Five major controversial issues about fusion level selection in corrective surgery for adolescent idiopathic scoliosis: a narrative review

Comparison of traction, side-bending and dead-hang radiographs in preoperative evaluation and postoperative correction prediction in adolescent idiopathic scoliosis: A retrospective analysis of a novel flexibility radiograph

A retrospective study comparing traction, dead-hang, and side-bending radiographs in adolescent idiopathic scoliosis to compare the effectiveness of dead-hang radiography in structural and nonstructural curves and evaluate it in terms of postoperative correction prediction. In the surgical correction of adolescent idiopathic scoliosis, flexibility radiographs have an important role in determining fusion levels and in surgical decision-making. Supine bending radiographs are presently considered the gold standard, but their reliability, reproducibility, and standardization along with traction films, are a subject of debate. In our clinic, dead-hang radiographs are also used as an alternative flexibility film. The role of dead-hang radiography against other flexibility radiographs is unknown. A total of 33 patients with adolescent idiopathic scoliosis were evaluated with preoperative standing, lateral, supine traction, dead-hang, supine side-bending, and postoperative standing films. Flexibility and correction rates were assessed. In structural main thoracic (MT) and thoracolumbar/lumbar (TL/L) curves, dead-hang showed significantly higher flexibility compared with traction (P < .001). In MT curves > 60°, dead-hang was superior to side-bending and traction, whereas in MT curves < 50°, side-bending showed more improvement (P < .05). Side-bending showed higher flexibility in TL/L curves < 50° (P < .05). No predictive value was found in structural curves for all 3 radiographs. In nonstructural curves, side-bending films showed over-correction while traction radiographs remained below postoperative correction. Dead-hang radiographs showed very similar flexibility to postoperative correction. Dead-hang radiograph is superior to traction. In MT curves > 60°, dead hang shows greater flexibility than side-bending. Dead-hang technique, which shows equal results with side-bending except in TL/L curves < 50°, is a successful flexibility radiograph and provides predictive value for nonstructural curves in terms of postoperative correction.

Influence of the thoracolumbar junction flexibility on the risk of adding-on after posterior vertebral arthrodesis for thoracic idiopathic adolescent scoliosis

PURPOSE

The objective was to analyze the role of the thoracolumbar sagittal flexibility on the outcome after posterior spinal fusion of Lenke 1 and 2 adolescent idiopathic scoliosis with last touched vertebra as the lowest instrumented vertebra.

METHODS

We included 105 thoracic AIS patients who had a posterior spinal fusion with a 2 years minimum follow-up. Thoracolumbar junction flexibility was assessed on dynamic sagittal X-rays and compared to the standing position. Adding-on was defined according to radiographic Wang criteria. The junction was considered flexible if the variability from the static position to flexion and/or extension was greater than 10°.

RESULTS

Mean age of the patients was 14 ± 2 years. The preoperative mean Cobb angle was 61 ± 12.7° and 27.5 ± 7.7° after surgery. Mean follow-up was 3.1 years. Twenty-nine patients (28%) developed an adding-on. Thoracolumbar junction range of motion was higher (p = 0.017) with higher flexibility in flexion (p < 0.001) in the no adding-on group. In no adding-on group, 53 patients (70%) had a flexible thoracolumbar junction, and 23 patients (30%) had a stiff thoracolumbar junction in flexion and flexible in extension. In adding-on group, 27 patients (93%) had a stiff thoracolumbar junction, and 2 patients (7%) had a flexible junction in flexion and stiff in extension.

CONCLUSION

The flexibility of the thoracolumbar junction is a determining factor in the surgical outcome after posterior spinal fusion for AIS and should be considered in correlation with the frontal and sagittal alignment of the spine.

Is it Safe to Save Levels and Choose the Lowest Instrumented Vertebra as Touched Vertebra While Selectively Fusing Lenke 1/2 Curves? A Proportional Meta-Analysis of Existing Evidence

STUDY DESIGN

Meta-analysis.

OBJECTIVE

To compare the clinical and radiological outcomes in patients with Adolescent Idiopathic scoliosis (AIS) treated by selective thoracic fusion (STF) with lowest instrumented vertebra (LIV) at touched vertebra (TV) vs stable vertebra (SV).

METHODS

The databases PubMed, Embase and Google Scholar were searched until November 2020.Studies which had Lenke type 1 curves and Lenke type 2 curves in adolescent population treated by STF and which reported pre- and post-operative curve characteristics including correction percentage and complications were included. Studies which did not report the LIV selection, curve correction percentages and whose full text could not be acquired were excluded.

RESULTS

Eight studies were included for analysis of which seven were found to be retrospective studies (level III evidence) and one was prospective study (level II evidence) each. Overall proportional meta-analysis found no significant difference in correction rate, total srs-22 scores, and complication rates.

CONCLUSION

The evaluation of SV group and TV group as LIV for selective thoracic fusions in AIS reveals a comparable outcome in terms of curve correction, patient satisfaction scores and complication rates. The TV can be chosen safely as the LIV especially in type A and B Lenke 1&2 curves, as it saves more motion segments when compared to SV.

Postoperative shoulder balance in Lenke type 1 adolescent idiopathic scoliosis patients with large thoracic curve (Cobb angle ≥ 70 degrees): a radiographic study

Background

Large amounts of thoracic curve correction had been considered as a risk factor for postoperative shoulder imbalance (PSI) in adolescent idiopathic scoliosis (AIS) patients. This study aims to evaluate postoperative shoulder balance in Lenke type 1 AIS patients with large thoracic curve (Cobb angle ≥ 70 degrees) and compared it with those with moderate thoracic curve (Cobb angle < 70 degrees).

Methods

A total of 47 Lenke type 1 AIS patients underwent posterior correction surgery between Sept. 2016 to Nov. 2018 in our institution were included. All these patient were divided into 2 groups based on the severity of main thoracic (MT) curve. Group A consisted of 25 cases with MT curve equal to or more than 70 degree while Group B consisted of 22 cases with MT curve less than 70 degree. Proximal thoracic (PT) Cobb angle, MT Cobb angle, MT apical vertebral translation (AVT), T2-T5 kyphosis, T5-T12 kyphosis, and radiographic shoulder height (RSH) were compared between these 2 groups preoperatively, immediately after surgery, and at a minimum of two-year follow-up.

