Adult Spinal Deformity: Current Concepts and Decision-Making Strategies for Management

Do Obese Patients Have Worse Outcomes in Adult Spinal Deformity Surgeries?: A Meta-analysis

STUDY DESIGN

A meta-analysis study.

OBJECTIVE

This meta-analysis evaluates the difference in surgical outcomes between obese and nonobese patients undergoing adult spinal deformity (ASD) corrective surgery.

BACKGROUND

ASD encompasses a wide range of debilitating spinal abnormalities. Concurrently, obesity is on the rise globally and has been shown to influence the outcomes of ASD management. The relationship between obesity and surgical outcomes in ASD has been the focus of recent studies, yielding various results.

MATERIALS AND METHODS

We conducted a comprehensive search of PubMed, Cochrane, and Google Scholar (pages 1-20) through June of 2024. The surgical outcomes assessed included postoperative complications, revision rates, wound infections, thromboembolic events, implant-related complications, and nonhome discharge. Surgical parameters such as operative time, length of stay (LOS), and estimated blood loss (EBL), as well as functional outcomes like the Oswestry Disability Index (ODI) and pain scores were analyzed.

RESULTS

Nine studies met the inclusion criteria. Nonobese patients exhibited a lower rate of implant-related complications [odds ratio (OR)=0.25; 95% CI: 0.12-0.52, P =0.0002] and nonhome discharge (OR=0.52; 95% CI: 0.32-0.84, P =0.007). In addition, nonobese patients had reduced LOS (MD=-0.29; 95% CI: -0.53 to -0.05, P =0.02) and EBL (SMD=-0.68; 95% CI: -1.19 to -0.18, P =0.008). No statistically significant differences were observed for the remaining outcomes.

CONCLUSION

Nonobese patients undergoing ASD corrective surgery are associated with fewer implant-related complications, a lower EBL, shorter LOS, and a higher likelihood of being discharged home compared with their obese counterparts.

Combined anterior-posterior versus posterior only approach for surgical management of adult spinal deformity: a systematic review and meta-analysis of comparative studies

PURPOSE

The purpose of this systematic review and meta-analysis was to examine the clinical outcomes and complication rates for fusion procedures of adult spinal deformity (ASD) performed via an anterior-posterior approach as compared to a posterior-only approach to guide surgical decision-making. Numerous surgical techniques exist for operative management of ASD; however, no systematic review and meta-analysis exists comparing combined anterior-posterior approaches to posterior-only approach, despite significant interest in the current literature.

METHODS

Four databases were used to collect articles from database inception until September 9th, 2023. Inclusion criteria was articles that examined both anterior-posterior or posterior only surgical approach, adult patients, comparative studies, and articles in English.

RESULTS

Seven comparative articles met the inclusion criteria. Included patients had a frequency weighted (FW) mean age of 60.2 ± 5.1 years and a FW mean follow-up of 40.4 ± 12.5 months. Qualitative data did not favor either group in terms of length of stay, radiographic outcomes, or functional outcomes. There was a total of 306 complications in the Anterior-Posterior group with a complication rate per patient of 1.0 ± 0.9 complications whereas there was a total of 380 complications in the Posterior Only group with a complication rate per patient of 1.0 ± 1.2 complications. Meta-analysis of specific complications found no significant difference in revision rate, dural tear rate, neurological complication rate, infection rate, or pseudoarthrosis rate.

CONCLUSION

Surgical management for ASD may provide comparable results in terms of surgical parameters, radiographic outcomes, functional outcomes, and complication rates, irrespective of surgical approach.

Defining modern iatrogenic flatback syndrome: examination of segmental lordosis in short lumbar fusion patients undergoing thoracolumbar deformity correction

PURPOSE

Understanding the mechanism and extent of preoperative deformity in revision procedures may provide data to prevent future failures in lumbar spinal fusion patients.

METHODS

ASD patients without prior spine surgery (PRIMARY) and with prior short (SHORT) and long (LONG) fusions were included. SHORT patients were stratified into modes of failure: implant, junctional, malalignment, and neurologic. Baseline demographics, spinopelvic alignment, offset from alignment targets, and patient-reported outcome measures (PROMs) were compared across PRIMARY and SHORT cohorts. Segmental lordosis analyses, assessing under-, match, or over-correction to segmental and global lordosis targets, were performed by SRS-Schwab coronal curve type and construct length.

RESULTS

Among 785 patients, 430 (55%) were PRIMARY and 355 (45%) were revisions. Revision procedures included 181 (23%) LONG and 174 (22%) SHORT corrections. SHORT modes of failure included 27% implant, 40% junctional, 73% malalignment, and/or 28% neurologic. SHORT patients were older, frailer, and had worse baseline deformity (PT, PI-LL, SVA) and PROMs (NRS, ODI, VR-12, SRS-22) compared to primary patients (p < 0.001). Segmental lordosis analysis identified 93%, 88%, and 62% undercorrected patients at LL, L1-L4, and L4-S1, respectively. SHORT patients more often underwent 3-column osteotomies (30% vs. 12%, p < 0.001) and had higher ISSG Surgical Invasiveness Score (87.8 vs. 78.3, p = 0.006).

