Apophyseal Injuries


KEY FACTS

Terminology

  • Apophysis: Nonarticular secondary center of ossification that serves as attachment site for muscle or tendon

  • Acute injury: Avulsion fracture of osseous &/or cartilaginous apophysis through subjacent physis

  • Chronic injury: Repetitive submaximal tensile forces (avulsive microtrauma) exceed rate of repair, leading to local growth plate disturbance (± symptoms)

Imaging

  • Acute injury: Displaced apophyseal ossification center

  • Chronic injury: Mild soft tissue swelling with ossific irregularity &/or physeal widening at tendon attachment site

  • Radiographs usually diagnostic of acute avulsion

  • Further imaging may be required if fragment nondisplaced, ossification center not yet present, or chronic apophysitis suspected

    • MR more sensitive & specific than US

Top Differential Diagnoses

  • Osteomyelitis

  • Osteosarcoma

  • Muscle injury

  • Stress injury of bone

Clinical Issues

  • Acute injury: Sudden onset of pain with sensation of “pop” & instant ↓ of muscle function during athletic activity

  • Chronic injury: Insidious onset of pain & swelling without specific event or associated bruising

  • Most acute pelvic avulsions occur from ages 12-18 years

    • Most occur during kicking or sprinting

      • Soccer, gymnastics, rugby, track & field

    • AIIS, ASIS, ischial tuberosity > iliac crest, pubic symphysis

  • Conservative (nonsurgical) therapy: Highly successful

  • Surgical fixation reserved for displacement > 1.5-2.0 cm

Frog leg lateral radiograph in a 13-year-old girl with acute onset of left hip pain & the sensation of a “pop” during cheerleading shows displaced bony fragments
adjacent to the left ischial tuberosity.

Coronal T2 FS MR in the same patient shows the attachments of the hamstring tendons
to the displaced curvilinear osteocartilaginous apophysis
at the ischial tuberosity. Fluid
undercuts the displaced fragment, typical of an acute avulsion injury.

AP radiograph in a 16-year-old boy with a history of pain & a “pop” while kicking a ball shows an inferiorly displaced bony fragment
avulsed from the anterior superior iliac spine. The lateral left iliac wing apophysis
also shows fragmentation & growth plate widening, suggesting avulsion.

Lateral radiograph in a 13 year old shows a tibial tubercle avulsion
with the fracture line extending superiorly through the epiphysis
. Note the marked soft tissue edema
& high-riding patella
.

TERMINOLOGY

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