Quantitative differentiation of thoracolumbar transitional vertebrae : possible embryological origins and associations with other anomalies in the vertebral column

Abstract

INTRODUCTION: Transitional vertebrae result from overlapping developmental fields in the spine and can be located at any regional junction in the vertebral column. Consequently, transitional vertebrae retain features from the two respective adjacent regions. Based on the current literature, a need to further investigate TLTV with regards to repeatable differentiation, classification and clinical significance had been identified. MATERIALS AND METHODS: Therefore, this project aimed to identify vertebral anomalies and to determine whether TLTV can be quantitatively differentiated from thoracic and lumbar vertebrae using skeletal remains from Pretoria and the Western Cape of South Africa (n=287). This was achieved by measuring the superior zygapophyseal facet angle. This project also evaluated whether the measuring tool can be applied to living persons. Therefore this study additionally aimed to evaluate whether measurements can be used to differentiate vertebrae at the thoracolumbar junction using CT scans (n=175) representative of the Windhoek population in Namibia. This study also aimed to evaluate whether associations exist among congenital malformations of the spine and to explore the embryological events that lead to the formation of various anomalies in the spine. RESULTS: The results show that the prevalence of TLTV ranges between 7.5% (Windhoek), 30% (Western Cape) and 33.2% (Pretoria) in the reference samples. The results also clearly demonstrate that each vertebral type (thoracic, lumbar, TLTV) falls into separate distributions and confidence intervals. The results show that the mean angles and confidence intervals in skeletal remains for T12 is 189 ±9.5o (CI: 188o-190o), 110.6o ±7.88 (CI: 109.7o - 111.6o) for L1, and 137o ± 24.11 (CI: 133.5o - 140.5o) for TLTV. The mean confidence interval in CT-scans for T12 is 182.8 ± 10.4o (CI: 181.6o-183.9o), 112.3 ± 7.27o (CI: 111.5o-113o) for L1, and 136 ± 23.18o (CI: 125o- 147o) for TLTV. These results infer that each type of vertebra has independent measurable criteria to identify it. High correlation coefficients demonstrated the repeatability of the measurements using skeletal remains (0.94 < r < 0.97) and CT-scans (0.978< r < 0.997). CONCLUSION: The results strongly infer that quantitative morphometry from the superior articular facets of vertebrae can differentiate between T12, L1 and TLTV using radio-images or skeletal remains. This study also concludes that individuals with one defect or congenital malformation in the spine are more likely to have at least one other associated anomaly of the spine.