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Scoliosis: evidence-based diagnostic evaluation
Neuroimag Clin N Am 13 (2003) 335 – 341
Scoliosis: evidence-based diagnostic evaluation Diego Jaramillo, MD, MPHa,*, Tina Young Poussaint, MDb, Brian E. Grottkau, MDc a
Division of Pediatric Radiology, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA b Department of Radiology, Boston Children’s Hospital, 300 Longwood Avenue, Boston, MA 02115, USA c Division of Pediatric Orthopaedics, Department of Orthopaedics, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
Scoliosis is defined as an abnormal spinal curvature most apparent in the coronal plane. It is associated with axial rotation and with abnormal curvature in the sagittal plane, typically lordosis, but sometimes kyphosis. Scoliosis is a common spinal abnormality in childhood and adolescence and a significant source of pain, suffering, and disability in adults. Scoliosis can be classified as congenital, neuromuscular, degenerative, or idiopathic. Most pediatric cases fall into the idiopathic category. Idiopathic scoliosis is further classified according to the age at which the disease is manifested: infantile (from birth to 3 years), juvenile (4 to 9 years), and adolescent (10 years and beyond) [1]. Congenital scoliosis is caused by vertebral abnormalities of embryologic origin [2]. Scoliosis can also occur in association with diseases such as neurofibromatosis and Marfan syndrome. In all types of scoliosis, the role of imaging is to detect and characterize the curve and its severity, to monitor disease progression and track changes associated with therapy, and to identify those cases in which occult etiologies exist.
Epidemiology Adolescent idiopathic scoliosis, by far the most common form of the disease, has a prevalence between 0.5% [3] and 3% [3,4] and occurs predominantly in
* Corresponding author. E-mail address: [email protected] (D. Jaramillo).
females. In a study of 15,799 children and young adolescents in the United Kingdom, Stirling et al [3] found that the prevalence ratio of girls to boys was 5.2 [95% confidence interval (CI), 2.9 – 9.5]. In a screening study of 5303 children, Dickson [5] found that progressive scoliosis (greater than 10 degrees and progressing by 5 degrees or more a year) was present in 3.2% of girls and 1% of boys. The more severe the curve, the greater the predominance of girls over boys. In a study of 26,947 students, Rogala et al [6] found that for curves ranging from 6 to 10 degrees, the girlto-boy ratio was 1 to 1, whereas the ratio was 5.4 to 1 for curves greater than 20 degrees. Infantile scoliosis constitutes approximately 8% of idiopathic scoliosis [7] and has a male predominance. Juvenile scoliosis, representing 18% of the idiopathic curves [7], includes cases that fall in between the other two categories. Congenital scoliosis is caused by a failure of formation or a failure of segmentation of spinal elements. In a series of 60 cases of congenital scoliosis, Shahcheraghi and Hobbi [2] found that the most common type of abnormality was a hemivertebra (failure of formation), and that the most severe deformity was associated with a unilateral unsegmented bar (failure of segmentation) with a contralateral hemivertebra. The etiology of adolescent scoliosis remains a puzzle; however, some principles are generally agreed upon [8]: The progression of scoliosis is related to severity and skeletal maturity. The younger the onset and the greater the severity of the curve, the faster the progression. Although previously it
1052-5149/03/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S1052-5149(03)00023-6
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D. Jaramillo et al / Neuroimag Clin N Am 13 (2003) 335–341
was believed that scoliosis remained stable after skeletal maturity was attained, Weinstein and Ponseti [9] demonstrated that 68% of curves worsened after maturity. The typical scoliosis curve is not associated with pain or neurologic signs and symptoms. Painful curves, especially if rapidly progressive or if associated with an atypical curve pattern, are frequently caused by underlying diseases [10]. Less than 10% of the curves require treatment [8]. Patients with loss of thoracic kyphosis and double curve patterns experience more rapid progression of the curvature [8].
Radiographic evaluation of scoliosis Although scoliosis has traditionally been considered an abnormality in the coronal plane, the rotational component of the deformity and the coexistent deformity in the sagittal plane (usually, a decrease in the normal thoracic kyphosis) should be assessed before beginning treatment. The assessment of the abnormality in the frontal radiograph is usually performed by measuring the Cobb angle, which is defined by the intersection of the perpendiculars to the upper end plate of the most tilted cephalad vertebra and the lower end plate of the most tilted caudal vertebra of the curve. The following sections describe the evidence behind the most important challenges in radiographic evaluation.
