European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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Review Comparative Study
Biomechanical analysis of the spino-pelvic organization and adaptation in pathology.
Standing in an erect position is a human property. The pelvis anatomy and position, defined by the pelvis incidence, interact with the spinal organization in shape and position to regulate the sagittal balance between both the spine and pelvis. Sagittal balance of the human body may be defined by a setting of different parameters such as (a) pelvic parameters: pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS); (b) C7 positioning: spino-pelvic angle (SSA) and C7 plumb line; (c) shape of the spine: lumbar lordosis. ⋯ The genuine shape of the spine is probably one of the main mechanical factors of degenerative evolution. This shape is oriented by a shape pelvis parameter, the pelvis incidence. In case of pathology, this constant parameter is the only signature to determine the original spine shape we have to restore the balance of the patient.
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In L5-S1 spondylolisthesis, it has been clearly demonstrated over the past decade that sacro-pelvic morphology is abnormal and that it can be associated to an abnormal sacro-pelvic orientation as well as to a disturbed global sagittal balance of the spine. The purpose of this article is to review the work done within the Spinal Deformity Study Group (SDSG) over the past decade, which has led to a classification incorporating this recent knowledge. ⋯ The clinical relevance is that clinicians need to keep in mind when planning treatment that subjects with L5-S1 spondylolisthesis are a heterogeneous group with various adaptations of their posture. In the current controversy on whether high-grade deformities should or should not be reduced, it is suggested that reduction techniques should preferably be used in subjects with evidence of abnormal posture, in order to restore global spino-pelvic balance and improve the biomechanical environment for fusion.
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Aging of the spine is characterized by facet joints arthritis, degenerative disc disease and atrophy of extensor muscles resulting in a progressive kyphosis. Recent studies confirmed that patients with lumbar degenerative disease were characterized by an anterior sagittal imbalance, a loss of lumbar lordosis and an increase of pelvis tilt. The aim of this paper was thus to describe the different compensatory mechanisms which are observed in the spine, pelvis and/or lower limbs areas for patients with severe degenerative spine. ⋯ To avoid underestimate the severity of the degenerative spine disorder, it thus seems important to recognize the different compensatory mechanisms from the upper part of the trunk to the lower limbs. We propose a three steps algorithm to analyse the balance status and determine the presence or not of these compensatory mechanisms: measurement of pelvis incidence, assessment of global sagittal alignment and analysis of compensatory mechanisms successively in the spine, pelvis and lower limbs areas.
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The main objective of all the sagittal compensating mechanisms is to allow a subject to stand and keep an erect position. ⋯ Three questions to answer: What is the value of the pelvis incidence? Is the patient balanced? Are there compensatory mechanisms?
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The role of the pelvic area in sagittal balance is evident for spinal surgeons, but the influence of the coxofemoral joint is underestimated and inadequately explained by conventional imagery. Comprehensive analysis of the pelvic and subpelvic sectors as part of the sagittal, frontal and cross-sectional balance of the trunk sheds new light on some spinal diseases and their relation to the pelvis. ⋯ A comprehensive assessment of each patient and in particular of the complex comprising the spine and the pelvis, is essential for understanding each individual's adaptation to the imbalance induced by disorders of the spine or lower limbs.