The Short Arm Cast

Daniel L. Stulberg, MD, FAAFP
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Subject: The Short Arm Cast

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Introduction

Patients with orthopedic injuries commonly present to primary care offices or are referred there if the practitioner is skilled in their management. Knowing how to apply basic casts can expand one’s practice of medicine and assist in the management and satisfaction of one’s patients. Although most displaced fractures are managed with orthopedic consultation, primary care physicians manage many uncomplicated or nondisplaced fractures. Properly trained generalists may also perform some reductions. 
The objective of early fracture management is immobilization of the fracture fragments. Internal fixation accomplishes this goal, but the costs and risks of internal fixation may be unnecessary for fractures that can be effectively treated with external devices such as casts. Casts are circumferential, rigid, molded to fit a body part, and do not accommodate swelling. Typically, they should be applied only after a period of splinting, usually 2 to 14 days, to allow resolution of swelling. Casts can be applied immediately for a clinical situation in which swelling is insignificant, such as with a suspected scaphoid fracture. A cast never completely immobilizes a fracture, but a well-molded cast provides enough relative immobilization to allow a fracture to heal. Casts provide the additional benefits of pain relief, protection of surrounding tissues (e.g., vessels, nerves), and maintenance of position after reduction of fracture fragments. 
When applying a cast, place the injured part in a position of function, unless alternate positioning is required by the clinical situation. The position of function for the forearm is easily achieved by asking the patient to position the hand and wrist as if drinking a glass of water. 
Plaster of Paris has been extremely popular as a cast material because of its ease of use, long shelf life, and low cost. Synthetic materials such as fiberglass provide the benefit of light weight and added strength, but at additional cost. The shelf life of some synthetic materials can be <6 months; the shelf life can be extended by turning over the packages every few months to prevent drying. 

Equipment

  • Cast material: fiberglass or plaster, two 2-, 3-, or 4-inch rolls based on patient size

  • Stockinette: cotton or for waterproof casts—synthetic (3M Synthetic Cast Stockinette)

  • Cast padding: Cotton (BSN Specialist Cotton Cast Padding) or either synthetic cast padding (3M Scotchcast Wet or Dry Cast Padding or cast liner (Procel–Gore Cast Liner) for waterproof casts

  • Nonsterile gloves

  • Water basin

  • Cast saw with vacuum attachment

  • Cast spreader

  • Bandage scissors

  • A cut-resistant plastic strip (De-Flex Protective Strip) that provides protection from cuts and burns from cast saws during cast removal (optional if standard padding used)

Indications

  • Colles fracture (nondisplaced or after reduction)

  • Nondisplaced metacarpal fractures

  • Torus (buckle) or greenstick fracture of the distal radius

  • Nondisplaced or suspected scaphoid fracture (refer if more than 1 mm of displacement)

  • Clinically suspected scaphoid fracture with negative initial x-ray

Relative Contraindications

  • Unfamiliarity with appropriate methods or techniques

  • Fractures best managed by specialty referral or surgical reduction or intervention

  • Improperly functioning equipment (e.g., cast saw)

  • Infection in tissues to be covered by a cast

  • Open fractures

The Procedure

Step 1

A single layer of stockinette is applied, typ-ically 3 inches. Cut the stockinette long enough so that it goes from the elbow to the distal interphalangeal joint of the third finger. 

Step 2

Cut a hole for the thumb. For scaphoid fractures, a thumb extension (spica) is added with 1-inch stockinette split at the base to overlap onto the radial aspect of the 3-inch stockinette and covering to the end of the thumb. 

Step 3

Apply the stockinette. The extra length on each end helps to create smooth edges on the cast. 

Step 4

Apply the cast padding (starting either proximal or distal) covering from approximately 1 to 1.5 inches from the flexed elbow to the flexural crease of the palm to allow for adequate range of motion of the unaffected joints. The cast padding is applied to a double thickness by overlapping the roll 50% each turn. 

Step 5

An extra roll of padding at the elbow as shown or a folded piece of padding at the palmar end of the cast help to reduce chafing and make the cast more comfortable at the cast ends. 

Step 6

Partially tear the padding to slip the padding next to and around the base of the thumb. 

Step 7

Apply cast padding and cast material while keeping the roll flat against the patient. This is like unrolling carpet with the bulk of the padding away from the patient. Doing the reverse would necessitate shifting the roll more from hand to hand. This allows the pad to roll on straight and not under too much tension. 
  • PITFALL: Do not use too much padding, because this makes the cast loose.

  • PITFALL: Do not stretch the padding, because it will cause the padding and subsequent cast to be too tight.

  • PITFALL: Some extra padding should be applied over bony prominences to avoid injury under the cast. An extra roll over the ulnar styloid can avoid problems at this site.

