Background <p>No appropriate studies have been conducted that compare the biomechanical properties of different fenestration positions in deep circumflex iliac artery (DCIA)-vascularized iliac bone grafts for femoral head necrosis (ONFH) treatment. In this study, we aimed to explore the fenestration locations of DCIA-vascularized iliac grafting in ONFH treatment using FEA and clinical retrospective analysis.</p> Methods <p>We simulated an iliac bone flap transplantation with a vascularized tip by finite element analysis (FEA). Patients were divided into four groups using different femur fenestration positions as follows: center-window group (C-group), superior-window group (S-group), medial-window group (M-group), and inferior-window group (I-group). In this study, we primarily observed the maximum femoral stress at different healing degrees (0, 25, 50, 75, and 100%). We retrospectively analyzed the changes in the postoperative Harris scores (HHS) and the imaging of 16 patients with iliac flaps for ONFH (11 and 5 cases in the center and other-positioned groups, respectively) at the final follow-up visit.</p> Results <p>The FEA results showed that the peak von Mises stresses in the four groups at the time of complete healing were in the following order: group C (20.28 MPa) &lt; group I (20.33 MPa) &lt; group M (20.92 MPa) &lt; group S (22.00&#xa0;MPa). A clinical retrospective study following a comparison of the two groups found that the mean improvement in HHS was 18.00 ± 12.38 in the center-window group and 13.60 ± 25.55 in the other groups. However, no significant difference was observed in the rate of collapse (36.37 vs. 40.00%) or changes in the HHS between the two groups.</p> Conclusion <p>A fenestration at the center of the femoral neck resulted in improved biomechanical gain and clinical outcomes.</p> Trial registration <p>approval was granted by the Ethics Committee (II202418102).</p>