What Factors Are Associated With Kyphosis Restoration in Lordotic Adolescent Idiopathic Scoliosis Patients?

The effect of the caudal insertion angle of pedicle screws on postoperative thoracic kyphosis in adolescent idiopathic scoliosis: a pilot study

The study was a prospective analysis of collected data to compare the effect of the insertion angle (parallel or oblique relative to the upper-end plates) of thoracic pedicle screws on postoperative thoracic kyphosis in patients with idiopathic thoracic scoliosis. This study was conducted on idiopathic adolescent scoliosis (AIS) patients. Two groups of patients were defined according to the insertion angle of thoracic pedicle screws in relation to the upper-end plate of the corresponding vertebra, the insertion angles being either oblique or parallel. Seven consecutive AIS patients were compared in each group. Pre- and postoperative standing X-rays were obtained. Cobb's angles, sagittal parameters such as thoracic kyphosis (TK) (T1-T12) and lumbar lordosis (LL) (L1-S1) were all measured. The average of the main curve or compensatory curve corrections showed no significant differences between the two groups. From a sagittal profile perspective, the mean TK in the oblique screw group was 39.3 ± 11.5 preoperatively, which was reduced to 30.9 ± 6.41 after surgery. The mean TK in the parallel group was 36.4 ± 14 preoperatively and 42.1 ± 13.9 postoperatively. There was a significant reduction in TK in the oblique screws group compared with the second group ( P  = 0.038). The insertion angle of pedicle screws had no significant effect on Cobb's angle and lumbar lordosis changes. However, oblique insertion of thoracic screws decreased thoracic kyphosis postoperatively, which could be considered a negative point. As such, the insertion of thoracic screws in a caudal direction should not be routinely used because of its lordogenic effect.

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.

Systematic review and meta-analysis for the impact of rod materials and sizes in the surgical treatment of adolescent idiopathic scoliosis

PURPOSE

To assess surgical and safety outcomes associated with different rod materials and diameters in adolescent idiopathic scoliosis (AIS) surgery.

METHODS

A systematic literature review and meta-analysis evaluated the surgical management of AIS patients using pedicle screw fixation systems (i.e., posterior rods and pedicle screws) with rods of different materials and sizes. Postoperative surgical outcomes (e.g., kyphosis and coronal correction) and complications (i.e., hyper/hypo-lumbar lordosis, proximal junctional kyphosis, revisions, reoperations, and infections) were assessed. Random-effects models (REMs) pooled data for outcomes reported in ≥ 2 studies.

RESULTS

Among 75 studies evaluating AIS surgery using pedicle screw fixation systems, 46 described rod materials and/or diameters. Two studies directly comparing titanium (Ti) and cobalt-chromium (CoCr) rods found that CoCr rods provided significantly better postoperative kyphosis angle correction vs. Ti rods during a shorter follow-up (0-3 months, MD = - 2.98°, 95% CI - 5.79 to - 0.17°, p = 0.04), and longer follow-up (≥ 24 months, MD = - 3.99°, 95% CI - 6.98 to - 1.00, p = 0.009). Surgical infection varied from 2% (95% CI 1.0-3.0%) for 5.5 mm rods to 4% (95% CI 2.0-7.0%) for 6 mm rods. Reoperation rates were lower with 5.5 mm rods 1% (95% CI 0.0-3.0%) vs. 6 mm rods [6% (95% CI 2.0-9.0%); p = 0.04]. Differences in coronal angle, lumbar lordosis, proximal junctional kyphosis, revisions, and infections did not differ significantly (p > 0.05) among rods of different materials or diameters.

CONCLUSION

For AIS, CoCr rods provided better correction of thoracic kyphosis compared to Ti rods. Patients with 5.5 mm rods had fewer reoperations vs. 6.0 and 6.35 mm diameter rods.

LEVEL OF EVIDENCE

III.

