Incidence of pars defects in adolescent idiopathic scoliosis: an MRI study

Objective: In this study, our aim was to present the incidence rate of pars defect in patients with adolescent idiopathic scoliosis, based on MRI findings. Methods: Two-hundred twenty adolescent idiopathic scoliosis (AIS) patients with MRI scans, taken either as a preoperative investigation or due to other symptoms between 2006 and 2008, were included in the study. The scans were reviewed for pars defect independently by two experienced musculoskeletal radiology consultants. Results: Among the 220 patients, 9 patients (4.09%; 8 female, 1 male) were found to have a pars defect. The mean age of the affected patients was 14 (range: 11-20) years. We noted two lumbar/thoracolumbar curves (Lenke 5), four King Type 1, one King Type 2 and two King Type 3 curves. All scoliotic deformities were non-structural. Bilateral pars defect was noted in eight (89%) of these patients. All of the pars defects were at the L5 vertebral level. Conclusion: Our study revealed a 4.09% incidence rate of pars defect in AIS patients which appeared similar to those previously reported in roentgenographic studies.