Evidence-based analysis and literature review
Level 1
The authors performed a MEDLINE search using Ovid (Wolters Kluwer US Corporation, New York, NY) and PubMed (National Library of Medicine, Bethesda, MD) for data relevant to the diagnostic performance and accuracy of clinical and radiographic examination of patients with scoliosis. The diagnostic performance of the clinical examination (history and physical examination) was based on a systematic literature review performed using MEDLINE during the years 1966 to June 2002. The clinical examination search strategy used the following statements: (1) scoliosis, (2) clinical examination, (3) epidemiology OR physical examination OR surgery, (4) 1 AND 2, and (5) 1 AND 3. The review of the current diagnostic imaging literature was performed using MEDLINE covering the years 1966 to December 2001. The search strategy used the following key statements and words: (1) scoliosis, (2) diagnostic imaging, and (3) 1 AND 2. Animal studies and non-English articles were excluded. The titles, abstracts, and full text of the relevant articles were reviewed at each step. The methodologic qualities of the articles were rated using the following scale:
No prospective randomized controlled clinical trials or meta-analyses of randomized controlled trials have studied the use of radiographs for the evaluation of scoliosis.
Level 1: evidence was obtained from a welldesigned randomized controlled trial or metaanalysis of randomized controlled trials. Level 2: evidence was obtained from clinical studies, including nonrandomized controlled trials, cohort studies, case – control studies, time series, or uncontrolled prospective studies. Level 3: evidence was obtained from descriptive studies, case series, or reports of expert opinion or expert committees.
Level 2 Many articles have addressed the variability in measurement of the Cobb angle in adolescent idiopathic scoliosis. In a 1990 study by Morrisy et al [11], four orthopedic surgeons performed six measurements on 50 frontal radiographs. The 95% CIs were 4.9 degrees, and the variation was greatest when the end-plate vertebrae were not preselected. The variability is similar for the sagittal and coronal planes. Carman et al [12] had five observers perform two measurements on 28 radiographs showing kyphosis or scoliosis and found 95% CIs of 8 degrees for scoliosis and 7 degrees for kyphosis. A recent study [13] comparing manual versus computer-assisted radiographic measurements (24 radiographs, six observers) found a statistically significant difference between the 95% CIs of manual measurements (3.3 degrees) and computer-generated measurements (2.6 degrees). Variability is greater for congenital scoliosis versus idiopathic scoliosis. Using six observers and 54 radiographs, Loder et al [14] found 95% CIs of 11.8 degrees. Level 3 The contribution of radiologists’ reports of scoliosis radiographs to clinical management was studied by Crockett et al [15]. These investigators retrospectively reviewed 161 charts and analyzed them for the
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presence or absence of information about certain key parameters. There was no mention of how the review was done or whether there was any attempt to correct for bias. The radiologists’ reports were found to be incomplete. For example, 12.6% of the reports mentioned the magnitude of the curve compared with 98.1% of orthopedists’ reports. Similarly, curve levels were documented in 10.6% of reports by radiologists versus in 95.6% by the orthopedists. Radiologists added information in 1.9% of the cases that, although not specified, was not clinically significant [15]. Summary of evidence Radiographic measurements of scoliosis are reproducible, particularly when the levels of the end plates measured are kept constant. Unexpected findings are unusual.
Radiation-induced complications resulting from radiographic monitoring of scoliosis Patients with severe scoliosis are monitored with the use of serial radiographs that expose most of the trunk. The following sections review the evidence behind the most important radiation-induced complications in scoliosis. Level 1 No prospective randomized controlled clinical trials or meta-analyses of randomized controlled trials support or refute the presence of radiation-induced effects in patients evaluated for scoliosis.
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dose. Potential confounding arose because the severity of disease was related to radiation exposure and reproductive history; patients with more severe disease were less likely to become pregnant and had a greater risk of breast cancer. In a large retrospective cohort study of 2039 patients, Levy et al [17] found an excess lifetime cancer risk of 1% to 2% (12 to 25 cases per 1000 population) among women. The same group suggested that supplanting the anteroposterior (AP) view with the posteroanterior (PA) view would result in a three to seven fold reduction in cumulative doses to the thyroid gland and the female breast, three to four fold reductions in the lifetime risk of breast cancer, and a halving of the lifetime risk of thyroid cancer [18]. The same cohort of women was evaluated for adverse reproductive outcomes [19]. Of the initial group of 1793 young women evaluated for scoliosis between 1960 and 1979, 1292 women returned questionnaires in 1990. This cohort was compared with a reference group of 1134 women selected randomly from the general population. The adolescent idiopathic scoliosis cohort had a higher risk of spontaneous abortions [odds ratio (OR), 1.35; 95% CI, 1.06 – 1.73). The odds of unsuccessful attempts at pregnancy (OR, 1.33; 95% CI, 0.84 – 2.13) and of congenital malformations (OR, 1.2; 95% CI, 0.78 – 1.84) were also higher but not statistically significant. None of these odds increased monotonically by dose to the ovaries. The risk of having a low birth weight baby was not greater than in the general population, but, in the exposed population, there was a relationship between dose and the odds of having low birth weight infants. Level 3
Level 2 In 2000, Morin Doody et al [16] published a retrospective cohort study of 5573 female patients with scoliosis diagnosed before the age of 20 years. The average length of follow-up was 40.1 years, with complete follow-up in 89%. The average number of examinations per patient was 24.7 (range, 0 – 618), and the mean estimated cumulative radiation dose to the breast was 10.8 cGy (range, 0 – 170). Seventyseven breast cancer deaths were observed compared with 45.6 expected deaths on the basis of United States mortality rates. Women with scoliosis had a 1.7-fold risk of dying of breast cancer (95% CI, 1.3 – 2.1) when compared with the general population. The data suggested that radiation was the causative factor, with risk increasing significantly with the number of radiographic exposures and the cumulative radiation
A recent study [20] showed that the radiation dose related to scoliosis follow-up was relatively low when compared with the dose from other types of radiographic examinations. An average-sized patient (50 kg) received an effective dose of approximately 140 microSv, 80% of that to the abdomen. This result conflicted with the work of Almen and Mattsson [21], who found that scoliosis films delivered relatively high-absorbed doses to radiation-sensitive organs, although an optimized frontal scoliosis radiograph gave a much lower effective dose, about 0.05 mSv (PA view). Digital radiography seems to reduce radiation exposure. The results are varied [22 – 24], and the technology is evolving. Recent studies report an 18-fold reduction with some systems [25] versus an almost twofold increase with others [26].