The Sagittal Plane in Spinal Fusion for Adolescent Idiopathic Scoliosis

Sagittal balance is widely recognized as the primary determinant of optimal outcomes in adult spinal deformity. In adolescent idiopathic scoliosis (AIS), coronal correction risks being obtained at the expense of sagittal malalignment after posterior spinal fusion. Apical lordosis, often underestimated on two-dimensional imaging, is the primary deforming factor in AIS. Failure to restore thoracic kyphosis and lumbar lordosis during posterior spinal fusion contributes to problematic early surgical complications, including proximal or distal junctional kyphosis and failure. Although adolescent patients often compensate for sagittal imbalance in the short-term and mid-term, late sequelae of iatrogenic sagittal imbalance include flatback syndrome, disk degeneration, cervical kyphosis, and late decompensation. Objective criteria using spinopelvic parameters and preoperative three-dimensional planning can guide sagittal plane correction during PSF for AIS. Technical caveats can help avoid sagittal plane complications, including instrumentation level selection, anchor type, and anatomic protection of adjacent levels. Other surgical techniques to optimize restoration of thoracic kyphosis include higher implant density, stiffer rod material, Ponte osteotomies, and deformity correction technique.

Evaluating flexibility and predicting curve correction using fulcrum-bending radiographs in Lenke type 2 adolescent idiopathic scoliosis

BACKGROUND

Fulcrum-bending (FB) correction is considered to provide the best estimation of main thoracic (MT) curve flexibility and postoperative correction in surgical treatment for adolescent idiopathic scoliosis (AIS). However, few studies evaluated the usefulness of FB radiographs for proximal thoracic (PT) curve. We aimed to perform flexibility assessments using both active side-bending (SB) and FB radiographs and evaluate surgical outcomes after posterior spinal fusion (PSF) for Lenke type 2 AIS.

METHODS

This study included 38 consecutive patients with Lenke type 2 AIS who underwent PSF using a pedicle screw construct with a minimum 2-year follow-up. Radiographic parameters, including correction rate, SB and FB flexibility, and FB correction index (FBCI: [correction rate/FB flexibility] × 100), were evaluated preoperatively, immediately after surgery, and at the 2-year follow-up. The clinical outcomes were preoperatively evaluated using the Scoliosis Research Outcomes Instrument-22 and at the follow-up.

RESULTS

All scoliosis curves significantly improved and shoulder balance shifted toward left shoulder elevation (all comparisons, p < 0.0001). There were significant differences between the SB and FB corrections in the PT and MT curves (p < 0.0001). The magnitudes of the discrepancies between the SB and FB corrections in the PT and MT curves were 11.2° ± 5.2° and 11.6° ± 7.2°, respectively. FB correction did not differ from postoperative Cobb angles correction immediately after surgery or at the 2-year follow-up; the mean FBCIs in the PT and MT curves were 98.8% and 105.5%, respectively. The self-image domain SRS-22 scores had significantly increased at the 2-year follow-up (p < 0.0001).

CONCLUSIONS

There were significant differences between the SB and FB corrections, and FB correction tended to approximate the postoperative curve correction (FBCI = 100%) for PT and MT curves in patients with Lenke type 2 AIS. FB flexibility is more reliable than SB flexibility in evaluating actual curve flexibility even for the PT curve.

Maximizing mechanical advantage: surgical technique increases stiffness in spinal instrumentation

PURPOSE

While there has been a great improvement in the treatment of adolescent idiopathic scoliosis, sagittal deformity correction has remained challenging. Increased rod stiffness has been shown to reduce thoracic flattening. We propose that the surgical technique can increase rod stiffness. A mechanical study was created to quantify the effect this has on construct stiffness.

METHODS

The sagittal bending stiffness of a constrained over contoured rod was measured using four different commonly used instrumentation systems. Pedicle screws were secured into custom printed blocks. One block was completely immobilized, while the other block was subject to four levels of constraint. This includes no constraint, mild constraint, moderate constraint, and maximal constraint with both blocks immobilized. The rod apex was loaded until 1 cm of displacement occurred. The stiffness was then calculated and compared between groups.

RESULTS

All four rod types showed increased bending stiffness as the construct became more constrained. The moderately constrained and the maximally constrained groups had a significantly higher stiffness compared to the unconstrained groups in all rod types (p < 0.05). The 6.0 mm titanium circular rods showed the highest increase in stiffness between maximal and no constraint, which became 3.02 × stiffer.

CONCLUSIONS

Rod stiffness is not only determined by size, shape, and metal alloy, but also by surgical technique. Constraining the spinal instrumentation by first locking the rod to the proximal and distal anchors significantly increases the sagittal bending stiffness. In a mechanical model this technique increases rod bending stiffness regardless of the material or shape.

