Spinal Deformity Study Group Research Articles

138 The Schwab-SRS Adult Spinal Deformity Classification

INTRODUCTION: The Schwab-SRS Classification of Adult Spinal Deformity (ASD) is a validated system that provides a common language for the complex pathology of ASD. Classification reliability has been reported; however, correlation with treatment has not been assessed. Purpose: assess association between disability, classification type/modifier and ASD treatment. METHODS: Prospective analysis of consecutive ASD patients from a multi-center spinal deformity study group. Inclusion criteria: age = 18 yrs and scoliosis = 20°, sagittal vertical axis (SVA) = 5 cm, pelvic tilt (PT) = 25° or thoracic kyphosis (TK)> 60°. All patients had 36" standing x-rays. Differences in demographics, health related quality of life (HRQOL; ODI, SRS, SF36), and classification curve type/modifier distribution between operative (OP) and nonoperative (NONOP) treatment were evaluated. RESULTS: 757 patients (mean age 53 yrs, range 18-85) met inclusion criteria. OP (n = 311) were older (mean age 56 vs 51 yrs), had greater BMI (27.7 vs 25.7), more previous surgery (45% vs 19%), and greater Charlson comorbidity index (1.1 vs 0.85) than NONOP (n = 446), respectively (P < 0.05). OP had worse HRQOL scores on all surveys than NONOP (P < 0.05). OP and NONOP had similar coronal alignment (P < 0.05). OP had worse sagittal spinopelvic alignment for all measures than NONOP except cervical lordosis, TK and pelvic incidence (PI). OP had greater percentage of pure sagittal classification (type S; OP = 23%, NON = 14%; P < 0.05). OP had worse grades for all modifier categories: PT (26% vs 16%), PI-lumbar lordosis mismatch (37% vs 21%) and global sagittal alignment (29% vs 9%), OP vs NONOP, respectively (P < 0.05). CONCLUSION: Prospective analysis of OP vs NONOP treated ASD patients demonstrated OP patients were older, had more co-morbidities, greater disability and worse sagittal spinopelvic alignment as defined by the Schwab-SRS Classification subtype and sagittal modifiers. This classification is descriptive, correlates with HRQOL scores, and corresponds to treatment preference for ASD.

Use and Outcomes of Wound Drain in Spinal Fusion for Adolescent Idiopathic Scoliosis

A multicenter retrospective analysis. To evaluate outcomes of closed-suction wound drainage after posterior spinal fusion with instrumentation for adolescent idiopathic scoliosis and to identify surgeon patterns of drain use in this cohort. There is little evidence on the use of drains in spinal surgery, particularly for repair of adolescent idiopathic scoliosis. Studies on hip and knee arthroplasty suggest no advantage to draining. There are few published reports on surgeon technique and rationale for drain use in spinal surgery. Patients were divided into drain and no drain cohorts and followed for 2 years. Primary outcome was complication rate. A separate survey was conducted from surgeons in the Spinal Deformity Study Group to evaluate drain practice patterns. There were 324 drained and 176 undrained patients. Complication rate did not differ between the drain and no drain cohorts in any of the 4 categories (wound infection, neural injury, other infection, and other complication) at any time (all P > 0.1). More drained patients received postoperative transfusions compared with those without a drain (43% vs. 22%, P < 0.001). Of the 50 surgeons in the group, 36 used drains. Half of these did so out of habit. Surgeons tended to place deep drains with bulb suction, without drain manipulation. Half removed drains on the basis of output, whereas half removed them after 1 to 3 days. More patients tended to receive wound drains than not receive wound drains. Drains did not impact complication rate and drained patients received more blood product. There are no universal criteria for draining and practice patterns vary widely.

