# Lumbosacral Transitional Disorder as a Missing Link in Symptomatic Scoliosis
## 1 Introduction  
In 1917, [PERSON] stated that LSTVs (lumbosacral transitional vertebrae) can cause low back pain [1]. [PERSON] et al. classified LSTVs into four types. Type I includes unilateral (IA) or bilateral (IB) dysplastic transverse processes with a width of at least 19 mm(craniocaudal dimension). Type II shows incomplete unilateral (IIA) or bilateral (IIB) lumbarization/sacralization with an enlarged transverse process that forms a pseudarthrotic joint between itself and the sacrum. Type III describes unilateral (IIIA) or bilateral (IIIB) lumbarization/sacralization with complete bony fusion of the transverse process(es) to the sacrum. Type IV involves a unilateral transition from type II to type III on the contralateral side [2], see Figure 1.  
The Ferguson image (AP radiograph with a 30\({}^{\circ}\) angle) serves as the standard method for detecting LSTVs. However, this radiograph is not the same as that used to clarify scoliosis. Thus, an additional radiograph becomes necessary. The alternative is an MRI scan, which can also provide additional information for all three spatial planes. Diagnostic errors in determining vertebral body assignment on sagittal radiography and lumbar MRI are also common [3; 4; 5], see Figure 2.  
Therefore, routinely obtaining sagittal MRI images of the entire spine is recommended. The caudal numbering of C2 on MRI images of the entire spine and the use of Castel-lvi's morphologic classification allow for the correct identification of both numeric and morphologic vertebral variations [6; 7; 8]. The use of MRI has demonstrated a sensitivity of up to 80% in identifying LSTVs. However, sagittal and axial images alone have been shown to increase the likelihood of  
Figure 1: Classification for LSTVs. Example of scoliosis Lenke 1 and 5 with LSTV Castellvi IIA. Figure 2: Ferguson technique (30\({}^{\circ}\) inclination). misdiagnosis [9]. CT scans provide the highest accuracy in assessing bony anatomy and may be useful in considering LSTVs. [PERSON] et al. advocate for measuring segmental differences in the vertical mid-vertebral angle (Diff-VMA) and vertical anterior vertebral angle (Diff-VOVA) of the three most caudally located segments of the lumbar spine to easily and reliably identify LSTVs. A Diff-VMVA of \(\leq\)+10\({}^{\circ}\) identified type III and IV LSTVs with a sensitivity of 100% and a specificity of 89% on MRI [10; 11]. [PERSON] et al. [11] state that LSTVs may show increased lordosis of the lumbar spine and a lack of angulation at the lumbosacral junction. Measurement of angles allows for the prediction of the presence of LSTVs. Other methods of measurement in the sagittal slices of MRI scans are also described for the identification of an LSTV. In this regard, the variability in the vertebral bodies makes it difficult to define L5 and S1 accurately [12]. As indicated, the number of vertebral bodies is not an assured constant. A high prevalence of variations in the number of thoracic or lumbar vertebrae is also described for scoliosis patients. However, this is mainly crucial in fusion surgery or pseudoaorthectomy [13; 14]. According to [PERSON] et al., the prevalence in the studied MRI scans of 769 consecutive patients of [PERSON] syndrome is 4.6% in the general population and 11.4% in those with back pain who are younger than 30 [15]. Unilateral LSTVs result in asymmetric biomechanical loading. The side with the extra L5/S1 junction carries a higher proportion of the load, resulting in lateral tilting with the scoliotic curvature. This local loading leads to higher wear and unilateral muscle activity. In addition, asymmetric motion may also influence disc degeneration [16]. The Lenke classification for scoliosis forms the current international standard [17] and focuses on scoliosis surgery. However, there is no generally accepted uniform classification for brace fitting, so various classifications are used. The Lenke classification is applied in the study by [PERSON] et al. [18].