Which displaced spiral tibial shaft fractures can be managed conservatively?

The aim of the present study was to establish a threshold for the initial d isplacement of a spiral tibial shaft fracture beyond which its retention in an acceptable position cannot be guaranteed by plaster immobilization. We reviewed the records and radiographs of 131 plaster cast-treated patients w ith spiral tibial shaft fracture, initially displaced 50% or less, for pati ents whose fracture had either lost its acceptable retention or consolidate d in an unacceptable position. The fractures were classified, according to the true initial displacement as measured on the first radiographs, into fo ur pairs of categories using cut-off points of 10, 20, 30 and 40% of the di ameter of the tibial diaphysis. Comparison was then made of the proportions of failed treatments between each of these pairs. Plaster cast treatments failed in 28% when the true initial displacement was 30% or less, and in 46 % when the true initial displacement was more than 30%. The risk of failed plaster cast treatment increased when true initial displacement exceeded 30 %. In all patients whose plaster cast treatment was interrupted the true in itial displacement was more than 30%. We therefore conclude that diaphyseal fractures of the tibia for which the initial displacement exceeds 30% are not suitable for plaster cast treatment.