Modified Global Alignment and Proportion Scoring With Body Mass Index and Bone Mineral Density Analysis in Global Alignment and Proportion Score of Each 3 Categories for Predicting Mechanical Complications After Adult Spinal Deformity Surgery

Cost Benefit of Implementation of Risk Stratification Models for Adult Spinal Deformity Surgery

STUDY DESIGN/SETTING

Retrospective cohort study.

OBJECTIVE

Assess the extent to which defined risk factors of adverse events are drivers of cost-utility in spinal deformity (ASD) surgery.

METHODS

ASD patients with 2-year (2Y) data were included. Tertiles were used to define high degrees of frailty, sagittal deformity, blood loss, and surgical time. Cost was calculated using the Pearl Diver registry and cost-utility at 2Y was compared between cohorts based on the number of risk factors present. Statistically significant differences in cost-utility by number of baseline risk factors were determined using ANOVA, followed by a generalized linear model, adjusting for clinical site and surgeon, to assess the effects of increasing risk score on overall cost-utility.

RESULTS

By 2 years, 31% experienced a major complication and 23% underwent reoperation. Patients with ≤2 risk factors had significantly less major complications. Patients with 2 risk factors improved the most from baseline to 2Y in ODI. Average cost increased by $8234 per risk factor (R2 = .981). Cost-per-QALY at 2Y increased by $122,650 per risk factor (R2 = .794). Adjusted generalized linear model demonstrated a significant trend between increasing risk score and increasing cost-utility (r2 = .408, P < .001).

CONCLUSIONS

The number of defined patient-specific and surgical risk factors, especially those with greater than two, were associated with increased index surgical costs and diminished cost-utility. Efforts to optimize patient physiology and minimize surgical risk would likely reduce healthcare expenditures and improve the overall cost-utility profile for ASD interventions.Level of evidence: III.

The Association of Bone Mineral Density with Distal Junctional Kyphosis and Distal Junctional Failure After Multilevel Spine Fusions: A Systematic Review and Meta-Analysis

BACKGROUND

Distal junctional kyphosis (DJK) and distal junctional failure (DJF) are known complications of adult multilevel spinal fusion surgery. Previous literature has extensively investigated proximal junctional kyphosis and proximal junctional failure, but DJK and DJF are relatively understudied. This study investigates the association between bone mineral density (BMD) and DJK/DJF via a systematic review and meta-analysis.

METHODS

A literature search was conducted across PubMed, Cochrane, Web of Science, Embase, and Scopus to find studies reporting DJK, DJF, and BMD. A 12-month minimum follow-up and radiographic biomarker for BMD (Hounsfield units [HU] or a T-score) individually reported for each patient type were required for inclusion. Studies that did not report individualized biomarkers but provided averaged estimates of the effect of BMD on DJK/DJF development were used for systematic review.

RESULTS

Our search yielded 12 unique studies with 1094 patients, of which 5 studies with a total of 519 patients were suitable for comparison by meta-analysis. Patients who developed DJK/DJF had significantly lower HUs (113.17 ± 33.86) than patients who did not develop DJK/DJF (142.51 ± 41.39). No significant difference was found with regard to dual-energy X-ray absorptiometry measurements, age, or body mass index between patients who did and did not develop DJK/DJF.

CONCLUSIONS

Patients who developed DJK/DJF had significantly lower computed tomography-measured HU as compared to those without DJK/DJF. Our findings highlight the potential importance of BMD evaluation with computed tomography prior to multilevel spine fusion surgery, though further research would be helpful to evaluate the significance of dual-energy X-ray absorptiometry-based BMD measurements on DJK/DJF development.

Predicting postoperative mechanical complications with the ethnicity-adjusted global alignment and proportion score in degenerative scoliosis: does paraspinal muscle degeneration matter?

BACKGROUND

The global alignment and proportion (GAP) score was developed to predict mechanical complications (MCs) after adult spinal deformity surgery but showed limited sensitivity in the Asian population. Considering variations in sagittal parameters among different ethnic groups, our team developed the ethnicity-adjusted GAP score according to the spinopelvic parameters of 566 asymptomatic Chinese volunteers (C-GAP score). Notably, degenerative scoliosis (DS) patients with MCs following corrective surgery have more severe paraspinal muscle degeneration. For DS patients with various sagittal alignments, the unevenly distributed degeneration of paraspinal muscle may exert different influences on MC occurrence and largely affect the accuracy of the C-GAP score in clinical assessment. Therefore, incorporating paraspinal muscle degeneration indices within the C-GAP score may improve its accuracy in predicting MC occurrence.

