Volumetric Considerations for Valving Long-Arm Casts: The Utility of the Cast Spacer

Fiberglass casts are frequently valved to accommodate swelling following injury or surgery. The use of cast spacers has been recommended to bridge this gap between pressure reduction and cast strength, but no studies have assessed their effect on cast pressure. We applied 30 long-arm fiberglass casts to adult volunteers, divided between a univalve group and a bivalve group. A pediatric blood pressure bladder was applied under the cast to simulate soft tissue swelling. Valved casts were secured using an elastic wrap, 10-mm cast spacer, or 15-mm cast spacer. Measurements of cast pressure and circumference were performed at each stage and compared on the basis of type of valve and securement. Our results indicated that cast univalving resulted in an approximately 60% reduction in cast pressures, with a 75% reduction seen in the bivalve group. The addition of cast spacers resulted in significant pressure reductions for both valving groups. The univalve group secured with a 10-mm cast spacer produced reductions in cast pressure similar to those of the elastic-wrapped bivalve cast, both with the cast padding intact and with it released. The use of cast spacers results in significant cast pressure reductions, regardless of valving technique. A univalved cast secured with a cast spacer can produce decreases in cast pressures similar to those seen with an elastic-wrapped bivalved cast, and it is a viable option for reducing cast pressure without compromising cast structural integrity with a bivalve technique.