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Summary of evidence Radiographic monitoring of scoliosis results in a clear increase in the radiation-induced cancer risk, particularly to the breast. It also results in a high dose of radiation to the ovaries and worsens reproductive outcome in females. For these reasons, it is crucial to reduce the radiation exposure. Using the PA projection greatly decreases exposure, and some digital systems also reduce radiation.
Use of magnetic resonance imaging for severe idiopathic scoliosis There is increasing concern about the association of scoliosis with structural abnormalities of the neural axis. This concern has led to controversy regarding when to use MR imaging in scoliosis. The following sections present the evidence regarding MR imaging in typical adolescent idiopathic scoliosis and in atypical curves. Level 1 Cheng et al [27] studied 36 healthy control subjects, 135 patients with moderately severe adolescent idiopathic scoliosis (Cobb angle less than 45 degrees), and 29 similar patients with Cobb angles greater than 45 degrees. All of the patients were evaluated prospectively with MR imaging looking specifically for tonsillar ectopia and with somatosensory-evoked potentials. Tonsillar herniation was found in none of the controls versus 4 of 135 (3%) and 8 of 29 (27.6%) of the two scoliotic groups (P < 0.001). Similarly, the percentages of patients with abnormal somatosensoryevoked potentials were 0%, 11.9%, and 27.6%, respectively. There was a significant association between tonsillar ectopia and abnormal somatosensory function (P < 0.001; correlation coefficient, 0.672). Tonsillar ectopia was defined as any inferior displacement of the tonsils, and none of the patients had a displacement greater than 5 mm, which is considered the usual threshold for the diagnosis [28 – 30].
were evaluated from the base of the skull to the sacrum. Seven patients had abnormal MR images, including two with syrinx, four with Chiari malformation type I, and one with a fatty vertebral body. None of them required specific treatment for these findings. In four other cases, equivocal MR findings necessitated additional work-up. In a similar prospective doubleblinded study of 140 patients evaluated preoperatively, Winter et al [32] found four patients with abnormalities, three with Chiari I malformations and one with a small syrinx, none of whom required treatment. In another study of MR examinations performed preoperatively, Maiocco et al [33] found 2 of 45 patients with syrinx, one requiring decompression. To study whether the severity of the curve increased the risk of associated abnormalities, O’Brien et al [34] performed MR evaluation on 33 consecutive patients with adolescent idiopathic scoliosis and Cobb angles greater than 70 degrees. No neural axis abnormalities were found. Liljenqvist et al [35] analyzed 307 vertebra in 26 consecutive patients using MR imaging and found that the pedicles were significantly narrower on the convex side of the curve. The epidural space on the concave side of the curve was 1 mm or less, whereas it was between 3 and 5 mm on the convex side. This observation raises concerns regarding pedicle – screw instrumentation, because, in the apex of the concavity, the pedicles are small and immediately adjacent to the cord. Level 3 Because of the abundance of evidence obtained from level 2 studies, no level 3 studies are discussed herein. Summary of evidence Minimal tonsillar ectopia (< 5 mm) is significantly prevalent in scoliosis and correlates with abnormalities in somatosensory-evoked potential and with the severity of scoliosis. Otherwise, there is a paucity of significant findings on MR images of patients evaluated for idiopathic scoliosis, even when it is severe.
