Introduction
  • Epidemiology
    • incidence
      • patella fractures account for 1% of all skeletal injuries
    • demographics
      • male to female 2:1
      • most fractures occur in 20-50 year olds
  • Mechanism of injury
    • direct impact injury
      • occurs from fall or dashboard injury
        • causes failure in compression
    • indirect eccentric contraction
      • occurs from rapid knee flexion against contracted quads muscle
        • causes failure in tension
      • patella sleeve fracture
        • seen in pediatric population (8-10 year olds)
        • high index of suspicion required
  • Associated injuries
    • high-energy dashboard injuries are associated with femoral neck fracture, posterior wall acetabular fracture, or knee dislocation
  • Prognosis
    • osteonecrosis reported to occur in up to 25% but not found to affect clinical outcome
Anatomy
  • Osteology 
    • patella is largest sesamoid bone in body
    • superior 3/4 of posterior surface covered by articular cartilage
      • articular cartilage thickest in body (up to 1cm)
    • posterior articular surface comprised of medial and lateral facets
      • lateral facet is larger
      • facets separated by vertical ridge
  • Soft tissue attachments 
    • quadriceps tendon and fascia lata attach to anterosuperior margin
      • quadriceps tendon comprised of 3 layers
        • superficial layer formed from rectus femoris tendon
        • middle layer formed by vastus medialis and vastus lateralis tendons
        • deep layer formed by vastus intermedius tendon
    • patellar tendon attaches to inferior margin
  • Blood Supply 
    • derives from anas