Bone and Joint Infection Flashcards
What is the term for a bone infection?
Osteomyelitis
What is the term for a joint infection?
Septic arthritis
Epidemiology of acute osteomyelitis
- mostly children (different ages)
- boys > girls
- history of trauma (minor)
- other disease i.e. diabetes, rheum arthritis, immunocompromised, long term steroid treatment, sickle cell
Describe the source of infection in acute osteomyelitis
Haematogenous spread in children and elderly
Local spread from contiguous site of infection = trauma (open fracture), bone surgery, joint replacement
Secondary to vascular insufficiency
Infants; infected umbilical cord
Children; boils, tonsilitis, skin abrasions
Adults; UTI, arterial line
What are the most common organisms involved in acute osteomyelitis?
- infants < 1 year = S. Aureus, group B strep, E.Coli
- older children = S.Aureus, S.Pyogenes, H.Influenzae
- Adults = S.Aureus
What are less common organisms in acute osteomyelitis?
Diabetic foot and pressure sores = mixed infection including anaerobes
Sickle cell disease = salmonella spp
Mycobacterium marinum (fishermen, filleters)
Candida (debilitating illness, HIV/AIDS)
What is the pathology of acute osteomyelitis?
Starts at metaphysis
Vascular stasis; venous congestion and arterial thrombosis
Acute inflam - increased pressure
Suppuration
Release of pressure (medulla, sub-periosteal, into joint)
Necrosis of bone (sequestrum)
New bone formation (involucrum)
Resolution - or not (chronic)
Where does acute osteomyeltitis occur?
Long bones - metaphysis
- dital femur
- proximal tibia
- proximal humerus
Joints with intra-articular metaphysis
- hip
- elbow
What are the clinical features of acute osteomyelitis in an infant?
- may be minimal signs or may be v ill
- failure to thrive
- poss drowsy or irritable
- metaphyseal tenderness + swelling
- decrease ROM
- positional change
- commonest around knee
What are the clinical features of acute osteomyelitis in a child?
- severe pain
- reluctant to move, not weight bearing
- may be tender fever (swinging pyrexia) + tachycardia
- malaise
- toxaemia
What are the clinical features of acute osteomyelitis in an 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
- mixture of organisms
How is acute osteomyelitis diagnosed?
- history and clinical examination (pulse and temp)
- FBC + diff WBC (neutrophil leucocytosis)
- ESR and CRP
- blood cultures x3 (at peak temp 60% +ve)
- U&Es; ill, dehydrates
- xray, US, aspiration
- isotope bone scan
- labelled white cell scan
- MRI
What are differentials for acute osteomyelitis?
- acute septic arthritis
- acute inflammatory arthritis
- trauma (fracture, dislocation etc.)
- transient synovitis
- rarely sickle cell crisis, Gaucher’s disease, rheumatic fever, haemophilia
- soft tissue infection
Describe radiographs in acute osteomyelitis?
- early radiographs minimal change
- 10-20 days early periosteal changes
- medullary changes lytic areas
- late osteonecrosis (sequestrum)
- late periosteal new bone (involucrum)
What is the treatment for acute osteomyelitis?
Supportive treatment for pain and dehydration; general care and analgesia
Rest and splintage
Antibiotics;
- route (IV/oral switch 7-10days)
- duration (4-6wks depends on response, ESR)
- choice - empirical (fluclox + BenzylPen) while waiting
Surgery
When should you consider surgery in acute osteomyelitis?
- aspiration of pus for diagnosis and culture
- abscess drainage
- debridement of dead/infected/contaminated tissue
- infected joint replacements?
What are complications of acute osteomyelitis?
- septicaemia, death
- metastatic infection
- pathological fracture
- septic arthritis
- altered bone growth
- chronic osteomyelitis
Describe onset of chronic osteomyelitis
May follow acute
May start de novo
- following operation
- following open fracture (possibly many years earlier)
- immunosuppressed, diabetics, elderly, drug abusers etc.
Repeated breakdown of healed wounds
What organisms are involved in chronic osteomyelitis?
Often mixed
Usually same organisms each flare-up
Mostly S.Aureus, E.Coli, S.Pyogenes, proteus
What is the pathology of chronic osteomyelitis?
- cavities, poss sinus(es)
- dead bone (retained sequestra)
- involucrum
- histological picture is one of chronic inflammation
What are complications of chronic osteomyelitis?
- chronically discharging sinus + flare-ups
- ongoing (metastatic) infection (abscesses)
- pathological fracture
- growth disturbance + deformities
- squamous cell carcinoma
What is the treatment for chronic osteomyelitis?
- long term Abs; local or systemic
- eradicate bone infection; surgically (multiple ops)
- treat soft tissue problems
- deformity correction?
- massive reconstruction?
- amputation?
Describe the route of infection in acute septic arthritis
- haematogenous
- eruption of bone abscess
- direct invasion; penetrating wound, intra-articular injury, arthroscopy
What are the common organisms in acute septic arthritis?
- S.Aureus
- H.Influenzae
- S. 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
What are the consequences of acute septic arthritis?
Complete recovery
or
Partial loss of articular cartilage and subsequent OA
or
Fibrous or bony ankylosis
Describe the presentation of acute septic arthritis in a neonate
Picture of septicaemia
- irritability
- resistant to movement
- ill
Describe the presentation of acute septic arthritis in a child/adult
Acute pain in single large joint
- reluctant to move joint
- increase temp and pulse
- increase tenderness
- often superficial joint
- rare in healthy adult
- may be delayed diagnosis
Describe diagnosis of acute septic athritis
- FBC, WBC, ESR, CRP, bood cultures
- xray
- US
- aspiration
What is the most common cause of septic arthritis in adults?
Infected joint replacement
What is the most common organism in acute septic arthritis?
Staph
What are differential diagnoses 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 (3-4 weeks)
- surgical drainage and lavage (emergency); open or arthroscopic lavage
Describe clinical features of tuberculosis of one and joint
- insidious onset, general ill health
- contact with TB
- pain, swelling, weight loss
- low grade pyrexia
- joint swelling
- decrease ROM
- ankylosis
- deformity
Describe the pathology of tuberculosis of bone and joint
Primary in lung or gut
Secondary spread
Tuberculous granuloma
Describe spinal tuberculosis
Little pain
Present with abscess or kyphosis
Describe diagnosis of tuberculosis of bone and joint
- Long history
- Involve single joint
- Marked thickening of synovium
- Marked muscle wasting
- Periarticular osteoporosis
Describe investigation of tuberculosis of bone and joint
- FBC, ESR
- mantoux test
- sputum/urine culture
- xray; soft tissue swelling, periarticular osteopaenia, articular space narrowing
- joint aspiration and biopsy
What are some differential diagnoses for tuberculosis of bone and joint?
- transient synovitis
- monoarticular RA
- haemorrhagic arthritis
- pyogenic arthritis
- tumour
Treatment of tuberculosis of bone and joint
Chemo;
- initial 8 weeks rifampicin, isoniazid, ethambutol
- THEN 6-12 month rifampicin and isoniazid
Rest and splintage
Operative drainage rarely necessary
