Main Thoracic Adolescent Idiopathic Scoliosis Research Articles

Pedicle morphometry analysis of main thoracic apex adolescent idiopathic scoliosis

IntroductionScrew insertion during scoliosis surgery uses free-hand pedicle screw insertion methods. However, there is a wide variation in pedicle shapes, sizes, and morphometry, especially in scoliosis patients. CT scan pedicle measurements in main thoracic Lenke type 1 adolescent idiopathic scoliosis can help visualize this diversity. This study aimed to highlight the features of pedicle morphometry on the concave and convex sides, including pedicle diameter (width in axial and height in the sagittal plane), the depth to the anterior cortex, and Watanabe Pedicle classification in patients with main thoracic apex adolescent idiopathic scoliosis.Materials and methodsThis study was a cross-sectional observational study of Adolescent Idiopathic Scoliosis (AIS) patients whose apex in the main thoracic patient underwent deformity correction procedures. We used a three-dimensional CT scan to evaluate pedicle morphometry on the apex vertebrae, three consecutive vertebrae above and below the apex.ResultsA total of 6 patients with apex main thoracic AIS with 84 pedicles consisting of 42 pedicles from each concave and convex curve were analyzed. All of the samples were female, with the mean age at the procedure being 21.2 ± 5.56. The mean cobb angle was 62° ± 23°, with the main apex between VT8-VT10. The size of the pedicle was bigger from upper to lower vertebrae. The mean pedicle depth, pedicle width, and pedicle height for the concave side were 36.06 ± 4.31 mm, 3.91 ± 0.66 mm, and 9.16 ± 1.52 mm, respectively. Meanwhile, the convex side is 37.52 ± 1.84 mm, 5.20 ± 0.55 mm, and 11.05 ± 0.70 mm, respectively. We found a significant difference between the concave and convex sides for the pedicle width and height. The concave and convex sides were mainly classified as type C (38%) and type A (50%) Watanabe pedicle.ConclusionPedicle width and pedicle height are significantly different between the concave and the convex side with convex side has better Watanabe pedicle classification. Pre-operative CT evaluation is essential for planning proper pedicle screw placement in AIS patients.

In vivo deformation of anatomically pre-bent rods in thoracic adolescent idiopathic scoliosis

Some surgical strategies can maintain or restore thoracic kyphosis (TK); however, next-generation surgical schemes for adolescent idiopathic scoliosis (AIS) should consider anatomical corrections. A four-dimensional correction could be actively achieved by curving the rod. Thus, anatomically designed rods have been developed as notch-free, pre-bent rods for easier anatomical reconstruction. This study aimed to compare the initial curve corrections obtained using notch-free rods and manually bent, notched rods for the anatomical reconstruction of thoracic AIS. Two consecutive series of 60 patients who underwent anatomical posterior correction for main thoracic AIS curves were prospectively followed up. After multilevel facetectomy, except for the lowest instrumented segment, either notch-free or notched rods were used. Patient demographic data, radiographic measurements, and sagittal rod angles were analyzed within 1 week after surgery. Patients with notch-free rods had significantly higher postoperative TK than patients with notched rods (P < .001), but both groups achieved three-dimensional spinal corrections and significantly increased postoperative rates of patients with T6–T8 TK apex (P = .006 for notch-free rods and P = .008 for notched rods). The rod deformation angle at the concave side was significantly lower in the notch-free rods than in the notched rods (P < .001). The notch-free, pre-bent rod can maintain its curvature, leading to better correction or maintenance of TK after anatomical spinal correction surgery than the conventional notched rod. These results suggest the potential benefits of anatomically designed notch-free, pre-bent rods over conventional, manually bent rods.

Changes in peri-apical vertebral body and intervertebral disc shape in both the sagittal and coronal planes correlate with scoliosis severity: a 3D study of 397 patients.

To evaluate associations between vertebrae and disc shape asymmetry and adolescent idiopathic scoliosis (AIS) curve severity. Analysis included normal screening referrals and patients with right, main thoracic AIS who underwent upright, biplanar radiographs with 3D reconstruction at a single institution from 2010 to 2015. Peri-apical anterior, posterior, right, and left vertebral body heights (aVBH, pVBH, rVBH, lVBH) and intervertebral disc heights (DH) were measured, and ratios of these measurements were calculated in sagittal and coronal planes. Correlations were performed between curve severity and height measurements. Sagittal and coronal plane components of these measurements were compared between normal controls with coronal curve measurements < 11° and patients with moderate (11°-49°) and severe curves (≥ 50°), with tolerance intervals established for the normal controls. The analysis included a total of 397 patients. Patients with AIS had coronal curve measurements ranging from 11° to 101°. Greater coronal curve severity strongly correlated with smaller pVBH relative to aVBH and moderately correlated with smaller pDH relative to aDH (r = - 0.643, r = - 0.305, respectively). aVBH was greater for larger curves; pVBH remained stable. Scoliosis severity strongly correlated with right relative to left VBH and DH ratios (r = 0.919, r = 0.865 respectively). In comparison of normal controls to severe curves, severe curves had significantly greater aVBH and aDH, while pVBH was not significantly different and pDH was significantly less. Nearly half (46.9%) of the severe curves were below the range of normal for PA vertebral height ratio. In right, main thoracic AIS, greater main thoracic curve severity is associated with greater sagittal and coronal plane asymmetry of both the vertebral bodies and the discs. Severity more strongly correlates with vertebral changes in symmetry than with disc changes, though both are present.

