In orthopaedic spine surgery pedicle screw systems are used for stabilisation of the spine after injuries or disorders. With an percutaneous operation method surgeons are faced with huge challenges compared to an open surgery, but it's less traumatic and the patient benefits with a faster rehabilitation and less traumatic injuries. The screw positions and the required rod dimensions for the stabilising connection between the screws are hard to define without an open view on the operating field. Because of these facts a new smart device based system for rod shape determination was invented. Therefore, an application was developed, which integrates a localiser module to get the position data of the pedicle screws, with help of rigid bodies placed on top of the pedicle screws down-tubes. An algorithm was developed to choose the best fitting rod to connect the pedicle screws with help of calculating the rod length and the rod radius. The system was tested in a test scenario where four pedicle screws were drilled into a wooden plate. The positions of the screws were adjusted to fit a curved and a straight rod. In the test scenario the application chose always the rod correctly.

The key for a successful total hip replacement (THR) and the longevity of the implant is the correct alignment of the acetabular cup which is to be considered as the most critical component. The alignment of the cup is defined with respect to anterior pelvic plane (APP). The APP defines the reference for the anteversion and inclination angles which sets the basis for the correct alignment of the implant. The angle of the plane is created by three distinct anatomical landmarks which are represented by two anterior superior iliac spines (ASIS) and the symphysis pubis. The angle of the APP in respect to the coronal plane defines the pelvic tilt (PT) which can be anterior or posterior. The rotation of the pelvis highly depends on the individual anatomy of the subject. This means that a neutral pelvic tilt (PT) in supine position is rarely observed and also may be dissimilar in standing position. In this paper we present a non-invasiveness and cost-effective prototype for measuring the patient-specific PT under the use of a navigated smart-device based ultrasound system for supporting surgery planning. In view of the non-invasiveness method the system can be used to measure pre- and postoperative pelvic orientation. With the use of an artificial hip reference model different cases were measured. The computed results look very promising with a standard deviation of ±1°.