Sagittal balance and idiopathic scoliosis: does final sagittal alignment influence outcomes, degeneration rate or failure rate?

Benefit-risks analysis of thoracoplasty in adolescent idiopathic scoliosis treated by sublaminar bands

INTRODUCTION

Cosmetic concerns are one of the main complaints of patients with adolescent idiopathic scoliosis (AIS). Several studies have shown a significant improvement in self-image scores after thoracoplasty. However, the effects of thoracoplasty on pulmonary function and clinical outcomes remain debated. The objective was to analyze the benefits and risks of thoracoplasty during AIS surgery using a hybrid construct with sublaminar bands.

MATERIAL AND METHODS

In this monocentric prospective cohort study, 68 patients with thoracic AIS were consecutively included between 2016 and 2017. All patients had low-dose 3D radiographs. Surgical correction was performed via the posterior approach, using the posteromedial translation technique with a hybrid construct (thoracic sublaminar band and lumbar pedicle screws). A thoracoplasty was proposed in cases of severe rib hump (more than 3cm). Pulmonary function was assessed by pulmonary function tests (PFT) with forced vital capacity, forced expiratory volume in 1 second and total lung capacity). Radiographic parameters and PFT were compared between patients who had or had not had a thoracoplasty preoperatively and 2 years postoperatively. The SRS-22 score was collected at follow-up.

RESULTS

The average age was 15±3 years. Nineteen patients (27%) had a thoracoplasty. The demographic, radiographic and respiratory data of the 2 groups were comparable preoperatively. The correction was similar between the groups on sagittal and coronal views. At 2 years, the PFTs were comparable to those performed preoperatively and no difference was found between the groups. None of the 12 patients who had a pleural effusion had it drained. The total SRS-22 score and the cosmetic subscore were higher in the thoracoplasty group (p<0.03).

DISCUSSION

The association of a thoracoplasty with AIS surgery improves the self-image of patients without altering the PFTs at 2 years postoperatively. Given the low morbidity of thoracoplasty, it seems reasonable to offer it to patients with severe rib hump and high cosmetic demands.

LEVEL OF EVIDENCE

III.

Costs of revision operations for distal junctional kyphosis following thoracic posterior spinal fusion for adolescent idiopathic scoliosis

PURPOSE

To assess direct costs and risks associated with revision operations for distal junctional kyphosis/failure (DJK) following thoracic posterior spinal instrumented fusions (TPSF) for adolescent idiopathic scoliosis (AIS).

METHODS

Children who underwent TPSF for AIS by a single surgeon (2014-2020) were reviewed. Inclusion criteria were minimum follow-up of 2 years, thoracolumbar posterior instrumented fusion with a lower instrumented vertebra (LIV) cranial to L2. Patients who developed DJK requiring revision operations were identified and compared with those who did not develop DJK.

RESULTS

Seventy-nine children were included for analysis. Of these, 6.3% developed DJK. Average time to revision was 20.8 ± 16.2 months. Comparing index operations, children who developed DJK had significantly greater BMIs, significantly lower thoracic kyphosis postoperatively, greater post-operative lumbar Cobb angles, and significantly more LIVs cranial to the sagittal stable vertebrae (SSV), despite having statistically similar pre-operative coronal and sagittal alignment parameters and operative details compared with non-DJK patients. Revision operations for DJK, when compared with index operations, involved significantly fewer levels, longer operative times, greater blood loss, and longer hospital lengths of stay. These factors resulted in significantly greater direct costs for revision operations for DJK ($76,883 v. $46,595; p < 0.01).

CONCLUSIONS

In this single-center experience, risk factors for development of DJK were greater BMI, lower post-operative thoracic kyphosis, and LIV cranial to SSV. As revision operations for DJK were significantly more costly than index operations, all efforts should be aimed at strategies to prevent DJK in the AIS population.

Sagittal Balance Parameters and Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis

Background: To review and evaluate multiple preoperative and postoperative sagittal parameters and their association with the risk of developing proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS) who undergo correction surgery. Methods: A systematic search was performed in December 2022 in PubMed, Embase and the Cochrane Library to retrieve all the studies relevant to our research. After the study selection and data extraction following PRISMA guidelines, RevMan 5.3 was used for statistical analysis. All the analyzed factors were evaluated by using odds ratios and weighted mean differences with 95% confidence intervals. Moreover, the meta-analysis of proportions via MedCalc was used for analyzing quantitative data from the studies. Results: A total of 22 studies were included in our meta-analysis. All the available values of sagittal parameters were evaluated. Among all the potential risk factors, higher preoperative thoracic kyphosis (Test for overall effect Z = 11.79, p < 0.00001), higher preoperative sagittal vertical axis (SVA) (test for overall effect Z = 11.19, p < 0.00001), greater thoracic kyphosis change post-op. compared to pre-op. (test for overall effect Z = 6.02, p < 0.00001), increased postoperative lumbar lordosis (test for overall effect Z = 3.65, p = 0.0003), higher post-op. SVA (test for overall effect Z = 24.93, p < 0.00001) and a larger pelvic incidence/lumbar lordosis (PI/LL) mismatch (test for overall effect Z = 20.50, p < 0.00001) were found to be the risk factors for PJK after AIS surgery. Moreover, a decreased rod contour angle (RCA) (test for overall effect Z = 3.79, p < 0.0002) and higher proximal junctional angle-rod contour angle (PJA-RCA) (test for overall effect Z = 39.18, p < 0.00001) play a significant role in the risk of developing PJK after AIS correction. Conclusions: Sagittal balance is of great importance when considering the surgical correction of AIS. Many factors in our meta-analysis were found to increase the incidence for PJK such as higher preoperative thoracic kyphosis and pre-op. SVA. Furthermore, increased thoracic kyphosis change, increased post-operative lumbar lordosis, SVA and PI/LL mismatch are also factors that influence the possibility of post-op. PJK. Lastly, RCA and PJA-RCA are two important factors that need attention during AIS, as over-contouring of the rod could lead to PJK in AIS patients.

Breaking the Rules in Three Dimensions: What to Expect After a Thoracic-only Fusion With Structural Thoracic and Thoracolumbar Curves

OBJECTIVE

Despite guidelines to fuse both thoracic and thoracolumbar/lumbar (TH/L) curves in patients with structural curves in both regions, a thoracic-only fusion allows preservation of lumbar motion segments. The purpose of this study was to assess the 2-year postoperative three-dimensional (3D) radiographic and clinical outcomes of patients with double or triple major (thoracic curves >TH/L curves) structural curves who underwent a thoracic-only fusion.

METHODS

A prospective adolescent idiopathic scoliosis registry was queried for double or triple major curves undergoing thoracic-only posterior fusion and a minimum 2-year follow-up. 3D reconstructions were generated from bi-planar radiographs. Paired sample t tests were used to assess differences in the coronal, sagittal, and axial planes pre and postoperatively, as well as Scoliosis Research Society Questionnaire-22 scores. Pearson correlations were utilized to identify variables related to spontaneous lumbar derotation.

RESULTS

Twenty-two patients met the inclusion criteria. Both thoracic [61 ± 10 degrees to 20 ± 9 degrees ( P < 0.001)] and lumbar curves [41 ± 7 degrees to 22±7 degrees ( P < 0.001)] had significant coronal improvement and T5 to T12 kyphosis improved from 7 ± 14 degrees to 23 ± 8 degrees ( P < 0.001). The thoracic apical translation was significantly improved postoperatively (4.7 ± 1.5 to 0.5 ± 1 cm, P < 0.001), but the lumbar apical translation was unchanged (-1.7 ± 0.6 to -1.7±0.8 cm, P = 0.94). Scoliosis Research Society Questionnaire-22 scores significantly improved by 2 years postoperative.

CONCLUSIONS

Unlike the 3D correction observed in nonstructural TH/L curves after thoracic-only fusion, patients with double or triple major curves demonstrated only spontaneous coronal correction of the lumbar curve, whereas the sagittal and axial planes were not significantly improved. These radiographic parameters did not negatively affect subjective or clinical outcomes at minimum 2-year follow-up.

LEVEL OF EVIDENCE

Level IV-therapeutic.

Is sagittal spinopelvic alignment a cause of low back pain in pediatric spine pathologies? A review

Purpose

Altered spinopelvic morphology is observed in many spine pathologies occurring during growth. The aim of the study is to better understand the sagittal compensatory mechanisms and their possible influence on the occurrence of pain in selected pediatric spine pathologies.

Methods

A bibliographic search in the PubMed database included articles published between September 1965 and July 2023. The keywords contained in the search were "spondylolysis," "spondylolisthesis," "scoliosis," "kypho," "sagittal," "pediatric," "child," "adolescent," "grow," "development," and "pain."

Results

The largest diversity in sagittal alignment patterns was reported in idiopathic scoliosis, with global flattening of the spine being the most common. Kyphotic deformations occurring during growth are characterized by structural thoracic or thoracolumbar kyphosis compensated by lumbar hyperlordosis and lower pelvic incidence. Whereas in spondylolisthesis, altered morphology of the spinopelvic junction with high values of pelvic incidence is observed. Pain does not seem to be related to sagittal alignment in idiopathic scoliosis. In Scheuermann disease, it is localized at the apex of the deformity and is associated with the curve pattern, whereas in spondylolisthesis, sagittal alignment correlates with pain scores only in high-grade slips.

Conclusion

Most of the patients with spine disorders that occurred during growth present a clinically balanced posture in the sagittal plane. It suggests that compensatory mechanisms before achieving skeletal maturity are really significant. A comprehension of sagittal alignment in spine deformities and its relationship to pain is essential for the proper assessment and treatment of these disorders.

Durability of stand-alone anterolateral interbody fusion in staged minimally invasive circumferential scoliosis surgery with delayed posterior instrumentation due to medical necessity

PURPOSE

Circumferential minimally invasive scoliosis surgeries are often staged, wherein anterior and/or lateral lumbar interbody fusion is followed by percutaneous posterior fixation days later. This study examines the impact on outcomes when posterior augmentation was delayed due to unexpected medical issues following the first stage, anterolateral procedure.

METHODS

A retrospective review was conducted of all patients undergoing minimally invasive circumferential deformity corrections from 2006 to 2019. Patients in whom planned posterior fixation was postponed due to medical necessity or safety concerns were identified. Perioperative surgical metrics and radiographic parameters were collected.

RESULTS

Three of the six patients initially scheduled for circumferential fusion never underwent posterior augmentation due to symptomatic improvement (2.3, 5, and 10.7 years of follow-up). The other three underwent posterior fixation once medically optimized after an average interval of 4.7 months (range 3.2-7.8 months) due to persistent symptoms. It was also observed that the average coronal malalignment in the postoperative period was 5.1 cm in the group requiring further fixation and only 1.6 cm in the group which did not.

