Adult degenerative scoliosis – A literature review

The TLR-M-CSF axis is implicated in increased bone turnover and curve progression in adolescent idiopathic scoliosis

BACKGROUND

Facet joint osteoarthritis (OA) is prevalent in patients with adolescent idiopathic scoliosis (AIS). The most pronounced OA presents above and below the curve's apex where the intervertebral rotation is the greatest. This indicates that facet joint OA is implicated and potentially contributes to AIS progression. OA impacts both cartilage and bone and we have previously demonstrated an association between lower bone quality and more severe OA in AIS facet joints. This study aimed to further investigate the molecular mechanisms underlying cartilage-bone crosstalk in the facet joints of patients with AIS.

METHODS

Unbiased deep RNA sequencing was performed to compare gene expression in facet joint chondrocytes of age-matched AIS patients and non-scoliotic individuals. Differentially expressed genes of interest were validated through qPCR and ELISA in a larger sample cohort. Key regulatory pathways involved in cartilage-bone crosstalk were identified through bioinformatic analysis. Functional studies were conducted by treating chondrocytes with TLR2 and TLR4 agonists, collecting conditioned media, and administering it to an in vitro osteoclastogenesis model. The expression of M-CSF, a key regulatory factor influencing osteoclast proliferation, was measured in individual facet joint cartilage samples at different spinal levels and correlated with cartilage morphological grade and 3D structural parameters extracted from spine reconstruction.

RESULTS

One thousand four hundred twenty six upregulated genes were detected, and gene ontology analysis revealed a significant enrichment of the TLR pathway, and bone-regulating biological processes in AIS chondrocytes. TLR activation of AIS chondrocytes induced expression of bone-regulating factors, including M-CSF, a key regulator of osteoclast proliferation. Furthermore, secreted factors from AIS chondrocytes enhanced osteoclast proliferation and maturation, with a stronger effect observed following TLR pre-activation. Clinically, M-CSF expression was found to correlate strongly with increased OA severity and a greater degree of intervertebral axial rotation.

CONCLUSIONS

Together, our findings suggest that the TLR-M-CSF axis is implicated in osteoclastogenesis, resulting in increased bone turnover and may contribute to curve progression in AIS patients.

Efficacy and safety of long fusion versus short fusion in degenerative scoliosis: a systematic review and meta-analysis

BACKGROUND

This study aimed to evaluate the efficacy and safety of long fusion versus short fusion in patients with degenerative scoliosis.

METHODS

Databases were systematically searched up to June 2024. The authors applied Review Manager 5.4 to manage the data and perform the analysis.

RESULTS

After the selection of 611 studies from electronic databases, 13 studies were eligible for inclusion. These 13 studies included 1261 patients: 534 patients underwent long fusion, and 727 underwent short fusion. At baseline, the Cobb angle, coronal imbalance, and sagittal imbalance were greater in the long fusion group. There was no difference in the VAS back, Cobb angle, ODI, hospital stay, revision surgery, adjacent segment degeneration, sacral slope, pelvic tilt, Cobb angle, lumbar lordosis, coronal balance, or sagittal balance at the final follow-up. The surgery time, complication rates, and amount of blood loss were greater in the long fusion group.

CONCLUSIONS

Long fusion leads to superior radiographic improvement, particularly in reducing the Cobb angle and reconstructing coronal and sagittal balance. The long fusion group was inferior in terms of increased surgical time, more blood loss, and higher postoperative complication rates. At the final follow-up, there was no difference in the clinical or radiographic outcomes between the long and short groups. For patients with a large coronal Cobb angle and significant coronal or sagittal imbalance, long fusion surgery should be performed. On the other hand, for patients whose milder deformities and clinical symptoms are the main concern, short fusion surgery is recommended.

