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https://upload.orthobullets.com/topic/4120/images/patella sleeve fracture.jpg
https://upload.orthobullets.com/topic/4120/images/psorif.jpg
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Introduction
  • Overview
    • patellar sleeve fractures are a rare injury seen in children between 8 and 12 years of age characterized by separation of the cartilage "sleeve" from the ossified patella
      • most fractures are displaced and require treatment with open reduction and internal fixation
  • 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
  • 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 
  • Prognosis
    • higher risk of complications associated with greater degree of
      • comminution
      • displacement
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 pol
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 open reduction - periosteal sleeve (white arrow) and inferior pole cartilage (asterisk) opposite cancellous bone of the main patella (black arrow).
      • 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 (A) Patellar “sleeve” fracture. (B) and (C) demonstrate AP and lateral x-ray of the knee after reduction and fixation with Kirschner wires and 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
 

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(OBQ09.77) A 10-year-old female presents to the emergency department complaining of anterior knee pain after a fall from her bicycle. Exam reveals ecchymosis and swelling over the patella and an extensor lag. Radiographs are shown in Figures A and B. What is the most appropriate next step in treatment? Review Topic

QID: 2890
FIGURES:
1

Open reduction and suture fixation

76%

(871/1143)

2

Open reduction and internal fixation with plating and wire cerclage technique

5%

(57/1143)

3

Cylinder cast

5%

(52/1143)

4

Partial patellectomy and advancement of patellar tendon

3%

(37/1143)

5

Patellar tendon midsubstance rupture repair with nonabsorbable suture

11%

(124/1143)

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