Level 2 Several studies have addressed the prevalence of MR abnormalities in patients with severe idiopathic scoliosis who are otherwise asymptomatic. Do et al [31] studied a consecutive series of 327 patients with idiopathic scoliosis requiring surgical intervention (average preoperative curve of 57 degrees) but without neurologic findings. The patients, aged 10 to 19 years,
Use of magnetic resonance imaging for higher-risk subgroups of scoliosis Level 1 No prospective randomized controlled clinical trials or meta-analyses of randomized controlled tri-
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als support or refute the use of MR imaging in patients with scoliosis at higher risk for neurologic abnormalities.
Level 2 Several studies have shown that, with scoliosis types that are different from the typical adolescent idiopathic form, there is a high prevalence of neural abnormalities. Of 30 consecutive children with congenital scoliosis studied by Prahinski et al [36], 9 had abnormal MR findings, primarily tethered cord and syringomyelia. Of these children, one required release of the tethered cord and one correction of a diastematomyelia. Two studies of prepubertal children suggest a high incidence of neural abnormalities in juvenile and infantile scoliosis. In a study of 26 consecutive children aged less than 11 years, Lewonowski et al [37] found five (19.2%) with abnormalities of the cord. Three required surgical intervention, two with hydromyelia and one with a mass [37]. Gupta et al [38] found that 6 of 34 patients under 10 years of age studied prospectively had neural axis abnormalities, including two patients with syrinx requiring syringopleural shunting (one with a Chiari I malformation). Other abnormalities included dural ectasia, tethered cord, and a brainstem astrocytoma.
Level 3 In a retrospective review of 95 patients with idiopathic scoliosis who had been studied for various indications, Schwend et al [39] found that 12 had a syrinx, one a cord astrocytoma, and one dural ectasia. Left thoracic scoliosis was the most important predictor of abnormality (10 abnormalities in 43 patients). Mejia, Schwend, and others [40] then performed a prospective study (level 2) of 29 consecutive patients with idiopathic left thoracic scoliosis, finding only two with syrinx and no other abnormalities. Barnes et al [10] retrospectively analyzed 30 patients with atypical idiopathic scoliosis and found 17 abnormalities in 11 patients, including seven cases of syringohydromyelia and five Chiari I malformations.
Summary of evidence Unlike adolescent idiopathic scoliosis, juvenile and infantile idiopathic scoliosis and congenital scoliosis have a high incidence of neural axis abnormalities.
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Recommendations Magnetic resonance imaging is not recommended in patients presenting with adolescent idiopathic scoliosis, regardless of the severity of the disease. The data suggest that there is no need for preoperative MR evaluation in a female with adolescent idiopathic scoliosis, normal neurologic examination, and a typical curve, although this conclusion remains controversial. Patients with juvenile and infantile idiopathic scoliosis and those with congenital scoliosis have a high risk for neural axis abnormalities and should undergo MR imaging. Patients with adolescent idiopathic scoliosis but atypical findings (pain, rapid progression, development of neurologic signs and symptoms) and those with scoliosis related to other pathologies such as neurofibromatosis also should be studied with MR imaging [41].
Future directions of research The cost-effectiveness of using MR imaging in the various clinical scenarios has not been established. More research is needed to elucidate the relationship between apparently subclinical Chiari I malformation and idiopathic scoliosis.
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[8] Weinstein SL. Natural history. Spine 1999;24(24): 2592 – 600. [9] Weinstein SL, Ponseti IV. Curve progression in idiopathic scoliosis. J Bone Joint Surg Am 1983;65(4): 447 – 55. [10] Barnes PD, Brody JD, Jaramillo D, Akbar JU, Emans JB. Atypical idiopathic scoliosis: MR imaging evaluation. Radiology 1993;186(1):247 – 53. [11] Morrissy RT, Goldsmith GS, Hall EC, Kehl D, Cowie GH. Measurement of the Cobb angle on radiographs of patients who have scoliosis: evaluation of intrinsic error. J Bone Joint Surg Am 1990;72(3):320 – 7. [12] Carman DL, Browne RH, Birch JG. Measurement of scoliosis and kyphosis radiographs: intraobserver and interobserver variation. J Bone Joint Surg Am 1990; 72(3):328 – 33. [13] Shea KG, Stevens PM, Nelson M, Smith JT, Masters KS, Yandow S. A comparison of manual versus computer-assisted radiographic measurement: intraobserver measurement variability for Cobb angles. Spine 1998; 23(5):551 – 5. [14] Loder RT, Urquhart A, Steen H, Graziano G, Hensinger RN, Schlesinger A, et al. Variability in Cobb angle measurements in children with congenital scoliosis. J Bone Joint Surg Br 1995;77(5):768 – 70. [15] Crockett HC, Wright JM, Burke S, Boachie-Adjei O. Idiopathic scoliosis: the clinical value of radiologists’ interpretation of pre- and postoperative radiographs with interobserver and interdisciplinary variability. Spine 1999;24(19):2007 – 9; discussion, 2010. [16] Morin Doody M, Lonstein JE, Stovall M, Hacker DG, Luckyanov N, Land CE. Breast cancer mortality after diagnostic