THE DESIGN AND PERFORMANCE OF AN EXPERIMENTAL EXTERNAL FIXATION DEVICE WITH LOAD TRANSDUCERS

It is becoming increasingly common that fracture healing is modelled i n the laboratory with an osteotomy in the diaphysis of the ovine tibia . External fixation is often used to hold the bones in these models, p resenting the problem that the lands on such devices are poorly unders tood. To help investigate this, a unilateral device has been developed which is capable of measuring the two components of load considered t o be the most important, that of axial compression and bending in the plane of the fixator. The device was found to be a rigid system and ea sy to all,ly, with the in-vivo measurements being straightforward. The estimated limits of error of the compression transducer are +37.9 N a nd -21.4 N and those of the bending transducer are +3.6 Nm and -4.2 Nm . Preliminary measurements showed the maximum load during normal walki ng to 345 N compression and 28 Nm in-plane bending.