Morphological differences between the facies articularis carpalis of distal radius in humans and chimpazees

Abstract

Introduction: In this study, we analyze the carpal articular surface of the radius in humans and chimpanzees, which is divided into two surfaces for the articulation of the lunate and scaphoid bones (facies articularis carpalis). The morphology of this articular surface is related to the different types of locomotion developed by hominoid primates. Our objective is to identify anatomical differences in the facies articularis carpalis between chimpanzees and humans to determine their relationship with their particular locomotion.
Material and methods: The analysis is characterized by a two 3D point-cloud mesh set across the two articular surfaces for the lunate and scaphoid bones with Geometric Morphometrics package. A total of 4.800 points were used as surface pseudo-landmarks to build a cloud mesh indicative of the topography and compare the articular surface of chimpanzees and humans. A total of 51 distal radius were studied: 31 belonging to Homo sapiens came from the Unit of Human Anatomy and Embryology of the University of Barcelona and 20 belonging to Pan troglodytes came from the Museum of Anatomy of the University of Valladolid.
Results: Significant differences were observed in the morphology of both articular surfaces between human and chimpanzee. The lunate articular showed the greatest variability (31,5%), being mainly represented by a greater width and a shorter surface length in the case of chimpanzees compared to humans. In the case of the articular surface of the scaphoid, the morphological variability between humans and chimpanzees was 26,9%. Chimpanzees showed a broader and more curved articular surface for the scaphoid bone compared to humans.
Conclusions: Chimpanzees and humans have a particular and differentiated pattern of the facies articularis carpalis and this feature may be related to their particular postural habit and locomotion.

Full text

1Unit of Human Anatomy and Embryology, University of Barcelona, Barcelona, Spain.
2Department of Anatomy and Radiology, University of Valladolid, Valladolid, Spain.
A. Casado1 , JM. Potau1, M.Gómez1, F. de Paz2, M. Barbosa2, JF. Pastor2
MORFOLOGICAL DIFFERENCES BETWEEN THE
FACIES ARTICULARIS CARPALIS OF DISTAL
RADIUS IN HUMANS AND CHIMPANZEES
This study was supported by the Ministerio de Economía y Competitividad of Spain (project CGL2014-52611-C2-2-P) and by the European Union (FEDER)
Contact email: aroa.casado@ub.edu
Introduction: In this study, we analyze the carpal articular surface of the radius (facies articularis carpalis) in humans and chimpanzees,
which is divided into two surfaces for the articulation of the lunate and scaphoid bones. The morphology of this articular surface is related to
the different types of locomotion developed by hominoid primates. Our objective is to identify anatomical differences in the facies articularis
carpalis between chimpanzees and humans to determine their relationship with their particular locomotion.
Material and methods: The analysis is characterized by atwo 3D point-cloud mesh set across the two articular surfaces for the lunate
and scaphoid bones using Geometric Morphometrics package. A total of 4.800 points were used as surface pseudo-landmarks to build a cloud
mesh indicative of the shape in order to compare the articular surface of chimpanzees and humans. A total of 51 distal radius were studied: 31
belonging to Homo sapiens came from the Unit of Human Anatomy and Embryology of the University of Barcelona and 20 belonging to Pan
troglodytes came from the Museum of Anatomy of the University of Valladolid.
Lunate articular surface Scaphoid articular surface
Results and conclusions: Significant differences were observed in the morphology of both articular surfaces between humans and
chimpanzees. The lunate articular surface showed the greatest variability (31,5%), being mainly represented by a greater expansion of the
transverse diameter in the dorsal area and a palmar reduction in the case of chimpanzees. In humans, we observed a longer sagittal diameter in
the lunate surface and less differences between its dorsal and palmar portions. In the case of the articular surface of the scaphoid, the
morphological variability between humans and chimpanzees was 26,9%. Chimpanzees showed a reduction of the transverse diameter and
height, while humans showed a radial expansion of the articular surface of the scaphoid. In conclusion, we can determine that the facies
articularis carpalis are stylized in humans to gain mobility, while in chimpanzees this surface is more compacted to gain resistance to the
pressure that is generated by knuckle-walking.
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