Results

Although all the correction of PT Cobb angle (15.8° ± 6.0° vs 12.5° ± 3.6°, P = 0.028), that of MT Cobb angle 47.3° ± 9.1° vs 30.9° ± 6.7°, P < 0.001) and that of MT AVT (35.1 mm ± 16.0 mm vs 24.1 mm ± 8.9 mm, P = 0.007) were significantly larger in Group A when compared with Group B, RSH was comparable between these 2 groups at last follow up (7.5 mm ± 7.4 mm vs 9.2 mm ± 4.2 mm P = 0.363). Most of the patients gained satisfactory shoulder balance with only 7 cases with minimal PSI in group A (28%) and only 6 cases with minimal PSI in group B (27.3%) at last follow-up (P > 0.05).

Conclusions

Although Lenke type 1 AIS patients with large thoracic curve had more amounts of MT curve correction when compared with those with moderate thoracic curve, it did not lead to higher incidence of PSI if the correction rate is proper.

Prediction of long-term postoperative results of disc wedge and vertebral tilt with intraoperative prone radiograph in posterior correction of thoracolumbar/lumbar curve in adolescent idiopathic scoliosis: a minimum 5-year follow-up

BACKGROUND CONTEXT

Preservation of the more mobile lumbar segments is important during thoracolumbar/lumbar scoliosis surgery; however, the remaining disc wedge angle (DWA) below lowermost instrumented vertebra (LIV) and vertebral body tilt below LIV (LIV+1 tilt) can cause curve progression.

PURPOSE

This study aimed to evaluate the efficacy of intraoperative radiograph to predict the postoperative DWA below LIV and LIV+1 tilt on standing radiographs in patients with LIV of L3 or L4.

STUDY DESIGN/SETTING

Retrospective cohort study PATIENT SAMPLE: A total of 235 patients with idiopathic scoliosis who underwent posterior correction and fusion for the structural thoracolumbar curve and were followed up for >5 years were reviewed.

OUTCOME MEASURES

DWA below LIV, LIV+1 tilt, Cobb angle, trunk shift, apical vertebra translation, and pelvic parameters were measured.

METHODS

Correlation between intraoperative and postoperative measurements of DWA below LIV and LIV+1 tilt were assessed. Additional analysis was performed to identify risk factors and prognosis of LIV+1 tilt ≥10° and DWA below LIV of ≥4° RESULTS: LIV+1 tilt measured on intraoperative radiograph was significantly correlated with the postoperative 5-day and postoperative 5-year evaluation in both groups. However, the intraoperative DWA below LIV was only correlated with the postoperative 5-year value in the L3 group (p=.018). At the 5-year follow-up, patients with LIV+1 tilt ≥10° on intraoperative radiography showed significantly greater LIV+1 tilt (p<.001), apical vertebral translation (p<.001), thoracic curve (p=.008), and thoracolumbar curve (p<.001) than patients with LIV+1 tilt <10°. Intraoperative DWA below LIV of ≥4° was only associated with higher DWA below LIV at the 5-year follow-up.

CONCLUSIONS

Intraoperative measurement of LIV+1 tilt was correlated with long-term postoperative outcomes, and intraoperative LIV+1 tilt ≥10° was associated with a less favorable radiographic outcome. Intraoperative DWA below LIV demonstrated less correlation with postoperative values and was not a prognostic factor for other radiographic parameters.

Defining risk factors for adding-on in Lenke 1 and 2 AR curves

PURPOSE

To identify curve/correction characteristics associated with adding-on at 2 years after posterior spinal fusion (PSF) in Lenke 1/2 AR curves.

METHODS

A prospective multicenter registry was queried to identify patients with adolescent idiopathic scoliosis (AIS), Lenke 1/2 AR curves, who underwent PSF with a minimum of 2-year follow-up. Patient characteristics as well as pre- and post- operative radiographic variables were evaluated using Classification and Regression Tree (CART) analysis to determine which factors contribute to adding-on.

RESULTS

253 patients treated with PSF were assessed for adding-on, of which 50 met our adding-on criteria. Univariate analysis revealed adding-on was associated several factors including: post-operative thoracic and lumbar curve magnitude (p > 0.001), first erect (FE) end instrumented vertebra (EIV) angulation (p = 0.009) and EIV translation (p = 0.001), younger age (p = 0.027), Risser stage (p = 0.024), and a more proximal lowest instrumented vertebra (LIV) (p < 0.001). Multivariate CART analysis showed the chance of adding-on was more than 2 times greater (42 vs 16%) when the chosen LIV was translated more than 2.7 cm from the CSVL. When the LIV was within 2.7 cm, the post-op risk of adding-on was increased when the LIV was not perfectly leveled (> 0.5°).

CONCLUSION

In Lenke 1 and 2 AR curves, pre-operative LIV translation appears to be an independent risk factor for adding-on; and in those with < 2.7 cm of LIV translation, FE LIV angulation also seems to increase the risk of adding-on. These factors are relevant in determining appropriate LIV selection and aid in identifying patients at risk for developing adding-on.

Risk factors for persistent coronal imbalance or revision surgery following L3 LIV selection in adolescent idiopathic scoliosis (AIS)

STUDY DESIGN

Retrospective case-control.

OBJECTIVE

To identify a cohort of patients with persistent coronal imbalance (CIB) or revision surgery 5 years following fusion to an L3 lowest-instrumented-vertebra (LIV) and determine factors that make an L3 LIV high-risk. In surgical planning for AIS, L3 is chosen over L4 whenever possible to maximize motion segments below the LIV. Though fusion to an L3 LIV is common, the rate of failure and its risk factors have not been described.

METHODS

In this analysis of prospectively-collected multi-center data of AIS patients who underwent posterior spinal fusion (PSF) to an L3 LIV, we identified patients with CIB at 5 years and/or those who required revision surgery attributable to LIV selection. Patients who were balanced at 5 years and did not require revision surgery served as controls. Pre-operative patient and radiographic variables were compared between cases and controls to identify risk factors for CIB/revision surgery.

RESULTS

We identified 646 patients with 2-year follow-up and 225 patients with 5-year follow-up, of which 11 were found to have CIB and/or revision surgery attributable to selecting L3 as the LIV. There were statistically significant differences between cases and controls with respect to several pre-operative factors, including BMI (24.5 in cases vs. 20.1 in controls; p = 0.01), Lenke curve type (81.8% Lenke 5/6 vs. 44.4%; p = 0.03), lumbar curve magnitude (56 vs. 45°; p < 0.01), TL/L apical vertebral translation (AVT) (6.2 vs. 4.1 cm; p < 0.01), L3 angulation (30° vs. 22°; p < 0.01), L3 translation (4.3 vs. 2.9 cm; p < 0.01), thoracic rib hump (7° vs. 12°; p = 0.02), lumbar rib hump (16° vs. 10°; p < 0.01), and thoracolumbar (T10-L2) kyphosis (10.5° vs. 2°; p = 0.006). Multivariate logistic regression showed that pre-operative BMI, TL/L AVT, L3 angulation, L3 translation, lumbar rib hump, and thoracolumbar kyphosis were independent predictors of CIB/revision surgery.

