April 11, 2024

A functional cast is a type of bracing where the limb is allowed to do functions with a brace kept in .

It helps in continuing function while a fracture is uniting encourages osteogenesis promotes the healing of tissue and prevents the development of joint stiffness (accelerate rehabilitation)

This is not a method of fracture reduction but an attitude towards fracture healing

Requirement of fracture healing:


Maintainance of reduction

Blood supply

Pascal law

Fluid is not compressible

Hydraulic container theory for functional cast
Hydraulic container theory

The force applied on any area of an enclosed liquid is transmitted equally to all areas throughout the enclosure

Fascia cannot be stretched beyond the confines of cast

Stability is maintained by more loading

Physiology of functional cast bracing
Physiology of functional cast bracing

Liquid: Not compressible

Muscle is equivalent to Liquid: Sarmiento

Pressure and load are transmitted without further deformation

Rotation is restricted by components of the brace

Muscle Contraction

Intermittent bending/loading of the fracture area by muscle activity and weight-bearing, promote local blood flow and development of electric field which are beneficial for healing

Loading: Contraction of muscle: Micromotion at the fracture site: Increase blood supply: Bridging callus
Loading: Contraction of muscle: Micromotion at the fracture site: Increase blood supply: Bridging callus

Indications of functional cast

All middle third shaft fracture

Lower third junctional fractures

Cooperative patients


  • Fracture ends sticky
  • Access the fracture, when pain and swelling subsided
    1. Minor movement at the fracture site should be pain-free
    2. Any deformity should disappear once distractor force removed
    3. Reasonable resistance to telescoping
    4. The shortening should not exceed 6.0mm in the tibia, 1.2 cm in the femur


  1. Intraarticular fractures
  2. Compound fractures
  3. Lack of cooperation by the patient
  4. Patients with spastic disorders
  5. Bedridden and mental incompetent patient
  6. The deficient sensibility of the limb
  7. Fracture both bone forearm when reduction is difficult

Acceptable Reduction following functional cast

  • 50% cortical contact
  • < 5-10° valgus/varus angulation
  • < 10-15° of anterior-posterior bowing
  • < 5-7° degrees of internal/ external rotations
  • No more than 10-15 mm shortening


  • PTB Cast
  • The functional cast of the humerus

Gypsum (CaSO4.2H20)

Derived from the Greek word: “to cook

CaSO4.2H2O => 110-120C


CaSO4 (Hexagonal anhydrate)

CaSO4 (Orthorhombic anhydrate)

Types of POP

See also: Kapandji techniques for distal radius fracture

See also: External Fixator Principles

See also: Total Contact Casting (TCC)

See also: Tension Band Principles (TBW)


See also: Properties of metals

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