CONCLUSIONS

Nearly half of adult spinal deformity surgeries were revision fusions. Revision short fusions were associated with sagittal malalignment, often due to undercorrection of segmental lordosis goals, and frequently required more invasive procedures. Further initiatives to optimize alignment in lumbar fusions are needed to avoid costly and invasive deformity corrections.

LEVEL OF EVIDENCE

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

The Role of Pelvic Compensation in Sagittal Balance and Imbalance: The Impact of Pelvic Compensation on Spinal Alignment and Clinical Outcomes Following Adult Spinal Deformity Surgery

BACKGROUND AND OBJECTIVES

The Scoliosis Research Society (SRS)-Schwab system does not include a pelvic compensation (PC) subtype, potentially contributing to gaps in clinical characteristics and treatment strategy for deformity correction. It also remains uncertain as to whether PC has differing roles in sagittal balance (SB) or imbalance (SI) status. To compare radiological parameters and SRS-22r domains between patients with failed pelvic compensation (FPC) and successful pelvic compensation (SPC) based on preoperative SB and SI.

METHODS

A total of 145 adult spinal deformity patients who received deformity correction were analyzed. Radiographic and clinical outcomes were collected for statistical analysis. Patients were classified into 4 groups based on the median value of PT/PI ratio (PTr) and the cutoff value of SB. Patients with low PTr and high PTr were defined as FPC and SPC, respectively. Radiographic and clinical characteristics of different groups were compared.

RESULTS

Patients with SPC exhibited significantly greater improvements in lumbar lordosis, pelvic tilt, PTr, and T1 pelvic angle as compared to patients with FPC, irrespective of SB or SI. No apparent differences in any of SRS-22r domains were observed at follow-up when comparing the SB-FPC and SB-SPC patients. However, patients with SI-SPC exhibited significantly better function, self-image, satisfaction, and subtotal domains at follow-up relative to those with SI-FPC. When SI-FPC and SI-SPC patients were subdivided further based on the degree of PI-LL by adjusting for age, the postoperative function and self-image domains were significantly better in the group with overcorrection of PI-LL than undercorrection of PI-LL in SI-FPC patients. However, no differences in these SRS-22r scores were observed when comparing the subgroups in SI-SPC patients.

CONCLUSION

Flexible pelvic rotation is associated with benefits to the correction of sagittal parameters, irrespective of preoperative SB or SI status. However, PC is only significantly associated with clinical outcomes under SI. Patients with SI-FPC exhibit poorer postoperative clinical outcomes, which should be recommended to minimize PI-LL.

Surgical Management of Adult Spinal Deformity Patients with Osteoporosis

Adult spinal deformity (ASD) commonly affects older adults, with up to 68% prevalence in those over 60, and is often complicated by osteoporosis, which reduces bone mineral density (BMD) and increases surgical risks. Osteoporotic patients undergoing ASD surgery face higher risks of complications like hardware failure, pseudoarthrosis, and proximal junctional kyphosis (PJK). Medical management with antiresorptive medications (e.g., bisphosphonates, SERMs, and denosumab) and anabolic agents (e.g., teriparatide, abaloparatide, and romosozumab) can improve BMD and reduce complications. While bisphosphonates reduce fracture risk, teriparatide and newer agents like romosozumab show promise in increasing bone density and improving fusion rates. Surgical adaptations such as consideration of age-adjusted alignment, fusion level selection, cement augmentation, and the use of expandable screws or tethers enhance surgical outcomes in osteoporotic patients. Specifically, expandable screws and cement augmentation have been shown to improve fixation stability. However, further research is needed to evaluate the effectiveness of these treatments, specifically in osteoporotic ASD patients.

Glycemic laboratory values are associated with increased length of stay and 90-day revision risk following surgical management of adult spinal deformity

BACKGROUND CONTEXT

Diabetes mellitus (DM) is a common comorbidity among patients undergoing spinal fusion for adult spinal deformity (ASD) surgery. An elevated Hemoglobin A1c (HbA1c) and elevated postoperative glucose have been shown to increase the risk of complications following spine and other orthopedic surgeries; however, data is limited for ASD.

PURPOSE

To investigate glycemic control and ASD surgery to inform surgical decision making, medical optimization, and patient education.

STUDY DESIGN/SETTING

Retrospective cohort.

