Abstracts

INTRODUCTION

The vertebral spine plays an important role in the support and locomotion of the human body. An understanding of the elements that compose it is essential for learning about its role in body balance and alignment.¹1. Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8.

2. Hammerberg EM, Wood KB. Sagittal profile of the elderly. J Spinal Disord Tech. 2003;16(1):44-50.

3. Jackson RP, McManus AC. Radiographic analysis of sagittal plane alignment and balance in standing volunteers and patients with low back pain matched for age,sex, and size. A prospective controlled clinical study. Spine (Phila Pa 1976).1994;19(14):1611-8 ^{- 4}4. McLean IP, Gillan MG, Ross JC, Aspden RM, Porter RW. A comparison of methods for measuring trunk list. A simple plumbline is the best. Spine (Phila Pa 1976). 1996;21(14):1667-70.

Thoracic kyphosis and lumbar lordosis measurements are used to analyze trunk alignment. Overall vertebral alignment is assessed by the plumb line method.¹1. Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8.

2. Hammerberg EM, Wood KB. Sagittal profile of the elderly. J Spinal Disord Tech. 2003;16(1):44-50.

3. Jackson RP, McManus AC. Radiographic analysis of sagittal plane alignment and balance in standing volunteers and patients with low back pain matched for age,sex, and size. A prospective controlled clinical study. Spine (Phila Pa 1976).1994;19(14):1611-8 ^{- 4}4. McLean IP, Gillan MG, Ross JC, Aspden RM, Porter RW. A comparison of methods for measuring trunk list. A simple plumbline is the best. Spine (Phila Pa 1976). 1996;21(14):1667-70. More recently, the role of the pelvis has been widely recognized in the evaluation of spinal balance and alignment⁵5. During J, Goudfrooij H, Keessen W, Beeker TW, Crowe A. Toward standards for posture. Postural characteristics of the lower back system in normal and pathologic conditions. Spine (Phila Pa 1976). 1985;10(1):83-7.

6. Jackson RP, Peterson MD, McManus AC, Hales C. Compensatory spinopelvic balance over the hip axis and better reliability in measuring lordosis to the pelvic radius on standing lateral radiographs of adult volunteers and patients. Spine (Phila Pa 1976). 1998;23(16):1750-67. ^{- 7}7. Legaye J, Duval-Beaupère G, Hecquet J, Marty C. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J. 1998;7(2):99-103., with the introduction of the concepts of Pelvic Incidence (PI), Pelvic Tilt (PT), and Sacral Slope (SS).

Deformities of the sagittal plane, such as loss of lumbar lordosis, can cause anterior inclination of the trunk, affecting sagittal balance. The main causes of loss of sagittal balance are degenerative diseases, inadequate fixation of the lumbar spine, post-traumatic deformity, and ankylosing spondylitis. In the initial stages of deformity, retroversion of the pelvis may compensate for the loss of sagittal balance, but with the progression of degenerative changes, its capacity to accommodate the trunk is exceeded, associated with an increase in the energy expended to maintain erect posture, causing pain, fatigue, and functional disability.⁷7. Legaye J, Duval-Beaupère G, Hecquet J, Marty C. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J. 1998;7(2):99-103. ^{, 8}8. Vaz G, Roussouly P, Berthonnaud E, Dimnet J. Sagittal morphology and equilibrium of pelvis and spine. Eur Spine J. 2002;11(1):80-7.

To analyze the consequences of changes in sagittal balance in each individual, we need to understand the normal parameters for the population. Several studies⁶6. Jackson RP, Peterson MD, McManus AC, Hales C. Compensatory spinopelvic balance over the hip axis and better reliability in measuring lordosis to the pelvic radius on standing lateral radiographs of adult volunteers and patients. Spine (Phila Pa 1976). 1998;23(16):1750-67.

7. Legaye J, Duval-Beaupère G, Hecquet J, Marty C. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J. 1998;7(2):99-103.

8. Vaz G, Roussouly P, Berthonnaud E, Dimnet J. Sagittal morphology and equilibrium of pelvis and spine. Eur Spine J. 2002;11(1):80-7.

9. Labelle H, Roussouly P, Berthonnaud E, Dimnet J, O'Brien M. The importance of spino-pelvic balance in L5-s1 developmental spondylolisthesis: a review of pertinent radiologic measurements. Spine (Phila Pa 1976). 2005;30(Suppl 6):S27-34.

10. Legaye J, Duval-Beaupère G. Sagittal plane alignment of the spine and gravity: a radiological and clinical evaluation. Acta Orthop Belg. 2005;71(2):213-20.

