Incidence of osteosynthesis of members in France.

PURPOSE: Little data is available on the number of osteosynthesis of limbs in a country. Incidence of osteosynthesis is an essential element for the formation and organization of care. Based on the data from the work of the Hospital Information Technology Agency ( http://www.atih.sante.fr/ ) and available in open access, we wanted to know the incidence of the number of osteosynthesis performed in France and their evolution over ten years between 2006 and 2015. METHODS: The data analyzed are derived from the website of the technical agency of information on the hospitalization (ATIH). RESULTS AND CONCLUSIONS: In France, in 2015, 267,999 limb osteosyntheses were performed. Between 2006 and 2015, the number of osteosynthesis increased by 9.1%. The incidence of limb osteosynthesis is 403.7 per 100,000 people, rising 3.9% between 2006 and 2015. In comparison, the incidence of hip prostheses increased by 12.6%, knee prosthesis by 57.4%. The main bias of the study is of course the quality of the coding of the surgeons and the establishments, a type of fracture that can enter into one or several categories of acts. In ten years, the incidence of osteosynthesis has increased little in France. The evolution is more pronounced on fractures affecting mainly the elderly, fracture of the upper end of the femur, fracture of the distal end of the radius and fracture of the ankle. The incidence of many acts of osteosynthesis is very low and therefore responsible for a weak experience for most surgeons.

Normal sagittal parameters of global spinal balance in children and adolescents: a prospective study of 646 asymptomatic subjects.

PURPOSE: To document values for parameters of global spinal balance in asymptomatic children and adolescents. METHODS: Multicenter prospective study of normal sagittal global spinal balance in Caucasian children and adolescents. Spinosacral angle (SSA), spinal tilt (ST), and C7 translation ratio were evaluated in 646 asymptomatic children and adolescents (276 males and 370 females). RESULTS: Mean and standard deviation for SSA, ST, and C7 translation ratio were, respectively 132.1° ± 8.3°, 93.2° ± 4.6° and -0.7 ± 8.3. Mean ± 2 standard deviations were, respectively 116°-149° for SSA and 84°-102° for ST. C7 plumbline was behind the HA (hip axis) in 78 % of subjects. Correlations between global balance and age were small (-0.17 ≤ r ≤ 0.19). CONCLUSION: Asymptomatic children and adolescents tend to stand with a stable global balance, and 95 % have an SSA and ST between 116° and 149° and 85°-102°, respectively. C7 plumbline in front of the HA is not necessarily associated with a spinal pathology.

The use of a photogrammetric method for the three-dimensional evaluation of spinal correction in scoliosis.

PURPOSE: Clinical parameters, characterizing the spinal deformations due to scoliosis, are still directly measured on the spinal curve plane projections. METHODS: A 3D spinal curve has been reconstructed from its two projections, using photogrammetric techniques. Each spinal curve is a compound of several plane regions, where it is purely flexed, and short zones of connection, where abduction and axial rotation components are concentrated. All spinal curves are represented as linear chains of regional planes articulated together. The regional plane is represented by a triangle, where one summit corresponds to the point of maximum offset. The set of weight forces, representing pelvis and spine, forms a bundle of vertical forces. The dispersion of the bundle illustrates the postural stability of patients. RESULTS AND CONCLUSIONS: The first objective was to numerically describe the changes of the 3D spinal feature, due to the correcting treatment. Changes are calculated from the comparison between 3D radiologic situations, between before and after treatment. The second objective was to determine the direction of the external force, which would be the most efficient for correcting the patient set spine/rib cage. A mild mechanical analysis is proposed, for representing the transit of the external force, from rib cage to thoracic regional plane.

Sagittal spino-pelvic alignment in chronic low back pain.