radiography: findings from the US Scoliosis Cohort Study. Spine 2000;25(16):2052 – 63. [17] Levy AR, Goldberg MS, Hanley JA, Mayo NE, Poitras B. Projecting the lifetime risk of cancer from exposure to diagnostic ionizing radiation for adolescent idiopathic scoliosis. Health Phys 1994;66(6):621 – 33. [18] Levy AR, Goldberg MS, Mayo NE, Hanley JA, Poitras B. Reducing the lifetime risk of cancer from spinal radiographs among people with adolescent idiopathic scoliosis. Spine 1996;21(13):1540 – 7; discussion, 1548. [19] Goldberg MS, Mayo NE, Levy AR, Scott SC, Poitras B. Adverse reproductive outcomes among women exposed to low levels of ionizing radiation from diagnostic radiography for adolescent idiopathic scoliosis. Epidemiology 1998;9(3):271 – 8. [20] Chamberlain CC, Huda W, Hojnowski LS, Perkins A, Scaramuzzino A. Radiation doses to patients undergoing scoliosis radiography. Br J Radiol 2000; 73(872):847 – 53. [21] Almen AJ, Mattsson S. Dose distribution at radiographic examination of the spine in pediatric radiology. Spine 1996;21(6):750 – 6. [22] Kalmar JA, Jones JP, Merritt CR. Low-dose radiography of scoliosis in children: a comparison of methods. Spine 1994;19(7):818 – 23. [23] Kling Jr TF, Cohen MJ, Lindseth RE, De Rosa GP.
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Scoliosis: evidence-based diagnostic evaluation Diego Jaramillo, MD, MPHa,*, Tina Young Poussaint, MDb, Brian E. Grottkau, MDc a
Division of Pediatric Radiology, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA b Department of Radiology, Boston Children’s Hospital, 300 Longwood Avenue, Boston, MA 02115, USA c Division of Pediatric Orthopaedics, Department of Orthopaedics, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
Scoliosis is defined as an abnormal spinal curvature most apparent in the coronal plane. It is associated with axial rotation and with abnormal curvature in the sagittal plane, typically lordosis, but sometimes kyphosis. Scoliosis is a common spinal abnormality in childhood and adolescence and a significant source of pain, suffering, and disability in adults. Scoliosis can be classified as congenital, neuromuscular, degenerative, or idiopathic. Most pediatric cases fall into the idiopathic category. Idiopathic scoliosis is further classified according to the age at which the disease is manifested: infantile (from birth to 3 years), juvenile (4 to 9 years), and adolescent (10 years and beyond) [1]. Congenital scoliosis is caused by vertebral abnormalities of embryologic origin [2]. Scoliosis can also occur in association with diseases such as neurofibromatosis and Marfan syndrome. In all types of scoliosis, the role of imaging is to detect and characterize the curve and its severity, to monitor disease progression and track changes associated with therapy, and to identify those cases in which occult etiologies exist.
Epidemiology Adolescent idiopathic scoliosis, by far the most common form of the disease, has a prevalence between 0.5% [3] and 3% [3,4] and occurs predominantly in
* Corresponding author. E-mail address: [email protected] (D. Jaramillo).
females. In a study of 15,799 children and young adolescents in the United Kingdom, Stirling et al [3] found that the prevalence ratio of girls to boys was 5.2 [95% confidence interval (CI), 2.9 – 9.5]. In a screening study of 5303 children, Dickson [5] found that progressive scoliosis (greater than 10 degrees and progressing by 5 degrees or more a year) was present in 3.2% of girls and 1% of boys. The more severe the curve, the greater the predominance of girls over boys. In a study of 26,947 students, Rogala et al [6] found that for curves ranging from 6 to 10 degrees, the girlto-boy ratio was 1 to 1, whereas the ratio was 5.4 to 1 for curves greater than 20 degrees. Infantile scoliosis constitutes approximately 8% of idiopathic scoliosis [7] and has a male predominance. Juvenile scoliosis, representing 18% of the idiopathic curves [7], includes cases that fall in between the other two categories. Congenital scoliosis is caused by a failure of formation or a failure of segmentation of spinal elements. In a series of 60 cases of congenital scoliosis, Shahcheraghi and Hobbi [2] found that the most common type of abnormality was a hemivertebra (failure of formation), and that the most severe deformity was associated with a unilateral unsegmented bar (failure of segmentation) with a contralateral hemivertebra. The etiology of adolescent scoliosis remains a puzzle; however, some principles are generally agreed upon [8]: The progression of scoliosis is related to severity and skeletal maturity. The younger the onset and the greater the severity of the curve, the faster the progression. Although previously it
1052-5149/03/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S1052-5149(03)00023-6
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was believed that scoliosis remained stable after skeletal maturity was attained, Weinstein and Ponseti [9] demonstrated that 68% of curves worsened after maturity. The typical scoliosis curve is not associated with pain or neurologic signs and symptoms. Painful curves, especially if rapidly progressive or if associated with an atypical curve pattern, are frequently caused by underlying diseases [10]. Less than 10% of the curves require treatment [8]. Patients with loss of thoracic kyphosis and double curve patterns experience more rapid progression of the curvature [8].
