Computer Assisted Orthopaedic and Trauma Surgery

To create an environment where surgeons receive real-time feedback about their instrument position, computer technologies were integrated in surgical procedures. This type of surgical technology is referred to as Computer Assisted Surgery (CAS). CAS offers the possibility to continuously monitor the position of surgical instruments in relation to the patients anatomy intraoperatively. Therefore, the position of surgical instruments is superimposed virtually on single shot radiographic images in real time. This feature promises enhanced accuracy and consequently less morbidity combined with a reduction in radiation exposure. The goal of this thesis was to evaluate the hypothesis of high accuracy and reproducibility of CAS in orthopaedic and trauma surgery. In Chapter 3 the accuracy of the fluoroscopy based navigation system (Medivision, Oberdorf, CH.) was evaluated in a laboratory study performed in 20 sawbones of a proximal femur. The virtual position of the reamer appeared to be reliable in 97% of cases when considering an inaccuracy of = 2mm as clinically irrelevant. Chapter 4 describes the results of a cadaver study investigating the reliability and reproducibility of femoral anteversion angles and lengths provided by the navigation system (Medivision, Oberdorf, CH.) during femoral nailing. Length measurements provided by the navigation system showed to be reproducible and accurate enough for clinical use. The rotation measurements, however, were reproducible with a difference of almost six degrees but not accurate enough to prevent malrotation. In chapter 5 virtual planning of an anterior cruciate ligament (ACL) was analysed. Notch impingement and elongation for selected graft positioning could be predicted by displaying the kinematics of a virtual ACL on a monitor. This study indicated that computer assisted planning may reduce the inter-surgical variance to 5 mm for positioning the femoral and tibial tunnels. Moreover, the experience level of the surgeon did not effect the planning process. Chapter 6 describes the feasibility and pitfalls of CAS in the treatment of femoral neck fractures with a DHS in a small patients group. This study showed that fluoroscopy based navigation in the treatment of femoral neck fractures with a DHS is feasible. However, the technique used in this study was too complicated to use in daily practice. In Chapter 7 the results of CAS iliosacral screw fixations were compared with the results of a conventionally operated prospective control group. This study showed that fluoroscopy based CAS is a save and intuitive technique for performing posterior pelvic screw fixation. The fluoroscopy time was decreased with a factor 2.5. The use of the navigation system did not lead to a longer procedure time and may in the future even accelerate the procedure. In summary fluoroscopy based CAS is accurate enough to rely on in experimental and clinical situations. This thesis proved several clinical benefits for CAS when used for navigated guidewire insertion in iliosacral screw fixation compared with the conventional technique. The CAS femoral anteversion control module must be improved before clinical use. Computer-assisted ACL grafting has to be evaluated in a controlled study. However, it is to be expected that CAS will soon evaluate into a clinically accepted and mandatory technique in some fields of orthopaedic and trauma surger