Thoracic Sagittal Alignment Research Articles

Spinal shrinkage, sagittal alignment and back discomfort changes in manufacturing company workers during a working day

Prolonged standing and lifting heavy loads are risk factors for the appearance of low back pain in work. The aim of this study was to observe changes in the height, spinal sagittal alignment, and the lumbar and dorsal discomfort perception in assembly line workers. Cross-sectional study, 40 assembly line workers (6 females). Height, sitting height, grades of thoracic kyphosis and lumbar lordosis and perceived spine discomfort, before and after the working day, were determined. Thoracic and lumbar sagittal alignment was compared between discomfort developers and no developers. There was a significant decrease in the height and sitting height of the workers at the end of the day. Thoracic and lumbar curvature increased significantly, as did the perceived lumbar discomfort. Workers on the assembly line, in a prolonged standing work, suffer an increase in lumbar discomfort, and changes in height and thoracic and lumbar curvatures. Practitioner summary: Spinal shrinkage, sagittal alignment and back discomfort (upper and lower back), were analysed in assembly line workers in prolonged standing during a workday. Assembly line workers suffer a decrease in height, an increase in their thoracic and lumbar curvature, and in lumbar discomfort throughout their workday.

Effect of cervical flexion and extension on thoracic sagittal alignment.

The cervical spine has the largest sagittal motion in the whole spine, and cervical alignment affects the thoracic sagittal alignment. However, the effects of cervical flexion and extension on thoracic sagittal alignment have not been investigated in detail. The purpose of this study was to analyze the change of thoracic sagittal alignment following cervical flexion and extension. A total of 55 consecutive patients (42 men and 13 women; average age 49.1 years) who presented to our department with spinal degenerative disease between January 2016 and September 2017 were enrolled in our study. Subjects with a history of trauma, infection, tumor, inflammatory disease, ossification, or cervical deformities, and those who had undergone spinal surgery were excluded. The following parameters were analyzed: occipito-axial angle (O-C2), C2 slope (C2S), C2-C7 angle, T1 slope (T1S), thoracic kyphosis, T1-T4 angle, T5-T8 angle, T9-T12 angle, lumbar lordosis, sacral slope, pelvic tilt in cervical flexion, neutral, and extension. Cervical flexion significantly decreased O-C2, C2-C7 angles and T1S, and increased C2S. Cervical extension conversely changed these parameters. At cervical flexion, the correlation of C2-C7 angle with thoracic parameters was maintained, except for the T1-T4 angle. At cervical extension, the correlation was observed with T1S and T1-T4 angle. Cervical flexion affects the T1S and T5-T8 angle, but there is no significant change in T1-T4 and T9 and lower spino-pelvic columns. This study suggests that T2-T4 can be considered as a stable distal end when cervical long fixation for corrective surgery is performed.

Correlation of cervical and thoracic inlet sagittal parameters by MRI and radiography in patients with cervical spondylosis.

To investigate the relationship between cervical and thoracic sagittal alignment parameters measured by magnetic resonance imaging (MRI) and x-ray in patients with cervical spondylosisData from 120 symptomatic patients who presented with cervical spondylosis between April 2015 and January 2016 were retrospectively analyzed. Patients received both a cervical MRI and a cervical radiograph during a single visit. The thoracic inlet angle (TIA), T1 slope (T1S), neck tilt (NT), C2-C7 angle (C2-C7), and C2-C7 sagittal vertical axis (C2–7 SVA) were assessed. Pearson correlation coefficient, paired t test, and linear regression models were used to analyze parameters obtained by cervical MRI and radiography.The difference in mean thoracic inlet angle x-ray (TIAX) and thoracic inlet angle MRI (TIAM) (TIAM–TIAX) (0.72 ± 5.82°) was not significant (P > .05). There were significant differences in mean T1 slope x-ray (T1SX) and T1 slope MRI (T1SM) (T1SM-T1SX) (-2.55 ± 6.14°), mean neck tilt x-ray (NTX) and neck tilt MRI (NTM) (NTM-NTX) (3.26 ± 6.01°), mean C2-C7 angle x-ray (C2–7X) and C2-C7 angle MRI (C2–7 M) (C2–7M-C2–7X) (−3.57 ± 10.00°), and mean C2-C7 sagittal vertical axis X ray (C2–7 SVAX) and C2-C7 sagittal vertical axis MRI (C2–7 SVAM) (C2–7 SVAM-C2–7 SVAX) (-4.50 ± 1.26 mm) (all P ≤ .001). There were positive correlations between TIAM and TIAX (r = 0.807), T1SM and T1SX (r = 0.581), NTM and NTX (r = 0.759), cervical loidosis MRI and cervical loidosis x-ray (r = 0.666), and SVAM and SVAX (r = 0.226).MRI may be useful to evaluate thoracic inlet and sagittal alignment parameters in patients with cervical spondylosis. Patients with cervical spondylosis may have a relatively low capacity for compensation in the cervical region.