PURPOSE

We aimed to clarify the influence of paraspinal muscle degeneration on the C-GAP score predicting MC occurrence following DS surgery and modify the C-GAP score with paraspinal muscle degeneration parameters.

STUDY DESIGN

A retrospective case-control study.

SAMPLE SIZE

A total of 107 adult degenerative scoliosis patients.

OUTCOME MEASURES

Demographic information, postoperative sagittal spinopelvic parameters, the GAP score, the C-GAP score, and paraspinal muscle degeneration parameters.

METHODS

A total of 107 DS patients undergoing posterior spinal fusion surgery (≥4 vertebrae) with a minimum of 2 years follow-up (or experiencing MCs within 2 years) were retrospectively reviewed. Their C-GAP score was calculated based on our previous study and patients were divided into 3 C-GAP categories, "proportioned" (P), "moderately disproportioned" (MD), and "severely disproportioned" (SD). Relative cross-sectional area (cross-sectional area of muscle-disc ratio×100, rCSA) and fat infiltration rate, FI% at L1/2, L2/3, L3/4, and L4/5 discs were quantitatively evaluated using magnetic resonance imaging (MRI). In each C-GAP category, patients were additionally divided into the MC group and the non-MC group to analyze their paraspinal muscle degeneration. A multivariable logistic regression model consisting of the CSA-weighted average FI% (total FI%) and the C-GAP score, C-GAPM was constructed. The area under the curve (AUC) of the receiver operating characteristic (ROC) curves was used to evaluate the predictability of the GAP score, the C-GAP score, FI%, and C-GAPM. This project was supported by the National Natural Science Foundation of China (No.82272545) and Special Fund of Science and Technology Plan of Jiangsu Province (No.BE2023658).

RESULTS

For all 107 patients, FI% at L1/2, L2/3, L3/4, and L4/5 discs and the total FI% of the MC group (n=32) were significantly higher than those of the non-MC group (n=75). The MC rates of 3 original GAP categories, P, MD, and SD categories were 25.00% (6/24), 27.03%(10/37), and 34.78% (16/46) (χ2=0.944, p=.624). Based on the C-GAP score, the MC rates of the P, MD, and SD categories were 11.90% (5/42), 34.69% (17/49), and 62.50% (10/16), showing significant differences (χ2=15.137, p=.001). In the C-GAP MD category, compared with the non-MC group (n=32), the MC group (n=17) has a higher total FI% (26.16(22.95, 34.00) vs 22.67(16.39, 27.37)), p=.029). A similar trend was identified in the C-GAP SD category (34.79±11.56 vs 19.00±5.17, p=.007), but not in the C-GAP P category (25.09(22.82, 32.66) vs 24.66(17.36, 28.63), p=.361). The AUC of the GAP score, the C-GAP score, the total FI%, and C-GAPM were respectively 0.601, 0.722, 0.716, and 0.772.

CONCLUSIONS

Paraspinal muscle degeneration exerts a significant effect on the occurrence of MC in the C-GAP MD, SD instead of P category. The integration of paraspinal muscle FI% with the C-GAP score (C-GAPM) enables a more accurate prediction of MCs following DS surgery. Surgeons should pay adequate attention to paraspinal muscle degeneration during surgical planning and postoperative management for patients in the C-GAP MD and SD categories.

The T4-L1-Hip Axis: Sagittal Spinal Realignment Targets in Long-Construct Adult Spinal Deformity Surgery: Early Impact

BACKGROUND

Our understanding of the relationship between sagittal alignment and mechanical complications is evolving. In normal spines, the L1-pelvic angle (L1PA) accounts for the magnitude and distribution of lordosis and is strongly associated with pelvic incidence (PI), and the T4-pelvic angle (T4PA) is within 4° of the L1PA. We aimed to examine the clinical implications of realignment to a normal L1PA and T4-L1PA mismatch.