CONCLUSIONS

An L3 LIV is frequently successful at 5 years post-operatively. Consider an L4 LIV when: pre-operative BMI ≥ 28, L3 angulation ≥ 25°, L3 translation ≥ 4 cm, TL/L AVT ≥ 6 cm, or the lumbar curve is large (≥ 55°) and rotated (≥ 10°).

LEVEL OF EVIDENCE

Level III.

Is the Combination of Convex Compression for the Proximal Thoracic Curve and Concave Distraction for the Main Thoracic Curve Using Separate-rod Derotation Effective for Correcting Shoulder Balance and Thoracic Kyphosis?

BACKGROUND

Posterior correction of the proximal thoracic curve in patients with adolescent idiopathic scoliosis has been recommended to achieve shoulder balance. However, finding a good surgical method is challenging because of the small pedicle diameters on the concave side of the proximal thoracic curve. If the shoulder height can be corrected using screws on the convex side, this would appear to be a more feasible approach.

QUESTIONS/PURPOSES

In patients with adolescent idiopathic scoliosis, we asked: (1) Is convex compression with separate-rod derotation effective for correcting the proximal thoracic curve, shoulder balance, and thoracic kyphosis? (2) Which vertebrum is most appropriate to serve as the uppermost-instrumented vertebra? (3) Is correction of the proximal thoracic curve related to the postoperative shoulder balance?

METHODS

Between 2015 and 2017, we treated 672 patients with scoliosis. Of those, we considered patients with elevated left shoulder, Lenke Type 2 or 4, or King Type V idiopathic scoliosis as potentially eligible. Based on that, 17% (111 of 672) were eligible; 5% (6 of 111) were excluded because of other previous operations and left-side main thoracic curve, 22% (24 of 111) were excluded because they did not undergo surgery for the proximal thoracic curve with only pedicle screws, 21% (23 of 111) were excluded because the proximal thoracic curve was not corrected by convex compression and separate rod derotation, and another 3% (3 of 111) were lost before the minimum study follow-up of 2 years, leaving 50% (55 of 111) for analysis. During the study period, we generally chose T2 as the uppermost level instrumented when the apex was above T4, or T3 when the apex was T5. Apart from the uppermost-instrumented level, the groups did not differ in measurable ways such as age, sex, Cobb angles of proximal and main thoracic curves, and T1 tilt. However, shoulder balance was better in the T3 group preoperatively. The median (range) age at the time of surgery was 15 years (12 to 19 years). The median follow-up duration was 26 months (24 to 52 months). Whole-spine standing posteroanterior and lateral views were used to evaluate the improvement of radiologic parameters at the most recent follow-up and to compare the radiologic parameters between the uppermost-instrumented T2 (37 patients) and T3 (18 patients) vertebra groups. Finally, we analyzed radiologic factors related to shoulder balance, defined as the difference between the horizontal lines passing both superolateral tips of the clavicles (right-shoulder-up was positive), at the most recent follow-up.

RESULTS

Convex compression with separate-rod derotation effectively corrected the proximal thoracic curve (41° ± 11° versus 17° ± 10°, mean difference 25° [95% CI 22° to 27°]; p < 0.001), and the most recent shoulder balance changed to right-shoulder-down compared with preoperative right-shoulder-up (8 ± 11 mm versus -8 ± 10 mm, mean difference 16 mm [95% CI 12 to 19]; p < 0.001). Proximal thoracic kyphosis decreased (13° ± 7° versus 11° ± 6°, mean difference 2° [95% CI 0° to 3°]; p = 0.02), while mid-thoracic kyphosis increased (12° ± 8° versus 18° ± 6°, mean difference -7° [95% CI -9° to -4°]; p < 0.001). Preoperative radiographic parameters did not differ between the groups, except for shoulder balance, which tended to be more right-shoulder-up in the T2 group (11 ± 10 mm versus 1 ± 11 mm, mean difference 10 mm [95% CI 4 to 16]; p = 0.002). At the most recent follow-up, the correction proportion of the proximal thoracic curve was better in the T2 group than the T3 group (67% ± 10% versus 49% ± 22%, mean difference 19% [95% CI 8% to 30%]; p < 0.001). In the T2 group, T1 tilt (6° ± 4° versus 6° ± 4°, mean difference 1° [95% CI 0° to 2°]; p = 0.045) and shoulder balance (-14 ± 11 mm versus -7 ± 9 mm, mean difference -7 mm [95% CI -11 to -3]; p = 0.002) at the most recent follow-up improved compared with those at the first erect radiograph. The most recent shoulder balance was correlated with the correction proportion of the proximal thoracic curve (r = 0.29 [95% CI 0.02 to 0.34]; p = 0.03) and change in T1 tilt (r = 0.35 [95% CI 0.20 to 1.31]; p = 0.009).

CONCLUSION

Using the combination of convex compression and concave distraction with separate-rod derotation is an effective method to correct proximal and main thoracic curves, with reliable achievement of postoperative thoracic kyphosis and shoulder balance. T2 was a more appropriate uppermost-instrumented vertebra than T3, providing better correction of the proximal thoracic curve and T1 tilt. Additionally, spontaneous improvement in T1 tilt and shoulder balance is expected with upper-instrumented T2 vertebrae. Preoperatively, surgeons should evaluate shoulder balance because right-shoulder-down can occur after surgery in patients with a proximal thoracic curve.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Transient fixation of L4 vertebra preserves lumbar motion and function in Lenke Type 5C and 6C scoliosis

This study investigated the efficacy of a novel surgical method that relies on the transient fixation of L4 in Lenke Type 5C and 6C adolescent idiopathic scoliosis. Thirty-six transient surgically treated L4 fixation patients were retrospectively evaluated. The first surgery involved mechanical correction of scoliosis; the lowest instrumented vertebra (LIV) was L4. After an average of 1.3 years (range, 0.3-3.4), the second surgery to remove transient L4 pedicle screws was performed. Radiographic parameters and SRS-22 scores were measured. Cobb's angle, coronal balance, LIV tilting angle, and LIV coronal disc angle clearly improved after the first surgery (p < 0.01). After the second surgery, the corrected Cobb angle (p = 0.446) and coronal balance were maintained (p = 0.271). Although L3/S1 lumbar lordosis decreased after the first surgery (p < 0.01), after removal of transient L4 pedicle screws, it recovered slightly (p = 0.03). Similarly, the preoperative L3/4 lateral disc mobility eventually recovered after transient L4 screw removal (p < 0.01). The function domain of the SRS-22 showed better scores after removal of transient L4 screws (p = 0.04). L4 transient fixation surgery is beneficial for Lenke Type 5C and 6C scolioses that do not fully satisfy LIV (L3) criteria. It preserves L3/4 disc motion, increases functional outcomes, and maintains spinal correction and coronal balance.

