Infection of Bone and Joints

Question 1

Define osteomyelitis

Answer 1

Infection of the bone

Question 2

Microbiology of osteomyelitis:

Answer 2

Common:

• Staphylococcus aureus (Most common)
• Coagulase-negative staphylococci

Occasionally: streptococci, enterococci, gram-negative bacteria, and anaerobes

Rarely: mycobacterium (including TB), brucella species, salmonella species and fungi

Question 3

Investigations for osteomyelitis

Answer 3

• Elevated ESR and C-reactive protein (indicative of systemic infection)
• Blood culture for haematogenous bacteria
• Bone biopsy (best test when possible)
• Local swabs are done, but very misleading (show superficial bacteria)

Question 4

Medical imaging of osteomyelitis

Answer 4

• X-ray -> useful if chronic; bone irregularity and periosteal separation
• Nuclear imaging -> uptake of technetium element indicates osteomyelitis
• CT scan -> shows soft tissue and bone; better than x-ray but more radiation
• MRI -> Best imaging; shows bone marrow abnormality; highly specific and sensitive

Question 5

Describe the different types of osteomyelitis

Answer 5

• Haematogenous osteomyelitis -> Bacteria reach infection site through blood stream; high risk of endocarditis if bacteria in blood
• Vertebral osteomyelitis rapid onset of localized back pain; not responsive to analgesics
• Open fracture osteomyelitis -> fracture contaminated at time of accident; non-union occurs when surgically implanted supports (e.g. plates and screws) become infected
• Vascular insufficiency osteomyelitis -> poor vascular supply leads to inadequate healing; minor traumas can lead to ulcers that can spread to bone (e.g. foot ulcer in diabetes)
• Tuberculous osteomyelitis -> chronic, affects spine usually, TB therapy is effective but deformities remain

Question 6

Treatment for these different types of osteomyelitis

Answer 6

Antibiotic therapy -> use cultures from bone biopsy to target antibiotics:

• IV antibiotics for aggressive cases
• Oral antibiotics over long term

Analgesics to manage pain.

Question 7

Define septic (infectious) arthritis

Answer 7

Joints become infected, leading to arthritis

Question 8

Microbiology of septic (infectious) arthritis

Answer 8

Bacteria:

• Streptococci
• Staphylococcus aureus
• N. gonorrhoeae
• Animal/tick bites

Viruses:

• Parvovirus
• Rubella
• Hepatitis
• HIV

Tuberculosis
Non-candida fungi

Question 9

Symptoms of septic (infectious) arthritis

Answer 9

• Focal joint tenderness and inflammation
• Limited range of motion
• Distant infectious source

Question 10

Investigations for septic (infectious) arthritis:

Answer 10

• Raised white cell count
• Breath culture
• Blood culture
• Urine culture

Question 11

Treatment for septic (infectious) arthritis

Answer 11

• Surgically remove infectious fluid from joint
• Antibiotic diffusion into joint
• Shorter treatment than osteomyelitis