METHODS

A prospective multicenter adult spinal deformity registry was queried for patients who underwent fixation from the T1-T5 region to the sacrum and had 2-year radiographic follow-up. Normal sagittal alignment was defined as previously described for normal spines: L1PA = PI × 0.5 - 21°, and T4-L1PA mismatch = 0°. Mechanical failure was defined as severe proximal junctional kyphosis (PJK), displaced rod fracture, or reoperation for junctional failure, pseudarthrosis, or rod fracture within 2 years. Multivariable nonlinear logistic regression was used to define target ranges for L1PA and T4-L1PA mismatch that minimized the risk of mechanical failure. The relationship between changes in T4PA and changes in global sagittal alignment according to the C2-pelvic angle (C2PA) was determined using linear regression. Lastly, multivariable regression was used to assess associations between initial postoperative C2PA and patient-reported outcomes at 1 year, adjusting for preoperative scores and age.

RESULTS

The median age of the 247 included patients was 64 years (interquartile range, 57 to 69 years), and 202 (82%) were female. Deviation from a normal L1PA or T4-L1PA mismatch in either direction was associated with a significantly higher risk of mechanical failure, independent of age. Risk was minimized with an L1PA of PI × 0.5 - (19° ± 2°) and T4-L1PA mismatch between -3° and +1°. Changes in T4PA and in C2PA at the time of final follow-up were strongly associated (r 2 = 0.96). Higher postoperative C2PA was independently associated with more disability, more pain, and worse self-image at 1 year.

CONCLUSIONS

We defined sagittal alignment targets using L1PA (relative to PI) and the T4-L1PA mismatch, which are both directly modifiable during surgery. In patients undergoing long fusion to the sacrum, realignment based on these targets may lead to fewer mechanical failures.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Determining the utility of three-column osteotomies in revision surgery compared with primary surgeries in the thoracolumbar spine: a retrospective cohort study in the United States

STUDY DESIGN

Retrospective cohort study.

PURPOSE

To determine the incidence and success of three-column osteotomies (3COs) performed in primary and revision adult spine deformity (ASD) corrective surgeries.

OVERVIEW OF LITERATURE

3COs are often required to correct severe, rigid ASD presentations. However, controversy remains on the utility of 3COs, particularly in primary surgery.

METHODS

Patients ASD having 2-year data were included and divided into 3CO and non-3CO (remaining ASD cohort) groups. For the subanalysis, patients were stratified based on whether they were undergoing primary (P3CO) or revision (R3CO) surgery. Multivariate analysis controlling for age, Charlson comorbidity index, body mass index, baseline pelvic incidence-lumbar lordosis, and fused levels evaluated the complication rates and radiographic and patient-reported outcomes between the 3CO and non-3CO groups.

RESULTS

Of the 436 patients included, 20% had 3COs. 3COs were performed in 16% of P3COs and 51% of R3COs. Both 3CO groups had greater severity in deformity and disability at baseline; however, only R3COs improved more than non-3COs. Despite greater segmental correction, 3COs had much lower rates of aligning in the lumbar distribution index (LDI), higher mechanical complications, and more reoperations when performed below L3. When comparing P3COs and R3COs, baseline lumbopelvic and global alignments, as well as disability, were different. The R3CO group had greater clinical improvements and global correction (both p<0.04), although the P3CO group achieved alignment in LDI more often (odds ratio, 3.9; 95% confidence interval, 1.3-6.2; p=0.006). The P3CO group had more neurological complications (30% vs. 13%, p=0.042), whereas the R3CO tended to have higher mechanical complication rates (25% vs. 15%, p=0.2).

CONCLUSIONS

3COs showed greater improvements in realignment while failing to demonstrate the same clinical improvement as primaries without a 3CO. Overall, when suitably indicated, a 3CO offers superior utility for achieving optimal realignment across primary and revision surgeries for ASD correction.

Which sagittal plane assessment method is most predictive of complications after adult spinal deformity surgery?

PURPOSE

Different methods of sagittal alignment assessment compete for predicting adverse events after adult spinal deformity (ASD) surgery. We wanted to study which method provides greater benefit.

METHODS

Retrospective study of 391 patients operated for ASD, with > 6 instrumented levels, fused to the pelvis, and 2 years of follow-up. Three alignment methods were analyzed 6-week postoperatively: (1) Roussouly mismatch; (2) GAP score/GAP categories; (3) T4-L1-Hip axis. Binary logistic regression generated models that best predict the following adverse events: mechanical complications (MC): in general and isolated (PJK, PJF, rod breakage); reinterventions (in general and after MC); and readmissions. ROC/AUC analysis was also implemented. In a second regression round, we added different variables that were selected on univariate analysis-demographic, surgical, and radiographic-to complete the models.