Radiographic evaluation of scoliosis Although scoliosis has traditionally been considered an abnormality in the coronal plane, the rotational component of the deformity and the coexistent deformity in the sagittal plane (usually, a decrease in the normal thoracic kyphosis) should be assessed before beginning treatment. The assessment of the abnormality in the frontal radiograph is usually performed by measuring the Cobb angle, which is defined by the intersection of the perpendiculars to the upper end plate of the most tilted cephalad vertebra and the lower end plate of the most tilted caudal vertebra of the curve. The following sections describe the evidence behind the most important challenges in radiographic evaluation.
Evidence-based analysis and literature review
Level 1
The authors performed a MEDLINE search using Ovid (Wolters Kluwer US Corporation, New York, NY) and PubMed (National Library of Medicine, Bethesda, MD) for data relevant to the diagnostic performance and accuracy of clinical and radiographic examination of patients with scoliosis. The diagnostic performance of the clinical examination (history and physical examination) was based on a systematic literature review performed using MEDLINE during the years 1966 to June 2002. The clinical examination search strategy used the following statements: (1) scoliosis, (2) clinical examination, (3) epidemiology OR physical examination OR surgery, (4) 1 AND 2, and (5) 1 AND 3. The review of the current diagnostic imaging literature was performed using MEDLINE covering the years 1966 to December 2001. The search strategy used the following key statements and words: (1) scoliosis, (2) diagnostic imaging, and (3) 1 AND 2. Animal studies and non-English articles were excluded. The titles, abstracts, and full text of the relevant articles were reviewed at each step. The methodologic qualities of the articles were rated using the following scale:
No prospective randomized controlled clinical trials or meta-analyses of randomized controlled trials have studied the use of radiographs for the evaluation of scoliosis.
Level 1: evidence was obtained from a welldesigned randomized controlled trial or metaanalysis of randomized controlled trials. Level 2: evidence was obtained from clinical studies, including nonrandomized controlled trials, cohort studies, case – control studies, time series, or uncontrolled prospective studies. Level 3: evidence was obtained from descriptive studies, case series, or reports of expert opinion or expert committees.
Level 2 Many articles have addressed the variability in measurement of the Cobb angle in adolescent idiopathic scoliosis. In a 1990 study by Morrisy et al [11], four orthopedic surgeons performed six measurements on 50 frontal radiographs. The 95% CIs were 4.9 degrees, and the variation was greatest when the end-plate vertebrae were not preselected. The variability is similar for the sagittal and coronal planes. Carman et al [12] had five observers perform two measurements on 28 radiographs showing kyphosis or scoliosis and found 95% CIs of 8 degrees for scoliosis and 7 degrees for kyphosis. A recent study [13] comparing manual versus computer-assisted radiographic measurements (24 radiographs, six observers) found a statistically significant difference between the 95% CIs of manual measurements (3.3 degrees) and computer-generated measurements (2.6 degrees). Variability is greater for congenital scoliosis versus idiopathic scoliosis. Using six observers and 54 radiographs, Loder et al [14] found 95% CIs of 11.8 degrees. Level 3 The contribution of radiologists’ reports of scoliosis radiographs to clinical management was studied by Crockett et al [15]. These investigators retrospectively reviewed 161 charts and analyzed them for the
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presence or absence of information about certain key parameters. There was no mention of how the review was done or whether there was any attempt to correct for bias. The radiologists’ reports were found to be incomplete. For example, 12.6% of the reports mentioned the magnitude of the curve compared with 98.1% of orthopedists’ reports. Similarly, curve levels were documented in 10.6% of reports by radiologists versus in 95.6% by the orthopedists. Radiologists added information in 1.9% of the cases that, although not specified, was not clinically significant [15]. Summary of evidence Radiographic measurements of scoliosis are reproducible, particularly when the levels of the end plates measured are kept constant. Unexpected findings are unusual.
Radiation-induced complications resulting from radiographic monitoring of scoliosis Patients with severe scoliosis are monitored with the use of serial radiographs that expose most of the trunk. The following sections review the evidence behind the most important radiation-induced complications in scoliosis. Level 1 No prospective randomized controlled clinical trials or meta-analyses of randomized controlled trials support or refute the presence of radiation-induced effects in patients evaluated for scoliosis.
