Measurement of fracture movement in patients treated with unilateral external skeletal fixation

Axial movement occurring at the fracture site has been determined in a group of healing tibial fractures treated by external skeletal fixation. Fracture movement was determined via a strain gauge transducer which was attached to the column of the external fixator and measured the deflection of the bone screw adjacent to the fracture site and the active loading or weight bearing given by the patient to the fractured limb was monitored using a force platform. The results for 27 subjects show that, with a rigid unilateral fixator, the axial movement occurring at the fracture site was initially small (mean = 0.28 mm at 5 weeks post fracture). This movement increases to reach a mean maximum value of 0.43 mm at 11 weeks post-fracture and then decreases, despite increased weight bearing, as fracture healing progresses. In the early stages of healing, the movement can be increased slightly if the fixator is fitted with a module which permits additional fracture site movement, although the resultant increase in movement is only a small proportion of the potential available with this module.