RESULTS

The best predictor parameters in most models were T4-L1PA mismatch and GAP score; we could not prove a predictive ability of the Roussouly mismatch. The T4-L1PA mismatch best predicted general MC, PJK, PJK + PJF, and readmission, while the GAP score best predicted PJF and reinterventions (for MC and for any complication). However, the variance explained by these models was limited (Nagelkerke's R2 = 0.031-0.113), with odds ratios ranging from 1.070 to 1.456. ROC curves plotted an AUC between 0.57 and 0.70. Introducing additional variables (demographic, surgical, and radiographic) improved prediction in all the models (Nagelkerke's R2 = 0.082-0.329) and allowed predicting rod breakage.

CONCLUSION

The T4-L1-Hip axis and GAP score show potential in predicting adverse events, surpassing the Roussouly method. Despite partial efficacy in complication anticipation, recognizing postoperative sagittal alignment as a key modifiable risk factor, the crucial need arises to integrate diverse variables, both modifiable and non-modifiable, for enhanced predictive accuracy.

LEVEL OF EVIDENCE

Level IV.

Deep Learning Method for Precise Landmark Identification and Structural Assessment of Whole-Spine Radiographs

This study measured parameters automatically by marking the point for measuring each parameter on whole-spine radiographs. Between January 2020 and December 2021, 1017 sequential lateral whole-spine radiographs were retrospectively obtained. Of these, 819 and 198 were used for training and testing the performance of the landmark detection model, respectively. To objectively evaluate the program's performance, 690 whole-spine radiographs from four other institutions were used for external validation. The combined dataset comprised radiographs from 857 female and 850 male patients (average age 42.2 ± 27.3 years; range 20-85 years). The landmark localizer showed the highest accuracy in identifying cervical landmarks (median error 1.5-2.4 mm), followed by lumbosacral landmarks (median error 2.1-3.0 mm). However, thoracic landmarks displayed larger localization errors (median 2.4-4.3 mm), indicating slightly reduced precision compared with the cervical and lumbosacral regions. The agreement between the deep learning model and two experts was good to excellent, with intraclass correlation coefficient values >0.88. The deep learning model also performed well on the external validation set. There were no statistical differences between datasets in all parameters, suggesting that the performance of the artificial intelligence model created was excellent. The proposed automatic alignment analysis system identified anatomical landmarks and positions of the spine with high precision and generated various radiograph imaging parameters that had a good correlation with manual measurements.

Assessing the predictive power of the GAP score on mechanical complications: a comprehensive systematic review and meta-analysis

PURPOSE

The prevention of mechanical complications (MC) is a major concern in adult spinal deformity (ASD) correction surgery; thus, the global alignment and proportion (GAP) score was developed to assess MC risk. Numerous studies have clarified the validity of the GAP score, but their contradictory results have prevented researchers from reaching compelling conclusions. This study aimed to analyze the predictive power of the GAP score on MC via a meta-analysis.

METHODS

A total of 1,617 patients were included in the meta-analysis. Studies relevant to the GAP score and MC were identified in PubMed, EMBASE, and Cochrane CENTRAL and screened according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The GAP score categories of the patients and their MC/revision surgery status were collected. The data collected for the meta-analysis of odds ratios (OR) included the number of patients in the GAP score subgroups and their MC/revision surgery status. To calculate the OR, three GAP score subgroups were combined into two groups; hence, the analysis was conducted twice (gap proportioned [GAP-P] and higher groups, and gap severely disproportioned [GAP-SD] and lower groups).

RESULTS

Eleven studies were collected; of them, revision surgery data were available for seven. The proportion of MC in the studies was 27.7-60.6%, while that of revision surgery was 11.7-34.9%. In the meta-analysis of the GAP-P and higher score groups, the difference in MC ratio was significant (OR = 2.83; 95% confidence interval [CI] = 1.20-6.67; P = 0.02), whereas that for revision surgery was not. For the GAP-SD and lower score groups, the GAP-SD group had significantly higher proportions of both MC (OR = 2.65; 95% CI = 1.57-4.45; P < 0.001) and revision surgery (OR = 2.27; 95% CI = 1.33-3.88; P = 0.003). Publication bias was significant only in the latter MC analysis.

CONCLUSION

The GAP score offers predictive value for the risk of mechanical complications.

