Infection in Bone 2: Septic Arthritis and Tuberculosis Flashcards
What are the most common routes of infection for acute septic arthritis?
- Haematogenous
- Eruption of bone abscesses
- Direct invasion (penetrating wounds / surgery etc.)
When there is a metaphyseal abscess rupture, where can the pus spread to?
Sub - periosteal: osteomyelitis
Joint cavity - septic arthritis
What are the most common causative organisms for septic arthritis?
- Staph Aureus
- Haemophilus influenzae
- Streptococcus pyogenes
- E. Coli
Describe the progression of a septic arthritis infection
- Acute synovitis with purulent joint effusion
- Articular cartilage attacked by bacterial toxin and cellular enzymes
- Complete destruction of articular cartilage if untreated for significant time
Possible outcomes of septic arthritis infection?
- Complete recovery
- Partial loss of articular cartilage and subsequent osteoarthritis
- Fibrous or bony ankylosis (stiffening / immobility of
the joint)
How does septic arthritis tend to present in infants?
Picture of septicaemia:
- Irritability
- Bone resistant to movement
- ill
Often multifocal infection with other sites of infection present (CNS etc.)
How does septic arthritis tend to present in adults?
- Reluctant to move joint (often can’t really move it at all, very severe pain)
- Joint swelling (in superficial joints like knee / wrists, not really seen in shoulder / hip etc.)
- Increased temperature and pulse
- Increased tenderness
Is erythema seen in septic arthritis?
No, not early on in large joint infections
- May be there in superficial joints or late on in infection, but not a common early sign
What joints are mostly affected by septic arthritis?
Superficial joints
- Knee
- Wrists
- Ankle
What investigations are done in suspected septic arthritis?
- FBC / WBC / ESR / CRP
- Xray / USS / MRI
- Aspiration of the joint
What are the most common causative organisms for septic arthritis due to joint replacement?
- Staph epidermis
- Staph aureus
Treatment of septic arthritis?
- Supportive (analgesia / fluids)
- Antibiotics (3-4 weeks)
- Surgical drainage and lavage (washing out) of joint
- Infected joint replacements
How are tuberculosis infections of bone and joints classified by location?
Extra-articular (epiphyseal, bones w haemodynamic marrow)
Intra-articular (large joints)
Vertebral body (most common)
- There are multiple lesions in 1/3 of patients though
How does tuberculosis infection of bone tend to present?
Insidious onset & general ill health
- Pain, swelling, weight loss, low grade pyrexia
- Joint swelling, decreased ROM
- Ankylosis & deformity (late stage)
What is ankylosis of a joint?
abnormal stiffening and immobility of a joint due to fusion of the bones
What is an important thing to look for when bone infection with TB is suspected?
Primary site of infection (Lungs / gut)
- Tuberculous granuloma
- Also need to consider role of malnutrition / HIV etc. in precipitating infection
How does spinal tuberculosis tend to present?
Often little pain
- Have either a cold abscess or kyphosis of spine
Kyphosis: outward curve
What are some characteristics of bone infection with tiberculosis?
- Involvement of single joint only
- Marked thickening of synovium
- Marked muscle wasting
- Periarticular osteoporosis
Investigations for suspected TB infection of bone?
FBC / ESR / Sputum & urine culture
Mantoux test
XRay / MRI
Joint aspiration and biopsy
Treatment of bone infection with TB?
Chemotherapy:
- 8 Weeks: rifampicin / isoniazid / ethambutol
Rest and splintage
Operative drainage / bone fusion (rare)
