Abstract
Background: Lumbosacral transitional vertebrae (LSTV) are a set of congenital variations which occur at the lumbosacral junction and are defined by dysplastic changes of the transverse process (TVP) of the final lumbar vertebra. These dysplastic changes present as an increase in craniocaudal height of the TVP and can occur unilaterally or bilaterally. Lumbosacral transitional vertebrae can be classified into 4 different types and demonstrate varying degrees of articulation and/or fusion of the last lumbar vertebra to the first sacral vertebra. The accurate enumeration of the lumbar spine in the setting of LSTV is important to clinicians appraising medical images, as well as spinal surgeons who treat low back pain (LBP). Identifying a reliable landmark by which the lumbar spine can be accurately enumerated enables correct level surgery, aids identification of neurological inconsistencies, directs the administration of nerve block injections, assists in determining the origin of LBP, and enhances treatment outcomes that are favourable.
Aim: The primary aim of this study was to identify at which lumbar spinal level, above the transitional vertebra, demonstrates the longest TVP length/s in the setting of LSTV. The secondary aim was to establish whether lumbar TVP length can be correlated to the various LSTV types (II, IIII, and IV, respectively). The tertiary aim was to identify whether other demographic factors (age at death (AD), sex, and population affinity) affect lumbar TVP lengths.
Method: This was a prospective exploratory quantitative osteological cohort study. Dried human cadaveric lumbar spinal columns were utilised to explore linear measurements, i.e., the length of the lumbar TVPs, in the setting of LSTV. The TVP lengths were then analysed and used to describe variations, correlations, and trends among the LSTV-containing cohort. Data collection was conducted at the Raymond A. Dart Collection of Modern Human Skeletons housed in the School of Anatomical Sciences at the University of Witwatersrand, Johannesburg, and at the Pretoria Bone Collection housed in the Department of Anatomy, University of Pretoria, Pretoria. The experimental group consisted of 110 (n=110) LSTV-containing individuals and the control group consisted of a randomised selection of 30 (n=30) females and 30 (n=30) males with the LSTV variation.
Procedure: A digital Vernier calliper was used to measure TVP lengths of the lumbar vertebrae above the LTSV. Each TVP was measured in horizontal length (medial to lateral) for both the left and right sides. Only vertebrae above the LSTV were measured for the experimental group. For the control group, TVPs for all lumbar vertebral levels were measured.
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Results: It can be concluded that the general trend was that the TVPs of third lumbar vertebra (L3) had the longest mean, minimum, and maximum lengths for both the left and right sides in the setting of LSTV. It can be said that LSTV Types II, III and IV have a direct influence on TVP length; TVP length increases in the setting of LSTV. Ultimately, it was established that there were no statistical differences in TVP length in the setting of LSTV. Interestingly, the experimental group demonstrated longer TVPs for every lumbar vertebral level, especially at L3, while the left side demonstrated longer TVPs overall. In the control group, it was shown that the general trend was that the TVPs of L3 had the longest mean length for both the left and right sides in both males and females.
Conclusion: The findings of this study demonstrate the usefulness of L3 TVPs as an alternate bony landmark by which the lumbar spine can be enumerated in the setting of LSTV. Therefore, it can be extrapolated to medical images i.e., radiographs, which may aid lumbar vertebral enumeration, and ultimately correct-level intervention. Additionally, this study confirms that lumbar TVP lengths in LSTV-free spines are generally the longest of the lumbar vertebrae. This study contributes to the body of knowledge which exists surrounding LSTV and its relationship to other spinal and supportive structures.