Pathology - Infections

Question 1

What is (acute) osteomyelitis?

Answer 1

Inflammation to the bone & marrow secondary to infection

Question 2

How does (acute) osteomyelitis manifest?

Answer 2

As a primary solitary foci of disease, but can be complication of systemic infection

Question 3

Clinical Features of (acute) osteomyeltiis?

Answer 3

1. Raised CSR and ERP
2. Pain, Fever, Swelling. other constitutional symptoms

Question 4

What are the locations in the bone of (acute) osteomyelitis?

Answer 4

Bone Cortex, Medulla and Periosteum

Question 5

Radiological Features of (acute) osteomyelitis?

Answer 5

Lytic focus of bone destruction surrounded by sclerosis, with periosteal reaction

Question 6

What organisms commonly cause osteomyelitis?

Answer 6

S. aureus, E. coli, Strep, H. Influenzae, Salmonella, TB

Question 7

Through what routes do microbial agents infect bone?

Answer 7

1. DIrect Implantation
2. Blood
3. Weakened Immunity or vascular insufficiency
4. Extension from contiguous sites

Question 8

What locations of the body do osteomyelitis occur in children and adults?

Answer 8

Children: Long Bones (UL + LL)
Adults: Feet. vertebral spine, femur

Question 9

Pathophysiology of acute osteomyelitis?

Answer 9

1. Infection, proliferation, microabscesses
2. Spread through bone with inflammation (may cause septic arthritis if extends to joint or synovium)
3. Inflammation impedes blood supply to bone causing ischemia and necrosis
4. Inflammatory exudate lifts periosteum away from the bone cortex - forms a involucrum (layer of woven bone that surrounds the dead infected bone)
5. Rupture of periosteum leads to abscess in soft tissue and eventually formation of draining sinus
   *If untreated, structures can form bony deformities

Question 10

Complications of Osteomyelitis (acute)

Answer 10

Impinge on structures (ie spinal cord), Spondylodiscitis: infection of IVD and adjacent vertebrae (2-5% of OM prevelance; M:F=2:1; bimodal distribution (age); site L, T, S, C

Question 11

What are features of spondylodiscites

Answer 11

1. adj, soft tissue swelling
2. Narrow Disc Space
3. End Plate early destruction

Question 12

What percentage of acute osteomyelitis progresses to chronic?

Answer 12

5-25%

Question 13

What are risk factors for progression to chronic osteomyelitis?

Answer 13

1. Weakened Immunity: Diabetes, Dialysis, IV Drug Use, Poor Nutrition, Smoking, Trauma
2. Delay in diagnosis, inadequate antibiotic treatment
3. Incomplete surgical removal of infected or necrotic bone

Question 14

What are complications of chronic osteomyelitis?

Answer 14

1. Extensive bone necrosis –> pathological fracture or deformity
2. secondary amyloidosis
3. sepsis
4. Malignant Transformation : Sarcoma in bone, Squamous Cell Carcinoma in Sinus Tract

Question 15

Imaging of Chronic Osteomyelitis?

Answer 15

1. Radiographs: Thickened irregular sclerotic bone; periosteal bone formation, soft tissue swelling, sequestrum (necrotic bone piece detached)
2. MR: Marrow & Soft Tissue Edema, abscess, sinus tracts

Question 16

ddx for chronic osteomyelitis

Answer 16

neoplasm

Question 17

treatment for chronic osteomyelitis

Answer 17

surgical debridement & parenteral antibiotics

Question 18

What is TB Osteomyelitis

Answer 18

A type of chronic osteomyelitis
- difficult to treat
- spreads from lungs to bone via blood or lymphatics

Question 19

Demographic of TB OM?

Answer 19

Young, Old , immunocompromised, low SES group

Question 20

Features of TB OM

Answer 20

Chronic Inflammation features + Epitheloid Granulomas & Necrosis

Question 21

Spinal TB Osteomyelitis location?

Answer 21

Vertebral Spine (Thoracic and Lumbar)

Question 22

Spinal TB OM complications

Answer 22

Compression fractures, severe deformities (kyphosis, scoliosis), neurological deficits due to cord and nerve compression