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Casts and Splints

  • Casts and splints are used to immobilize injured bones and joints.
  • Because casts are circumferential and do not accommodate postinjury swelling, acute injuries usually should be treated with splints, which have a lower risk of iatrogenic compartment syndrome.
  • In the field after an injury, almost anything can be used as splint material, including sticks, slats of wood, a pillow, or cardboard.
  • It is important to pad the splint in areas where it contacts the skin to prevent pressure injuries and protect the soft tissues.
  • Splints are applied to immobilize not only the fractured bone, but the joint above and below the fracture.
  • In a hospital setting, splints and casts are made of 2 substances, plaster and fiberglass.
    • Plaster of Paris:
      • Made of muslin stiffened by dextrose or starch and impregnated with the hemihydrate of calcium sulfate
      • When water is added, the calcium sulfate crystallizes in an exothermic reaction.
      • Plaster solidifies in ~15 minutes.
    • Fiberglass:
      • More modern material made of a fiberglass substrate impregnated with a polyurethane resin that is activated by moisture to polymerize
      • Hardens in ~7 minutes and weighs less than plaster
      • Disadvantages:
        • Sticky and hard-to-remove from exposed skin; latex gloves should be used to protect the hands.
        • The fast hardening time can make molding more difficult than with plaster.
  • Injured bones and muscles release inflammatory substances such as interleukin-6.
  • Motion of broken bones at a fracture site creates more inflammation and potential muscle injury.
  • Immobilization of the limb and fracture limits this motion and leads to pain relief and gradual decrease of inflammation.
Signs and Symptoms
Patients with fractures after trauma
Physical Exam
  • Examine patients for wounds and open fractures that require urgent surgical debridement.
  • Examine joints for signs of dislocation.
  • Evaluate neurovascular status thoroughly for nerve or vessel injury.
  • Examine patients for swelling and signs of compartment syndrome.
Patients with painful bones or joints should be evaluated with radiographs for fracture or dislocation.
General Measures
  • Immobilization in the acute period after an injury is best provided by a splint.
  • After swelling of the initial injury has been reduced, a cast may be applied to hold the fracture until healing.
    • Generally, injuries are casted 1 or 2 weeks after the injury.
    • If casts are applied immediately after injury, they should be cut or bivalved and loosely wrapped.
  • Before splint or cast application, the extremity must be padded well with cast padding or felt, especially over bony prominences.
  • Rings or bracelets must be removed from the affected extremity.
  • Limbs should be splinted in the position of function of the joint.
  • The joints above and below the fracture should be immobilized.
  • Hot water should not be used because it may lead to thermal burns under the splint.
  • Indentations from fingers may cause pressure points and should be avoided.
  • 3-point fixation and molding should be used to stabilize the fracture.
  • Open fractures, which require emergency surgery, should be splinted before surgery.
  • Specific consideration should be given by anatomic area.
    • Proximal humerus and humeral shaft fractures:
      • Place plaster over the shoulder and on either side of the arm.
      • Place a sling.
      • Place a removable pad in the armpit so it can be changed and the armpit cleaned.
      • When fractures have begun to heal, a fracture brace may be applied to the humerus.
    • Elbow:
      • Splint the elbow at 90°, with plenty of padding and with a back slab.
      • A side slab can be used for reinforcement.
      • The wrist should be supported by the splint, but the hand should be free.
      • An above-the-elbow cast can be placed after swelling has reduced.
    • Forearm and wrist:
      • A sugar-tong splint extends around the elbow, with the elbow bent at 90°.
      • On either side of the hand, it is important to leave the MCP joints free.
      • Below-the-elbow casts should leave the hand and thumb free to move.
    • Hand and fingers:
      • The boxer splint or ulnar gutter splint can be used for 4th and 5th metacarpal fractures.
      • Place 4-inch plaster from the tip of the 5th finger to 2 inches from the antecubital fossa, with a gauze pad between the 4th and 5th fingers.
      • The splint is applied to the ulnar side of the hand to create a gutter.
      • The wrist is positioned at 25-30° of extension and the MCP joint at 90° of flexion.
      • To splint finger fractures, use structural aluminum malleable splints (made of a strip of soft aluminum, coated with polyethylene foam), which can be cut into strips with scissors.
    • Femur and hip:
      • Thomas splints are a premade splinting device used to apply traction to a leg.
      • The splint has a ring that measures 2 inches more than the circumference of the proximal thigh and engages the ischial tuberosity for countertraction.
      • A strap is placed anteriorly and attached to the end of the splint with an ankle hitch.
      • This splint can be used temporarily to apply traction to the leg but should not be left in place for >2 hours because the ankle hitch places substantial pressure on the skin and may cause skin necrosis.
    • Knee and tibia:
      • Above-the-knee splints extending to the end of the foot should be used; the ankle should be splinted at 90°.
      • Care must be taken to pad the peroneal region around the knee and the ankle.
      • For stable fractures, above-the-knee casts may be used after swelling has subsided.
    • Ankle and foot:
      • Below-the-knee splints are applied with a U around the ankle and a back slab.
      • The ankle should be kept at 90° to avoid Achilles contracture.
      • Below-the-knee casts must be padded carefully.
      • Ankle injuries that require less support may be treated with an ankle air splint.
Patients should be encouraged to move the joints above and below the splint to prevent joint stiffness; joints that stiffen quickly include the shoulder, elbow, and hand.
  • Patients should be evaluated (including a neurovascular check) to make sure that the splint is not too tight.
Medication (Drugs)
First Line
Patients with fractures generally require narcotic pain medicines.
Fractures that are open, intra-articular, or displaced may require surgical fixation.
Issues for Referral
  • Patients with splinted fractures should be referred to an orthopaedist for management.
  • In general, patients should be seen within a week to assess the reduction of the fracture and the need for operative intervention.
  • Casts or splints may be too tight.
    • Patients complaining of continued pain and tightness should be examined, and the splint or cast should be loosened.
    • If loosening is not effective in reducing pain, the limb should be checked carefully for compartment syndrome.
      • Cut the splint material and assess the limb.
      • Check pressure measurements to evaluate the intracompartmental pressure.
      • If compartment syndrome is diagnosed, urgent fasciotomy is required to preserve limb function.
  • To prevent skin breakdown, careful attention should be paid to providing adequate padding to boney prominences.
Patient Monitoring
  • Patients require monitoring for soft-tissue swelling and compartment syndrome.
  • Fracture reduction should be monitored with serial radiographs until healing.
Patient Teaching
  • After application of any splint or cast, the patient should be instructed to:
    • Be aware of the signs and symptoms of compression from swelling within the splint (numbness, tingling, pain).
    • Keep the splint dry.
    • Call the clinician in case of splint problems or symptoms of compression.
    • Make appointment for a follow-up examination.
  • Comply with weightbearing restrictions.
  • Exercise joints not incorporated in the splint.
  • Elevate the injured limb above the level of the heart for 2-3 days.
Q: Can I take the splint off?
A: No, the splint must remain in place unless removal is needed for more detailed examination of the extremity or if it is to replaced by another splint or cast. Splints should not be removed for radiographs unless any metal will obscure images, in which case a nonradiodense splint should be applied.
Q: Why is a cast not applied immediately after the injury?
A: Casts are circumferential and do not allow for swelling. Splints apply pressure only on 1 or 2 sides of the extremity, which should allow for swelling. However, if the splint feels too tight, it should be loosened.

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