Including the stable sagittal vertebra in the fusion for adolescent idiopathic scoliosis reduces the risk of distal junctional kyphosis in Lenke 1-3 B and C curves

PURPOSE

The selection of lowest instrumented vertebra (LIV) in adolescent idiopathic scoliosis (AIS) is determined by coronal and sagittal plane indicators. Failure to properly select the LIV can lead to suboptimal outcomes and the need for revision surgery. A subset of patients have discordant coronal last touched vertebra (cLTV) and stable sagittal vertebra (SSV) which complicates the choice of LIV. The purpose of this study is to report the incidence of discordant cLTV and SSV when choosing LIV and investigate the association between length of fusion and patient-reported outcomes (PROs) and distal junctional kyphosis (DJK).

METHODS

This retrospective multicenter cohort study included AIS patients with discordant pre-operative cLTV and SSV. Patients fused only to include the proximal cLTV were compared to patients fused to include the distal SSV. Primary outcomes included DJK and PROs measured by SRS-22.

RESULTS

Eight hundred and fifty-six patients were identified of which 114 (13.3%) had discordant SSV and cLTV. The DJK incidence was 7.7% and 45.5% in patients fused to include the SSV versus short of the SSV, respectively. Lenke Modifier type B and C patients with fusions short of the SSV had a 9.2 times increased risk of developing DJK at 2 years compared to patients with fusions including the SSV (95% CI 2.8, 29.7; p < 0.001). However, patients with fusions short of the SSV and no evidence of DJK were 9.2 times more likely to have improvement in the SRS-22 pain domain compared to patients with fusions including the distal SSV (95% CI 1.1, 77.4; p = 0.042) CONCLUSION: Patients fused short of the SSV are at significant risk for the development of DJK at 2 years post-operatively. However, patients with shorter fusions were more likely to have an improvement in their pain as measured by patient-reported outcomes than patients with longer fusions.

A bony Chance fracture through L1 following posterior spinal fusion for adolescent idiopathic scoliosis: a case report

STUDY DESIGN

Case report.

INTRODUCTION

Instrumented posterior fusion using pedicle screws has been the mainstay of the surgical correction of adolescent idiopathic scoliosis since it was popularised by Roy-Camille in the 1970s. The aim of this case report is to describe the occurrence and salvage of an L1 chance fracture occurring through the lower instrumented vertebra following pedicle screw placement for posterior spinal instrumented fusion in the treatment of adolescent idiopathic scoliosis (AIS).

CASE REPORT

A 15-year-old female patient underwent T2-L1 posterior instrumented fusion for a Lenke 1b deformity. The selection of fusion levels was made based upon standing and bending radiographs which showed a non-structural lumbar curve. Early recovery was uneventful. At 6 months post-operatively, the patient reported new deformity and pain. A chance fracture at L1 was diagnosed and subsequent extension of instrumentation to L3 was carried out. Final post-operative recovery was uneventful and the patient returned to an active lifestyle.

CONCLUSION

Several factors can contribute to the occurrence of a fracture through an instrumented pedicle. This case shows that there must be due consideration of the small pedicle at L1 when it is chosen as the LIV.

Spontaneous Improvement of Postoperative Coronal Imbalance Following Selective Thoracolumbar-Lumbar Fusion in Lenke 5C Adolescent Idiopathic Scoliosis

OBJECTIVE

To evaluate prevalence and prognosis of postoperative coronal imbalance (CIB) and factors related to its onset and spontaneous improvement in patients with Lenke 5C adolescent idiopathic scoliosis who underwent selective thoracolumbar-lumbar fusion.

METHODS

We measured radiographic parameters and evaluated clinical outcomes using the Scoliosis Research Society-22 questionnaire in patients with Lenke 5C adolescent idiopathic scoliosis and a minimum 2-year follow-up. CIB was defined as >2 cm distance between C7 plumb line and central sacral vertical line. We compared parameters between patients with CIB (CIB group) and without CIB (coronal balanced group).

RESULTS

Inclusion criteria were met by 29 patients (mean age at surgery:17.0 years; average follow-up period: 45.6 months). CIB was found in 10 patients 1 week after surgery (34.5%); this decreased to 6.9% at final follow-up. Comparative analysis indicated significant values as follows: age at surgery (17.5 years vs. 14.7 years, P = 0.005), lumbosacral curve (5.9° vs. 11.2°, P = 0.02), and L5 tilt (-3.6° vs. -8.1°, P = 0.02) in bending film. Greater changes of lowest instrumented vertebra disc angle, which means scoliotic angles between LIV and LIV+1, were significantly associated with spontaneous improvement of CIB (P = 0.04). Clinical outcomes were comparable between the coronal balanced and CIB groups.

CONCLUSIONS

Although CIB was frequently detected in the early postoperative period after selective thoracolumbar-lumbar fusion, it mostly corrected spontaneously. Relatively younger age at surgery and less flexible lumbosacral curve may be related to postoperative CIB, and greater changes of LIV disc angle may be associated with spontaneous improvement of CIB.

Variations in the Number of Thoracic and Lumbar Vertebrae in Patients With Adolescent Idiopathic Scoliosis: A Retrospective, Observational Study

BACKGROUND

Abnormal anatomy is a contributory factor to wrong-level surgery. Variations in the number of vertebrae in populations from different races and geographical regions have been described. A ∼10% prevalence of variations in number of thoracic and lumbar vertebrae in adolescent idiopathic scoliosis (AIS) patients has been previously reported. The objectives of present study were (i) to find out the prevalence of variations in the number of thoracic and lumbar vertebrae and the presence of lumbosacral transitional vertebrae (LSTV) in Indian AIS patients and (ii) to correlate these variations with gender and type of curve.

METHODS

Hospital records and imaging of 198 AIS patients were reviewed retrospectively. A standardized numbering strategy was used to identify the number of thoracic vertebrae, number of lumbar vertebrae, and presence of LSTV. Patients' gender and curve type were correlated with the presence of an abnormal number of thoracic or lumbar vertebrae. Radiology reports and operation notes were reviewed to find out instances when the radiologist or surgeon had identified an abnormal number of vertebrae.

