  In this study, we investigated a method allowing the determination of the
femur bone surface as well as its mechanical axis from some easy-to-identify
bony landmarks. The reconstruction of the whole femur is therefore performed
from these landmarks using a Statistical Shape Model (SSM). The aim of this
research is therefore to assess the impact of the number, the position, and the
accuracy of the landmarks for the reconstruction of the femur and the
determination of its related mechanical axis, an important clinical parameter
to consider for the lower limb analysis. Two statistical femur models were
created from our in-house dataset and a publicly available dataset. Both were
evaluated in terms of average point-to-point surface distance error and through
the mechanical axis of the femur. Furthermore, the clinical impact of using
landmarks on the skin in replacement of bony landmarks is investigated. The
predicted proximal femurs from bony landmarks were more accurate compared to
on-skin landmarks while both had less than 3.5 degrees mechanical axis angle
deviation error. The results regarding the non-invasive determination of the
mechanical axis are very encouraging and could open very interesting clinical
perspectives for the analysis of the lower limb either for orthopedics or
functional rehabilitation.