Selection of the lowest instrumented vertebra in main thoracic adolescent idiopathic scoliosis: Is it safe to fuse shorter than the last touched vertebra?

Fusing shorter than the last touched vertebra (LTV) is a safe approach in flexible main thoracic (MT) adolescent idiopathic scoliosis (AIS) curves. This was a prospective study on consecutive AIS patients surgically treated with selective fusion of the MT curve. Fusion-level selection was based on the fulcrum-bending radiograph method. Patients were grouped based on the position of the lowest instrumented vertebra as proximal to the LTV (proxLTV, n = 43), at the LTV (atLTV, n = 45), and distal to the LTV (distLTV, n = 21). A total of 109 patients were included in the study. Preoperatively, the distLTV group had greater lumbar Cobb angle, lumbar apical translation, and less flexibility in the MT curve. At 2-year follow-up, the groups did not differ in MT curve correction, but the distLTV had larger lumbar Cobb angle, more apical translation, and worse coronal balance. Distal adding-on was observed in 11 patients (26%) in the proxLTV group, four patients (9%) in the atLTV group, and one patient (5%) in the distLTV group (p = 0.031). Adding-on was associated with younger patients and lower Risser grade at the time of surgery but not with any other radiographic parameter. No differences in SRS-22r scores were observed between the groups. Proximal fusion carries the risk of adding-on, but leaving unfused segments in the lower spine increases the potential for compensatory mechanisms to improve spinal and truncal balance. In mature patients with a flexible MT curve, surgeons may consider fusion at or cranial to the LTV.

Conservative treatment of main thoracic adolescent idiopathic scoliosis: Full-time or nighttime bracing?

To compare treatment efficacy between the Boston full-time brace and the Providence part-time brace in main thoracic adolescent idiopathic scoliosis (AIS). Patients were treated with either the Boston brace (n = 37) or the Providence brace (n = 40). Inclusion criteria were Risser grade ≤2, major curve between 25° and 40° with the apex of the curve between T7 and T11 vertebrae. Two-year follow-up was available in all patients unless brace treatment had reached endpoint. The primary outcome measure was main curve progression to ≥45°. Median age was 12.6 years and median treatment length at follow-up was 25 months (interquartile range (IQR): 18-32)) with no difference between the groups (p ≥ 0.116). Initial median main Cobb angle was 29° (IQR: 27-33) and 36° (IQR: 33-38) in the Boston and Providence groups, respectively (p < 0.001). At follow-up, 13 patients (35%) had progressed to ≥45° in the Boston group versus 16 patients (40%) in the Providence group (p = 0.838). Twenty-three patients (62%) had progressed by more than 5° in the Boston group versus 22 patients (55%) in the Providence group (p = 0.685). The secondary thoracolumbar/lumbar curve progressed by more than 5° in 14 (38%) and 18 (45%) in the Boston and Providence groups, respectively (p = 0.548). Despite a larger initial curve size in the Providence group, progression of more than 5° or to surgical indication area was similar in the Boston group. Our results indicate that nighttime bracing is a viable alternative to full-time bracing also in main thoracic AIS.

Postoperative translation of the upper instrumented vertebra in thoracic adolescent idiopathic scoliosis.

OBJECTIVEThe aim of this retrospective study was to analyze the influence of upper instrumented vertebra (UIV) translation from the C7 plumb line (C7PL) on the long-term postoperative results of patients with main thoracic (MT) adolescent idiopathic scoliosis (AIS).METHODSTwenty-five patients had been treated surgically for AIS with a Lenke type 1 curve and had been followed up for a mean period of 18.2 years. Radiographic parameters, pulmonary function measurements, and clinical outcomes were compared between the patients (n = 15) with UIV translation < 20 mm and those (n = 10) with UIV translation ≥ 20 mm at the final follow-up. Correlations between UIV translation and radiographic or pulmonary function parameters were analyzed.RESULTSPatients with ≥ 20 mm UIV translation at the final follow-up had a significantly larger preoperative UIV translation than that in the patients with < 20 mm UIV translation at follow-up. The former group also had a significantly lower correction rate of the MT curve, higher chest cage ratio, and lower radiographic shoulder height (p = 0.01, 0.005, and 0.025, respectively) at the final follow-up. The Scoliosis Research Society (SRS)-30 Questionnaire scores were equivalent between the two groups. Correlation analysis showed that the following parameters were significantly associated with UIV translation: MT curve correction rate (r = -0.481, p = 0.015), chest cage ratio (r = 0.673, p < 0.001), and percent-predicted forced expiratory volume in 1 second (r = -0.455, p = 0.033).CONCLUSIONSThe UIV translation should be considered an important factor that influences postoperative results. In MT AIS patients whose preoperative upper end vertebra (UEV) is distant from the C7PL, the UIV should be selected above the UEV to prevent large UIV translation at the postoperative follow-up.