Incidence and Risk Factors of Lumbosacral Complications Following Long-Segment Spinal Fusion in Adult Degenerative Scoliosis

PURPOSE

Long-segment spinal fusions are associated with lumbosacral complications (LSC), but the associated risk factors are not known. This study aimed to identify the risk factors for LSC after long-segment instrumented fusion with distal fixation to the L5 vertebral body in adult degenerative scoliosis (ADS).

METHODS

We retrospectively evaluated 294 patients with ADS who underwent long-segment floating fusion between January 2014 and March 2022, with follow-up for at least 2 years. Patients were matched to the baseline data using fusion level > 5 as a grouping variable. Patients who completed matching were divided into two groups according to the presence or absence of LSC. Univariate logistic regression was applied to identify potential risk factors for LSC, and multivariate logistic regression was used to identify independent risk factors for postoperative LSC.

RESULTS

The overall incidence of LSC was 21.77% in the 294 patients, with disc degeneration in 28 (9.52%) and radiographic ASD in 44 (14.97%) patients. The mean time to LSC development after surgery was 26.91 ± 8.43 months. A total of 54 pairs of patients were matched and grouped, and the complication group had higher Oswestry Disability Index (ODI) and visual analog scale (VAS) scores at the last follow-up. Multivariate analysis showed that gender (OR = 0.274, p = 0.026 [0.087, 0.859]); levels of fusion > 5 (OR = 3.127, p = 0.029 [1.120, 8.730]), main curve correction rate (OR = 0.009, p = 0.005 [0.000, 0.330]), and postoperative pelvic incidence minus lumbar lordosis (PI-LL) > 15° (OR = 3.346, p = 0.022 [1.195, 9.373]) were independent risk factors for postoperative LSC. The area under the curve value of the prediction model was 0.804, with a 95% confidence interval of 0.715-0.892, indicating that the model had a high prediction accuracy. Collinearity statistics showed no collinearity between variables.

CONCLUSION

Sex, level of fusion > 5, main curve correction rate, and postoperative PI-LL > 15° were independent risk factors for the development of LSC after long-segment floating fusion. These results will improve our ability to predict personal risk conditions and provide better medical optimisation for surgery.

A novel method for assigning bone material properties to a comprehensive patient-specific pelvic finite element model using biplanar multi-energy radiographs

The increasing prevalence of adult spinal deformity requires long spino-pelvic instrumentation, but pelvic fixation faces challenges due to distal forces and reduced bone quality. Bi-planar multi-energy X-rays (BMEX) were used to develop a patient-specific finite element model (FEM) for evaluating pelvic fixation. Calibration involved 10 patients, and an 81-year-old female test case was used for FEM customization and pullout simulation validation. Calibration yielded a root mean square error of 74.7 mg/cm3 for HU. The simulation accurately replicated the experimental pullout test with a force of 565 N, highlighting the method's potential for optimizing biomechanical performance for pelvic fixation.

Characteristic of Paraspinal Muscle Change in Coronal Sub-type of Degenerative Lumbar Scoliosis and its Potential Clinical Significance

OBJECTIVE

Clarifying paraspinal muscle (PM) change in degenerative lumbar scoliosis (DLS) is positive to evaluate the progression of scoliosis. This research compares the characteristic of PM change among different coronal sub-types of DLS and explores its potential clinical significance.

METHODS

A total of 84 DLS patients between June 2019 to December 2021 were retrospectively analyzed. Patients were classified into three types based on the coronal balance distance (CBD): Type A, CBD <3 cm; Type B: C7 Plumb Line (C7PL) shifted to the concave side of the curve, and CBD >3 cm; Type C: C7PL shifted to the convex side of the curve, and CBD >3 cm. Fat infiltration rates in the multifidus (MS) and erector spinae (ES) at the apex of the main and fractional curves, and spinopelvic parameters were analyzed statistically. Pearson's or Spearman's correlation was applied to analyze the correlation between asymmetric degree of PM change and these parameters in three types.

