Flashcards in Infection Deck (46)
Name 4 local factors that increase susceptibility to infection of bones and joints
Articular steroid injection
Large wound area and depth
Distal anatomical location
Chronic bone or joint disease
Name 4 systemic factors that increase susceptibility to infection of bones and joints
Age: children and elderly
Describe the features of acute pyogenic infection
Formation of pus often localised in an abscess
Abscess may extend infection along tissue directly, or spread via lymphatics (lymphangitis and lymphadenopathy) or blood (bacteraemia and septicaemia).
Systemic reaction due to enzymes and toxins.
Describe the features of chronic infection
May occur after acute infection
Less acute systemic effects, but may be more debilitating
Lymphadenopathy, splenomegaly, and tissue wasting
Outline the treatment principles of bone and joint infections
Analgesia and supportive measures
Rest the affected part
Drainage of pus and debridement of necrotic tissue
Stabilise bone if fractured
Maintain soft tissue and skin cover
What is typically the causative organism of acute osteomyelitis?
Less often: Strep pyogenes, Strep pneumoniae, or H. influenzae (children)
If sickle-cell: Salmonella typhi
Which patient group is most affected by acute osteomyelitis?
Children over age of 4 years
What is the most common location of acute osteomyelitis in children?
Metaphysis of long bones
Most often at the proximal or distal end of the femur, or the proximal end of the tibia
N.B. in infants, acute osteomyelitis can also reach the epiphysis due to presence of anastomoses.
Describe the pathological changes of acute osteomyelitis
1. Acute inflammation: intense pain, obstructed blood flow
2. Suppuration: subperiosteal abscess formation
-may spread along shaft and re-enter bone, or spread to soft tissues
-infants: may spread to epiphysis and joint
3. Necrosis: usually seen by 1 week
-stasis, periosteal stripping, thrombosis
-bone fragments can act as foreign bodies
4. New bone formation: involucrum encases infection
-if infection persists ➔ chronic osteomyelitis
-requires infection to be controlled and intraosseous pressure to be release at an early stage
-may result in overall thickening of bone
Describe the clinical features of acute osteomyelitis in children
Severe pain: limb held still
Systemic: fever, malaise, irritability, lethargy
Tenderness over involved bone
Decreased range of motion in adjacent joints
Later: red, swollen, warm ➔ pus formation (suppuration)
Describe the clinical features of acute osteomyelitis in infants and neonates
Infants and neonates may present with misleadingly mild symptoms: failure to thrive, drowsy, irritable
May have metaphyseal tenderness and resistance to joint movements
Always look at other sites, as multi infection is not uncommon.
Name 2 aspects of the history that would increase suspicion of acute osteomyelitis in neonates
Umbilical artery catheterisation
Name and explain 2 consequences of acute osteomyelitis in infants within 1st year of life
Growth retardation and deformity
Metaphysis-epiphysis anastomoses present in 1st year of life, allow haematogenous spread to epiphysis.
Where is the commonest location of acute osteomyelitis in adults? What clinical features would suggest this?
Suspicious features: back pain and a mild fever
How is acute osteomyelitis confirmed?
Fine needle aspiration and culture
How is acute osteomyelitis investigated?
Aspirate pus from subperiosteal abscess or joint*
Culture for cells and organisms
Raised WBC and ESR
MRI*: 90-100% sensitivity
X-ray: normal for first 2 weeks
Explain the treatment of acute osteomyelitis
Blood and aspirate samples sent for culture
Supportive: bed rest, splint, analgesia
Prompt antibiotics if pus found on aspiration
Empirical antibiotics: Flucloxacillin or clindamycin
Continue antibiotics for 4-6 weeks
Children should initially receive 2 weeks of IV antibiotics
Outpatient follow-up*: crucial to check for recurrence
State 3 complications of acute osteomyelitis
Spread: septic arthritic or metastatic osteomyelitis
Growth disturbance/deformity if epiphysis involved
Persistent infection ➔ chronic osteomyelitis
Describe the clinical features of subacute osteomyelitis
Common in distal femur, and proximal and distal tibia
Pain near one of larger joints for several weeks
What classic radiographic sign is indicative of subacute osteomyelitis?
Brodie abscess: small oval cavity surrounded by sclerotic bone
Most be explored as can be mistaken for osteoid osteoma or bone tumour if large
What is the commonest causative organism of post-traumatic osteomyelitis?
Others: E. coli, Proteus mirabilis, Pseudomonas aeruginosa
Describe the clinical features of post-traumatic osteomyelitis
Pain and swelling over fracture site
May have purulent discharge
What are the common causes of chronic osteomyelitis?
Following open fracture or operation
Less common nowadays after acute osteomyelitis
Name 2 typically causative organisms of chronic osteomyelitis
Proteus mirabilis: soil
Strep epidermidis: surgical implants
Describe the clinical features of chronic osteomyelitis
Recurrent pain, redness, and tenderness at affected site
Healed and discharging sinus
What x-ray features are seen with chronic osteomyelitis?
Bone rarefaction (thinning) surrounded by dense sclerosis and cortical thickening
Outline the treatment options for chronic osteomyelitis
If seldom relapses: conservative management
-Rest, dressing, and antibiotics for 4-6 weeks
Drainage of any acute abscess
Refractory or frequent relapses: surgery
-excision of infected/devitalised bone
-Ilizarov method after bone transport ➔ bone union
What is the usual causative organism of septic arthritis?
Children aged 1-4: H. influenzae if not vaccinated
Explain the pathology of septic arthritis
Joint invaded by:
-a penetrating wound
-eruption of adjacent bone abscess
-distal haematogenous spread