Reliability of the Spinal Deformity Study Group Classification of Lumbosacral Spondylolisthesis

Reliability study of the computer-assisted SDSG (Spinal Deformity Study Group) classification of lumbosacral spondylolisthesis. To assess the intra- and interobserver reliability of the computer-assisted SDSG classification of lumbosacral spondylolisthesis. The SDSG has proposed a new classification of lumbosacral spondylolisthesis based on slip grade, pelvic incidence (PI), and sacro-pelvic and spinal balance. Three types of low-grade spondylolisthesis are described: low PI (type 1), normal PI (type 2), and high PI (type 3). High-grade spondylolisthesis are defined as type 4 (balanced sacro-pelvis), type 5 (retroverted sacro-pelvis with balanced spine), and type 6 (retroverted sacro-pelvis with unbalanced spine). Full-length standing lateral radiographs of the spine of 40 subjects with lumbosacral spondylolisthesis were reviewed twice by 7 observers. Custom software was used by the observers to identify 7 anatomical landmarks on each radiograph to determine the SDSG type for all subjects. Percentage of agreement and κ coefficients were used to determine the intra- and interobserver reliability. All 6 types of spondylolisthesis described in the computer-assisted SDSG classification were identified. Overall intra- and interobserver agreements were 80% (κ: 0.74) and 71% (κ: 0.65), respectively. The intra- and interobserver agreements associated with computerized determination of slip grade were 92% (κ: 0.83) and 88% (κ: 0.78), respectively. As for computerized determination of sacro-pelvic and spinal balance, intra- and interobserver agreements were 86% (κ: 0.76) and 75% (κ: 0.63) for low-grade slips, whereas they were 88% (κ: 0.80) and 83% (κ: 0.75) for high-grade slips. Substantial intra- and interobserver reliability was found for the computer-assisted SDSG classification, and all 6 types of lumbosacral spondylolisthesis were identified. Refinement of the computer-assisted classification technique is, however, needed to further increase the reliability of the SDSG classification and facilitate its clinical use.

Spino-pelvic sagittal balance of spondylolisthesis: a review and classification.

In L5-S1 spondylolisthesis, it has been clearly demonstrated over the past decade that sacro-pelvic morphology is abnormal and that it can be associated to an abnormal sacro-pelvic orientation as well as to a disturbed global sagittal balance of the spine. The purpose of this article is to review the work done within the Spinal Deformity Study Group (SDSG) over the past decade, which has led to a classification incorporating this recent knowledge. The evidence presented has been derived from the analysis of the SDSG database, a multi-center radiological database of patients with L5-S1 spondylolisthesis, collected from 43 spine surgeons in North America and Europe. The classification defines 6 types of spondylolisthesis based on features that can be assessed on sagittal radiographs of the spine and pelvis: (1) grade of slip, (2) pelvic incidence, and (3) spino-pelvic alignment. A reliability study has demonstrated substantial intra- and inter-observer reliability similar to other currently used classifications for spinal deformity. Furthermore, health-related quality of life measures were found to be significantly different between the 6 types, thus supporting the value of a classification based on spino-pelvic alignment. The clinical relevance is that clinicians need to keep in mind when planning treatment that subjects with L5-S1 spondylolisthesis are a heterogeneous group with various adaptations of their posture. In the current controversy on whether high-grade deformities should or should not be reduced, it is suggested that reduction techniques should preferably be used in subjects with evidence of abnormal posture, in order to restore global spino-pelvic balance and improve the biomechanical environment for fusion.

Reliability and Accuracy Analysis of a New Semiautomatic Radiographic Measurement Software in Adult Scoliosis

