Infection of the bone and joint

Osteomyelitis

• Acute osteomyelitis usually occurs in children• Usually a haematogenous infection from distant focus• Organisms responsible include:– Staph. aureus– Strep. pyogenes– H. influenzae– Gram-negative organisms

• Salmonella infections are often seen in those with sickle-cell anaemia

• Infection usually occurs in metaphysis of long bones

Pathology• Acute inflammation results in raised intraosseous pressure

and intravascular thrombosis• Suppuration produces a subperiosteal abscess that may

discharge into soft tissues• Spread of infection into epiphysis can result in joint

infection• Within days bone death can occur• Fragments of dead bone become separated in medullary

canal (sequestrum)• New bone forms below stripped periosteum (involucrum)• If infection rapidly controlled resolution can occur• If infection poorly controlled chronic osteomyelitis can

develop

Presentation

• Child usually presents with pain, malaise and fever• Often unable to weight bear• Early signs of inflammation are often few• Bone is often exquisitely tender with reduced joint

movement• Late infection presents with soft-tissue swellings or

discharging sinus• Diagnosis can be confirmed by aspiration of pus from

abscess or metaphysis• 50% of patients have positive blood cultures

Radiology

• X-rays can be normal during first 3 to 5 days• In the second week radiological signs include:– Periosteal new bone formation– Patchy rarefaction of metaphysis– Metaphyseal bone destruction

• In cases of diagnostic doubt bone scanning can be helpful

Management• General supportive measures should include

intravenous fluids and analgesia• Painful limb often requires a splint of skin traction to

relieve symptoms• Aggressive antibiotic therapy should be instituted• Flucloxacillin is often the antibiotic of choice• If fails to respond to conservative treatment surgery

may be required• A subperiosteal abscess should be drained• Drilling of metaphysis is occasionally required• Overall, about 50% of children require surgery

Complications• Metastatic infection can occurs at distant sites (e.g.

brain, lung)• Spread into joint can result in a septic arthritis• This complication occurs in:– Young children in whom the growth plate is permeable– Bones in which the metaphysis is intracapsular– Epiphysis of bones involved in metastatic infection

• Involvement of physis can result in altered bone growth

• Failure to eradicate infection can result in chronic osteomyelitis

SEPTIC ARTHRITIS

Septic arthritis

• Acute inflammatory condition of a joint• Usually results from bacterial infection• Untreated it will lead to destruction of the articular

cartilage• 50% cases occur in children less than 3 years of age• In infants less than one year old the hip is the

commonest joint involved• In older children the knee is the commonest joint

affected• 10% of patients have multiple joints involved

Microbiology

Microbiology

• Organism can enter joint via a number of routes– Penetrating wound– From epiphysis or metaphysis– Haematogenous spread

• Provoke an acute inflammatory response• Large number of neutrophils accumulate in joint• Release proteolytic enzymes that break down the

articular cartilage• Results in joint effusion and reduced synovial blood

supply

Complications

• Avascular necrosis of epiphysis• Joint subluxation / dislocation• Growth disturbance• Secondary osteoarthritis• Persistent or recurrent infection

Clinical features

• Exact presentation depends on age• Children are usually systemically unwell• Present with pain in the affected joint• All movements of the joint are painful• Reluctant to stand on weight-bearing joints• Affected joint is usually swollen, red and warm• Hip involvement results in flexion and external rotation• In adults septic arthritis is usually associated with

immunosuppression

Ix

• Key investigation is culture of a joint aspirate• Should be performed prior to the

administration of antibiotics• Other appropriate investigations should

include– Inflammatory markers– Plain x-rays– Bone scan

DD

• Irritable hip• Perthe's disease• Osteomyelitis• Gout• Pseudogout

Mx

• Antibiotics should be started after joint aspiration

• Empirical therapy should be commenced based on likely organisms

• Adjusted depending antibiotic sensitivity• Antibiotics should be continued for 6 weeks

Sx

• Involves joint drainage and lavage• May be performed arthroscopically• Early joint mobilisation should be encouraged

POTT’S DISEASE

Pott’s disease

• Pott's disease is tuberculous spondylitis• Well recognised in Egyptian mummies• Described by Percival Pott in 1779• Now rare in western countries• Still prevalent in the developing world

Pathology

• Usually occurs secondary to infection elsewhere• Due to a combination of osteomyelitis and arthritis• Often occurs at more than one vertebral level• Usually affects anterior part of vertebral body• More common in thoracic spine• Bone destruction lead to vertebral collapse and

kyphosis• Spinal cord can be narrowed resulting in cord

compression and neurological deficit

Clinical presentation

• Back pain is the commonest symptom• Pain may be present for several months• Pain can be both spinal and radicular• 50% patients have neurological signs at

presentation• Most patients have some degree of kyphosis• Cold abscess may point in the groin

Ix• Serum ESR is usually massively raised• Tuberculin skin test is usually positive• Plain x-rays may show– Lytic destruction of anterior vertebral body– Anterior vertebral collapse– Reactive sclerosis– Enlarged psoas shadow

• CT or MRI provides information on disc space and neurological involvement

• As allows CT guided biopsy to obtain microbiological and pathological specimens

Tx• Treatment involves both tuberculous chemotherapy and possible surgery• Nine months of combination chemotherapy should be used• This involves 3 or 4 drugs• Isoniazid and rifampicin should be given for full nine months• Pyrazinamide, ethambutol or streptomycin should be give for first 2 months• Surgery is indicated if:

– Neurological deficit– Spinal deformity with instability– No response to medical treatment– Non-diagnostic percutaneous biopsy

• Surgical approach depends on extent of disease and level of spinal involvement

• Usually involves radical debridement and posterior stabilisation