RELATIONSHIP BETWEEN CERVICAL SAGITTAL ALIGNMENT AND CURVE PATTERN IN IDIOPATHIC SCOLIOSISABSTRACT
Objective: The aim of this study was to correlate the different curve patterns presented in idiopathic scoliosis with the sagittal cervical parameters of patients with this pathology.
Method: This was a cross-sectional, descriptive and retrospective study. Information was collected from medical records and lateral panoramic radiographs of 49 patients with idiopathic scoliosis were analyzed. The data was assessed quantitatively using the following cervical parameters: Cobb from C2-C7, the distance from the center of gravity of the head to C7, the T1 slope, the thoracic Inlet angle, the cervical version, C7-S1 SVA, the Cobb angle of the main curve, and the kyphosis at T1-T12. These parameters were analyzed in relation to the different curve types presented and the lumbar and sagittal modifiers, as described by Lenke’s classification for idiopathic scoliosis. All the results were statistically analyzed and the significance level adopted was 5% (p<0.05).
Results: The Cobb C2-C7 values showed a decrease in cervical lordosis in these patients (p = 0.048) and also showed an inverse relationship with thoracic kyphosis (p = 0.027). There was a statistically significant relationship between T1 inclination and loss of cervical lordosis (p = 0.003) also with variations in the sagittal modifier (p < 0.05). Lenke 2 and Lenke 4 curves were related to loss of cervical lordosis (p = 0.038).
Conclusion: There was a loss of cervical lordosis in the patients in this study, evidenced by the alteration of the cervical sagittal parameters in these patients. The T1 slope was the variable that showed the greatest correlation with cervical alignment parameters, varying mainly in relation to the type of curve and sagittal modifier. In addition, curves affecting the upper thoracic spine (Lenke 2 and Lenke 4) significantly altered the sagittal cervical alignment of patients with idiopathic scoliosis, and it is recommended that they be carefully observed. Level of Evidence VI; Retrospective Observational Study.
Keywords:
Scoliosis; Spinal Curvatures; Classification; Postural Balance; Cervical Vertebrae
Resumo:
Objetivo: Correlacionar os diferentes padrões de curva apresentados na escoliose idiopática com os parâmetros sagitais cervicais de pacientes portadores dessa patologia.
Método: Este foi um estudo transversal, descritivo e retrospectivo. Foram coletadas informações de prontuários e analisadas radiografias panorâmicas laterais de 49 pacientes portadores de escoliose idiopática. Os dados foram avaliados quantitativamente usando os seguintes parâmetros cervicais: Cobb de C2-C7, a distância do centro de gravidade da cabeça até C7, a inclinação T1, o ângulo do Inlet torácico, a versão cervical, C7-S1 SVA, o ângulo de Cobb da curva principal, e a cifose em T1-T12. Tais parâmetros foram analisados em relação aos diferentes tipos de curva apresentados e aos modificadores lombar e sagital, conforme descrito pela classificação de Lenke para escoliose idiopática. Todos os resultados foram analisados estatisticamente e o nível de significância adotado foi de 5% (p<0,05).
Resultados: Os valores encontrados para o Cobb C2-C7 evidenciaram uma diminuição da lordose cervical nesses pacientes (p=0,048) e apresentaram, ainda uma relação inversa com a cifose torácica (p = 0,027). Houve relação estatisticamente relevante entre a inclinação de T1 e a perda da lordose cervical (p = 0,003) e também com as variações do modificador sagital (p < 0,05). Curvas Lenke 2 e Lenke 4 apresentaram relação com a perda da lordose cervical (p = 0,038).
Conclusão: Houve uma perda da lordose cervical nos pacientes deste estudo, evidenciada pela alteração dos parâmetros sagitais cervicais nesses pacientes. A inclinação de T1 foi a variável que mais apresentou correlação com os parâmetros do alinhamento cervical, variando principalmente em relação ao tipo de curva e modificador sagital. Além disso, curvas que acometem a coluna torácica alta (Lenke 2 e Lenke 4) alteraram significativamente o alinhamento cervical sagital de pacientes portadores de escoliose idiopática, sendo recomendado observá-las cuidadosamente. Nível de Evidência IV; Estudo Observacional Retrospectivo.
Descritores:
Escoliose; Curvaturas da Coluna Vertebral; Classificação; Equilíbrio Postural; Vertebras Cervicais
Resumen:
Objetivo: Correlacionar los diferentes patrones de curvatura presentados en la escoliosis idiopática con los parámetros sagitales cervicales de los pacientes con esta patología.
