Spotlight on Casting | Surmounting Common Casting Problems

 In this new series, we look at arguably the most crucial factor in the success of a custom DAFO: the cast. Look for more on casting in future issues of Dafo Dynamics.

Many of the most common problems we see in casts that arrive in the Cascade Dafo lab are easy to avoid. Here’s a look at them, a hint of what we need to do to correct casts, and tips for avoiding these problems.

Note—after a cast is corrected, it is filled and further refined to provide a smooth finish, highlight contours of prominences and build up or remove as indicated by your instructions.

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Rubbery Cast

The cast was created using 3M® Scotchcast® Soft Cast Casting Tape. The cast is exceedingly flexible and thus won’t hold its shape when we create the positive from which the brace is built (Fig. 1, top). For these casts, we need to essentially re-create the cast by using our fiberglass tape over top of it.

Key— We recommend fiberglass casting tape. We use Royce Medical Techform® Ortho-Roll. However, 3M Scotchcast Plus Casting Tape or Caraglass Synthetic Casting Tape (by Kingsley O&P Supply) are similar.

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Poor Wrap Coverage

The casting tape has loose areas or gaps in coverage (Fig. 1, bottom).

Key— Overlap each previous layer of tape by about 50 percent, and apply moderate tension by pulling gently and evenly on the tape. Be sure to maintain an overlap of tape, especially over the heel. (Look for more on good casting technique in the next issue of Dafo Dynamics.)

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Ambiguous Foot Position

The patient’s foot has been cast in a position that conflicts with the instructions on the order form; or there is poor definition of foot contours (Fig. 2).

Key— Before you cast, rehearse holding the foot in correction. Take note of your handhold and the amount of pressure you apply. Then use this handhold when waiting for the casting tape to set up. Use the casting footplates when appropriate. If the cast you create doesn’t reflect the patient’s best position of function, it’s always a good idea to cast again.

As a final check, compare your cast to the instructions you put on the order. Make sure the two are compatible.

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Packed Loosely

Because of extra space in the shipping box, the box has collapsed, the tape comes loose and the cast is damaged (Fig. 3).

Key— If you use plaster, make sure it is completely dry before packing it, and wrap your cast securely in bubble wrap. Always fill up the rest of the box with Styrofoam peanuts or other space-taking packing material. Fill the box right up to its capacity. This way, the box will hold its shape. (Shipping boxes are often stacked in transit.) Tape the box securely, using at least two pieces of tape across the main opening.

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Wet Plaster Cast

Our preferred casting material is fiberglass (though plaster, done well, is also suitable). If you send wet or damaged plaster (Fig. 4), we must essentially re-create the cast by using our fiberglass tape over top of it.

Key— If you do send plaster, please be sure it is fully dry and cured (and well-packed) before shipping it.

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Short Cast Length or Height

The cast doesn’t cover enough, either in toe length or in posterior height, to define the brace (Fig. 5).

Key—Consider how high you want the final brace. Cast up at least that far. Also, be sure you cast all the way past the distal end to cover every toe. Don’t leave any toes out.

Fig. 1. A cast showing both the rubbery nature of Scotchcast Soft Cast casting tape and a gap in heel coverage. We wrap the cast with fiberglass to stabilize shape, but this may alter contours from their original form. Fig. 2. Casts with incorrect ankle alignment and poor definition. Left, the casts as they arrived, clearly in extreme PF with very little definition around boney prominences. Right, the casts with angle corrected based on order form instructions: really no information to go on for ankle or heel definition. These very features are extremely important for good fit and comfort. Fig. 3. A partly-empty box, collapsed in shipment. Fig. 4. Top, the plaster casts as they arrived, swollen and distorted. Just above, the corrected casts waiting to be filled and modified. Fig. 5. Rough, corrected mold from a cast; the original cast had cut off the toes, the DF angle required correction and the surface anatomy was not well defined. The resulting positive mold will require quite a bit of guesswork on the part of our modifiers in order to create a precise fit.