Step 8

Place the plaster or fiberglass roll in lukewarm or room temperature water. For plaster, allow the plaster to sit in the water a few seconds, until the bubbling ceases. Remove the roll, and gently twist or gently squeeze the roll to remove excess water. Fiberglass can be applied without wetting if the clinician would like extra time for rolling it on or molding. The resin will react with ambient moisture in the air and harden in approximately 5 to 10 minutes. 
  • PITFALL: Never use hot water, which can cause an excess thermochemical reaction and extremely rapid setting of the cast material. The cast material should never be wrung out.

Step 9

Start rolling either proximally or distally. Apply the cast material with only mild tension, applying it in the same manner as the cast padding, from one end to the other and overlapping 50% of the prior turn. When applying plaster over tapered parts, tucks or pleats may be needed to avoid ridges or creases. After the cast tape is anchored at the wrist, cut the fiberglass three quarters of the way across the strip at the thumb and fold the free corners under. This allows coverage of the hand without constricting the thumb. Alternatively, the cast tape can be folded accordion style or twisted 360 degrees around its lengthwise axis at the thumb web space. These latter techniques may cause a thicker cast at the web space, which can cause more rubbing at the base of the thumb. 
  • PITFALL: Apply the cast material while keeping the roll flat against the patient. This is like unrolling carpet with the bulk of the cast roll in your palm away from the patient. Reversing this necessitates shifting the roll more from hand to hand and also tends to cause too much tension as the roll is unwound by pulling away from the patient.

Step 10

The stockinette and the underlying padding are folded over the edge of rolled cast material at the thumb, proximal, and distal aspects of the cast to form clean padded edges. 
  • PITFALL: If the cast material creates a sharp edge at the base of the thumb, trim the edge with bandage scissors or the cast saw.

Step 10
Step 10

Step 11

The folded-over stockinette is incorporated into the cast by rolling the casting tape back over the folded edge, either with the first roll or with a second roll if desired or if the arm is large and requires a second roll. For scaphoid fractures, the thumb is casted in a thumb extension (spica) position and the padding is folded back over the cast material to expose the distal aspect of the distal phalanx. 
  • PITFALL: The most common mistake made by novice physicians is to apply the cast to the metacarpophalangeal joints. All fingers need to be able to flex 90 degrees, and this means that the cast should end well short of the metacarpophalangeal joints.

Step 11
Step 11

Step 12

With wet gloved hands or using cast cream or hand lotion, smooth out any rough edges of the cast tape and mold the palm of the cast with an arm-wrestling-type handshake in a neutral position, unless a different position is required (i.e., for reduction of a Colles fracture). 
  • PITFALL: A poorly molded cast will not immobilize the area appropriately and can apply undue pressure at the wrong areas.

Step 12
Step 12

Step 13

Mold the forearm into a rounded off rectangular shape instead of leaving it as a circle. This will conform to the natural shape of the arm and also prevent rotation of the radius and ulna in the cast. 
  • PITFALL: Use broad surfaces of your hands to mold the cast. Do not use the fingertips to mold the cast because this can leave dents and pressure points to the underlying structures.

Step 13
Step 13

Step 14

Some clinicians recommend that being able to slip a finger under the edge of the cast is a guideline that the cast is not too tight. 
Give the patient adequate follow-up instructions and precautions. 
Step 14
Step 14

Step 15

Cast removal is performed with a vibrating cast saw. Although the serrated edge on the cast saw does not spin completely around, it can sometimes injure the skin beneath the cast if the padding is thin or the skin is fragile. The blade heats up as it vibrates through cast material. It gets warmer with thicker casts, fiberglass material, and if the practitioner cuts too slowly and stays in the same place too long. The cast saw should be used in an up-and-down motion (piston movement) going from one end of the cast to the other. Do not drag the saw linearly through the cast because this will cause more heat and risk to the underlying skin. Use the index finger or knuckle to stabilize the cast saw against the cast. The cast may be cut along the palmar and dorsal aspects. Alternatively, it can be cut along the ulnar side and may spread enough to slide over the thumb and off. If the arm cannot easily slip out of the cast, a second cut may be required down the radial side of the cast. 
Step 15
Step 15

Step 16

Spread the cast apart with cast spreaders. 
Step 16
Step 16

Step 17

Carefully cut the padding beneath the cast using cast scissors, avoiding injury to underlying skin, and then lift off the cast. 
Step 17
Step 17

