Simulation for Hip Osteotomy Using Three-Dimensional Computerized Tomography

Abstract

Three-dimensional computerized tomography (3-DCT) has been developed to overcome the inherent difficulties involved in two-dimensional assessments of images in orthopedic surgery, and surgical planning and simulations based on 3-DCT have already begun. Since 1988, we have been attempting surgical simulations using the Nagoya University Craniofacial Surgical Planning System (NUCSS) [1]. However, this is a program developed for a mainframe computer. To popularize surgical simulation, it seemed necessary to develop a program for a simulation of actual osteotomy which could be run on the smaller computers commonly used. Under these circumstances, the joint development of SurgiPlan was undertaken with the Teijin company (Yokohama, Japan) [2,3]. SurgiPlan (Fig. 1), developed as an aid to orthopedic surgical planning, is run on a UNIX Graphics 3D work station (SPARC station-2; Japan Sun Microsystems, Tokyo). Its functions are roughly divided into two categories, 2- and 3-D data processing. Two-dimensional data processing includes that undertaken preliminary to 3-D simulation, such as analysis of original CT images and separation of individual bones. Osteotomy simulation, which is the main purpose of this program, is included in the 3-D data processing function. The evaluative function includes the measurement of distances and angles and the display of contact area of joints. To run this simulation program, consecutive CT data are fed into the computer. These CT data are then processed into two levels, bone and others, to extract bone data as well as to separate data for individual bones (e.g., pelvis and femur). Then a 3-D image is constructed, and surgical simulation of osteotomy is carried out. Simulation is repeated until a satisfactory result is obtained. It is finished with recording of the distance and angle over which the bone fragments were moved, and is utilized in actual operations. In orthopedic surgery, 3-DCT is indicated in disorders of the hip joint or spine, which disorders are frequently missed in 2-D evaluation as the structures overlap one another in lateral radiographs. To date, surgical planning and post-operative evaluation of these regions have been made on the basis of 2-D imaging. It is expected that 3-D surgical planning and simulation based on 3-DCT imaging will contribute much to clinical medicine.