RESULTS

Forty patients (20.2%) with abnormally numbered thoracic or lumbar vertebrae were identified. Twenty patients (10.1%) had abnormally numbered thoracic vertebrae, and 33 patients (16.7%) had abnormally numbered lumbar vertebrae. The prevalence of LSTV was 18.2%. Presence of variations did not correlate with gender or curve type. Radiology reports identified 2/40 patients with variations, whereas operation notes showed 4/40 patients had been correctly identified to have abnormally numbered vertebrae.

CONCLUSIONS

There is high prevalence of variation in the number of thoracic or lumbar vertebrae in AIS patients, with most of those missed being identified by radiologists or surgeons. The patient's preoperative imaging must be scrutinized to identify these patients and take the variation into account to avoid wrong selection of fusion levels.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

Text. The study raises awareness about possibility of wrong selection in fusion levels due to anatomical variations in surgery for AIS.

A Retrospective Study of Factors Associated with Restoration of Thoracic Kyphosis in 43 Patients with Adolescent Idiopathic Scoliosis with Lenke Type 1 Curvature

BACKGROUND This retrospective study aimed to identify the factors associated with successful surgical correction of thoracic kyphosis (TK) in 43 patients with adolescent idiopathic scoliosis (AIS) with Lenke type 1 curvature, in which the major curve with the largest Cobb angle was mainly in the thoracic region. MATERIAL AND METHODS We collected data from patients with Lenke 1 AIS. The following parameters were measured: Cobb angle, side-bending Cobb angle, cervical lordosis (CL), TK, lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), the sagittal vertical axis (SVA), the center of a C7 plumb line to the center sacral vertical line (C7-CSVL), correction rate, Ponte osteotomy, flexibility, and screw density. Univariate analysis and multivariate logistic regression analyses were performed. RESULTS Among the 43 cases analyzed, the mean postoperative Cobb angle at the last follow-up, C7-CSVL, SVA, CL, TK, LL, PI, SS, and PT were respectively 21.33±9.47°, 10.41±8.45 mm, 19.68±14.33 mm, 16.19±7.45°, 23.12±7.45°, 50.33±11.37°, 49.70±9.83°, 39.42±8.11°, and 10.16±6.63°. Univariate analysis suggested that preoperative TK, preoperative LL, and Ponte osteotomy were statistically significant (P<0.05), and multivariate analysis suggested that preoperative LL and Ponte osteotomy were statistically significant (P<0.05). CONCLUSIONS The results of this study demonstrated that preoperative TK, preoperative LL, and Ponte osteotomy were related factors for maintaining normal TK. Multivariate analysis suggested that preoperative LL and the use of Ponte osteotomy with full-thickness segmental resection of the spinal posterior column resulted in the successful surgical correction of TK in patients with AIS with Lenke type 1 curvature.

Extreme long-term outcome of operatively versus conservatively treated patients with adolescent idiopathic scoliosis

PURPOSE

We report on outcomes of surgically versus (vs) non-surgically treated patients with moderate adolescent idiopathic scoliosis (AIS) after minimum of 29 years.

METHODS

AIS patients with a follow-up of  ≥ 41 years in the surgical group and  ≥ 29 years in the non-surgical group were included. Patients were treated surgically for primary curves  ≥ 45° vs non-surgically for curves  < 45° or refusal of surgery. Groups were matched for age, gender, comorbidities and primary curve severity. Oswestry Disability Index (ODI) was used to measure clinical outcomes and standard radiography to quantify curve severity at final follow-up.

RESULTS

In total, 16 patients (8 within each group, 75% females) with a median age of 14 (interquartile range (IQR) 2) years could be included and were followed up after 46 (IQR 12) years. All matched variables were similar for both groups, including the primary curve Cobb angles of 48° (IQR 17°) (surgical) vs 40° (IQR 19°) (non-surgical); p = 0.17). At final follow-up after a median of 47 (IQR 5) years for the surgical and 39 (IQR 19) years for the non-surgical group (p = 0.43), the ODI was similar for both groups (15 (IQR 13) points (surgical) vs 7 (IQR 15) points (non-surgical); p = 0.17) with, however, a primary curve magnitude lower in the surgical compared to the non-surgical group (38° (IQR 3°) vs 61° (IQR 33°); p = 0.01), respectively.

CONCLUSION

After around 47 and 39 years, respectively, surgical and non-surgical treatment of moderate AIS showed similar subjective outcomes, but with a relevant smaller curve magnitude with surgical treatment.

LEVEL OF EVIDENCE

III.

The Benefits of Sparing Lumbar Motion Segments in Spinal Fusion for Adolescent Idiopathic Scoliosis Are Evident at 10 Years Postoperatively

STUDY DESIGN

A prospective multicenter study.

OBJECTIVE

To evaluate the effects of sparing lumbar motion segments on spinal mobility and Scoliosis Research Society-22 scores at 10 years after spinal fusion for major thoracic adolescent idiopathic scoliosis (AIS).

SUMMARY OF BACKGROUND DATA

In surgical correction for major thoracic AIS, the long-term benefits of sparing lumbar motion segments remain unclear.

METHODS

A prospective multicenter registry was reviewed and patients with major thoracic AIS (Lenke types 1-4) and availability of both preoperative and 10-year postoperative mobility data were included. Spinal fusions ending at L1 or above were defined as thoracic fusions (T), and at L2 or below as thoracic and lumber fusions (T + L). Spinal mobility was evaluated with a measuring tape. The excursions between the starting and ending positions were measured using the distance from the spinous processes of C7 to S1 for forward flexion (FF), and the distance from the tip of the middle finger to the floor for lateral flexion (LF). Substantial reduction of mobility was defined as a reduction rate (a ratio of postoperative change divided by preoperative mobility) of 40% or more. Motion data were correlated with lowest instrumented vertebra levels and group comparisons were performed.

RESULTS

We identified 151 patients (average age, 25.1 years). The spinal mobility decreased with more distal lowest instrumented vertebrae (FF, rho = 0.208; right LF, 0.257; left LF, 0.371; P ≤ 0.01). Consequently, the incidence of substantial reduction of mobility was lower in the T group (n = 109) than in the T + L group (n = 42) (FF: 17.4% vs. 50%, LF: 14.8% vs. 51.2%; P < 0.001). Patients with substantial reduction in LF had lower Scoliosis Research Society-22 scores for pain, function, satisfaction, and total scores than those without substantial reduction at 10-year follow-up (P < 0.05).

CONCLUSION

The sparing of lumbar motion segments demonstrated clinically significant benefits at 10-year postoperatively.