11. Roussouly P, Gollogly S, Berthonnaud E, Dimnet J. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976). 2005;30(3):346-53. ^{- 12}12. Schwab F, Lafage V, Boyce R, Skalli W, Farcy JP. Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine (Phila Pa 1976). 2006;31(25):E959-67. have evaluated the relationship between the position of the pelvis and spinal alignment. However, it is important to know the values of these radiographic parameters in healthy individuals, without spinal disease. Although some studies address these parameters, it is interesting to evaluate them in a specific population as there are structural differences between different population groups. We identified publications with evaluations of individuals from the European,¹³13. Vialle R, Levassor N, Rillardon L, Templier A, Skalli W, Guigui P. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005;87(2):260-7. Causcasian,¹⁴14. Mac-Thiong JM, Roussouly P, Berthonnaud E, Guigui P. Sagittal parameters of global spinal balance: normative values from a prospective cohort of seven hundred nine Caucasian asymptomatic adults. Spine (Phila Pa 1976). 2010;35(22):E1193-8. and Korean¹⁵15. Lee CS, Chung SS, Kang KC, Park SJ, Shin SK. Normal patterns of sagittal alignment of the spine in young adults radiological analysis in a Korean population. Spine (Phila Pa 1976). 2011;36(25):E1648-54. populations. However, a similar study has not yet been conducted for the Brazilian population.

The objective of this study is to observe the parameters of sagittal and spinopelvic balance in a sample of the Brazilian population consisting of volunteer asymptomatic individuals, in order to establish the relationship between these parameters, age, and sex and to compare the results with those of other studies that cover other population groups.

METHODS

The group analyzed comprised 50 adults who volunteered to take part in the study, including doctors and employees of the hospital where the study was carried out. All the individuals were Brazilian, over 20 years of age, and had no history of spinal pain or disease. Exclusion criteria included the presence of spinal deformity or inadequate imaging exams that would prevent proper analysis of the parameters in question.

Panoramic radiographs of the spine were performed in frontal and profile views in the orthostatic position. All were performed at the same radiology department, by the same professional, using the same technique. The exams were obtained with the individuals in a standing position with the knees extended and the hands on the supraclavicular fossae.¹⁶16. Marks MC, Stanford CF, Mahar AT, Newton PO. Standing lateral radiographic positioning does not represent customary standing balance. Spine (Phila Pa 1976).2003;28(11):1176-82 Long cassettes (91 cm) were used and the radiograph was centered on T12 in inspiration, with a distance of 2 meters between the film and the focus. The images were digitalized and evaluated using Surgimap Spine software (Nemaris Inc., New York, USA). (Figure 1)

The sagittal and spinopelvic alignment parameters analyzed were sagittal vertical axis (SVA), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). (Figures 2 and 3)

All the parameter values studied were statistically analyzed. The statistical analysis was based on calculations of the average value, the standard deviation, and the standard error of both the data from the sample and those obtained from the published studies of different populations. The comparisons between groups were performed using the Student's t-test. The level of significance used was 5%.

RESULTS

Of the 50 volunteers analyzed, 25 were male and 25 were female. The average age of the volunteers was 34.85 years, ranging from 22 to 50 years of age. The average age of the male volunteers was 32.3, while the average age of the female volunteers was 37.4.

Table 1 displays the averages and standard deviations of the pelvic incidence, sacral slope, pelvic tilt, and sagittal vertical axis of the sample. Table 2 displays the normal values reported in other studies of different populations.¹¹11. Roussouly P, Gollogly S, Berthonnaud E, Dimnet J. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976). 2005;30(3):346-53. ^{, 13}13. Vialle R, Levassor N, Rillardon L, Templier A, Skalli W, Guigui P. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005;87(2):260-7. ^{, 17}17. Barrey C, Jund J, Noseda O, Roussouly P. Sagittal balance of the pelvis-spine complex and lumbar degenerative diseases. A comparative study about 85 cases. Eur Spine J. 2007;16(9):1459-67. ^{, 18}18. Glassman SD, Berven S, Bridwell K, Horton W, Dimar JR. Correlation of radiographic parameters and clinical symptoms in adult scoliosis. Spine (Phila Pa 1976). 2005;30(6):682-8.

There were no differences observed between males and females for any of the pelvic parameters in the population studied. (Table 3)

A comparison between the pelvic parameter values of the individuals in our study and the values reported for the European and Korean populations is shown in Table 4, with no difference noted between the Brazilian and Korean populations. However, differences between the European population and the Brazilian population sample were observed in relation to pelvic incidence and sacral slope (p=0.0001 and p=0.0140), with higher values for both parameters in the European population.

The averages and standard deviations of the pelvic parameters for males of all three population groups and the descriptive values (p) for the comparison between Europe and Brazil (p¹) and between Korea and Brazil (p²) are presented in Table 5. We observed that there was no difference between any of the parameter values for the Brazilian and Korean populations. However, there was a difference between the pelvic incidence values of the Brazilian and European populations (p=0.02), with higher values in the European population.