Radiographic software measurement analysis in adult scoliosis. To assess the accuracy as well as the intra- and interobserver reliability of measuring different indices on preoperative adult scoliosis radiographs using a novel measurement software that includes a calibration procedure and semiautomatic features to facilitate the measurement process. Scoliosis requires a careful radiographic evaluation to assess the deformity. Manual and computer radiographic process measures have been studied extensively to determine the reliability and reproducibility in adolescent idiopathic scoliosis. Most studies rely on comparing given measurements, which are repeated by the same user or by an expert user. A given measure with a small intra- or interobserver error might be deemed as good repeatability, but all measurements might not be truly accurate because the ground-truth value is often unknown. Thorough accuracy assessment of radiographic measures is necessary to assess scoliotic deformities, compare these measures at different stages or to permit valid multicenter studies. Thirty-four sets of adult scoliosis digital radiographs were measured two times by three independent observers using a novel radiographic measurement software that includes semiautomatic features to facilitate the measurement process. Twenty different measures taken from the Spinal Deformity Study Group radiographic measurement manual were performed on the coronal and sagittal images. Intra- and intermeasurer reliability for each measure was assessed. The accuracy of the measurement software was also assessed using a physical spine model in six different scoliotic configurations as a true reference. The majority of the measures demonstrated good to excellent intra- and intermeasurer reliability, except for sacral obliquity. The standard variation of all the measures was very small: ≤ 4.2° for Cobb angles, ≤ 4.2° for the kyphosis, ≤ 5.7° for the lordosis, ≤ 3.9° for the pelvic angles, and ≤5.3° for the sacral angles. The variability in the linear measurements (distances) was <4 mm. The variance of the measures was 1.7 and 2.6 times greater, respectively, for the angular and linear measures between the inter- and intrameasurer reliability. The image quality positively influenced the intermeasurer reliability especially for the proximal thoracic Cobb angle, T10-L2 lordosis, sacral slope and L5 seating. The accuracy study revealed that on average the difference in the angular measures was < 2° for the Cobb angles, and < 4° for the other angles, except T2-T12 kyphosis (5.3°). The linear measures were all <3.5 mm difference on average. The majority of the measures, which were analyzed in this study demonstrated good to excellent reliability and accuracy. The novel semiautomatic measurement software can be recommended for use for clinical, research or multicenter study purposes.

Brace treatment for adolescent idiopathic scoliosis – Protocols of the Canadian Spinal Deformity Study Group Surgeons

Rigid full-time braces are the most common non-surgical treatment for adolescents with moderate severity of scoliosis and further growth. The Scoliosis Research Society has established guidelines on which patients with adolescent idiopathic scoliosis (AIS) should be treated with a brace. This study surveyed Canadian surgeons on their protocols for prescribing braces for adolescent females with AIS.

Assessment of lumbosacral kyphosis in spondylolisthesis: a computer-assisted reliability study of six measurement techniques

Although recognized as an important aspect in the management of spondylolisthesis, there is no consensus on the most reliable and optimal measure of lumbosacral kyphosis (LSK). Using a custom computer software, four raters evaluated 60 standing lateral radiographs of the lumbosacral spine during two sessions at a 1-week interval. The sample size consisted of 20 normal, 20 low and 20 high grade spondylolisthetic subjects. Six parameters were included for analysis: Boxall's slip angle, Dubousset's lumbosacral angle (LSA), the Spinal Deformity Study Group's (SDSG) LSA, dysplastic SDSG LSA, sagittal rotation (SR), kyphotic Cobb angle (k-Cobb). Intra- and inter-rater reliability for all parameters was assessed using intra-class correlation coefficients (ICC). Correlations between parameters and slip percentage were evaluated with Pearson coefficients. The intra-rater ICC's for all the parameters ranged between 0.81 and 0.97 and the inter-rater ICC's were between 0.74 and 0.98. All parameters except sagittal rotation showed a medium to large correlation with slip percentage. Dubousset's LSA and the k-Cobb showed the largest correlations (r= -0.78 and r= -0.50, respectively). SR was associated with the weakest correlation (r= -0.10). All other parameters had medium correlations with percent slip (r= 0.31-0.43). All measurement techniques provided excellent inter- and intra-rater reliability. Dubousset's LSA showed the strongest correlation with slip grade. This parameter can be used in the clinical setting with PACS software capabilities to assess LSK. A computer-assisted technique is recommended in order to increase the reliability of the measurement of LSK in spondylolisthesis.