Determination of optimal screw number based on correction angle for main thoracic curve in adolescent idiopathic scoliosis

BackgroundReducing the number of screw insertions while maintaining good clinical outcomes can improve the efficiency and cost-effectiveness of scoliosis surgery. However, the optimal minimum number of pedicle screws remains unclear. This study searched for factors to estimate the fewest number of pedicle screws required between end vertebrae in relation to preoperative main thoracic curve flexibility. MethodsSixty-nine subjects (4 male and 65 female, mean age: 14.8 ± 2.5 years) who underwent skip pedicle screw fixation for Lenke type 1–4 or 6 curves and were followed for at least 1 year were enrolled. Intervention technique was selected according to the size and flexibility of the preoperative main thoracic curve. Surgery-related variables included pedicle screw number, rod material and diameter, and extent of Ponte osteotomy. The effect on postoperative correction angle (i.e., the difference between the preoperative supine position maximum bending and postoperative standing Cobb angles of the main thoracic curve) according to surgical intervention technique was estimated using multiple linear mixed regression models with the preoperative supine position maximum bending correction angle (i.e., the difference between the standing preoperative and supine position maximum bending Cobb angles) as a random effect. ResultsThe preoperative maximum bending correction angle was 8–42° and had a moderate negative correlation with postoperative correction angle (r = −0.65, P < 0.01). Multivariate analysis revealed a 1.7° (95% CI 0.7–2.6; P < 0.01) correction gain per single-screw insertion and a 1.8° (95% CI 0.5–3.1; P < 0.01) gain per intervertebral level in Ponte osteotomy. ConclusionsThe number of pedicle screws necessary to correct main thoracic adolescent idiopathic scoliosis curves can be estimated by calculating correction gains of 1.7° per pedicle screw and 1.8° per Ponte osteotomy intervertebral level. Based on these results, it may be possible to reduce invasiveness and cost for patients requiring a smaller degree of correction.

Friday, September 28, 2018 10:30 AM–12:00 PM abstracts: deformity: technical factors: 171. The amount of curve correction is more important than upper instrumented vertebra selection for ensuring postoperative shoulder balance in Lenke type 1 adolescent idiopathic scoliosis

BACKGROUND CONTEXT Postoperative shoulder height imbalance is a common complication following adolescent idiopathic scoliosis (AIS) surgery. It is thought that a more cephalad upper instrumented vertebra (UIV) decreases the risk of shoulder imbalance in Lenke type 1 curves, however this has not been proven. PURPOSE To test the hypothesis that “over-correction” of the main thoracic curve without control of the proximal curve increases the risk for shoulder imbalance in Lenke type 1 AIS. STUDY DESIGN/SETTING Clinical photo and x-ray review of patients with Lenke 1 Main Thoracic AIS curves. PATIENT SAMPLE Surgically-treated patients with Lenke type 1 AIS were reviewed from a large multicenter database. OUTCOME MEASURES Postoperative shoulder height balance on clinical photos and PA radiographs. METHODS A total of 13 surgeons reviewed preop and 5-year postop clinical photos and PA radiographs of patients from a large multicenter database with Lenke type 1 AIS curves who were corrected with pedicle screw or rod constructs. Predictors of postop shoulder imbalance were identified by univariate analysis; multivariate analysis was done using the classification and regression tree (CART) method to identify independent drivers of shoulder imbalance. RESULTS A total of 145 patients were reviewed. The UIV was T3-T5 in 87% of patients, with 8.9% instrumented up to T1 or T2. 52 (36%) had shoulder imbalance at 5 years. On CART analysis: when the proximal thoracic (PT) Cobb angle was corrected more than 52%, 80% of the patients had balanced shoulders. Similarly, when the PT curve was corrected less than 52% and the main thoracic (MT) curve was corrected less than 54%, 87% were balanced. However, when the PT curve was corrected less than 52%, and the MT curve was corrected more than 54%, only 41% of patients had balanced shoulders (p=0.05). This relationship was maintained regardless of the UIV level. CONCLUSIONS In Lenke type 1 AIS curves, “over-correction” of the main thoracic curve (>54%) with simultaneous “under-correction” (

Predictors of ultimate postoperative cervical sagittal alignment in main thoracic adolescent idiopathic scoliosis: A long-term follow-up study.

