Comparison of biomechanical behavior between a cast material torso jacket and a polyethylene based jacket

Area of Science:

• Orthopedics
• Biomechanical Engineering
• Materials Science

Background:

• Early Onset Scoliosis (EOS) treatment involves various designs, including Thoraco-Lumbo-Sacral Orthoses (TLSO) made of Polyethylene (PE).
• Casting materials offer advantages like growth preservation, improved compliance, and reduced invasiveness compared to PE TLSOs.
• The comparative mechanical effectiveness of cast material braces versus traditional PE TLSOs for EOS remains largely unquantified.

Purpose of the Study:

• To biomechanically compare the mechanical effectiveness of cast material braces with traditional Polyethylene (PE) Thoraco-Lumbo-Sacral Orthoses (TLSO) for Early Onset Scoliosis (EOS).

Main Methods:

• Standardized tensile tests were conducted to determine mechanical properties of cast materials (Delta-Cast Soft®) and PE.
• A finite element spine model was created using patient-specific radiographic measurements.
• Simulations applied established mechanical loads to finite element models of both TLSO and cast jacket designs, varying material thicknesses and layers.

Main Results:

• A 6.6mm cast jacket exhibited a maximum deformation of 4.7mm and stress of 2.9MPa, with a safety factor of 5.71.
• A 4mm PE jacket showed a maximum deformation of 2mm and stress of 8.9MPa, with a safety factor of 2.70.
• The cast jacket was 3.5 times lighter and had a material cost 1/5th that of the PE brace.

Conclusions:

• Both TLSO and cast designs provide adequate spinal constraint forces for scoliosis correction.
• Cast material braces, despite being slightly thicker, demonstrate superior structural integrity and cost-effectiveness.
• From a biomechanical perspective, cast braces are more efficient for Early Onset Scoliosis treatment compared to PE TLSOs.