A Biomechanical Evaluation of Casting Technique and Cast Core Size Effect

Area of Science:

• Orthopedic biomechanics
• Materials science in medicine

Background:

• Casting techniques and materials significantly influence orthopedic cast biomechanical function.
• Understanding the relationship between cast dimensions, layers, and strength is vital for clinical application.

Purpose of the Study:

• To compare the biomechanical function of casts made with different materials (fiberglass, Plaster of Paris) and core diameters.
• To evaluate the impact of casting techniques (smoothing vs. non-smoothing) on cast strength.
• To determine the relationship between the number of cast layers and core diameter on overall cast strength.

Main Methods:

• Two standardized cast models (60mm and 100mm core diameter) simulated forearm and short leg casts.
• Casts were constructed using fiberglass (2-4 layers) and Plaster of Paris (3-5 layers) with and without a smoothing/lamination technique.
• Cyclic 4-point bend testing assessed ultimate load-to-failure and flexural rigidity.

Main Results:

• Increased cast thickness (more layers) significantly enhanced ultimate load-to-failure and bending strength.
• Larger core diameters (100mm vs. 60mm) significantly reduced cast strength for both fiberglass and POP materials.
• The smoothing and lamination technique negatively impacted POP casts and had minimal effect on fiberglass casts.

Conclusions:

• Optimal cast layering should be adapted to the size of the extremity being immobilized.
• The smoothing and lamination casting technique does not significantly improve the mechanical behavior of orthopedic casts.
• Findings guide physicians in selecting appropriate casting materials, techniques, and layer numbers for improved patient outcomes.