ABSTRACT
STUDY DESIGN: Descriptive cross-sectional study. PURPOSE: To determine the frequency of lumbosacral transitional vertebrae (LSTV) in patients with low back pain (LBP) and the role of iliolumbar ligament (ILL) origin from L5 in LSTV cases. OVERVIEW OF LITERATURE: Transitional vertebrae are developmental variants of the spine. LSTV is a common congenital abnormality, and failure to recognize this anomaly may result in serious consequences during surgery. METHODS: All patients aged 11–90 years of either gender with LBP for any duration, who presented for X-ray and magnetic resonance imaging (MRI) of the lumbosacral spine, were included. X-rays of the lumbosacral spine in anteroposterior and lateral views were acquired. In addition, T1- and T2-weighted sagittal and axial MRI was performed. Images were evaluated on a workstation. RESULTS: Of 504 patients, transitional vertebrae were observed in 75 patients (15%). Among them, 39 (52%) patients had Castellvi type III and 36 (48%) patients had Castellvi type II. However, on MRI, 42 (56%) patients had O'Driscoll type II, 18 (24%) patients had O'Driscoll type IV, and 15 patients (20%) had O'Driscoll type III. ILL origin from L5 was significantly higher (n=429, 100%) among patients with a normal lumbosacral junction than among patients with a transitional lumbosacral junction (n=22, 29.3%) (p < 0.001). CONCLUSIONS: LSTV occurs at a high frequency in patients with LBP. Furthermore, in the presence of LSTV, the ILL is not a reliable marker for the identification of L5.