Staged Corrective Surgery for a Patient With Sagittal Malalignment Related to Noonan Syndrome: A Case Report

CASE

A 20-year-old man with Noonan syndrome had rigid cervical kyphosis caused by cervical myelopathy and thoracic lordosis caused by pulmonary disfunction. Two-staged corrective surgery, which involved initial posterior spinal fusion (PSF) in T2-L2 followed by PSF in C3-T2, had been performed without any complications. The radiographs before surgery and 2 years after surgery showed that cervical lordosis (C2-7) changed form -56° to -29°, and thoracic kyphosis (T5-12) improved from -49° to 10°.

CONCLUSION

Initial realignment surgery in the caudal lesion should be better for improving global spinal alignment in patients with rigid spinal deformities at different locations.

PRE- AND POSTOPERATIVE COMPARATIVE ANALYSIS OF THE SPINOPELVIC AND GLOBAL SAGITTAL PARAMETERS OF PATIENTS WITH ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Objective: To analyze the pre- and postoperative spinopelvic parameters and global sagittal balance of patients with adolescent idiopathic scoliosis (AIS) divided into 3 groups (Group 1 – thoracic arthrodesis, Group 2 - thoracolumbar arthrodesis, and Group 3 – lumbar arthrodesis), observing differences in these two moments and whether the parameter values are maintained or not over a period of up to 2 years following surgery. Methods: We analyzed the radiographs from a single-center database of 99 patients who underwent arthrodesis with posterior instrumentation. Pelvic incidence, pelvic version, sacral slope, lumbar lordosis, thoracic kyphosis, and sagittal vertical axis values were measured in the pre- and postoperative radiographies of each patient. Results: The parameters of pelvic incidence, pelvic version, sacral slope, and sagittal vertical axis did not show statistically significant differences among the 3 groups. There was a difference in preoperative lumbar lordosis between the 3 groups (p = 0.049). Thoracic kyphosis showed differences both in the pre- (p = 0.015) and postoperative (p = 0.042) values, in addition to demonstrating a relationship of dependence between the pre- and postoperative values in the final statistical analysis. Conclusion: The evaluation of the parameters analyzed shows that the study groups have similar values of individual balance, with the exception of thoracic kyphosis and lumbar lordosis, which are measurements that depend on the surgical technique and compensatory mechanisms, but remained within normal ranges. These factors allow the surgeon to be attentive to both the coronal and sagittal planes when planning the correction in order to achieve the equilibrium of the trunk in addition to correction of the deformity. Level of Evidence IIIA: Comparative retrospective study.

Does use of pre-operative low-dose CT-scan in adolescent idiopathic scoliosis improve accuracy in screw placement? Results of a retrospective study

PURPOSE

To evaluate the efficacy of pre-operative low-dose radiation computed tomography (CT) in optimizing screw placement in patients with adolescent idiopathic scoliosis (AIS).

METHODS

49 patients with AIS who required correction and posterior fusion between January 2018 and December 2019 were included in this retrospective study. All patients underwent surgery performed by the same team of experienced surgeons. Patients were divided in two groups. The study group received a pre-operative low-dose CT scan (CT group, n = 25), differently from the control group (CG, n = 24). Patients of both groups received a post-operative low-dose CT scan. The primary outcome measure was the accuracy of screw placement on the Gertzbein-Robbins scale (grades A and B were considered acceptable). Secondary outcome measures included a comparison of perioperative complications.

RESULTS

A total of 1045 screws were placed. In CT group (n = 25, screws = 528) and CG (n = 24, screws = 517), trajectories were grade A or B in 94.5% and 93.6% of screws, respectively. Two screws (one for each group) were removed because of intra-operative-evoked potentials alteration and one screw required revision after post-operative imaging. No correlation was found between the malpositioning rate and the proximity to the apex of the curve, conversely a significative peak of misplacements was observed at T3 (p < 0.01). No neurological and vascular complications related to screw placement were recorded. There was not intergroup difference neither in screw accuracy (Chi-Square, 2-tailed Fisher's exact, p = 0.63), nor in complications rate.

CONCLUSION

Pre-operative low-dose CT scan as surgical plan does not contribute in reducing pedicle screw misplacement rate.