Gravity Line-Hip Axis Offset as a Guide for Global Alignment to Prevent Recurrent Proximal Junctional Kyphosis/Failure

BACKGROUND AND OBJECTIVES

Proximal junctional kyphosis/failure (PJK/F) is a potentially serious complication after adult spinal deformity (ASD) corrective surgery. Recurrent PJK/F is especially troublesome, necessitating fusion extension and occasionally resulting in irreversible neurological deficits. The gravity line (GL) offers valuable insights into global sagittal balance. This study aims to examine the postoperative GL-hip axis (GL-HA) offset as a critical risk factor for recurrent PJK/F.

METHODS

We retrospectively reviewed patients with ASD who had undergone revision surgery for initial PJK/F at a single academic center. Patients were categorized into 2 groups: nonrecurrent PJK/F group and recurrent PJK/F group. Demographics, surgical characteristics, preoperative and postoperative parameters of spinopelvic and global alignment, and the Scoliosis Research Society-22 scores were assessed. We examined these measures for differences and correlations with recurrent PJK/F.

RESULTS

Our study included 32 patients without recurrent PJK/F and 28 patients with recurrent PJK/F. No significant differences were observed in baseline demographics, operative characteristics, or Scoliosis Research Society-22 scores before and after surgery. Importantly, using a cutoff of -52.6 mm from logistic regression, there were considerable differences and correlations with recurrent PJK/F in the postoperative GL-HA offset, leading to an odds ratio of 7.0 (95% CI: 1.94-25.25, P = .003).

CONCLUSION

Postoperative GL-HA offset serves as a considerable risk factor for recurrent PJK/F in patients with ASD who have undergone revision surgery. Overcorrection, with GL-HA offset less than -5 cm, is associated with recurrent PJK/F. The instrumented spine tends to align the GL near the HA, even at the cost of proximal junction.

Persistent Lower Extremity Compensation for Sagittal Imbalance After Surgical Correction of Complex Adult Spinal Deformity: A Radiographic Analysis of Early Impact

BACKGROUND AND OBJECTIVES

Achieving spinopelvic realignment during adult spinal deformity (ASD) surgery does not always produce ideal outcomes. Little is known whether compensation in lower extremities (LEs) plays a role in this disassociation. The objective is to analyze lower extremity compensation after complex ASD surgery, its effect on outcomes, and whether correction can alleviate these mechanisms.

METHODS

We included patients with complex ASD with 6-week data. LE parameters were as follows: sacrofemoral angle, knee flexion angle, and ankle flexion angle. Each parameter was ranked, and upper tertile was deemed compensation. Patients compensating and not compensating postoperatively were propensity score matched for body mass index, frailty, and T1 pelvic angle. Linear regression assessed correlation between LE parameters and baseline deformity, demographics, and surgical details. Multivariate analysis controlling for baseline deformity and history of total knee/hip arthroplasty evaluated outcomes.

RESULTS

Two hundred and ten patients (age: 61.3 ± 14.1 years, body mass index: 27.4 ± 5.8 kg/m2, Charlson Comorbidity Index: 1.1 ± 1.6, 72% female, 22% previous total joint arthroplasty, 24% osteoporosis, levels fused: 13.1 ± 3.8) were included. At baseline, 59% were compensating in LE: 32% at hips, 39% knees, and 36% ankles. After correction, 61% were compensating at least one joint. Patients undercorrected postoperatively were less likely to relieve LE compensation (odds ratio: 0.2, P = .037). Patients compensating in LE were more often undercorrected in age-adjusted pelvic tilt, pelvic incidence, lumbar lordosis, and T1 pelvic angle and disproportioned in Global Alignment and Proportion (P < .05). Patients matched in sagittal age-adjusted score at 6 weeks but compensating in LE were more likely to develop proximal junctional kyphosis (odds ratio: 4.1, P = .009) and proximal junctional failure (8% vs 0%, P = .035) than those sagittal age-adjusted score-matched and not compensating in LE.

CONCLUSION

Perioperative lower extremity compensation was a product of undercorrecting complex ASD. Even in age-adjusted realignment, compensation was associated with global undercorrection and junctional failure. Consideration of lower extremities during planning is vital to avoid adverse outcomes in perioperative course after complex ASD surgery.

Proximal Junctional Kyphosis Prevention Strategies Focused on Alignment

Adult spinal deformity (ASD) is a complex pathology associated with spinal malalignment in the coronal, sagittal, and axial planes. Proximal junction kyphosis (PJK) is a complication of ASD surgery, affecting 10%-48% of patients, and can result in pain and neurological deficit. It is defined radiographically as a greater than 10° Cobb angle between the upper instrumented vertebrae and the 2 vertebrae proximal to the superior endplate. Risk factors are classified according to the patient, surgery, and overall alignment, but it is important to consider the interplay between various factors. This article reviews the risk factors of PJK and considers alignment-focused prevention strategies.

