Thumb Spica Splinting Technique

Updated: May 03, 2017
  • Author: Dinesh Patel, MD, FACS; Chief Editor: Erik D Schraga, MD  more...
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Technique

Application of Thumb Spica Splint

Explain the procedure to the patient, including risks and benefits. Obtain informed consent.

With the patient appropriately positioned (see Positioning), apply the stockinette. Cut longitudinally at the distal end of the stockinette to allow coverage of the thumb. When measuring the stockinette, allow for extra length. The stockinette should extend 2-3 cm beyond the overlying padding on either end. In turn, the padding will extend 2-3 cm beyond the overlying wet plaster on either end. Together, the stockinette and padding will be pulled over the edges of the wet plaster to create smooth edges. (See the video below.)

Thumb spica splinting: application of stockinette. Video courtesy of Kenneth R Chuang, MD.

Wrap the padding over the stockinette (see the video below). Overlap each layer by half the width. Also, allow for extra length. The padding should extend 2-3 cm beyond the overlying plaster on both ends. Smooth out creases, unwrapping and rewrapping as necessary. Apply extra padding to the bony prominences of the wrist and to the metacarpophalangeal (MCP) and interphalangeal (IP) joints of the thumb. (See the video below.)

Thumb spica splinting: application of cotton padding. Video courtesy of Kenneth R Chuang, MD.

Measure the dry plaster (see the video below). For an average-sized adult, plaster for the thumb spica splint should be eight to 10 layers thick. Use plaster that is 3-4 in. (7.5-10 cm) wide. After counting out the layers, measure the plaster from the level of the IP joint of the thumb to the proximal third of the forearm. Then, at the level of the MCP joint, cut a triangle 1.5 cm deep along both edges. Cutting the triangles keeps plaster from becoming too bulky when the thumb is abducted in the molding step. (See the video below.)

Thumb spica splinting: measurement of dry plaster. Video courtesy of Kenneth R Chuang, MD.

Allow for roughly 5 mm of extra length on either end; plaster shrinks when wet. Excess wet plaster, on the ends, will be folded over.

Next, submerge the plaster in clean, room-temperature water. Allow all the bubbles to escape. This starts the lamination process of the plaster and allows the layers to bond together. Squeeze out the excess water. With the fingers, strip out the remaining water. Then, lay the plaster on a flat surface or dry towel, and smooth out wrinkles and folds. This allows further bonding of the plaster layers. (See the video below.)

Thumb spica splinting: wetting of plaster. Video courtesy of Kenneth R Chuang, MD.

Apply the wet plaster, over the padding, to the lateral or radial surface of the forearm, extending along the length of the thumb to the IP joint. Fold the excess plaster outward on the ends. Then, fold the underlying stockinette and padding outward on both ends in such a way as to create smooth edges. (See the video below.)

Thumb spica splinting: application of wet plaster. Video courtesy of Kenneth R Chuang, MD.

Apply the bandage wrap over the wet plaster. Start distally, at the IP joint of the thumb, and wrap proximally. Avoid wrapping too tightly. (See the video below.)

Thumb spica splinting: application of bandage wrap. Video courtesy of Kenneth R Chuang, MD.

While the plaster is still wet, mold the splint into the desired shape. The wrist and hand should be in a neutral position. Extend the wrist to 20°, and abduct the thumb. To assist in achieving neutral position, ask the patient to imagine holding a wine glass, or hand the patient a bandage wrap to hold. (See the video below.)  If the wrist is immobilized straight or in flexion, a flexion contracture can develop because the wrist extensors may be unable to overcome potentially shortened wrist flexors.

Thumb spica splinting: molding of splint. Video courtesy of Kenneth R Chuang, MD.

The patient's hand, wrist, and forearm should remain immobile until the splint is dry. Advise the patient that he or she may feel some warmth released from the plaster as it dries. However, if the heat becomes too intense, unwrap the splint and remove the plaster immediately; thermal burns can occur.

Once the splint is dry, check for neurovascular function and capillary refill (see the video below). Keep in mind the areas innervated by the main sensory nerves in this area:

  • The median nerve provides sensory function to the palmar side of the thumb and second and third digits and the lateral half of the fourth digit and, dorsally, to the distal half of the second and third digits and the lateral half of the fourth digit
  • The ulnar nerve provides sensory function to the palmar and dorsal aspects of the fifth digit and the medial half of the fourth digit
  • The radial nerve provides sensory function to the dorsal surface of the hand and to the web space between the first and second digits
Thumb spica splinting: assessment of neurovascular function and capillary refill. Video courtesy of Kenneth R Chuang, MD.

Remember to check motor function as well. Wipe away any plaster that may have dropped onto the patient's skin.

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Postprocedural Care

Deliver appropriate aftercare instructions. Instruct the patient to rest, elevate, and ice the injured limb. Instruct the patient to remove the splint and return immediately or go to an emergency department if he or she experiences weakness or numbness, color change (pale or bluish), increasing pressure or pain, or spreading redness or streaking.

Keep the splint clean and dry. Do not stick any items into the splint. Patients can be tempted to use sticks, pens, or hangers to scratch an itch. Advise the patient that sticking objects into the splint can wrinkle the padding and lead to pressure sores or cause a break in the skin and lead to an unattended infection.

Arrange for follow-up with a consultant, usually in 2-7 days, depending on the reason for the splint.

If the patient received any sedation or opioids, advise against driving or alcohol consumption.

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Complications

Patients can typically expect to feel some warmth as the plaster dries. However, if intense heat or any pain is reported, the plaster should be removed immediately to prevent possible thermal burns. [5]  As more layers of plaster are used, more heat is produced. Use clean, room-temperature water. Water that is dirty or too warm accelerates the drying time and increases the heat produced. Do not wrap towels or blankets around the splint to shorten drying time; this produces excess heat.

To prevent pressure sores, provide extra padding to bony prominences. When wrapping the cotton padding, avoid creases. When creases occur, smooth them out, or unwrap and rewrap as needed. When molding the wet plaster, use broad-based pressure. In other words, do not use the fingertips; rather, use the entire palmar surface of the hands and fingers to mold the plaster.

Contact dermatitis may develop with thumb spica splinting. Consider prescribing an antihistamine (eg, diphenhydramine) for itching. However, if the itching persists or worsens, the splint should be evaluated for complications.

Increased pressure from swelling may give rise to ischemia and neurovascular compromise. If moderate-to-significant swelling is anticipated, cut the cotton padding lengthwise along the medial or ulnar side of the forearm before applying the wet plaster on the radial side. This allows for expansion of the padding. If using tape to secure the outermost bandage wrap, do not tape circumferentially.

Immobilization may result in decreased range of motion. Advise the patient that, depending on the extent and nature of the initial injury, he or she can often expect long-term pain, arthritis, stiffness, and decreased range of motion, despite best care practices. The aftercare of such injuries often requires physical therapy.

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