Bone and Soft Tissue Infection Flashcards
What is osteomyelitis?
Infection of the bone
What are the different types of osteomyelitis?
- Acute or chronic
- Specific or non-specific (most common)
Is specific or non-specific osteomyelitis more common?
Non-specific
What age group and sex does acute osteomyelitis mostly affect?
- Mostly children
- Boys > girls
What are risk factors for acute osteomyelitis?
- History of trauma (minor)
- Other disease
- diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell
What are sources of infection for acute osteomyelitis?
- Haematogenous spread
- Children and elderly
- Local spread from contiguous site of infection
- Such as trauma (open fracture), bone surgery or joint replacement
- Secondary to vascular insufficiency
What is a common source of infection for acute osteomyelitis in: infants, children, adults?
- In infants
- Infected umbilical cord
- In children
- Boils, tonsillitis, skin abrasions
- In adults
- UTI, arterial line
What are the most common infecting organisms for acute osteomyelitis for: infants (<1 year), older children and adults?
- Infants (<1 year)
- Staph aureus, Group B streptococci, E. coli
- Older children
- Staph aureus, Strep pyogenes, Haemophilus influenzae
- Adults
- Staph aureus
- coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)
Describe the pathology of acute osteomyelitis?
- Starts at metaphysis
- Typically distal femur, proximal tibia, proximal humerus or for joints with intra-articular metaphysis the hip or elbow
- Vascular stasis
- Venous congestion and arterial thrombosis
- Acute inflammation causing increased pressure
- Release of pressure
- Necrosis of bone (sequestrum)
- New bone formation (involucrum)
- Resolution or not (maybe become chronic osteomyelitis)
Where does acute osteomyelitis typically start?
- Starts at metaphysis
- Typically distal femur, proximal tibia, proximal humerus or for joints with intra-articular metaphysis the hip or elbow
Describe some of the clinical features of acute osteomyelitis in: infants, children, adults?
- Infants
- may be minimal signs, or may be very ill
- failure to thrive
- poss. drowsy or irritable
- metaphyseal tenderness + swelling
- decrease ROM
- positional change
- commonest around the knee
- Child
- severe pain
- reluctant to move (neighbouring joints held flexed); not weight bearing
- may be tender fever (swinging pyrexia) + tachycardia
- malaise (fatigue, nausea, vomiting – “**nae weel” - fretful
- toxaemia
- Adult
- Primary OM seen commonly in thoracolumbar spine
- backache
- history of UTI or urological procedure
- elderly, diabetic, immunocompromised
- Secondary OM much more common
- often after open fracture, surgery (esp. ORIF)
- mixture of organisms
How is acute osteomyelitis diagnosed?
- history and clinical examination (pulse + temp.)
- Bloods
- FBC + diff WBC (neutrophil leucocytosis)
- ESR, CRP
- blood cultures x3 (at peak of temperature – 60% +ve)
- U&Es – ill, dehydrated
- Imaging
- X-ray (normal in the first 10-14 days)
- ultrasound
- aspiration
- Isotope Bone Scan (Tc-99, Gallium-67)
- labelled white cell scan (Indium-111)
- MRI
- Microbiological diagnosis
- blood cultures in haematogenous osteomyelitis and septic arthritis
- bone biopsy
- tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
- sinus tract and superficial swab results may be misleading (skin contaminants)
What bloods can be done for acute osteomyelitis?
- FBC + diff WBC (neutrophil leucocytosis)
- ESR, CRP
- blood cultures x3 (at peak of temperature – 60% +ve)
- U&Es – ill, dehydrated
What imaging can be done for acute osteomyelitis?
- X-ray (normal in the first 10-14 days)
- ultrasound
- aspiration
- Isotope Bone Scan (Tc-99, Gallium-67)
- labelled white cell scan (Indium-111)
- MRI
What microbiological diagnosis can be done for acute osteomyelitis?
- blood cultures in haematogenous osteomyelitis and septic arthritis
- bone biopsy
- tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
- sinus tract and superficial swab results may be misleading (skin contaminants)
Describe the differential diagnosis for acute osteomyelitis?
- acute septic arthritis
- acute inflammatory arthritis
- trauma (fracture, dislocation, etc.)
- transient synovitis (“**irritable hip”)
- rare
- sickle cell crisis
- Gaucher’s disease
- rheumatic fever
- haemophilia
- Soft tissue infection
- cellulitis - (deep) infection of subcutaneous tissues (Gp A Strep)
- erysipelas - superficial infection with red, raised plaque (Gp A Strep)
- necrotising fasciitis - aggressive fascial infection (Gp A Strep, Clostridia)
- gas gangrene - grossly contaminated trauma (Clostridium perfringens)
- toxic shock syndrome - secondary wound colonisation (Staph aureus)
What are some soft tissue infections included in the differential diagnosis for acute osteomyelitis?
- cellulitis - (deep) infection of subcutaneous tissues (Gp A Strep)
- erysipelas - superficial infection with red, raised plaque (Gp A Strep)
- necrotising fasciitis - aggressive fascial infection (Gp A Strep, Clostridia)
- gas gangrene - grossly contaminated trauma (Clostridium perfringens)
- toxic shock syndrome - secondary wound colonisation (Staph aureus)
What is the treatment for acute osteomyelitis?
