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[CLINICAL TECHNIQUES]

Applying the Munster Cast

Optimal Motion Control for Scaphoid Fractures

Elizabeth A. Joy, MD

William O. Roberts, MD, Department Editor

THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 6 - JUNE 1999


The scaphoid is the most frequently fractured carpal bone, with fractures of the middle third accounting for 80% of all scaphoid fractures (1-3). These fractures are commonly treated with a thumb spica, long arm cast that immobilizes both the wrist and the elbow. This type of cast is cumbersome and creates economic hardship for some patients.

However, an acute, nondisplaced fracture of the scaphoid waist or proximal scaphoid (figure 1) can also be treated with a Munster cast, a modified thumb spica, long arm cast that prevents supination and pronation of the wrist and forearm while allowing some elbow flexion and extension (4). The Munster cast is relatively easy to apply. It provides adequate immobilization, and it makes immobilization much more tolerable for patients.

[Figure 1]

Troublesome Fractures

Given the blood supply to the scaphoid bone, difficulties in radiography, and delays in diagnosis, scaphoid fractures have a relatively high rate of nonunion (8% to 10 %) (1-3,5). Nonunion occurs in 20% to 30% of proximal third fractures and 10% to 20% of middle third (waist) fractures, but it is rare in distal fractures (1).

Several possible features in scaphoid fractures contraindicate cast immobilization and should prompt referral to an orthopedic surgeon for further evaluation and treatment. These include displacement of the fracture fragments by more than 1 mm, angulation, comminution, delay of diagnosis by more than 1 month, inadequate initial immobilization leading to delayed union or nonunion, scapholunate dissociation, and perilunate dislocation (1,3,6).

Although there is considerable controversy regarding the management of scaphoid fractures, a number of authorities support the use of long arm casts in the initial treatment of nondisplaced waist and proximal third fractures of the scaphoid (1-3,5-7). Both cadaveric and clinical studies have demonstrated improved outcomes when forearm rotation is restricted (8,9). The Munster cast is an attractive option because it effectively restricts forearm rotation while allowing a functional range of elbow motion.

Initial Steps

Upper-extremity position. The initial steps of applying a Munster cast are similar to those for a standard long arm cast with a thumb spica. The patient should be seated with his or her arm held in front of the body. An assistant can hold the patient's hand in the proper position to facilitate cast application. To treat a scaphoid fracture, the elbow should be bent 90°, with the forearm in neutral supination-pronation, the wrist in neutral flexion-extension, and the thumb slightly extended and abducted (1-3,6).

Stockinette. Stockinette—2-in. for a woman or 3-in. for a man—is measured from the proximal interphalangeal joints to the deltoid insertion. Remember to measure twice, and cut once! Cut a hole for the thumb placement (figure 2).

[Figure 2]

Padding. Next, cast padding is applied by overlapping each width by half so the extremity is covered with two layers (figure 3). Using 2-in. padding, begin from the midpoint between the deltoid insertion and the elbow joint and proceed distally to just past the patient's metacarpophalangeal (MCP) joints. Use a second roll of 1-in. material to pad the thumb.

[Figure 3]

Take care to pad bony prominences adequately, including the medial and lateral epicondyles, the olecranon, the distal ulna, and the radial styloid. However, do not apply too much to the wrist area, since overpadding can prevent adequate cast molding and immobilization of the fracture.

Fiberglass Application

At least three rolls of 2-in. fiberglass casting tape are usually necessary for a Munster cast. After dipping the casting tape in cold water, gently squeeze out any excess.

Forearm to hand. Start at the midpoint of the forearm and wrap distally, overlapping each width of tape by half. The cast tape should be layered on without tension so that it won't be too snug around the wrist or forearm.

When casting the hand and thumb, cut the cast tape about half way through its width to avoid excess in the thenar web space. Fold the stockinette back over the padding on the hand, and secure it with casting tape. This portion of the cast should now end at a point just proximal to the MCP joints (the distal palmar crease), allowing full flexion of the fingers.

It is very important that the hand and wrist portion of the cast be well molded to maintain optimal alignment of the fracture fragments. Molding is done by grasping the thumb, hand, and wrist and applying moderate pressure to configure the cast to the desired shape (figure 4).