Should Global Realignment Be Tailored to Frailty Status for Patients Undergoing Surgical Intervention for Adult Spinal Deformity?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Assess whether modifying spinal alignment goals to accommodate frailty considerations will decrease mechanical complications and maximize clinical outcomes.

SUMMARY OF BACKGROUND DATA

The Global Alignment and Proportion (GAP) score was developed to assist in reducing mechanical complications, but has had less success predicting such events in external validation. Higher frailty and many of its components have been linked to the development of implant failure. Therefore, modifying the GAP score with frailty may strengthen its ability to predict mechanical complications.

MATERIALS AND METHODS

We included 412 surgical ASD patients with two-year follow-up. Frailty was quantified using the modified Adult Spinal Deformity Frailty Index (mASD-FI). Outcomes: proximal junctional kyphosis and proximal junctional failure (PJF), major mechanical complications, and "Best Clinical Outcome" (BCO), defined as Oswestry Disability Index<15 and Scoliosis Research Society 22-item Questionnaire Total>4.5. Logistic regression analysis established a six-week score based on GAP score, frailty, and Oswestry Disability Index US Norms. Logistic regression followed by conditional inference tree analysis generated categorical thresholds. Multivariable logistic regression analysis controlling for confounders was used to assess the performance of the frailty-modified GAP score.

RESULTS

Baseline frailty categories: 57% not frail, 30% frail, 14% severely frail. Overall, 39 of patients developed proximal junctional kyphosis, 8% PJF, 21% mechanical complications, 22% underwent reoperation, and 15% met BCO. The mASD-FI demonstrated a correlation with developing PJF, mechanical complications, undergoing reoperation, and meeting BCO at two years (all P <0.05). Regression analysis generated the following equation: Frailty-Adjusted Realignment Score (FAR Score)=0.49×mASD-FI+0.38×GAP Score. Thresholds for the FAR score (0-13): proportioned: <3.5, moderately disproportioned: 3.5-7.5, severely disproportioned: >7.5. Multivariable logistic regression assessing FAR score demonstrated associations with mechanical complications, reoperation, and meeting BCO by two years (all P <0.05), whereas the original GAP score was only significant for reoperation.

CONCLUSION

This study demonstrated adjusting alignment goals in adult spinal deformity surgery for a patient's baseline frailty status and disability may be useful in minimizing the risk of complications and adverse events, outperforming the original GAP score in terms of prognostic capacity.

LEVEL OF EVIDENCE

III.

Risk factors for unplanned reoperation after corrective surgery for adult spinal deformity

To determine the major risk factors for unplanned reoperations (UROs) following corrective surgery for adult spinal deformity (ASD) and their interactions, using machine learning-based prediction algorithms and game theory. Patients who underwent surgery for ASD, with a minimum of two-year follow-up, were retrospectively reviewed. In total, 210 patients were included and randomly allocated into training (70% of the sample size) and test (the remaining 30%) sets to develop the machine learning algorithm. Risk factors were included in the analysis, along with clinical characteristics and parameters acquired through diagnostic radiology. Overall, 152 patients without and 58 with a history of surgical revision following surgery for ASD were observed; the mean age was 68.9 years (SD 8.7) and 66.9 years (SD 6.6), respectively. On implementing a random forest model, the classification of URO events resulted in a balanced accuracy of 86.8%. Among machine learning-extracted risk factors, URO, proximal junction failure (PJF), and postoperative distance from the posterosuperior corner of C7 and the vertical axis from the centroid of C2 (SVA) were significant upon Kaplan-Meier survival analysis. The major risk factors for URO following surgery for ASD, i.e. postoperative SVA and PJF, and their interactions were identified using a machine learning algorithm and game theory. Clinical benefits will depend on patient risk profiles.

