Sagittal morphology and equilibrium of pelvis and spine

Abstract

A prospective analysis of the sagittal profile of 100 healthy young adult volunteers was carried out in order to evaluate the relationship between the shape of the pelvis and lumbar lordosis and to create a databank of the morphologic and positional parameters of the pelvis and spine in a normal healthy population. Inclusion criteria were as follows: no previous spinal surgery, no low back pain, no lower limb length inequality, no scoliotic deviation. For each subject, a 30 x 90-cm sagittal radiograph including spine, pelvis and proximal femurs in standing position on a force plate was performed. The global axis of gravity was determined with the force plate. Each radiograph was digitized using dedicated software. The spinal parameters registered were values for thoracic kyphosis and lumbar lordosis. The pelvic angles measured were: pelvic incidence, sacral slope and pelvic tilt. The global axis of gravity was on average 9 mm anterior of the center of the femoral heads. The anatomic parameter of pelvic incidence angle varied from 33 degrees to 85 degrees (mean: 51.7 degrees, SD: 11 degrees). The average lumbar lordosis was 46.5 degrees. The average thoracic kyphosis was 47 degrees. We found a statistical correlation between incidence angle and lumbar lordosis (r=0.69, P<0.001) and between sacral slope angle and lumbar lordosis (r=0.75, P<0.001). Spine and pelvis balance around the hip axis in order to position the gravity line over the femoral heads. We propose a scheme of sagittal balance of the standing human body.

The femoro-sacral posterior angle: an anatomical sagittal pelvic parameter usable with dome-shaped sacrum

“…We observed mean values for PI, SS, PT and lumbar lordosis similar to the values assessed as 'normal' firstly established by Duval-Beaupe`re and corroborated by several authors [3,14,[19][20][21]. The value for the pelvic incidence was provided as Fig.…”

“…The chain of close interdependence between the morphological (pelvic incidence, Jackson's angle and FSPA) and the positional pelvic parameters (sacral slope, pelvic tilting, angles SI and PA) was corroborated. The primordial correlation between the pelvic anatomical parameter 'pelvic incidence' and the positional parameter 'sacral slope' was similar to the reported coefficients (r=0.81-0.86) [14,20,21]. A similar relation was observed using the 'Jackson's angle PR-S1'.…”

Age- and sex-related variations in sagittal sacropelvic morphology and balance in asymptomatic adults

“…Parameters of sacropelvic balance and morphology ( Fig. 1) were then measured by a single observer with the Optispine software (Optispine, France), that has been presented in detail in previous studies of sagittal spinal alignment [32,33]. The pelvic incidence (PI) was measured in order to assess sacropelvic morphology.…”

Compensatory mechanisms contributing to keep the sagittal balance of the spine

“…This can be done optimally using strength plate and measuring positioning of the gravity axis in the sagittal plane [25]. However, in clinical practise, global balance is appreciated more simply by describing the relative positioning of the spine in reference with the pelvis on standing full spine radiographs.…”