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dose. Potential confounding arose because the severity of disease was related to radiation exposure and reproductive history; patients with more severe disease were less likely to become pregnant and had a greater risk of breast cancer. In a large retrospective cohort study of 2039 patients, Levy et al [17] found an excess lifetime cancer risk of 1% to 2% (12 to 25 cases per 1000 population) among women. The same group suggested that supplanting the anteroposterior (AP) view with the posteroanterior (PA) view would result in a three to seven fold reduction in cumulative doses to the thyroid gland and the female breast, three to four fold reductions in the lifetime risk of breast cancer, and a halving of the lifetime risk of thyroid cancer [18]. The same cohort of women was evaluated for adverse reproductive outcomes [19]. Of the initial group of 1793 young women evaluated for scoliosis between 1960 and 1979, 1292 women returned questionnaires in 1990. This cohort was compared with a reference group of 1134 women selected randomly from the general population. The adolescent idiopathic scoliosis cohort had a higher risk of spontaneous abortions [odds ratio (OR), 1.35; 95% CI, 1.06 – 1.73). The odds of unsuccessful attempts at pregnancy (OR, 1.33; 95% CI, 0.84 – 2.13) and of congenital malformations (OR, 1.2; 95% CI, 0.78 – 1.84) were also higher but not statistically significant. None of these odds increased monotonically by dose to the ovaries. The risk of having a low birth weight baby was not greater than in the general population, but, in the exposed population, there was a relationship between dose and the odds of having low birth weight infants. Level 3
Level 2 In 2000, Morin Doody et al [16] published a retrospective cohort study of 5573 female patients with scoliosis diagnosed before the age of 20 years. The average length of follow-up was 40.1 years, with complete follow-up in 89%. The average number of examinations per patient was 24.7 (range, 0 – 618), and the mean estimated cumulative radiation dose to the breast was 10.8 cGy (range, 0 – 170). Seventyseven breast cancer deaths were observed compared with 45.6 expected deaths on the basis of United States mortality rates. Women with scoliosis had a 1.7-fold risk of dying of breast cancer (95% CI, 1.3 – 2.1) when compared with the general population. The data suggested that radiation was the causative factor, with risk increasing significantly with the number of radiographic exposures and the cumulative radiation
A recent study [20] showed that the radiation dose related to scoliosis follow-up was relatively low when compared with the dose from other types of radiographic examinations. An average-sized patient (50 kg) received an effective dose of approximately 140 microSv, 80% of that to the abdomen. This result conflicted with the work of Almen and Mattsson [21], who found that scoliosis films delivered relatively high-absorbed doses to radiation-sensitive organs, although an optimized frontal scoliosis radiograph gave a much lower effective dose, about 0.05 mSv (PA view). Digital radiography seems to reduce radiation exposure. The results are varied [22 – 24], and the technology is evolving. Recent studies report an 18-fold reduction with some systems [25] versus an almost twofold increase with others [26].
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Summary of evidence Radiographic monitoring of scoliosis results in a clear increase in the radiation-induced cancer risk, particularly to the breast. It also results in a high dose of radiation to the ovaries and worsens reproductive outcome in females. For these reasons, it is crucial to reduce the radiation exposure. Using the PA projection greatly decreases exposure, and some digital systems also reduce radiation.
Use of magnetic resonance imaging for severe idiopathic scoliosis There is increasing concern about the association of scoliosis with structural abnormalities of the neural axis. This concern has led to controversy regarding when to use MR imaging in scoliosis. The following sections present the evidence regarding MR imaging in typical adolescent idiopathic scoliosis and in atypical curves. Level 1 Cheng et al [27] studied 36 healthy control subjects, 135 patients with moderately severe adolescent idiopathic scoliosis (Cobb angle less than 45 degrees), and 29 similar patients with Cobb angles greater than 45 degrees. All of the patients were evaluated prospectively with MR imaging looking specifically for tonsillar ectopia and with somatosensory-evoked potentials. Tonsillar herniation was found in none of the controls versus 4 of 135 (3%) and 8 of 29 (27.6%) of the two scoliotic groups (P < 0.001). Similarly, the percentages of patients with abnormal somatosensoryevoked potentials were 0%, 11.9%, and 27.6%, respectively. There was a significant association between tonsillar ectopia and abnormal somatosensory function (P < 0.001; correlation coefficient, 0.672). Tonsillar ectopia was defined as any inferior displacement of the tonsils, and none of the patients had a displacement greater than 5 mm, which is considered the usual threshold for the diagnosis [28 – 30].
