Patella Fracture

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Topic updated on 05/10/13 4:04pm
Introduction
  • Patella fractures account for 1% of all skeletal injuries
    • occur either by direct impact injury or indirect eccentric contraction
    • male to female 2:1
    • most fractures occur in 20-50 year olds
  • Patella sleeve fracture
    • seen in pediatric population (8-10 year olds)
    • high index of suspicion required
  • Bipartite patella 
    • may be mistaken for patella fracture 
    • affects 8% of population
    • characteristic superolateral position
    • bilateral in 50% of cases
Anatomy
  • Patella is largest sesamoid bone in body
  • Articular cartilage thickest in body (up to 1cm)
Classification
  • Can be described based on fracture pattern 
    • nondisplaced
    • transverse
    • pole or sleeve (upper or lower)
    • vertical
    • marginal
    • osteochondral
    • communited (stellate)
Presentation
  • Physical exam
    • palpable patellar defect 
    • significant hemarthrosis
    • unable to perform straight leg raise indicates failure of extensor mechanism 
      • retinaculum disrupted
Imaging
  • Radiographs
    • patella alta 
    • fracture displacement
      • best evaluated on lateral x-ray
      • degree of fracture displacement correlates with degree of retinacular disruption
  • MRI 
    • obtain MRI if child has normal xrays but is unable to straight leg raise
Treatment
  • Nonoperative
    • knee immobilized in extension (brace or cylinder cast) and full weight bearing
      • indications
        • intact extensor mechanism (patient able to perform straight leg raise)
        • nondisplaced or minimally displaced fractures
        • vertical fracture patterns
      • early active ROM with hinged knee brace
        • early WBAT in full extension 
        • progress in flexion after 2-3 weeks
  • Operative
    • ORIF with tension band construct
      • indications
        • preserve patella whenever possible 
        • extensor mechanism failure (unable to perform straight leg raise)
        • open fractures
        • fracture articular displacement >2mm
        • displaced patella fracture >3mm
        • patella sleeve fractures in children
      • techniques
        • minifrag lag screw fixation for independent fragments
        • tension bands
          • 0.062 K wires with figure of 8 wire 
          •  longitudinal cannulated screws combined with tension band wires shown to be biomechanically superior  
          • circumferential cerclage wiring 
            • good for communited fractures
          • interfragmentary screw compression supplemented by cerclage wiring 
    • partial patellectomy 
      • indications
        • comminuted superior or inferior pole fracture measuring <50% patellar height
      • techniques
        • quadricep or patellar tendon re-attachment
        • reattachment close to articular surface prevents patellar tilt
        • medial and lateral retinacular repair essential
    • total patellectomy 
      • indications
        • reserved for severe and extensive communition not ammenable to salvage
          • quadriceps torque reduced by 50%
          • medial and lateral retinacular repair essential
Complications
  • Symptomatic hardware
    • most common
  • Loss of reduction (22%)
    • increased in osteoporotic bone
  • Nonunion (<5%)
    • can consider partial patellectomy
  • Osteonecrosis (proximal fragment)
    • thought to be due to excessive initial fracture displacement
    • can observe these, as most spontaneously revascularize by 2 years
  • Infection
  • Stiffness

 

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Qbank (3 Questions)

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(OBQ07.207) Partial patellectomy is the recommended treatment for which of the following injuries? Topic Review Topic

1. Vertical patella fractures
2. Patellar tendon rupture
3. Comminuted inferior pole fracture
4. Stellate patella fracture
5. Chronic quadriceps tendon rupture

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Cases

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HPI - fracture patella , motor vehicle accident, no dm or ht non alcoholic non smoker
poll What would you do for this multi fragment patella fracture?
10/13/2011
13 responses
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HPI - fall from ladder
poll what would yield good result for the fracture
12/12/2011
24 responses
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