walks into your clinic complaint of pain and stiffness in the spine. They have decreased ROM and notice a hyperkyphosis of the spine as they walk in. What is a possible condition you suspect is wrong with the patient?
Tuberculosis infection
What is the etiology of Syphilis?
Treponema pallidum
What are some of the clinical manifestations of an acquired syphilis infection?
- Saddle nose
- Sabre shin
- Gummas
- bone erosion
- neurological symptoms
What term descirbes a granulomatous lesion with a central area of coagulative necrosis, epithelioid macrophages, and giant cells surrounded by fibrous tissue?
Gummas
What condition is the sign Sabre shin most commonly associated with?
Syphilis
What prominent signs are specific to congenital syphilis infection?
- Hutchinson’s teeth
- neurological symptoms -> milestone delays
What is the result of a dislocated epiphysis caused by a treponema pallidum growth plate infection that leads to a functionless limb?
Pseudoparalysis of Parrot
