3D shape analyses of extant primate and fossil hominin vertebrae support the ancestral shape hypothesis for intervertebral disc herniation

The Application of 3D Imaging as an Appropriate Method of Wildlife Craniometry: Evaluation of Accuracy and Measurement Efficiency

The suitability of CT and 3D scanners for craniometric proposes was tested using digital calipers when determining linear measurements, and a measuring cylinder was used for the accuracy of 3D printing of deer antlers obtained by the CT and 3D scanners. The resolution of digitized objects from a 3D scanner ranged from 0.008 mm to 0.122 mm. For mandibular dimensions, a positive deviation (p < 0.01) from the primary control measurement was recorded. The average antler volume measured with the cylinder was 60.47 cm3 at the first measurement, in the case of the CT scanner 61.62 cm3 and for the 3D scanner 64.76 cm3—both technologies exhibit a positive deviation from the primary measurement. Precise sensing and measurements can be used to evaluate the quality and evolution of wildlife populations, create digital museum collections, or to examine in detail certain traits such as antler and horn development or dentition.

Morphological parameters of fourth lumbar spinous process palpation: a three-dimensional reconstruction of computed tomography

Background

The localization of lumbar fourth spinous process (L4-SP) is an important anatomical landmark, and identifying its accurate position is essential for the diagnosis and treatment of waist diseases.

Methods

Five hundred participants were scanned with positive and lateral computed tomography (CT), which aimed to clarify anatomic characteristics of L4-SP. Anatomical parameters of the surface localization of L4-SP were measured and recorded through a three-dimensional (3D) reconstruction.

Results

Five hundred participants were classified into three types according to the position of BC with the iliac spine. There are just 266 that the line between the highest point of the iliac spine on both sides located on L4-SP (type I, 53.20%), 16 above L4-SP (type II, 3.20%), and 218 below L4-SP (type III, 43.60%). BC in type I (15.92 ± 1.30 mm) is longer than type III (15.56 ± 1.32 mm). While the angle combined with AB and BC is different in the three groups, the angle in type I (173.00 ± 4.83°) is larger than that in type II (164.69 ± 5.50°) and type III (159.45 ± 8.39°). Other measurements were not found any significant differences between above.

Conclusion

The traditional palpation for L4-SP is not absolutely exact. The accuracy rate is only 53.20%, and the errors may cause serious consequences.

Spondylolysis and spinal adaptations for bipedalism: The overshoot hypothesis

Background and objectives

The study reported here focused on the aetiology of spondylolysis, a vertebral pathology usually caused by a fatigue fracture. The goal was to test the Overshoot Hypothesis, which proposes that people develop spondylolysis because their vertebral shape is at the highly derived end of the range of variation within Homo sapiens.

Methodology

We recorded 3D data on the final lumbar vertebrae of H. sapiens and three great ape species, and performed three analyses. First, we compared H. sapiens vertebrae with and without spondylolysis. Second, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae. Lastly, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae and to vertebrae of H. sapiens with Schmorl’s nodes, which previous studies have shown tend to be located at the ancestral end of the range of H. sapiens shape variation.

Results

We found that H. sapiens vertebrae with spondylolysis are significantly different in shape from healthy H. sapiens vertebrae. We also found that H. sapiens vertebrae with spondylolysis are more distant from great ape vertebrae than are healthy H. sapiens vertebrae. Lastly, we found that H. sapiens vertebrae with spondylolysis are at the opposite end of the range of shape variation than vertebrae with Schmorl’s nodes.

Conclusions

Our findings indicate that H. sapiens vertebrae with spondylolysis tend to exhibit highly derived traits and therefore support the Overshoot Hypothesis. Spondylolysis, it appears, is linked to our lineage’s evolutionary history, especially its shift from quadrupedalism to bipedalism.

Lay summary: Spondylolysis is a relatively common vertebral pathology usually caused by a fatigue fracture. There is reason to think that it might be connected with our lineage’s evolutionary shift from walking on all fours to walking on two legs. We tested this idea by comparing human vertebrae with and without spondylolysis to the vertebrae of great apes. Our results support the hypothesis. They suggest that people who experience spondylolysis have vertebrae with what are effectively exaggerated adaptations for bipedalism.