The averages and standard deviations of the pelvic parameters for females of all three population groups, and the descriptive values (p) for the comparison between Europe and Brazil (P¹1. Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8.) and between Korea and Brazil (P²2. Hammerberg EM, Wood KB. Sagittal profile of the elderly. J Spinal Disord Tech. 2003;16(1):44-50.) are shown in Table 6. We can see that there was no difference between any of the parameter values for the Brazilian and Korean populations. However, there were differences between the pelvic incidence and sacral slope values of the Brazilian and European populations (p=0.0007 and p=0.005). Both the pelvic incidence and sacral slope values of the European population were higher than those of the Brazilian population.

DISCUSSION

The overall sagittal alignment of the trunk can be measured using the sagittal vertical axis, which corresponds to the "plumb line".¹1. Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8. ^{, 2}2. Hammerberg EM, Wood KB. Sagittal profile of the elderly. J Spinal Disord Tech. 2003;16(1):44-50. It has been reported that normal adult sagittal alignment falls within a narrow margin in the pelvis, with an average sagittal vertical axis value in asymptomatic adults described as 0.5 cm

(± 2.5 cm) from the posterior-superior corner of the sacrum.³3. Jackson RP, McManus AC. Radiographic analysis of sagittal plane alignment and balance in standing volunteers and patients with low back pain matched for age,sex, and size. A prospective controlled clinical study. Spine (Phila Pa 1976).1994;19(14):1611-8 Since the work of Legaye and Duval-Beaupere,⁷7. Legaye J, Duval-Beaupère G, Hecquet J, Marty C. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J. 1998;7(2):99-103. various studies have stressed the importance of the pelvis in the sagittal alignment of adults. An analysis of the pelvis in the sagittal plane is obtained by measuring three angles: pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS).

The impact of loss of sagittal balance on quality of life indicators was demonstrated by Glassman et al.¹⁹19. Lafage V, Schwab F, Patel A, Hawkinson N, Farcy JP. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976). 2009;34(17):E599-606. Both patients who had previously undergone spinal arthrodesis and those without any prior surgeries had poorer quality of life parameters, including the Oswestry Index, the SF-12, and the SRS-22, associated with an increase in the values of the sagittal vertical axis, which indicates a loss of sagittal balance. This study demonstrates the importance of analyzing sagittal balance both in the evaluation of patients with complaints of back pain and functional limitations and for the outcome of surgical treatment.

More recently, the correlation between the pelvic parameter PT and the worsening of quality of life parameters (Oswestry Index, SF-12, and SRS-22) was demonstrated, confirming that pelvic position is correlated with impaired functional capacity in patients.²⁰ High values of pelvic tilt indicate pelvic retroversion, compensating for the loss of sagittal balance.

However, for us to correctly understand the effects of the loss of sagittal balance on the quality of life of each individual, we must know the normal values of the parameters used to evaluate sagittal and spinopelvic balance in the population. Although Brazil is a country of continental proportions and a mixed population, this study presents the results of an analysis of a small sample of healthy individuals. It can be noticed that the values obtained from the sample are within the values described as normal in the literature.¹¹11. Roussouly P, Gollogly S, Berthonnaud E, Dimnet J. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976). 2005;30(3):346-53. ^{, 13}13. Vialle R, Levassor N, Rillardon L, Templier A, Skalli W, Guigui P. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005;87(2):260-7. ^{, 17}17. Barrey C, Jund J, Noseda O, Roussouly P. Sagittal balance of the pelvis-spine complex and lumbar degenerative diseases. A comparative study about 85 cases. Eur Spine J. 2007;16(9):1459-67. ^{, 18}18. Glassman SD, Berven S, Bridwell K, Horton W, Dimar JR. Correlation of radiographic parameters and clinical symptoms in adult scoliosis. Spine (Phila Pa 1976). 2005;30(6):682-8. In our study, there were no differences in the radiographic parameters when compared by sex of the individuals evaluated.

When we compare the average values and standard deviations obtained in this study with those published in the literature for European and Korean populations, we can see that: there were no differences for any of the pelvic parameters between the Brazilian and Korean populations, even when compared by sex; the values of pelvic incidence of the European population were higher than those of the Brazilian population sample, both for the total sample and in the comparison by sex; the values of sacral slope of the European population were higher than those of the Brazilian population sample, both for the total population and for the female group; and the pelvic tilt values of the European population were similar to those obtained for the sample population studied. These data show the importance of studies in this format, aimed at adjusting the radiographic parameters for different populations.

CONCLUSIONS

This study presents the pelvic incidence, sacral slope, pelvic tilt, and sagittal vertical axis values of a sample of the Brazilian population. There were no differences in any radiographic parameter between males and females in the sample. The values obtained are compatible with the values presented as normal in the literature. A comparison of the study results with data published about other populations revealed no differences in any of the pelvic parameters between the Brazilian and Korean populations. There were differences in pelvic incidence between the Brazilian and European populations both in the total sample and in the male and female groups. There were differences in sacral slope between the Brazilian and European populations in relation to the total sample and the female group.

All authors declare no potential conflict of interest concerning this article.

REFERENCES

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