Paediatric Septic Arthritis

Contents

• Introduction

• Pathophysiology

• Microbiology

• Diagnosis

• History

• PE

• Investigations

• Treatment Options

What is it?

• An infection of the joint space

• Monoarticular-90%, Polyarticular, Suppurative and non-suppurative

Routes of Infection

1. Hematogenous

• Most common

• Bacteremia associated with URTI, Skin or GIT infections. Or invasive procedures.

2. Direct Inoculation

• Joint contamination by foreign object

3. Contiguous spread

• Osteomyelitis due to several factors in infants

Pathogenesis: Acute septic arthritis

Bacteria deposits in synovium producing inflamation

↓

Spreads to synovial fluid and multiplies

↓

Products of inflamation destroys joint components

(Swollen, painful joint)

↓

Sequlae

Infant

Destroy the epiphysis, which is still largely

cartilaginous.

Children

Vascular occlusion lead to necrosis of

epiphyseal bone

a) In the early stage, there is an acute synovitis with a purulent joint effusion

b) Soon the articular cartilage is attacked by bacterial and cellular enzyme.

c) If infection is not arrested , the cartilage may be completely destroyed

d) Sequlae include necrosis, sublaxation, dislocation and ankylosis.

Healing

May occur with/and/or

1.Complete resolution

2.Partial loss of articular cartilage and fibrosis of joint

3.Loss of articular cartilage and bony ankylosis

4.Bony destruction and permanent deformity

What causes it?

• Mostly bactireal. Also caused by mycobacteria, virus and fungi. (HiB vaccination status dependent)

• Gram positive 70-80% of which 40% is S. aureus

• Gram negative 9-20%

• Kingella kingae, N. gonorrhoeae

Clinical FeaturesInfants

• More septicaemia• Rather than joint pain

• Baby is irritable & refuses to feed

• Tachycardia with fever

• Joints are inflamed• Pseudoparalysis

• Check umbilical cord and IV site for infection

Children

• Acute pain in single large joint(esphip)

• Pseudoparesis

• Child is ill, rapid pulse and swinging fever

• Overlying skin looks red & superficial joint swelling may be obvious

• Local warmth and marked tenderness

• All movements are restricted by pain or spasm.

• Look for source of infection

Position of minimal intrasynovial pressure

Joint Degrees of flexion

Wrist 0

Elbow 40

Shoulder 0 40 abduction; 0 rotation

Hip 40 15 abduction; 15 external rotation

Knee 40

Ankle 15

History

1. Progression

• Worsens over time, does not wax or wane, and may awaken patient at night.

2. Joint trauma

• Falls, bites, cuts.

3. Skin lesions

4. Recurrent or concurrent illness

5. Recent onset of menses

6. MCH card (Immunization status)

7. Family history of rheumatologic disease

Physical Exam

• Lower limb antalgic limp / cannot walk• Upper limb affected part is closely guarded• Marked tenderness, active and passive range of

motion are limited• Examine for synovial effusion, erythema, heat and

tenderness.• Spasm of muscles around the joint may be

marked.• Patient may hold the joint in a position to reduce

the intra-articular pressure to minimize pain.

Investigations Explaination

Full blood count Elevated white blood cell count

ESR > 40 mm/hr

CRP > 20 mg/dL

Blood culture May be positive

Ultrasound

Xray

Synovial Fluid

Investigations

Bloods Imaging SynovialFluid

Imaging2. Xray: Frog-leg position for hip.

• Early Stage – Normal

• Look for soft tissue swelling, loss of tissue planes, widening of joint space and slight subluxation due to fluid in joint. Gas may be seen with E. coli infection

• Late stage – Narrowing and irregularity of joint space, erosion of epiphysis or metaphysis

• Plain film findings of superimposed osteomyelitis may develop (periosteal reaction, bone destruction, sequestrum formation).

1. USS

• More reliable in revealing a joint effusion in early cases.

• Widening of space between capsule and bone of > 2mm indicates effusion.

• Echo-free

transient synovitis

• Positively echogenic

septic arthritis

Narrowing of joint space and irregularity of subchondral bone.

Joint space losssubchondral erosions and

sclerosis of the femoral head

osteonecrosis and complete collapse of

the femoral head

Synovial Fluid AnalysisArthritis Type Appearance Viscosity White

cells/mm3

Crystals Biochemistry Culture

Normal Clear yellow High Few - As per plasma -

Septic arthritis

Purulent Low >>50,000 - Glucose low +

Tuberculous arthritis

Turbid Low <2000 - Glucose low +

Rheumatoid arthritis

Cloudy Low >2000 - - -

Gout Cloudy Normal >2000 UrateNBF

- -

Pseudogout Cloudy Normal >2000 Pyrophosphate PBF

- -

Osteoarthritis Clear yellow High <2000 Often + - -

DifferentialsInfectious Causes of arthritis in children

DifferentialsNon- Infectious Causes of arthritis in children

Management

• Medical

• General supportive (Fever, pain, hydration)

• Antibiotics: IV Antibiotics 6-8 weeks

• Cloxacillin, Flucloxicillin, gentamycin and rifampicin for mycobacterium and ceftriaxone for gonorrhoea

• Surgical

• Percutaneous arthrocentesis

• Arthroscopic of open surgical drainage

• Rehabilitation

• Physiotherapy: Rapid mobilizaton

Parenteral antibiotics

Take Home Points

• Prompt diagnosis and treatment is crucial to preventing bad bad sequlae. Esp. if the hip is involved

• Treatment goals are sterillisation and decompression of joint space and removal of debris

• Follow-up must be scheduled to ensure a growing child won’t be affected the rest of her/his life.

Veenaka