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Properties of a hybrid plaster-fibreglass cast
1Department of Surgery, Queen's University, Kingston, Ont.
Objective:
To examine the suitability of a plaster-fibreglass hybrid cast for orthopedic applications, comparing them to plaster of Paris (POP) and fibreglass constructs.
Method:
Groups of 10 standardized hybrid, POP and fibreglass casts were studied. An Instron servohydraulic system was used to test the casts in 3-point bending and shear.
Outcome Measures:
Strength, stiffness, weight, thickness and cost of the 3 types of cast, and shear strength at the interface between the POP and fibreglass in the hybrid casts.
Results:
The hybrid casts were twice as strong as the POP constructs, were stiffer and weighed 14% less but were thicker and cost 2.5 times more. They were almost as strong as and less than half the cost of the fibreglass constructs but were thicker, not as stiff, and weighed 42% more. The shear strength of the POP-fibreglass interface in the hybrid casts was higher than the 3-point bending strength of this construct by a factor of 3.
Conclusions:
Plaster-fibreglass hybrid casts should be considered for orthopedic use on the basis of their strength, stiffness, weight and cost, combined with their acknowledged advantages of good moulding ability and water resistance.