Método: Se trata de un estudio transversal, descriptivo y retrospectivo. Se recogió información de las historias clínicas y se analizaron las radiografias panorâmicas laterales de 49 pacientes con escoliosis idiopática. Los datos se evaluaron cuantitativamente mediante los siguientes parámetros cervicales: Cobb de C2-C7, la distancia del centro de gravedad de la cabeza a C7, la inclinación de T1, el ángulo Inlet torácico, la versión cervical, C7-S1 SVA, el ángulo de Cobb de la curva principal y la cifosis en T1-T12. Estos parámetros se analizaron en relación con los diferentes tipos de curva presentados y los modificadores lumbares y sagitales, según la clasificación de Lenke para la escoliosis idiopática. Todos los resultados fueron analizados estadísticamente y el nivel de significación adoptado fue del 5% (p<0,05).
Resultados: Los valores encontrados para Cobb C2-C7 mostraron una disminución de la lordosis cervical en estos pacientes (p = 0,048) y también mostraron una relación inversa con la cifosis torácica (p = 0,027). Existía una relación estadísticamente significativa entre la inclinación T1 y la pérdida de lordosis cervical (p = 0,003) y también con las variaciones del modificador sagital (p < 0,05). Las curvas de Lenke 2 y Lenke 4 estaban relacionadas con la pérdida de lordosis cervical (p = 0,038).
Conclusión: Hubo una pérdida de lordosis cervical en los pacientes de este estudio, evidenciada por la alteración de los parámetros sagitales cervicales en estos pacientes. La inclinación T1 fue la variable que mostró mayor correlación con los parámetros de alineación cervical, variando principalmente en relación al tipo de curva y modificador sagital. Además, las curvas que afectan a la columna torácica superior (Lenke 2 y Lenke 4) alteraron significativamente el alineamiento cervical sagital de los pacientes con escoliosis idiopática, por lo que se recomienda una cuidadosa observación. Nivel de Evidencia IV; Estudio Observacional Retrospectivo.
Descriptores:
Escoliosis; Curvaturas de la Columna Vertebral; Clasificación; Equilíbrio Postural; Vértebras Cervicales
INTRODUCTION
Scoliosis is defined as a three-dimensional deformity in which, in the frontal plane, there is a lateral deviation greater than 10 degrees. The sagittal alignment of the spine is characterized by having a lordotic curvature from C2 to C7, kyphosis from T1 to T12, and lordosis from L1 to L5, and variations in this alignment can lead to changes in the individual’s overall balance.1
Multiple studies have analyzed the relationship between lumbar lordosis and thoracic kyphosis, but very little has been published about the cervical spine’s reaction to the deformity present in idiopathic scoliosis.2
Recently, some authors have noted an inverse relationship between thoracic sagittal alignment and cervical spine alignment in patients with idiopathic scoliosis. Patients with AIS have shown a decrease in cervical lordosis in the lower segments, associated with kyphosis in the higher cervical segments. The relationship between T1 slope and thoracic kyphosis possibly justifies this.3,4
This study relates the sagittal cervical parameters of patients with adolescent idiopathic scoliosis to the different curve patterns presented according to Lenke’s classification.5
METHOD
A cross-sectional, retrospective, descriptive study conducted with information obtained from medical records and the evaluation of panoramic radiographs in posteroanterior and lateral views of 49 patients in outpatient follow-up at the spine service of the Hospital das Clínicas da Unicamp from January 2015 to January 2016.
All patients diagnosed with adolescent idiopathic scoliosis in outpatient follow-up, of both sexes, aged 10 years and older, with curves without restriction of angulation, location, or flexibility were included in this study. All patients with other types of scoliosis that are not idiopathic adolescent scoliosis were excluded from this study, as well as patients who had already undergone surgical treatment for the correction of the deformity or any other type of surgical treatment on the spine or thoracic cavity, as they could prevent the correct measurement of the radiographic parameters. All patients with other comorbidities that could influence the conduct of the study were also excluded. The study was conducted after approval by the Ethics Committee in Research with Human Beings of the State University of Campinas - Unicamp (opinion: 886,837 of November 24, 2014).
All the X-rays were obtained on the same digital X-ray machine, following the standardized technique in the Radiology Service of the Hospital das Clínicas of Unicamp for positioning, collimation, and radiation. The radiographic parameters were evaluated using the Surgimap Spine software (Nemaris Inc. New York, USA) on a 1 × 1 standard scale for all the images.