CONCLUSION

In select cases, the indirect decompression and stability conferred by minimally invasive anterolateral arthrodesis alone may afford adequate pain relief to delay or even avoid posterior fixation in patients with adult spinal deformity.

No short-term clinical improvement and mean 6° of thoracic kyphosis correction using limited-level Ponte osteotomy near T7 for Lenke type 1 and 2 adolescent idiopathic scoliosis: a preliminary study

This study was a retrospective single surgeon case series approved by institutional review board and showed the efficacy of limited Ponte osteotomy at T6/7, 7/8 and 8/9 (limited-PO) in the sagittal plane for patients with Lenke type 1 and 2 adolescent idiopathic scoliosis (AIS). A total of 37 consecutive patients [7 males and 30 females; average age 16.0 ± 2.5 (range: 12-21)] over a 4-year period with posterior corrective fusion surgery were included. Initially, 18 patients were operated on without limited-PO [P(-)-group]. Midway in the series, the senior author switched to the limited-PO [P(+)-group]. The limited-PO has been performed to form the apex of thoracic kyphosis at the T7 level, together with the restoration of thoracic kyphosis. The mean amount of the correction angle of thoracic kyphosis was more in the P(+)-than in P(-)-group (13.8 ± 9.6° vs. 7.8 ± 8.0°, P  = 0.046) at 1-year after surgery. Cervical lordosis was spontaneously corrected more in P(+)-than in P(-)-group. The apex of thoracic kyphosis was controlled around the T7 level postoperatively in most cases (18/19 cases). There was no significant difference between the two groups in terms of blood loss and operative time per level, or Scoliosis Research Society-22 domain scores. Limited-PO contributed to the restoration of the whole spinal sagittal alignment for Lenke type 1 and 2 AIS; however, in this preliminary study, the clinical improvement was unclear at least in the short term, because the kyphosis angle obtained by limited-PO was only approximately 6°.

Rod Rotation with Outrigger Is Substantial for Correcting Apical Hypokyphosis in Patients with Adolescent Idiopathic Scoliosis: Novel Outrigger Device for Concave Rod Rotation

The apical hypokyphosis of scoliotic patients is thought to lead to decreased lung capacity and cause shortness of breath. Additionally, concave rod curve reduction is a problem in the correction of apical hypokyphosis in posterior spinal fusion surgery in adolescent idiopathic scoliosis (AIS). We investigated the contributions of rod rotation (RR) with an outrigger device, followed by differential rod contouring (DRC) with the outrigger attached to the concave rod, designed to prevent concave rod curve-flattening. We analyzed and compared the results of segmental pedicle screw fixation without the outrigger in 41 AIS patients with thoracic curves (Lenke type I, 25; type II, 16) to those corrected using the outrigger in 36 patients (Lenke type I, 24; type II,12). The changes in the Cobb angle, apical kyphosis of five vertebrae, thoracic kyphosis (TK, T4-12), correction rate, correction angle of apical vertebral rotation, spinal penetration index (SPi), and rib hump index (RHi) before and after surgery were measured, and the contribution of the outrigger was analyzed. The mean scoliosis correction rates without and with the outrigger were 72.1° and 75.6°, respectively (p = 0.03). Kyphosis of the five apical vertebrae and TK were significantly greater in the surgery with the outrigger (p = 0.002). Significantly greater improvements in SPi and RHi were also noted in the surgery with the outrigger (p < 0.05). The use of concave RR and convex DRC with the outrigger appear to be advantageous for correcting apical hypokyphosis, followed by the subsequent formation of TK. As a result, breathing problems are less likely to occur during daily life because of improvements in SPi and RHi.

Surgical treatment of double major adolescent idiopathic scoliosis can lead to excessive lumbar lordosis in the instrumented segments

PURPOSE

The purpose of this study was to characterize the sagittal spine in AIS patients with double major curves fused into the lumbar spine to determine the effects of posterior spinal fusion and instrumentation (PSFI) on global and segmental lumbar sagittal parameters.

METHODS

A consecutive series of AIS patients undergoing a PSFI from 2012 to 2017 having Lenke 3, 4 or 6 curves were analyzed. Sagittal parameters included pelvic incidence (PI), lumbar lordosis (LL), and segmental lordosis were measured. The difference in segmental lumbar lordosis between the preoperative, 6-week, and 2-year radiographs was analyzed and correlated to outcomes using SRS-30 patient questionnaires.

RESULTS

Seventy-seven patients had improvement in their coronal Cobb from 67.3 ± 11.8° to 25.43 ± 10.7° (66.4%) at 2 years. There was no change in thoracic kyphosis (23.0 ± 13.4° to 20.3 ± 7.8°) and pelvic incidence (49.9 ± 13.4° to 51.1 ± 15.7°) from preoperative to 2 years (p > 0.05) while lumbar lordosis increased from 57.6 ± 12.4° to 61.4° ± 12.3° (p = 0.002). Segmental lumbar analysis showed increased (+) lordosis at each instrumented level when comparing the preoperative and 2-year films for: T12-L1 (+ 3.24°, p < 0.001), L1-L2 (+ 5.70°, p < 0.001), and L2-L3 (+ 1.70°, p < 0.001). Loss (-) of lordosis was noted at every level below the LIV: L3-L4 (- 1.70°, p < 0.001), L4-L5 (- 3.52°, p < 0.001), L5-S1 (- 1.98°, p = 0.02). Preoperative LL of L4-S1 comprised 70 ± 16% of the global LL compared to 56 ± 12%, at 2 years (p < 0.001). Changes in sagittal measurements did not correlate with SRS outcome scores at two-year follow-up.

CONCLUSION

When performing PSFI for double major scoliosis, global SVA was maintained at 2 years, however, overall lumbar lordosis increased due to an increased lordosis in the instrumented segments and a smaller decrease in lordosis below the LIV. Surgeons should be wary of the tendency to create instrumented lumbar lordosis with a compensatory loss of lordosis below LIV which may be a set-up for poor long-term outcomes in adulthood.

Patient and surgical predictors of 3D correction in posterior spinal fusion: a systematic review

BACKGROUND

Restoration of three-dimensional (3D) alignment is critical in correcting patients with adolescent idiopathic scoliosis using posterior spinal fusion (PSF). However, current studies mostly rely on 2D radiographs, resulting in inaccurate assessment of surgical correction and underlying predictive factors. While 3D reconstruction of biplanar radiographs is a reliable and accurate tool for quantifying spinal deformity, no study has reviewed the current literature on its use in evaluating surgical prognosis.

PURPOSE

To summarize the current evidence on patient and surgical factors affecting sagittal alignment and curve correction after PSF based on 3D parameters derived from reconstruction of biplanar radiographs.

METHODS

A comprehensive search was conducted by three independent investigators on Medline, PubMed, Web of Science, and Cochrane Library to obtain all published information on predictors of postoperative alignment and correction after PSF. Search items included "adolescent idiopathic scoliosis," "stereoradiography," "three-dimensional," "surgical," and "correction." The inclusion and exclusion criteria were carefully defined to include clinical studies. Risk of bias was assessed with the Quality in Prognostic Studies tool, and level of evidence for each predictor was rated with the Grading of Recommendations, Assessment, Development, and Evaluations approach. 989 publications were identified, with 444 unique articles subjected to full-text screening. Ultimately, 41 articles were included.

RESULTS

Strong predictors of better curve correction included preoperative normokyphosis (TK > 15°), a corresponding rod contour, intraoperative vertebral rotation and translation, and upper and lower instrumented vertebrae selected based on sagittal and axial inflection points. For example, for Lenke 1 patients with junctional vertebrae above L1, fusion to NV-1 (1 level above the neutral vertebra) achieved optimal curve correction while preserving motion segments. Pre-op coronal Cobb angle and axial rotation, distal junctional kyphosis, pelvic incidence, sacral slope, and type of instrument were identified as predictors with moderate evidence. For Lenke 1C patients, > 50% LIV rotation was found to increase spontaneous lumbar curve correction. Pre-op thoracolumbar apical translation and lumbar lordosis, Ponte osteotomies, and rod material were found to be predictors with low evidence.

CONCLUSIONS

Rod contouring and UIV/LIV selection should be based on preoperative 3D TK in order to achieve normal postoperative alignment. Specifically, Lenke 1 patients with high-lying rotations should be fused distally at NV-1, while hypokyphotic patients with large lumbar curves and truncal shift should be fused at NV to improve lumbar alignment. Lenke 1C curves should be corrected using > 50% LIV rotation counterclockwise to the lumbar rotation. Further investigation should compare surgical correction between pedicle-screw and hybrid constructs using matched cohorts. DJK and overbending rods are potential predictors of postoperative alignment.

Apical Vertebras Distribution Modifier for Coronal Balance Classification in Adult Idiopathic Scoliosis

Background: We aimed to propose the apical vertebras distribution modifier to supplement the coronal balance (CB) classification for adult idiopathic scoliosis (AdIS). An algorithm to predict postoperative coronal compensation and avoid postoperative coronal imbalance (CIB) was proposed. Methods: Patients were categorized into CB and CIB groups according to the preoperative coronal balance distance (CBD). The apical vertebras distribution modifier was defined as negative (-) if the centers of the apical vertebras (CoAVs) were on either side of the central sacral vertical line (CSVL) and positive (+) if the CoAVs were on the same side of the CSVL. Results: A total of 80 AdIS patients, with an average age of 25.97 ± 9.20 years, who underwent posterior spinal fusion (PSF) were prospectively recruited. The mean Cobb angle of the main curve was 107.25 ± 21.11 degrees at preoperation. The mean follow-up time was 3.76 ± 1.38 (2-8) years. At postoperation and follow-up, CIB occurred in 7 (70%) and 4 (40%) CB- patients, 23 (50%) and 13 (28.26%) CB+ patients, 6 (60%) and 6 (60%) CIB- patients, and 9 (64.29%) and 10 (71.43%) CIB+ patients. Health-related quality of life (HRQoL) was significantly better in the CIB- group compared with that of the CIB+ group in the dimension of back pain. To avoid postoperative CIB, the correction rate of the main curve (CRMC) should match the compensatory curve for CB-/+ patients; the CRMC should be greater than the compensatory curve for CIB- patients; and the CRMC should be less than the compensatory curve for CIB+ patients, and the inclination of the LIV needs to be reduced. Conclusions: CB+ patients have the least postoperative CIB rate and the best coronal compensatory ability. CIB+ patients are at a high risk of postoperative CIB and have the poorest coronal compensatory capacity in the event of postoperative CIB. The proposed surgical algorithm facilitates the handling of each type of coronal alignment.

Cervical Sagittal Alignment and Balance Associated With Aging Chinese Adults: A Radiographic Analysis

STUDY DESIGN

This was a retrospective cohort radiographic study.

