Case-Based Discussion: Lower Limb Infection, Bone, and Joints and Muscle Flashcards
What is the most common causative organism of osteomyelitis in adults?
Staphylococcus aureus.
In which population is hematogenous osteomyelitis most commonly seen, and where does it usually occur?
Most common in children, affecting the metaphysis of long bones.
What radiological sign is commonly associated with chronic osteomyelitis?
Sequestrum (dead bone) surrounded by involucrum (new bone).
Which joint is most commonly affected in septic arthritis?
The knee joint.
What are the key clinical features of septic arthritis?
Acute onset of joint pain, swelling, warmth, and restricted movement.
What is the gold standard for diagnosing septic arthritis?
Joint aspiration and synovial fluid analysis (including Gram stain and culture).
Name three key risk factors for septic arthritis.
Immunosuppression, joint prosthesis, and pre-existing joint disease (e.g., rheumatoid arthritis).
What is the initial empirical antibiotic therapy for septic arthritis?
Empirical therapy with intravenous antibiotics targeting Staphylococcus aureus (e.g., cefazolin or vancomycin).
What is necrotizing fasciitis, and why is it considered a surgical emergency?
A rapidly spreading soft tissue infection that destroys fascia and subcutaneous tissue, requiring immediate debridement to prevent sepsis and death.
What are the common causative organisms of necrotizing fasciitis?
Group A Streptococcus (Streptococcus pyogenes), Clostridium species, and polymicrobial infections.
What is the hallmark clinical feature of gas gangrene, and which organism is typically responsible?
Crepitus due to gas production in soft tissues; caused by Clostridium perfringens.
How does osteomyelitis typically spread to bones?
Hematogenous spread, direct inoculation (e.g., trauma, surgery), or contiguous spread from nearby infections.
What are two major complications of untreated chronic osteomyelitis?
Pathological fractures and squamous cell carcinoma (Marjolin’s ulcer).
Why are diabetic patients at higher risk for developing osteomyelitis in the lower limb?
Due to peripheral neuropathy, poor circulation, and immunosuppression.
What is a Charcot joint, and how is it related to infection?
A neuropathic joint disease causing progressive destruction, often seen in diabetics and mistaken for infection.
What is pyomyositis, and which organism is most commonly responsible?
A bacterial infection of skeletal muscles, typically caused by Staphylococcus aureus.
What imaging modality is most sensitive for detecting early osteomyelitis?
MRI
What are the mainstays of treatment for osteomyelitis?
Long-term antibiotic therapy and surgical debridement.
Which bones are most commonly affected by tuberculous osteomyelitis?
The vertebrae (Pott’s disease), long bones, and weight-bearing joints.
What are typical laboratory findings in a patient with acute osteomyelitis?
Elevated white blood cell count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
What is the most common causative organism of gonococcal septic arthritis?
Neisseria gonorrhoeae.
How does gonococcal septic arthritis typically present?
It presents as migratory polyarthritis or monoarthritis, often accompanied by tenosynovitis and dermatitis.
What is the diagnostic gold standard for gonococcal septic arthritis?
Synovial fluid culture and nucleic acid amplification tests (NAAT) for Neisseria gonorrhoeae.
What is the recommended treatment for gonococcal septic arthritis?
Intravenous ceftriaxone followed by oral antibiotics once symptoms improve, along with treatment for concurrent sexually transmitted infections.
What are the key differences in clinical presentation between gonococcal and non-gonococcal septic arthritis?
Gonococcal septic arthritis is typically polyarticular and associated with skin lesions, while non-gonococcal septic arthritis is usually monoarticular and more destructive.
