University of Twente Student Theses


Preoperative individualized planning tool to determine 3D tunnel orientation for ACL reconstructions

Hendriks, M.S. (2015) Preoperative individualized planning tool to determine 3D tunnel orientation for ACL reconstructions.

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Abstract:Background: The Anterior Cruciate Ligament (ACL) is one of the most frequently injured ligaments of the knee. ACL injuries are commonly treated by surgery, which attempts to restore the translational and rotational stability of the knee. The literature report failure rates between 10% and 25% after primary ACL reconstruction of which 70% to 80% is caused by inadequate tunnel placement. Problem: In recent years, many studies only focused on the anatomical positioning of the femoral tunnel at the native insertion site in order to improve tunnel placement. However, the current surgical arthroscopic ACL reconstruction technique provides no unambiguous protocol for femoral tunnel drilling. Therefore, there is still a considerable freedom in drilling angle, limited by exion angle of the knee, the femoral notch shape and the location of the endoscopic portals. As a consequence, standards for the tunnel-exit on the lateral wall are not defined, although in the literature is described that a sharp bending angle between the femoral and tibial tunnel by a non-optimal drilling angle results in graft damage due to repetitive bending stress forces at the femoral tunnel aperture. Hypothesis / Purpose: The clinical outcome after ACL reconstruction will be improved by determining an individualized optimal femoral and tibia tunnel orientation. Methods of approach: In this study, a 3D computer model is developed to pre-operatively assess the optimal patient-specific tunnel orientation. MRI-scans are used to generate an individual 3D-model of the knee. The optimal patient-specific tunnel orientation is subsequently determined with a focus on a minimal bending angle of the graft at femoral and tibial tunnel aperture over the entire range of motion. The computer model will account for the surgical boundary conditions and patient-specific anatomical characteristics. The 3D model is evaluated by calculating the optimal tunnel orientation using MRI scans of operative patients. These findings were then compared with the actually placed tunnels, because we suggest that tunnel position of failed ACL reconstruct significant differs from the predicted tunnel placement of our developed 3D model. Results: Optimal patient-specific tunnel orientation were calculated with the developed 3D computer model on MRI-scans of operative patients with known clinical outcome. Tunnel orientation, the effect of femoral tunnel position on surface area and shape of the aperture, graft orientation and inclination, elongation of the graft were compared with knowledge in the literature. Results of calculation were in terms of horizontal and vertical tunnel angles which can be used by drilling the tunnels intraoperatively. Conclusion: The present study demonstrates a 3D computer model to individualize ACL reconstruction in terms of femoral and tibial tunnel orientation to reproduce the native ACL characteristics as closely as possible. Further work is necessary to determine the relevance of the morphologic orientation of both tunnels at clinical outcome after ACL reconstruction. Some additional studies are needed to actuallyapply the 3D model in a clinical setting.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Programme:Electrical Engineering MSc (60353)
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