How to Optimize Axial Correction Without Altering Thoracic Sagittal Alignment in Hybrid Constructs With Sublaminar Bands: Description of the “Frame” Technique

Study DesignRetrospective monocentric database study. ObjectivesTo describe the “frame” reduction technique and report the 3D quantitative analysis of postoperative corrections in a consecutive series of thoracic adolescent idiopathic scoliosis (AIS) patients. Summary of Background DataPosteromedial translation technique using sublaminar bands have been proved to be efficient and safe for 3D correction of the deformity and overall cosmetic aspect of the trunk. However, the ability to correct the axial plane may tend to rotate the vertebra clockwise instead of counterclockwise, thus increasing apical vertebra axial rotation (AVR) and the rib hump. A technical improvement was developed to emphasize axial correction. Methods60 thoracic AIS patients consecutively operated by posteromedial translation using the “frame” reduction technique were included with a minimum 2-year follow-up. Precontoured rods were connected with fixed transverse connectors according to a personalized preoperative planning. Rods were first inserted distally in the pedicle screws to achieve lumbar correction, and then in the upper anchors, and finally sublaminar bands were connected to their corresponding rods to progressively bring the concave lamina to the concave rod to correct the thoracic deformity. Sagittal and coronal 3D measures were performed preoperatively and at the latest follow-up using SterEOS (EOS Imaging, Paris, France) to assess the efficiency of the technique. ResultsThe distance from the center of the apical vertebra to the reference axis in the frontal plane was reduced from 4.7 to 1.1 cm, traducing the efficient medial translation of the spine during correction. T1–T12 kyphosis significantly increased after surgery (28°–35°). 3D location of the upper instrumented vertebra (UIV) was not affected. The apical rotation was significantly reduced after surgery (19°–11°), and the AVR correction rate averaged 42.2%. ConclusionThe “frame” technique is an innovative way of using polyester bands, optimizing axial correction while respecting sagittal alignment. Level of EvidenceLevel IV.

Magnitude, Location, and Factors Related to Regional and Global Sagittal Alignment Change in Long Adult Deformity Constructs: Report of 183 Patients With 2-Year Follow-up.

This is a retrospective review of a prospective multicenter adult spinal deformity (ASD) database. To quantify the location and magnitude of sagittal alignment changes within instrumented and noninstrumented spinal segments and to investigate the factors associated with these changes after surgery for ASD. Spinal realignment is one of the major goals in ASD surgery and changes in the alignment are common following surgical correction. Inclusion criteria: operative patients with age above 18, coronal Cobb angle ≥20 degrees, sagittal vertical axis (SVA) ≥5 cm, pelvic tilt ≥25 degrees, and/or thoracic kyphosis ≥60 degrees. revision surgery 6 weeks postoperatively. Standard sagittal radiographic spinal deformity parameters were evaluated. Changes in sagittal parameters between 6 weeks and 2 years postoperatively were assessed within and outside instrumented segments. Associations between changes in sagittal alignment and age, preoperative SVA, rod diameters, rod material, presence of 3-column osteotomy, and the use of interbody fusions were evaluated. Patients were also stratified by >5- and >10-degree changes in alignment. In total, 183 patients (male:29, female:154, average age: 56±14.8 y) met inclusion criteria. A total of 45(24.6%) patients had increase in pelvic tilt >5 degrees, 74(40.4%) had increase in pelvic incidence and lumbar lordosis (LL) >5 degrees, and 76 (41.5%) had increase in SVA >2 cm. Mean change of thoracic sagittal alignment was +8 degrees; 70 (60%) patients had increases of >5 degrees and 31 (27%) had increases of >10 degrees. Noninstrumented thoracic segments had significantly more increase than instrumented thoracic segments (P=0.02). Mean loss of LL was -6 degrees; 49(47%) patients had worsening >5 degrees and 13(13%) >10 degrees. Noninstrumented lumbar segments had significantly less loss of lordosis than instrumented segments (P<0.01). Risks for loss of LL were: age 65 years and above [odds ratio (OR) 9.4; 95% confidence interval (CI), 3.5-25.2; P<0.01], preoperative SVA>5 cm (OR, 2.4; 95% CI, 1.3-4.4; P<0.01), and lumbar interbody fusion (OR, 2.3; 95% CI, 1.2-4.2; P<0.01). Smaller rods (4.5 mm) were associated with a lower probability of worsening LL compared with 5.5-mm rods (OR, 0.15; 95% CI, 0.04-0.58; P<0.01) and 6.0-mm rods (OR, 0.36; 95% CI, 0.18-0.72; P<0.01). The presence of a 3-column osteotomy and rod material were not significant factors in alignment changes (P>0.05). After correction of ASD, increases in thoracic and decreases in lumbar alignment is common. Loss of thoracic sagittal alignment primarily occurs in noninstrumented thoracic segments, whereas instrumented lumbar levels in elderly patients ( above 65 y) with high preoperative SVA, interbody fusions, and larger rods have significantly higher rates of postoperative sagittal alignment changes in the lumbar spine.

