LO: Compare and contrast the management of septic arthritis and crystal arthritis

Crystal arthritis

• Monosodium urate (uric acid): gout
• Calcium pyrophosphate: pseudogout

Pathogenic process

• Overproduction of uric acid (exo/endogenous)
• Underexcretion of uric acid
• Combination of both
• Most patients with hyperuricemia and primary gout (90%) are underexcretors of uric acid

Drugs causing hyperuricemia

• Cyclosporine
• Alcohol
• Nicotinic acid
• Thiazides
• Lasix (Frusemide)
• Ethambutol
• Aspirin (low dose)
• Pyrazinamide
  CANT LEAP

Epidemiology

• Common inflammatory arthritis in men over 40
• After menopause increase in women - loss of uricosuric effect of oestrogen
• Aging population
• Comorbidities

Predisposing factors

• Immediate postop period after major surgery
• Acute myocardial infarction
• Stroke
• Fasting
• Alcohol abuse
• Large intake of food with high purine content
• Local infection
• Kidney stones

Management

• Patient education
• Diet - low purine
  
• Reduce alcohol
• Weight reduction
• Colchicine prophylaxis for the first 3-6 months to reuce frequency of heart attacks
• Offer urate lowering therapy - lifelong treatment
• Chronic kidney disease stages 3 to 5
• Diuretic therapy
• Tophi
• Chronic gouty arthritis

Acute attack

• Joint rest and local ice
• NSAIDS/COX II
• Oral steroids
• Local steroid injection
• Oral colchicine

Intercritical gout

• Diet
• Alcohol
• Colchicine prophylaxis
• Urate lowering drugs
• 2 or more heart attacks in a year

Pseudogout

• Deposition of calcium pyrophosphate dihydrate (CPPD)
• Chondrocalcinosis - calcified cartilage on x-rays
• Presence of CPPD crystals associated with aggressive, destructive osteoarthritis

Conditions predisposing

• Age
• Hyperparathyroidism
• Hemachromatosis
• Hypomagnesemia
• Hypophosphatasia
• Acromegaly
• Hypothyroidism
• Trauma
• Infection
• Osteoarthritis

Acute pseudogout (a/c)

• 25%
• Elderly women > men
• Knee most involved
• Ankles, wrist and shoulders
• Attacks self limiting
• Surgical procedures

Chronic pseudogout (c/c)

• Pseudo osteoarthritis (OA) or pseudo rheumatoid arthritis (RA)
• Pseudo OA commonest form of c/c CPPD
• Primary OA pattern of involvement of wrist and metacarpophalangeal joint and atypical knee OA
• CPPD crystals associated with more severe OA
• Found in 60% of knee joints at time of replacement

Diagnosis

• History
• Clinical examination
• Joint fluid analysis
• X-ray

Osteoarthritis	Rheumatoid arthritis	Calcium pyrophosphate dihydrate
White - affected Black - not affected

LO: Discuss the differential diagnosis of presentations of a/c and c/c monoarthropathy

Aspiration of synovial fluid

• Joint fluid analysis
• White cell count in joint fluid neutrophils
• Culture to rule out infection
• Sodium uric acid
• Renal function
• Urine dipstick - haematuria

Radiography

• Well defined erosions
• Sclerotic borders
• Overhanging edges
• No osteoporosis
• Joint space: symmetric loss vs preservation
• Erosions: marginal vs eccentric with overhanging edge

Differential diagnosis

• Degree of inflammation - different from rheumatoid arthritis
• Matched by other crystal disease (pseudogout) or infection
• Podagra (1st metatarsophalangeal joint pain) characteristic of gout
• Degree of inflammation matched by gout and septic arthritis
• Gout - 1st metatarsophalangeal joint

Treatment

• Acute attack joint aspiration and steroid injection
• Anti-inflammatories
• Chronic pseudogout
• Periodic intraarticular steroid injection
• Associated disease managed

Allopurinol

• Most commonly used drug to lower uric acid
• Xanthine oxidase inhibitor
• Lower serum and uinary uric acid excretion

Gout flare

• Measure serum urate level
• Information about gout, self-management and reduce the risk of future flares
• Assess lifestyle and comorbidities
• Review medications and discuss the risks and benefits of long term urate-lowering therapy

Radiographic appearance

• Calcium deposition
• Triangular fibrocartilage
• Subchondral sclerosis
• Joint space narrowing
• Subchondral cyst formations