INCIDENCE OF SPINAL DEFORMITY IN ADULTS AND ITS DISTRIBUTION ACCORDING SRS-SCHWAB CLASSIFICATION

Objective: To evaluate the incidence of spinal deformity in adults, as well as its distribution according the curve type and the occurrence of sagittal modifiers of the SRS-Schwab classification.. Methods: Radiographs in frontal and lateral views of the entire column were performed and radiographic parameters were used to diagnose the vertebral deformity for the classification according to the SRS-Schwab system. Results: We included 302 patients in the study, 236 (78.1%) women and 66 (21.9%) men. Fifty-six of the participants were diagnosed with ASD, 50 women and 6 men. The incidence of ASD was 18.5% in the total population, ranging from 9.1% in males and 21.2% in females (p=0.04). As to age group, the incidence was 11.9% in patients between 18 and 39 years, 12% between 40 and 59 years and 28.8% in patients with 60 years of age or older, significantly higher in the oldest group (p=0.002). When analyzing the correlation between age and progression of sagittal modifiers, there was no significant difference in the PI-LL and PT modifiers, but there was significant difference of SVA modifier (p=0.008), with a higher age in individuals “++”. Conclusion: This study presented demographic data on ASD in a Brazilian population sample. There was a higher incidence of ASD in females and individuals aged ≥ 60 years. As for the sagittal modifiers of SRS-Schwab classification, there was a correlation between increasing age and degree of progression of SVA.


INTRODUCTION
2][3][4][5][6] Recent studies have shown a high prevalence, especially in the elderly population, reaching a rate of 68% in individuals over 60 years of age. 7Clinically, while some patients are asymptomatic, others complain of severe pain and functional disability that are often severe.Thus, the radiographic parameters should be considered when evaluating the quality of life.[10] The treatment objectives and surgical strategies for ASD are entirely different from those of adolescent idiopathic scoliosis (AIS), and the classification systems used for this deformity are not useful for the deformity in adults.2][13] In 2012, a new SD classification system presented, advocated by Schwab et al and called the SRS-Schwab Classification.This system (Figure 1) classifies the type of curve in the coronal plane, and includes three sagittal spinopelvic modifiers that reflect the components of the deformity in the sagittal plane, as well as the mechanisms used to compensate for the deformity. 14More recently, it was demonstrated that the SRS-Schwab classification system reflects the severity of the symptoms, in that both the type of curve and the sagittal modifiers have a significant correlation with quality of life indicators and the need for surgery. 15owever, much of the information about ASD comes from other populations, and little data has been presented for Brazilian patients.Moreover, the classification system that is most widely accepted today -the SRS Schwab systemwas developed and validated based on just a single population sample from the USA.The aim of our study was to present information about ASD in a Brazilian population sample, such as its incidence and distribution by age range and sex, as well as its distribution across the types of curves and the occurrence of sagittal modifiers within the SRS Schwab classification system.To date, there is no known data available on this subject.

METHODS
This is a prospective, observational study involving adult individuals over the age of eighteen, who were seen at the same outpatient clinic, for complaints related to the spine.Following approval by the Ethics Committee, these individuals were invited to participate in the study, and radiographic images of the total spine (panoramic), scanned in front and profile views, were obtained, as well as demographic data, such as sex, age, weight, and height.Individuals who had undergone previous spinal surgery, or who had any neurological or neuromuscular pathology, or a history of traumatic lesion, spinal oncology, or the presence of any deforming disease of the lower limbs capable of affecting the individual's posture or the gait, were excluded from the study.
All the radiographs were obtained using a standardized technique, with the patients being asked to remain in a comfortable standing position, with the elbow in full flexion and the shoulder flexed at 45°, and with the hands relaxed and the fingers resting on the clavicle or the zygomatic bone.Individuals with exams of high technical quality allowing good visualization of the entire length of the spine, from C2 to the sacrum and to the head of the femur bilaterally, were considered suitable for the study.
The radiographic parameters of interest were evaluated using the Surgimap Spine software (Nemaris Inc.New York, USA) (Figure 2).Based on these radiographic parameters, ASD was diagnosed by the presence of at least one of the following criteria: deformity of the coronal plane with Cobb angle ≥ 20°; SVA ≥ 5 cm; PT ≥ 25°, or thoracic kyphosis ≥ 60°.
The radiographic parameters were then used to classify those individuals diagnosed with ASD according to the SRS Schwab classification system.The demographic data considered were sex and age and the patients were divided into three groups by age range: Group 1 -from 18 to 39 years of age; Group 2 -from 50 to 59 years of age; and Group 3 -60 years of age or older.
The incidence of ASD was compared across the different age groups using the Chi-square test.The correlation of the types of curve, and the progression of the sagittal modifiers of the SRS Schwab classification with the patients' age, was also analyzed, using the Analysis of Variance test (ANOVA), with a level of significance of p < 0.05.