[Figure 4]

Wrist to elbow. Using a second roll of casting tape, start at the wrist, and, overlapping the tape again by half its width, layer proximally to about 2 to 3 in. past the epicondyles of the humerus. The cast material should be well molded about the epicondyles (figure 5) to optimize the cast's ability to prevent rotation of the forearm.

[Figure 5]

While applying the tape, remember to continually reevaluate the position of the thumb, wrist, and elbow, as they have a tendency to move from their initial position. Fiberglass casting material hardens quickly (within 3 minutes), allowing little time to make adjustments once the cast is applied.

While the proximal end of the cast is still slightly wet, locate the epicondyles and mark the cast with a pen about one thumb-breadth above each epicondyle and above the olecranon (figure 6a). Draw a line from the antecubital fossa connecting each of the marked areas and back to the antecubital fossa. Using the cast saw, cut along this line (figure 6b), taking care to avoid cutting through the cast padding and the stockinette. Remove the superior portion of the cast, and fold down the remaining padding and stockinette over the proximal end of the cast.

[Figure 6]

Finishing. Using the third roll of cast tape, secure the proximal end of the stockinette, and continue applying the tape down the forearm to the wrist until two layers are applied (figure 7).

[Figure 7]

Immobilization Time

For the nondisplaced waist or proximal fracture of the scaphoid, the Munster cast is left in place for 6 weeks. If the wrist is moderately swollen when the cast is initially applied, recasting after 2 weeks should be considered to ensure proper immobilization.

Six weeks after the cast is applied, it should be removed and radiographs should be obtained. If radiographic healing is confirmed, no further immobilization is necessary. However, if the patient's healing is inadequate, a short arm cast with a thumb spica should be placed for another 4 to 6 weeks, until bony union is certain (3,6,7).

Patient Information

Patients should be given appropriate cast-care instructions and information regarding potential problems before leaving the office. Swelling or paresthesias of the hand, bluish discoloration of the fingers, or increasing pain at the fracture site may indicate an overly tight cast, which requires splitting or reapplication. While the fiberglass material is generally water-resistant, a shower or bath taken without protecting the cast will soak the padding. This can lead to maceration of the skin under the cast and subsequent local infection, so patients should avoid getting the cast wet.

References

  1. Eiff MP, Calmbach WL, Hatch R, et al: Carpal fractures, in Eiff MP, Hatch RL, Calmbach WL: Fracture Management for Primary Care. Philadelphia, WB Saunders, 1998, pp 65-71
  2. Richard JR: Office orthopedics: thumb spica casting for scaphoid fractures. Am Fam Phys 1995;52(4):1113-1120
  3. Rockwood CA, Green DP, Bucholz RW (eds): Rockwood and Green's Fractures in Adults, ed 3. Philadelphia, Lippincott, 1991, pp 638-647
  4. Blauvelt CT, Nelson FRT: A Manual of Orthopedic Terminology, ed 6. St Louis, Mosby, 1998, p 158
  5. Gustilo RB, Kyle RF, Templeman DC: Fractures and Dislocations. St Louis, Mosby, 1993, pp 585-591, vol 1
  6. Ruby LK: Fractures and dislocations of the carpus, in Browner BD (ed): Skeletal Trauma: Fractures, Dislocations, Ligamentous Injuries, ed 2. Philadelphia, WB Saunders, 1998, pp 1025-1028
  7. Markiewitz AD, Ruby LK, O'Brien ET: Carpal fractures and dislocations, in Lichtman DM, Alexander AH (eds): The Wrist and Its Disorders, ed 2. Philadelphia, WB Saunders, 1997, pp 189-194
  8. Gellman H, Caputo RJ, Carter V, et al: Comparison of short and long thumb-spica casts for non-displaced fractures of the carpal scaphoid. J Bone Joint Surg (Am) 1989;71(3):354-357
  9. Thomaidis BT: Elbow-wrist-thumb immobilization in the treatment of fractures of the carpal scaphoid. Acta Orthop Scand 1973;44(6):679-689

Dr Joy is an assistant professor in the department of family and preventive medicine and a team physician at the University of Utah in Salt Lake City. Dr Roberts is a family physician at MinnHealth SportsCare in White Bear Lake, Minnesota, and medical director of the Twin Cities Marathon. Both are fellows of the American College of Sports Medicine, and Dr Roberts is an editorial board member of The Physician and Sportsmedicine.


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