Office orthopedics: thumb spica casting for scaphoid fractures – includes patient information sheet

Office orthopedics: thumb spica casting for scaphoid fractures – includes patient information sheet – Cover Story

J. Randall Richard

Fracture of the scaphoid bone of the wrist is a common orthopedic problem and is accurately diagnosed by determining the mechanism of injury based on the history, performing specific physical examination maneuvers and interpreting radiographic findings. Skill in the application of the thumb spica cast enables the family physician to provide appropriate and definitive care for many of these patients.

The scaphoid is the most frequently fractured carpal bone. In one study,[1] scaphoid fractures were present in 33 (5.1 percent) of 641 patients who were evaluated for acute wrist trauma. Situated on the radial side of the wrist, the scaphoid mechanically links the proximal and distal rows of carpal bones and has strong ligamentous attachments both proximally and distally that limit motion (Figure 1). With forced hyperextension of the wrist, such as during a fall on an outstretched hand, the volarly directed tensile stresses on the relatively fixed scaphoid can result in a fracture.

Scaphoid fractures typically occur as a result of athletic or work-related injuries in men between 18 and 40 years of age. Interestingly, the same mechanism of injury in elderly persons (usually postmenopausal women) most often results in a distal radius (Colles’) fracture.

Clinical Evaluation

During the initial office visit, the patient presents with pain while trying to grip and dorsal radial wrist pain, especially during movement. Scaphoid fracture does not result in an obvious deformity of the wrist. The presence of a deformity and/or ecchymosis may indicate scapholunate fracture or dislocation. Localized tenderness in the anatomic snuffbox is the classic finding indicative of scaphoid fracture (Figure 2). Snuffbox tenderness may be more evident with the wrist in ulnar deviation. Also, tenderness may be present over the volar radial aspect of the wrist at the distal flexor crease, indicating the possibility of a fracture. This area, near the base of the first metacarpal, corresponds to the distal pole of the scaphoid.

Radiographs should include the posteroanterior and lateral views, as well as a special scaphoid view (anteroposterior view with 30 degrees supination and ulnar deviation) (Figure 3). A nondisplaced fracture may not be evident on initial films. If a scaphoid fracture is suspected clinically (i.e., based on the mechanism of injury an physical examination), the patient should be treated with thumb spica casting and radiographs should be repeated in approximately two weeks. A delay in diagnosis, even one or two weeks, increases the risk of nonunion.[2] If standard radiographs remain negative, but the suspicion for a fracture remains high, a bone scan or magnetic resonance imaging should be considered.

Illustrative Case

A 30-year-old man who played in a weekend football league fell on his outstretched hand and hyperextended his wrist. He felt a sudden pop accompanied by pain in the radial dorsal aspect of the wrist. Clinical examination revealed tenderness in the anatomic snuffbox. Radiographs revealed a fracture of the scaphoid. He was placed in a long-arm thumb spica cast for six weeks and then a short-arm thumb spica cast for two more weeks. Repeat radiographs revealed complete resolution of the fracture, and after a period of reconditioning, the patient returned to full activity without difficulties (Figure 4).

Fracture Classification

While several classification schemes have attempted to correlate location of scaphoid fracture with prognosis for healing,[3] the simplest classification scheme categorizes fractures as proximal, middle and distal third fractures (Figure 5). Location of the fracture has prognostic significance for healing time and the incidence of nonunion and avascular necrosis. Fracture location is important because branches of the radial artery, which supplies blood to the area, enter, in retrograde fashion, at or distal to the waist (mid-portion) of the scaphoid bone.[4]

Proximal third fractures are at greater risk for avascular necrosis and comprise approximately 15 percent of scaphoid fractures. Distal pole fractures account for 5 to 10 percent of scaphoid fractures, and midddle third or waist fractures account for 75 to 80 percent of fractures. Nondisplaced distal or middle third fractures heal, on average, in approximately eight to 10 weeks, but nondisplaced fractures of the proximal one-third require 12 weeks or more.[5(p640)]

Treatment

The use of long-arm versus short-arm thumb spica casts has been the subject of some debate. Gellman and colleaugues[6] reported a decreased healing time and reduced rates of delayed union and nonunion with long-arm casting. Other reports indicate an overall union rate of 95 percent with short-arm casting.[5(p642)] It is generally agreed that nondisplaced distal pole fractures are suitably treated with short-arm casting and that proximal pole fractures are best treated with long-arm casting for a longer duration. While the more common nondisplaced waist or middle third fractures may heal well with short-arm casting, these fractures are best treated using a long-arm thumb spica cast for six weeks, followed by a short-arm cast until complete radiographic union is confirmed (usually an additional two to four weeks).[7] The long-arm cast restricts pronation and supination of the forearm, preventing additional movement at the wrist.

