Orthopaedics

Question 1

Define avascular necrosis

Answer 1

Avascular necrosis (AVN) may be defined as death of bone tissue secondary to loss of the blood supply. This leads to bone destruction and loss of joint function. It most commonly affects the epiphysis of long bones such as the femur.

Question 2

What are the causes/risk factors of avescular necrosis?

Answer 2

Causes

• Long-term steroid use
• Chemotherapy
• Alcohol excess
• Trauma
  
  • Intracapsular neck of femur fractures
  • Scaphoid fractures

Question 3

Describe the investigations and management of avascular necrosis

Answer 3

Investigation

Plain x-ray findings may be normal initially. Osteopenia and microfractures may be seen early on. Collapse of the articular surface may result in the crescent sign.

MRI is the investigation of choice. It is more sensitive than radionuclide bone scanning.

Management

Joint replacement may be necessary

Question 4

What is the definition of compartment syndrome, and what are the common causes?

Answer 4

Compartment syndrome is a particular complication that may occur following fractures (or following ischaemia reperfusion injury in vascular patients). It is characterised by raised pressure within a closed anatomical space. The raised pressure within the compartment will eventually compromise tissue perfusion resulting in necrosis. The two main fractures carrying this complication include:

• Supracondylar fractures (injury to the humerus, or upper arm bone, at its narrowest point, just above the elbow)
• Tibial shaft injuries

Question 5

What are the clinical features of compartment syndrome?

Answer 5

• Pain, especially on movement (even passive)
• Paraesthesia
• Pallor may be present
• Arterial pulsation may still be felt as the necrosis occurs as a result of microvascular compromise
• Paralysis of the muscle group may occur

The presence of a pulse does not rule out compartment syndrome.

Question 6

What are the investigations for compartment syndrome?

Answer 6

Diagnosis is made by measurement of intracompartmental pressure measurements. Pressures in excess of 20mmHg are abnormal and >40mmHg is diagnostic

Compartment syndrome will typically not show any pathology on an x-ray

Question 7

Describe the management of compartment syndrome

Answer 7

This is essentially prompt and extensive fasciotomies.

• Myoglobinuria may occur following fasciotomy and result in renal failure and for this reason these patients require aggressive IV fluids.
• Where muscle groups are frankly necrotic at fasciotomy they should be debrided and amputation may have to be considered.

Death of muscle groups may occur within 4-6 hours.