This is a retrospective study. The aim of this study was to access sagittal compensatory mechanism of the cervical spine in thoracic adolescent idiopathic scoliosis (T-AIS) before and after posterior spinal fusion and to identify preoperative or immediate postoperative radiographic parameters that can predict the ultimate cervical sagittal alignment (CSA) after long-term follow-up.A retrospective study was performed on 44 T-AIS patients treated with posterior spinal fusion and with at least 5 years of follow-up. Preoperative, immediate postoperative and latest follow-up radiographs were reviewed measuring cervical lordosis (CL), cervical sagittal vertical axis (CSVA), upper thoracic kyphosis (UTK), main thoracic kyphosis (MTK), global thoracic kyphosis (GTK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). Pearson correlation analysis, stepwise multilinear regression analysis, and receiver operator characteristic (ROC) curve were performed to define the relationship between ultimate CL and preoperative or immediate postoperative radiographic parameters.CL significantly improved from 6.6 ± 8.8 degree kyphosis preoperatively to 3.8 ± 8.7 degree kyphosis immediate postoperatively and to 0.5 ± 7.3 degree lordosis at the latest follow-up. Pre- and postoperative CSVA showed no significant difference. Pearson correlation coefficient test showed that CL was only correlated to T1 slope and UTK before surgery, whereas it was correlated to T1 slope, UTK, and GTK after surgery. The following equation was developed to estimate the ultimate CL: ultimate CL = −2.792 + 0.510 × Preop CL + 0.531 × Postop T1 slope. Furthermore, ROC curve showed that preoperative CL ≥−4.5 degree was strongly predictive and postoperative T1 slope ≥11.3 degree was moderately predictive of lordotic cervical spine after long-term follow-up.For T-AIS patients, CL significantly increased after surgery with the restoration of the global and regional sagittal profile. The sagittal compensatory mechanism of the cervical spine before surgery is different from that after surgery. In these patients, preoperative CL and immediate postoperative T1 slope could be predictors of the ultimate CSA after long-term follow-up.

Key Vertebral Pedicle Screw Strategy for the Correction of Flexible Lenke Type 1 Adolescent Idiopathic Scoliosis

A retrospective clinical and radiographic study. The aim of this study was to evaluate outcomes of the key vertebral pedicle screw strategy (KVPSS) for the correction of flexible Lenke type 1 adolescent idiopathic scoliosis (AIS) with a minimum follow-up of 5 years. The KVPSS has been described as an alternative screw placement strategy for surgically treating the main thoracic curve in AIS patients. However, there have been no long-term, three-dimensional correction studies of selective thoracic fusion using the KVPSS in Lenke type 1AIS. Twenty consecutive patients with Lenke type 1 main thoracic AIS underwent one-stage posterior correction and fusion using the KVPSS. Preoperative and postoperative radiographic and clinical parameters were analyzed. The mean preoperative major thoracic curve was 47.4° ± 5.8°, and mean corrections of 67.0%, 63.4%, and 61.5% were observed at the immediate, 2-year postoperative, and final follow-ups, respectively. Thoracickyphosis decreased significantly from the preoperative period to the immediate postoperative period (P = 0.042) but did not change significantly from the 2-year postoperative follow-up to the final follow-up (P = 0.067). Apical vertebral rotation achieved 34.7% correction and exhibited correction loss of 8.2% at the final follow-up. The average intraoperative blood loss was 802.3 mL, and the mean operative time was 138.6 minutes. SRS-22 scores for self-image and satisfaction improved significantly from the preoperative period to the final follow-up. No neurologic or implant-associated complications were observed in this study. The KVPSS is an effective method for correcting Lenke type 1 AIS and achieves satisfactory correction of the deformity. Relative to other approaches, the KVPSS can not only achieve a satisfactory and cost-effective clinical outcome but also reduce both operative time and intraoperative blood loss. 4.

Preventing Fusion Mass Shift Avoids Postoperative Distal Curve Adding-on in Adolescent Idiopathic Scoliosis.