were evaluated from the base of the skull to the sacrum. Seven patients had abnormal MR images, including two with syrinx, four with Chiari malformation type I, and one with a fatty vertebral body. None of them required specific treatment for these findings. In four other cases, equivocal MR findings necessitated additional work-up. In a similar prospective doubleblinded study of 140 patients evaluated preoperatively, Winter et al [32] found four patients with abnormalities, three with Chiari I malformations and one with a small syrinx, none of whom required treatment. In another study of MR examinations performed preoperatively, Maiocco et al [33] found 2 of 45 patients with syrinx, one requiring decompression. To study whether the severity of the curve increased the risk of associated abnormalities, O’Brien et al [34] performed MR evaluation on 33 consecutive patients with adolescent idiopathic scoliosis and Cobb angles greater than 70 degrees. No neural axis abnormalities were found. Liljenqvist et al [35] analyzed 307 vertebra in 26 consecutive patients using MR imaging and found that the pedicles were significantly narrower on the convex side of the curve. The epidural space on the concave side of the curve was 1 mm or less, whereas it was between 3 and 5 mm on the convex side. This observation raises concerns regarding pedicle – screw instrumentation, because, in the apex of the concavity, the pedicles are small and immediately adjacent to the cord. Level 3 Because of the abundance of evidence obtained from level 2 studies, no level 3 studies are discussed herein. Summary of evidence Minimal tonsillar ectopia (< 5 mm) is significantly prevalent in scoliosis and correlates with abnormalities in somatosensory-evoked potential and with the severity of scoliosis. Otherwise, there is a paucity of significant findings on MR images of patients evaluated for idiopathic scoliosis, even when it is severe.
Level 2 Several studies have addressed the prevalence of MR abnormalities in patients with severe idiopathic scoliosis who are otherwise asymptomatic. Do et al [31] studied a consecutive series of 327 patients with idiopathic scoliosis requiring surgical intervention (average preoperative curve of 57 degrees) but without neurologic findings. The patients, aged 10 to 19 years,
Use of magnetic resonance imaging for higher-risk subgroups of scoliosis Level 1 No prospective randomized controlled clinical trials or meta-analyses of randomized controlled tri-
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als support or refute the use of MR imaging in patients with scoliosis at higher risk for neurologic abnormalities.
Level 2 Several studies have shown that, with scoliosis types that are different from the typical adolescent idiopathic form, there is a high prevalence of neural abnormalities. Of 30 consecutive children with congenital scoliosis studied by Prahinski et al [36], 9 had abnormal MR findings, primarily tethered cord and syringomyelia. Of these children, one required release of the tethered cord and one correction of a diastematomyelia. Two studies of prepubertal children suggest a high incidence of neural abnormalities in juvenile and infantile scoliosis. In a study of 26 consecutive children aged less than 11 years, Lewonowski et al [37] found five (19.2%) with abnormalities of the cord. Three required surgical intervention, two with hydromyelia and one with a mass [37]. Gupta et al [38] found that 6 of 34 patients under 10 years of age studied prospectively had neural axis abnormalities, including two patients with syrinx requiring syringopleural shunting (one with a Chiari I malformation). Other abnormalities included dural ectasia, tethered cord, and a brainstem astrocytoma.
Level 3 In a retrospective review of 95 patients with idiopathic scoliosis who had been studied for various indications, Schwend et al [39] found that 12 had a syrinx, one a cord astrocytoma, and one dural ectasia. Left thoracic scoliosis was the most important predictor of abnormality (10 abnormalities in 43 patients). Mejia, Schwend, and others [40] then performed a prospective study (level 2) of 29 consecutive patients with idiopathic left thoracic scoliosis, finding only two with syrinx and no other abnormalities. Barnes et al [10] retrospectively analyzed 30 patients with atypical idiopathic scoliosis and found 17 abnormalities in 11 patients, including seven cases of syringohydromyelia and five Chiari I malformations.
Summary of evidence Unlike adolescent idiopathic scoliosis, juvenile and infantile idiopathic scoliosis and congenital scoliosis have a high incidence of neural axis abnormalities.
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Recommendations Magnetic resonance imaging is not recommended in patients presenting with adolescent idiopathic scoliosis, regardless of the severity of the disease. The data suggest that there is no need for preoperative MR evaluation in a female with adolescent idiopathic scoliosis, normal neurologic examination, and a typical curve, although this conclusion remains controversial. Patients with juvenile and infantile idiopathic scoliosis and those with congenital scoliosis have a high risk for neural axis abnormalities and should undergo MR imaging. Patients with adolescent idiopathic scoliosis but atypical findings (pain, rapid progression, development of neurologic signs and symptoms) and those with scoliosis related to other pathologies such as neurofibromatosis also should be studied with MR imaging [41].
Future directions of research The cost-effectiveness of using MR imaging in the various clinical scenarios has not been established. More research is needed to elucidate the relationship between apparently subclinical Chiari I malformation and idiopathic scoliosis.
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