Patella fractures

HPI: young male s/p ATV accident

Exam: Inspection: edema and deformity. No open wounds.  Palpation: TTP, palpable deformity. 2+ DP/PT pulses. SILT lower extremity. ROM: unable to perform straight leg raise. limited ROM secondary to pain. Limited assessment of anterior/posterior drawer, varus/valgus testing

Imaging:
 # Best seen on lateral xray. 
#In pediatric patients, MRI if xrays do not show fracture and child unable to perform straight leg raise

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Bipartate patella: 
#often mistaken for fracture-use history and clinical exam
#8-10 % of population, 50 % bilateral, usually superolateral

Fracture Patterns:

• nondisplaced
• transverse
• pole or sleeve (upper or lower)
• vertical
• marginal
• osteochondral
• comminuted (stellate)

Management:
# Nonoperative:
-Extensor mechanism intact (straight leg test)
-nondisplaced/minimally displaced
-vertical fractures
-Knee immobilized in extension (cylinder cast/brace)

#Operative
-extensor mechanism failure
-open fractures
-articular displacement > 2 mm
-displacement > 3 mm
-patella sleeve fractures in children (fracture between cartilage sleeve and patella)
-severely communited fractures

Discussion:
-Patella fractures 1 % of skeletal injuries
-Mechanism: direct impact of indirect eccentric contraction
-Complications: weakness and anterior knee pain, loss of reduction, nonunion, osteonecrosis, infection, stiffness

Key Points:  
#History of mechanism and exam is important-especially palpation, straight leg testing
#Best seen on lateral xray, consider MRI in pediatric patients given history and exam findings
#Bipartate patella-seen in 8-10 % of population, usually superolateral
#Orthopedic consultation-open vs closed, fracture pattern, straight leg testing, displacement
#Consider patella sleeve fractures in pediatric patients
#Management-minimally displaced, vertical, closed, extensor mechanism intact-immobilize in brace or cast and follow up as outpatient; Open, extensor mechanism not intact, communited, displaced-surgical

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