INTRODUCTION: The differences in sagittal spino-pelvic alignment between adults with chronic low back pain (LBP) and the normal population are still poorly understood. In particular, it is still unknown if particular patterns of sagittal spino-pelvic alignment are more prevalent in chronic LBP. The current study helps to better understand the relationship between sagittal alignment and low back pain. MATERIALS AND METHODS: To compare the sagittal spino-pelvic alignment of patients with chronic LBP with a cohort of asymptomatic adults. Sagittal spino-pelvic alignment was evaluated in prospective cohorts of 198 patients with chronic LBP and 709 normal subjects. The two cohorts were compared with respect to the sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), lumbar tilt (LT), lordotic levels, thoracic kyphosis (TK), thoracic tilt (TT), kyphotic levels, and lumbosacral joint angle (LSA). Correlations between parameters were also assessed. RESULTS: Sagittal spino-pelvic alignment is significantly different in chronic LBP with respect to SS, PI, LT, lordotic levels, TK, TT and LSA, but not PT, LL, and kyphotic levels. Correlations between parameters were similar for the two cohorts. As compared to normal adults, a greater proportion of patients with LBP presented low SS and LL associated with a small PI, while a greater proportion of normal subjects presented normal or high SS associated with normal or high PI. CONCLUSION: Sagittal spino-pelvic alignment was different between patients with chronic LBP and controls. In particular, there was a greater proportion of chronic LBP patients with low SS, low LL and small PI, suggesting the relationship between this specific pattern and the presence of chronic LBP.

Impact of an ergonomic seat on the stand-to-sit strategy in healthy subjects: Spinal and lower limbs kinematics.

PURPOSE: To assess differences in spinal, pelvic and lower limb parameters in healthy individuals during a stand-to-sit task using three different seating conditions. METHODS: Ten healthy adults carried out three stand-to-sit movements on different stools: a high ergonomic stool with the seat tilted 10° forward; a standard stool (adjusted to the same height as the ergonomic stool) and a standard stool at a lower level (so their thighs were horizontal). Movements were recorded by an optoelectronic Vicon system. RESULTS: Hip flexion was altered by the height of the seat (significantly greater for the low standard stool in comparison to either the ergonomic stool or the high standard stool (p < 0.0001)). There was also significantly less knee flexion with the ergonomic stool in comparison to the low standard stool (p < 0.0001) and to the high standard stool (p = 0.0017). Lumbar lordosis was not significantly altered by seat height, although it was less pronounced with the ergonomic stool, with a significantly higher range of motion for the pelvis (p = 0.015). At the thoracic level, no differences were observed, except that the stand-to-sit movement on the lower stool produced greater flexion. CONCLUSION: Lumbar lordosis was not increased by the ergonomic stool and the range of lower limb motion was reduced by the high seat. These findings contrast with current opinion that ergonomic seats promote lumbar lordosis.

Spino-pelvic alignment after surgical correction for developmental spondylolisthesis.

This study is a retrospective multi-centre analysis of changes in spino-pelvic sagittal alignment after surgical correction of L5-S1 developmental spondylolisthesis. The purpose of this study was to determine how sagittal spino-pelvic alignment is affected by surgery, with the hypothesis that surgical correction at the lumbo-sacral level is associated with an improvement in the shape of the spine and in the orientation of the pelvis. Whether L5-S1 high grade spondylolisthesis should or should not be reduced remains a controversial subject. A popular method of treatment has been in situ fusion, but studies have reported a high rate of pseudarthrosis, slip progression and persistent cosmetic deformity. Spinal instrumentation with pedicle screws has generated a renewed interest for reduction, but the indications for this treatment and its effect on spino-pelvic alignment remain poorly defined. Recent evidence indicates that reduction might be indicated for subjects with an unbalanced (retroverted or vertical) pelvis. This is a retrospective multi-centre analysis of 73 subjects (mean age 18 +/- 3 years) with developmental spondylolisthesis and an average follow-up of 1.9 years after reduction and posterior fusion with spinal instrumentation or cast immobilisation. Spinal and pelvic alignment were measured on standing lateral digitised X-rays using a computer software allowing a very high inter and intra observer reliability. Pelvic incidence was unaffected by surgery. The most important changes were noted for grade, L5 Incidence, lumbo-sacral-angle, and lumbar lordosis, which all decreased significantly towards normal adult values. At first evaluation, pelvic tilt, sacral slope and thoracic kyphosis appeared minimally affected by surgery. However, after classifying subjects into balanced and unbalanced pelvis, significant improvements were noted in pelvic alignment in both the sub-groups, with 40% of cases switching groups, the majority from an unbalanced to a balanced pelvis alignment. The direction and magnitude of these changes were significantly different by sub-group: sacral slope decreased in the balanced pelvis group but increased in the unbalanced group, while pelvic tilt values did the opposite. While pelvic shape is unaffected by attempts at surgical reduction, proper repositioning of L5 over S1 significantly improves pelvic balance and lumbar shape by decreasing the abnormally high lumbar lordosis and abnormal pelvic retroversion. These results emphasise the importance of sub-dividing subjects with high grade developmental spondylolisthesis into unbalanced and balanced pelvis groups, and further support the contention that reduction techniques might be considered for the unbalanced retroverted pelvis sub-group.

