Abstract

A leg length inequality of 5 cm was compensated by lengthening of the proximal tibia by distraction epiphysiolysis. During the first 7 weeks of lengthening the distraction force was monitored continuously by strain gauges attached to the extension bars of the external distraction device. The increase in length was 1.25 mm a day. The force registration showed a visco-elastic response of the tissue to distraction. In the first week the distraction force increased up to 791 N. Then lysis occurred, followed by a sudden decrease in force to an average level of 150 N. During subsequent distraction, pain and clinical symptoms could be associated with increasing tension and inadequate stress relaxation of soft tissues. Adjusting the distraction rate decreased the build-up of force in the tissue and ameliorated the clinical symptoms. These results show that force measurements can be clinically useful for appropriately adjusting the distraction rate.