A computer implemented method for accounting for femoral abduction, comprising: acquiring a preoperative image of a surgical site, the surgical site including a skeletal bone and a femur, the femur capable of articulating with respect to the skeletal bone; acquiring an intraoperative image of the surgical site after an implant has been affixed to the femur; generating a first landmark point (400; 528) on the femur in the intraoperative image; generating the first landmark point (378; 528) on the femur in the preoperative image; arranging a cutout of the femur from the intraoperative image on the preoperative image, such that the first landmark points are collocated; determining a difference angle (α) about the collocated first landmark points between a femoral axis (L1; 3104) of the femur in the preoperative image relative to a femoral axis (L2; 3108) of the femur in the intraoperative cutout image; arranging the intraoperative image and the preoperative image, such that the skeletal bone in the intraoperative image and in the preoperative image are in overlying alignment with respect to each other; identifying a centre of rotation of the implant in at least one of the preoperative and intraoperative images; identifying a corrected landmark point, wherein the corrected landmark point is equal to the first landmark point in the intraoperative image after it is rotated, about the centre of rotation of the implant, an amount equal to the difference angle; and calculating at least one of offset and length differential of at least the femur by analysing the vector (v) between the first landmark point in the preoperative image and the corrected landmark point, thereby accounting for femoral abduction, wherein calculating the length differential of the femur comprises calculating the component of the vector along the femoral axis of the femur in the preoperative image, and wherein calculating the offset of the femur comprises calculating the component of the vector along a line perpendicular to the femoral axis of the femur in the preoperative image. acquiring a preoperative image of a surgical site, the surgical site including a skeletal bone and a femur, the femur capable of articulating with respect to the skeletal bone; acquiring an intraoperative image of the surgical site after an implant has been affixed to the femur; generating a first landmark point (400; 528) on the femur in the intraoperative image; generating the first landmark point (378; 528) on the femur in the preoperative image; arranging a cutout of the femur from the intraoperative image on the preoperative image, such that the first landmark points are collocated; determining a difference angle (α) about the collocated first landmark points between a femoral axis (L1; 3104) of the femur in the preoperative image relative to a femoral axis (L2; 3108) of the femur in the intraoperative cutout image; arranging the intraoperative image and the preoperative image, such that the skeletal bone in the intraoperative image and in the preoperative image are in overlying alignment with respect to each other; identifying a centre of rotation of the implant in at least one of the preoperative and intraoperative images; identifying a corrected landmark point, wherein the corrected landmark point is equal to the first landmark point in the intraoperative image after it is rotated, about the centre of rotation of the implant, an amount equal to the difference angle; and calculating at least one of offset and length differential of at least the femur by analysing the vector (v) between the first landmark point in the preoperative image and the corrected landmark point, thereby accounting for femoral abduction, wherein calculating the length differential of the femur comprises calculating the component of the vector along the femoral axis of the femur in the preoperative image, and wherein calculating the offset of the femur comprises calculating the component of the vector along a line perpendicular to the femoral axis of the femur in the preoperative image.