Surgery for adolescent idiopathic scoliosis (AIS) is only complete after achievingfusion to maintain the correction obtained intraoperatively. The instrumented or fused segments can be referred to as the "fusion mass". In patients with AIS, the ideal fusion mass strategy has been established based on fulcrum-bending radiographs for main thoracic curves. Ideally, the fusion mass should achieve parallel endplates of the upper and lower instrumented vertebra and correct any "shift" for truncal balance. Distal adding-on is an important element to consider in AIS surgery. This phenomenon represents a progressive increase in the number of vertebrae included distally in the primary curvature and it should be avoided as it is associated with unsatisfactory cosmesis and an increased risk of revision surgery. However, it remains unknown whether any fusion mass shift, or shift in the fusion mass or instrumented segments, affects global spinal balance and distal adding-on after curve correction surgery in patients with AIS. (1) To investigate the relationship among postoperative fusion mass shift, global balance, and distal adding-on phenomenon in patients with AIS; and (2) to identify a cutoff value of fusion mass shift that will lead to distal adding-on. This was a retrospective study of patients with AIS from a single institution. Between 2006 and 2011 we performed 69 selective thoracic fusions for patients with main thoracic AIS. All patients were evaluated preoperatively and at 2 years postoperatively. The Cobb angle between the cranial and caudal endplates of the fusion mass and the coronal shift between them, which was defined as "fusion mass shift", were measured. Patients with a fusion mass Cobb angle greater than 20° were excluded to specifically determine the effect of fusion mass shift on distal adding-on phenomenon. Fusion mass shift was empirically set as 20 mm for analysis. Therefore, of the 69 patients who underwent selective thoracic fusion, only 52 with a fusion mass Cobb angle of 20° or less were recruited for study. We defined patients with a fusion mass shift of 20 mm or less as the balanced group and those with a fusion mass shift greater than 20 mm as the unbalanced group. A receiver operating characteristic (ROC) curve was used to determine the cutoff point of fusion mass shift for adding-on. Of the 52 patients studied, fusion mass shift (> 20 mm) was noted in 11 (21%), and six of those patients had distal adding-on at final followup. Although global spinal balance did not differ significantly between patients with or without fusion mass shift, the occurrence of adding-on phenomenon was significantly higher in the unbalanced group (55% (six of 11 patients), odds ratio [OR], 8.6; 95% CI, 2-39; p < 0.002) than the balanced group (12% [five of 41 patients]). Based on the ROC curve analysis, a fusion mass shift more than 18 mm was observed as the cutoff point for distal adding-on phenomenon (area under the curve, 0.70; 95% CI, 0.5-0.9; likelihood ratio, 5.0; sensitivity, 0.64; specificity, 0.73; positive predictive value, 39% [seven of 18 patients]; negative predictive value, 88% [30 of 34 patients]; OR, 4.8; 95% CI, 1-20; p = 0.02). Our study illustrates the substantial utility of the fulcrum-bending radiograph in determining fusion levels that can avoid fusion mass shift; thereby, underlining its importance in designing personalized surgical strategies for patients with scoliosis. Preoperatively, determining fusion levels by fulcrum-bending radiographs to avoid residual fusion mass shift is imperative. Intraoperatively, any fusion mass shift should be corrected to avoid distal adding-on, reoperation, and elevated healthcare costs. Level II, prognostic study.

The effect of sublaminar wires on the rib hump deformity during scoliosis correction manoeuvres.

During thoracic curve correction, the tightening of the sublaminar wires through concavity creates a medial and a dorsal translation of the spine. However, little is known about the effect of the sublaminar wires on the axial plane. This is prospective case series analysis of 30 consecutive surgical patients with main thoracic adolescent idiopathic scoliosis. All of the patients were fused with hybrid instrumentation (apical concavity-sublaminar wires) and differential rod contouring (over-kyphosis concavity/under-kyphosis convexity). The degrees of the rib hump were measured with a scoliometer placed at the apex of the deformity at five different times: (1) preoperatively through the Adam's test, and during surgery (sterilised scoliometer), (2) with the patient lying prone, (3) after the Ponte osteotomies, (4) after the apical sublaminar tightening, and (5) after convexity apical derotation and compression manoeuvres. (1) Preoperatively, the Adam's test was 16.3°±4.6. (2) Lying prone and under general anaesthesia, it decreased to 11.4°±3.9. (3) After exposure and Ponte osteotomies, it was 7.1°±4. (4) After the wire tightening, it was 10.8°±4.7. (5) After the convexity manoeuvres, it was 4.8°±3.7. The degrees of the rib hump final correction were 11.6°±4 (70% correction). The tightening of the sublaminar wires increased the rib hump by 3.5°. The sublaminar wire tightening towards the concave rod seemed to create an effect opposite of the desired effect, increasing the apical rotation and the thoracic rib hump deformity. Convexity manoeuvres (apical screw derotation and compression) are necessary and must be coupled with an under-bending of the convex rod to neutralise this effect.

Maintenance of spontaneous lumbar curve correction following thoracic fusion of main thoracic curves in adolescent idiopathic scoliosis.

The aims of our study were to provide long-term information on the behaviour of the thoracolumbar/lumbar (TL/L) curve after thoracic anterior correction and fusion (ASF) and to determine the impact of ASF on pulmonary function. A total of 41 patients (four males, 37 females) with main thoracic (MT) adolescent idiopathic scoliosis (AIS) treated with ASF were included. Mean age at surgery was 15.2 years (11 to 27). Mean follow-up period was 13.5 years (10 to 18). For the TL/L curve, the mean curve flexibility evaluated with supine pre-operative bending radiographs was 78.6% (standard deviation 16.5%), with no significant loss of correction observed. On comparing patients with an increase of the TL/L curve increase (> 4º, n = 9, 22%) to those without, significant differences were observed in the correction rate of the MT curve at the final follow-up (p = 0.011), correction loss of the MT curve (p = 0.003) and the proportion of patients who had semi-rigid instrumentation (p = 0.003). Pre-operative percentage predicted forced vital capacity (%FVC) was 80%, dropping to 72% at final follow-up (p < 0.001). The Scoliosis Research Society questionnaire score was not significantly different between patients with and without a TL/L curve increase (p = 0.606). Spontaneous lumbar curve correction (SLCC) was maintained up to 18 years following selective ASF in most patients and demonstrated significant correlation with maintenance of MT curve correction. Maintenance of MT curve correction using rigid instrumentation provided stable SLCC over time. An observed 8% decrease in %FVC indicates that ASF should be reserved for patients with no or only mild pulmonary impairment. Cite this article: Bone Joint J 2016;98-B:997-1002.

