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Morphological and postural sexual dimorphism of the lumbar spine facilitates greater lordosis in females
Author(s) -
Bailey Jeannie F.,
Sparrey Carolyn J.,
Been Ella,
Kramer Patricia A.
Publication year - 2016
Publication title -
journal of anatomy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 118
eISSN - 1469-7580
pISSN - 0021-8782
DOI - 10.1111/joa.12451
Subject(s) - sexual dimorphism , lordosis , lumbar lordosis , anatomy , lumbar , lumbar spine , spine (molecular biology) , medicine , biology , physical medicine and rehabilitation , bioinformatics , zoology , surgery , radiography
Previous work suggests females are evolutionarily adapted to have greater lumbar lordosis than males to aid in pregnancy load‐bearing, but no consensus exists. To explore further sex‐differences in the lumbar spine, and to understand contradictions in the literature, we conducted a cross‐sectional retrospective study of sex‐differences in lumbar spine morphology and sacral orientation. In addition, our sample includes data for separate standing and supine samples of males and females to examine potential sex‐differences in postural loading on lumbosacral morphology. We measured sagittal lumbosacral morphology on 200 radiographs. Measurements include: lumbar angle (L1–S1), lumbar vertebral body and disc wedging angles, sacral slope and pelvic incidence. Lumbar angle, representative of lordotic curvature between L1 and S1, was 7.3° greater in females than males, when standing. There were no significant sex‐differences in lumbar angle when supine. This difference in standing lumbar angle can be explained by greater lordotic wedging of the lumbar vertebrae (L1–L5) in females. Additionally, sacral slope was greater in females than males, when standing. There were no significant sex‐differences in pelvic incidence. Our results support that females have greater lumbar lordosis than males when standing, but not when supine – suggesting a potentially greater range of motion in the female spine. Furthermore, sex‐differences in the lumbar spine appear to be supported by postural differences in sacral‐orientation and morphological differences in the vertebral body wedging. A better understanding of sex‐differences in lumbosacral morphology may explain sex‐differences in spinal conditions, as well as promote necessary sex‐specific treatments.