Bone Infection (Acute, Subacute and Chronic Osteomyelitis, Acute Septic Arthritis, Tuberculous Osteomyelitis) Flashcards
How can bone infections spread?
Can occur from metastatic haematogenous spread (carried in the blood), or from local infeciton. They can also occur 2o to vascular insufficiency.
What organisms most commonly affect infants (<1yr)?
- Staph aureus
- Group B streptococci
- E. coli
What organisms commonly affect older children up to age of 4?
- Staph aureus
- Strep pyogenes
- Haemophilus influenzae
- Kingella kingae
What organisms commonly affect Adults?
- Staph aureus
- Coag negative staphylococci - prostheses
- Propionibacterium spp - prostheses
- Streptococcus pyogenes - infectious arthritis
- Mycobacterium tuberculosis
- Pseudomonas aeroginosa - esp. secondary to penetrating foot injuries, IVDAs
What is the pathogenesis of osteomyelitis?
The classical sequence of changes in osteomyelitis is as follows:
- Transient bacteraemia - e.g. Staphylococcus aureus
- Focus to metaphysis of long bone
- Acute inflammation - increased pressure within haversian canals in cortical bone and under periosteum ⇒ periosteum lifts off and interrupts blood supply to underlying bone
- SEQUESTRUM - Caused by necrosis of bone fragments
- INVOLCURM - New reactive bone formation created by the elevated periostium
-
Outcome ⇒ resolution or chronic osteomyelitis
- If untreated, sinuses form, draining pus to the skin surface via cloacae ⇒ Chronic Osteomyelitis
Predisposing conditions to osteomyelitis
- diabetes mellitus
- sickle cell anaemia
- intravenous drug user
- immunosuppression due to either medication or HIV
- alcohol excess
How do bone Abscesses form?
- Acute inflammatory response ⇒ granulation tissue ‘walls off’ sequestrum
- Bacterial proliferation in dead tissue ⇒ pressure & toxins
- Adjacent healthy bone devascularised, further destruction
- Fibrous membrane forms around abscess
- Reactive bone forms ⇒ involucrum ⇒ Bacteria isolated from host defences!
What is the pathophysiology of Chronic osteomyelitis?
- Cavities, poss. sinus(es)
- Cloacae
- Sequestrum + involcrum + sinus
What is the pathophysiology of Septic arthritis?
- Acute synovitis with purulent joint effusion
- Articular cartilage attacked by bacterial toxin and cellular enzyme
- Complete destruction of the articular cartilage
-
Sequelae (1 of the following):
- Complete recovery
- Partial loss of the articular cartilage and subsequent OA
- Fibrous or bony ankylosis
What is the pathophysiology of Tuberculous Arthritis?
- 2 phases
- Early short lived vascular
- Chronic avascular
- Obliterative endarteritis - poor entry of antibiotics
- Less plasminogen activation - less joint destruction
- Primary complex (in the lung or the gut)
- Secondary spread
- Tuberculous granuloma
What are the clinical features of Acute Osteomyelitis in infants?
May be minimal signs, or may be very ill
- FTT
- Possibly drowsy or irritable
- Metaphyseal tenderness + swelling
- Decreased ROM
*Commonest around the knee
What are the clinical feautrues of Acute Osteomyelitis in children?
Vascular bone most affected - long bone metaphyses, esp. distal femur, upper tibia
- Severe pain - May be tender and inlamed
- Reluctant to move - neighbouring joints held flexed
- Not weight bearing
- Fever (swinging pyrexia) + tachycardia
- Systemic features - Malaise fatigue, nausea, vomiting
What are the clinical features of Acute osteomyelitis in an adult?
- Fever
- Localized bone pain - gradual onset over the course of a few days
- Overlying tenderness, warmth and erythema
- Slight effusion in neighbouring joints
What is the presentation of subacute osteomyelitis?
- Long history
- Variable symptoms - pain, limp
- Local swelling/warmth, with Tenderness
- Brodie’s abscess - well defined cavity in cancellous bone
What are the clinical features of Chronic Osteomyelitis?
- Pain
- Fever
- Sequestra - small peice of dead bone separated from live bone
- Sinus suppuration (pathognomic)
-
Risk factors - Diabetic ulcer, Vascular insufficiency
- If bone can be felt on probing ulcer ⇒ CHRONIC OSTEOMYELITIS
What are the clinical features of acute septic arthritis in a neonate?
- Picture of septicaemia
- Irritability
- Resistant to movement
- Ill Child