| Purpose To investigate the positional relationship between the femoral tunnel outlet on the medial femoral condyle and the medial and posteromedial anatomical structures of the knee joint during single-bundle posterior cruciate ligament reconstruction,to verify whether various femoral tunnel drilling angles will cause damage to the surrounding anatomic structures,and to further estimate the safe drilling angle range for the femoral tunnel placement.Methods Eleven human knee joint specimens were used.Careful dissection on each knee joint specimen was performed to determine the outline of the region where each anatomical structure runs and attaches on the femoral medial aspect,as well as to identify a bare bony area to be used as a safe zone in this study,which could be composed of areas 10 mm away from the articular and avoiding the distribution and attachment of ligamentous structures.Each knee joint specimen was fixed at a flexion angle of 120°,and then the posterior cruciate ligament was cut to expose its femoral attachment area.The process of femoral tunnel preparation for PCL single-bundle reconstruction was simulated using the inside-out technique to drill the femoral tunnel.The creation of femoral tunnels in different directions was realized by combining the angles of the axial plane and the coronal plane;the anatomic femoral axis was regarded as the 0°reference angle in the coronal plane,and the transepicondylar axis was regarded as the 0°reference angle in the axial plane.The following 20 angle combinations for femoral tunnel drilling were selected:0°/15°,0°/30°,0°/45°,0°/60°,15°/15°,15°/30°,15°/45°,15°/60°,30°/15°,30°/30°,30°/45°,30°/60°,45°/15°,45°/30°,45°/45°,45°/60°,60°/15°,60°/30°,60°/45°,and 60°/60°(axial/coronal).According to the positional relationship between the femoral tunnel outlet produced by various drilling angles on the medial femoral condyle and the safe zone,it would be verified whether the femoral tunnel placement angle is a risk factor for damage to the medial and posteromedial anatomical structures of the knee joint,and the safe angle range for the femoral tunnel placement would be further estimated.Results When creating the femoral tunnel for single-bundle posterior cruciate ligament reconstruction,there was a risk of damage to the medial collateral ligament,the posterior oblique ligament,and other medial and posteromedial anatomical structures of the knee joint caused by the tunnel outlet.Particularly,the risk of damage was 100%when the drilling angles were 0°and 15°on the axial plane.When the drilling orientation of the femoral tunnel was changed to different angles,the risk of iatrogenic injury significantly differed(χ~2=168.880,P<0.001).The frequency of the situation arising that the femoral tunnel outlet was located within the safe zone was significantly different when using angle combinations of 45/45°,45/60°,60/30°,60/45°,and 60/60°(axial/coronal)compared with the other 15 angles(P<0.05).The femoral tunnel drilling angle in the axial plane was negatively correlated with the shortest distance from the exit center of the femoral tunnel to the safe zone(P=8.43*10-38,r=-0.810).Conclusion In the process of single-bundle posterior cruciate ligament reconstruction,the creation of the femoral tunnel will cause damage to the medial and posteromedial structures of the knee joint,such as the medial collateral ligament and the posterior oblique ligament,and the risk of injury is affected by the angle of the femoral tunnel placement.Therefore,in order to avoid damage to these structures during the operation as much as possible,it is recommended to create a femoral tunnel in the range of 45°～60°in the coronal plane when the cruciate ligament guide is put at 45°in the axial plane or in the range of 30°～60°in the coronal plane when the guide is put at 60°in the axial plane. |
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