RESULTS

There were 62 cases with coronal sub-Type A, 6 cases with Type B, and 16 cases with Type C. Patients in Type B and C demonstrated higher fat infiltration in MS on the concave side of both the main and fractional curves when compared to those in Type A. The asymmetric degree of ES change was positively correlated with CBD at the apex of the main curve in Type B and at the apex of the fractional curve in Type C respectively, and that of MS was positively correlated with apical vertebral rotation, while negatively strong-correlated with pelvic incidence and sacral slope in Type C.

CONCLUSION

PM fatty infiltration presented difference among varied coronal sub-types of DLS patients. The CBD in Type B and C patients was correlated with the asymmetric degree of ES change.

Developmental Patterns and Risk Factors of Scoliosis After Hemipelvectomy for the Pelvic Bone Tumor

BACKGROUND

Postoperative scoliosis is often seen after hemipelvectomy for malignancies involving the pelvic area, but the details remain unclear. The objectives were to investigate the development patterns and risk factors of scoliosis after hemipelvectomy.

METHODS

We retrospectively reviewed 30 patients who underwent hemipelvectomy at our hospital between 1998 and 2020. The risk factors of scoliosis with a Cobb angle of ≥10° were investigated.

RESULTS

The postoperative Cobb angle significantly increased in all patients compared with the preoperative one (p < 0.001), and the change ratio of the Cobb angle was significantly higher during the first postoperative year than thereafter. The external hemipelvectomy (EH) group demonstrated a larger Cobb angle and a higher change ratio than the internal hemipelvectomy group. Nine patients developed scoliosis with a final Cobb angle of ≥10°, and the risk factors were EH (p = 0.017), P1+2+3+4 resection according to the Enneking classification (p = 0.005), iliac crest resection (p = 0.004), L5/S resection (p = 0.020), and no pelvic ring reconstruction after hemipelvectomy (p = 0.004).

CONCLUSIONS

Approximately 30% of patients who underwent hemipelvectomy developed scoliosis with a Cobb angle of ≥10°, and this angle increased rapidly during the first postoperative year. Hence, careful follow-up of scoliosis is required after hemipelvectomy.

Optimization of S2-alar-iliac screw (S2AI) fixation in adult spine deformity using a comprehensive genetic algorithm and finite element model personalized to patient geometry and bone mechanical properties

PURPOSE

To optimize the biomechanical performance of S2AI screw fixation using a genetic algorithm (GA) and patient-specific finite element analysis integrating bone mechanical properties.

METHODS

Patient-specific pelvic finite element models (FEM), including one normal and one osteoporotic model, were created from bi-planar multi-energy X-rays (BMEXs). The genetic algorithm (GA) optimized screw parameters based on bone mass quality (BM method) while a comparative optimization method maximized the screw corridor radius (GEO method). Biomechanical performance was evaluated through simulations, comparing both methods using pullout and toggle tests.

RESULTS

The optimal screw trajectory using the BM method was more lateral and caudal with insertion angles ranging from 49° to 66° (sagittal plane) and 29° to 35° (transverse plane). In comparison, the GEO method had ranges of 44° to 54° and 24° to 30° respectively. Pullout forces (PF) using the BM method ranged from 5 to 18.4 kN, which were 2.4 times higher than the GEO method (2.1-7.7 kN). Toggle loading generated failure forces between 0.8 and 10.1 kN (BM method) and 0.9-2.9 kN (GEO method). The bone mass surrounding the screw representing the fitness score and PF of the osteoporotic case were correlated (R2 > 0.8).

CONCLUSION

Our study proposed a patient-specific FEM to optimize the S2AI screw size and trajectory using a robust BM approach with GA. This approach considers surgical constraints and consistently improves fixation performance.