OBJECTIVE

To determine the age- and gender-related normative values and correlation of cervical sagittal parameters in asymptomatic Chinese adults, and to explore the changes and compensating mechanisms across different age groups.

METHODS

The asymptomatic subjects were divided into 6 groups according to age and then one-way analysis of variance was used to compare the multiple sets of cervical sagittal parameters among the different age groups. Independent t-tests were performed to compare the sagittal parameters among different gender and different cervical spine alignments. Relationships between each parameter were tested by Pearson's correlation. Linear regression analysis based on T1 slope (T1S) and C2 slope (C2S) was used to provide an equation to predict normal cervical alignment.

RESULTS

Mean values of each cervical sagittal parameter were presented based on age and gender. There were positive correlations between age and cervical lordosis (CL) (r = -.278, P < .001), T1S (r = .271, P < .001), cervical sagittal vertical axis (cSVA) (r = .218, P < .001), C2-C4 Cobb angle (r = -.283, P < .001), horacic inlet angle (TIA) (r = .443, P < .001), and neck tilt (NT) (r = .354, P < .001). Older groups (aged >50 years) had greater T1 Slope, C2S, and TIA. The C2-C4 Cobb angle maintained a steadily increasing trend and significantly increased in the older adult groups (P < .05), while the C5-C7 Cobb angle was relatively constant. Mean values of parameters were larger in males (P > .05). Linear regression analysis indicated a strong association between T1S and CL (R2 = .551, standard error 1.16°), T1S and C5-7 (R2 = .372; P < .001), and C2S and C2-4 (R2 = .309; P < .001).

CONCLUSIONS

Normative values of cervical sagittal parameters vary by age and sex. The CL, cSVA, and T1S, C2-4 Cobb angle changed with increasing age, and it can influence the recruitment of compensation mechanism. Normative CL of Chinese adults was predicted by the equation CL = T1S-14.7° ± 1.2°, which could serve as a reference when planning for cervical surgery.

Spinal Sagittal Alignment Changes During Childhood: Results of a National Cohort Analysis of 1,059 Healthy Children

BACKGROUND

In the past decades, it has been recognized that sagittal alignment of the spine is crucial. Although the evolution of spinal alignment with growth has previously been described, there are no data for key parameters such as the exact shapes (extent and magnitude) of spinal curvatures. The goals of this study were therefore to determine normative values of spinopelvic sagittal parameters and to explore their variation during growth, based on the analysis of a large national cohort of healthy children.

METHODS

The radiographic data of 1,059 healthy children were analyzed in a retrospective, multicenter study. Full spine radiographs were used to measure several sagittal parameters, such as pelvic parameters, T1-T12 thoracic kyphosis (TK), and L1-S1 lumbar lordosis (LL). TK was divided into proximal, middle, and distal parts, and LL was divided into proximal and distal parts. Patients were stratified into 5 groups according to skeletal maturity (based on age, Risser stage, and triradiate cartilage status).

RESULTS

During growth, pelvic incidence increased from 40° to 46° and pelvic tilt increased from 4° to 9° (p < 0.05), whereas sacral slope remained constant. The peak of change in pelvic parameters occurred at the beginning of pubertal growth in Group 2 (the first part of the pubertal growth spurt). TK slightly increased among groups from 39° to 41° (p = 0.005), with the peak of change occurring in Group 4 (pubertal growth deceleration). LL increased from 51° to 56° (p < 0.001), with the peak of change occurring in Group 3 (the second part of the pubertal growth spurt). Segmental analysis revealed that most of the TK and LL changes occurred in the distal TK and proximal LL, with the other parts remaining constant.

CONCLUSIONS

This is one of the largest studies showing changes in sagittal alignment with growth in normal children and adolescents. We found that changes in spinal shape were cascading phenomena. At the beginning of the growth peak, pelvic incidence increased. This change in pelvic morphology led to an increase in LL, involving its proximal part. Finally, TK increased, in its distal part, at the end of pubertal growth.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

How to make a more optimal surgical plan for Lenke 5 adolescent idiopathic scoliosis patients: a comparative study based on the changes of the sagittal alignment and selection of the lowest instrumented vertebra

BACKGROUND

The treatment of patients with Lenke 5 adolescent idiopathic scoliosis (AIS) is closely related to the pelvic because the spine-pelvis is an interacting whole. Besides, the choice of fusion segment is a significant issue; with the optimal choice, there will be fewer complications and restoring the pelvic morphology to some extent. This study aims to analyze the impact of changes in sagittal parameters and selection of the lowest instrumented vertebra (LIV) on spine and pelvic morphology for better surgical strategy.

METHOD

Ninety-four patients with Lenke 5 AIS who underwent selective posterior thoracolumbar/lumbar (TL/L) curve fusion were included in the study and grouped according to pelvic morphology and position of LIV. Spinopelvic parameters were measured preoperatively, postoperatively, and at the latest follow-up. The patient's preoperative and last follow-up quality of life was assessed with the MOS item short-form health survey (SF-36) and scoliosis research society 22-item (SRS-22).

RESULT

Patients being posterior pelvic tilt had the oldest mean age (P = 0.010), the smallest lumbar lordosis (LL) (P = 0.036), the smallest thoracic kyphosis (TK) (P = 0.399) as well as the smallest proximal junctional angle (PJA) while those being anterior pelvic tilt had the largest PJA. The follow-up TK significantly increased in both groups of anterior and normal pelvic tilt (P < 0.039, P < 0.006) while no significant changes were observed in the posterior pelvic tilt group. When LIV is above L4, the follow-up PJA was larger than other groups (P = 0.049, P = 0.006). When LIV is below L4, the follow-up TK and PT were larger and LL was smaller than other groups(P < 0.05). The SF-36 and SRS-22 scores were better in the LIV = L4 group than in other groups at the last follow-up (P < 0.05).

CONCLUSION

The correction of TK and LL after surgery can improve pelvic morphology. Besides, LIV is best set at L4, which will facilitate the recovery of TK, the improvement of symptoms, and the prevention of complications and pelvic deformities. Level of evidence Level III.

A gait functional classification of adolescent idiopathic scoliosis (AIS) based on spatio-temporal parameters (STP)

BACKGROUND

Therapeutic decisions for patients with adolescent idiopathic scoliosis (AIS) are mostly based on static measurements performed on two-dimensional standing full-spine radiographs. However, the trunk plays an essential role in the human locomotion, and the functional consequences during daily activities of this specific and common spinal deformity are not factored in.

RESEARCH QUESTION

Does patients with AIS have specific gait patterns based on spatio-temporals parameters measurements ?

METHODS

90 AIS patients (aged 10-18 years) with preoperative simplified gait analysis were retrospectively included for analysis between 2017 and 2020. Spatio-temporal parameters (STP) were measured on a 3-m baropodometric gaitway and included the measurement of 15 normalized gait parameters. A hierarchical cluster analysis was performed to identify group of patients based on the similarities of their gait patterns, and functional variables' inter-group differences were also measured. The subject distribution was calculated to identify the structural characteristics of the subjects according to their gait patterns.

RESULTS

Three gait patterns were identified. Cluster 1 (46%) was defined by asymmetry, Cluster 2 (16%) by instability, and Cluster 3 (36%) by variability. Each cluster was significantly different from the other ones on at least 6 different parameters (p < 0.05). Furthermore, each cluster was associated with one type of curve: Lenke 1 for Cluster 1 (57.5%), Lenke 6 for Cluster 2 (40%) and Lenke 5 for Cluster 3 (43.5%).

SIGNIFICANCE

Patients with severe AIS have a dynamic signature during gait identified on STP. Understanding consequences of this deformity on gait may be an interesting avenue to study the pathological mechanisms involved in their dynamic motor organization. Furthermore, these results might also be a first step to study the effectiveness of the different therapies.

Traditional versus magnetically controlled growing rods in early onset scoliosis surgical treatment

PURPOSE

Growing rod surgeries are common methods in the treatment of early onset scoliosis. Magnetic growing rod (MGR) surgery, in particular, has become more widespread in the last 10 years. The aim of this study was to compare the effects of traditional and magnetically controlled growing rod techniques on efficacy, safety, spinal growth, and lung development.

METHODS

A retrospective analysis was made of 24 TGR and 17 MGR patients. Inclusion criteria were patients aged < 10 years, curvature > 40° or a progression of > 10° in the 4-6 month follow-up for curves between 25 and 40°.

RESULTS

There were 9 males and 15 females in the TGR cohort and 7 males and 10 females in the MGR cohort. The mean age at first surgery was 6.1 years and 7.1 years, respectively. Major curve Cobb angles of TGR were preop. 51.5°, postop. 21.4° and 18.1° at the final follow-up. In the MGR cohort, these values were 60.4°, 41.8°, and 36.4°, respectively. The mean T1-S1 lengthening velocity was calculated as 1.12 cm/year (0.9318 mm/month) in the TGR group and 1.27 cm/year (1.0571 mm/month) in the MGR group. In the TGR cohort, a total of 99 procedures were performed as 24 initial surgeries and 75 additional procedures (5 lengthening during unplanned surgery due to complications; 4 revision, 1 debridement). In the MRG cohort, a total of 25 surgical procedures were performed as 17 initial surgeries and 7 additional procedures (3 debridements, 5 revisions).

CONCLUSION

The results of this study showed that the TGR system provided better correction in the coronal plane and was superior in kyphosis restoration than the MGR system. Both methods were successful in lengthening, but complication rates were slightly higher in the MGR cohort. The most common complication was the pullout of the proximal anchors, and this was more common in the MGR. Both TGR and MGR were found to be effective treatments. Lengthening without surgery is a significant advantage of the MGR system, but it has a high revision rate, and Cobb angle correction was found to be less effective than with TGR.

Is posteromedial translation with sublaminar bands effective in correcting axial rotation in adolescent idiopathic scoliosis surgery? A 3D reconstruction study

PURPOSE

Hybrid constructs with sublaminar bands have recently regained popularity as an alternative to all-screw construct for correction of adolescent idiopathic scoliosis (AIS). The aim of this study is to evaluate the ability of hybrid constructs with sublaminar bands to achieve a tridimensional correction of the scoliotic deformity. Our hypothesis is that hybrid construct with sublaminar bands are able to achieve a substantial derotation of the apical vertebrae, while preserving the thoracic kyphosis.

METHODS

A prospective evaluation of 50 consecutive cases (41 F, 9 M, mean age 14.7 ± 2 years) of AIS correction with hybrid construct was performed. In all cases, sublaminar bands were used at the apex of the main curve on concave side. All patients underwent pre and postoperative X-rays with EOS System, with full 3D reconstruction. Spinopelvic parameters and axial rotation of the vertebrae were measured pre and postoperatively.