LEVEL OF EVIDENCE

2.

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

HYPOTHESIS

Fusing shorter than the last touched vertebra (LTV) is a safe approach in flexible main thoracic (MT) adolescent idiopathic scoliosis (AIS) curves.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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.

Posterior Correction of Adolescent Idiopathic Scoliosis with High-Density Pedicle Screw-Only Constructs: 5 Years of Follow-Up

PURPOSE

This study aimed to analyze radiological outcomes in patients with adolescent idiopathic scoliosis (AIS) who underwent posterior correction with high-density pedicle screw-only constructs. We hypothesized that high-density pedicle screw-only constructs in AIS would provide a high correction rate and would facilitate the maintenance of the correction or obviate the loss thereof.

MATERIALS AND METHODS

We retrospectively analyzed radiological outcomes over a minimum follow-up period of 5 years in patients with AIS who underwent posterior correction with high-density pedicle screw-only constructs. A total of 124 consecutive patients were included. Demographic data, including age, sex, operated fusion level, numbers of screw, Lenke curve type, Risser stage, and follow-up period were retrospectively collected from electronic medical records and radiological measurements including serial follow-up.

RESULTS

The average number of pedicle screws was 1.96/vertebra. The average curve correction was 48.3% for the proximal thoracic (PT) curve, 83.1% for the main thoracic (MT) curve, and 80.2% for the thoracolumbar/lumbar (TL/L) curve at final follow-up. Use of high-density pedicle screw-only constructs helped achieve excellent correction rates, with no significant loss of correction at final follow-up.

CONCLUSION

We obtained excellent correction rates of 48.3% for PT, 83.1% for MT, and 80.2% for TL/L curves using high-density pedicle screw-only constructs in AIS, with no significant loss of correction at final follow-up.

Disc Wedge and Vertebral Body Tilt Angle Below Lower Instrumented Vertebra After Posterior Correction and Fusion in Patients With a Structural Thoracolumbar/Lumbar Curve: A Minimum 5-Year Follow-up

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The purpose of this study was to evaluate the stability of remained lumbar curve by the review of serial changes in L3/L4 disc wedge and L4 body tilt angle in patients with idiopathic scoliosis who underwent posterior-only fusion to L3 lower instrumented vertebra (LIV) for the correction of structural thoracolumbar/lumbar (TL/L) curve for a minimum 5-year follow-up.

SUMMARY OF BACKGROUND DATA

There has been some debate in the selection of L3 or L4 as the LIV for the correction of structural TL/L curve. However, there is a limited information about the changes in disc wedge or vertebral body tilt angles below the L3 LIV.

METHODS

Forty-seven patients were included (mean age 16 yr 7 mo, follow-up 8 yr 2 mo). The Cobb angle of the TL/L curve, L3/L4 disc wedge angle, L4 tilt angle, trunk shift (TS), and apical vertebral translation (AVT) were compared preoperatively and at postoperative 5 days, 1 month, 6 months, 2 years, and final follow-up.

RESULTS

At postoperative 5 days, Cobb angle of the TL/L curve, L4 tilt angle, and AVT were improved, except TS and L3/L4 disc wedge angle. The L3/L4 disc wedge and L4 tilt angle were most increased at postoperative 6 months and decreased thereafter. L4 tilt angle, AVT, and TS were improved during postoperative follow-up, except L3/L4 disc wedge angle. Finally, Cobb angle of the TL/L curve (11.8° ± 5.1°, P < 0.001), L4 tilt angle (7.6° ± 4.0°, P < 0.001), AVT (19.2 ± 9.3 mm, P < 0.001), and TS (-5.0 ± 10.0 mm, P = 0.041) were improved; however, L3/L4 disc wedge angle (3.3° ± 2.3°, P = 0.442) was not improved compared to the preoperative evaluation.

CONCLUSION

When LIV was selected as the L3, the correction of TL/L curve was maintained in a minimum 5-year follow-up with the improvement of L4 tilt angle, AVT, and TS; however, L3/L4 disc wedge angle may remain.

LEVEL OF EVIDENCE

3.

The Importance of the Pedicle Diameters at the Proximal Thoracic Vertebrae for the Correction of Proximal Thoracic Curve in Asian Patients With Idiopathic Scoliosis

STUDY DESIGN

A retrospective comparative radiographic study.

OBJECTIVE

The purpose of this study was to evaluate differences in the pedicle diameters of proximal thoracic vertebrae in relation to the severity of the proximal thoracic curve in Asian patients with idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

A small pedicle diameter at the proximal thoracic vertebra has been reported in normal population, but the changes of pedicle diameter in patients with a proximal thoracic curve have not been properly evaluated.

METHODS

One hundred eighty-two patients with adolescent idiopathic scoliosis involving a greater than 10-degree proximal thoracic curve were analyzed. Sixty-nine and 113 patients had a structural and nonstructural proximal thoracic curve, respectively. The pedicle width was evaluated from T1 to T4 using a reconstructed computed tomography (CT) scan. The pedicle widths were compared between the convex and concave side, and between the structural and nonstructural proximal thoracic curve groups.

RESULTS

The pedicle widths at T3 (0.76 ± 0.92 mm) and T4 (0.50 ± 0.69 mm) on the concave side for the structural proximal thoracic curves were extremely narrow compared with those for the nonstructural proximal thoracic curves (T3,1.17 ± 0.84 mm; T4,0.82 ± 0.72 mm) (P = 0.002, 0.003, respectively). However, the T2 pedicle width was comparable on the concave side in both groups (2.44 ± 0.94 mm for the nonstructural and 2.32 ± 0.97 mm for the structural proximal thoracic curve, P = 0.430).

CONCLUSION

A pedicle screw insertion at the T3 or T4 vertebra on the concave side is not always possible in cases of a structural proximal thoracic curve; however, the pedicle width of the T2 vertebra is very wide and safe for the standard pedicle screw insertion. These results should be considered when the surgeon decides the upper instrumented vertebra or the correction method for the structural proximal thoracic curve.

LEVEL OF EVIDENCE

3.

