The objective of the project is to develop an accurate method for the insertion of pedicle screws into spinal vertebrae with minimal invasion. The insertion is currently performed with computer assistance through a large open wound. A major improvement would be if the screws could be inserted through small incised wounds. A minimally invasive approach requires a percutaneous device which provides an accurate registration of the operating tools and a preoperative computed tomography image. The ultrasound technique seems promising for the intraoperative use.
A new method will be developed for the extraction of the bone surface from an ultrasound image of a vertebra covered by soft tissue. The intraoperative calibration of the ultrasound probe in a sterile environment will be studied. Novel surface matching techniques will be investigated for the registration of an intraoperative ultrasound image and a preoperative computed tomography image. The registration method developed will be verified in a series of experiments. The system will then be brought into an operating room and a clinical trial will be performed. The results will be directly exploited at ORTON Orthopaedic Hospital. The registration method may also result in a major breakthrough in orthopaedic hip and knee surgery in addition to spine surgery.
The current computer assisted method (CAOS) has been developed in cooperation with ORTON Research Unit and M. E. Müller Institute for Biomechanics. ORTON Orthopaedic Hospital operates three times a week using CAOS since 1995. M. E. Müller Institute for Biomechanics is familiar with the ultrasound technique whereas Institute of Photogrammetry and Remote Sensing at HUT has the knowledge of surface matching for the registration of 3-D images.