The data was evaluated quantitatively using the Cobb method for evaluating cervical lordosis from C2 to C7,6 the distance from the center of gravity of the skull (GOS) to C7 (GOS C0-C7)7 (Figure 1), measured the inclination of T1 (T1Slope),7 the angle of the thoracic inlet (ATI)7 (Figure 1), cervical version (neck-tilt)7 (Figure 1), plumb line C7-S1 (SVA C7-S1).7
A) Schematic drawing representing the inclination measurements of T1, ATI, and cervical version. B) Schematic drawing representing the Cobb measurement of the cervical spine C2-C7.
The cervical sagittal parameters were analyzed concerning the variables: the angular value of the main curve, Cobb of the proximal thoracic curve, Cobb curve of the thoracolumbar/lumbar curve, and T1-T12 Kyphosis value. In addition to being analyzed, the type of curve described by Lenke et al.5 (from Lenke 1 to Lenke 6) and the lumbar and sagittal modifiers are also being analyzed.
The results were distributed in tables, and then a statistical analysis of the obtained data was performed to objectively prove the relationship between cervical spine alignment in the sagittal plane and the curve patterns presented by the patients in this study.
The ages of the patients and the measurements taken of the parameters were described using summary measures (average, standard deviation, median, minimum, and maximum). In contrast, the sex was described using absolute and relative frequencies. Normality distribution tests were performed for all the measurements of the column evaluated using Kolmogorov-Smirnov tests.8 Pearson or Spearman correlations were calculated between the column measures to assess the presence of correlation between them. The measures evaluated according to the type of curve were described according to the classification of Lenke et al.5, with the sagittal modifier and the lumbar modifier.
The variables of the Lenke classification used in this study (curve types and modifiers) had their values compared with the cervical sagittal parameters through the use of analysis of variance (ANOVA) followed by Bonferroni multiple comparisons when there was a difference between the categories or Kruskal-Wallis tests followed by Dunn’s multiple comparisons.8 The tests were conducted with a significance level of 5%.
RESULTS
Panoramic radiographs in posteroanterior and lateral views were evaluated in 49 patients with adolescent idiopathic scoliosis, of which 34 were female (69.4%), and 15 were male (30.6%). The ages ranged from 10 to 17. The cervical sagittal parameters were evaluated, and the results were submitted for statistical analysis (Table 1).
There was an inverse correlation between the T1-T12 kyphosis and the Cobb C2-C7 (P=0.027). In addition, an inverse relationship was also observed between the inclination of T1 and Cobb C2-C7 (P<0.001). (Table 2). There was also a direct correlation between the Cobb of the proximal thoracic curve and the Cobb C2-C7 (p = 0.038).
Lenke 2 and Lenke 4 curves showed changes in the parameters for evaluating sagittal alignment, as evidenced in Table 3.
Correlations between the Lenke classification and the evaluated cervical column measurements.
The inclination of T1 varied significantly about the sagittal modifier (p<0.05). This parameter varied according to all types of modifiers (Table 5 and Table 6).
Statistical analysis of the sagittal modifier and its relationship with the cervical column variables.
DISCUSSION
Although idiopathic scoliosis presents cervical changes that are clinically perceived during patient treatment and follow-up, these changes have been little analyzed in the current literature until now.9 This study presents important information to establish a correlation between cervical sagittal alignment and the different curve patterns.
Cervical lordosis is defined as an angle less than −2.5° between the lower terminal plates of C2-C7 when measuring the Cobb angle. The kyphosis, in turn, is defined when this angle is greater than +2.5°. Patients with a Cobb angle range between −2.5 and +2.5 degrees are considered to have a straightened cervical spine.7 The patients evaluated in this study presented an average value of cervical lordosis of -2.0 (Table 1), considered a cervical straightening that evidences a loss of lordosis in patients with idiopathic scoliosis.4,7
The value of GOS-C7 is defined as 43.6 ± 23.7 mm.9 In the patients evaluated in this study, the average value of GOS-C7 was 70mm (Table 1), demonstrating an anterior projection of the skull in patients with idiopathic scoliosis.
The skull projection in patients with idiopathic scoliosis found in this study has already been described in the literature.10 Still, it has not been evidenced, until the present moment, one relationship between this alteration and the early appearance of symptoms or cervical degeneration in these patients. Furthermore, despite showing an increased average of values in our study, the GOS-C7 variable did not demonstrate a relationship with the loss of cervical lordosis (P=0.832). These findings suggest, therefore, that new studies are necessary to elucidate the real importance of the previous projection of the skull in idiopathic scoliosis.