Scoliosis Correction Objectives in Adolescent Idiopathic Scoliosis

A recent study revealed large variability among a group of 32 spine surgeons in the preoperative instrumentation strategies for the same 5 adolescent idiopathic scoliosis (AIS) patients. The surgical plans were determined to be surgeon and curve-type dependent. It is hypothesized that this variability may be attributed to different objectives for correction. This study is presented to document and analyze 3-dimensional (3-D) surgical correction goals for AIS as determined by a sample of experienced spine surgeons. Fifty surgeons from the Spinal Deformity Study Group were surveyed and asked to rank 20 parameters of scoliosis correction and to provide weights for correction in the coronal, sagittal, and transverse planes and for mobility (number of unfused vertebrae) according to their importance for an optimal 3-D correction. Responders were also asked to complete a more detailed survey where the correction objectives were assessed for each of the 6 Lenke curve types. Importance and variability of the correction parameters were evaluated using median (M) and interquartile range (IQR) of the rank (1-20). Intraobserver reliability was assessed by means of intraclass correlation coefficients. Twenty-five surgeons completed the first questionnaire. There was overall agreement that sagittal (M, 1; IQR, 1) and coronal (M, 2; IQR, 0.5) balance were the most important parameters for an optimal correction. Apical vertebral rotation was the least important. All other parameters were highly variable. The Cobb angles were moderately important, with ranks between 8 and 11 (IQR, 3-5.75). Lumbar lordosis (M, 6.5; IQR, 6.5) had a better rank and consensus than thoracic kyphosis (M, 13; IQR, 10). Results for individual parameters were in agreement with the weights given for an optimal 3-D correction in the coronal (36%) and sagittal (34%) planes. A subgroup of 10 surgeons completed the second survey. Mobility was more important for Lenke curve types 3 to 6 than for types 1 and 2 (P < 0.032). The coronal plane was more important for curve types 2 and 4 than for the other types (P < 0.032). The intraobserver reliability for determining the different parameters of scoliosis correction was poor to moderate. There is a large variability in scoliosis correction objectives. The variability is both surgeon and curve-type dependent. The variability in instrumentation goals may explain the documented variability of spine instrumentation strategies among surgeons. Aside from achieving sagittal and coronal balance, the goals of surgical correction in AIS remain to be further determined and agreed upon by a consensus of spine deformity surgeons. Level V.

Assessment of Sacral Doming in Lumbosacral Spondylolisthesis

Quantitative versus subjective evaluation of sacral doming in lumbosacral spondylolisthesis. To evaluate the relevance of the Spinal Deformity Study Group (SDSG) index in the assessment of sacral doming and to propose a quantitative criterion to differentiate between significant and nonsignificant doming. There is no consensus on the optimal technique to assess sacral doming, although it is an important feature in spondylolisthesis. Five spinal surgeons subjectively assessed the sacral endplate of 100 subjects (34 high-grade spondylolisthesis, 50 low-grade spondylolisthesis, 16 controls) from lateral radiographs. Subjects were classified by each surgeon as having significant or nonsignificant sacral doming. An independent observer quantitatively evaluated sacral doming for all subjects using the SDSG index. A criterion to differentiate significant from nonsignificant sacral doming was sought, based on the comparison between the subjective assessment of surgeons and the quantitative evaluation by the independent observer. Intrarater and interrater reliability of the SDSG index was evaluated using intraclass correlation coefficient (ICC). Intrarater and interrater ICCs for the SDSG index were excellent at 0.91 and 0.88, respectively. Sacral doming evaluated with the SDSG index was 11.6% +/- 5.0% (range, 1.5%-18.9%), 16.4% +/- 6.3% (range, 3.7%-35.6%), and 27.9% +/- 10.9% (range, 5.7%-56.9%) for controls, low-grade, and high-grade cases, respectively. Overall intersurgeon agreement on the significance of sacral doming was substantial at 88% (kappa = 0.72). With a threshold value of 25% for the SDSG index, 93% of concordance was found between the quantitative evaluation using the SDSG index and the multisurgeons subjective assessment. This study confirms the relevance of the SDSG index to assess sacral doming in lumbosacral spondylolisthesis. The authors propose a criterion of 25% to differentiate significant from nonsignificant sacral doming using the SDSG index. Such a criterion will allow more accurate assessment of sacral remodeling, especially for borderline cases, and facilitate comparisons between studies.