Indications for Referral

Because of the risk of nonunion and subsequent avascular necrosis, persons with fractures of the proximal third should be referred to an orthopedist for definitive care. Patients with a displaced fracture (greater than a 1-mm gap) or a fracture with angulation should also be referred; such fractures may require specialized molding and/or positioning of the cast, percutaneous pinning, or open reduction and screw fixation.

Discussion with the patient about the overall 5 percent chance of delayed union or nonunion alerts the patient to possible complications.

Thumb Spica Casting Technique

For casting of the uncomplicated, nondisplaced scaphoid fracture, the wrist should be in the neutral flexion-extension and neutral radial-ulnar deviation position.[5(p642)] Although some clinicians prefer a thumb spica splint as initial management, we believe that the cast can generally be applied early, since subsequent increases in external swelling are uncommon.

The patient should be seated with the arm held horizontally. An assistant may be useful in stabilizing the patient’s arm or helping with the application of the cast. The best way to achieve the proper thumb and hand position for casting is to ask the patient to imagine that he or she is holding a small glass upright (Figure 6). The thumb should be in the neutral position with respect to abduction/adduction at the metacarpal phalangeal joint.

To allow full flexion of the second through fifth metacarpal phalangeal joints, the distal edge of the cast should be just proximal to the distal palmar crease. The thumb portion of the cast, in general, should extend to the middle of the distal phalanx, although some clinicians prefer to allow for full flexion of the interphalangeal joint. For scaphoid fractures, the proximal edge of the short-arm thumb spica cast is approximately three finger widths distal to the antecubital fossa. The proximal edge of the long-arm thumb spica cast should reach one-third to one-half of the way up the upper arm to prevent pronation/supination of the forearm.

Stockinette (3-in width for an average-sized adult man) is measured approximately 1 to 2 in beyond the intended proximal and distal edges of the cast, so that it can be back-folded after the initial fiberglass layers are laid down (Figure 7). An appropriately placed hole is cut for the thumb.

Next, 2-in cast wadding is unrolled, beginning with one layer around the wrist for anchoring. Usually two to three thicknesses are adequate. The distal edge of the wrapping should be along the distal palmar crease. After the thumb is wrapped, the wrapping should be continued up the arm to a point three finger widths from the antecubital fossa (Figure 8). For a long-arm cast, the wrapping should continue to approximately one-third to one-half of the way up the upper arm.

Usually two 2-in fiberglass casting tape rolls are adequate for a short-arm thumb spica cast. For a long-arm cast, one additional 3- or 4-in roll is necessary. The individual foil package should not be opened until ready to apply cause moisture in the air will activate the hardening process.

The roll is dipped into cold tap water, removed and shaken to remove excess water, with care taken not to misshape the roll by squeezing it. Fiberglass gives off considerably more heat compared with plaster, so it is important to use only cold water.

Beginning with one rotation around the wrist, the roll is brought distally toward the thumb. So that the fiberglass will lay flat, it is necessary to make small cuts in the fiberglass when wrapping around the thumb (Figure 9). With this first roll, two layers of fiberglass are sufficient. Next, the fiberglass is wrapped distally around the palm to within 0.5 cm to 1.0 cm of the edge of the wadding, with care taken not to roll the fiberglass beyond the edge (Figure 10). The fiberglass is continued up the forearm until a double layer of fiberglass has been rolled to within 0.5 cm to 1.0 cm of the proximal edge of the wadding near the antecubital fossa (for a short-arm cast), again with care taken not to go beyond the edge of the wadding (Figure 11).

The stockinette is folded back at both ends, and then the second roll is started at the proximal end of the cast, with the fiberglass tape edge carefully placed 0.5 cm from the reflected end of the stockinette (Figure 12). The fiberglass is rolled down the arm, adding approximately two layers of thickness, including the thumb, with cuts in the fiberglass made as before. The fiberglass is finally rolled to within 0.5 cm of the distal edge, with caution taken not to go beyond that point (Figures 13 and 14). For the long-arm cast, the proximal edge is midway up the upper arm, with the elbow in 90 degree flexion and the forearm in neutral position with respect to pronation and supination (Figure 15).

