Study design Current concepts review. Objective Outline the basic principles in the evaluation and treatment of adult spinal deformity patients with a focus on goals to achieve during surgical realignment surgery. Summary of background data Proper global alignment of the spine is critical in maintaining standing posture and balance in an efficient and pain-free manner. Outcomes data demonstrate the clinical effect of spinopelvic malalignment and form a basis for realignment strategies. Methods Correlation between certain radiographic parameters and patient self-reported pain and disability has been established. Using normative values for several important spinopelvic parameters (including sagittal vertical axis, pelvic tilt, and lumbar lordosis), spinopelvic radiographic realignment objectives were identified as a tool for clinical application. Because of the complex relationship between the spine and the pelvis in maintaining posture and the wide range of "normal" values for the associated parameters, a focus on global alignment, with proportionality of individual parameters to each other, was pursued to provide clinical relevance to planning realignment for deformity across a range of clinical cases. Conclusion Good clinical outcome requires achieving proper spinopelvic alignment in the treatment of adult spinal deformity. Although variations in pelvic morphology exist, a framework has been established to determine ideal values for regional and global parameter in an individualized patient approach. When planning realignment surgery for adult spinal deformity, restoring low sagittal vertical axis and pelvic tilt values are critical goals, and should be combined with proportional lumbar lordosis to pelvic incidence.

Adult spinal deformity-postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery.

Pelvis and spinal curves were studied with an angular parameter typical of pelvis morphology: pelvic incidence. A significant chain of correlations between positional pelvic and spinal parameters and incidence is known. This study investigated standards of incidence and a predictive equation of lordosis from selective pelvic and spinal individual parameters. One hundred and forty nine (78 men and 71 women) healthy adults, aged 19–50 years, with no spinal disorders, were included and had a full-spine lateral X-ray in a standardised upright position. Computerised technology was used for the measurement of angular parameters. Mean-deviation section of each parameter and Pearson correlation test were calculated. A multivariate selection algorithm was running with the lordosis (predicted variable) and the other spinal and pelvic parameters (predictor variables), to determine the best sets of predictors to include in the model. A low incidence ( 62°) increased sacral-slope and the lordosis is more pronounced. Lordosis predictive equation is based on incidence, kyphosis, sacral-slope and ±T9 tilt. The confidence limits and the residuals (the difference between measured and predicted lordosis) assessed the predicted lordosis accuracy of the model: respectively, ±1.65 and 2.41° with the 4-item model; ±1.73 and 3.62° with the 3-item model. The ability of the functional spine-pelvis unit to search for a sagittal balance depended both on the incidence and on the variation section of the other positional parameters. Incidence gave an adaptation potential at two levels of positional compensation: overlying state (kyphosis, T9 tilt), underlying state (sacral slope, pelvic tilt). The biomechanical and clinical conditions of the standing posture (as in scoliosis, low back pain, spondylisthesis, spine surgery, obesity and postural impairments) can be studied by comparing the measured lordosis with the predicted lordosis.

Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis

Study Design. Research update, focused review. Objective. identify the role of the pelvis in the setting of adults with spinal deformity. Summary of Background Data. Sagittal plane alignment is increasingly recognized as a critical parameter in the setting of adult spinal deformity. Additionally, pelvic parameters reveal to be a key component in the regulation of sagittal alignment. Methods. Analysis of the pelvis in the sagittal plane is commonly assessed by 3 angular measurements: the pelvic incidence (morphologic parameter directly linked to sagittal morphotypes), the pelvic tilt (or pelvis retroversion used to maintain an upright posture in the setting of spinal deformity), and the sacral slope. Recent work using force plate technology has revealed that in the setting of anterior trunk inclination ("spinal imbalance"), the pelvis shifted posteriorly (toward the heels) in order to maintain a balanced mass distribution. The complex relationship between pelvic and spinal parameter were investigated in order to construct predictive formulas of postoperative spinopelvic alignment. It has emerged that pelvic tilt is highly correlated with patient self reported function (ODI, SF-12, and SRS). Conclusion. It has become evident that good clinical outcome in the treatment of spinal deformity requires proper alignment. Pelvis parameters play an essential role not only in terms of spine morphotypes but also in regulating standing balance and postoperative alignment. Thus, optimal treatment of a patient with spinal deformity requires integration of the pelvis in the preoperative evaluation and treatment plan.

Sagittal plane considerations and the pelvis in the adult patient.

STUDY DESIGN Prospective study of the sagittal plane alignment of the spine and pelvis in the normal pediatric population. OBJECTIVES To document the sagittal alignment of the spine and pelvis and its change during growth in the normal pediatric population. SUMMARY OF BACKGROUND DATA Pelvic morphology as well as sagittal alignment of the spine and pelvis in the pediatric population are poorly defined in the literature. METHODS Five parameters were evaluated on lateral standing radiographs of 180 normal study participants 4 to 18 years of age: thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. Statistical analysis was performed using two-tailed Student t tests and Pearson's coefficients (level of significance = 0.01). RESULTS The mean thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence values were 43.0 degrees, 48.5 degrees, 41.2 degrees, 7.2 degrees and 48.4 degrees, respectively. There was no significant difference between males and females. Thoracic kyphosis, lumbar lordosis, pelvic tilt, and pelvic incidence were found to be weakly correlated with age, while sacral slope remained stable with growth. CONCLUSIONS Pelvic morphology, as measured by the pelvic incidence angle, tends to increase during childhood and adolescence before stabilizing into adulthood, most likely to maintain an adequate sagittal balance in view of the physiologic and morphologic changes occurring during growth. Pelvic tilt and lumbar lordosis, two position-dependent parameters, also react by increasing with age, most likely to avoid inadequate anterior displacement of the body center of gravity. Sacral slope is achieved with the standing posture and is not further significantly influenced by age. These results are important to establish baseline values for these measurements in the pediatric population, in view of the reported association between pelvic morphology and the development of various spinal disorders such as spondylolisthesis and scoliosis.