RESULTS

2.7 ± 0.9 mean sublaminar bands were used per patient. Mean correction of deformity was 50 ± 9.5%. on the coronal plane. The mean axial rotation of the apical vertebra went from 18° ± 11.5° preoperatively to 9.4° ± 7.2° postoperatively (p < 0.001) with a mean derotation of 47.7%. Thoracic kyphosis went from 32.1° ± 18° preoperatively to 37.3° ± 13.1° postoperatively (p < 0.05). No intraoperative complications due to sublaminar bands were recorded.

CONCLUSIONS

Hybrid construct with sublaminar band have been showed to be safe and effective in deformity correction and in maintaining or restoring thoracic kyphosis. This study showed that with sublaminar bands applied at the curve apex a substantial derotation of the apical vertebrae can be achieved.

Restoration of thoracic kyphosis in adolescent idiopathic scoliosis with patient-specific rods: did the preoperative plan match postoperative sagittal alignment?

PURPOSE

To determine if the planned sagittal profile for thoracic kyphosis (TK) restoration was achieved after adolescent idiopathic scoliosis (AIS) surgery using a novel hybrid construct with apical double bands and precontoured patient-specific rods (PSR) made according to the detailed surgical plan for the desired sagittal plane.

METHODS

AIS patients with a Lenke type 1-4 primary right thoracic curve who underwent corrective surgery by a single surgeon and had minimum 24-month follow-up were analyzed retrospectively from a prospective database. All patients underwent simultaneous translation on two rods with apical double bands and PSR. Clinical outcomes in terms of sagittal 2D TK (T4-T12), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), PI-LL mismatch, rod angle, and rod deflection were compared between preoperative, planned, and 24-month data, while 3D apical rotation, 3D TK (T5-T12), sagittal thoracolumbar angle, degree of curvature at L1-L4 and L4-S1, proximal junctional angle, and distal junctional angle were compared at baseline and at 6 and 24 months postoperatively. SRS-22 questionnaire scores were obtained at baseline and 24 months postoperatively.

RESULTS

Forty-eight patients were included. Study patients had a median coronal thoracic curve of 62.7° preoperatively and 22.4° at 24-month follow-up (p < 0.001). Median TK gain was 6.5° for the entire cohort (n = 48) and 19.1° in the Lenke type 1 and 2 hypokyphotic subgroup (n = 14). Both groups had no significant changes between planned and 24-month TK (p = 0.068 and p = 0.943, respectively), rod angle (p = 0.776 and p = 0.548, respectively), or rod deflection (p = 0.661 and p = 0.850, respectively). For the overall study cohort, median LL gain was 7.0° (p < 0.001), 3D apical derotation was 10.7° (p < 0.001), and change in 3D TK was 36° (p < 0.001). No instance of proximal junctional kyphosis was observed. SRS-22 scores for pain, self-image, and satisfaction differed significantly between the preoperative and 24-month follow-up time-points.

CONCLUSIONS

With sagittal plane planning, desired TK, improved reciprocal changes in LL, and minimal changes in rod shape can be achieved in patients with AIS.

Quantitative evaluation of correlation between lumbosacral lordosis and pelvic incidence in standing position among asymptomatic Asian adults: a prospective study

The determination of lumbopelvic alignment is essential for planning adult spinal deformity surgery and for ensuring favorable surgical outcomes. This prospective study investigated the correlation between the lumbar section of lumbar spine lordosis and increasing pelvic incidence in 324 Asian adults with a mean age of 55 ± 13 years (range: 20-80 years), comprising 115 male and 209 female volunteers. Participants were divided into three groups based on pelvic incidence (G1, G2, and G3 had pelvic incidence of < 45°, 45-55°, and ≥ 55°, respectively). We determined that distal and proximal lumbar lordosis contributed differentially to the increase in pelvic incidence, whereas the lordosis ratio of the L3-L4 and L4-L5 segments mostly remained constant. The mean contribution ratio of the segmental lordosis from L1 to S1 was as follows: L1-L2, 2.3%; L2-L3, 11.7%; L3-L4, 18.1%; L4-L5, 25.2%; and L5-S1, 42.7%. Pelvic incidence had a stronger correlation with proximal lumbar lordosis than did distal lumbar lordosis. The ratios of proximal lumbar lordosis to distal lumbar lordosis were 37.8% in G1, 45.8% in G2, and 55.9% in G3. These findings serve as a reference for future lumbar spine correction or fusion surgery for Asian adults.

Increased proximal vertebral rotation is associated with shoulder imbalance after posterior spinal fusion for severe adolescent idiopathic scoliosis

PURPOSE

Residual shoulder imbalance is associated with suboptimal outcomes following the surgical correction of adolescent idiopathic scoliosis (AIS) including poor patient satisfaction. In this retrospective study, we evaluate the radiographic parameters and the relationship between the global and local indices of spinal alignment with shoulder balance pre- and postoperatively utilizing EOS imaging and 3D reconstruction.

METHODS

A retrospective radiographic analysis was performed on patients with AIS, treated with posterior spinal fusion. Postoperative radiographs were obtained immediately following surgery, at 6 months and final follow-up over 2 years postoperatively. 3D Radiographic measurements included in the coronal plane radiographic shoulder height difference (RSHD), proximal thoracic Cobb angle (PT) and main thoracic Cobb (MT), in the sagittal plane T4-T12 kyphosis, T12-L5 lordosis, in the axial plane proximal thoracic (PT AVR) and main thoracic apical vertebral rotation (MT AVR).

RESULTS

Sixty-six patients were included (63 females) with an average main thoracic curvature of 76 degrees. RSHD averaged 14 mm ± 14 preoperatively, -15 mm ± 12 postoperatively, -8.5 mm ± 11 at 6 months, and -8.3 mm ± 8.7 at final follow-up, respectively. Statistical analysis revealed a significant correlation between RSHD and proximal thoracic Cobb angle, between RSHD and proximal thoracic apical vertebral rotation (PTAVR) (r > 0.20, p < 0.05).

CONCLUSION

The significant correlation presented in this study suggests that PT Cobb angle and PT AVR are involved in postoperative shoulder imbalance.

THE LEVEL OF EVIDENCE

Level 4.

Does the Distal Level Really Matter in the Setting of Health-Related Quality of Life? Assessment of a Series of Adolescent Idiopathic Scoliosis Patients at More Than 7 Years Following Surgery

STUDY DESIGN

Retrospective longitudinal study.

OBJECTIVE

The main goal of this study was to measure the disability after AIS correction, according to the LIV.

SUMMARY OF BACKGROUND DATA

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine that may require surgical correction. If the upper and lower instrumented levels (UIV and LIV) of these fusions are defined by the characteristics of the curve, the long-term consequences of the LIV choices are still partially unknown.

METHODS

This retrospective longitudinal study collected demographic, radiologic (Lenke classification, Cobb angle), and surgical data (approach, LIV, UIV) on 116 patients operated for AIS fusion on a specialized pediatric spine center were collected. All participants answered SRS30, SF12, lumbar and leg pain Visual Analogue Scales (VAS) at last follow-up. Statistical analysis between LIV (T12L1, L2, L3 or L4L5) and clinical data at last follow-up was realized.

RESULTS

The mean follow-up was 87months. The mean increase of back pain VAS per UIV level was 9 mm. No statistically significant difference between the different LIV was found, for SRS30 or SF12 MCS (mental component scale). There was a statistically significant difference between L3 UIV and L4L5 UIV for SF-12 PCS (physical component scale); ( P = 0.03).

CONCLUSION

The long-term consequences of LIV choice mostly affect levels distal to L3. If the LIV is mostly defined by the characteristics of the curve, one level caudally corresponds to +9 mm of back pain VAS at 7 years of follow-up. Surgeons may be aware of the long-term consequence of LIV choice and patients be informed.

How does magnetically controlled growing rods insertion affect sagittal alignment in ambulatory early onset scoliosis patients?

PURPOSE

The importance of sagittal alignment restoration in early onset scoliosis (EOS) management has rarely been investigated to date. The aim was to report the influence of magnetically controlled growing rods (MCGR) insertion on the sagittal alignment of EOS patients.

METHODS

All consecutive ambulatory patients operated with MCGR rods between 2011 and 2018 were retrospectively included in four institutions. Standing biplanar radiographs were performed preoperatively, in the early postoperative period and at latest follow-up. Global and local sagittal parameters, spinal global shape and harmony were investigated.

RESULTS

A total of 37 ambulatory EOS patients were included (mean age at surgery 8.5 (± 2) years). 70% had a balanced construct postoperatively. Both MaxTK (- 17°, p = 0.02) and MaxLL (- 15°, p = 0.001) were significantly reduced, particularly at the instrumented levels. The number of vertebrae included in the lumbar lordosis significantly increased (+ 2 levels, p = 0.02), as well as the thoraco-lumbar inflexion point (+ 2 levels, p < 0.001) and the kyphosis apex (+ 1 level, p < 0.001). Overall mechanical failure rate was 40.5%, and radiological PJK was observed in 43% of the patients, with 11 remaining asymptomatic. Patients with initial hyperkyphosis (> 50°) developed more complications (62% vs. 28%, p = 0.04).

CONCLUSION

MCGR insertion flattened the spine in EOS, at both instrumented and non-instrumented levels. Overall spinal harmony was modified, with a cranial shift of the thoraco-lumbar inflexion point and the thoracic kyphosis apex, associated with a lengthening of the lumbar lordosis. The rate of complication remained high, some explanations being found in the radiological changes reported such as the preoperative location of the TK apex.

LEVEL OF EVIDENCE

IV.

The Prevalence of Hip Pathologies in Adolescent Idiopathic Scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is the most common form of abnormal spine curvature observed in patients age 10 to 18. Typically characterized by shoulder height and waistline asymmetry, AIS may drive uneven distribution of force in the hips, leading to increased rates of concurrent hip diagnoses. The relationship between AIS and concurrent hip diagnoses is underexplored in the literature, and to date, there has been little research comparing rates of hip diagnoses between patients with AIS and those unaffected.

Purpose

Assess differences in rates and clusters of hip diagnoses between patients with AIS and those unaffected.

Study design

Retrospective review of Healthcare Cost and Utilization Project's (HCUP) Nationwide Inpatient Sample (NIS).

Patient sample

224,504 weighted inpatient discharges.

Outcome measures

Rates of hip diagnoses.

Methods

Patients in the NIS database (2005-2013) ages 10-18 years were isolated. Patients were grouped by those diagnosed with AIS (ICD-9: 737.30) and those unaffected. Patient groups were propensity score matched (PSM) for age. Means comparison tests assessed differences in demographic, comorbidity, and diagnosis profiles between patient groups for corresponding age categories. ICD-9 codes were used to identify specific hip diagnoses.

