Evaluation of castellvi classification in lumbosacral transitional vertebrae and its relationship with psoas muscle area

Objective: Lumbosacral Transitional Vertebra (LSTV) is a common anatomical variation. We aimed to determine the frequency and typing of Lumbosacral Transitional Vertebra using Castellvi classification, to determine the relationship of the psoas muscle area with LSTV and its subtypes, to evaluate whether it differs significantly from the normal population, and to compare it with the literature. Material and Method: Our study is a retrospective study and 1344 patient (482 of them is female which equals %35.8, 862 of them is male which equals %64.1) between 18-65 age whom underwent whole spine computerized tomography(CT) scans for any reason between January 2020 and January 2023 at Dicle University Medical Faculty Hospital were included. Sagittal and coronal images were obtained with multiplanar reconstruction algorithm through axial section of CT images from CT devices equipped with 16 and 64 detectors. The assessments were done blindly twice by the same observant. Patients with psoas muscle infection, abscess or hematoma; malignancy where psoas muscle is kept as primary or secondary, L3 vertebra fracture, undergoing surgery to the lumbar region, marked scoliosis, spondylolisthesis of grade 2 and above, bone metastasis and images with artifacts that limit the evaluation were not included in the study. Findings: 482 of them were female (% 35.8), and 862 were male (%64.1). The LSTV is diagnosed by 614 of them (%45.7), sacralization is observed at 576 of them (%93.8), and lumbarization is observed at 38 of them ( %6.2). It is found that 97(%16.1) of them are in the right, 127 of them (%21) are in the left and 380 of them (%62.9) are diagnosed as bilateral. When patients analyzed in accordance with LSVT type, it is determined that 88 of them (%14.4) are 1A; 141 of them (%23) are 1B; 121 of them (%19.7) are 2A; 152 of them (%24.8) are 2B; 13 of them (%2.1) are 3A; 68 of them (%11.1) has 3B; 21 of them (%3.4) are 4 and 9 of them as total lumbarized . The left and right psoas muscle area of the patients were found significantly higher than the control group. It is noted that there was no significant difference between PS muscle areas between unilateral and bilateral LSTV types and unilateral LSTV subtypes (1A, 2A, 3A). The significant relation was found between LSTV and the existence of cervical costa (p= 0,003), and twelfth costa aplasia/hypoplasia (p=0,005). Conclusion: LSTV was observed in 45.7% of our patients included in the study. In order to prevent the wrong level of surgery or injection in any spinal intervention to the lumbosacral region, all vertebral imaging ought to be performed before the operation, taking into account both the increased costal variation rates and the high prevalence of LSTV. The necessity of correlation of the case with other imaging modalities ought to be reported if needed, and the presence and typing of LSTV should be determined with absolute accuracy. Keywords: Lumbosacral transitional vertebra, Bertolotti syndrome, Castellvi classification, Computed tomography