Correction of hypokyphosis in thoracic adolescent idiopathic scoliosis using sublaminar bands: a 3D multicenter study.

The comparison of implants and correction methods remain controversial in AIS. Excellent frontal and axial correction rates have been reported with all-screw constructs, but at the expense of sagittal alignment, which has a tendency to flatten postoperatively. Posteromedial translation using hybrid constructs seems to preserve and improve thoracic kyphosis (TK), but no series exist to date with a significant number of hypokyphotic patients. In addition, the measures of TK in 2D are often wrong in severe AIS due to axial rotation. The goals of this study were therefore to analyze the 3D radiological outcomes of a group of hypokyphotic AIS patients operated with sublaminar bands. 35 consecutive AIS hypokyphotic patients (T4T12 <15°) operated in three centers were included, with a minimum 2-year follow-up. The surgical technique was similar in all centers, associating lumbar pedicle screws and thoracic sublaminar bands. Posteromedial translation was the main correction technique, and no patient underwent prior anterior release. 3D spinal reconstructions were performed preoperatively, postoperatively and at the latest follow-up by an independent observer using SterEOS (EOS imaging, Paris, France), and 2D and 3D measurements were compared. In addition, a new 3D parameter [sagittal shift of the apical vertebra (SSAV)], reflecting the translation of the apical vertebra of the main curve in the patient sagittal plane, was described and reported. The age of the cohort was 16years and the number of sublaminar bands used for correction averaged 6 (±1.5). T1T12 and T4T12 sagittal Cobb angles appeared to be overestimated on 2D postoperatively (3°, p=0.002 and 4°, p<0.001, respectively). Hence, only 3D measurements were kept for the quantitative analysis of the postoperative correction. T4T12 TK significantly increased after surgery (average 8°±7°, p<0.001), but 11 patients (31.4%) remained hypokyphotic. Seven out of the eight patients (87.5%) who presented a thoracic lordosis (i.e., T4T12 <0°) preoperatively were corrected after surgery (mean gain 16°±4°). A posterior shift (positive SSAV) of the apical vertebra was reported in 24 patients (68.6%). In this subgroup, the mean SSAV was +2cm (±1). Good correlation was found between the SSAV and the postoperative change in 3D T4T12 kyphosis (r=0.62). Measures in 2D tend to overestimate sagittal alignment and are not sufficient to evaluate postoperative correction. SSAV is a new 3D parameter reflecting the TK change that needs to be further investigated and used in the future. This series confirms that sublaminar bands should be considered in hypokyphotic patients, since thoracic sagittal alignment was restored in 68.6% of the cases.

Cervical Sagittal Alignment Limited Adjustment After Selective Posterior Thoracolumbar/Lumbar Curve Correction in Patients With Lenke Type 5C Adolescent Idiopathic Scoliosis.

