Flashcards in Bone and Joint Infections Deck (19)
What is the osteomyelitis?
Infection of the bone
What are the 3 mechanisms by which bone infections can occur?
Haematogenous - bacteria in the blood seed bone
Contiguous-focus - spread from adjacent area of infection
Direct Inoculation - trauma or surgery
How are the 4 anatomical classifications of bone infection?
Stage I - medullary - necrosis confined to the medulla
Stage 2 - superficial - necrosis limited to exposed surface
Stage 3 - localised - full thickness destruction of cortical elements of bone - need surgery to get rid of infected bone and pus - antibiotics alone will not work
Stage 4 - diffuse - extensive, unstable bone
What are the clinical features of osteomyelitis?
-Persistent pain (not just mechanical)
-Soft tissue swelling
-Reduced movement of affected limb
- Systemic upset UNCOMMON (fever, chills, night sweats)
What is the most common cause of osteomyelitis?
Usually single organism
- Staph Aureus = most common
- Streptococci A/B
- Gram negative bacilli - e.g. pseudomonas = more common in infants/babies
What laboratory investigations should be performed with osteomyelitis?
Cultures and histology of bone biopsy/needle aspirate (superficial swabs not great!)
What are the diagnostic features of osteomyelitis?
C-reactive protein raised
Leukocytosis - not diagnostic
What are the therapeutical options for osteomyelitis?
- CLINDAMYCIN - staph aureus
-Ciproflaxcin - gram negatives (pseudomonas)
- Vancomycin - gram positive (strep cocci, enterococci)
Gentamicin (Beta lactams)
FLUCOXACILLIN = treatment of choice for staph aureus osteomyelitis
What is the term meaning inflammatory reaction in joint space by infection?
What is the classification system for direct infection?
Native (natural joint infection) vs prosthetic (artificial) joint infection
What is the pathogenesis of septic arthritis in native joint?
Organisms enter joint via blood or trauma
Synovial joint is highly vascular and lacks basement membrane - facilitates seeding
Cartilage erosion causes joint space narrowing/impaired function
What is the pathogenies of septic arthritis in prosthetic joint?
- Organisms enter a joint via the blood during surgery/wound infection
- Joint prosthesis and cement provide a surface for bacterial attachment
- Polymorph infiltration results in tissue damage instability of the prosthesis
What is the clinical presentation of septic arthritis?
Joint: pain, swelling, tenderness, redness and movement limitation
System upset: fever, chills, night sweats
Duration of symptoms is variable, dependent on site and organism
What are the causative bacterial organisms for septic arthritis in native joint?
Strep A (pyogenes), B, C, G
NATIVE = N species
What are the causative bacterial organism for prosthetic joint infections
Step A, B, C, G
Coagulase negative staph (CoNS)*
*skin flora/in environment
What are the diagnostic features of septic arthritis?
Total white cell count increased
- Polymorphs increased
- Gram stain (35-65%) positive
Crystal examination (check for gout)
What is the therapy for native joint infection?
Removal of pus/purulent material (joint drainage/washout)
Empirical IV antimicrobial therapy
Direct IV antimicrobial therapy depending on causative organism
What is the therapy for prosthetic joint?
If loose/late, removal of impact or replacement of elements - washout
Empirical (broad) IV antimicrobial therapy
Directed (specific) IV antimicrobial therapy depending on organism