Plaster of Paris Casts: Immobilization, Care, and Complications

Posted on Feb 24, 2025 in Medicine & Health

Plaster of Paris Cast Immobilization

Plaster of Paris (POP) Cast immobilization is a common method for stabilizing fractures and injuries. Plaster of Paris casts have a long history of use. Plaster of Paris (Gypsum salt) is CaSO4. ½ H2O in dry form, which becomes CaSO4.2H2O upon wetting. This conversion is an exothermic and irreversible reaction. The plaster sets into a rigid form as it dries. The setting time varies depending on the plaster’s quality and the water temperature.

Types of Plaster Bandages

There are two main types of plaster bandages:

  • Home-made bandages: Prepared by impregnating rolls of starched cotton bandages with plaster powder.
  • Readymade bandages: Proprietary bandages available for immediate use.

Uses of Plaster of Paris

Plaster of Paris can be applied as a slab or a full cast. A plaster slab covers only part of a limb’s circumference and is made by layering a plaster bandage to the desired thickness (typically around twelve layers). Slabs are used for soft tissue injuries and to reinforce plaster casts.

A plaster cast covers the entire circumference of a limb. Its thickness depends on the fracture type and the body part being treated. Key principles for applying a plaster cast include:

  • Immobilize the joints above and below the fracture.
  • Immobilize joints in a functional position.
  • Pad the limb adequately, especially over bony prominences.

Aftercare of a Plaster Cast

Proper aftercare is crucial and involves:

  • Checking for cracks in the plaster.
  • Avoiding getting the plaster wet.
  • Gradually increasing weight-bearing for lower limb fractures.
  • Exercising muscles within the cast and moving joints not immobilized by the cast to promote recovery.

Complications of Plaster Cast Treatment

Potential complications include:

  • Impairment of circulation (tight cast): A plaster cast creates a closed compartment. Hematoma and tissue edema after a fracture can increase pressure inside the cast, impairing circulation. Signs of a tight cast include:
    • Unrelenting pain, especially stretch pain
    • Swelling of the fingers or toes
    • Inability to move fingers or toes
    • Hypoesthesia (decreased sensation)
    • Bluish discoloration of the digits
    Prevention involves adequate padding and elevating the extremity for the first 2-3 days after application.
  • Plaster sores: Caused by inadequate padding, irregularities on the cast’s inner surface, or foreign objects inside the cast. Signs of a plaster sore include:
    • Pain disproportionate to the fracture
    • Fretfulness
    • Disturbed sleep
    • Recurrence of swelling in toes or fingers
    • Low-grade fever
    • Blood or drainage on the cast
    Suspected areas can be examined through a window cut in the cast, allowing for dressing small sores. In some cases, the cast must be removed and reapplied.

Thomas Knee Bed Splint (Thomas Splint)

The Thomas splint was originally designed for immobilizing tuberculosis of the knee. It is now commonly used for hip and thigh injuries.

Parts of a Thomas Splint

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