A retrospective clinical and radiographic study. The aim of this study was to analyze the radiographic change in cervical sagittal alignment (CSA) and identify the possible factors influencing the postoperative CSA in selective posterior thoracolumbar/lumbar (TL/L) curve correction. The correlation between the CSA and thoracic sagittal alignment (TSA) is a well-recognized phenomenon in patients with thoracic idiopathic scoliosis. However, little has been published about the influence of TL/L curve instrumentation on CSA. Thirty patients with Lenke type 5C adolescent idiopathic scoliosis (AIS) received the selective posterior TL/L curves fusion by pedicle screws. Preoperative and postoperative radiographic and clinical parameters were analyzed. C2-C7 lordosis less than 0 was considered a lordotic cervical spine (LCS), whereas more than 0 was considered a kyphotic cervical spine (KCS). Preoperatively, 43% of patients showed a KCS, whereas the remaining 57% showed a LCS. C2-C7 lordosis was correlated with T1-slope, thoracic kyphosis (TK), and global-TK (Gl-TK) (P < 0.05). The patients in the KCS group showed a smaller T1-slope, TK, and Gl-TK than those in the LCS group. Logistic regression analysis revealed that the T1-slope [odds ratio (OR) = 0.86, P = 0.008] and Gl-TK (OR = 0.90, P = 0.019) were risk factors for developing KCS. In the LCS group, 5 of 12 patients with LCS exhibited KCS after surgery. The T1-slope and Gl-TK in the changed group were considerably smaller than those in the maintained group (P = 0.004 and 0.035, respectively). In the KCS group, 6 of 13 patients with KCS unrecovered to LCS after the operation. The T1-slope in the unrecovered group was smaller than that in the recovered group (P = 0.045). C2-C7 lordosis was strongly correlated with the T1-slope. C2-C7 lordosis of Lenke 5C AIS was related to the global TSA rather than TK and proximal TK. As time progresses, spontaneous adjustment of CSA is limited because of the inherent rigidity of the cervical spine. 4.

MRI May Serve as a Valid Alternative to Standing Radiography in Evaluating the Sagittal Alignment of the Upper Thoracic Spine

This study is of a retrospective radiographic design. The objective of the study was to compare supine magnetic resonance images (MRI) with standing x-ray scanning in the evaluation of the sagittal alignment of the upper thoracic spine. X-ray films have been reported to be inaccurate in evaluating the proximal thoracic sagittal alignment because of poor visibility of the upper thoracic region. Previous studies have demonstrated the feasibility of supine MRI in evaluating spinal deformities in the coronal plane. However, no study has addressed the use of MRI for evaluating the sagittal alignment of the upper thoracic region. Ninety-six adolescents with idiopathic thoracolumbar/lumbar scoliosis were enrolled. The visibility of the upper thoracic spine landmarks from C7 to T6 in the lateral standing x-ray films was first graded. For patients with moderate or good clarity of the landmarks of each vertebra from C7 to T6 on x-ray films, the vertebral sagittal angles from T1 to T5 and the angle of T2-T5 kyphosis were measured by 3 observers on standing x-ray films and supine MRI images, respectively. Intraclass correlation coefficients were used to determine the intraobserver, interobserver, and method reliability. The paired t test was performed to compare the measurements between the 2 methods. The visibility of the upper thoracic region in x-ray films was generally unsatisfactory, especially for T1 and T2, whereas all the vertebrae were clear in MRI images. Only 50 patients' x-ray films were graded as moderate or good visibility in the upper thoracic spine. Measurements on MRI images gave excellent intraobserver and interobserver reliability (0.914-0.924 and 0.838-0.920, respectively), which were better than that on x-ray films (0.767-0.891 and 0.713-0.883, respectively). No significant difference was found between the 2 modalities in terms of sagittal angles of T3, T4, and T5 (P=0.680, 0.595, and 0.239, respectively) and T2-T5 kyphosis (P=0.105). With excellent measurement reproducibility, a supine MRI image may serve as a valid alternative to a standing x-ray film for the measurement for T3, T4, and T5 sagittal angles and for the evaluation of upper thoracic kyphosis.

