Determination of anatomical sacral dysmorphism criteria based on CT scan findings for iliosacral screw fixation in a sample of Iranian population without pelvic ring fracture

Introduction: The pelvic ring and sacral fractures and sacroiliac dislocations are managed with different methods. The upper sacral segment dysplasia increases the risk of perforation of the osseous cortex during Iliosacral fixation with a screw. Dysmorphic sacra have narrow and angular osseous corridor. An understanding of the anatomy of the pelvis is key to the management and treatment of pelvic injuries to prevent iatrogenic injuries, and to provide the best results.To date no study has been done about sacral dysmorphism and quantitative and qualitative criteria for fixation with iliosacral screw in sacral dysmorphism in the Iranian population.Method and Material: We analyzed 100 CT scan and Outlet CT reformation forms of traumatic patients without pelvic trauma to determine 5 qualitative criteria of sacral dysmorphism (i.e., Mammillary bodies, Misshapen sacral foramen, Upper sacral segment not recessed in the pelvis, Residual disc between S1 and S2 vertebra and Acute alar slope) and sixth characteristic (tongue-in-groove) from the axial pelvic CT section were obtained by an orthopedic surgeon.Upper sacral surface area and angulation were determined from CT scan reformatted. Coronal reconstruction was used to divide the patients into dysmorphic and non-dysmorphic groups by drawing a line along the axis of the osseous corridor from one side of iliosacral to its other side. Results: The results showed that 37% of the patients were in the dysmorphic group and 63% in non-dysmorphic. The obtained mean angle in the dysmorphic and non-dysmorphic group was 84° and 72°, respectively. Sacral dysmorphism score was calculated in all patients. As the score increased, the safety of osseous corridor decreased.Conclusion: Axial angulation and coronal angulation were the most important quantitative criteria for determining the sacral dysmorphism. Detecting sacral dysmorphism can be useful for preoperative planning of iliosacral screw placement.