Atlas of Primary Care Procedures, 1st Edition

Musculoskeletal Procedures

67

The Short Arm Cast

Primary care physicians often have the opportunity to place casts. Patients with orthopedic injuries commonly present to primary care offices, and casting may be performed in the management of uncomplicated injuries splinted in the emergency department. Although most displaced fractures are managed with orthopedic consultation, primary care physicians manage many uncomplicated or nondisplaced fractures. Properly trained generalists may also perform reductions and some internal fixation procedures.

Historically, the treatment of musculoskeletal injury involved rest and immobilization of the injured part. Over the past several decades, studies have demonstrated that bones and soft tissues heal better with functional treatment, allowing normal movement while preventing abnormal movement. Osteoporosis of immobilized bone may be reduced or prevented by axial loading or stimulation of the fracture as healing occurs, and cartilage and ligaments heal better if allowed to move. The objective of early fracture management is immobilization of the fracture fragments with simultaneous axial loading and movement of nearby joints. Internal fixation accomplishes this goal, but the costs and risks of internal fixation may be unreasonable for some 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. Casts 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 it 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.

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 less than 6 months; the shelf-life can be extended by turning over the packages every few months to prevent drying. Two rolls of 4-inch plaster or two rolls of 2- or 3-inch fiberglass material are usually adequate for placement of a short arm cast.

P.533

One of the most common indications for placement of a short arm cast is to immobilize a suspected or occult scaphoid fracture or to treat a nondisplaced fracture. The potential harm and long-term consequences of a missed scaphoid (navicular) fracture are great. Initial radiographs often are negative for scaphoid fractures. Casting for 10 to 14 days allows adequate time for early callus formation, which can be seen on a follow-up radiograph. Documented fractures historically have been treated with short arm-thumb spica casts or long arm casts. New evidence suggests that simple short arm casts may provide better outcomes for nondisplaced scaphoid fractures.

PRIMARY CARE INDICATIONS FOR A GAUNTLET OR SHORT ARM CAST

  • 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)

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

Physicians would be wise to heed the 2001 guidelines for physiotherapists in Australia for the application and removal of casts (http://www.physioreg.heatlh.nsw.gov.au/hprb/physio_web/pdf/plaster.pdf).

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PROCEDURE

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 and hand involve placing the arm in a handshake position; pronate the wrist about 20 degrees, flex the wrist 20 to 30 degrees, and flex the metacarpophalangeal and phalangeal joints as if holding a 1- or 2-inch pole in the palm.

 

(1) When applying a cast, place the injured part in a position of function unless alternate positioning is required by the clinical situation.

P.535

 

A single layer of stockinette is applied. Cut the stockinette long enough so that it goes from the elbow to the distal interphalangeal joint of the third finger (Figure 2A). The extra length on each end helps to create smooth edges on the cast. Cut a hole for the thumb (Figure 2B).

 

(2) Apply a single layer of stockinette from the elbow to the distal interphalangeal joint of the third finger, and cut a hole for the thumb.

P.536

 

Apply the cast padding, beginning ½ inch inside one end of the stockinette and proceeding to within 1 inch of the other end (Figure 3A). The cast padding is applied to a double thickness by overlapping the roll 50% each turn (Figure 3B). Apply the padding and cast material with the thenar eminence, keeping the roll flat (like unrolling carpet) and not reversed to avoid dropping the roll during application (Figure 3C). Apply the padding halfway onto the thumb; the excess is folded back into the cast, providing padding at the base of the thumb.

 

(3) Apply the cast padding, beginning ½ inch inside one end of the stockinette and proceeding to within an inch of the other end.

PITFALL: Do not overpad, because this makes the cast loose.

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.

P.537

 

As an alternate option, a waterproof cast liner made up of multiple square cushions 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.

 

(4) A waterproof cast liner made up of multiple square cushions can be applied under fiberglass casts, which allows the patient to swim or bathe.

Place the plaster or fiberglass roll in lukewarm or room temperature water. 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.

 

(5) Place the plaster or fiberglass roll in lukewarm water, and allow it to sit for a few seconds until the bubbling ceases.

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.

P.538

 

Begin at the proximal end of the forearm, at least 2 inches from the elbow to avoid compromise of elbow flexion (Figure 6A). After the first circumferential roll around the forearm, fold back the excess stockinette and padding over the cast material. Reroll over this folded material, ½ inch from the edge of the folded padding, to create a smooth edge of cast material and soft edge of padding above the cast material (Figure 6B).

 

(6) Begin applying the fiberglass roll at the proximal end of the forearm at least 2 inches from the elbow to avoid compromise of elbow flexion.

P.539

 

Roll the cast material with moderate 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.

 

(7) Roll the cast material with moderate tension, applying it in the same manner as the cast padding, from one end to the other and overlapping 50% of the prior turn.