Results

Following PSM, 24,656 AIS and 24,656 unaffected patients were included. The AIS patient group was comprised of more females (66% vs 59%) and had lower rates of obesity (2.4% vs 3.5%, both p < 0.001). Overall, 1.1% of patients had at least one hip diagnosis: congenital deformity (0.31%), developmental dysplasia (0.24%), recurrent dislocation (0.18%), isolated dislocation (0.09%), osteonecrosis (0.08%), osteochondrosis (0.07%), acquired deformity (0.03%), and osteoarthritis (0.02%). AIS patients had lower rates of osteonecrosis (0.04% vs 0.12%, p = 0.003), but higher rates of all other hip diagnoses, including dysplasia (0.41% vs 0.07%, p < 0.001), recurrent dislocation (0.32% vs 0.03%, p < 0.001), isolated dislocation (0.13% vs 0.06%, p < 0.001), and osteoarthritis (0.04% vs 0.01%, p = 0.084. Co-occurrences of hip diagnoses were relatively rare, with 0.03% patients having more than one hip diagnosis. Rates of co-occurring hip diagnoses did not differ between AIS and unaffected groups (0.04% vs 0.02%, p = 0.225).

Conclusions

Compared to unaffected patients of similar ages, patients with AIS had higher overall rates of hip diagnoses, including dysplasia and recurrent dislocation. A higher trend of precocious osteoarthritis was also observed at a higher rate in AIS patients, although this difference was not statistically significant. Our results present an argument for surgical realignment in the coronal and sagittal planes to neutralize asymmetrical forces in the hips, and suggest the need for increased awareness and clinical screening for hip-related disorders in AIS patients.

Level of Evidence

III.

W-Transformer: Accurate Cobb angles estimation by using a transformer-based hybrid structure

BACKGROUND

Scoliosis is a type of spinal deformity, which is harmful to a person's health. In severe cases, it can trigger paralysis or death. The measurement of Cobb angle plays an essential role in assessing the severity of scoliosis.

PURPOSE

The aim of this paper is to propose an automatic system for landmark detection and Cobb angle estimation, which can effectively help clinicians diagnose and treat scoliosis.

METHODS

A novel hybrid framework was proposed to measure Cobb angle precisely for clinical diagnosis, which was referred as W-Transformer due to its w-shaped architecture. First, a convolutional neural network of cascade residual blocks as our backbone was designed. Then a transformer was fused to learn the dependency information between spine and landmarks. In addition, a reinforcement branch was designed to improve the overlap of landmarks, and an improved prediction module was proposed to fine-tune the final coordinates of landmarks in Cobb angles estimation. Besides, the public AASCE MICCAI 2019 challenge was served as dataset. It supplies 609 manually labeled spine AP X-ray images, each of which contains a total of 68 landmark labels and three Cobb Angles tags.

RESULTS

From the perspective of the AASCE MICCAI 2019 challenge, we achieved a lower symmetric mean absolute percentage error (SMAPE) of 8.26% for all Cobb angles and the lowest averaged detection error of 50.89 in terms of landmark detection, compared with many state-of-the-art methods. We also provided the SMAPEs for the Cobb angles of the Proximal-Thoracic (PT), the Main-Thoracic (MT) and the Thoracic-Lumbar (TL) area, which are 5.27%, 14.59% and 20.97% respectively, however, these data were not covered in most previous studies. Statistical analysis demonstrates that our model has obtained a high level of Pearson correlation coefficient of 0.9398 (p<0.001), which shows excellent reliability of our model. Our model can yield 0.9489 (p<0.001), 0.8817 (p<0.001) and 0.9149 (p<0.001$) for PT, MT and TL, respectively. The overall variability of Cobb angle measurement is less than 4°, implying clinical value. And the mean absolute deviation (Standard Deviation) for three regions is 3.64° (4.13°), 3.84° (4.66°) and 3.80° (4.19°). The results of Student paired t-test indicate that no statistically significant differences are observed between manual measurement and our automatic approach (p value is always > 0.05). Regarding the diagnosis of scoliosis (Cobb angle > 10°), the proposed method achieves a high sensitivity of 0.9577 and a specificity of 0.8475 for all spinal regions.

CONCLUSIONS

This study offers a brand-new automatic approach that is potentially of great benefit of the complex task of landmark detection and Cobb angle evaluation, which can provide helpful navigation information about the early diagnosis of scoliosis. This article is protected by copyright. All rights reserved.

Effects of posterior hemivertebra resection and short segment fusion on the evolution of sagittal balance in children with congenital scoliosis

There is a paucity of data describing sagittal alignment changes in children with congenital scoliosis (CS) treated by hemivertebra (HV) resection. This study aimed to evaluate the effects of posterior HV resection on spine sagittal alignment in children with CS. This is a retrospective analysis of 31 children with CS (mean age at surgery: 49.61 ± 10.21 months; range, 39-72; mean follow-up time: 5.16 ± 1.21 years; range: 3-7) treated at our Institution. Only patients with single thoracic or single lumbar, fully segmented HV managed by posterior HV resection and two segments fusion with four screws and two robs were included. According to the anatomical location of the HV, patients were divided into two groups: thoracic (group A) and lumbar (group B). Thoracic kyphosis (T1-T12; TK) and lumbar lordosis (L1-S1; LL) were measured pre- and postoperatively at 6 months interval. Postoperative TK and LL were 30.3 ± 11.47 and 28.8 ± 9.47, and were 31.98 ± 9.66 and 46.7 ± 11.37 at the last follow-up visit, respectively. The incidence of thoracic hypokyphosis in group B was 53.3%, and it was significantly higher compared to group A (12.5%, P = 0.04). During follow-up, TK changes were comparable between the two groups of patients while LL improved in all patients 6 months after surgery, and continued to improve thereafter. Posterior HV resection and short segment fusion have limited impact on the evolution of TK; in particular, children with lumbar HV were more likely to be hypokyphotic preoperatively, but less likely postoperatively with an increase in LL and a stabilization of TK.

Incidence and Radiological Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw Instrumentation with Rod Derotation and Direct Vertebral Rotation: A Minimum 5-Year Follow-Up Study

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group (n = 62) and PJK group (n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively (p = 0.027), postoperatively (p = 0.001), and at last follow-up (p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

Pelvic and sacral morphology and their correlation with pelvic incidence, lumbar lordosis, and lumbar alignment changes between standing and sitting postures

STUDY DESIGN

Retrospective Cross-Sectional Radiographic Study.

OBJECTIVE

This study aims to describe novel radiographic markers of sacropelvic morphology to further define the static and dynamic relationship between the pelvis and the spine, via the analysis of two postures - standing and sitting.

SUMMARY OF BACKGROUND DATA

There is increasing evidence underlining the importance of spinopelvic radiographic parameters in the holistic management of sagittal spinal deformity given the close relationship between pelvic morphology and spinal profile.

METHODS

This is a retrospective radiographic study of patients who presented with the first episode of isolated mechanical, low back pain of fewer than 3 months' duration. All patients underwent whole spine radiographs using EOS technology in both standing and relaxed sitting postures. Six novel distance measurements (H1, H2, H3, V1, V2, DD) to determine pelvic dimensions, and 3 novel angles (A, B, C) to determine sacral morphology were described.

RESULTS

A total of 64 males (58.2%) and 46 females (41.8%) with a mean age of 42.8 ± 18.6 (range:17-81) years old was studied. Between standing and relaxed sitting postures, differences were observed in all sagittal radiographic parameters. Multivariate analysis showed that standing LL< 50⁰ (p = 0.008), standing V1 > 13 cm(p = 0.040), and angle B> 80⁰(p = 0.002) are predictive of PI< 5⁰⁰, standing TK< 30⁰ (p = 0.003) and PI< 50⁰ (p = ⁰.006) are predictive of LL< 5⁰⁰, and standing PT< 17⁰(p = 0.034), standing H3 ≥ 4 cm (p = 0.030), standing angle C< 42⁰ (p = 0.003), sitting SS≥ 6⁰ (p = ⁰.002), and sitting PT < 45⁰ (p = 0.013) are predictive of change in LL below mean difference of 42⁰ between standing and relaxed sitting.

CONCLUSIONS

Apart from the known correlation between TK, LL and PI, low PI was found to be associated with a tall pelvis and a straight sacrum (angle B). Association between a small coccygeal inclination angle (angle C) and smaller change in LL between standing and relaxed sitting may have clinical relevance.

Cervical sagittal alignment in Lenke 1 adolescent idiopathic scoliosis and assessment of its alteration with surgery: a retrospective, multi-centric study

PURPOSE

To document baseline cervical sagittal characteristics in Lenke 1 adolescent idiopathic scoliosis (AIS) patients and assess the alteration in these parameters with surgery.

METHODS

Pre-operative and 2-year postoperative radiographs of 82 Lenke 1 AIS patients recruited from five hospitals were analysed. Selected radiographic parameters capturing regional and global sagittal alignment were measured. Comparison was made between groups based on baseline thoracic kyphosis (TK: TK < 20°, TK ≥ 20°). Pre-operative and postoperative values were compared-the change in each radiographic parameter was correlated with the degree of sagittal and coronal correction.

RESULTS

At baseline, TK was 29.8° ± 16°, cervical lordosis (CL) was - 1° ± 14°, lumbar lordosis (LL) was - 57.1° ± 21°, C2-C7 sagittal vertical axis (SVA) was 16 ± 14 mm and C7-S1 SVA was - 15 ± 28 mm; 44% of patients had cervical kyphosis. Patients with thoracic hypokyphosis had a significantly lower LL and more kyphotic cervical spine compared to those with thoracic normohyperkyphosis. The effect of surgery on TK depended on pre-operative thoracic sagittal alignment-TK increased in patients with thoracic hypokyphosis, but decreased in patients with thoracic normohyperkyphosis. Neither CL nor C2-C7 SVA changed significantly with surgery; 46% of patients still had cervical kyphosis postoperatively.

CONCLUSION

There is a high incidence of cervical kyphosis at baseline in AIS patients-more so in those with pre-operative thoracic hypokyphosis. Unlike TK, CL is not significantly altered with surgery-improvement in CL correlates weakly with sagittal correction of the structural curve.

The Effect of Posterior Lumbar Spinal Surgery on Biomechanical Properties of Rat Paraspinal Muscles 13 Weeks After Surgery

STUDY DESIGN

Preclinical study in rodents.

OBJECTIVE

To investigate changes in biomechanical properties of paraspinal muscles following a posterior spinal surgery in an animal model.

SUMMARY OF BACKGROUND DATA

Posterior spine surgery damages paraspinal musculature per histological and imaging studies. The biomechanical effects of these changes are unknown.

