Response to “Is the Greater Trochanter the Ideal Freehand Landmark for the S2AI Screw Angle in the Caudal Direction? Commentary on ‘Extra-Articular Portion of the Sacroiliac Joint—Between the Sacral and Pelvic Tuberosities: An Anatomical Guide for the S2-Alar-Iliac Screw Trajectory’ by Tatara et al”

We use navigation software preoperatively to determine the entry point and trajectory of the S2AI screw and the approximate screw size. There are three key points to our surgical method: first, we made it easier to touch the top of the greater trochanter during surgery; second, the guidewire was inserted along the sacral tuberosity from the extra-articular portion of the sacroiliac joint, but it was always inserted into the iliac bone; and third, we always took intraoperative X-rays.

As you pointed out, the tip of the greater trochanter is not the only unique and absolute signpost, so the screw trajectory will be adjusted based on the intraoperative X-ray images. However, in our experiences, the tip of the greater trochanter is not completely off the mark, and we have never felt the need to perform CT scans with patients in the prone position.