Correlation analysis between change in thoracic kyphosis and multilevel facetectomy and screw density in main thoracic adolescent idiopathic scoliosis surgery

Background ContextControversy exists regarding the effects of multilevel facetectomy and screw density on deformity correction, especially thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. PurposeThis study aimed to evaluate the effects of multilevel facetectomy and screw density on sagittal plane correction in patients with main thoracic (MT) AIS curve. Study DesignA retrospective correlation and comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution was undertaken. Patient SampleSixty-four consecutive patients with Lenke type 1 AIS treated with posterior correction and fusion surgery using simultaneous double-rod rotation technique were included. Outcome MeasuresPatient demographics and preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study. MethodsMultiple stepwise linear regression analysis was conducted between change in TK (T5–T12) and the following factors: age at surgery, Risser sign, number of facetectomy level, screw density, preoperative main thoracic curve, flexibility in main thoracic curve, coronal correction rate, preoperative TK, and preoperative lumbar lordosis. Patients were classified into two groups: TK<15° group defined by preoperative TK below the mean degree of TK for the entire cohort (<15°) and the TK≥15° group, defined by preoperative TK above the mean degree of kyphosis (≥15°). Independent sample t tests were used to compare demographic data as well as radiographic outcomes between the two groups. There were no study-specific biases related to conflicts of interest. ResultsThe average preoperative TK was 14.0°, which improved significantly to 23.1° (p<.0001) at the 2-year final follow-up. Greater change in TK was predicted by a low preoperative TK (p<.0001). The TK <15° group showed significant correlation between change in TK and number of facetectomy level (r=0.492, p=.002). Similarly, significant correlation was found between change in TK and screw density (r=0.333, p=.047). Conversely, in the TK ≥15° group, correlation was found neither between change in TK and number of facetectomy level (r=0.047, p=.812), nor with screw density (r=0.030, p=.880). Furthermore, in patients with preoperative TK<15°, change in TK was significantly correlated with screw density at the concave side (r=0.351, p=.036) but not at the convex side (r=0.144, p=.402). ConclusionsIn patients with hypokyphotic thoracic spine, significant positive correlation was found between change in TK and multilevel facetectomy or screw density at the concave side. This indicates that in patients with AIS who have thoracic hypokyphosis as part of their deformity, the abovementioned factors must be considered in preoperative planning to correct hypokyphosis.

Using Skin Markers for Spinal Curvature Quantification in Main Thoracic Adolescent Idiopathic Scoliosis: An Explorative Radiographic Study.

Background and PurposeAlthough the relevance of understanding spinal kinematics during functional activities in patients with complex spinal deformities is undisputed among researchers and clinicians, evidence using skin marker-based motion capture systems is still limited to a handful of studies, mostly conducted on healthy subjects and using non-validated marker configurations. The current study therefore aimed to explore the validity of a previously developed enhanced trunk marker set for the static measurement of spinal curvature angles in patients with main thoracic adolescent idiopathic scoliosis. In addition, the impact of inaccurate marker placement on curvature angle calculation was investigated.MethodsTen patients (Cobb angle: 44.4±17.7 degrees) were equipped with radio-opaque markers on selected spinous processes and underwent a standard biplanar radiographic examination. Subsequently, radio-opaque markers were replaced with retro-reflective markers and the patients were measured statically using a Vicon motion capture system. Thoracolumbar / lumbar and thoracic curvature angles in the sagittal and frontal planes were calculated based on the centers of area of the vertebral bodies and radio-opaque markers as well as the three-dimensional position of the retro-reflective markers. To investigate curvature angle estimation accuracy, linear regression analyses among the respective parameters were used. The impact of inaccurate marker placement was explored using linear regression analyses among the radio-opaque marker- and spinous process-derived curvature angles.Results and DiscussionThe results demonstrate that curvatures angles in the sagittal plane can be measured with reasonable accuracy, whereas in the frontal plane, angles were systematically underestimated, mainly due to the positional and structural deformities of the scoliotic vertebrae. Inaccuracy of marker placement had a greater impact on thoracolumbar / lumbar than thoracic curvature angles. It is suggested that spinal curvature measurements are included in marker-based clinical gait analysis protocols in order to enable a deeper understanding of the biomechanical behavior of the healthy and pathological spine in dynamic situations as well as to comprehensively evaluate treatment effects.

Pressure distribution of intraoperative chest pad designs in patients with adolescent idiopathic scoliosis.

