Considering the inferior surface area of lower lumbar vertebrae: determining weight transmission pattern at the lumbosacral junction
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The biomechanical function of the lumbosacral junction (LSJ) is obscure, but its medical significance is not, as it is the most common site of low back pain. In this study, we analyzed the difference between the mean values of the surface areas of the inferior body and total inferior facet areas of the fourth and fifth lumbar vertebrae. We aimed to define the function of the LSJ during weight transmission and clarify its mechanical significance. Vertebral columns of 45 adult male human cadavers from five anatomy departments in Nigeria were cut at the L3–L4 intervertebral disc and macerated. Using the graph paper method, the mean values of the surface area of the inferior body and total facet area of the fourth and fifth lumbar vertebrae were 1356 ± 26 and 329 ± 6 and 1277 ± 27 and 418 ± 8 mm2, respectively. The relationships between the fourth and fifth lumbar vertebrae paired variables were highly significant (P < 0.001). A sudden reduction in the surface area of the inferior body of the fifth lumbar vertebra was compensated for by a corresponding increase in its total inferior facet area, which indicated that corresponding weight was diverted from the anterior column to the posterior column at the LSJ. This pattern of weight transmission may be a beneficial functional adaptation in man to protect the relatively large intervertebral disc of the LSJ in bipedal posture, or it may predispose the LSJ synovial zygapophyseal joints to mechanical stress.
KeywordsLumbar vertebrae Mechanics Posture Sacrum Weight-bearing
We would like to thank Editage (www.editage.com) for English language editing. We thank Dr. G. Ndukwe and Dr. S. Danborno for granting us access to the facilities at the Gross Anatomy laboratory of Abia State University and Ahmadu Bello University, Zaria, respectively, and Dr. Felix Aguboshim for the statistical analysis of this work.
Compliance with ethical standards
Source of funding
There were no sponsorships or grants received in support of this study.
Conflict of interest
The authors declare that they have no conflict of interest.
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