Answer to the comment by Dietrich Schlenzka on ‘‘A proposal for a surgical classification of pediatric lumbosacral spondylolisthesis based on current literature (J.-M. Mac-Thiong, H. Labelle)’’

We wish to thank Dr. Schlenzka for his judicious comments. We completely agree with him that the scientific evidence is currently too sparse to provide definitive recommendations concerning the surgical treatment of pediatric lumbosacral spondylolisthesis. The rationale of our study was in fact directly focused on this specific problem. After a thorough review of the literature and from the recent findings on spino-pelvic balance, we concluded that one of the main impediments to reaching a consensus on the treatment of this disorder was the failure to recognize that the slip grade in only one component of the deformity. As a primary objective of our article, the proposed classification suggests that subjects with spondylolisthesis are a heterogeneous group and that clinicians need to keep this fact in mind for evaluation and treatment. As noted many times in the article, the tentative algorithm presented was not meant to be considered as the final scheme of treatment but rather was provided to illustrate and better support the notion that spondylolisthesis involves a heterogeneous group of subjects and that consequently the treatment should not be the same for all patients. We strongly believe that the development of a comprehensive classification is a prerequisite and a sine qua none for future studies in order to end up with strong recommendation on the treatment of the different types of spondylolisthesis. It is exact that we based our classification on the premise that the complexity of the surgery should increase as the severity of spondylolisthesis increases. Although it seems axiomatic, we agree with the Dr. Schlenzka that it ‘‘is not necessarily true for a chronic condition’’ and that it is still to be proven. However, we believe that it is in fact true (at least when considering the slip grade) since in the current literature, there is sufficient evidence supporting that the ‘‘gold standard’’ in situ fusion for low-grade spondylolisthesis is not appropriate for all patients with severe high-grade spondylolisthesis. There is also some evidence from Molinari et al. that posterior element dysplasia (size of transverse processes) influences the planning of surgical treatment in high-grade spondylolisthesis. While the current tendency is towards more complex surgery for high-grade slips—most authors now recommend partial reduction with circumferential fusion and some form of pelvic stabilization—we wanted to underline that a complex surgery may not be necessary for all patients. In the meantime, the Spinal Deformity Study Group (SDSG) is currently enrolling a prospective multi-center cohort of patients surgically treated for spondylolisthesis and we hope that this large database will allow to verify the relevance of the proposed classification in predicting the outcome with respect to all types of surgery. Concerning the criteria to differentiate between low- and high-dysplastic slips, we totally agree with Dr. Schlenzka that there is currently insufficient data to adequately characterize dysplasia. This is an important question that definitely needs to be addressed. This is why the SDSG is now conducting studies to establish standards to quantify dysplasia in spondylolisthesis. For example, a recent study by the SDSG has shown that significant sacral doming, as assessed by a group of spinal surgeons, occurs when the dome height measures more than 25% of the length of the upper sacral endplate. As pointed out by Dr. Schlenzka and already cited in the article, patient's age is an important criterion that needs to be taken into consideration for surgical planning. However, an age-based criterion was too difficult to incorporate into the classification due to the lack of data in the literature. This is why we mentioned in the article that age should be considered on an individual basis. It is also true that radiation exposure is an important aspect that needs to be considered. As surgeons usually follow up spondylolisthesis using lumbosacral films, we believe that standing long films are necessary in the preoperative work-up. The addition of a single long film preoperatively is not related with undue radiation, considering also that patients often have scoliosis and that assessing spinal balance is important. Regarding CT scans, we agree that they are not mandatory (as already mentioned in the text), especially if an MRI is available. In addition, in our current practice, we have found that plain films are sufficient to classify spondylolisthesis with an acceptable intra- and inter-rater reliability. Finally, as mentioned many times in the article, the algorithm presented was only a proposal meant to illustrate the foreseen clinical use of the classification. Further research is required before reaching our ultimate goal of proposing a definitive surgical algorithm for lumbosacral spondylolisthesis. Although this is only the beginning of a long road, we believe the proposed classification can serve as the starting point for future studies that will provide evidence-based data concerning the progression and treatment of lumbosacral spondylolisthesis.