P.540

 

Apply the material to the level of the patient's mid-palm, over the proximal palmar crease. Fold back the stockinette and padding, and then reroll a smooth edge that angles across the palm. To allow movement of the fifth finger, the cast edge must angle downward across the palm, not straight across. Do not apply the cast material onto the thumb.

 

(8) Apply the material to the level of the patient's mid-palm over the proximal palmar crease.

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.

PITFALL: If the cast material creates a sharp edge at the base of the thumb, trim the edge with casting scissors or the cast saw.

P.541

 

While the plaster or fiberglass is setting, contour and mold the material with the palms of the hands (Figure 9A). After the material sets, make sure a finger can be inserted easily under the cast edge at each end (Figure 9B). Make sure the cast edge is padded at the base of the thumb. Give the patient adequate follow-up instructions (Table 67-1).

 

(9) Contour and mold the casting material with the palms of your hands while the plaster or fiberglass is setting, making sure that a finger can be easily inserted under each end of the cast.

TABLE 67-1. INSTRUCTIONS FOR CAST CARE

 

1. Elevate the cast for 24 to 48 hours to reduce swelling beneath the cast. Avoid grabbing or damaging the cast in the first 24 hours.

2. Watch for signs of swelling or problems beneath the cast. Pain is usually an early indication of a problem. To watch for circulation problems, examine the fingernails. If the nails appear pale or blue or fail to blanch (i.e., turn white and then pink after blood returns) when squeezed, call your physician.

3. Keep the cast dry if it is a plaster cast. If a waterproof cast liner is applied beneath a fiberglass cast, swimming or bathing is permitted. However, dry out the cast (i.e., use a blow drier set on cool or low, directed beneath each end) soon after to prevent skin trauma or maceration.

4. Do not place anything inside the cast. Many individuals incorrectly try to relieve itching with pencils, pens, coat hangers, or kitchen utensils. Blow warm air with a hairdryer, apply an ice pack, or take Benadryl (25 mg) to help alleviate itching.

5. Do not damage the cast, cut into the cast, or modify the cast. If the cast inadvertently breaks or becomes too loose, report right away to your physician for cast repair.

 

P.542

 

Cast removal is performed with a vibrating cast saw. The serrated edge on the cast saw (Figure 10A) can injure the skin beneath the cast or burn the patient. The blade heats up as it vibrates through cast material; it gets warmer with thicker casts or fiberglass material. The cast saw cuts by up-and-down motion as it moves from one end of the cast to the other (Figure 10B). Make a cut along the ulnar side of the cast; enlarge the opening with a cast spreader (Figure 10C). Carefully cut the padding beneath the cast using cast scissors, avoiding injury to underlying skin. (Figure 10D). If the arm cannot easily slip out of the cast, a second cut may be required down the radial side of the cast.

 

(10) Removal of the cast is accomplished by using a vibrating cast saw.

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CODING INFORMATION

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). Insurance such as Medicaid may not cover the cost of materials.

CPT® Code

Description

2002 Average 50th Percentile Fee

29075

Short arm cast (elbow to finger)

$135

29085

Gauntlet cast (hand and lower forearm)

$128

CPT® is a trademark of the American Medical Association.

INSTRUMENT AND MATERIALS ORDERING

The 2-, 3-, or 4-inch rolls of cotton or acrylic cast padding, cotton or acrylic stockinet, plaster bandages, and fiberglass cast tape can be ordered from DePuy OrthoTech, Tracy, CA (http://www.depuy.com); Ray-Tek Inc. fracture management supplies (http://www.ray-tek.com); and 3M Health Care, St. Paul, MN (phone: 800-228-3957; http://www.3M.com/healthcare). Cast removal tools such as scissors, cast spreaders, and Stryker cast saws can be obtained from Applies Medical Service, Inc, Knoxville, TN (http://www.appliedmedicalinc.com). Procell cast liner (formerly Gore cast liner) is a waterproof, breathable, quilted cast padding that allows individuals to bathe and swim while the fracture heals. De-flex Protective Strip is a cut-resistant removal aid that provides protection from the cuts and burns from cast saws. It can be ordered from W.L. Gore & Associates, Flagstaff, AZ (phone: 800-248-8489; http://www.goremedical.com).

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Burge P. Closed case treatment of scaphoid fractures. Hand Clin 2001;17:541–552.

Byl NN, Kohlhase W, Engel G. Functional limitation immediately after cast immobilization and closed reduction of distal radius fractures: preliminary report. J Hand Ther 1999;12:201–211.

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Lewis DM, Osterman AL. Scapholunate instability in athletes. Clin Sports Med 2001;20:131–140.

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Mercier LR, Pettid FJ, Tamisiea DF, et al. Practical orthopedics, 4th ed. St. Louis: Mosby, 1995:14–19.

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