Hip Arthritis and Trauma

Question 1

Describe the pathophysiology of osteoarthritis

Answer 1

• Chronic degenerative joint disease leading to functional limitation and reduced quality of life
  
  • Most common in hands, knees and hip joints
• Wear and tear of articular hyaline cartilage leads to bone-to-bone contact, soreness and swelling
• No systemic involvement and non-inflammatory

Question 2

Differentiate between primary and secondary osteoarthritis

Answer 2

• Primary osteoarthritis - etiology is unknown
  
  • Type 1 occurs in postmenopausal woman
    
    • Due to increase in osteoclast number, a result of oestrogen withdrawal
  • Type 2 occurs in elderly persons of both sexes
    
    • Generally occurs after age 80 and reflects attenuated osteoblast function
• Secondary osteoarthritis - etiology is known
  
  • Trauma
  • Previous joint disorders
  • Developmental dysplasia of hip (DDH)
    
    • Infection/inflammation

Question 3

List the risk factors of osteoarthritis

Answer 3

• Obesity
• Past injury of joint
• Occupational factors
• Genetics - female
• Age

Question 4

Describe the symptoms of osteoarthritis

Answer 4

• Deep aching joint pain, exacerbated by use
• Crepitis (grinding of hip)
• Reduced range of motion
• Stiffness during rest - morning stiffness
• Joint deformity

Question 5

Describe the features of osteoarthritis on x-ray

Answer 5

• Reduced joint space - no gap between bone
• Subchondral sclerosis - bone becomes white/marble when worn away
• Bone cysts - darker areas of bone
• Osteophytes - extra bone

Question 6

Describe the symptoms and causes of femoral neck fractures

Answer 6

• Fractures of the femoral neck are classified as intracapsular or extracapsular
• Symptoms include reduced mobility, sudden inability to bear weight on the limb, pain in the hip/groin/knee
• Intracapsular fractures are more common in the elderly, especially post-menopausal women with osteoporotic bone
• Extracapsular fractures more common in middle aged population through significant trauma

Question 7

Describe adjacent structures that could be damaged from femoral neck fracture

Answer 7

• Damage to femoral triangle
  
  • Can be due to open wound in buttock, groin and thigh
  • Leads to damage to blood supply and/or nerve damage
• Fascia iliaca block - femoral nerve block to reduce pain
  
  • Blunt needle hits fascia and pushes through and then injects anaesthetic
• Injury to buttock could damage sciatic nerve
  
  • Sits underneath external rotators and gluteus maximus
  • Damage to superior gluteal artery could kill
• Damage in car accident pushes femur head into pelvis and damage capsule and ligaments
  - Fracture of acetabulum

Question 8

Describe the consequences of intracapsular fractures in adults

Answer 8

• Medial femoral circumflex artery and lateral femoral circumflex artery form a extracapsular arterial ring at the base of the head of femur
• Ascending branches (retinacular arteries) supply the majority of blood to the head of femur
• Intracapsular fractures carry high risk of avascular necrosis of the bone if the middle femoral circumflex artery is disrupted

Question 9

Describe how intracapsular fractures in children are different

Answer 9

• In children, artery of ligamentum teres also helps supply the head of the femur
• Cartilage is soft and epiphyseal growth plate has not closed off the artery
• Risk of avascular necrosis in head of femur fracture is lowered

Question 10

Describe how intracapsular fractures can be treated

Answer 10

• Partial or full head replacement - need to replace arteries
• Hemiarthroplasty - full head replacement
• If non-displaced fracture, can use cannulated hip screws which give better outcome (dynamic hip screw)

Question 11

Describe how extracapsular fractures can be treated

Answer 11

• Use screws to fixate - intramedullary nail
• Blood supply maintained to heal bone
• Dynamic hip screw to allow slight movement to aid healing
  - Avoid remodelling to prevent bone spicules forming beyond fracture

Question 12

Describe the common clinical appearance of the limb after a displaced femoral neck fracture

Answer 12

• Shortened - distal fragment pulled upwards by muscles including glut medius and minimus, iliopsoas, sartorius and hamstrings
• Externally rotated - iliopsoas contracts and externally rotates femur distal to fracture as it has broken off
• Abducted - gluteus medius and minimus insert on greater trochanter

Question 13

Describe posterior dislocations of the hip and presentation

Answer 13

• 90% of hip dislocations are posterior
  
  • Eg. Knee impact in high-energy road traffic collision
• Leg presents as:
  
  • Shortened - femoral head pushed backwards out of acetabulum and pulled upwards by muscles
  • Internally rotated - glut medius and minimus contract and internally rotate hip
  • Flexed
  • Adducted
• Sciatic nerve palsy present in 8-20% of cases

Question 14

Describe anterior dislocation of hip and its presentation

Answer 14

• 8-9% of hip dislocations are anterior
  
  • Usually high energy trauma in young person
• Leg presents as:
  
  • Shortened
  • Externally rotated
    
    • Slightly flexed