• Steven B Daines, David D Aronsson, Bruce D Beynnon, Daniel R Sturnick, Jennifer W Lisle, and Shelly Naud.
• Departments of *Orthopaedics & Rehabilitation †Medical Biostatistics, University of Vermont College of Medicine, Burlington, VT.
• J Pediatr Orthop. 2014 Oct 1; 34 (7): 743-8.

BackgroundCasts are used to treat clubfeet, developmental dysplasia of the hip (DDH), forearm fractures, and femur fractures. The ability of a cast to maintain a desired shape is termed moldability. Clinicians use plaster, fiberglass, and soft casts. To our knowledge the biomechanical molding characteristics of these 3 materials have never been reported. We hypothesized that moldability of plaster would be better than fiberglass and fiberglass would be better than soft cast.MethodsWe compared 12.7 cm wide casts of plaster, fiberglass, and soft cast. Casts were 5 layers thick, prepared in 40°C water, and placed over 2 layers of cotton padding on 5.1 cm and 15.2 cm diameter foam cylinders. A loading device simulated loads applied by clinicians when molding casts for 4 conditions: clubfoot (thumb-shaped 50 N load on 5.1 cm model), DDH (thumb-shaped 100 N load on 15.2 cm model), forearm fracture (palm-shaped 50 N load on 5.1 cm model), and femur fracture (palm-shaped 100 N load on 15.2 cm model). The loading device applied molding for 7 minutes. Five casts of each material were made for each model. Casts were removed, photographed, and the area of maximal deformation was compared with an unmolded cast. A large area of maximal deformation meant that the deformation was spread out over a large area, less precise molding.ResultsIn the clubfoot model, plaster was more precise than fiberglass (P=0.002) and soft cast (P<0.0001). In the DDH model, plaster was more precise than fiberglass (P<0.0001) and soft cast (P<0.0001) and fiberglass was more precise than soft cast (P<0.0001).In the femur fracture model, plaster was more precise than fiberglass (P=0.001) and soft cast (P=0.001).ConclusionsThe moldability of plaster is better than fiberglass and soft cast and fiberglass is better than soft cast.Clinical RelevanceIf precise molding is required, plaster has the best moldability. In cases not requiring precise molding, fiberglass and soft cast are lightweight, waterproof, and available in child-friendly colors.

13 keywords...

hide…