Once a roll of fiberglass is placed in water, it will become tacky in approximately two to three minutes. As it begins to harden, it becomes more difficult to unroll While the tendency may be to pull harder on the roll, this action increases the likelihood that the fiberglass will be wrapped too tightly Therefore, caution must be exercised when unrolling each fiberglass roll, especially at the end of the roll, to avoid making the cast too tight.

It is also common for the edges of the fiberglass not to lay completely flat when it has been rolled. This results in sharp, irregular edges on the cast when it has dried. Once the cast is rolled, any irregular edges can be smoothed down by rubbing moisturizing cream or water over the cast. My preference is to wrap a wet elastic bandage (which has been soaking in the water bath) tightly around the entire cast and leave it on for one to two minutes (Figure 16). This seals down any loose edges.

PATIENT INSTRUCTIONS

The patient should be given specific, preferably written, instructions for cast care, including symptoms that may indicate a problem. Increased swelling of the injured area after casting is not common. However, a cast that is applied too tightly can lead to a compartment syndrome, with the possibility f serious consequences. Key problem indicators are the development of increased wrist or thumb pain, paresthesias or swelling in the fingers that is not relieved immediately by elevation of the arm.

While the fiberglass cast does not disintegrate when it gets wet, moisture can cause skin maceration and breakdown. The patient should be instructed to use a plastic bag or wrap over the cast when bathing and, if the cast gets wet, to dry the inside by using a blow-dryer through the outside of the cast. A low power setting of the hair dryer should be used to prevent bums; drying may take an hour or more.

POST-CASTING CARE

The patient should return for a follow-up visit in one to two days to ensure that immobilization is adequate and that the cast is not too tight. Telephone follow-up would also be reasonable for some patients.

After the prescribed duration of casting, the cast is removed using a cast saw. It should be demonstrated to the patient that the cast saw cannot cut the skin. It is possible, however, to burn the patient with the heat generated from the friction of the vibrating saw, especially when cutting fiberglass. Periodically changing the cast saw blade will minimize the amount of frictional heat generated.

Repeat radiographs are obtained after cast removal to ensure fracture resolution. For scaphoid fractures, reapplication of casting for two to four weeks may be indicated if the fracture line remains visible. If the fracture line is still apparent after this additional period of casting, orthopedic consultation is appropriate.

The author thanks Jim Kennedy, M.D., and Vicki Hiner for their assistance in the preparation of this manuscript.

REFERENCES

[1.] Larsen CF, Brondum V, Wienholtz G, Abrahamsen J, Beyer J. An algorithm for acute wrist trauma. A systematic approach to diagnosis. J Hand Surg [Br] 1993;18:207-12. [2.] Cooney WP 3d, Linsheid RL, Dobyns JH. Fractures and dislocations of the wrist. In: Rockwood CA Jr, Green DP, Bucholz RW, eds. Fractures in adults. 3d ed. Philadelphia: Lippincott, 1991:638-9. [3.] Barton, NJ. Twenty questions about scaphoid fractures. J Hand Surg [Br] 1992;17:289-310. [4.] Taleisnik J. The wrist. New York: Churchill Livingstone, 1985:105-48. [5.] Cooney WP 3d, Linsheid RL, Dobyns JH. Fractures and dislocations of the wrist. In: Rockwood CA Jr, Green DP, Bucholz RW, eds. Fractures in adults. 3d ed. Philadelphia: Lippincott, 1991. [6.] Gellman H, Caputo RJ, Carter V, Aboulafia A, McKay M. Comparison of short and long thumbspica casts for non-displaced fractures of the carpal scaphoid. J Bone Joint Surg [Am] 1989;71:354-7. [7.] Kennedy JP. Wrist fractures and dislocations. In: Kennedy JP, Blaisdell FW, eds. Extremity trauma. New York: Thieme Medical, 1992:175.

J. RANDALL RICHARD, M.D. is associate director of the family practice residency program at Barberton (Ohio) Citizens Hospital and associate professor of clinical family medicine at Northeastern Ohio Universities College of Medicine, Rootstown. He earned a medical degree at the University of Cincinnati College of Medicine, and completed a family practice residency at St. Elizabeth Medical Center, Dayton, Ohio.

Address correspondence to J. Randall Richard, M.D., Family Practice Residency Program, 155 5th Street, N.E., Barberton, OH 44203.

COPYRIGHT 1995 American Academy of Family Physicians

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