Case-Based Discussion: Lower Limb Infection, Bone, and Joints and Muscle

Question 1

What is the most common causative organism of osteomyelitis in adults?

Answer 1

Staphylococcus aureus.

Question 2

In which population is hematogenous osteomyelitis most commonly seen, and where does it usually occur?

Answer 2

Most common in children, affecting the metaphysis of long bones.

Question 3

What radiological sign is commonly associated with chronic osteomyelitis?

Answer 3

Sequestrum (dead bone) surrounded by involucrum (new bone).

Question 4

Which joint is most commonly affected in septic arthritis?

Answer 4

The knee joint.

Question 5

What are the key clinical features of septic arthritis?

Answer 5

Acute onset of joint pain, swelling, warmth, and restricted movement.

Question 6

What is the gold standard for diagnosing septic arthritis?

Answer 6

Joint aspiration and synovial fluid analysis (including Gram stain and culture).

Question 7

Name three key risk factors for septic arthritis.

Answer 7

Immunosuppression, joint prosthesis, and pre-existing joint disease (e.g., rheumatoid arthritis).

Question 8

What is the initial empirical antibiotic therapy for septic arthritis?

Answer 8

Empirical therapy with intravenous antibiotics targeting Staphylococcus aureus (e.g., cefazolin or vancomycin).

Question 9

What is necrotizing fasciitis, and why is it considered a surgical emergency?

Answer 9

A rapidly spreading soft tissue infection that destroys fascia and subcutaneous tissue, requiring immediate debridement to prevent sepsis and death.

Question 10

What are the common causative organisms of necrotizing fasciitis?

Answer 10

Group A Streptococcus (Streptococcus pyogenes), Clostridium species, and polymicrobial infections.

Question 11

What is the hallmark clinical feature of gas gangrene, and which organism is typically responsible?

Answer 11

Crepitus due to gas production in soft tissues; caused by Clostridium perfringens.

Question 12

How does osteomyelitis typically spread to bones?

Answer 12

Hematogenous spread, direct inoculation (e.g., trauma, surgery), or contiguous spread from nearby infections.

Question 13

What are two major complications of untreated chronic osteomyelitis?

Answer 13

Pathological fractures and squamous cell carcinoma (Marjolin’s ulcer).

Question 14

Why are diabetic patients at higher risk for developing osteomyelitis in the lower limb?

Answer 14

Due to peripheral neuropathy, poor circulation, and immunosuppression.

Question 15

What is a Charcot joint, and how is it related to infection?

Answer 15

A neuropathic joint disease causing progressive destruction, often seen in diabetics and mistaken for infection.

Question 16

What is pyomyositis, and which organism is most commonly responsible?

Answer 16

A bacterial infection of skeletal muscles, typically caused by Staphylococcus aureus.

Question 17

What imaging modality is most sensitive for detecting early osteomyelitis?

Answer 17

MRI

Question 18

What are the mainstays of treatment for osteomyelitis?

Answer 18

Long-term antibiotic therapy and surgical debridement.

Question 19

Which bones are most commonly affected by tuberculous osteomyelitis?

Answer 19

The vertebrae (Pott’s disease), long bones, and weight-bearing joints.

Question 20

What are typical laboratory findings in a patient with acute osteomyelitis?

Answer 20

Elevated white blood cell count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).

Question 21

What is the most common causative organism of gonococcal septic arthritis?

Answer 21

Neisseria gonorrhoeae.

Question 22

How does gonococcal septic arthritis typically present?

Answer 22

It presents as migratory polyarthritis or monoarthritis, often accompanied by tenosynovitis and dermatitis.

Question 23

What is the diagnostic gold standard for gonococcal septic arthritis?

Answer 23

Synovial fluid culture and nucleic acid amplification tests (NAAT) for Neisseria gonorrhoeae.

Question 24

What is the recommended treatment for gonococcal septic arthritis?

Answer 24

Intravenous ceftriaxone followed by oral antibiotics once symptoms improve, along with treatment for concurrent sexually transmitted infections.

Question 25

What are the key differences in clinical presentation between gonococcal and non-gonococcal septic arthritis?

Answer 25

Gonococcal septic arthritis is typically polyarticular and associated with skin lesions, while non-gonococcal septic arthritis is usually monoarticular and more destructive.