Osteonecrosis

Question 1

What is osteonecrosis?

Answer 1

Bone infarction near a joint

Question 2

When is the term ‘bone infarction’ used rather than osteonecrosis?

Answer 2

When the infarction occurs in a point in the bone which is not near the joint

Question 3

In which areas is osteonecrosis most common?

Answer 3

Hip and shoulder

Question 4

What is the main symptom which patient’s with osteonecrosis present with?

Answer 4

Pain

Question 5

Osteonecrosis can be assymptomatic. T/F?

Answer 5

True

Question 6

Describe a typical presenting complaint of a patient with osteonecrosis of the femoral head

Answer 6

Groin pain which worsens with weight-bearing and motion

Rest pain and night pain may also occur

Question 7

As osteonecrosis progresses patients will present with the findings of arthrosis. What are these findings?

Answer 7

Limp
Tenderness around the affected bone
Restricted motion

Question 8

What movements of the hip are particularly restricted due to osteonecrosis fo the femoral head?

Answer 8

Internal rotation

Abduction

Question 9

What. is the peak age of prevalence of osteonecrosis?

Answer 9

40-60 years

Question 10

Osteonecrosis is often bilateral. T/F?

Answer 10

True

Question 11

What haematological condition is commonly associated with osteonecrosis?

Answer 11

Sickle cell anaemia

Question 12

Which of the bone is affected first by osteonecrosis?

Answer 12

Medullary bone

Question 13

Why is the overlying cartilage spared in osteonecrosis?

Answer 13

This cartilage receives nutrition from the synovial fluid, so remains viable

Question 14

Describe how osteonecrosis can lead to the formation of insoluble calcium soaps

Answer 14

The dead bone has empty lacunae and is surrounded by necrotic adipocytes that often rupture and release fatty acids which can bind calcium to form insoluble calcium soaps

Question 15

The process of osteonecrosis can be caused by intravascular coagulation in the bone. What can cause this intravascular coagulation?

Answer 15

Arthus
Fat embolism
Shwartzman phenomenon

Question 16

Describe the process of creeping substitution in the healing process of bone in osteonecrosis?

Answer 16

Osteoclasts resorb necrotic trabeculae hole the remaining trabeculae serve as scaffolding for the deposition of new bone

Question 17

What is bone remodelling?

Answer 17

The process by which osteoclasts secrete acid and proteolytic enzymes to digest the bone matrix and osteoblasts synthesis new organic matrix leading to the deposition of newer, better bone

Question 18

Describe how a failure of bone healing in osteonecrosis can lead to the development of arthritis?

Answer 18

If bone does not remodel, micro damage does not get repaired and the mechanical properties of the bone are impaired. If enough damage accumulates, the sub-chondral bone can be weakened to the point of collapse. If the sub-chondral bone collapses, the joint surface becomes irregular. If one side fo the joint surface is not smooth then this will damage the other side.

Question 19

What are the findings of osteonecrosis which may be seen on plain radiograph?

Answer 19

Mild density changes following by sclerosis and cysts as the condition progresses

Question 20

What pathognomonic sign on x-ray can preceed subchodnral collapse in osteonecrosis?

Answer 20

Crescent sign (subchondral radiolucency)

Question 21

What are the risk factors for the development of osteonecrosis?

Answer 21

History of trauma, espc. joint dislocation
Corticosteroid use / cushing's
Alcohol abuse
Sickle cell disease / haemaglobinopathies
SLE
Antiphospholipid antibody syndrome
Metabolic diseases such as hyperlipidaemia
Renal failure
HIV
Prior radiation therapy
Chemotherapy
Decompression sickness
Bisphosphonates

Question 22

What are the treatment options for osteonecrosis?

Answer 22

Partial weight bearing
Bisphosphonates
Core decompression with or without bone graft
Total hip arthroplasty

Question 23

Reperfustion and healing of the infarcted area in osteonecrosis will restore the joint surface. T/F?

Answer 23

False