ABSTRACT
In intramedullary nail (IMN) surgical operations, one of the main efforts for surgeons is to find the axes of two distal holes. Two distal holes on an IMN, which are inside the intramedullary canal of a patient's femur, can only be seen in a lateral X-ray view. For the standard surgical procedure, the localization of the distal hole axes is a trial-and-error process which results in a long surgical time and large dose of X-ray exposure. In this paper, an algorithm to derive the three-dimensional position and orientation of the distal hole axis was developed. The algorithm first derives the nail axis through two X-ray images. Then the distal hole axis is calculated through projecting back the hole boundary on the X-ray image from a lateral view to three-dimensional space. A least-squares method is used to determine the centres of the front hole and the back hole through iteration. The algorithm has been tested with real data and it was robust.
Subject(s)
Bone Nails , Fracture Fixation, Intramedullary/methods , Imaging, Three-Dimensional , Models, Theoretical , Prosthesis Implantation/methods , Radiographic Image Enhancement/methods , Computer Simulation , Femoral Fractures/diagnostic imaging , Femoral Fractures/surgery , Humans , Imaging, Three-Dimensional/instrumentation , Phantoms, Imaging , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Accurate characterisation of the image distortion within a fluoroscopic image intensifier is critical if it forms the vision component of an image guided surgical system. By considering non-linear dynamic distortion it is possible to greatly increase the accuracy of the image intensifier, although at the cost of some image quality.
Subject(s)
Surgical Procedures, Operative , Therapy, Computer-Assisted/instrumentation , X-Ray Intensifying Screens/standards , Calibration/standards , Fluoroscopy , Humans , Nonlinear Dynamics , Radiographic Image EnhancementABSTRACT
This paper presents a prototype system for computer assisted surgery, the purpose of which is to assist orthopaedic surgeons when performing distal locking of intramedullary nails. This system comprises three components, namely: an Intelligent Image Intensifier, a Trajectory Tactician and an Intelligent Trajectory Guide. The Intelligent Image Intensifier is an X-ray vision system that provides accurate X-ray images. Such images enable the Trajectory Tactician software to analyse the operation site and calculate the trajectory required for a screw to lock an intramedullary nail. This involves the capture of two X-ray images from which are extracted the projections of the nail's edge boundaries and its distal locking holes. Using an analytical mathematical model of the nail, the position and orientation of the nail is determined. The trajectory is then implemented by the surgeon using the Intelligent Trajectory Guide. Evaluation in the laboratory suggests that the system is capable of reliably inserting a locking screw into an intramedullary nail. The rapidity with which this computer assisted method achieves locking should benefit both patient and surgeon by reducing radiation dosage and the length of time required to lock a nail.