Forefoot morphotype study and planning method for forefoot osteotomy.

In the reconstruction of the hip, knee, or any other joint, preoperative planning is necessary for avoiding mistakes during surgery. Since 1995, the authors have been doing this before forefoot surgery to increase the accuracy of the surgery. As much as possible, they try to correct only the lesion and to avoid preventive or extensive surgery on adjacent rays, except if the correction leads to a modified dysharmonious new morphotype with high risk of transfer lesion. The tolerance length seems to be 2 mm, particularly on the middle metatarsals (M2 and M3). This surgery should be performed only if the midfoot and backfoot are correct and if the gastrocnemius muscle has been checked on to eliminate a retraction needing stretching exercises before and generally after surgery.

Spondylolisthesis: Intra-rater and Inter-rater Reliabilities of Radiographic Sagittal Spinopelvic Parameters Using Standard Picture Archiving and Communication System Measurement Tools.

STUDY DESIGN: Reliability analysis. OBJECTIVE: To determine the intra-rater and inter-rater reliability of common sagittal spinopelvic measurements from Digital Imaging and Communications in Medicine images on a commercial Picture Archiving and Communication system for patients with developmental spondylolisthesis. SUMMARY OF BACKGROUND DATA: Computer-aided analysis of digital radiographs has been used in research protocols to define anatomic and positional characteristics of developmental spondylolisthesis. Previous studies have shown poor reliability and weak correlations of manual measurements used in clinical practice with research measurements, which limit the clinical value of prior research. METHODS: Five raters of varying experience measured lateral spinopelvic images of 30 patients with developmental spondylolisthesis. Measurements were repeated after 1 week. Intra-rater and inter-rater reliabilities for each measurement were determined. Measurements were compared with those obtained from a computer-based image enhancement research system. Continuous variables were assessed by analysis of variance, whereas kappa statistics were determined for categorical variables. RESULTS: Excellent intraclass correlations (ICC)s were obtained for all radiographic measurements based on linear values (slip ratio and C7 balance) as well as pelvic tilt angle. Angular measurements had good to excellent ICC but were weaker when the sacral plate was involved. There was poor agreement with classification of sacral doming. Some measurements had reduced reliability in the images with evidence of doming. CONCLUSIONS: Excellent ICCs were found with measurements of from Digital Imaging and Communications in Medicine images using commercial Picture Archiving and Communication System tools. Sacral doming affected the reliability. A radiographic classification of spondylolisthesis will be most reliable when based on slip ratio, C7 balance, and pelvic tilt.

Sagittal parameters of global spinal balance: normative values from a prospective cohort of seven hundred nine Caucasian asymptomatic adults.

