Determination of stresses in below-knee walking casts

Glass fibre bandages are now commonly used for definitive below-knee walking casts, in preference to plaster of Paris, since they are better able to withstand the stresses imposed upon them. This paper describes a technique for recording the cast strains in glass fibre bandages and shows typical stress levels in patient and volunteer casts. A typical map of the stress variations in walking casts during gait in a volunteer has been produced. The study shows that the high stresses recorded along the medial and lateral borders of the foot by the strain gauge technique are confirmed by clinical experience, since this is where failure is most commonly seen in below-knee walking casts. It is concluded that the current generation of polyurethane impregnated glass fibre splinting bandages are too brittle in many cases for below-knee walking casts and that a more flexible fabric would reduce the incidence of cast breakdown.