Vertebrae at the thoracolumbar junction: A quantitative assessment using CT scans

Thoracolumbar/Lumbar Degenerative Kyphosis-The Importance of Thoracolumbar Junction in Sagittal Alignment and Balance

PURPOSE

To conduct a more comprehensive study of sagittal alignment in patients with thoracolumbar/lumbar (TL/L) degenerative kyphosis.

METHODS

A total of 133 consecutive patients from September 2016 to March 2019 with degenerative spinal kyphosis were enrolled. These patients were divided into different types according to sagittal alignment, including thoracolumbar junctional kyphosis (TLJK). Then, we divided the patients with TLJK into two groups: the Sagittal Balance group (C7-SVA < 50 mm) and the Sagittal Imbalance group (C7-SVA ≥ 50 mm). The sagittal parameters of each type or group were compared and correlation analysis was conducted.

RESULTS

Thoracolumbar/lumbar degenerative kyphosis consists of four types: Type I, lumbar kyphosis; Type II, degenerative flat back; Type III, thoracolumbar junctional kyphosis; and Type IV, global kyphosis. According to different sagittal alignments, Type III can further be divided into three subtypes: IIIA, with smooth kyphosis of thoracic and upper lumbar; IIIB, like a clasp knife, with a flat thoracic and lumbar angle; and IIIC, with bigger thoracic kyphosis and lumbar lordosis. The thoracolumbar kyphosis angle (°) of the three subtypes were -23.61 ± 5.37, -25.40 ± 7.71, and -40.01 ± 8.40, respectively. Lumbar lordosis was correlated with thoracic kyphosis (IIIA, r = -0.600, p = 0.005; IIIB, r = -0.312, p = 0.046; IIIC, r = -0.657, p = 0.015), and correlated with sacral slope (IIIA, r = 0.537, p = 0.015; IIIB, r = 0.654, p = 0.000; IIIC, r = 0.578, p = 0.039). All spinopelvic parameters were compared between the Sagittal Balance group and the Sagittal Imbalance group, and only the thoracolumbar kyphosis angle showed statistical difference (t = -2.247, p = 0.028).

CONCLUSIONS

The common characteristics of thoracolumbar junctional kyphosis were found to be a bigger thoracolumbar junctional angle and vertex of kyphosis located in the thoracolumbar junction (T10-L2). Despite TLJK, a change in the thoracic angle was still important to maintain sagittal balance. The thoracolumbar junction plays an important role in sagittal alignment and balance.

Thoracolumbar transitional vertebrae: Quantitative differentiation and associated numeric variation in the vertebral column using skeletal remains

Transitional vertebrae at the thoracolumbar region are called thoracolumbar transitional vertebrae (TLTV) and retain physical features from the thoracic and lumbar regions. Since TLTV were first classified 40 years ago, there has been much discrepancy regarding its features, identification and clinical relevance. Vertebral body levels are used in the medical field as a frame of reference to locate specific organs, vessels, nerves or landmarks. Any numeric variation or deviation in the vertebral column may lead to clinical errors. Previous findings have suggested a high association between numeric variation and the presence of TLTV. Therefore, the aim of this study was to identify the types of TLTV observed and to identify any possible associated numeric variation in the vertebral column. This study also aimed to validate the established technique to quantitatively differentiate TLTV from T12 and L1 at the thoracolumbar junction using skeletal remains from a South African population group. Skeletal remains (n = 187) remains from the Pretoria bone collection were assessed. Measurements were taken of the angle of the superior zygapophyseal processes of the last thoracic vertebra (T12), the first lumbar (L1), and identified TLTV. The results indicate a TLTV prevalence of 35% (n = 66/187). The results show that each vertebral type (T12, L1, TLTV) fall into independent confidence intervals: T12 is 188° ± 9.22 (CI: 187° < μ < 189.6°), 110° ± 7.52 (CI: 109.2° < μ < 111.3°) in L1, and 135° ± 24.51 (CI: 130.4° < μ < 139.1°) in the TLTV. This study observed that 70% of cases with TLTV was associated with numeric variation in the spine, both homeotic and meristic and that TLTV has a 35% prevalence. The results clearly show that quantitative morphometric analysis can effectively differentiate TLTV from other vertebral types at the thoracolumbar junction in skeletal remains.

Congenital malformations in the vertebral column: associations and possible embryologic origins

Cases of associations between random spinal congenital defects have previously been reported, yet several questions remain unanswered. Firstly, why are associations between what seems to be random combinations of vertebral malformations observed? Secondly, is there a common event or pattern that connects the associated defects? Therefore, this study aimed to identify congenital defects in the vertebral column and also to determine whether any associations, if present, between vertebral malformations exist. This article consequently discusses the possible embryological disruptions that may lead to the formation of various defects in the vertebral column. A random skeletal sample (n=187) was selected from the Pretoria Bone Collection housed in the Department of Anatomy, University of Pretoria (Ethics 678/2018). The sample was evaluated to determine the frequencies of spinal congenital defects in each set of remains. Identifiable congenital malformations were observed in 48.1% (n=90/187) of the sample. The results demonstrated a high probability of association between the different defects observed in the vertebral column. Findings are of value as they provide a reasonable explanation to why seemingly random cases of associations have been reported by several authors. This study is clinically relevant as severe spinal defects have been shown to have high morbidity in patients and mortality in infants.