Poster 129: Biomechanical Evaluation of the Isometry of Medial Patellofemoral Ligament Reconstruction Grafts Fixed at Non-Anatomic Femoral Insertion Points

Objectives: In MPFL reconstruction surgery, achieving perfect placement of the femoral tunnel intraoperatively is difficult. An understanding effects malpositioning has on graft isometry crucial to minimizing instability or overconstraint which leads anterior knee pain, increased patellofemoral contact pressures, failure. The purpose this study was identify differences in with malpositioning, specifically evaluating as position moved anterior, posterior, proximal, and distal relative radiographic landmark MPFL, Schottle’s point. Methods: A biomechanical 11 fresh frozen cadaveric knees conducted. Non-elastic suture, used an analogue, anchored at point 30° flexion, 5 mm 10 superior, draw wire displacement sensor evaluate length changes analogue through 0-120° flexion. Knee flexion continuously measured using a motion tracking system. Pairwise t-tests Bonferroni corrections were compare between non- anatomic insertion points. Results: Grafts placed demonstrated mild anisometry tightening extension loosening Similarly, grafts distally posteriorly also anteriorly proximally Mean range total excursion over full ROM across specimens shown Figure 1. mean found be greater further from all directions but posterior. comparisons proximal direction significant excursion, while posterior did not (10 proximal: 0.36 (p=0.028), distal: 0.14 (p=0.012), 0.22 (p<0.001)) (Table 1). Conclusions: order minimize risk during if deviating point, it safest err position. Travel away greatest isometry. seen