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Avascular Necrosis of Bone           

Title               

Ñ    Avascular Necrosis of Bone

Definition

Ñ    Focal infarction of bone

Pathogenesis

Causes

Definite          

LMS

Ñ    Fracture of the femoral neck

Ñ    Hip dislocation

HS

Ñ    Sickle cell disease

RS

Ñ    Decompression sickness

E&M

Ñ    Gaucher’s disease

Physical agents

Ñ    Radiotherapy

Drugs

Ñ    Corticosteroids

Ñ    Heparin

Possible

LMS

Ñ    Systemic lupus erythematosus

Ñ    Gout

IS

Ñ    Psoriasis

HS

Ñ    Polycythaemia rubra vera

E&M

Ñ    Cushing’s syndrome

Ñ    Diabetes mellitus

GIT

Ñ    Pancreatitis

Ñ    Pancreatic cancer

Ñ    Fatty liver

KUS

Ñ    Renal transplant

CVS

Ñ    Atherosclerosis

Drugs

Ñ    Cytotoxic chemotherapy

Toxins

Ñ    Alcohol abuse

Pathological Process

Ñ    Occlusion of blood supply to the bone

Ñ    Necrosis of bone

Ñ    Repair process triggered:

Vascular elements, osteoclasts, osteoblasts, histiocytes involved

Ñ    Osteoblasts build new bone on top of dead bone

Ñ    This produces a thick scar which prevents revascularisation of necrotic bone

Ñ    This causes abnormal joint remodelling and joint dysfunction

Sites

Usually affects sites with a single terminal blood supply:

Ñ    Hip

Ñ    Knee

Ñ    Shoulder

Ñ    Talus

Ñ    Scaphoid

Ñ    Navicular

Clinical Features

History

May be:

Ñ    Asymptomatic

Ñ    Sudden onset

Ñ    Insidious onset

LMS

Ñ    Pain

Ñ    Decreased range of movement

Ñ    Effusion

Investigations

Imaging

X-ray

Ñ    Changes are diagnostic after a few weeks:

Well-demarcated area of increased bone density

CT scan

Ñ    Used to rule out advanced disease

MRI

Ñ    Sensitive, specific and may be used for very early diagnosis

Nuclear Medicine

Bone scan

Ñ    More sensitive than x-ray but less specific

Management

Symptom relief

Drugs

Ñ    Analgesics

Support

Surgery

Ñ    Bone graft

Ñ    Core decompression:

Drill out the centre of the bone to relieve intraosseous pressure

Ñ    Osteotomy:

Alters mechanics of the joint

Ñ    Joint replacement

Staffing

Ñ    Physiotherapy

Prevention

Drugs

Ñ    Minimise steroid dose

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