**2.7 Cannulated intra-medullary screws**

Our intra-medullary fixation preference is now a cannulated intra-medullary screw (**Figure 1**) with differential threads at either end. Originally, we used 4.5 mm diameter Herbert screws for females and adolescent males and the 6.5 mm Herbert screws for most adult males. Unfortunately, these have been discontinued recently. We successfully have variants on this theme with different diameters and lengths. Typically, 70–100 mm lengths have been suitable. The advantage of this design is that temporary reduction can be made over a guide wire before definitive placement of the cannulated screw. The screw can be made completely intra-osseous reducing the likelihood of hardware irritation and the need for subsequent removal. The differential threads at either end of the screw provide length and rotational control (**Figure 2**).
