A Biomechanical Study of the Treatment of Tibial Fractures Using Plaster Casts

Abstract

The treatment of fractures of the tibial shaft by closed reduction and external fixation, usually employs plaster-of-Paris stabilization. This is effected by one of two techniques: the traditional toe to groin padded cast, which still enjoys widespread popularity and the Sarmiento patellar tendon bearing cast which offers excellent functional results. Some doubts have been expressed about the ability of the Sarmiento cast to provide sufficient stability for the fractured tibia and so the present study compares the stability of tibial fractures treated conventionally with those treated in a patellar tendon bearing cast. Experimental transverse fractures were produced in the tibia and fibula of seventeen above knee amputation specimens which were then subjected to bending and torsional loads. Each specimen was fractured through the mid-tibia and immobilized either in a conventional long leg cast moulded over two thicknesses of orthopaedic wool or in the Sarmiento moulded cast without padding. The immobilized leg was tested by supporting the leg at a fixed span and centrally loading the cast anteroposteriorly over the fracture site. A maximum bending moment of 50 Nm was applied. After clamping the upper femur, torsional moments were applied to the foot. After changing the type of plaster on the specimen the same experiments were repeated. Angulation and anteroposterior displacement was plotted against bending torque for both types of cast. The results showed that the Sarmiento cast provided stability at least equal to that of the conventional cast.