Automated determination method of tibial bone coordinate system for analysing bone tunnel trans-position after anterior cruciate ligament reconstruction from a knee MDCT image

The anterior cruciate ligament (ACL) plays important role as a preventing excessive anterior movement of the knee. When the ACL is injured, ACL reconstruction is often performed. In ACL reconstruction, bone tunnels of the femur and tibia are made for passing graft to the bone. It is reported that the bone tunnel is usually enlargement. The bone tunnel enlargement affects much knee function. In serious case, ACL reconstruction should be required again. Therefore evaluation of the bone tunnel is important. It has been analyzed for only calculation of volume change in time course. However, the direction of the volume change has not been considered, due to the difference of bone coordinate systems between data. This study proposes determination method of the bone coordinate system with fuzzy inference. As a result, our proposed method could determine the tibial bone coordinate system. Then, the bone tunnel trans-position was examined. A future work is to apply this method to more data, then feed back the clinical outcome.