STUDY DESIGN: Prospective study of normal sagittal global spinal balance in the Caucasian adult population. OBJECTIVE: To document values for parameters of global spinal balance in 709 asymptomatic adults without spinal pathology. SUMMARY OF BACKGROUND DATA: Previous studies have investigated sagittal spinal balance in the normal population, but there is still a need for a large prospective database with normative values on the basis of gender and age. METHODS: Spinosacral angle (SSA), spinal tilt (ST), and C7 translation ratio were evaluated in 709 asymptomatic adults (354 males and 355 females). Position of C7 plumbline relative to sacrum and hip axis (HA) was also assessed. Comparisons on the basis of gender were performed using analyses of covariance with age as covariate. Relationships between parameters and age were assessed using Spearman's coefficients. RESULTS: Mean SSA, ST, and C7 translation ratio were respectively 130.4° ± 8.1°, 90.8° ± 3.4°, and 0.1° ± 1.9°. Mean ± 2 standard deviations were respectively 110° to 150° for SSA and 85° to 100° for ST. Mean SSA and ST were higher in females but by less than 2°. C7 plumbline was behind the HA in 86% of subjects. Correlations between global balance and age were small (-0.1 ≤ r ≤ 0.1), with only 1 correlation reaching statistical significance (SSA vs. age; r = -0.1), reflecting a slight tendency for SSA to decrease with age. There was no relationship between ST and age. CONCLUSION: Asymptomatic adults tend to stand with a stable global balance and it is expected that 95% of normal adults have an SSA and ST between 110° to 150° and 85° to 100°, respectively. C7 plumbline in front of the HA is not necessarily associated with a spinal pathology. Results suggest that in adults, anterior displacement of C7 plumbline with respect to sacrum cannot be attributed solely to aging and should raise a suspicion for the risk of developing spinal pathology.

Classification of high-grade spondylolistheses based on pelvic version and spine balance: possible rationale for reduction.

STUDY DESIGN: Retrospective review of a radiographic database of high-grade spondylolisthesis patients in comparison with asymptomatic controls. OBJECTIVE: To analyze the sagittal spinopelvic alignment in high-grade spondylolisthesis patients and identify subgroups that may require reduction to restore sagittal balance. SUMMARY OF BACKGROUND DATA: High-grade spondylolisthesis is associated with an abnormally high pelvic incidence (PI); however, the spatial orientation of the pelvis, determined by sacral slope (SS) and pelvic tilt (PT), is not known. We hypothesized that sagittal spinal alignment would vary with the pelvic orientation. METHODS: Digitized sagittal radiographs of 133 high-grade spondylolisthesis patients (mean age, 17 years) were measured to determined sagittal alignment. K-means cluster analysis identified 2 groups based on the PT and SS, which were compared by paired t test. Comparisons were made to asymptomatic controls matched for PI. RESULTS: High-grade spondylolisthesis patients had a mean PI of 78.9 degrees +/- 12.1 degrees . Cluster analysis identified a retroverted, unbalanced pelvis group with high PT (36.5 degrees +/- 8.0 degrees )/low SS (40.3 degrees +/- 9.0 degrees ) and a balanced pelvic group with low PT (mean 21.3 degrees +/- 8.2 degrees )/high SS (59.9 degrees +/- 11.2 degrees ). The retroverted pelvis group had significantly greater L5 incidence and lumbosacral angle with less thoracic kyphosis than the balanced pelvic group. A total of 83% of controls had a "balanced pelvis" based on the categorization by SS and PT. CONCLUSION: Analysis of sagittal alignment of high-grade spondylolisthesis patients revealed distinct groups termed "balanced" and "unbalanced" pelvis. The PT and SS were similar in controls and balanced pelvis patients. Unbalanced pelvis patients had a sagittal spinal alignment that differed from the balanced pelvis and control groups. Treatment strategies for high-grade spondylolisthesis should reflect the different mechanical strain on the spinopelvic junction in each group; reduction techniques might be considered in patients with an unbalanced pelvis high-grade spondylolisthesis.

Sagittal spinopelvic balance in normal children and adolescents.