Cervical sagittal alignment variations in adolescent idiopathic scoliosis patients treated with thoraco-lumbo-sacral orthosis

Thoraco-lumbo-sacral orthosis (TLSO) is an effective treatment in adolescent idiopathic scoliosis (AIS) patients, but cervical sagittal alignment (CSA) variations after bracing have never been evaluated. The purpose of this study was to assess changes in CSA before, during and after TLSO treatment, and to determine whether patients developed cervical pain. This was a retrospective study in 38 AIS patients (33 females; mean age 10.8years) treated by TLSO. Patients were Risser 0 (n=34) or 1 (n=4). Major curve deformity (MC) in the coronal plane and cervical (CSA), thoracic (TSA) and lumbar (LSA) sagittal alignment were evaluated radiographically at start of treatment (t 0), after 1month of brace treatment (t 1), and 1year after end of treatment (t 2). Cervical pain was evaluated at t 2 using a visual analogue scale (VAS). The TLSO was worn for an average of 4.6years. Mean CSA, TSA and LSA were significantly lower at t 2 than at t 0: 0±2.5° vs. 9.4±2.3°, 24.1±2.6° vs. 29.3±2.4° and 5±1.9° vs. 44.2±2.5°, respectively (p<0.05). CSA and TSA showed moderate-good correlation (r=0.57). CSA was normolordotic in 1/38 patients at t 2 compared to 18/38 at t 0 (p<0.05). MC did not progress during treatment (p>0.8). VAS score was 0 in all patients. The TLSO can control progression of the deformity in the frontal plane, but it influences CSA, TSA and LSA. In particular, it decreases cervical spine lordosis, with reduction maintained 1year after the end of treatment. Numerical differences, although statistically significant, were not clinically relevant.

The Thoracic Lordosis Correction Improves Sacral Slope and Walking Ability in Neuromuscular Scoliosis.

Retrospective study. To report on neuromuscular patients with preserved walking ability, but forward bending of the body due to thoracic lordosis, and to suggest thoracic lordosis correction as the surgical treatment. It is an established fact that lumbar lordosis or pelvic parameter is directly related to thoracic sagittal balance. However, the reverse relationship has not been fully defined yet. Loss of thoracic kyphosis results in positive sagittal balance, which causes walking difficulty. Neuromuscular patients with thoracic lordosis have not been reported yet, and there have been no reports on their surgical treatments. This study analyzed 8 patients treated with thoracic lordosis correction surgery. Every patient was diagnosed with muscular dystrophy. In thoracic lordosis correction surgery, anterior release was performed in the first stage and posterior segmental instrumentation was performed in the second stage. Radiographic parameters were compared and walking ability was evaluated with gait analysis. All patients were classified according to the modified Rancho Los Amigos Hospital system preoperatively and 2 years postoperatively to evaluate functional ability. The average follow-up period was 2.9 years. Before surgery, the mean thoracic sagittal alignment was -2.1-degree lordosis, the mean Cobb angle and sacral slope increased to 36.3 and 56.6 degrees, respectively. The anterior pelvic tilt in gait analysis was 29.3 degrees. At last follow-up after surgery, the mean thoracic sagittal alignment changed to 12.6-degree kyphosis, and the Cobb angle and sacral slope decreased to 18.9 and 39.5 degrees, respectively. Lumbar lordosis and the sacral slope showed significant positive correlation (P<0.001). The improvement in thoracic lordosis showed a significant correlation to the preoperative flexibility of the major curve (P=0.028). The anterior pelvic tilt in gait analysis improved to 15.4 degrees. The functional ability improved in 2 (50%) of 4 patients in class 2 and maintained in remaining 6 patients 2 years after surgery. Thoracic lordosis correction surgery in neuromuscular scoliosis patients with thoracic lordosis improved the sacral slope in the standing position and the anterior pelvic tilt in gait. Sagittal imbalance was compensated by the spinopelvic mechanism, and back and hip extensor muscles seem to play a major role in this compensation.

Relationship among cervical, thoracic, and lumbopelvic sagittal alignment in healthy adults.

To evaluate the association between cervical sagittal alignment and thoracic/lumbopelvic sagittal alignment in healthy Japanese adults. 30 male and 22 female healthy adults aged 22 to 50 years were recruited. Spinal parameters were measured on radiographs, including the cervical sagittal vertical axis, sagittal vertical axis, C7 tilt angle, Ishihara index for cervical lordosis, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. The C7 tilt angle positively correlated with the Ishihara index (r=0.52, p<0.0001) and thoracic kyphosis (r=0.53, p<0.0001). The Ishihara index positively correlated with thoracic kyphosis (r=0.34, p=0.01) and C7 tilt angle (r=0.52, p<0.0001). Pelvic incidence positively correlated with sacral slope (r=0.45, p=0.001), lumbar lordosis (r=0.26, p=0.07), and pelvic tilt (r=0.29, p=0.03). Compared with men, women had a smaller Ishihara index (0.07 vs. 0.001, p=0.03), thoracic kyphosis (30.5º vs 24.1º, p=0.02), and C7 tilt angle (23.1º vs. 16.8º, p=0.02). Women had less cervical lordosis and thoracic kyphosis, that is, a straighter cervico-thoracic sagittal alignment. In healthy Japanese adults, cervical sagittal alignment is associated with thoracic sagittal alignment but not with lumbopelvic alignment.