METHODS

12 Sprague-Dawley rats were divided equally into sham and surgical injury (SI) groups. For sham, the skin and lumbodorsal fascia were incised at midline. For SI, the paraspinal muscles were detached from the vertebrae, per normal procedure. Thirteen weeks postsurgery, multifidus and longissimus biopsies at L1, L3, and L5 levels were harvested on the right. From each biopsy, three fibers and three to six bundles of fibers (∼10-20 fibers ensheathed in their extracellular matrix) were tested mechanically to measure their passive elastic modulus. The collagen content and fatty infiltration of each biopsy were also examined histologically by immunofluorescence staining. Nonparametric statistical methods were used with a 1.25% level of significance.

RESULTS

A total of 220 fibers and 279 bundles of fibers were tested. The elastic moduli of the multifidus and longissimus fibers and longissimus fiber bundles were not significantly different between the SI and sham groups. However, the elastic modulus of multifidus fiber bundles was significantly greater in the SI group compared to sham (SI median 82 kPa, range 23-284; sham median 38 kPa, range 23-50, P = 0.0004). The elastic modulus of multifidus fiber bundles in the SI group was not statistically different between spinal levels (P = 0.023). For histology, only collagen I deposition in multifidus was significantly greater in the SI group (median 20.8% vs. 5.8% for sham, P < 0.0001).

CONCLUSION

The surgical injury increased the passive stiffness of the multifidus fiber bundles. Increased collagen content in the extracellular matrix is the likely reason and these changes may be important in the postoperative compensation of the spine.Level of Evidence: N/A.

The measurement of Cobb angle based on spine X-ray images using multi-scale convolutional neural network

Adolescent idiopathic scoliosis (AIS) is a structural spinal deformity mainly in the coronal plane and is among the most frequent deformities in children, adolescents, and young adults, with an overall prevalence of 0.47-5.2%. The Cobb angle is an objective measure to determine the progression of deformity and plays a critical role in the planning of surgical treatment. However, existing studies suggested that Cobb angle measurement is susceptible to inter- and intra-observer variability, as well as a high variability in the definition of the end vertebra. In this study, we proposed an automatic method for the spine vertebrae segmentation using Deeplab V3+, a powerful tool that has shown success in the image segmentation of other anatomical regions but spine, and Cobb angle measurement. The segmentation performance was compared to existing mainstay neural networks. Compared to U-Net, Residual U-Net and Dilated U-Net, our method using Deeplab V3+ showed the best performance in the Dice Similarity Coefficient (DSC), accuracy, sensitivity and Jaccard Index. An excellent correlation in the final Cobb angle calculation was achieved between the smallest distance point (SDP) method and two experts (> 0.95), with a small error in the angle estimation compared (MAE < 3°). The proposed method could provide a potential tool for the automatic estimation of the Cobb angle to improve the efficiency and accuracy of the treatment workflow for AIS.

Proximal junctional kyphosis is a rebalancing spinal phenomenon due to insufficient postoperative thoracic kyphosis after adolescent idiopathic scoliosis surgery

PURPOSE

Many authors tried to explain proximal junctional kyphosis (PJK) after adolescent idiopathic scoliosis (AIS) surgery by looking for risk factors. Latest publications focus on sagittal alignment. Each healthy adolescent has a specific thoracic kyphosis (TK) depending on their pelvic parameters and lumbar lordosis (LL). The objective of this work is to determine if the difference between TK at follow-up (TKFU) and the patient-specific TK (PSTK) plays a role in PJK occurrence after AIS surgery. The secondary objective was to find other risk factors.

METHODS

We analyzed retrospectively 570 thoracic AIS who underwent a posterior thoracic fusion from nine centers. The series was separated in two groups: with and without PJK. PSTK was calculated with the formula PSTK = 2(PT + LL-PI). TK Gap was the difference between TKFU and PSTK. Logistic regression was utilized to test the impact of TK Gap and other known risk factors on PJK occurrence.

RESULTS

Univariate analysis showed 15 factors significantly different between the groups. In a multivariate analysis, three factors had a strong significant influence on PJK: TKFU, TK Gain and TK Gap. Four additional factors affected the rate of PJK: Posterior translation on two rods, preoperative TK, preoperative LL and number of instrumented vertebrae.

CONCLUSION

PJK is related to the insufficient TK at follow-up, compared to the specific TK that every patient should have according to their pelvic parameters. PJK incidence is significantly reduced by a strong gain in TK and a thoracic selective fusion which leaves the proximal lumbar vertebrae free.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Direct vertebral rotation significantly decreases the pullout strength of the pedicle screw: a biomechanical study in adult cadavers

The pullout strength of the pedicle screws after direct vertebral rotation (DVR) maneuver is not known. This biomechanical study was performed to quantitatively analyze the pullout strength of a pedicle screw after DVR maneuver using human cadaveric vertebrae. Thoracic vertebral bodies from three cadavers were harvested and stripped of soft tissues. Thirty pedicles of 15 vertebrae were separated into two groups after bone mineral density measurements. Polyaxial 5.5 mm pedicle screws with appropriate length were inserted with a freehand technique for each pedicle. One Kirschner wire was inserted to the anterior part of each vertebral corpus the half depth of each corpus was embedded into PVC pipes using polyester paste. In the DVR group, each screw was pulled horizontally with 2 kg (~20 N) load over a screwdriver rigidly attached to the screw, and a DVR maneuver was simulated. The control group did not load with a DVR maneuver. Samples were placed on a universal testing machine and pullout loads were measured. The Mann-Whitney U test was utilized, and the P value <0.05 was considered as statistically significant. In the DVR group, the mean pullout strength was 183.35 N (SD ± 100.12), and in the control group, the mean pullout strength was 279.95 N (SD ± 76.26). Intergroup comparisons revealed that DVR maneuver significantly decreases the pullout strength (P = 0.012). The results of this study confirm that the pullout strength of pedicle screw significantly decreases by approximately 35% when DVR maneuver is applied.

Global sagittal alignment after surgery of right thoracic idiopathic scoliosis in adolescents and adults with and without thoracic hypokyphosis

This study aimed to characterize global sagittal alignment in adolescent idiopathic scoliosis (AIS) with normal kyphosis (NTK, kyphosis > 10°) and with thoracic hypokyphosis (THK, kyphosis < 10°), before and after posterior spinal fusion, and compare them with asymptomatic controls. 27 AIS girls and young adults with right thoracic curves were included (seventeen with age ≤ 18 years, then age > 21). Biplanar radiographies were acquired at baseline, immediate post-operatively, 1-year and 2-year follow-up, and 3D reconstruction of the spine and pelvis was performed. NTK and THK showed different global sagittal alignment, as well as differences compared to controls. AIS with THK at baseline had higher SVA/SFD (2.0 ± 2.9 vs - 0.4 ± 1.9; P < 0.05) and OD-HA (0.2 ± 1.4° vs - 1.3 ± 1.6°; P < 0.05) than controls, indicating that THK had compensated balance with unusual forward leaning posture. Immediately post-operation, SVA/SFD remained high (1.3 ± 3.0) while OD-HA reversed (- 1.2 ± 1.7°), indicating that THK patients had found partially compensated balance. After 2-yeas, both SVA/SFD (- 1.3 ± 2.1) and OD-HA (- 1.4 ± 0.9°) were normalized. The changes in global sagittal alignment and mechanism of balance are different in AIS with or without THK. As the head plays a critical role on balance during immediate and delayed post-operation, OD-HA can be complementary parameter for assessing global balance during post-operative follow-up of AIS patients with THK.

Comparison of different strategies on three-dimensional correction of AIS: which plane will suffer?

PURPOSE

There are distinct differences in strategy amongst experienced surgeons from different 'scoliosis schools' around the world. This study aims to test the hypothesis that, due to the 3-D nature of AIS, different strategies can lead to different coronal, axial and sagittal curve correction.

METHODS

Consecutive patients who underwent posterior scoliosis surgery for primary thoracic AIS were compared between three major scoliosis centres (n = 193). Patients were treated according to the local surgical expertise: Two centres perform primarily an axial apical derotation manoeuvre (centre 1: high implant density, convex rod first, centre 2: low implant density, concave rod first), whereas centre 3 performs posteromedial apical translation without active derotation. Pre- and postoperative shape of the main thoracic curve was analyzed using coronal curve angle, apical rotation and sagittal alignment parameters (pelvic incidence and tilt, T1-T12, T4-T12 and T10-L2 regional kyphosis angles, C7 slope and the level of the inflection point). In addition, the proximal junctional angle at follow-up was compared.

RESULTS

Pre-operative coronal curve magnitudes were similar between the 3 cohorts and improved 75%, 70% and 59%, from pre- to postoperative, respectively (P < 0.001). The strategy of centres 1 and 2 leads to significantly more apical derotation. Despite similar postoperative T4-T12 kyphosis, the strategy in centre 1 led to more thoracolumbar lordosis and in centre 2 to a higher inflection point as compared to centre 3. Proximal junctional angle was higher in centres 1 and 2 (P < 0.001) at final follow-up.

CONCLUSION

Curve correction by derotation may lead to thoracolumbar lordosis and therefore higher risk for proximal junctional kyphosis. Focus on sagittal plane by posteromedial translation, however, results in more residual coronal and axial deformity.

COMPARATIVE STUDY OF THE TYPES OF FIXATION IN ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Objective: To conduct a comparative study of the results obtained in the treatment of adolescent idiopathic scoliosis (AIS) with different types of fixations (traditional, selective and multiple), and to evaluate the correction of angular deformity in the frontal plane by the Cobb and sacral clavicular angle (SCA) methods. Methods: A study of a group of 278 patients with AIS who underwent selective, traditional, and multiple fixation surgeries. Results: Significant corrections of both the Cobb angle and the SCA were observed. Conclusions: In the multiple fixation surgeries there was a 100% correction between the preoperative and postoperative SCA values and a 50% correction in the traditional and selective fixations, a difference considered significant. Regarding the Cobb angle, the three fixations presented corrections between preop and postop with significant differences. Level of evidence III; Retrospective Study.

Evaluation of correlation between sagittal balance and plantar pressure distributions in adolescent idiopathic scoliosis: A pilot study

BACKGROUND

To evaluate the correlation between baropodometric parameters and sagittal parameters for adolescent idiopathic scoliosis.

METHODS

44 volunteers (7 males and 37 females) were recruited. All participants were diagnosed as adolescent idiopathic scoliosis by X-ray before baropodometric study. Sagittal parameters included thoracic kyphosis, lumbar lordosis, sagittal vertical axis, pelvic tilt, sacral slope and pelvic incidence. A static baropodometry was performed for each patient. The foot area was divided into four quadrants. The contact surface and weight percentage were measured.

