Lower Limb Trauma Flashcards
Anatomical and physiological consequences of injury
- Anatomical
> Fracture
> Dislocation
> Soft tissue injury - Physiological
> Bleeding + shock
> Coagulopathy
> Multiple organ failure
How many places does a rigid ring tend to fracture in?
At least 2
What are the rigid rings of the pelvis?
- Main pelvic ring
- 2x obturator rings
Main function of anterior ligaments of pelvis
Stabilise pubic symphysis
Anterior ligaments of the pelvis
- Superior pubic ligament
- Arcuate ligament
Relative strength of anterior ligaments of the pelvis and what this means
- Relatively weak compared to rest of pelvis
- Pubis symphysis disruption is common
Main function of secondary ligaments of the pelvis
- Stop sacrum, and therefore spine, from tilting forward
- Keep pelvic ring stable
Secondary ligaments of the pelvis
- Sacrotuberous ligament
- Sacrospinous ligament
- Iliolumbar ligament
Main function of posterior ligaments of the pelvis
Stabilise sacroiliac joint (for weight bearing)
Posterior ligaments of the pelvis
- Anterior sacroiliac ligament
- Interosseus sacroiliac ligament
- Posterior sacroiliac ligament
What is APC in pelvic injury?
- Antero-posterior compression
- Occurs when motor cyclist hits tree –> front of pelvis hits petrol tank
3 stages of APC injury
- APC 1
- APC 2
- APC 3
What happens in an APC 1 injury?
- 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
What happens in an APC 2 injury?
- Greater force applied to front of pelvis
- Damage to anterior + secondary ligaments
- Results in sacroiliac joint being disrupted so pelvis hinges open
What happens in an APC 3 injury?
- 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)
Why are haemorrhages often associated with pelvic fractures?
Damage to pelvic floor
Why are haemorrhages often associated with pelvic fractures?
Damage to pelvic floor which is covered by major vascular structures
How is haemorrhage controlled?
Embolization (blockage of vessel)
Why are hip fractures more common in elderly patients?
Weak bones
3 types of hip fracture
- Intracapsular
- Trochanteric
- Subtrochanteric
Where are subtrochanteric fractures located?
Within 5cm below lesser trochanter
Characteristic deformities of hip fracture
- Shortening of leg
- External rotation of leg
Why does shortening of the leg occur in a hip fracture?
- Action of muscles that cross the hip joint
> Hip abductors (gluteus medius + minimus) + flexors (iliacus + psoas major)
Why does external rotation of the leg occur in a hip fracture?
- 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)
3 ligaments of hip joint
- Iliofemoral ligament
- Ischiofemoral ligament
- Pubofemoral ligament
What line needs to be assessed in an X-ray of a hip fracture?
Shenton’s line
What is Shenton’s line?
Imaginary line drawn along inferior border of superior pubic ramus + along inferomedial border of neck of femur
Where does anterior blood supply to the femoral head come from?
Lateral circumflex femoral artery (branch of profunda femoris)
Where does posterior blood supply to the femoral head come from?
Medial circumflex femoral artery (branch of profunda femoris)
When would the femoral head undergo avascular necrosis?
- Intracapsular fracture
- Cuts of retinacular vessels coming from medial/lateral circumflex arteries
What procedure is used to treat a displaced femoral fracture?
Hemiarthroplasty (half hip joint replaced)
What position is the proximal femur in after a subtrochanteric fracture and why?
- Abducted (gluteus medius + minimus)
- Flexed (iliacus + psoas major)
Treatment of a subtrochanteric fracture
- 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)
Which ligaments make knee dislocation so uncommon?
- Lateral + medial collaterals
- Posterior + anterior cruciates
What is the vascular danger of a knee dislocation?
- Popliteal artery lies directly behind the joint
- Can cut off blood supply to lower limb
Causes of increased pressure in a muscle compartment
- Increased pressure from inside (bleeding + oedema)
- Increased pressure from outside (tight casts + dressings)
Consequences of compartment syndrome
- 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
Treatment of compartment syndrome
- Remove bandages around area
- Fasciotomy