Cervical Spine Compensation in Adolescent Idiopathic Scoliosis

Study Design/SettingCross-sectional. ObjectivesTo determine associations between cervical spine alignment and Lenke type for adolescent idiopathic scoliosis (AIS). Summary of Background DataAlthough the lumbosacral spine and pelvis are standard considerations for evaluation of AIS, few studies have examined cervical spine alignment. These studies did not consider Lenke types upon which treatment decisions are based. MethodsStratified random sampling from 3,654 full-length preoperative lateral films of patients in a multicenter database of surgically treated AIS was done to obtain a representative sample from all Lenke types and thoracic curve modifiers. The C2–C7 sagittal Cobb and C2–C7 sagittal vertical axis (SVA) distances were measured by reviewers unaware of the patient's Lenke classification. C2–C7 sagittal Cobb and C2-C7 SVA among curve types and thoracic modifiers was compared using analysis of variance. ResultsThere were 387 females and 84 males among patients in 471 randomly selected films; mean age at surgery was 14.8 ± 2.0 years. Significantly less cervical kyphosis was seen in Lenke 3 or 4 curves and greater cervical kyphosis in Lenke 1, 2, 5, and 6 curves. No significant differences in C2–C7 SVA were seen. ConclusionsPatients with AIS appear to compensate for abnormal thoracic sagittal alignment with changes in cervical sagittal alignment. This seems intuitive for Lenke 1 and 2 curves in which surgical restoration of thoracic kyphosis is a recognized goal and has been shown to improve cervical alignment. Cervical kyphosis was also noted in Lenke 5 and 6 curves, which suggests a need to consider compensatory thoracic and cervical sagittal alignment during surgical planning. Patients with Lenke 3 and 4 curves had more normal cervical alignment, which suggests that with the major portion of the curve located in the middle of the spine, there is more ability above and below to maintain a more normal sagittal alignment.

Variation of the Position of the Aorta Relative to a Kyphotic Thoracic Spine

An analysis of computed tomography images of the spine in adult Japanese patients. To evaluate the variation of the position of the aorta relative to a spine with a thoracic kyphotic angle and to verify the safety margin for transpedicular screw fixation. Recent studies have suggested that the aorta is positioned more laterally and posteriorly in patients with idiopathic scoliosis than in normal patients; however, variation of the position of the aorta in thoracic sagittal alignment has not been performed. T4-T12 vertebrae were studied using computer tomography images in 58 Japanese patients (aged 31-90 years) with normal coronal alignment of the spine. Pedicle diameter, pedicle length, chord length, closest distance from the aorta, and pedicle-aorta angle (PAA) were evaluated using a Mann-Whitney U test and Spearman rank correlation analysis. Pedicle diameter showed an increase in size from T4 (4.7 mm) to T12 (8.2 mm), pedicle length had an almost constant size of about 20 mm, and chord length increased from T4 (37.7 mm) to T12 (47.2 mm). Closest distance from the aorta decreased from T4 (29.6 mm) to T6 (24.6 mm) and then increased to T12 (49.3 mm). PAA increased from T4 (31.5°) to T6 (38.6°) and then decreased to T12 (5.0°). Sagittal curvature showed a correlation with PAA, with an increasing sagittal thoracic Cobb angle related to decreases in PAA at the T5 (r = -0.31, P = 0.034), T6 (r = -0.37, P = 0.008), and T7 (r = -0.29, P = 0.036) levels. The descending aorta is positioned more medially at the T5, T6, and T7 levels in patients with a kyphotic spine. These spatial relationships should be considered when planning pedicle screw insertion for a kyphotic spine.