Predicting Mechanical Complications After Adult Spinal Deformity Operation Using a Machine Learning Based on Modified Global Alignment and Proportion Scoring With Body Mass Index and Bone Mineral Density

Objective: This study aimed to create an ideal machine learning model to predict mechanical complications in adult spinal deformity (ASD) surgery based on GAPB (modified global alignment and proportion scoring with body mass index and bone mineral density) factors.Methods: Between January 2009 and December 2018, 238 consecutive patients with ASD, who received at least 4-level fusions and were followed-up for ≥ 2 years, were included in the study. The data were stratified into training (n = 167, 70%) and test (n = 71, 30%) sets and input to machine learning algorithms, including logistic regression, random forest gradient boosting system, and deep neural network.Results: Body mass index, bone mineral density, the relative pelvic version score, the relative lumbar lordosis score, and the relative sagittal alignment score of the global alignment and proportion score were significantly different in the training and test sets (p < 0.05) between the complication and no complication groups. In the training set, the area under receiver operating characteristics (AUROCs) for logistic regression, gradient boosting, random forest, and deep neural network were 0.871 (0.817–0.925), 0.942 (0.911–0.974), 1.000 (1.000–1.000), and 0.947 (0.915–0.980), respectively, and the accuracies were 0.784 (0.722–0.847), 0.868 (0.817–0.920), 1.000 (1.000–1.000), and 0.856 (0.803–0.909), respectively. In the test set, the AUROCs were 0.785 (0.678–0.893), 0.808 (0.702–0.914), 0.810 (0.710–0.910), and 0.730 (0.610–0.850), respectively, and the accuracies were 0.732 (0.629–0.835), 0.718 (0.614–0.823), 0.732 (0.629–0.835), and 0.620 (0.507–0.733), respectively. The random forest achieved the best predictive performance on the training and test dataset.Conclusion: This study created a comprehensive model to predict mechanical complications after ASD surgery. The best prediction accuracy was 73.2% for predicting mechanical complications after ASD surgery.

Crossing the Bridge From Degeneration to Deformity: When Does Sagittal Correction Impact Outcomes in Adult Spinal Deformity Surgery?

BACKGROUND

Patients with less severe adult spinal deformity (ASD) undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction rather than treatment of the spondylotic process.

PURPOSE

Determine baseline thresholds in radiographic parameters that, when exceeded, may result in substantive clinical improvement from surgical correction.

STUDY DESIGN

Retrospective.

MATERIALS AND METHODS

ASD patients with BL and two-year data were included. Parameters assessed: sagittal vertical axis, pelvic incidence-lumbar lordosis mismatch, pelvic tilt, T1 pelvic angle, L1 pelvic angle, L4-S1 lordosis, C2-C7 sagittal vertical axis, C2-T3, C2 slope. Outcomes: Good Outcome (GO) at two years: [meeting either: (1) Substantial Clinical Benefit for Oswestry Disability Index (change >18.8), or (2) Oswestry Disability Index <15 and Scoliosis Research Society Total>4.5]. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO.

RESULTS

We included 431 ASD patients. There were 223 (50%) that achieved a GO by two years. Binary logistic regression analysis demonstrated, with increasing baseline severity in deformity, sagittal correction was more often seen in those achieving GO for each parameter(all P <0.001). Of patients with baseline T1 pelvic angle above the threshold, 95% required correction to meet GO (95% vs. 54%, P <0.001). A baseline pelvic incidence-lumbar lordosis >10° (74% of patients meeting GO) needed correction to achieve GO (odds ratio: 2.6, 95% confidence interval: 1.4-4.8). A baseline C2 slope >15° also necessitated correction to obtain clinical success (odds ratio: 7.7, 95% confidence interval: 3.7-15.7).

CONCLUSIONS

Our study highlighted point may be present at which sagittal correction has an outsized influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds give us insight into which patients may be more suitable for sagittal correction, as opposed to intervention for the spondylotic process only, leading to a more efficient utility of surgical intervention for ASD.

Reciprocal Changes in the Whole-Body Following Realignment Surgery in Adult Spinal Deformity

The idea of the global balance of spine stems from Jean Dubousset, who first introduced the concept of cone of economy. Through the compensatory mechanisms, the human body maintains an upright posture and horizontal gaze in the setting of the spinal malalignment. Compensation takes place not only in the mobile spine segments, but also in the pelvis and lower extremities. Patients with a malalignment exhibit compensatory changes in the cervical hyper-lordosis, posterior pelvic shift, knee/ankle flexion, hip extension, and the pelvic retroversion. The advent of whole-body stereo radiography has yielded an improved understanding of global changes among the patients. Deformity-induced compensatory changes in the sagittal alignment could be resolved reciprocally after the surgical correction of the malalignment. Thoracolumbar realignment surgery restores the pathologic compensatory changes in the unfused spinal segments, pelvis, and the lower extremities. Similarly, reciprocal changes in the thoracolumbar spine may harmonize global sagittal alignment after the cervical reconstruction. This study reviews the compensatory mechanisms and reciprocal changes in global sagittal alignment caused by the surgical correction and highlights, the factors that should be considered while assessing a patient's compensatory status.