FINDINGS

Lumbar lordosis was positively correlated to pelvic incidence, sacral slope and (P < 0.001, P < 0.001, respectively). On the major curve side, pelvic tilt showed a positive correlation with all baropodometric parameters (P < 0.05) except forefoot weight percentage. Thoracic kyphosis showed negative correlations with contact surface and weight percentage of the forefoot (P = 0.04, 0.02 respectively) but no correlation with any rearfoot feature. Lumbar lordosis, sagittal vertical axis, pelvic incidence and sacral slope were not in correlation with plantar pressure. On the opposite side, sagittal profile showed no obvious correlation with any baropodometric parameter.

INTERPRETATION

In scoliosis, sagittal balance is closely correlated to plantar pressure distributions. Baropodometry is a feasible method to assess sagittal balance.

Specific sagittal alignment patterns are already present in mild adolescent idiopathic scoliosis

PURPOSE

The complex three-dimensional spinal deformity in AIS consists of rotated, lordotic apical areas and neutral junctional zones that modify the spine's sagittal profile. Recently, three specific patterns of thoracic sagittal 'malalignment' were described for severe AIS. The aim of this study is to define whether specific patterns of pathological sagittal alignment are already present in mild AIS.

METHODS

Lateral spinal radiographs of 192 mild (10°-20°) and 253 severe (> 45°) AIS patients and 156 controls were derived from an international consortium. Kyphosis characteristics (T4-T12 thoracic kyphosis, T10-L2 angle, C7 slope, location of the apex of kyphosis and of the inflection point) and sagittal curve types according to Abelin-Genevois were systematically compared between the three cohorts.

RESULTS

Even in mild thoracic AIS, already 49% of the curves presented sagittal malalignment, mostly thoracic hypokyphosis, whereas only 13% of the (thoraco) lumbar curves and 6% of the nonscoliosis adolescents were hypokyphotic. In severe AIS, 63% had a sagittal malalignment. Hypokyphosis + thoracolumbar kyphosis occurred more frequently in high-PI and primary lumbar curves, whereas cervicothoracic kyphosis occurred more in double thoracic curves.

CONCLUSIONS

Pathological sagittal patterns are often already present in curves 10°-20°, whereas those are rare in non-scoliotic adolescents. This suggests that sagittal 'malalignment' patterns are an integral part of the early pathogenesis of AIS.

Proximal junctional kyphosis in Lenke 5 AIS patients: the important factor of pelvic incidence

Background

The purpose of the study was to investigate whether pelvic incidence (PI) will affect the occurrence of PJK in Lenke 5 AIS patients after correction surgery and try to explore a better surgical scheme based on PI.

Methods

Lenke 5C AIS patients that underwent correction surgery with a minimum of a 2-year follow-up were identified. Demographic and radiographic data were collected preoperatively, postoperatively, and at the final follow-up. The comparison between the PJK and the Non-PJK group was conducted and the subgroup analysis was performed based on the preoperative value of PI to investigate the potential mechanism of PJK. Clinical assessments were performed using the Scoliosis Research Society (SRS)-22 questionnaire.

Results

The mean preoperative Cobb angle of the TL/L curve was 53.4°±8.6. At the final follow-up, the mean TL/L Cobb angle was drastically decreased to 7.3°±6.8 (P < 0.001). The incidence of PJK in Lenke 5 AIS was 18.6 %, 21.9 % (7/32) in the low PI group (PI < 45°) and 15.8 % (6/38) in the high PI group (PI ≥ 45°), and there was no statistical difference between the two groups (χ² = 0.425, P = 0.514). For low PI patients, there is no significant difference where the UIV is located with regards to the TK apex between the PJK and Non-PJK subgroups (χ² = 1.103, P = 0.401). For high PI patients, PJK was more likely to occur when UIV was cephalad to than caudal to the TK apex (31.25 % vs. 4.7 %, P = 0.038). There was no significant difference in the selection of LIV between the two groups.

Conclusions

There is no difference in the incidence of PJK between the Lenke 5 AIS patients with low PI (< 45°) and high PI (≥45°), but the main risk factor of PJK should be different. For patients with low PI, overcorrection of LL should be strictly avoided during surgery. For patients with high PI, the selection of UIV should not be at or cephalad to the apex of thoracic kyphosis to retain more mobile thoracic segments.

The effect of pedicle subtraction osteotomy for the correction of severe Scheuermann thoracolumbar kyphosis on sagittal spinopelvic alignment

Purpose

To analyze how pedicle subtraction osteotomy (PSO) treatment of severe Scheuermann thoracolumbar kyphosis (STLK) using pedicle screw instrumentation affects sagittal spinopelvic parameters.

Background

The medical literature on the post-surgical effects of treatments such as Ponte osteotomy is limited, but suggests few effects on spinopelvic profiles. Currently, there is no research regarding changes in sagittal spinopelvic alignment upon PSO treatment in STLK patients.

Methods

We performed a retrospective study on 11 patients with severe STLK. These patients underwent posterior-only correction surgeries with PSO and pedicle screw instrumentation between 2012 to 2017 in a single institute. Patients were measured for the following spinopelvic parameters: global kyphosis (GK), thoracic kyphosis (TK), thoracolumbar kyphosis (TL), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tile (PT), sacral slope (SS), and administered a Scoliosis Research Society-22 questionnaire (SRS-22) pre-operation, post-operation and at final follow-up.

Results

GK improved from a median of 74.1° to 40.0° after surgery, achieving a correction rate of 48.8% with a median correction loss of 0.8°. TK, TL and LL all showed significant difference (P < 0.05) and SVA improved 22.7 (11.6, 30.9) mm post operation. No significant difference was found in pelvic parameters (PI, PT, SS, all P < 0.05). The absolute value of LL- PI significantly improved from a median of 26.5° pre-operation to 6.1° at the final follow-up. 72.7% in this series showed an evident trend of thoracic and lumbar apices migrating closer to ideal physiological segments after surgery. Self-reported scores of pain, self-image, and mental health from SRS-22 revealed significant improvement at final follow-up (all P < 0.05).

Conclusions

PSO treatment of severe STLK with pedicle screw instrumentation can improve spine alignment and help obtain a proper alignment of the spine and the pelvis.

Sagittal profile modifications in hybrid versus all screw technique in adolescent idiopathic scoliosis

Aim of the study was to evaluate sagittal parameters modifications, with particular interest in thoracic kyphosis, in patients affected by adolescent idiopathic scoliosis (AIS) comparing hybrid and all-screws technique. From June 2010 to September 2018, 145 patients were enrolled. Evaluation included: Lenke classification, Risser scale, coronal Cobb angle, thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS). Patients were divided in two groups (1 all-screws and 2 hybrid); a further division, in both groups, was done considering preoperative TK values. Descriptive and inferential statistical analysis was conducted. 99 patients were in group 1, 46 in group 2 (mean follow-up 3.7 years). Patients with a normo-kyphotic profile developed a little variation in TK (Δ pre–post = 2.4° versus − 2.0° respectively). Hyper-kyphotic subgroups had a tendency of restoring a good sagittal alignment. Hypo-kyphotic subgroups, patients treated with all-screw implants developed a higher increase in TK mean Cobb angle (Δ pre–post = 10°) than the hybrid subgroup (Δ pre–post = 5.4°) (p = 0.01). All-screws group showed better results in restoring sagittal alignment in all subgroups compared to hybrid groups, especially in hypo-TK subgroup, with the important advantage to give better correction on coronal plane.

Severe persistent coronal imbalance following instrumented posterior spinal fusion for adolescent idiopathic scoliosis

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

The aim of this study was to identify the risk factors and health-related quality of life (HRQoL) impact of severe (> 4 cm) post-operative coronal imbalance at 2 years following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Coronal imbalance is an unfavorable outcome following PSF for AIS, though the degree of imbalance in such patients is typically mild. We hypothesize that a small number of patients become and remain severely imbalanced post-operatively, though this phenomenon has not been well studied.

METHODS

Prospectively collected data from a large multicenter registry were reviewed. Patients with severe coronal imbalance (SCIB; > 4 cm) 2 years after PSF were included. Matched controls without SCIB at 2 years were included at a 3:1 ratio. Comparisons were made between demographics, pre-operative radiographic measures, surgical factors, residual post-operative radiographic measures, and 2-year SRS-22 scores.

RESULTS

Nine of 954 (0.9%) patients (88.9% females; mean age 14.8 ± 2.3 years) were found to be severely imbalanced at 2 years. These patients had significantly greater pre-operative bending thoracic curve magnitude (45° vs. 33°; p = 0.013), curve flexibility (22.9% vs. 63.3%; p = 0.004), and kyphosis (41° vs. 26.5°; p = 0.034) compared to matched controls. Pre-operative curve flexibility of < 20% was associated with a 23.8 times greater odds of SCIB (95% CI 2.1-250; p = 0.008). With respect to HRQoL, median SRS-22 pain (4.1 vs. 4.8; p = 0.041), self-image (3.9 vs. 4.6; p = 0.013), general function (4.5 vs. 5; p = 0.022), and total (4.1 vs. 4.7; p = 0.012) scores at 2 years were significantly lower in cases compared to controls.

CONCLUSIONS

In the present study, thoracic curve stiffness was a strong risk factor for severe post-operative coronal imbalance, which was associated with poor HRQoL measures. Increased pre-operative thoracic curve stiffness (< 20% flexibility) should raise surgeon awareness for altering surgical approach to minimize the risk of severe post-operative coronal imbalance.

LEVEL OF EVIDENCE

Level III.

CORRECTION OF THE SPINAL SAGITTAL PLANE: THE APPLICATION OF CONVERGENT OR DIVERGENT SCREWS

ABSTRACT Objective To present a new principle for correction of the sagittal plane of the spine through the convergent or divergent placement of monoaxial pedicle screws in this plane, associated with compression or distraction, to provide lordotizing or kyphotizing leverage force. Method A statistical mechanical study of twenty-eight fixations in synthetic spine segments was performed. In fifteen pieces, pedicle screws were applied to the ends of the segments with positioning convergent to the center of the fixation. They were attached to the straight rods and subjected to compression force. The other thirteen segments were fixed with pedicle screws in a direction divergent to the center of the fixation, attached to the straight rods, and subjected to distraction force. Results To create kyphosis in the 15 synthetic segments of the spine, the mean pre-fixation Cobb angle was - 0.7° and the mean post-fixation angle was +15°. To create lordosis in the 13 segments, the mean pre-fixation Cobb angle was +1° and the mean post-fixation angle was +18°. The difference was confirmed by statistical mechanical tests and considered significant. However, there is no relevant difference between the mean angles for lordosis and kyphosis formation. Conclusions It was concluded that the correction of the sagittal plane of the spine by applying the new instrumentation method is efficient. A statistical mechanical test confirmed that the difference in Cobb degrees between pre- and post-fixation of the synthetic spine segments was considered significant in the creation of both kyphosis and lordosis. Level of evidence II C; Statistical mechanical study of synthetic spine segments.

