Pelvic parameters: origin and significance

Abstract

Introduction The adoption by humans of an upright position resulted in broadening and verticalisation of the pelvis together with the appearance of characteristic spinal curves, has profoundly modified the structure of the muscles supporting the spine. Material In order to characterise the sagittal balance of the pelvis, it is necessary to define parameters based on notable biomechanical forces involved in the transmission of constraints. The angle of incidence was constructed to enable reproducible analysis of the anatomical characteristics of the pelvis in the sagittal plane. The angle of incidence is the algebraic sum of two complementary angles: pelvic tilt (PT) and sacral slope (SS). Since the value of incidence is fixed for any given patient, the sum of pelvic tilt and sacral slope is a constant value: when one increases, the other necessarily decreases. Result The position of the lumbar spine, attached to the sacral plateau, is thus affected by the pelvic tilt and by the sacral slope. Consequently, the pelvic parameters affect the entire underlying sagittal spinal profile. Conclusion Global spinal balance involves harmonisation of lumbar lordosis and thoracic kyphosis taking into account the pelvic parameters.

Comparison of radiographic sagittal spinopelvic alignment between skeletally immature and skeletally mature individuals with Scheuermann’s disease

“…When the natural reserve of increasing LL is maximized, any further compensation for the increasing TK or TLK may be accomplished by posterior tilting of the pelvis that decreases SS and with fixed PI increases PT. Increased PT that results in a posterior shift of the center of gravity in relation to the hip joints is biomechanically disadvantageous [33][34][35]. We suspect that in a growing individual, it can result in modification of the pelvis shape, so the PT increase is prevented.…”

Three-dimensional pelvic incidence is much higher in (thoraco)lumbar scoliosis than in controls

“…Several other authors described the spino-pelvic balance in normal children and adolescents during growth and in patients with different pathologies [1,[10][11][12][13][14][15][16][17][18][19][20][21]. Dickson et al [5] described that differences in the sagittal plane (reversal of the normal thoracic kyphosis) during growth could initiate a progressive idiopathic scoliosis.…”

Comparison of Lumbar Lordosis in Lateral Radiographs in Standing Position with supine MR Imaging in consideration of the Sacral Slope

“…Indeed, surgical correction of lumbar lordosis must be proportional to pelvic incidence (PI) [1,2]. Reference data of asymptomatic patients may be helpful to understand individual disease progression, to achieve goals of movement therapies, and to improve the quality of monitoring therapies [3].…”