The diaphysis of the femur is surrounded by a thick muscular envelope. The major neurovascular structures are located medially and posteriorly, and, therefore, the femur can safely be approached over the anterolateral region.
Overall neurovascular status of the limb
For pin insertion, the condition of the soft-tissue envelope of the femoral shaft has to be considered (areas of crush injuries, or areas of extensive soft-tissue damage should be avoided, in order to minimize the risk of subsequent pin-track infection).
The safest anatomical zones for pin insertion are the anterolateral and direct lateral regions of the femur. See anatomical location of muscle groups and neurovascular bundles in each respective region.