Theory of Bowstring Disease: Diagnosis and Treatment Bowstring Disease

Bowstring disease (BSD) is a new classification of spine disease caused by axial stretched lesion on nerve roots and the spinal cord, which is differentiated from disc herniation and canal stenosis in that it is caused by nerve compression lesions. BSD could be caused by mismatched growth rates between the spine and nerve roots (the juvenile type), or by imbalanced degenerative rates between the spine column and nerve roots (degenerative type). Here, we propose that there are several self-adjust mechanisms to relieve axial nerve tension: (i) nerve growth; (ii) posture adjustment and low back pain; (iii) autogenous degeneration of intervertebral disc; and (iv) idiopathic and degenerative scoliosis. Iatrogenic lesions could also result in BSD, which could be presented as adjacent segment degeneration, leading to adding-on effects and other neurological symptoms. The diagnosis criteria are proposed based on symptoms, physical examination, and radiological presentations. To remove axial tension on nerve roots, lumbar surgery should aim to restore the coordination of spine and cord units. Capsule surgery, shortening the spine column, could decompress cord and nerve roots 3-dimensionally.

Postoperative Lumbar Curve Progression Deteriorates Shoulder Imbalance in Patients with Lenke Type 2B/C Adolescent Idiopathic Scoliosis Who Underwent Selective Thoracic Fusion

OBJECTIVE

To evaluate the association between postoperative lumbar curve progression and the shoulder height in patients with Lenke type 2B/C adolescent idiopathic scoliosis (AIS).

METHODS

A total of 25 patients with Lenke type 2B/C AIS underwent posterior correction surgery in our institution from 2005-2014 were included. Standing x-ray films of the whole spine obtained before surgery, immediately after surgery, and at the last follow-up were analyzed with respect to the following parameters: proximal thoracic Cobb angle, main thoracic (MT) Cobb angle, lumbar Cobb angle, lumbar apical vertebral translation, distance between C7 plumb line and the central sacral vertical line, and radiographic shoulder height (RSH). Correlations between the change of RSH and the changes of other parameters were analyzed both immediately after surgery and at the last follow-up.

RESULTS

The change of RSH was significantly negatively correlated with both the change of MT Cobb angle (P < 0.05) and that of lumbar Cobb angle (P < 0.05) immediately after surgery, whereas the interval-time change of RSH was significantly positively correlated with the interval-time change of lumbar Cobb angle (P < 0.05) and that of lumbar apical vertebral translation (P < 0.05) at the last follow-up. The change of MT Cobb angle was an independent predictor for the change of RSH immediately after surgery, whereas the interval-time change of lumbar Cobb angle was an independent predictor for the interval-time change of RSH at the last follow-up.

CONCLUSIONS

Postoperative lumbar curve progression is a risk factor for deterioration of shoulder imbalance in patients with Lenke 2B/C AIS during the follow-up period.

[Effectiveness analysis of Lenke type 1 adolescent idiopathic scoliosis with different proximal fixation vertebra]

Objective

To investigate the short-term effectiveness of proximal fixation of one vertebra above to the upper end vertebra and the upper end vertebra in the treatment of Lenke type 1 adolescent idiopathic scoliosis (AIS) patients with preoperative right higher shoulder.

Methods

The clinical data of 37 Lenke type 1 AIS patients treated with posterior correction between January 2010 and December 2015 were retrospectively analysed. According to proximal fixation vertebra, the patients were divided into 2 groups: group A ( n=17), proximal fixation of one vertebra above to the upper end vertebra; group B ( n=20), proximal fixation of the upper end vertebra. There was no significant difference in gender, age, Risser stage, radiographic shoulder height (RSH), flexibility of proximal thoracic curve, flexibility of main thoracic curve, flexibility of thoracolumbar/lumbar curve between 2 groups ( P>0.05). The main thoracic curve Cobb angle, proximal thoracic curve Cobb angle, thoracolumbar/lumbar curve Cobb angle, apical vertebral translation (AVT), clavicle angle (CA), RSH, coronal trunk shift, sagittal trunk shift, thoracic kyphosis (TK), and lumbar lordosis (LL) were measured by X-ray film before operation, and at 1 month, 1 year, and 2 years after operation. The correction indexes of main thoracic curve were evaluated, including the correction degree and correction rate of main thoracic curve and AVT correction at 1 month after operation, the loss degree and the loss rate of the correction of main thoracic curve at 2 years after operation.

Results

The operation time and intraoperation blood loss in group A were significantly greater than those in group B ( P<0.05). All the patients were followed up, and the follow-up time was 2-4 years (mean, 2.8 years) in group A and 2-3.5 years (mean, 2.6 years) in group B. No serious complication such as nerve damage occurred during perioperative period and follow-up period. No complication such as failure of fusion, loosening and rupture of internal fixator, adjacent segment degeneration, and proximal junctional kyphosis occurred. There was no significant difference between 2 groups in the correction degree and correction rate of main thoracic curve and AVT correction at 1 month after operation, the loss degree and the loss rate of the correction of main thoracic curve at 2 years after operation ( P>0.05). Comparison within the two groups: except for LL had no significant difference between pre- and post-operation ( P>0.05), the other indicators were significantly improved after operation ( P<0.05) in the two groups. There were significant differences in RSH, CA, proximal thoracic curve Cobb angle, and thoracolumbar/lumbar curve Cobb angle at each time point after operation ( P<0.05), and there were spontaneous correction during follow-up; however, there was no significant difference in main thoracic curve Cobb angle, AVT, TK, LL, trunk shift at each time point after operation ( P>0.05), and there was no significant loss during follow-up. Comparison between the two groups: there was no significant difference in all the radiographic indexes at pre- and post-operation ( P>0.05).

Conclusion

For Lenke type 1 AIS patients with preoperative right high shoulder, proximal fixation vertebra be fixed to the upper end vertebral can obtain satisfactory short-term orthopedic effectiveness and reduce blood loss and operation time.

Coronal Imbalance after Selective Posterior Thoracic Fusion in Patients with Lenke 1 and 2 Adolescent Idiopathic Scoliosis

Coronal decompensation is a common complication in Lenke 1 or 2 AIS patients after selective thoracic fusion (STF). However, the majority who developed immediately postoperative coronal decompensation experienced improvement and the related factors are not fully understood. The aim of this retrospective study was to investigate the prevalence of coronal imbalance in patients with Lenke 1 or 2 AIS and to explore radiological factors associated with spontaneous correction of coronal balance after surgery. Lenke 1 or 2 AIS patients receiving STF in our center from January 2013 to March 2015 were analyzed. Anteroposterior and lateral films were evaluated before surgery, at 1 month's and 2 years' follow-up. Patients were divided into 2 groups according to whether coronal imbalance occurred in the early postoperative period (1 month). Various radiological parameters as well as Scoliosis Research Society-22 were statistically compared between groups. Coronal decompensation was observed in 33 patients preoperatively, in 48 patients immediately postoperatively, and in 2 patients at final follow-up. Lowermost instrumented vertebra (LIV) disc angle (0.9° vs. 6.7°, p=0.019) and LIV- C7 plumb line and central sacral vertical line (CSVL) (-3.4mm vs. -13.7mm, p=0.020) increased in the final follow-up in the imbalanced group of type A modifier. The magnitude of lumbar curve was greater in the imbalanced group of type B or C modifier in the early postoperative period (19.5° vs. 12.6°, p=0.006; 25.5° vs. 13.7°, p<0.01), and this difference disappeared in the final follow-up. No differences in SRS-22 outcome scores were noted between groups in different time. Coronal imbalance was frequently detected immediately after STF in Lenke 1 or 2 AIS patients, with type C modifier slightly higher than A or B. Distal adding-on may help compensate for coronal imbalance in patients with type A modifier, while spontaneous correction of lumbar curve attributes to the improvement of coronal imbalance in patients with type B or C modifier.