The sagittal spinopelvic balance is poorly documented in normal pediatric subjects. The purpose of this study is to characterize the sagittal spinopelvic balance in the pediatric population and to evaluate the correlations between spinopelvic parameters. Seven parameters were evaluated from the lateral standing radiographs of 341 normal subjects aged 3-18 years old: thoracic kyphosis (TK), thoracic tilt (TT), lumbar lordosis (LL), lumbar tilt (LT), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI). The mean values for the pelvic parameters were 49.1+/-11.0, 7.7+/-8.0 and 41.4+/-8.2 degrees for PI, PT and SS, respectively. The mean values for the spinal parameters were 48.0+/-11.7, 44.0+/-10.9, -7.3+/-5.2 and -3.1+/-5.2 degrees for LL, TK, LT and TT, respectively. The spinopelvic parameters were different from those reported in normal adults, but the correlations between the parameters were similar. PI was significantly related to SS and PT. Significant correlations were found between the parameters of adjacent anatomical regions. Pelvic morphology (PI) regulates sagittal sacro-pelvic orientation (SS and PT). Sacral orientation (SS) is correlated with the shape (LL) and orientation (LT) of the lumbar spine. Adjacent anatomical regions of the spine and pelvis are interdependent, and their relationships result in a stable and compensated posture, presumably to minimize energy expenditure. Results from this study could be used as an aid for the planning of surgery in pediatric patients with spinal deformity in order to restore a relatively normal sagittal spinopelvic balance.

The vertical projection of the sum of the ground reactive forces of a standing patient is not the same as the C7 plumb line: a radiographic study of the sagittal alignment of 153 asymptomatic volunteers.

STUDY DESIGN: A radiographic study of 153 normal volunteers. OBJECTIVES: 1) To test the hypothesis that the vertical projection of the sum of the ground reactive forces of a standing patient is located in the same place in the sagittal plane as the C7 plumb line; 2) to determine if there are consistent geometric relationships between the location of the top of the spine and the pelvis in the sagittal plane that occur in individuals without symptoms of back pain or radiographic evidence of deformity. SUMMARY OF BACKGROUND DATA: Defining the optimal state of spinal balance is difficult. A full understanding of the compensatory relationships between the spine, pelvis, and lower limbs remains elusive. METHODS: A total of 153 normal volunteers were subjected to radiographic examination using a digital force plate, a stabilized standing position, a standardized radiographic technique, and the computerized measurement of sagittal alignment. RESULTS: 1) The C7 plumb line and the gravity line in a stabilized standing position are not located in the same place; 2) the association between the center of T1 and the sacral endplate may be an anatomic constant and a marker of spinal balance in individuals without symptoms of back pain or radiographic evidence of deformity, and is determined by the formula 99 degrees - 0.1 degrees (sacral slope). CONCLUSIONS: We speculate that this information will be very helpful in evaluating symptomatic spinal disease in the context of the overall alignment of the spine and pelvis.

Sagittal alignment of the spine and pelvis in the presence of L5-s1 isthmic lysis and low-grade spondylolisthesis.

STUDY DESIGN: A radiographic study of 82 patients with L5-S1 spondylolysis or spondylolisthesis of less than 50% displacement of L5 on S1. OBJECTIVE: To measure and describe the sagittal alignment of the spine and pelvis in patients with spondylolysis before the development of a large secondary deformity associated with progression of the spondylolisthesis. SUMMARY OF BACKGROUND DATA: Several publications have addressed the alignment of the spine and pelvis as an important factor in the occurrence, symptomatology, progression, and treatment of spondylolysis and spondylolisthesis. To our knowledge, this is the first report to systematically document the native sagittal alignment of affected patients and compare them to a large control population. MATERIALS AND METHODS: The sagittal alignment in this cohort of 82 patients was compared with a control population of 160 patients without symptoms of back pain or radiographic abnormalities of the spine and pelvis that was the subject of a previous study. RESULTS: Patients with spondylolysis and low-grade spondylolisthesis demonstrate increased pelvic incidence, increased lumbar lordosis, but less segmental extension between L5 and S1 than in a normal population. CONCLUSIONS: These data suggest that differences in the sagittal alignment of the spine and pelvis may influence the biomechanical environment that results in the development of spondylolysis and progressive spondylolisthesis.

Computerized assessment of sagittal curvatures of the spine: comparison between Cobb and tangent circles techniques.