Gastric Outlet Obstruction Secondary to Severe Thoracolumbar Scoliosis

A 78-year-old woman with a history of idiopathic thoracolumbar scoliosis presented with signs, symptoms, and imaging findings consistent with a gastric outlet obstruction secondary to the rib cage impinging on the pylorus of the stomach. She underwent an operative intervention and intra-operative findings were consistent with severe scoliosis with the right rib cage impinging on the pylorus, causing gastric outlet obstruction. A laparoscopic procedure was performed to pexy the greater curvature of the stomach to the left upper quadrant and a percutaneous endoscopic trans-gastric jejunostomy was inserted at the end. Thoracolumbar idiopathic scoliosis is a relatively benign common condition. However, with the increasing aging population and resultant higher incidence of progression to degenerative scoliosis, more patients are presenting with severe spinal and rib cage deformities that can cause rare intra-abdominal sequelae. We report the first case of a gastric outlet obstruction caused by the rib cage impinging on the pylorus in a patient with severe thoracolumbar scoliosis.

Identification of key genes and regulatory mechanisms in adult degenerative scoliosis

BACKGROUND

Adult degenerative scoliosis (ADS) is a spinal disorder, but its pathogenesis remain unclear. Therefore, in this study, we utilized data from the GEO database and explored the key genes and regulatory mechanisms involved in ADS.

METHODS

We performed bioinformatics analysis on the GSE209825 dataset of GEO database. Weighted gene co-expression network analysis (WGCNA) was used to identify ADS-related gene modules, and we performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. We constructed a protein-protein interaction (PPI) network using the STRING database. We validated the specificity of hub genes in ADS using the GSE34095 dataset and plotted ROC curves for the identification of different degenerative spinal diseases based on the hub genes expression RESULTS: We identified 113 differentially expressed lncRNAs. WGCNA identified the MEblack module had the strongest correlation to ADS. GO and KEGG analyses of target genes in lncRNAs revealed their involvement in immune responses, inflammation, cellular processes, and metabolic pathways. Through PPI and ROC analysis, 10 hub genes linked to ADS diseases with certain specificity were found: ELANE, LTF, DEFA1B, SLC2A4, DEFA1, FAXDC2, LCN2, CTSB, FDFT1, and AURKA.

CONCLUSIONS

We identified 10 potential hub genes associated with ADS and constructed a transcription factors (TFs)-lncRNAs-hub genes regulatory network. These findings provide a new direction and research basis for the targeted treatment and mechanism research of ADS.

Associations between Degenerative Lumbar Scoliosis Structures and Pain Distribution in Adults with Chronic Low Back Pain

BACKGROUND

This study aimed to investigate the location and distribution of pain in adults with chronic low back pain (LBP) with degenerative lumbar scoliosis (DLS) according to coronal deformities.

METHODS

We enrolled 100 adults with chronic LBP and DLS, dividing them into two groups, a right-convex DLS group (n = 50) and a left-convex DLS group (n = 50). Dominant pain location was analyzed by dividing it into three parts-left side, right side, and center-and pain areas were identified using the pain drawing method; then, a heat map was created for each group. An association between pain location and convex side was analyzed as the primary outcome. Additionally, we assessed pain characteristics and radiological parameters, such as the curve structure and degree of degeneration. We used the Mann-Whitney U test or the chi-squared test to compare the clinical characteristics of the two groups, and generalized linear models were utilized to determine which variables were associated with pain severity or pain area.

RESULTS

The results indicated that there was no significant difference between the two groups in terms of the association between the curve structure, pain severity and location. In multivariate analysis, although we did not find any variables associated with pain severity, we observed that age and a left-convex DLS were negatively correlated with pain area among all participants. The heat map demonstrated that individuals with chronic LBP frequently experienced pain in the central lumbar region, regardless of the coronal curve structure.

CONCLUSIONS

Our findings suggest that degenerative coronal lumbar deformities may not have a specific pain pattern associated with a curved structure.