STUDY DESIGN

Retrospective comparative cohort study.

LEVEL OF EVIDENCE

III.

True 3D parameters of the spinal deformity in adolescent idiopathic scoliosis

BACKGROUND

Spinal deformities in adolescent idiopathic scoliosis (AIS) are measured on 2D radiographs. Due to the 3D nature of the curve in AIS, such 2D measurements fail to differentiate between the true curve patterns, which in turn may adversly impact the clinical care and surgical planning. The use of 3D models of the spinal radiographs largely remains limited to the 3D measurements of the 2D parameters. The use of the true 3D variables of the spinal curves in describing the differences between the AIS patients is not fully explored.

METHODS

A cohort of 141 Lenke 1 AIS with two-view spinal stereoradiographs and 3D models of the spines were included. The 3D model of the spine was used to determine the spinal centerlines. The writhe and torsion of the 3D centerlines, which, respectively, quantify the coiling and twist of the curve, were calculated using differential geometry. Patients were clustered based on the writhe and torsion values to determine the patient groups with significantly different 3D curve characteristics. The relationship between the writhe and torsion was statistically determined. The distribution of the writhe and torsion groups between the lumbar modifier types was determined.

RESULTS

Two writhe and two torsion clusters were determined. Lumbar orientation of plane of maximum curvature (PMC) was significantly different between the torsion clusters and thoracic and lumbar PMC and thoracic Cobb angles were significantly different between the writhe groups, p < 0.05. More than 50% of the patients had high writhe and low torsion except for Lumbar modifier C that mainly belonged to the low writhe group.

DISCUSSION

Two geometrical parameters of the spinal centerline determine true 3D characteristics of the scoliotic curves. The parameters were complimentary and weakly correlated, quantifying different characteristics of the scoliotic spines.

Machine Learning Predicts the 3D Outcomes of Adolescent Idiopathic Scoliosis Surgery Using Patient-Surgeon Specific Parameters

STUDY DESIGN

Retrospective descriptive, multicenter study.

OBJECTIVE

The aim of this study was to predict the three-dimensional (3D) radiographic outcomes of the spinal surgery in a cohort of adolescent idiopathic scoliosis (AIS) as a function preoperative spinal parameters and surgeon modifiable factors.

SUMMARY OF BACKGROUND DATA

Current guidelines for posterior spinal fusion surgery (PSF) in AIS patients are based on two-dimensional classification of the spinal curves. Despite the high success rate, the prediction of the 3D spinal alignment at the follow-ups remains inconclusive. A data-driven surgical decision-making method that determines the combination of the surgical procedures and preoperative patient specific parameters that leads to a specific 3D global spinal alignment outcomes at the follow-ups can lessen the burden of surgical planning and improve patient satisfaction by setting expectations prior to surgery.

METHODS

A dataset of 371 AIS patients who underwent a PSF with two-year follow-up were included. Demographics, 2D radiographic spinal and pelvic measurements, clinical measurements of the trunk shape, and the surgical procedures were collected prospectively. A previously developed classification of the preoperative global 3D spinal alignment was used as an additional predictor. The 3D spinal alignment (vertebral positions and rotations) at two-year follow-up was used as the predicted outcome. An ensemble learner was used to predict the 3D spinal alignment at two-year follow-up as a function of the preoperative parameters with and without considering the surgeon modifiable factors.

RESULTS

The preoperative and surgical factors predicted three clusters of 3D surgical outcomes with an accuracy of 75%. The prediction accuracy decreased to 64% when only preoperative factors, without the surgical factors, were used in the model. Predictor importance analysis determined that preoperative distal junctional kyphosis, pelvic sagittal parameters, end-instrumented vertebra (EIV) angulation and translation, and the preoperative 3D clusters are the most important patient-specific predictors of the outcomes. Three surgical factors, upper and lower instrumented vertebrae, and the operating surgeon, were important surgical predictors. The role of surgeon in achieving a certain outcome clusters for specific ranges of preoperative T10-L2 kyphosis, EIV angulation and translation, thoracic and lumbar flexibilities, and patient's height was significant.

