Intramedullary nail distal hole axis estimation using blob analysis and hough transform

In a closed intramedullary nailing of femoral surgery, one of the most difficult task for surgeons is to identify the position and orientation of the screwing holes at both ends of the intramedullary nail (IMN) after being inserted into a patient's femoral canal. The distal hole location may be shifted by external forces and torques applied to the IMN during the insertion procedure resulting in the IMN to deform. To recover the position and orientation (or "pose") of the screwing holes in the conventional operation, surgeons require high degree of experience, and a number of trial-and-error adjustments to correct the path for inserting the screws. Both surgeon and patient are also continuously exposed to a great amount of X-ray exposure from the fluoroscopic imaging system. This paper discusses a necessary part of a surgical navigation research for assisting orthopedic surgeons. This work addresses a problem of estimating the intramedullary nail (IMN) distal hole axis from a 2-D image taken from the fluoroscopic imaging system. The proposed approach is based on the geometric properties of the nail itself. The Hough transform and Blob analysis were employed as main image processing tools. The preliminary results show that the proposed method performed satisfactorily. However, there are several limitations associated with this approach. In particular, the proposed method cannot differentiate estimated distal hole angles in the first quadrant from the second quadrant.