Recent studies have investigated new cervical parameters,11 introducing the concept of the angle between the cervical version and the angle of the thoracic “Inlet” (Cervical version and ATI). A relationship was established that defines ATI as having a value equal to the sum of the slope of T1 with the cervical version (ATI = T1 SLOPE + NT).7
The correlation between these variables also indicates that a smaller ATI creates a smaller T1 inclination to maintain the physiological cervical version and vice versa. The ATI and the inclination of T1 can be used as parameters for evaluating sagittal alignment, predicting physiological alignment, and guiding the correction of cervical spine deformity. This fact can be perceived by increased thoracic kyphosis and decreased cervical kyphosis in patients undergoing surgical correction. The inclination of T1 determines the amount of subaxial lordosis needed to keep the head’s center of gravity in a balanced position. It varies according to the global sagittal alignment of the spine, related to the SVA C7-S1 and the kyphosis present in the thoracic spine.4,5,7
According to Janusz et al.,12 the average values of the inclination of T1, the cervical version, and the ATI are ATI 71.7 ± 9.5; the inclination of T1 26.7 ± 6.3; and cervical version 44.9 ± 7.2,
The values of ATI, T1 inclination, and cervical version according to Weng et al.13 are: 78.0, 33.2, and 44.88, respectively.
In our study, the cervical version angle and the ATI presented higher values than those found in the literature, with an average of 58.8 for the cervical version and 81.8 for the ATI (Table 1), which evidences a modification of the cervical position about the cervicothoracic transition region in these patients.14,15 This change causes a loss of sagittal cervical alignment in patients with idiopathic scoliosis, being verified by the decrease of cervical lordosis and by the modification of the cervical parameters (ATI, Cervical Version, GOS-C7) about the reference values in the literature.7,12,13
This work had an inverse correlation between the T1-T12 kyphosis and the C2-C7 Cobb (P=0.027). Furthermore, an inverse relationship was also observed between the inclination of T1 and Cobb C2-C7 (P<0.001) (Table 2). These changes evidence that in idiopathic scoliosis, the increase in thoracic kyphosis, as well as the increase in the value of the inclination of T1, causes the loss of cervical lordosis in the lower cervical segments and the presence of kyphosis in the middle cervical segments, which corroborates previous findings in the literature.2,10
The Cobb C2-C7 showed a statistically significant relationship (p=0.038) with the Cobb of the proximal thoracic curve. Such a finding suggests that the involvement of the upper cervical spine is related to changes in cervical lordosis. Furthermore, the Lenke 2 and Lenke 4 curves showed variations in the values of cervical lordosis (−2.0 and −2.3, respectively), highlighting a straightening in cervical lordosis in this type of curve pattern. It is possible to infer, therefore, that when the proximal thoracic spine was involved, there was a decrease in cervical lordosis. Such a relationship has not been previously described in the literature, and due to the scarce volume of publications on the subject, the few existing publications diverge on the relationship between sagittal alignment and the types of Lenke curves 1-6. Since Liu et al., in their recent publication, found no correlation between cervical alignment and the Cobb of C2-7, main thoracic curve, proximal thoracic curve, and lumbar curve for each group of AIS of Lenke et al. from 1 to 6.5
The lumbar modifier showed no relationship with the variables of cervical sagittal alignment (Table 4). This is a predictable finding since this modifier is obtained through a measurement taken in the coronal plane, not the sagittal.
The inclination of T1 showed a relationship with all variations of the sagittal modifier (P=0.024) (table 5 and Table 6). It was the parameter that showed the most statistical relationship with the other variables of the cervical sagittal alignment of the evaluated patients, which suggests that this variable should be taken into account in the assessment of these patients and that changes in its value should be carefully monitored in the follow-up of the pathology. Therefore, the inclination of T1, along with the inclination of C7, are the main parameters that influence the cervical shape.16,3 Based on these findings, special attention is recommended to the cervical sagittal alignment during the treatment of these patients.
CONCLUSION
The values found for the cervical lordosis of the patients in this study demonstrate a loss of cervical sagittal alignment in patients with idiopathic scoliosis. Curves LENKE 2 and LENKE 4 are the ones that most present a relationship with the changes in the sagittal cervical parameters in patients with idiopathic scoliosis and should be carefully observed. The inclination of T1 has an important relationship with the changes in sagittal alignment in these patients, and it is recommended to take its measurement into account in the management of idiopathic scoliosis.
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