Abstract
The segmental bone transport allows the reconstruction of large scale bone defects resulting after a redical debridement due to an infection or after trauma. We use the Ilizarov fixator for the segmental transport. The part of the bone that has to be moved through the defect is pulled by a lateral and a medial towing rope. To determine continuously the forces of tension in the wires and to detect early complications of the bone transport we implanted in each wire a load cell with a resistance strain gauge. The knowledge of the resulting forces leads to the development of an automatic forced controlled bone transport.
Since 09/2004 we have measured the forces of tension in the wires in 77 patients undergoing a segmental bone transport due to a long-extending osteomyelitis. The average age was 47,2 (6 to 68). In 12 patients we had to treat a bone defect of the thigh (average size of the defect 12,5 cm), in 55 patients 56 large scale bone defects of the lower leg (average size of the defect: 8,6 cm ranging from 6,0 to 20,0 cm). We implanted a load cell with a resistance strain gauge in the lateral and medial towing rope. This way we could, after converting the measured values from analog to digital, the impacting forces.
In all patients we were able to meausure continuously rising forces of tension. Lwe noticed forces which didn´t change much. At the end the bone transport we again found rising forces of tension. We noticed higher forces in the lateral wires, on femur and on tibia. Due to the measurement of the acting forces we were abel to perform a bone transport without close X-ray-monitoring. Complications such as premature ossification of the new building bone were identified and treated in an early stage.at
We developed a theoretical model drawing into consideration the interfering forces caused by the regenerating bone, the soft tissue, the friction of the wire, adherend soft tissue and geometry otf the wire. The forces calculated using this model were similar to the acting forces we found when measuring the forces of the bone transport. We now record the data on memory cards. A control of the data is possible over long-distance. We now started a model of an automatic bone transport controlled by the the acting forces. Our aim is to perform such an automatic bone transport in patients.