- Supportive for pain and dehydration
- General care such as analgesia
- Rest and splintage
- Antibiotics
- Empirical (fluclox and benzylpen)
- Choose based on spectrum, penetration of bone and safety for long term administration
- Failure can occur due to
- drug resistance – e.g. b lactamases
- bacterial persistence - ‘dormant’ bacteria in dead bone
- poor host defences - IDDM, alcoholism…
- poor drug absorption
- drug inactivation by host flora
- poor tissue penetration
- Surgery
- Indications
- aspiration of pus for diagnosis & culture
- abscess drainage (multiple drill-holes, primary closure to avoid sinus)
- debridement of dead/infected /contaminated tissue
- refractory to non-operative Rx >24..48 hrs
- Timing, drainage, lavage
- Infected joint replacements
- Indications
What are indications for surgery for acute osteomyelitis?
- aspiration of pus for diagnosis & culture
- abscess drainage (multiple drill-holes, primary closure to avoid sinus)
- debridement of dead/infected /contaminated tissue
- refractory to non-operative Rx >24..48 hrs
What are some potential complications of acute osteomyelitis?
- septicemia, death
- metastatic infection
- pathological fracture
- septic arthritis
- altered bone growth
- chronic osteomyelitis
What can chronic osteomyelitis occur after?
Can follow acute osteomyelitis or occur de novo:
- Following operation
- Risk factors
- immunosuppressed, diabetics, elderly, drug abusers, etc.
What are some risk factors for chronic osteomyelitis?
- immunosuppressed, diabetics, elderly, drug abusers, etc.
What organisms are usually responsible for chronic osteomyelitis?
- Often mixed
- Usually same organism each flare up
- Mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus
Describe the pathology of chronic osteomyelitis?
- cavities, poss. sinus(es)
- dead bone (retained sequestra)
- involucrum
- histological picture is one of chronic inflammation
What are potential complications of chronic osteomyelitis?
- chronically discharging sinus + flare-ups
- ongoing (metastatic) infection (abscesses)
- pathological fracture
- growth disturbance + deformities
- squamous cell carcinoma (0.07%)
What is the treatment for chronic osteomyelitis?
- Long term antibiotics
- Local
- Systemic
- Eradicate bone infection surgically
- Treat soft tissue problems
- Deformity correction
- Massive reconstruction
- Amputation
What are the different route of infection for acute septic arthritis?
- haematogenous
- eruption of bone abscess
- direct invasion
- penetrating wound (iatrogenic? – joint injection)
- intra-articular injury
- arthroscopy
Infection A is?
Septic arthritis
Infection B is?
Osteomyelitis
What organisms are typically responsible for acute septic arthritis?
- Staphylococus aureus
- Haemophilus influenzae
- Streptococcus pyogenes
- E. coli
Describe the pathology of acute septic arthritis?
- Acute synovitis with purulent joint effusion
- Articular cartilage attacked by bacterial toxin and cellular enzyme
- Complete destruction of articular cartilage
- Finally complete recovery or partial loss of articular cartilage or fibrous or bony ankyloses
What are the clinical features of acute septic arthritis in: neonate, child/adult, adult?
- Neonate
- irritability
- resistant to movement
- ill
- Child/adult
- Acute pain in single large joint
- reluctant to move the joint (any movement – c.f. bursitis where RoM OK)
- increase temp. and pulse
- increase tenderness
- Adult
- often involves superficial joint (knee, ankle, wrist)
- rare in healthy adult
- May be delayed diagnosis
- Infected joint replacement (most common cause)
What investigations should be done for acute septic arthritis?
- FBC, WBC, ESR, CRP, blood cultures
- X ray
- ultrasound
- aspiration
What is the differential diagnosis for acute septic arthritis?
- acute osteomyelitis
- trauma
- irritable joint
- haemophilia
- rheumatic fever
- gout
- Gaucher’s disease
What is the treatment for acute septic arthritis?
- General supportive measures
- Antibiotics
- Surgical drainage and lavage
What are the different classifications of TB in bones and joints?
- extra-articular (epiphyseal / bones with haemodynamic marrow)
- intra-articular (large joints)
- vertebral body
What are clinical features of TB in bones and joints?
- insidious onset & general ill health
- contact with TB
- pain (esp. at night), swelling, loss of weight
- low grade pyrexia
- joint swelling
- decrease ROM
- ankylosis
- deformity
When does the pain due to TB in bone and joints occur usually?
Especially at night
Describe the pathology of TB in bones and joints?
- primary complex (in the lung or the gut)
- secondary spread
- tuberculous granuloma
How does TB often present in the spine?
Can occur in the spine where it causes little pain but presents with abscess or kyphosis
What does the diagnosis of TB in bones and joints involve?
- long history
- involvement of single joint
- marked thickening of the synovium
- marked muscle wasting
- periarticular osteoporosis
What investigations should be done for TB in bones and joints?
- FBC , ESR
- Mantoux test
- Sputum/ urine culture
- Xray soft tissue swelling
- periarticular osteopaenia
- articular space narrowing
- Joint aspiration and biopsy
- AAFB identified in 10-20%
- culture +ve in 50% of cases
What is the differential diagnosis for TB in bones and joints?
- transient synovitis
- monoarticular RA
- haemorrhagic arthritis
- pyogenic arthritis
- Tumour
What is the treatment for TB in bones and joints?
- Chemotherapy
- Initial: rifampicin, isoniazid and ethambutol (8 weeks)
- Then: rifampicin and isoniazid (6- 12months)
- Rest and splintage
- Operative drainage if necessary
What is the medical treatment for TB in bones and joints?
- Initial: rifampicin, isoniazid and ethambutol (8 weeks)
- Then: rifampicin and isoniazid (6- 12months)
