Surgical planning of computer-assisted repositioning osteotomies

Repositioning osteotomies are frequently used in orthopedic surgery and tra umatology to correct malpositions. Computed tomography (CT), stereolithogra phic models, and x-rays are used in planning. However, the precision achiev ed in the planning phase is usually not translated to patients. The Surgical Segment Navigator (SSN) is a navigation system that allows com puter-assisted correction of malpositions. It consists of an infrared posit ioning device, two dynamic reference frames (DRF), an infrared pointer, and an infrared camera. All data are displayed numerically and graphically on the monitor of the SSN workstation. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for plann ing surgery in the laboratory. LUCAS requires only a native CT scan. A prep aratory operation to implant bone markers that will be visible in x-rays an d a further planning CT scan showing the bone markers, which were necessary with previous systems, are not required for the LUCAS and SSN system. This significantly reduces the radiation exposure of the patient and the costs of surgical planning. Measuring anatomical landmarks in the surgical site, which is time-consumin g and reduces accuracy, is not required with the SSN system because the pos ition of die infrared transmitters is known during surgical planning on the LUCAS workstation. This makes die surgical approach faster and much more p recise. The surgical planning data are transferred to the surgical site usi ng a data file and an individual surface pattern that fits the surface of t he navigated bone segment. The data file is exported from the LUCAS-worksta tion to the SSN workstation. The planned spatial displacement of the infrar ed transmitters is saved in this file. The individual surface pattern carri es the infrared transmitters. This pattern is the mechanical interface betw een infrared transmitters and navigated bone segment. The individual surface pattern can be polymerized directly on a small stere olithographic model of the navigated bone segment. The surface pattern can also be generated as negative form from a CT data set using a computer-assi sted design/manufacture system. In summary, LUCAS and SSN allow for the computer-assisted correction of mal positions and positioning of artificial joints and implants. In principle, the systems can be used in all fields of surgery.