Cervical sagittal plane decompensation after surgery for adolescent idiopathic scoliosis: an effect imparted by postoperative thoracic hypokyphosis

Several studies have characterized the relationship among postoperative thoracic, lumbar, and pelvic alignment in the sagittal plane. However, little is known of the relationship between postoperative thoracic kyphosis and sagittal cervical alignment in patients with adolescent idiopathic scoliosis (AIS) treated with all pedicle screw constructs. The authors examined this relationship and associated factors. A prospective database of pediatric patients with AIS undergoing spinal fusion between 2003 and 2005 was reviewed for those who received predominantly pedicle screw constructs for Lenke Type 1 or Type 2 curves. Parameters analyzed on pre- and postoperative radiographs were the fusion levels; cervical, thoracic, and lumbar sagittal balance; and C-2 and C-7 plumb lines. Preoperatively, 6 (Group A) of the 22 patients included in the study had frank cervical kyphosis (mean angle 13.0°) with mean associated thoracic kyphosis of 27.2° (range 16°-37°). Postoperatively, cervical kyphosis (13.0°) remained in the patients in Group A along with mean thoracic kyphosis of 17.7° (range 4°-26°, p < 0.05). Preoperatively, the remaining 16 of 22 patients had neutral to lordotic cervical alignment (mean -13.8°) with thoracic kyphosis (mean 45°, range 30°-76°). Postoperatively, 8 (Group B) of these 16 patients demonstrated cervical sagittal decompensation (> 5° kyphosis), with 6 showing frank cervical kyphosis (10.5°, p < 0.05). In Group B, the mean postoperative thoracic kyphosis was 25.6° (range 7°-49°, p < 0.05). The other 8 patients (Group C) had mean postoperative thoracic kyphosis of 44.1° (range 32°-65°), and there was no cervical decompensation (p < 0.05). The sagittal profile of the thoracic spine is related to that of the cervical spine. The surgical treatment of Lenke Type 1 and 2 curves by using all pedicle screw constructs has a significant hypokyphotic effect on thoracic sagittal plane alignment (19 [86%] of 22 patients). If postoperative thoracic kyphosis is excessively decreased (mean 25.6°, p < 0.05), the cervical spine may decompensate into significant kyphosis.

Cervical spine sagittal alignment variations following posterior spinal fusion and instrumentation for adolescent idiopathic scoliosis

The aim of this study is to quantify the changes in the sagittal alignment of the cervical spine in patients with adolescent idiopathic scoliosis following posterior spinal fusion. Patients eligible for study inclusion included those with a diagnosis of mainly thoracic adolescent idiopathic scoliosis treated by means of posterior multisegmented hook and screw instrumentation. Pre and post-operative anterior-posterior and lateral radiographs of the entire spine were reviewed to assess the changes of cervical sagittal alignment. Thirty-two patients (3 boys, 29 girls) met the inclusion criteria for the study. The average pre-operative cervical sagittal alignment (CSA) was 4.0° ± 12.3° (range -30° to 40°) of lordosis. Postoperatively, the average CSA was 1.7° ± 11.4° (range -24° to 30°). After surgery, it was less than 20° in 27 patients (84.4%) and between 20° and 40° in 5 patients (15.6%). The results of the present study suggest that even if rod precontouring is performed and postoperative thoracic sagittal alignment is restored, improved or remains unchanged after significant correction of the deformity on the frontal plane, the inherent rigidity of the cervical spine limits changes in the CSA as the cervical spine becomes rigid over time.

Coupling Between Sagittal and Frontal Plane Deformity Correction in Idiopathic Thoracic Scoliosis and Its Relationship With Postoperative Sagittal Alignment

