Rheumatology Flashcards
What is Osteomyelitis?
Infection and inflammation of the bone.
Aetiology/Risk Factors for Osteomyelitis
Immunodeficiency (immunosuoppressants, HIV, etc)
DM - diabetic foot ulcers
Inflammatory arthritis e.g rheumatoid arthritis
Trauma
Sickle cell anaemia
Intravenous drug usage
Bacterial Aetiology of Osteomyelitsi
Staphylococcus aureus - most common
S.epidermidis - prosthetic joints
Salmonella - sickle cell disease
H.influenzae
P.aeruginosa - IVDU
What are the methods in which a bone can become infected?
Direct Inoculation - trauma, open wound
Contiguous Spread - infection of adjacent joint/tissue
Haematogenous Seeding - IVDU, catheter
Pathophysiology of Osteomyelitis
Inflammation due to infection causes inflammatory exudate in bone marow.
Results in increased intramedullary pressure - oedema.
Exudate can then go into the bone cortex and rupture periosteum.
Can interrupt perfusion and cause necrosis.
Leaves separated pieces of dead bone called sequestra.
New bone formation known as involucrum.
What is the most common site affected in children from haematogenous seeding osteomyelitis?
Metaphysis of long bones
Because blood flow is slower
Lack of endothelial basement membrane
Capillaries lack phagocytic lining cells.
What is the most common site affected in adutls from haematogenous seeding osteomyelitis?
Spinal vertebrae
Vertebrae get more vascular with age, allowing for increased likelihood of bacterial endplate seeding.
Acute pathophysiological changes seen in osteomyelitis
Oedema
Bone inflammation
Vascular congestion
Small vessel thrombi
Chronic pathophysiological changes seen in osteomyelitis
Necrotic bone ‘sequestra’
New bone formation - ‘involucrum
Lymphocytes and histiocytes
Exudate
Clinical Presentation of Acute Osteomyelitis
Onset over several days.
Dull pain at site which may be aggravated by movement.
Inflamed, swollen, tender at site of infection.
Clinical Presentation of Chronic Osteomyelitis
Deep / large ulcers that fail to heal despite several weeks treatment*
Non-healing fractures
Investigation of Osteomyelitis
FBC - leukocytosis
Raised CRP
First line: X-ray - can show osteopaenia - changes can be seen within 2 weeks of infection.
MRI scan - marrow oedema
GS: Blood cultures and bone biopsy
Differential Diagnoses of Osteomyelitis
Charcot joint - damage to sensory nerves due to diabetic neuropathy.
Cellulitis
Avascular necrosis of bone
Gout
Fracture
Medical Management of Osteomyelitis
Empirically vancomycin + ceftriaxone
Once organism is identified,
6 weeks IV antibiotics is considered minimum.
Stopping treatment is guided by CRP monitoring.
Surgical Management of Osteomyelitis
Debridement
Aetiolgy of Septic Arthritis in Adults
S.aureus
Streptococcus spp.
Neisseria gonorrhoeae
P.aeruginosa
Mycobacteria
Fungi
Aetiology of Septic Arthritis in children
S.aureus
H.influenzae
Kingella kingae
Risk Factors for Septic Arthritis
Immunosuppression (including steroids only)
Old age
Rheumatoid arthritis (or other immune-driven disease)
Diabetes mellitus
Prosthetic joint
Clinical Presentation of Septic Arthritis
Painful, red, swollen, hot joint
Mainly monoarthritis - single joint affected.
In children - may present as hesitation to use the joint.
Fever
Knee > hip > shoulder
Clincal Presentation of Gonococcal Septic Arthritis
Polyarthritis
Maculopapular – pustular rash
Investigation of Septic Arthritis
FBC: Leukocytosis
Raised CRP
Joint aspiration + culture - diagnostic
Infected joint fluid is turgid, viscous.
Blood cultures - mostly caused by bacteraemia seeding.
Management of Septic Arthritis
6 weeks minimum antibiotics
S.aureus - IV flucloxacillin
Gonococcal - IV ceftriaxone + azithromycin
Analgesia
Joint aspiration until no recurrent effusion.
What must be done for patients on corticosteroids with septic arthritis?
Temporary stoppage of short term immunosuppression.
If on long term steroids, prednisolone dose needs to be doubled in order to maintain glucocorticoid levels.
Investigation of Prosthetic Joint Infection
Serology: Alpha defensin positive - antimicrobial peptide found in synovial fluid.
Joint aspiration is diagnostic.