Assessing the influence of modifiable patient-related factors on complication rates after adult spinal deformity surgery

Aims

Postoperative complication rates remain relatively high after adult spinal deformity (ASD) surgery. The extent to which modifiable patient-related factors influence complication rates in patients with ASD has not been effectively evaluated. The aim of this retrospective cohort study was to evaluate the association between modifiable patient-related factors and complications after corrective surgery for ASD.

Methods

ASD patients with two-year data were included. Complications were categorized as follows: any complication, major, medical, surgical, major mechanical, major radiological, and reoperation. Modifiable risk factors included smoking, obesity, osteoporosis, alcohol use, depression, psychiatric diagnosis, and hypertension. Patients were stratified by the degree of baseline deformity (low degree of deformity (LowDef)/high degree of deformity (HighDef): below or above 20°) and age (Older/Younger: above or below 65 years). Complication rates were compared for modifiable risk factors in each age/deformity group, using multivariable logistic regression analysis to adjust for confounders.

Results

A total of 480 ASD patients met the inclusion criteria. By two years, complication rates were 72% ≥ one complication, 28% major, 21% medical, 27% surgical, 11% major radiological, 8% major mechanical, and 22% required reoperation. Younger LowDef patients with osteoporosis were more likely to suffer either a major mechanical (odds ratio (OR) 5.9 (95% confidence interval (CI) 1.1 to 36.9); p = 0.048) or radiological complication (OR 7.0 (95% CI 1.9 to 25.9); p = 0.003). Younger HighDef patients were much more likely to develop complications if obese, especially major mechanical complications (OR 2.8 (95% CI 1.1 to 8.6); p = 0.044). Older HighDef patients developed more complications when diagnosed with depression, including major radiological complications (OR 3.5 (95% CI 1.1 to 10.6); p = 0.033). Overall, a diagnosis of depression proved to be a risk factor for the development of major radiological complications (OR 2.4 (95% CI 1.3 to 4.5); p = 0.005).

Conclusion

Certain modifiable patient-related factors, especially osteoporosis, obesity, and mental health status, are associated with an increased risk of complications after surgery for spinal deformity. Surgeons should look for these conditions when assessing a patient for surgery, and optimize them to the fullest extent possible before proceeding to surgical correction so as to minimize the prospect of postoperative morbidity. Cite this article: Bone Joint J 2022;104-B(11):1249–1255.

Relationship Between Hounsfield Units of Upper Instrumented Vertebrae, Proximal Junctional Failure, and Global Alignment and Proportion Score in Female Patients with Adult Spinal Deformity

STUDY DESIGN

This was a retrospective observational study.

OBJECTIVES

The purpose of this study was to evaluate bone mineral density using Hounsfield unit (HU) values at the upper instrumented vertebrae (UIV), UIV+1, and UIV+2 and to investigate the association with proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD). We also evaluated the relationship between the global alignment and proportion (GAP) score and the HU value of patients after ASD surgery.

METHODS

Fifty-two patients (52 females, mean age =70.2 years) who underwent multiple-level lateral lumbar interbody fusion combined with posterior instrumentation for ASD were included. The patients were divided into 2 groups, PJF and non-PJF. The demographics, surgical characteristics, and radiographic parameters were compared. Vertebral HU values at UIV, UIV+1, and UIV+2 using preoperative computed tomography scans and immediate postoperative GAP scores were also compared.

RESULTS

PJF was found in 13 of 52 patients (25.0%). Preoperative and postoperative thoracic kyphosis was large in PJF patients. Based on the total GAP score, there was no significant difference among the categories of GAP scores (P = 0.514). The statistically significant difference in mean HU values (116.6 ± 28.1 vs. 141.8 ± 41.8, P = 0.049) between the two groups at UIV. Further correlation analysis showed that the mean HU values in UIV and UIV+1 showed a significantly negative correlation coefficient with the total GAP score.

CONCLUSIONS

Our study suggests that preoperative HU values at UIV may affect the development of PJF for female ASD patients. HU evaluation by preoperative computed tomography may help reduce the incidence of PJF.