TY - JOUR
T1 - A three-dimensional analysis of bilateral directional asymmetry in the human clavicle
AU - Abdel Fatah, Emam Elhak
AU - Shirley, Natalie R.
AU - Mahfouz, Mohamed R.
AU - Auerbach, Benjamin M.
PY - 2012/12
Y1 - 2012/12
N2 - This study presents a novel three-dimensional analysis using statistical atlases and automated measurements to assess diaphyseal morphology of the clavicle and its relationship to muscle asymmetry. A sample of 505 individuals (285 males, 220 females) from the William McCormick Clavicle Collection was CT scanned, segmented, and added to a statistical bone atlas that captures correspondence between homologous points on the bone surfaces. Muscle attachment sites were localized on the atlas and then propagated across the entire population. Cross-sectional contours were extracted at 5% increments along the entire bone, as well as at muscle attachment sites and the clavicle waist; maximum and minimum dimensions of each cross-sectional contour were calculated. In addition, the entire three-dimensional surface was examined for asymmetry by analyzing the magnitude and directional differences between homologous points across all bone surfaces in the dataset. The results confirm the existing studies on clavicle asymmetry, namely that the left clavicle is longer than the right, but the right is more robust than the left. However, the patterns of asymmetry are sexually dimorphic. Males are significantly asymmetric in all dimensions and at muscle and ligament attachment sites (P < 0.05), whereas female asymmetry is more variable. We hypothesize that this is related to absolute and relative differences in male muscle strength compared to females. However, an area with no muscle attachments on the posterior midshaft was significantly asymmetric in both sexes. We suggest that this is a curvature difference caused by opposing muscle actions at the medial and lateral ends of the bone. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.
AB - This study presents a novel three-dimensional analysis using statistical atlases and automated measurements to assess diaphyseal morphology of the clavicle and its relationship to muscle asymmetry. A sample of 505 individuals (285 males, 220 females) from the William McCormick Clavicle Collection was CT scanned, segmented, and added to a statistical bone atlas that captures correspondence between homologous points on the bone surfaces. Muscle attachment sites were localized on the atlas and then propagated across the entire population. Cross-sectional contours were extracted at 5% increments along the entire bone, as well as at muscle attachment sites and the clavicle waist; maximum and minimum dimensions of each cross-sectional contour were calculated. In addition, the entire three-dimensional surface was examined for asymmetry by analyzing the magnitude and directional differences between homologous points across all bone surfaces in the dataset. The results confirm the existing studies on clavicle asymmetry, namely that the left clavicle is longer than the right, but the right is more robust than the left. However, the patterns of asymmetry are sexually dimorphic. Males are significantly asymmetric in all dimensions and at muscle and ligament attachment sites (P < 0.05), whereas female asymmetry is more variable. We hypothesize that this is related to absolute and relative differences in male muscle strength compared to females. However, an area with no muscle attachments on the posterior midshaft was significantly asymmetric in both sexes. We suggest that this is a curvature difference caused by opposing muscle actions at the medial and lateral ends of the bone. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.
KW - computed tomography scans
KW - computer-automated bone measurements
KW - morphological variation
KW - muscle attachment
KW - statistical bone atlas
UR - http://www.scopus.com/inward/record.url?scp=84869508629&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84869508629&partnerID=8YFLogxK
U2 - 10.1002/ajpa.22156
DO - 10.1002/ajpa.22156
M3 - Article
C2 - 23077031
AN - SCOPUS:84869508629
SN - 0002-9483
VL - 149
SP - 547
EP - 559
JO - American Journal of Physical Anthropology
JF - American Journal of Physical Anthropology
IS - 4
ER -