RESULTS
During the period from March 2013 to March 2014, 302 patients who met the inclusion criteria and signed the Informed Consent Form were included in the study.Of these, 236 were female (78.1%) and 66 were male (21.9%).The average age of the total study population was 52.7 years.An analysis of the radiographic parameters yielded 56 patients who met the criteria for a diagnosis of ASD, with an average age of 58.9 years; six men (10.7%) and 50 women (89.3%).Thus, the incidence of ASD in the total study population was 18%, ranging from 9.1% in the men to 21.2% in the women (Table 1), i.e. significantly higher in women (p=0.04).As regards age range, the incidence of ASD was 11.9% in patients aged from 18 to 39 years, 12% in those aged from 40 to 59 years, and 28.8% in those aged 60 years or over.Comparing the incidence of ASD in the different age ranges, we observed a significantly higher incidence in population aged 60 years or over (p=0.002).(Table 2) The patients diagnosed with ASD were classified according to the SRS Schwab classification system.In terms of the type of curve (Table 3), ten (17.9%) had a Thoracic curve (Type T), twenty (35.7%) had a Lumbar curve (Type L), three (5.4%) had a Double curve (Type D), and twenty-three (41.1%) did not have a curve in the coronal plane (Type N), but only a deformity in the sagittal plane.Table 4 shows the distribution of patients by the sagittal modifiers of the SRS Schwab classification.
Table 5 shows the correlation between the progression of the sagittal modifiers and age.We observed no significant difference in terms of age in the degrees of either PI-LL (p=0.498) or PT (p=0.257)sagittal modifier.However, there was a significant difference in terms of age, and the degrees of the SVA modifier (p=0.008), with the "++" individuals being older.

DISCUSSION
There is a tendency towards the aging of the population in general, with a considerable increase in the elderly population, and consequently, an increase in the diseases associated with advancing age.It has been shown that the occurrence of ASD, and all the associated functional limitations, are correlated advancing age. 7In this study, we observed that the incidence of deformity was significantly higher in the more elderly patients, in the age range 60 years of age or over (p=0.0002).However, while a recent study showed that more than 60% of elderly individuals had some degree of deformity, 7 the actual incidence of ASD diagnosed in our sample was 28.8% in the 60 years of age or over group.
In our sample, most of the patients evaluated were female, 236 (78.1%) vs. 66 (21.9%), with a significantly higher incidence of ASD among the females, 21.2% vs. 9.1% (p=0.04).Other studies have  reported a higher percentage of ASD diagnosed in females, 7,8,15 reaching as high as 84.1%.Based on what we observed regarding the distribution of the types of curves, with a predominance of curves without deformity in the coronal plane, and of lumbar curves over thoracic or double curves, we do not believe that the prevalence of ASD in women is influenced by the greater incidence of AIS in women, as most of the curves resulting from AIS are either thoracic or double curves.
Although ASD has a complex range of clinical and radiographic presentations, the recently developed SRS Schwab classification system 14 has been widely used globally, and its relevance has been demonstrated, both for clinical correlation and treatment indication. 15omparing the results of that study our findings, which are based on a Brazilian sample population, a difference in the distribution of individuals with ASD by type of curve can be seen.In the study by Terran et al, 15 the largest number of deformities are classified as double curves (Type D, 31.3%),followed by thoracolumbar/lumbar curves (Type L, 29.7%), deformities exclusively in the sagittal plane (Type N, 16.8%), and thoracic curves (Type T, 14.3%).In the current sample, a marked predominance of Type N curves (41.1%) was observed, followed by Type L curves (35.7%), and type T curves (17.9%), with a minority of curves classified as Type D (5.4%).
As regards the sagittal modifiers described by the SRS Schwab classification, this study presents the distribution of the three modifiers (PT, SVA, and PI-LL) by class (0, +, and ++) across the Brazilian population sample.In our study, the analysis performed showed a progressive increase in age with the progression of the three sagittal modifiers.While this correlation was not significant for the PT and PI-LL modifiers (p = 0.498 and p = 0.257), it was significant for SVA (p = 0.008).Recently, Fu et al published a study of patients with ASD who underwent surgery or conservative treatment and stratification by age range demonstrated a worsening of SVA as age increased, associated with a worsening of quality of life indicators. 16his aim of this study was not to analyze the correlation between the distribution of the patients in the sample, in terms of the types of curves and sagittal modifiers of the SRS Schwab classification, and the clinical parameters (quality of life indicators).However, a worsening of the classification level of the sagittal modifiers has been associated with a worsening of those clinical parameters, a higher occurrence of surgical treatment, and a greater need for complex surgeries involving osteotomies. 15Almost all the information about the study of ASD is based on other populations, and data from studies involving the Brazilian population samples is lacking.We intend to pursue this line of study in the future, evaluating additional information about the correlation of the SRS Schwab classification with clinical parameters and treatment indications in a Brazilian population sample, to demonstrate the relevance of this classification system for our context.

CONCLUSIONS
This study presents the demographic data about adult spinal deformity (ASD) in a Brazilian population sample.A higher incidence of ASD is observed among the females and in individuals sixty years of age or older, as compared to the other younger age ranges.Regarding the sagittal modifiers, there is evidence of a non-significant progression of the PT and IP-LL modifiers in accordance with increasing age, but a significant correlation exists between increased age and worsening degrees of SVA.

Figure 1 .
Figure 1.SRS-Schwab classification system, describing 4 types of curves and three sagittal modifiers.

Figure 2 .
Figure 2. Illustration of the measurement of radiographic parameters using Surgimap Spine software (Nemaris Inc.New York, USA).

Table 1 .
Incidence of adult spinal deformity in the total study population, distributed by sex and age range.

Table 2 .
There is no significant difference (p=1) between the incidence of deformity in patients in the 18-39 and 40-59 years of age ranges.However, there is a significant difference (p=0.02) between patients 60 years of age or older and the other groups.

Table 3 .
Distribution of patients diagnosed with ASD by the type of curve from the SRS-Schwab Classification.

Table 4 .
Distribution of patients diagnosed with ASD by the sagittal modifiers from the SRS-Schwab Classification.

Table 5 .
Correlation between age and the progression of the sagittal modifiers of the SRS-Schwab Classification.There was no correlation between age and the progression of the modifiers PI -LL and PT (p=0.498 and 0.257), but there was a significant correlation between age and the progression of SVA (p=0.008). Coluna/Columna.2015;14(2):93-6