# Risk Factors of Avulsion Fracture after Iliac Crestal Flap for Jaw Reconstruction
## 4 Discussion  
Harvesting autogenous bone from the iliac crest has been a reliable and well-established technique in oral and maxillofacial surgery in recent decades [33; 34; 35]. However, complications at the donor site are common [19]. The incidence of minor complications following autogenous iliac crest bone graft harvest has been reported to be from 0% to 48% [8; 36; 37; 38; 39; 40; 41] and the rate of major complications is up to 11.9% [42]. Deep infections, hemorrhages, hernias, ilium fractures and pelvic instability, as well as vascular and nervous lesions, are reported as major complications [11; 14]. Fracture is caused by the contraction of the sartioris muscle and other immediate causes [43]. The harvesting of anterior iliac crest bone grafts can occur too close to the ASIS, thereby causing the fracture of the ASIS from the iliac wing in a few studies [25; 44]. Therefore, most of the literature suggested that iliac grafts 3-4 cm posterior to the ASIS provide maximum support for the sartioris and tensor fascia latae muscles. [PERSON] et al. placed the anterior osteotomy 2 cm distal to the ASIS to avoid any weakening of the pelvic ring [35]. Additionally, [PERSON] et al. showed that the removal of bone 30 mm posterior to the ASIS preserves 2.4 times more strength of the iliac crest compared with the harvesting of a bone graft 15 mm posterior to the ASIS [23]. The downward pulling of the sartioris muscle and tensor fascia latae muscle can lead to a late stress fracture after harvesting the anterior iliac crest, so the base of ASIS must be wide enough to reduce the risk of stress fracture due to the downward pulling of the sartioris muscle [5]. In this study, there was no statistically significant difference in the distance from the ASIS to the harvesting margin between the fracture group and non-fracture group. This is because the operation was performed maintaining a sufficient distance from the ASIS of at least 2 cm to prevent the avulsion fracture of the ASIS. In order to reduce the complications of the pelvis, [PERSON] et al. reported that an osteetome-harvested graft had an increased incidence of propagations of fracture compared with saw-harvested bone grafts on fresh frozen cadavers [29]. [PERSON] et al. evaluated the morbidity of grafts by comparing traditional iliac bone grafts with minimally invasive techniques [45]. They reported that a minimally invasive technique was statistically superior for pain control, operation time and mean incision length. [PERSON] et al. reported that the short-term morbidity (pain and scar at the donor site) in the traditional open osteotomy group was slightly greater than the closed harvesting group [46]. Conversely, long-term morbidity showed a negligible difference in both groups. [PERSON] et al. reported a minimally invasive trephine method [33] which is a safe method and minimizes morbidity. [PERSON] et al. reported that there no patients experienced morbidity at the harvesting site when using a small acetabular reamer [47]. Most of the iliac crest fractures reported in the literature occurred within 2 weeks after the harvesting procedure [1; 21; 25; 26; 44; 48]. Since a forceful activity with contraction of the sartioris muscle should cause the avulsion of the weakened bone part, a sufficient ABR period is needed to stabilize the donor site. In this study, there was a statistically significant difference in ABR periods between the fracture group and non-fracture group. Clinical studies suggest that old age, obesity, osteoporosis, co-morbidities and improper harvesting techniques are the risk factors for the fracture of the iliac crest after bone grafting [5; 21; 23]. The treatment of iliac crest fracture is usually symptomatic and involves a short rest period with assisted ambulation and the usage of analgesics until the fracture has healed [23; 49].