A prospective, comparative study. To evaluate the resultant force and pressure distribution between chest pad designs for scoliosis patients while in the prone position. Scoliosis affects the anatomy of the lungs and the chest wall, which can adversely affect pulmonary function. Scoliosis surgery requires that patients remain prone for several hours with their body weight supported by pads under the chest and pelvis. As a significant portion of the patient's weight is on the chest, this extrinsic pressure may further affect the pulmonary status of already compromised lungs. Fourteen female subjects with right main thoracic adolescent idiopathic scoliosis of at least 45 degrees were evaluated. A Jackson Spinal Surgery and Imaging Table (Orthopaedic Systems Inc.) was used with commercially available (Vista Medical) pressure transducer mats that were overlaid on the chest and hip supports. Awake subjects were positioned on the table during 2 testing conditions: 1 chest pad versus 2 chest pads on the table. Over a 60-second testing period for each condition, the average and maximum pressures and resultant force were found for each pad. The 1 and 2 pad systems had average chest pressures of 4.51±1.07 versus 3.10±0.64 kPa (P<0.05), and maximum chest pressures of 12.9±3.1 versus 9.44±3.14 kPa (P<0.05). The 1 and 2 pad systems had average pelvic pressures of 2.67±0.57 versus 2.98±0.56 kPa (P<0.05), and maximum pelvic pressures of 15.1±7.8 versus 19.4±0.8 kPa (P<0.05). The 2 pad chest support system resulted in lower maximum and average pressures at the chest and higher maximum and average pressures at the pelvis as compared with the 1 pad design.

Surgical treatment of Lenke 1 thoracic adolescent idiopathic scoliosis with maintenance of kyphosis using the simultaneous double-rod rotation technique.

Retrospective analysis of a prospectively collected, consecutive, nonrandomized series of patients. To assess the surgical outcomes of the simultaneous double-rod rotation technique for treating Lenke 1 thoracic adolescent idiopathic scoliosis (AIS). With the increasing popularity of segmental pedicle screw spinal reconstruction for treating AIS, concerns regarding the limited ability to correct hypokyphosis have also increased. A consecutive series of 32 patients with Lenke 1 main thoracic AIS treated with the simultaneous double-rod rotation technique at our institution was included. Outcome measures included patient demographics, radiographical measurements, and Scoliosis Research Society questionnaire scores. All 32 patients were followed up for a minimum of 2 years (average, 3.6 yr). The average main thoracic Cobb angle correction rate and the correction loss at the final follow-up were 67.8% and 3.3°, respectively. The average preoperative thoracic kyphosis (T5-T12) was 11.9°, which improved significantly to 20.5° (P < 0.0001) at the final follow-up. An increase in thoracic kyphosis was significantly correlated with an increase in lumbar lordosis at the final follow-up (r = 0.42). The average preoperative vertebral rotation angle was 19.7°, which improved significantly after surgery to 14.9° (P = 0.0001). There was no correlation between change in thoracic kyphosis and change in apical vertebral rotation (r =-0.123). The average preoperative total Scoliosis Research Society questionnaire score was 3.0, which significantly improved to 4.4 (P < 0.0001) at the final follow-up. Throughout surgery and even after, there were no instrumentation failures, pseudarthrosis, infection of the surgical site, or clinically relevant neurovascular complications. The simultaneous double-rod rotation technique for treating Lenke 1 AIS provides significant sagittal correction of the main thoracic curve while maintaining sagittal profiles and correcting coronal and axial deformities. 4.

Does curve convexity affect the surgical outcomes of thoracic adolescent idiopathic scoliosis?

Major left thoracic (LT) curve is an atypical type in adolescent idiopathic scoliosis (AIS) and showed independent clinical characteristics and natural history compared to major right thoracic (RT)curve. However, it's unclear whether the convexity of major thoracic curve would affect the surgical outcomes and risk of complications. A retrospective follow-up study was conducted to investigate whether the convexity of major thoracic curve would affect the surgical outcomes of patients with main thoracic AIS. Twelve LT-AIS patients underwent corrective spinal instrumentation and fusion were retrieved, and twelve patients with main RT-AIS matched for gender, chronological age, curve type, magnitude and surgical strategy were selected as control. All patients underwent at least 2-year follow-up. The pre- and post-operative radiographic parameters, intraoperative data and functional outcome assessed by Scoliosis Research Society questionnaire 22 (SRS-22) were analyzed and compared between two groups. Patients with LT- and RT-AIS presented with similar magnitudes of thoracic curves, flexibility, fusion level and correction rate. Compared with RT-AIS, patients with LT-AIS showed longer operation time (average, 364 vs. 348min) and larger amount intraoperative estimated blood loss (2,060 vs. 1,720ml) although the differences were not statistically significant (p>0.05). With at least 2-year follow-up, patients in two groups showed comparable loss of correction, coronal and sagittal balance, and the sagittal profiles. With regard to functional outcome, the scores of five categories of SRS-22 questionnaire were similar between two groups. No neurological or vascular complication was observed in these patients. The radiographic and functional outcomes of LT-AIS patients underwent operation were comparable to those with RT-AIS. Longer operation time and more intraoperative blood loss may be expected in instrumentation and fusion for patients with LT-AIS, which might be because of the inconvenience on the surgical procedure.