The Impact of Posterior Spinal Fusion (PSF) on Coronal Balance in Adolescent Idiopathic Scoliosis (AIS): A New Classification and Trends in the Postoperative Period

INTRODUCTION

One of the primary goals of scoliosis surgery is to balance the head over the pelvis (or avoid creating imbalance). Historically, a normal coronal balance was defined as the C7 plumb line (C7PL) within 2 cm of the central sacral vertical line (CSVL); however, there is limited published information regarding the speed/magnitude and success/failure of balancing, rebalancing, or unbalancing in the postoperative period. The purpose of this study is to classify and quantify coronal plane balance postoperatively in adolescent idiopathic scoliosis when using pedicle screw instrumentation.

METHODS

Evaluated patients with adolescent idiopathic scoliosis who had a posterior spinal fusion withstanding 2-view, posteroanterior and lateral radiographs of the entire spine performed at first erect visit, 6, 12, and 24 months. To measure coronal balance, a C7PL was measured and compared with the CSVL. A negative value denotes the leftward deviation of the C7PL and a positive value a rightward deviation. The authors then created a novel coronal balance classification system.

RESULTS

A total of 954 patients met the inclusion criteria. There was a strong trend toward improving coronal balance, especially between first erect and 6 months; the proportion of out of balance patients declined throughout the 2-year period: preoperative 372 of 954 (39%), first erect 297 of 954 (31.1%), 6 months 167 of 954 (17.5%), 1 year 136 of 954 (14.3%), and 2 years 115 of 954 (12.0%). Analyzing the patients most out of balance immediately after posterior spinal fusion, 35 of 50 (70%) in group 3 regained balance by 2 years. Out of the remaining 15 patients, 12 corrected to group 1 (24%), 2 patients to group 2 (4%), and 1 patient remained in group 3 (2%).

CONCLUSIONS

This large, longitudinal postoperative study of coronal balance documents a strong trend toward postoperative rebalancing, with the largest gains between first erect image and 6 months. The 31% of patients out of balance at first erect declined to only 12.1% at 2 years.

EOS® imaging: Concept and current applications in spinal disorders

EOS® imaging is a proprietary imaging technology that was launched in 2007. Based on a gaseous particle detector with a multi-wire proportional chamber, it offers several advantages over other imaging modalities: low dose of radiation, ability to create 3D reconstructions, ability to conduct whole body imaging, high reproducibility in measuring various parameters of alignment and faster imaging time. EOS® imaging is slowly gaining widespread acceptance as its applications in various disorders continue to evolve. It has been found to be particularly useful and has opened up new avenues of research in the field of spinal deformities. This narrative review seeks to provide an overview of the proprietary technology behind EOS® imaging, compare it to existing imaging modalities, summarize its current applications in various spinal disorders and outline its limitations.

What are normal radiographic spine and shoulder balance parameters among adolescent patients?

STUDY DESIGN

Retrospective.

OBJECTIVES

To define normal values and distributions for sagittal, coronal, and shoulder balance among healthy adolescents, both for traditional radiographs and biplanar radiography. Our understanding of spine balance, especially in the sagittal plane, has expanded rapidly in recent years. Additionally, there has been growing use of simultaneous biplanar radiography which requires slightly different patient positioning. However, the normal ranges of several commonly used parameters have not yet been defined, either in traditional or biplanar radiography.

METHODS

Radiographs were retrospectively reviewed of 273 patients aged 10-18 years seen in spine clinics at two high-volume centers and not diagnosed with any spine pathology. One center utilized traditional radiography and the other biplanar radiography. Coronal, sagittal, and shoulder balance were measured for each patient. Intra-observer reliability and normal values with distributions were reported for each parameter.

RESULTS

Intra-observer reliability was excellent (intra-class correlation coefficients ≥ 0.98). Each parameter was normally distributed at each institution based on Kolmogorov-Smirnov testing. Sagittal balance was more negative at the institution using traditional radiographs (- 3.4 ± 4.2 vs. 0.3 ± 2.2, p < 0.001). Coronal balance was statistically, but not clinically, significantly more negative at this institution (- 0.6 ± 1.4 vs. - 0.2 ± 1.0, p = 0.007). Shoulder balance was not different between institutions. The "normal" ranges (mean ± 2 standard deviations, i.e., expected to include 95% of patients) were - 2.8 to 2.0 cm for coronal balance, - 9.0 to 6.1 cm for sagittal balance, and - 1.5-2.4 cm for shoulder balance.

CONCLUSIONS

In adolescents without known spine pathology, the mean coronal, sagittal, and shoulder balance is near neutral, but each parameter varies over a large range; so the average patient deviates from neutral by 1.0 ± 0.7 cm, 3.1 ± 2.6 cm, and 0.9 ± 0.7 cm, respectively. The most important difference between biplanar and traditional radiographs was a significantly more negative sagittal balance in the biplanar group which may be attributable to arm positioning.

LEVEL OF EVIDENCE

Level III.

Analysis of the Change Patterns of Sagittal Alignment Values After Selective Thoracic Fusion in Lenke 1 Adolescent Idiopathic Scoliosis According to Preoperative Thoracic Kyphosis Status

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

The objective of this study was to demonstrate the different change patterns in reciprocal sagittal alignment values after selective thoracic fusion (STF) in Lenke type 1 adolescent idiopathic scoliosis (AIS) according to preoperative thoracic kyphosis (TK).

SUMMARY OF BACKGROUND DATA

Several studies have found significant increase in TK after STF, while other studies have reported decrease in TK postoperatively. Similar inconclusive results on changes in lumbar lordosis (LL) have been reported, showing LL increase, decrease, or no change.

MATERIALS AND METHODS

Ninety-three patients presenting with Lenke type 1 AIS treated by posterior STF with a minimum follow-up of 2 years were included in this study. Using whole spine radiographs, sagittal parameters including TK, LL, and upper lumbar lordosis (ULL) were compared preoperatively and at the last follow-up between a hypokyphosis group (preoperative TK<20 degrees) and a normokyphosis group (preoperative TK≥20 degrees). Health-related quality of life (HRQOL) was assessed using scoliosis research society health-related quality of life-30 (SRS-30) and short from health survey-36 questionnaire at the last visit.

RESULTS

The mean follow-up duration was 74.9 months. In the hypokyphosis group (35 patients), TK, LL, and ULL statistically significantly increased after surgery by mean 7.7, 5.1, and 3.7 degrees (P<0.001, <0.001, and 0.001). In the normokyphosis group (58 patients), these parameters did not show significant changes after STF. Final TK was significantly lower in hypokyphosis group than that in the normokyphosis group (21.2 vs. 30.9 degrees, P<0.001) while final LL did not differ between 2 groups (52.4 vs. 54.6 degrees, P=0.194). HRQOL did not differ significantly between the 2 groups.

CONCLUSIONS

After STF in Lenke 1 AIS, TK, and LL statistically significantly increased through an increase in the mean ULL in the hypokyphosis group while those mean values did not change in the normokyphosis group. Despite the final mean value of the TK in the hypokyphosis group increasing by 7.7 degrees, it was statistically significantly lower than the final mean TK value in the normokyphosis group which did not increase after STF surgery by posterior approach. However, HRQOL showed no significant difference between the 2 groups.

A 10-Year Radiographic Study Comparing Anterior Versus Posterior Instrumented Spinal Fusion in Patients With Lenke Type 5 Adolescent Idiopathic Scoliosis

MINI: This is a long-term prospective cohort study comparing the radiographic outcomes of anterior versus posterior instrumentation for Lenke 5 adolescent idiopathic scoliosis. Both approaches were comparable in terms of radiographic outcomes up to 10 years. The posterior approach is more prone to developing proximal junctional kyphosis.

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To compare the long-term, radiographic coronal and sagittal outcomes of these two approaches at 10-year follow-up.

SUMMARY OF BACKGROUND DATA

Both anterior and posterior instrumented fusions have been found to be safe and effective treatments for Lenke 5 adolescent idiopathic scoliosis with up to 2 to 5 years of follow-up. Few studies follow patients beyond this duration.

METHODS

36 patients who underwent anterior (n = 25) or posterior instrumented spinal fusion (n = 11) for Lenke 5 adolescent idiopathic scoliosis over a 4-year period were recruited and followed for 10 years. Preoperative clinical data include patient's age and age of menarche. Operative data included instrumented levels, duration of surgery, and surgical blood loss. Postoperative data included duration of hospital stay, duration of intensive care unit stay, and complications. Pre- and postoperative radiographic data collected include coronal Cobb angles for structural thoracolumbar/lumbar curves, and sagittal angles-sagittal vertical axis, thoracic kyphosis, global lumbar angle, pelvic incidence, pelvic tilt, sacral slope, and upper and lower end vertebrae.

RESULTS

Posterior surgery had a shorter operative time (P < 0.010) and hospital stay (P < 0.010). Coronal plane deformity improved by a mean of 74% in the anterior group and 71% in the posterior group. There was no significant change at 10 years in both groups (anterior P = 0.455 and posterior P = 0.325). Sagittal parameters remained unchanged. There was a higher incidence of proximal junctional kyphosis in the posterior (45%) compared to the anterior (16%) group (P < 0.010).

CONCLUSION

Both anterior and posterior instrumentation and fusion are successful surgeries after 10 years of follow-up. They are comparable with regards to their ability to achieve and maintain good correction of scoliotic deformities and have a low rate of pseudoarthrosis and instrument failure. Ideal sagittal parameters are maintained up to 10 years of follow-up.

LEVEL OF EVIDENCE

3.

Sagittal Balance in Adult Idiopathic Scoliosis

STUDY DESIGN

A narrative review article study.

OBJECTIVE

The objective of this study was to highlight guiding principles and challenges faced with addressing sagittal alignment in patients with adult idiopathic scoliosis (AIS) and to discuss effective surgical strategies based upon our clinical experience.

SUMMARY OF BACKGROUND DATA

Previous research and guidelines for the treatment of AIS have focused on the correction of spinal deformity in the coronal and axial planes. Failure to address sagittal deformity has been associated with numerous adverse clinical outcomes.

METHODS

This is a review of the current body of literature and a description of the rod derotation surgical technique for correction in the sagittal plane.

RESULTS

Several studies have offered general goals for postoperative radiographic measures in the sagittal plane for patients with AIS. However, these guidelines are evolving as diagnostic and therapeutic modalities continue to improve. The rod derotation surgical technique through differential metal rods is one method to potentially address sagittal balance in AIS.

CONCLUSIONS

Alignment in the sagittal plane is a unique challenge facing surgeons for patients with AIS. Further research with an assessment of functional outcomes and longer follow-up is needed to more precisely guide treatment principles.

LEVEL OF EVIDENCE

Level IV.