Sagittal imbalance cascade for simple degenerative spine and consequences: algorithm of decision for appropriate treatment

Abstract

Introduction The main objective of all the sagittal compensating mechanisms is to allow a subject to stand and keep an erect position. Materials and methods The cascade of compensating mechanisms appears progressively with the increasing amount of imbalance of the spine until compensation is no longer possible. The loss of lumbar lordosis can be considered as the initiating event of sagittal imbalance. This loss of the normal lordosis pushes the C7 plumb line forward. Results The assessment of sagittal balance has to include to be complete: a parameter measuring the global balance of the trunk, either C7 plumb line and sacral plateau, the position of the pelvis rotation by the pelvic tilt, and a description of the position of the lower limbs. Those three parameters have been taken into account by the newly described method called full balance integrated (FBI). This evaluation is easily done on a sagittal full spine standing X-ray from C2 to the pelvis, including the first 10 cm of the femur. Conclusion Three questions to answer: What is the value of the pelvis incidence? Is the patient balanced? Are there compensatory mechanisms?

Normative values of spino-pelvic sagittal alignment, balance, age, and health-related quality of life in a cohort of healthy adult subjects

“…Itoi et al [37] investigated the relationship between sagittal posture of the spine and the lower extremities in osteoporotic subjects, and found that thoracic kyphosis, a primary deformity, was compensated for by the lumbar spine, sacroiliac joint, hip joint, and knee joint. Another study suggested that upright posture is secondary to hip extension and LL, and an optimal and economic standing posture is obtained when these two parameters are balanced [8]. These reports suggest that lower extremities are also crucial factors for standing balance.…”

“…Based on conventional X-ray, Schwab et al reported that pelvic tilt (PT), pelvic incidence (PI), and lumbar lordosis (LL) combined with the sagittal vertical axis (SVA) predict disability, and proposed threshold values for severe disability [Oswestry Disability Index (ODI) [40] including: PT C22°, SVA C47 mm, and PI-LL C11° [7]. In case of decompensated standing balance, the trunk shows an increased SVA, the pelvis retroversed, the hip extended, and the knee flexed, suggesting the uneconomic alignment affects HRQOL [1,8]. Therefore, a better understanding of alignment from the head to the feet will elucidate the ''cone of economy'' mechanism.…”

Sagittal balance of the cervical spine: an analysis of occipitocervical and spinopelvic interdependence, with C-7 slope as a marker of cervical and spinopelvic alignment

“…The overall sagittal balance of the thoracolumbar and lumbosacral spine is expected to influence the cervical spine, which should be the last regulator of the compensatory cascade, which starts at the pelvic region and aims to maintain overall balance. 13,19 Studies of the treatment of idiopathic scoliosis in adolescents have shown that loss of thoracic kyphosis as a result of surgical coronal plane correction of the scoliosis is associated with a postoperative increase in cervical kyphosis. 1,6,7 Studies of sagittal alignment include either occipitocervical or thoracolumbopelvic regions, but limited data regarding the connection of these regions are available.…”

3D point cloud in the evaluation of processes that generate instability of the lumbar spine

“…Evaluation of sagittal balance must include a parameter to measure the overall equilibrium of the trunk, i.e., the plumb line in C7 and the sacral plateau, the position of pelvic rotation when bending the pelvis, and a description of the position of the lower limbs. These three parameters were considered by Le Huec et al 8 in their assessment method known as full balance integration (FBI). 8,20 In more severely unbalanced cases, patients present all the signs of postural changes in an attempt to compensate for sagittal imbalance: the trunk leaning forward, retroversion of the pelvis, and apparent flexion, while in reality, there is extension of the hips and flexion of the knees.…”

“…4 As a result of degeneration and instability, there is a gradual loss of sagittal balance that begins with a decrease in the height of the intervertebral disc and a cascade of compensatory mechanisms in which changes occur in the position of the hips, pelvis and knees, in order to restore sagittal balance to a neutral position, [5][6][7] enabling a plumb line from C7 to remain, clinically, between both malleoli. 8 But this situation is not profitable because, as measured electromyographically, more muscular energy is required to maintain this position, causing low back pain 9 and inevitably leading to imbalance in the sagittal plane.…”