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Summary19910posterior tibial slopes was calculated. The main finding was little (if any) to weak correlations between dynamic anterior tibial translation and amount of posterior tibial slope, both before and after ACL reconstruction. As with dynamic translation, little (if any) to weak correlations between dynamic range of tibial rotation and posterior tibial slope were observed with ACL deficiency. However, one year after ACL reconstruction we observed moderate-to-strong correlations between range of tibial rotation and posterior tibial slope. This study suggests that muscular activity enables subjects to compensate for anatomical factors such as posterior tibial slope by moderating their muscle activation patterns and kinematics when studied during high-demand activities. These compensatory mechanisms fail to make up for rotatory laxity one year after ACL reconstruction. Chapter 6 describes our first steps towards the development of a patient-specific surgical guide for the creation of a femoral tunnel in the anatomic footprint of the ACL. This study answers the question of whether we can reliably identify the footprint of a torn ACL on MRI. Orthopaedic surgeons and residents and musculoskeletal-trained radiologists were asked to identify the femoral footprint of the ACL on MRI. Twenty MRIs were evaluated twice, at intervals of at least one week. We demonstrated excellent intraobserver and interobserver reliability. The interobserver reliability was less than the intraobserver reliability. Orthopaedic surgeons had a higher level of intraobserver and interobserver agreement compared to musculoskeletal-trained radiologists and, to a lesser extent, to orthopaedic residents. Employing this feature, experienced orthopaedic surgeons are the preferred physicians to preoperatively plan femoral tunnel positioning in patient-specific ACL reconstruction.In Chapter 7 the first in vitro results of the newly developed patient-specific surgical guide for the creation of a femoral tunnel in ACL reconstruction are demonstrated. The design ratio and manufacturing process are highlighted and the results of a cadaveric study are presented. In an open procedure, using a polyamide-12 3D printed guide a mean deviation of 5 mm from the planned tunnel position was achieved. While the technique and development seem promising, this was outside our intended target of < 2 mm. Further improvement in the design and materials are needed before this concept can be introduced in an in vivo setting.Mark Zee.indd 199 03-01-2024 08:56