Background: Wrong placement of the ACL transplant especially in femoral site can result in early graft failure. Anatomical placement of the femoral tunnel results in restoration of knee kinematics closer to those of the intact knee. This placement could be performed by either using “aimer device” or with “free hand” methods. We compare the geometric position of femoral canal created by these two techniques.

Methods: In a prospective study, 22 patients were devided into two groups (11 patients) and operated by using femoral aimer instrument and “Free hand” techniques. Intra-operative fluoroscopy for femoral guide pin position was performed to determine the guide pin position. Vertical and horizontal coordinates of guide pins in both groups were outlined and compared with standard anatomical point of guide pins.

 Results: in “aimer” group the coordinates of the guide pin location was 41.33% vertically and 33.49% horizontally and the difference with anatomic location in both vertical (p < /em>=.03) and horizontal (p < /em>=.02) vectors was significant. The coordinates for the location of the guide pin in the “free hand” group were 35.33% and 33.07% respectively and the difference between anatomical location and guide pin width was significant (p < /em>=.04), and in this group, difference in the height was observed. The sum errors in width and height plane in “aimer” and “free hand” groups were 13.82 and 7.4 respectively.

Conclusions: Anatomic positioning of guide pin is possible through both free hand and instrument techniques. The percentage of error in instrument technique is more than free hand method.