Prospective clinical-radiographic study. To investigate the natural coupling behavior between frontal deformity correction and the simultaneous changes in thoracic kyphosis, and to examine how the postoperative thoracic sagittal realignment relates to this natural coupling behavior. Restoration of the sagittal alignment is one of the fundamental goals in scoliosis correction surgery. It is generally achieved by rod precontouring intraoperatively. However, clinical studies suggested that postoperative sagittal realignment seems to be more affected by the inherent properties of the spine rather than the instrumentation or the surgical maneuver. Ninety-eight idiopathic scoliosis patients with thoracic curves treated with one-stage posterior spinal fusion, using corrective segmental spinal instrumentation (hook-rod or pedicle screw-rod constructs) were investigated. Pre- and postoperative frontal and sagittal alignments were measured by standing anteroposterior and lateral radiographs. Preoperative frontal plane flexibility was assessed by the fulcrum bending radiograph in the standard manner, an additional radiograph was taken in the lateral plane, to assess how this frontal correction force affects sagittal plane alignment (lateral fulcrum bending radiograph). When thoracic frontal deformity was corrected under fulcrum bending, coupled changes in the thoracic kyphosis demonstrated 3 different patterns: thoracic kyphosis increased in 25 patients with a mean kyphosis of 9 degrees to 19 degrees, decreased in 45 with a mean of 34 degrees to 21 degrees and remained unchanged (within 3 degrees ) in 28 with a mean of 19 degrees to 18 degrees. After surgery, the direction of correction of thoracic kyphosis significantly correlated with the coupling patterns demonstrated on fulcrum bending radiographs (r = 0.579, P < 0.001). However, the actual postoperative thoracic kyphosis angle cannot be predicted by the preoperative lateral fulcrum bending radiograph. There was no statistically significant difference (P = 0.263) between using pedicle screws and hooks in achieving the additional correction beyond what was demonstrated on the lateral fulcrum bending radiographs. Changes in thoracic kyphosis on fulcrum bending due to natural coupling of deformities are directed towards "self-normalization." There is no difference in the sagittal plane deformity correction with the use of hook-rod system or pedicle screw-rod constructs. This can be used as a guideline for exact preoperative rod contouring to reduce the stress on the bone-implant interface and the rate of postoperative failures. The findings also suggest that it is not how big or strong the implants are, but rather the natural curve behavior will at least partially determine the final sagittal outcome.

Three-Dimensional Analysis of Thoracic Apical Sagittal Alignment in Adolescent Idiopathic Scoliosis

Retrospective review of a series of adolescent idiopathic scoliosis patients. To perform a 3-dimensional (3D) analysis of patients with thoracic scoliosis to identify differences in the thoracic sagittal alignment measured from the standard lateral projection as compared to the "true lateral" view. It has been difficult to clinically obtain radiographs in the planes of maximum spinal deformity. Recently, 3D models of the spine have been developed using biplanar radiographic reconstructions that allow a more accurate assessment of spinal alignment. Three-dimensional spinal reconstructions using biplanar radiographs were used to evaluate the apical thoracic sagittal profile. A measurement of sagittal curvature from 2 vertebral levels above and below the thoracic apex (5 vertebrae) was recorded from the standard lateral view. The 3D reconstructions were then rotated to achieve a "true lateral" view of the apical thoracic vertebra and the sagittal apical curvature was remeasured. The difference in the 2 measures of sagittal thoracic apical alignment was compared using repeated measures ANOVA, and then correlated to the coronal thoracic Cobb magnitude using a Pearson correlation analysis (P < 0.05). Sixty-six adolescent idiopathic scoliosis patients with right thoracic scoliosis (Cobb averaged 47 degrees +/- 10 degrees ) were evaluated. The apical thoracic sagittal curvature in the standard lateral view averaged 11 degrees +/- 10 degrees of kyphosis (range: -8 degrees to 38 degrees ). This was statistically greater (P < 0.001) than the apical sagittal curvature in the "true lateral" view that averaged 1 degrees +/- 9 degrees (range:-23 degrees to 22 degrees ). The standard lateral view was rotated an average of 13 degrees +/- 4 degrees to achieve the ideal lateral view of the thoracic apex. This 3D analysis of thoracic scoliosis demonstrated a consistent loss of kyphosis within the 5 thoracic apical vertebrae. The true apical sagittal profile was found to be overestimated by an average of 10 degrees as compared to the perceived alignment from standard lateral radiographs.

Spinal mobility and posture in 8‐ to 16‐year‐old children

Spinal mobility and posture were measured in 294 8-16-year-old boys and girls, divided into five age groups. The upper thoracic sagittal alignment was more vertical among girls, but the postural curves showed no significant age-related differences for either sex. Among both boys and girls thoracic extension, lateral flexion, and rotation decreased significantly between the ages of 12 and 13, but with the exception of extension they returned to the previous level by age 16. Girls were significantly different from boys at 13 years of age. In the thoracic spine, girls had less kyphosis, and were stiffer in forward and lateral flexion, with more rotation to the right than to the left. In the lumbar spine, lateral flexion increased after the age of 10 in both sexes. Between the ages of 8 and 14 lumbar lateral flexion was significantly greater among girls than among boys, whereas extension and rotation was greater only at the ages of 8 and 10 years. With increasing age, a shift from left to right dominance in lumbar lateral flexion was found in girls only.