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Um die Zeitraume zu minimieren, die nach einem endoprothetischen Gelenkersatz zur Regeneration des Patienten notig sind, und eine moglichst schnelle und weitestgehende Wiederherstellung der Funktion wahrend der Rehabilitation zu ermoglichen, ist ein gewisses Verstandnis der mechanischen Bedingungen notig. Wissen um die mechanischen Bedingungen ist insbesondere deshalb von Bedeutung, weil zum einen die Endoprothese die makroskopischen Bedingungen fur das Gelenk grundlegend andert. Zum anderen bestimmt das chirurgische Vorgehen – beim Kniegelenk besonders die Balance und Aktivitat der Weichteile – die mechanischen Rahmenbedingungen, unter denen die knocherne Integration des Implantats stattfindet. Somit sind die biomechanischen Bedingungen nicht nur fur die Funktion, sondern auch fur die Dauerhaftigkeit des Gelenkersatzes in dem sich mit dem Alter andernden biologischen Umfeld entscheidend.

In total hip arthroplasty, an optimal cup orientation is essential to avoid dislocations. Computer assisted systems provide the surgeon with the intra-operative cup orientation. However, these systems rely on the palpation of the anterior pelvic plane, and are thereby prone to the palpation error of this plane. As this error is directly linked to the soft tissue overlying the pelvic landmarks, we developed a navigated ultrasound system to acquire the anterior pelvic plane. 5 operators acquired 5 times the anterior pelvic plane of 2 female cadavers. After a learning curve, the acquisition of the plane took approximately 90 seconds. Compared to the anterior pelvic plane measured on the CT-scan, the mean rotation error was less than 0.5°, with a standard deviation of less than 1.2°. The mean version error was -1.2°, and the standard deviation remained below 1.9°. Our results confirm that navigated ultrasound is a very accurate tool to acquire the anterior pelvic plane and thereby allow an accurate navigation of total hip arthroplasty.

This work presents an approach towards reconstructing ligament and tendon attachment sites from 3D medical image data. We apply statistical shape models with an additional free form step to reconstruct the anatomical shape of the distal femur from CT data. After the shape fitting process the locations of ligament attachment sites, which are incorporated in the geometric model, are extracted and their positions optimized via an image based approach. To show the potential of our method we manually extracted the surface of 11 distal femora and their corresponding ligament attachment sites in clinical CT data and compared them to the results of our method.