Plastic Deformation Fracture
Acute Plastic Bowing

 

General Considerations

  • Deformation of the bone due to longitudinal stress
  • Almost exclusively in children ages 2-5
  • Produced by numerous microfractures on the concave surface of the bone with an intact cortex on the convex surface
  • Most common in the forearm and may affect radius or ulna
    • Most common form involves bowing of ulna with fracture of radius
  • Rarity of these injuries (relative to actual fracture) is due to fact that
    • Force must be exactly longitudinal
    • Force must be greater than the maximal strength of the bone, and
    • The force must be of shorter duration than the time it would take for a gross fracture to occur
  • May also occur in the femur and fibula

Clinical Findings

  • Usually produced by fall on an outstretched arm
  • Usually produces deformity of the forearm
  • If the shoulder is internally rotated and the forearm is pronated, an angulated fracture of radius with bowing of ulna will result
  • If the shoulder is externally rotated and the forearm is supinated, will produce a fracture of the ulna with bowing of the radius
  • A combination of forces may lead to plastic bowing of both radius and ulna
  • Monteggia fracture-dislocations are relatively less common in children
    • They classically result in an angulated fracture of the ulna, the apex pointing in the same direction as a dislocation of the radial head

Imaging Findings

  • Bowing of one or both bones of the forearm, especially when compared to the normal side
  • Lateral view is usually best at demonstrating bowing
  • Ulnar bowing is usually convex posteriorly
  • Radial bowing is usually convex anteriorly
  • Bone scan may show increased uptake on concave surface of bone

Treatment

  • If child is < 4 years old, angulations < 20 degrees will usually remodel
  • Over 4 years of age, frequently requires surgical correction.
  • Correction is generally indicated for plastic bowing fracture which restricts movement or prevents reduction of an adjacent  fracture or dislocation

Complications

  • Narrowing of the interosseus space restricting pronation and supination
  • Bowed bones remain bowed
  • May maintain an adjacent fracture in angulation
  • May prevent reduction of an adjacent dislocation

 

Plastic Deformation Fracture, acute plastic bowing

Acute plastic bowing of the ulna. Two views of the forearm in a child show a fracture of the radius (solid white arrow) with angulation and concomitant shortening associated with acute plastic bowing of the ulna (dotted white arrow) anteriorly. There is no dislocation of the radial head as a line (black line) drawn through the shaft of the radius intersects the capitellum on both views.
For more information, click on the link if you see this icon

For this same photo without the annotations, click here

       

Anterior Dislocation of the Radial Head with Plastic Bowing of the Ulna Introducing Modification to Bado’s Classification; S. Goyal, M.Ch(orth). A. Hussain M.Ch(orth).JK-Practitioner2005;12(1):20-23

 1 Roentgen Recognition Of Acute Plastic Bowing Of The Forearm In Children; Spencer Borden, MD; AJR, vol. 125, No. 3