Sagittal alignment of the spine and pelvis during growth.

Study design Prospective radiographic and forceplate analysis in adult volunteers. Objective Assess gravity line (GL) location and foot position regarding anatomic spinal structures to evaluate key correlations and age-related changes in balance. Summary of background data Global spinal balance is commonly assessed by the C7 plumbline. This radiographic parameter does not offer information on foot position or forces transmitted, and poor correlation with the true GL has been demonstrated. Methods A total of 75 asymptomatic adult volunteers were equally distributed into three age groups. Full length, free-standing spine radiographs were obtained with simultaneous acquisition of GL and feet location (forceplate). GL and heels were projected on each radiograph to compute their distance from anatomic entities and to investigate correlations with radiologic parameters and age-related changes. Results In this study group, advancing age led to a significant increase in thoracic kyphosis. The plumbline from C7 shifted anteriorly with age. In the sagittal plane, the GL was anterior to the vertebral column for all groups. With age, the GL location regarding the heels remained constant, while the pelvis moved posteriorly toward the heels and underwent a small retroversion (increasing pelvic tilt). The acetabulum was the most reliable radiographic marker of the GL location. Conclusions This quantitative study in volunteers reveals clear age-related changes in the spino-pelvic association and offers quantitative support to the "cone of economy" concept proposed by Dubousset. The pelvis can be seen as a regulator to help maintain a rather fixed GL-heel association with age-related changes in the spinal column. Further study in patients suffering from deformity can confirm the importance of radiographic-gravity line correlations and enhance our understanding of optimal balance.

Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position.

The anatomic pelvic parameter "incidence" – the angle between the line perpendicular to the middle of the sacral plate and the line joining the middle of the sacral plate to the center of the bicoxo-femoral axis – has been shown to be strongly correlated with the sacral slope and lumbar lordosis, and ensures the individual an economical standing position. It is important for determining the sagittal curve of the spine. The angle of incidence has also been shown to depend partly on the sagittal anatomy of sacrum, which is established in childhood while learning to stand and walk. The purpose of this study was (1) to define the relationship between the sacrum and the angle of incidence, and (2) to compare these parameters in three populations: young adults, infants before walking, and patients with spondylolisthesis. Forty-four normal young adults, 32 infants not yet walking and 39 patients with spondylolisthesis due to isthmic spondylolysis underwent a sagittal full-spine radiography. A graphic table and the software for bidimensional study of the sacrum developed by J. Hecquet were used to determine various anatomic and positional parameters. Comparison tests of means, and multiple and partial correlation tests were used. A study of the reliability of the measurements using factorial plan methods was performed. The sagittal anatomic parameters of the sacrum were found to have a close relationship with the pelvic parameter of incidence angle, and therefore with the sagittal balance of the spine. The anatomy of the sacrum in spondylolisthesis patients is particular in that some features are much like those of young infants, but it is more curved and the incidence angle is significantly larger. There is a close relationship between angle of incidence and the slip of spondylolisthesis. All the parameters of young infants are significantly smaller than those of adults. It can be concluded that the sagittal anatomy of the sacrum plays a key role in spinal sagittal balance. The sacral bone is an integral a part of the pelvis and constitutes the undistorted part of the spinal curves. Organization of sagittal curves during growth can be followed up by looking at the sacrum. The sacrum in the spondylolisthesis group differs from the normal, and the greater angle of incidence and sacral slope in this group could predispose to vertebral slip.

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The sagittal anatomy of the sacrum among young adults, infants, and spondylolisthesis patients

Sagittal profile of the spine prominent part of the pelvis.

Les auteurs rappellent que les variations individuelles des parametres pelviens positionnels du bassin et des courbures rachidiennes sagittales sont conditionnees par un parametre pelvien anatomique fondamental nomme Incidence. Compte tenu du fait que la morphologie du squelette evolue de la naissance a la maturite, les auteurs se proposent d'amorcer une etude sur les modifications de l'Incidence et de ses rapports avec les autres parametres au cours de la croissance. L'Incidence est significativement plus faible chez le petit enfant et il est etroitement correle aux parametres positionnels du bassin et aux courbures rachidiennes sagittales, mais de facon moins intense que chez l'adulte.

Le paramètre pelvien : Incidence chez le petit enfant

Les auteurs ont etudie l'anatomie sagittale du sacrum grâce aux radiographies et au logiciel Rachis 91 de J. Hecquet. Nous avons demontre qu'il existe des correlations tres significatives entre les parametres anatomiques sacres et le parametre anatomique pelvien: l'Incidence. Ainsi le sacrum joue un role important dans l'equilibre sagittal du rachis dans la position debout.

H. Descamps

Papers

The sagittal anatomy of the sacrum among young adults, infants, and spondylolisthesis patients

Sagittal profile of the spine prominent part of the pelvis.

Le paramètre pelvien : Incidence chez le petit enfant

Sacrum et incidence : Quelles relations

Modifications des angles pelviens, dont l'incidence, au cours de la croissance humaine