SUMMARY AND KEYWORDS: The deep circumflex iliac artery (DCIA) free flap is widely used for mandibular reconstruction due to its favourable bone stock and contour. However, donor-site morbidity remains a concern. Anterior superior iliac spine (ASIS) fracture is a rare but under-recognized complication.

CASES: We present two cases of ASIS fracture following DCIA flap harvest. In both patients, the fracture occurred in the early postoperative period following mobilization and presented with acute hip pain and gait disturbance. Imaging confirmed ASIS fracture. The preserved bone bridge between the ASIS and osteotomy site measured 16.1 mm and 20.6 mm, respectively. One patient required surgical removal of the fractured ASIS while the other patient was managed conservatively with satisfactory functional recovery.

DISCUSSION: ASIS fracture following iliac crest harvest is thought to result from structural weakening of the iliac crest combined with traction forces from the sartorius and tensor fascia lata muscles. Biomechanical studies demonstrate reduced iliac crest strength when the osteotomy is performed within 20-25 mm of the ASIS. Preservation of ≥ 2-3 cm anterior bony bridge is therefore recommended. Although prophylactic donor-site fixation has been described, current evidence is limited. Most non-displaced fractures can be managed conservatively.

CONCLUSION: ASIS fracture is a rare but preventable complication of DCIA flap harvest. Maintaining an adequate distance from the ASIS and cautious postoperative mobilization are key strategies to reduce risk.