OBJECTIVE: The tangent circles technique has been proposed as an alternative to the Cobb angle technique to assess sagittal curves of the spine. However, it has never been compared directly to the Cobb technique. This study compares the reproducibility and clinical relevance of the maximum Cobb angle and tangent circles techniques. METHOD: Standing sagittal radiographs of the spine of 10 adolescents with idiopathic scoliosis, 10 adolescents with spondylolisthesis, and 10 healthy adolescents were used. Thoracic kyphosis (TK) and lumbar lordosis (LL) were measured by 3 observers using the maximum Cobb angle and the tangent circles techniques. Intra- and interobserver intraclass correlation coefficients (ICCs) were calculated. RESULT: Intra- and interobserver ICCs for TK were 0.88 and 0.85, respectively, for the maximum Cobb angle technique, and 0.94 and 0.83, respectively, for the tangent circles technique. Intra- and interobserver ICCs for LL were 0.97 and 0.77, respectively, for the maximum Cobb angle technique, and 0.88 and 0.94, respectively, for the tangent circles technique. The 2 techniques were highly correlated for the measurement of the TK (r=0.93) and LL (r=0.88). CONCLUSION: Both techniques provide excellent intra- and interobserver reproducibility. Tangent circles technique may be a good alternative to the Cobb angle technique because it allows the evaluation of the global geometry of sagittal spinal curves, especially when there is limited visibility of bony structures on radiographs.

Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters.

OBJECTIVE: The purpose of this study is to introduce a method to analyze and characterize the global sagittal balance of the human trunk using indexes derived from the shape and orientation of the pelvis and cervical, thoracic, and lumbar spine. METHODS: Standing lateral x-rays of a cohort of 160 asymptomatic young adult volunteers were obtained. On each radiograph, a simplified model of the spine and pelvis was created using a dedicated computer software, and the following shape and orientation variables were calculated at each anatomic level: pelvic incidence, pelvic tilt, sacral slope, cervical curvature and tilt, thoracic curvature and tilt, and lumbar curvature and tilt. RESULTS: Significant linear correlations were found between each single adjacent shape parameter as well as between each single adjacent orientation parameter at all anatomic levels. Significant correlations were also found between some shape and orientation parameters at the same anatomic level as well as between adjacent anatomic areas. In general, the linear correlations were stronger between shape and orientation variables at the pelvic, lumbar, and cervical areas and weaker at the thoracic level and between the thoracic and lumbar areas. CONCLUSIONS: These results confirm that the pelvis and spine in the sagittal plane can be considered as a linear chain linking the head to the pelvis where the shape and orientation of each anatomic segment are closely related and influence the adjacent segment to maintain a stable posture with a minimum of energy expenditure. Changes in shape or orientation at one level will have a direct influence on the adjacent segment. Knowledge of these normal relationships is of prime importance for the comprehension of sagittal balance in normal and pathologic conditions of the spine and pelvis.

Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position.

STUDY DESIGN: A prospective radiographic study of 160 volunteers without symptoms of spinal disease was conducted. OBJECTIVES: The objective of this study was to describe, quantify, and classify common variations in the sagittal alignment of the spine, sacrum, and pelvis. SUMMARY OF BACKGROUND DATA: Previous publications have documented the high degree of variability in the sagittal alignment of the spine. Other studies have suggested that specific changes in alignment and the characteristics of the lumbar lordosis are responsible for degenerative changes and symptomatic back pain. METHODS: In the course of this study, anteroposterior and lateral radiographs of 160 volunteers in a standardized standing position were taken. A custom computer application was used to analyze the alignment of the spine and pelvis on the lateral radiographs. A four-part classification scheme of sagittal morphology was used to classify each patient. RESULTS: Reciprocal relationships between the orientation of the sacrum, the sacral slope, the pelvic incidence, and the characteristics of the lumbar lordosis were evident. The global lordotic curvature, lordosis tilt angle, position of the apex, and number or lordotic vertebrae were determined by the angle of the superior endplate of S1 with respect to the horizontal axis. CONCLUSIONS: Understanding the patterns of variation in sagittal alignment may help to discover the association between spinal balance and the development of degenerative changes in the spine.

