Infection in Bone 1: Acute & Chronic Osteomyelitis Flashcards
Who tends to get acute osteomyelitis?
Mostly children
- Adults with comorbidity (diabetes, rheum arth. immune compromise)
How does acute osteomyelitis tend to spread?
- Haematogenous spread (most common in children and elderly)
- Local spread from site of infection (surgery / open fracture / joint replacement)
- Secondary to vascular insufficiency
- Infected umbilical cord / boils / abrasions / UTIs / arterial line
What organism is the most common cause of acute osteomyelitis?
Staph Aureus
What are some other organisms that cause osteomyelitis in children and adults?
Children:
- Group B Strep / E. Coli / Strep pyogenes
Adults:
- Coagulase negative staphylococci & propionibacterium spp (both common in prostheses)
- Myobacterium TB / pseudomonas aeroginosa
What are the common sites for acute osteomyelitis to occur?
Metaphysis of long bones
- Distal femur / proximal tibia / proximal humerus
Joints with intra-articular metaphysis:
- Hip / radial head of elbow
Describe the progression of an acute osteomyelitis infection
- Starts at metaphysis
- Causes vascular stasis
- Inflammation & suppuration (increases pressure)
- Release of pressure (sub-periosteal / into joint etc)
- Sequestrum +/- Involucrum (necrosis of bone +/- formation of new bone)
- Resolution OR Chronic osteomyelitis
How does acute osteomyelitis tend to present in infants?
- Failure to thrive
- Metaphyseal tenderness & swelling (swelling not immediately visible, later stage sign)
- Decreased ROM
- Positional change of limb / joint (stop pain)
- Commonest around knee
- Infants < 1 month old often present with multiple sites of infection
How does acute osteomyelitis tend to present in children?
- Severe pain
- Reluctant to move (neighbouring joints held flexed, avoid weight bearing)
- Fever (swinging pyrexia) / tachycardia
- Malaise / nausea / toxaemia
How does acute osteomyelitis tend to present in adults?
- Thoracolumbar spine is most common area: complain of backache
- History of UTI / urological procedure / diabetes / immunosuppression / are elderly
What is the most common type of acute osteomyelitis in adults?
Secondary acute osteomyelitis
- After surgery (ORIF) / open fractures
- Commonly see a mixture of organisms in these patients
What investigations are used for suspected acute osteomyelitis?
- ESR / CRP / FBC (neutrophil leucocytosis)
- Blood culture (done 3x, at peak temp.)
- MRI / X-ray (normal for 1st 10 days) / USS (pus)
- Isotope bone scan / labelled white cell scan (both glow at site of infection)
How would you expect X-rays of a patients bone throughout the process of infection to look?
- No change within first 10 days
- Early changes: X-ray appears darker due to medullary lysis of the bone (destruction of cells)
- Further darkening due to destruction and sequestrum of bone
- Whitening of the bone due to involucrum (new bone formation)
What are some possible DDx for acute osteomyelitis?
- Acute septic arthritis
- Trauma (fracture / dislocation)
- Acute inflammatory arthritis
- Transient synovitis
- Soft tissue infection
List the different methods of microbiological diagnosis of acute osteomyelitis
- Blood cultures (not always positive in surgery / open fractures)
- Bone biopsy / aspiration
- Tissue swabs from around debridement in prosthetic infections
Treatment of acute osteomyelitis?
- Supportive (analgesia / fluids)
- Rest & splintage
- Antibiotics
- Surgery (biopsy / abscess drainage etc.)
Describe the antibiotic treatment given when acute osteomyelitis is diagnosed. Which antibiotics are used at first, before microbiology results are in?
- Start with IV antibiotics, switch to oral (usually at about 7-10 days)
- Antibiotic treatment usually lasts 4-6 weeks (depends on clinical response & ESR)
- Fluclox & Benzyl Pen usually used at first (bc usually either S Aureus or group B strep)
Why can antibiotics fail in treating osteomyelitis?
Resistance / poor penetration
- Bacteria can also hide in dead bone and lie dormant for years due to antibiotics not reaching these areas of un-perfused dead tissue
When is surgery needed to treat acute osteomyelitis?
- Biopsy
- Pus drainage (abscess drainage)
- Debridement of infected tissue
- Replacement of infected joints
What are some possible complications of acute osteomyelitis?
- Metastatic infection / septicaemia
- Septic arthritis
- Altered bone growth
- Pathological fracture
- Chronic osteomyelitis
What causes chronic osteomyelitis?
May follow acute osteomyelitis
De Novo: Surgery / open fracture / immunosuppressed
Repeated breakdown of “healed” wounds
Retained sequestra / involucrum / dead bone
What organism tends to cause chronic osteomyelitis?
Usually a mixed picture with multiple:
- S. Aureus
- E. Coli
- Strep. Pyogenes
- Proteus
Treatment of chronic osteomyelitis?
- Long term antibiotics
- Surgical eradication of infection
- Deformity correction / reconstruction / amputation
What are some possible complications of chronic osteomyelitis?
- Chronic sinus discharge & flare ups
- Metastatic infection
- Pathological fracture
- Growth disturbances +/- deformities
