Lower Limb Trauma

Question 1

Anatomical and physiological consequences of injury

Answer 1

• Anatomical
  > Fracture
  > Dislocation
  > Soft tissue injury
• Physiological
  > Bleeding + shock
  > Coagulopathy
  > Multiple organ failure

Question 2

How many places does a rigid ring tend to fracture in?

Answer 2

At least 2

Question 3

What are the rigid rings of the pelvis?

Answer 3

• Main pelvic ring
• 2x obturator rings

Question 4

Main function of anterior ligaments of pelvis

Answer 4

Stabilise pubic symphysis

Question 5

Anterior ligaments of the pelvis

Answer 5

• Superior pubic ligament
• Arcuate ligament

Question 6

Relative strength of anterior ligaments of the pelvis and what this means

Answer 6

• Relatively weak compared to rest of pelvis
• Pubis symphysis disruption is common

Question 7

Main function of secondary ligaments of the pelvis

Answer 7

• Stop sacrum, and therefore spine, from tilting forward
• Keep pelvic ring stable

Question 8

Secondary ligaments of the pelvis

Answer 8

• Sacrotuberous ligament
• Sacrospinous ligament
• Iliolumbar ligament

Question 9

Main function of posterior ligaments of the pelvis

Answer 9

Stabilise sacroiliac joint (for weight bearing)

Question 10

Posterior ligaments of the pelvis

Answer 10

• Anterior sacroiliac ligament
• Interosseus sacroiliac ligament
• Posterior sacroiliac ligament

Question 11

What is APC in pelvic injury?

Answer 11

• Antero-posterior compression
• Occurs when motor cyclist hits tree –> front of pelvis hits petrol tank

Question 12

3 stages of APC injury

Answer 12

• APC 1
• APC 2
• APC 3

Question 13

What happens in an APC 1 injury?

Answer 13

• Relatively low force applied to front of pelvis
• Anterior ligaments damaged
• This forces pelvis apart from the front
• Secondary + posterior ligaments having elasticity results in small opening in front of pelvis

Question 14

What happens in an APC 2 injury?

Answer 14

• Greater force applied to front of pelvis
• Damage to anterior + secondary ligaments
• Results in sacroiliac joint being disrupted so pelvis hinges open

Question 15

What happens in an APC 3 injury?

Answer 15

• Even greater force applied
• Causes pelvic ring injury which is vertically unstable
• Whole of affected side of pelvis (+ lower limb) will move proximally (due to muscle pull)

Question 16

Why are haemorrhages often associated with pelvic fractures?

Answer 16

Damage to pelvic floor

Question 17

Why are haemorrhages often associated with pelvic fractures?

Answer 17

Damage to pelvic floor which is covered by major vascular structures

Question 18

How is haemorrhage controlled?

Answer 18

Embolization (blockage of vessel)

Question 19

Why are hip fractures more common in elderly patients?

Answer 19

Weak bones

Question 20

3 types of hip fracture

Answer 20

• Intracapsular
• Trochanteric
• Subtrochanteric

Question 21

Where are subtrochanteric fractures located?

Answer 21

Within 5cm below lesser trochanter

Question 22

Characteristic deformities of hip fracture

Answer 22

• Shortening of leg
• External rotation of leg

Question 23

Why does shortening of the leg occur in a hip fracture?

Answer 23

• Action of muscles that cross the hip joint
  > Hip abductors (gluteus medius + minimus) + flexors (iliacus + psoas major)

Question 24

Why does external rotation of the leg occur in a hip fracture?

Answer 24

• Normally rotation occurs around mechanical axis of femur (between centre of femoral head + centre of knee joint)
• When fractured, it occurs around anatomical axis (shaft of femur)

Question 25

3 ligaments of hip joint

Answer 25

- Iliofemoral ligament - Ischiofemoral ligament - Pubofemoral ligament

Question 26

What line needs to be assessed in an X-ray of a hip fracture?

Answer 26

Shenton's line

Question 27

What is Shenton's line?

Answer 27

Imaginary line drawn along inferior border of superior pubic ramus + along inferomedial border of neck of femur

Question 28

Where does anterior blood supply to the femoral head come from?

Answer 28

Lateral circumflex femoral artery (branch of profunda femoris)

Question 29

Where does posterior blood supply to the femoral head come from?

Answer 29

Medial circumflex femoral artery (branch of profunda femoris)

Question 30

When would the femoral head undergo avascular necrosis?

Answer 30

- Intracapsular fracture - Cuts of retinacular vessels coming from medial/lateral circumflex arteries

Question 31

What procedure is used to treat a displaced femoral fracture?

Answer 31

Hemiarthroplasty (half hip joint replaced)

Question 32

What position is the proximal femur in after a subtrochanteric fracture and why?

Answer 32

- Abducted (gluteus medius + minimus) - Flexed (iliacus + psoas major)

Question 33

Treatment of a subtrochanteric fracture

Answer 33

- Line distal + proximal fragments by either: > Pushing from front to push fragment down > Placing spike in the bone and pulling it down to a ligament - Then do an intramedullary nailing (rod on inside of bone + fix with screws)

Question 34

Which ligaments make knee dislocation so uncommon?

Answer 34

- Lateral + medial collaterals - Posterior + anterior cruciates

Question 35

What is the vascular danger of a knee dislocation?

Answer 35

- Popliteal artery lies directly behind the joint - Can cut off blood supply to lower limb

Question 36

Causes of increased pressure in a muscle compartment

Answer 36

- Increased pressure from inside (bleeding + oedema) - Increased pressure from outside (tight casts + dressings)

Question 37

Consequences of compartment syndrome

Answer 37

- If decompression is late there is a severe risk of infection as dead muscle is ideal culture medium - Myoglobin can leak into circulation + cause renal damage --> renal failure

Question 38

Treatment of compartment syndrome

Answer 38

- Remove bandages around area - Fasciotomy