The importance of spino-pelvic balance in L5-s1 developmental spondylolisthesis: a review of pertinent radiologic measurements.

STUDY DESIGN: A review article. OBJECTIVES: The purpose of this article is to review pertinent radiologic measurements for the evaluation of spino-pelvic balance in developmental spondylolisthesis, based on the experience of the Spinal Deformity Study Group. SUMMARY OF BACKGROUND DATA: Over the past decade, pelvic morphology has been shown to significantly influence spino-pelvic balance of the human trunk in normal and pathologic conditions. This finding has important implications for the evaluation and treatment of developmental spondylolisthesis and has fostered a renewed interest in the radiologic evaluation of spino-pelvic balance in this condition. METHODS: The lateral standing radiographs of the spine and pelvis of subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence, sacral slope, pelvic tilt, L5 incidence angle, lumbosacral angle, lumbar lordosis, thoracic kyphosis, and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of an adult and child reference population. RESULTS: The pelvic shape, best quantified by the pelvic incidence angle, determines the position of the sacral endplate. The spine reacts to this position by adapting through lumbar lordosis, the amount of lordosis increasing as the sacral slope increases in order to balance the trunk in the upright position. Pelvic incidence, sacral slope, pelvic tilt, and lumbar lordosis are found to be significantly greater in subjects with developmental spondylolisthesis, while thoracic kyphosis is significantly lower when compared to a reference population. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases, suggesting that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Studies also indicate that pelvic incidence is unaffected by surgical reduction and instrumentation. Pelvic tilt, sacral slope, and thoracic kyphosis are slightly affected, while grade, L5 incidence angle, lumbosacral angle, and shape of the lumbar spine are significantly improved after surgery. A postoperative improvement in L5 incidence angle and lumbosacral angle appears correlated with a better outcome while subjects with a poor outcome have a higher preoperative grade. CONCLUSIONS: Spino-pelvic balance in the sagittal plane can be considered as an open linear chain linking the head to the pelvis where the shape and orientation of each successive anatomic segment are closely related and influence the adjacent segment. Pelvic morphology and spino-pelvic balance are abnormal in developmental spondylolisthesis. These abnormalities should be quantified on lateral standing radiographs of the spine and pelvis and have important implications for the evaluation and treatment of this pathologic condition.

Sagittal alignment of the spine and pelvis during growth.

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.

Spondylolisthesis, pelvic incidence, and spinopelvic balance: a correlation study.

STUDY DESIGN: A retrospective study of the sagittal alignment in developmental spondylolisthesis. OBJECTIVES: To investigate the role of pelvic anatomy and its effect on the global balance of the trunk in developmental spondylolisthesis. SUMMARY OF BACKGROUND DATA: Pelvic incidence (PI) is a fundamental anatomic parameter that is specific and constant for each individual, and independent of the three-dimensional orientation of the pelvis. Recent studies have suggested an association between a high PI and patients with isthmic spondylolisthesis. METHODS: The lateral standing radiographs of the spine and pelvis of 214 subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of a cohort of 160 normal subjects. Student's tests were used to compare the parameters between the curve types and Pearson's correlation coefficients were used to investigate the association between all parameters (alpha = 0.01). RESULTS: PI, SS, PT, and LL are significantly greater (P < 0.01) in subjects with spondylolisthesis, while TK is significantly decreased. PI has a direct linear correlation (0.41-0.65) with SS, PT, and LL. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases. CONCLUSIONS: Since PI is a constant anatomic pelvic variable specific to each individual and strongly determines SS, PT, and LL, which are position-dependent variables, this study suggests that pelvic anatomy has a direct influence on the development of a spondylolisthesis.Study participants with an increased pelvic incidence appear to be at higher risk of presenting a spondylolisthesis, and an increased PI may be an important factor predisposing to progression in developmental spondylolisthesis.