Waterproof Short Arm Cast Using Cast Liner

Step 1
Fiberglass is waterproof, but standard stockinette and padding is not; they will hold moisture and should not be soaked with water. As an alternate option, synthetic stockinette and padding may be used in the same manner as outlined previously. Also, a waterproof cast liner made up of multiple square cushions is available, which can be applied under fiberglass casts. This liner allows individuals to bathe or swim with a short arm fiberglass cast. The waterproof cast liner replaces the stockinette and cast padding and is rolled directly on the skin with overlapping rolls. After swimming in chlorinated pools or salt water, the cast is rinsed, and it dries in 30 to 60 minutes. 
Step 2
Cut the cast liner with scissors to conform around the thumb. 
Step 3
Cut the cast liner two squares’ length from the end to form a padded edge to the cast before rolling the cast pad. 
Step 4
Place protective cutting strips along the anticipated lines where the cast will be cut off and allowing the colored edge to remain visible for cutting at the desired time. The fiberglass is then rolled on as described previously, incorporating the strips into the cast. 
Step 5
Cut the cast with the cast saw along the line of the protective strips, spread the cast with spreaders as before and use a scissors to cut the cast liner to remove. 
  • PITFALL: Cast liner is much easier to cut through than standard padding, causing burns and skin trauma. If a cutting strip was not placed, the manufacturer sells a flexible strip that can be slid under the cast and maneuvered under the path of the saw blade to protect the skin with cast removal.

Complications

  • Ischemia to the casted body part as a result of swelling of the extremity or the cast being applied to tightly

  • Pressure ulcers due to a poorly padded or poorly fitting cast, especially at bony prominences

  • Skin maceration if the cast gets wet and is not thoroughly dried out

  • Skin damage from the patient inserting foreign objects into the cast or attempting to modify the cast

  • Breakage of the cast as a result of misuse or inadequate structural strength as a result of inadequate overlapping of cast tape

  • Failure to immobilize the area as a result of a poorly fitting cast

Pediatric Considerations

  • Consider using a waterproof cast for ease of care and cleanliness.

  • Active children may be harder on a cast, requiring earlier replacement if worn or damaged.

  • Children are often frightened by the loud noise and vibration of the cast saw, so warning them and demonstrating against the practitioner’s palm that the saw is not intended to cut skin can be helpful.

Postprocedure Instructions

Advise the patient to elevate the arm as much as possible to avoid swelling on the first day of application. Additionally, if the cast becomes too tight, or if the patient has increasing pain in the arm, loss of sensation, or loss of circulation, or if a foreign body becomes lodged in the cast, the practitioner should not hesitate to remove the cast. After removing the cast, advise the patient to wash the area gently and not to aggressively scratch or abrade the area. 

Coding Information and Supply Sources

These codes are used only for cast or splint reapplications during a follow-up period. The initial casting or splinting is considered part of the fracture management code. If no management code is reported, the cast application can be reported at the initial service. A supply code (99070) may be reported in addition to the cast code to help defray the cost of materials (estimated at $12 to $20 for plaster casts, $20 to $50 for fiberglass casts). Insurances including Medicaid may not cover the cost of materials. 
The 2-, 3-, or 4-inch rolls of cotton or acrylic cast padding, cotton or acrylic stockinette, plaster bandages, and fiberglass cast tape can be ordered from these suppliers: 
Procel cast liner (formerly Gore cast liner) and De-flex Protective Strips can be ordered from 

Bibliography

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Killian JT, White S, Lenning L. Cast-saw burns: comparison of technique versus material versus saws. J Pediatr Orthop.  1999;19:683–687. [View Abstract]
Kowalski KL, Pitcher JD Jr. Evaluation of fiberglass versus plaster of Paris for immobilization of fractures of the arm and leg. Mil Med .  2002;167(8):657–661. [View Abstract]
Medley ES, Shirley SM, Brilliant HL. Fracture management by family physicians and guidelines for referral. J Fam Pract.  1979;8:701–710. [View Abstract]
Phillips TG, Reibach AM. Diagnosis and management of scaphoid fractures. Am Fam Physician .  2004;70:879–884. [View Abstract]
Shannon EG. Waterproof casts for immobilization of children’s fractures and sprains. J Pediatr Orthop .  2005;25(1):56–59. [View Abstract]
Spain D. Casting acute fractures, part 1: commonly asked questions. Aust Fam Physician.  2000;29:853–856. [View Abstract]
Webb GR, Galpin RD. Fractures in the distal third of the forearm in children—comparison of short and long arm plaster casts for displaced fractures in the distal third of the forearm in children. J. Bone Joint Surg Am .  2006;88:9–17. [View Abstract]
2008 MAG Mutual Healthcare Solutions, Inc.’s Physicians’ Fee and Coding Guide. Duluth, Georgia. MAG Mutual Healthcare Solutions, Inc. 2007.
 
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