Long-term Outcomes of Anterior Spinal Fusion for Treating Thoracic Adolescent Idiopathic Scoliosis Curves

Retrospective review. To assess the long-term outcomes of anterior spinal fusion (ASF) for treating thoracic adolescent idiopathic scoliosis (AIS). Although ASF is reported to provide good coronal and sagittal correction of the main thoracic (MT) AIS curves, the long-term outcomes of ASF is unknown. A consecutive series of 25 patients with Lenke 1 MT AIS were included. Outcome measures comprised radiographical measurements, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores (preoperative SRS-30 scores were not documented). Postoperative surgical revisions and complications were recorded. Twenty-five patients were followed-up for 12 to 18 years (average, 15.2 yr). The average MT Cobb angle correction rate and the correction loss at the final follow-up were 56.7% and 9.2°, respectively. The average preoperative instrumented level of kyphosis was 8.3°, which significantly improved to 18.6° (P = 0.0003) at the final follow-up. The average percent-predicted forced vital capacity and forced expiratory volume in 1 second were significantly decreased during long-term follow-up measurements (73% and 69%; P = 0.0004 and 0.0016, respectively). However, no patient had complaints related to pulmonary function. The average total SRS-30 score was 4.0. Implant breakage was not observed. All patients, except 1 who required revision surgery, demonstrated solid fusion. Late instrumentation-related bronchial problems were observed in 1 patient who required implant removal and bronchial tube repair, 13 years after the initial surgery. Overall radiographical findings and patient outcome measures of ASF for Lenke 1 MT AIS were satisfactory at an average follow-up of 15 years. ASF provides significant sagittal correction of the main thoracic curve with long-term maintenance of sagittal profiles. Percent-predicted values of forced vital capacity and forced expiratory volume in 1 second were decreased in this cohort; however, no patient had complaints related to pulmonary function.

Analysis of Concave and Convex Rib-vertebral Angle, Angle Difference, and Angle Ratio in Patients With Lenke Type 1 Main Thoracic Adolescent Idiopathic Scoliosis Treated by Observation, Bracing or Posterior Fusion, and Instrumentation

Retrospective review. The aim of this study is to describe the radiologic changes in rib-vertebral angles (RVAs), rib-vertebral angle differences (RVADs), and rib-vertebral angle ratios (RVARas) in patients with Lenke type 1 main thoracic adolescent idiopathic scoliosis treated by observation, bracing, or posterior fusion and instrumentation, and to compare these with normal individuals. The RVA measurement has been shown to be a valid and reproducible method and its asymmetries are related to age, sex, and laterality patterns of the curvature. However, studies of RVA and RVAD in patients with adolescent idiopathic scoliosis are scarce and there are no data regarding the assessment of the ratio between concave and convex RVA. A retrospective chart and radiograph review was carried out for 66 consecutive adolescent female patients with Lenke type 1 main thoracic idiopathic scoliosis and 14 normal counterparts. Patients were divided into 5 groups: normal individuals (group 1); scoliotic patients with Cobb angle <30 degrees (group 2A); scoliotic patients with Cobb angle more than 30 degrees (group 2B), scoliotic patients treated by bracing (group 3), and scoliotic patients treated by posterior fusion and instrumentation (group 4). Overall values (mean ± SD) of the RVAs on the concave side were 90.5 ± 17 degrees in group 1, 90.3 ± 15.8 degrees in group 2A, 88.8 ± 15.4 degrees in group 2B, 87.5 ± 13.3 degrees in group 3, and 86.7 ± 17 degrees in group 4. On the convex side, values were 90.0 ± 17.3 degrees in group 1, 86.3 ± 13.7 degrees in group 2A, 80.7 ± 14.4 degrees in group 2B, 82.9 ± 13.2 degrees in group 3, and 81.7 ± 16.2 degrees in group 4. Overall values (mean ± SD) of the RVADs at all levels were 0.5 ± 0.7 degrees in group 1, 4 ± 4.8 degrees in group 2A, 8 ± 4 degrees in group 2B, 4.7 ± 5.6 degrees in group 3, and 5.1 ± 5.2 degrees in group 4. The RVARa values (mean ± SD) at all levels were 1.008 ± 0.012 degrees in group 1, 1.041 ± 0.061 degrees in group 2A, 1.102 ± 0.151 degrees in group 2B, 1.056 ± 0.078 degrees in group 3, and 1.061 ± 0.071 degrees in group 4. Convex RVA was smaller than concave RVA between T1 and T10 in all groups of patients. RVAD and RVARa values in the scoliotic segment were greater in patients with untreated scoliosis more than 40 degrees than in patients with an untreated deformity of <25 degrees or in patients, treated by bracing or surgery, with a residual curve of <25 degrees. These measurements are a useful tool in the armamentarium of the surgeon treating spinal deformities and could be used to better characterize the deformity and/or to evaluate effects of brace or surgical treatment.