RNA-Seq Comprehensive Analysis Reveals the Long Noncoding RNA Expression Profile and Coexpressed mRNA in Adult Degenerative Scoliosis

Objective: Owing to the intensification of the aging process worldwide, the prevalence of adult degenerative scoliosis (ADS) is increasing at an alarming rate. However, genomic research related to the etiology of ADS is rarely reported worldwide. Since long noncoding RNAs (lncRNAs) play a pivotal role in the progression of human diseases, this study aimed to investigate ADS-associated messenger RNAs (mRNAs) and lncRNAs by RNA sequencing (RNA-seq), as well as performed comprehensive bioinformatics analysis based on the lncRNA–mRNA coexpression network and protein–protein interaction (PPI) network.

Methods: Initially, six whole blood (WB) samples were obtained from three ADS and three nondegenerative lumbar trauma patients who underwent surgical operation for RNA-seq exploration to construct differential mRNA and lncRNA expression profiles. Subsequently, quantitative RT-PCR (qRT-PCR) was performed to validate three randomly selected differentially expressed mRNAs and lncRNAs derived from the nucleus pulposus (NP) tissue of 14 other subjects (seven ADS patients and seven nondegenerative lumbar trauma patients), respectively.

Results: A total of 1,651 upregulated and 1,524 downregulated mRNAs and 147 upregulated and 83 downregulated lncRNAs were screened out from the RNA-Seq data, which constructed coexpression networks to investigate their regulatory interactions further. GO gene function prediction revealed that lncRNA-targeted genes might play a vital role in ADS via participation in multiple biological processes such as the AMPK signaling pathway, lysosomes, and ubiquitin-mediated proteolysis, as well as cellular metabolic processes. Moreover, the expression levels of three selected lncRNAs and mRNAs were validated by qRT-PCR, respectively, demonstrating that the relative expression levels were consistent with the RNA-seq data. Notably, the dysregulated RNAs, AKT1, UBA52, PTPN12, and CLEC16A, were significantly differentially expressed in ADS WB samples and might serve as potentially regulated genes for research in the future.

Conclusions: This study provides the first insight into the altered transcriptome profile of long-stranded noncoding RNAs associated with ADS, which paves the way for further exploration of the clinical biomarkers and molecular regulatory mechanisms for this poorly understood degenerative disease. However, the detailed biological mechanisms underlying these candidate lncRNAs in ADS necessitate further elucidation in future studies.

The role of sagittal pelvic morphology in the development of adult degenerative scoliosis

PURPOSE

Pelvic morphology dictates the alignment and biomechanics of the spine. Recent observations in different types of adolescent idiopathic scoliosis indicate that individual pelvic morphology is related to the spinal levels in which scoliosis develops: primary lumbar adolescent scoliosis is associated with a higher pelvic incidence (PI) than thoracic scoliosis and non-scoliotic controls. We hypothesize that adult degenerative scoliosis (ADS) of the lumbar spine follows the same mechanical principles and is associated with a high PI.

METHODS

This study used an existing CT-scan database, 101 ADS patients were sex and age matched to 101 controls. The PI was measured by two observers with multi-planar reconstruction, perpendicular to the hip-axis according to a previously validated technique.

RESULTS

The PI was 54.1° ± 10.8° in ADS patients and 47.7° ± 10.8° in non-scoliotic controls (p < 0.001). The median ADS curve apex was the disc L2-3 and median curve length was 4 vertebral levels. The mean supine Cobb angle was 21° ± 8° (ranged 10°-47°). There was no significant correlation between PI and the apex level (p = 0.883), the curve length (p = 0.418) or the Cobb angle (p = 0.518).

CONCLUSIONS

ADS normally develops de novo in the lumbar spine of patients with a higher PI than controls, similar to primary lumbar adolescent idiopathic scoliosis. This suggests a shared mechanical basis of both deformities. Pelvic morphology dictates spinal sagittal alignment, which determines the segments of the spine that are prone to develop scoliosis.