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Updated: Jun 13 2021

Patella Sleeve Fracture

Images sleeve fracture.jpg
  • summary
    • Patellar Sleeve Fractures are rare injuries seen in children between 8 and 12 years of age characterized by separation of the cartilage "sleeve" from the ossified patella.
    • Diagnosis is made with radiographs of the knee.
    • Treatment is cylindrical casting for nondisplaced fractures with intact extensor mechanism. Operative management is indicated for displaced fractures associated with disrupted extensor mechanism.
  • Epidemiology
    • Incidence
      • <1% of pediatric fractures
      • accounts for >50% of patella fractures in children
    • Demographics
      • more common in males (5:1)
      • occurs in children 8-12 years old
        • when patellar ossification is nearly complete
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • indirect injury caused by powerful contraction of the quadriceps muscle applied to a flexed knee
      • pathoanatomy
        • separation between the cartilage "sleeve" and main part of the patella and ossific nucleus
  • Anatomy
    • Osteology
      • patella is largest sesamoid bone in body
        • ossification begins at 3-5 years old
      • 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
      • derived from anastomotic ring originating from geniculate arteries
      • most important blood supply to the patella is located at the inferior pole
  • Classification
    • Anatomic
      • superior pole
        • least common
      • inferior pole
        • most common
  • Presentation
    • History
      • indirect injury
        • not associated with a direct blow to the knee
    • Symptoms
      • severe knee pain
      • inability to bear weight
    • Physical exam
      • inspection
        • soft tissue swelling
        • diffuse tenderness
        • hemarthrosis of the knee joint is often present
        • high-riding patella or palpable gap at the distal end of the patella
          • indicates disruption of the extensor mechanism
      • motion
        • difficulty with active extension of the knee, especially against resistance
  • Imaging
    • Radiographs
      • recommended views
        • AP
        • lateral
        • tangential
      • findings
        • small flecks of bone adjacent to superior or inferior pole
          • diagnosis may be missed because the distal bony fragment is not readily discernible on radiographs
        • slight anterior tilt of superior pole
          • seen with proximal fractures
        • patella alta
          • seen with distal fractures
        • patella baja
          • seen with proximal fractures
    • MRI or ultrasound
      • indications
        • may be useful for identifying a sleeve fracture when the diagnosis is not clear from the clinical and radiographic findings
  • Treatment
    • Nonoperative
      • cylinder cast for 6 weeks
        • indications
          • nondisplaced fractures with intact extensor mechanism
            • rare (most require ORIF)
    • Operative
      • open reduction and internal fixation
        • indications
          • > 2-3mm displacement
          • > 2-3mm articular step-off
          • disrupted extensor mechanism
  • Technique
    • Open reduction and internal fixation
      • approach
        • medial parapatellar approach to knee
      • soft tissue
        • repair torn medial/lateral retinaculum and/or quadricept/patellar tendon
      • instrumentation
        • stabilize fracture using
          • transosseous sutures
          • modified tension band wiring
          • intraosseous suture anchors
          • interfragmentary screws
      • post-operative care
        • cylinder cast in extension for 2-3 weeks
  • Complications
    • Patella alta
    • Extensor lag
    • Quadriceps atrophy
    • Malunion
    • Nonunion
    • Painful hardware
  • Prognosis
    • Higher risk of complications associated with greater degree of
      • comminution
      • displacement
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