Spontaneous correction of coronal imbalance after selective thoracolumbar-lumbar fusion in patients with Lenke-5C adolescent idiopathic scoliosis

BACKGROUND CONTEXT

Coronal imbalance is a complication of corrective surgeries in adolescent idiopathic scoliosis (AIS). However, few studies about immediate coronal decompensation in Lenke-5C curves have reported its incidence, prognosis, and related factors.

PURPOSE

To evaluate the development of coronal imbalance after selective thoracolumbar-lumbar (TL/L) fusion (SLF) in Lenke-5C AIS, and to reveal related factors.

STUDY DESIGN

Retrospective comparative study.

PATIENT SAMPLE

This study included 50 consecutive patients with Lenke-5C AIS who underwent SLF at a single center.

OUTCOME MEASURES

Whole-spine anteroposterior and lateral radiographs were used to measure radiological parameters.

METHODS

Patients were divided into two groups according to the presence or absence of coronal imbalance (distance between C7 plumb line and central sacral vertical line >2 cm) in the early (1 month) postoperative period. Various radiological parameters were statistically compared between groups.

RESULTS

Of the patients, 28% (14 of 50) showed coronal imbalance in the early postoperative period; however, most of them (13 of 14) showed spontaneous correction during follow-up. The development of coronal imbalance was related to less flexibility of the TL/L curve (51.3% vs. 52.6%, p=.040), greater T10-L2 kyphosis (11.7° vs. 6.4°, p=.034), and greater distal junctional angle (6.0° vs. 3.7°, p=.025) in preoperative radiographs. Lowermost instrumented vertebra (LIV) tilt was greater in the decompensation [+] group in the early postoperative period (8.8° vs. 4.4°, p=.009). However, this difference disappeared in final follow-up with the decrease of LIV tilt in the decompensation [+] group.

CONCLUSIONS

Less flexibility of the TL/L curve, greater TL kyphosis, and greater distal junctional angle preoperatively were predictive factors for immediate coronal imbalance in Lenke-5C curves. Although coronal imbalance was frequently detected in the early postoperative period after SLF, it was mostly corrected spontaneously with a decrease of LIV tilt. Thus, SLF for Lenke-5C curves can be a good option regardless of the possible coronal imbalance in the early postoperative period.

A retrospective controlled clinical study of Cobb angle distribution of the main thoracic curve in adolescent idiopathic scoliosis

To compare the characteristics of Cobb angle distribution of the main thoracic curve (MTC) in patients with Lenke 1 adolescent idiopathic scoliosis (AIS) and differences in fulcrum-bending flexibility, correction rate, and correction index between different segments.Included in this study were 40 consecutive patients with Lenke 1 AIS who received posterior correction and fusion with pedicle screws. Cobb angle based on the proximal (T5-T7 or T6-T8), apical (T7-T9 or T8-T10), and distal (T9-T11 or T10-T12) segments in the fulcrum-bending position was measured before and after surgery. The flexibility ([Cobb angle of each segment - residual Cobb angle on fulcrum bending]/Cobb angle of each segment × 100%), correction rate ([Cobb angle of each segment - postoperative residual Cobb angle]/Cobb angle of each segment × 100%]), and correction index (correction rate of each segment/preoperative flexibility of each segment) in different segments were calculated. Comparative analyses were conducted by variance analysis.The mean age before surgery, Cobb angle, Risser sign, and follow-up time were 14.15 ± 2.13 years, 51.17 ± 10.72°, 2.78 ± 1.73, and 43.75 ± 9.82 months, respectively. MTC Cobb angle of the proximal segments was similar to that of the distal ones (12.88 ± 4.81 vs 12.85 ± 5.00) versus 25.45 ± 5.90 in the middle segments (P < .001). The flexibility was higher in the distal segments than that in the proximal or apical segments (66.43 ± 0.22% vs 43.78 ± 0.20% or 32.55 ± 0.17%, P < .001). One week after surgery, the correction rate in these 3 segments was 69.55 ± 0.1%, 66.25 ± 0.17%, and 75.28 ± 0.16 (P = .067), and the correction index was 2.15 ± 1.78, 3.16 ± 3.60, and 1.53 ± 1.93 (P = .019); the correction rate during the 3-year follow-up period was 68.06 ± 0.19%, 69.98 ± 0.15%, and 73.29 ± 0.17 (P = .212); and the correction index was 2.12 ± 1.78, 3.20 ± 3.54, and 1.49 ± 1.93 (P = .012), respectively.The proximal, apical, and distal segments in Lenke 1 AIS accounted for about 25%, 50%, and 25% of MTC Cobb angle, respectively. The distal segments were found to be most flexible and the apical segments most rigid. The correction rate was similar between the proximal, apical, and distal segments, and the correction index in the apical segments was higher than that in the proximal and distal segments.

Current concepts in the surgical management of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a complex 3D deformity of the spine. Its prevalence is between 2% and 3% in the general population, with almost 10% of patients requiring some form of treatment and up to 0.1% undergoing surgery. The cosmetic aspect of the deformity is the biggest concern to the patient and is often accompanied by psychosocial distress. In addition, severe curves can cause cardiopulmonary distress. With proven benefits from surgery, the aims of treatment are to improve the cosmetic and functional outcomes. Obtaining correction in the coronal plane is not the only important endpoint anymore. With better understanding of spinal biomechanics and the long-term effects of multiplanar imbalance, we now know that sagittal balance is equally, if not more, important. Better correction of deformities has also been facilitated by an improvement in the design of implants and a better understanding of metallurgy. Understanding the unique character of each deformity is important. In addition, using the most appropriate implant and applying all the principles of correction in a bespoke manner is important to achieve optimum correction.

In this article, we review the current concepts in AIS surgery.

Cite this article: Bone Joint J 2018;100-B:415–24.