CONCLUSION

Both preoperative patient-specific and surgeon modifiable parameters predicted the 3D global spinal alignment at two-year post PSF. Surgeon was determined as a predictor of the outcomes despite including 20 factors in the analysis that described the surgical moves. Methods to quantify the differences between the implemented surgeon modifiable factors are essential to improve outcome prediction in AIS spinal surgery.Level of Evidence: 3.

Tracheal stenosis due to cervicothoracic hyperlordosis in patients with cerebral palsy treated with posterior spinal fusion: a report of the first two cases

Background

Spinal deformity is frequently identified in patients with cerebral palsy (CP). As it progresses, tracheal stenosis often develops due to compression between the innominate artery and anteriorly deviated vertebrae at the apex of the cervicothoracic hyperlordosis. However, the treatment strategy for tracheal stenosis complicated by spinal deformity in patients with CP remains unknown.

Case presentation

This study reports two cases: a 19-year-old girl (case 1) and a 17-year-old girl (case 2), both with CP at Gross Motor Function Classification System V. Both patients experienced acute oxygen desaturation twice within the past year of their first visit to our department. X-ray and computed tomography revealed severe scoliosis and cervicothoracic hyperlordosis causing tracheal stenosis at T2 in case 1 and at T3-T4 in case 2, suggesting that their acute oxygen desaturation had been caused by impaired airway clearance due to tracheal stenosis. After preoperative halo traction for three weeks, both patients underwent posterior spinal fusion from C7 to L5 with Ponte osteotomy and sublaminar taping at the proximal thoracic region to correct cervicothoracic hyperlordosis and thoracolumbar scoliosis simultaneously. Postoperative X-ray and computed tomography revealed that the tracheal stenosis improved in parallel with the correction of cervicothoracic hyperlordosis. Case 1 did not develop respiratory failure 1.5 years after surgery. Case 2 required gastrostomy postoperatively due to severe aspiration pneumonia. However, she developed no respiratory failure related to impaired airway clearance at one-year follow-up.

Conclusions

We present the first two cases of CP that developed tracheal stenosis caused by cervicothoracic hyperlordosis concomitant with progressive scoliosis and were successfully treated by posterior spinal fusion from C7 to L5. This enabled us to relieve tracheal stenosis and correct the spinal deformity at the same time. Surgeons must be aware of the possibility of coexisting tracheal stenosis in treating spinal deformity in patients with neurological impairment because the surgical strategy can vary in the presence of tracheal stenosis. This study demonstrated that some patients with CP with acquired tracheal stenosis can be treated with spinal surgery.

Willingness to enroll in a surgical randomized controlled trial: patient and parent preferences regarding implant density for adolescent idiopathic scoliosis fusion

STUDY DESIGN

Prospective survey of adolescent idiopathic scoliosis (AIS) patients/parents with surgical magnitude curves.

OBJECTIVE

We hypothesized that patients and families considering fusion surgery would be willing to enroll in a randomized controlled trial (RCT) evaluating the effect of number of implants on curve correction. Surgical RCTs are infrequently performed, particularly in a pediatric population. Parental willingness to enroll affects both study design and trial feasibility. The Minimize Implants Maximize Outcomes (MIMO) Clinical Trial proposes to randomize patients to more versus fewer screws (high or low density) for Lenke 1A curve patterns, but it is unclear whether families and patients are willing to enroll in such a trial.

METHODS

This study was undertaken at 4 of the 14 sites participating in the MIMO Clinical Trial. AIS patients with Cobb > 45° were included. Implant density is defined as screws per level fused. Patients and families reviewed the MIMO education module describing proposed advantages and disadvantages of high (> 1.8) vs. low (< 1.4) density screw constructs and completed a custom survey regarding their preferences about the trial.

RESULTS

159 individuals were surveyed (78 families), including 82 parents/guardians, and 77 patients. Of those surveyed, 95% mostly or completely understood the trial (range 47-78%), and 63% agreed to enroll. Parents and patients who completely understood the trial were significantly more likely to enroll.

CONCLUSION

Randomization in the MIMO Trial was acceptable to the majority (63%) of patients and parents. Clear patient and parent education materials and access to the surgeon may facilitate enrollment in the trial. Parents afforded the child much autonomy when considering enrollment, although most families agree both child and parent should be in agreement before entering the trial.

LEVEL OF EVIDENCE

II.