# Risk Factors of Avulsion Fracture after Iliac Crestal Flap for Jaw Reconstruction
###### Abstract  
The iliac crestal flap is often used in maxillofacial reconstruction surgery because it has a similar bone contour to jaw bone. However, complications occur frequently in this flap, and the avulsion fracture of the anterior superior iliac spine (ASIS) occurs only in rare cases. The purpose of this study is to evaluate the risk factors affecting fractures that may occur after iliac crestal flap harvesting. In this study, we performed preoperative and postoperative CT scans of the iliac bones of 22 patients who underwent iliac crestal flaps between February 2013 and July 2019. Three of these patients had fractures within 1 month after surgery. After converting DICOM files to a three-dimensional model using Mimics software, some reference points were defined for analysis. The patients were classified into fracture and non-fracture groups. The patients' age and sex, harvested bone, residual bone and absolute bed rest (ABR) periods were investigated. The patients' age and sex were not associated with fracture occurrence. There was a statistically significant difference in the width of the anterior-superior part of residual bone. The fracture group showed statistically significantly shorter ABR periods. In the case of the iliac crestal flap, it was found that the factors that can affect the occurrence of fractures are the width of the residual bone and the ABR period. Iliac avulsion fracture can be prevented when the remaining bone is sufficient and the ABR period is prolonged sufficiently. Keywords:Iliac crestal flap; mandible reconstruction; maxilla reconstruction; donor site morbidity; iliac bone fracture : 9 August 2021 26 August 2021 26 August 2021 3  
Conventionally, the anterior iliac crestal flap has been harvested as a bicortical form, which can lead to an abnormal hip contour, hernia, severe bleeding tendency, and gait disturbance [3]. The monocortical iliac crestal flap may reduce the donor-site morbidity after harvesting a large amount of bone segment [3]. Recently, computer-assisted surgery has become popular in oral and maxillofacial surgery. Most reconstructive surgeries are performed by preoperative simulation and surgical guide fabrication. Therefore, it is important to determine the optimal bone harvesting site in the anterior iliac crest for successful reconstruction during simulation for preoperative planning. Serious complications related to the iliac crestal flap are rare, but when they do occur, they cause serious problems [14]. Major complications have been reported, such as chronic pain, neurological or vascular injury, infection, hematoma, intestinal prolapse, cosmetic defect, and iliac crest avulsion fracture [5; 6; 8; 11; 14; 15; 18; 19; 20]. Among these complications, fractures of the anterior iliac crest following bone graft are very rare [5; 21; 22]; only a few cases have been reported in the literature [21; 23; 24; 25; 26; 27]. The stress fracture of the anterior iliac crest after the harvesting of theiliac crestal flap has been reported in a few works, which may cause significant problems and increase morbidity [18]. Although the avulsion fracture of the anterior superior iliac spine (ASIS) after bone grafting is not common, the fracture could occur more commonly in older patients than reported in the literature [21]. The treatment of fractures usually focuses on walking assistance after a short break until the fracture heals, but sometimes additional surgical treatment is required to remove avulsed bone or open reduction and internal fixation [21]. Previous studies have reported that the iliac crestal flap in elderly patients with osteoporosis may increase the risk of iliac crest fractures [21; 23; 28]. Some authors have reported that harvesting sites and surgery methods also could affect the fracture risk [18; 29; 30; 31; 32]. An understanding of the bone harvesting techniques and management of the risk factors for fracture could help prevent iliac crest fractures after bone grafting.