Morphological and postural sexual dimorphism of the lumbar spine facilitates greater lordosis in females

Abstract

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.

Statistical shape modelling of hip and lumbar spine morphology and their relationship in the MRC National Survey of Health and Development

“…While the shape of the hips may be less affected between standing and lying, the shape of the spine changes measurably on going from standing to supine. This conclusion is supported by a recent study of 200 individuals which found a significantly larger lordosis angle in women than men while standing but not while lying supine (Bailey et al 2016). Although in previous studies we showed that an element of an intrinsic shape can still be identified between these postures (Meakin et al 2009), more associations between joint shapes may be evident in the natural weight-bearing position.…”

“…This conclusion is supported by a recent study of 200 individuals which found a significantly larger lordosis angle in women than men while standing but not while lying supine (Bailey et al. ). Although in previous studies we showed that an element of an intrinsic shape can still be identified between these postures (Meakin et al.…”

“…Many studies of joint morphology are limited by their sample number (n = 9-800) (Cil et al 2005;Bailey et al 2016), geometrical (Masharawi et al 2012;Shefi et al 2013) or external measurement methods (Wojtys et al 2000) and often lack heterogeneity in terms of health and disease state in their cohorts. Here we use data from the Medical Research Council (MRC) National Survey of Health and Development (NSHD), the oldest of the British birth cohort studies, to investigate the variations in hip and spine shapes in over 1500 individuals approaching early old age.…”

Trends in Incidence and Treatment of Herniated Lumbar Disc in Republic of Korea : A Nationwide Database Study

“…With improvements in advanced imaging techniques, HLD has been increasingly recognized in symptomatic and asymptomatic individuals 2) . Pre-vious work suggests lumbar lordosis, representative of lordotic curvature between L1 and S1, was 7.3° greater in females than males when standing 1) . Additionally, the sacral slope was greater in females than males, when standing.…”

Testing biomechanical models of human lumbar lordosis variability

“…Understanding the structural and functional bases for lordosis variation is a challenge because the alignment of the spine and balance of the upper body are influenced by several inter‐related factors. For instance, LL is mechanically linked to other spinal postural parameters such as thoracic kyphosis, pelvic orientation, and sacral incidence (Bailey et al, ; Vialle et al, ). Several non‐mechanical factors have also been shown to be associated with LL including individual factors such as age, sex, height, and body mass; genetic factors influencing heritability; and environmental factors such as occupational loading, athletic training, and physical fitness (for review, see Been and Kalichman, ).…”