PATIENT SAMPLE

Total of 106 adult patients undergoing surgical correction for ASD with an HbA1c drawn within 6 months preoperatively or 2 weeks postoperatively and valid plasma glucose levels throughout postoperative hospital stay.

OUTCOME MEASURES

Length of stay, 90-day wound complication, 90-day readmission, 90-day revision.

METHODS

All patients undergoing spinal fusion of seven or more levels between 2021 and 2023 at two large academic medical centers were identified using institutional data acquisition software. Medical charts were then manually reviewed to obtain and confirm demographic, laboratory, and surgical characteristics and outcomes. Laboratory characteristics included preoperative HbA1c, mean postoperative glucose (PG), and maximum PG. Surgical characteristics and outcomes included procedure time, estimated blood loss (EBL), length of inpatient stay (LOS), transfusion requirement, 90-day complications, 90-day revision, and 90-day readmission. Bivariate analysis was performed followed by simple and multiple regression analysis. Odds ratios were established relative to the laboratory threshold values informed by receiver operating characteristics.

RESULTS

Of 872 original procedures identified, 106 patients (12.2%) were adults with preoperative HbA1c and postoperative plasma glucose measurements who underwent surgery for a diagnosis of ASD. Median patient age was 67 years (IQR 59-72 years), 59 (55.7%) were female, and 96 (90.6%) were of Caucasian race. Median LOS was 7 days (IQR 5-10 years) and median HbA1c was 5.9% (IQR 5.3%-6.5%). Higher preoperative HbA1c was correlated with increased LOS (R=0.22, p=.023). The odds ratio for patients requiring extended LOS was 2.49 (95% CI 1.06-5.86, p=.034) for those with HbA1c ≥6.3%. Multiple regression analysis of LOS identified HbA1c [B= 1.51 (95% CI 0.32-2.70), p=.013] as a positive predictor of LOS and mean PG [B= -0.05 (95% CI -0.10 to (-0.01)), p=.019] as a weakly negative predictor of LOS. Upon simple logistic regression, the odds ratio for 90-day revision was 1.81 (95% CI 1.02-3.19, p=.042) for every unit increase in HbA1c. Patients with mean PG ≥165 mg/dL [OR=5.76 (95% CI 1.28-26.01), p=.024] were at increased risk for 90-day revision. Glycemic laboratory values do not seem to predict 90-day wound complications or 90-day readmission following surgery for ASD.

CONCLUSION

Elevated preoperative HbA1c is associated with increased LOS and risk for revision within 90 days of ASD surgery. Postoperative hyperglycemia is also associated with increased 90-day revision risk. To our knowledge, this study is the first to evaluate HbA1c and outcomes following ASD surgery. These findings can be leveraged to inform preoperative medical optimization and highlight the importance of glycemic control in ASD patients undergoing corrective surgical intervention.

Causes of Intraoperative Neuromonitoring Events in Adult Spine Deformity Surgery: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

Intraoperative neuromonitoring (IOMN) has become a standard practice in the detection and prevention of nerve damage and postoperative deficit. While multicenter studies have addressed this inquiry, there have been no systematic reviews to date. This systematic review identifies the leading causes of IONM alerts during adult spinal deformity (ASD) surgeries.

METHODS

Following PRISMA guidelines, a literature search was performed in PubMed and Embase. IONM alert causes were grouped by equivalent terms used across different studies and binned into larger categories, including surgical maneuver, Changes in blood pressure/temperature, Oxygenation, Anesthesia, Patient position, and Unknown.

RESULTS

Inclusion criteria were studies on adult patients receiving ASD correction surgery using IONM with documented alert causes. 1544 references were included in abstract review, 128 in full text review, and 16 studies qualified for data extraction. From those studies, there was a total of 3945 adult patients with 299 IONM alerts. Surgical maneuver led the alert causes (258 alerts/86.3%), with signal loss most commonly occurring at correction or osteotomy (101/33.8% and 95/31.8% respectively). Pedicle screw placement caused 35 alerts (11.7%). Changes in temperature and blood pressure were the third largest category (34/11.4%).

CONCLUSIONS

The most frequent causes of IONM alerts in ASD surgery were surgical maneuvers such as correction, osteotomy, and pedicle screw placement. This information provides spine surgeons with a quantitative perspective on the causes of IONM changes and show that most occur at predictable times during ASD surgery.

The Effect of Osteoporosis on Complications and Reoperation Rates After Surgical Management of Adult Thoracolumbar Spinal Deformity: A Systematic Review and Meta Analysis

STUDY DESIGN

Systematic Review.

OBJECTIVES

While substantial research has explored the impact of osteoporosis on patients undergoing adult spinal deformity (ASD) correction, the literature remains inconclusive. As such, the purpose of this study is to synthesize and analyze existing studies pertaining to osteoporosis as a predictor of postoperative outcomes in ASD surgery.

METHODS

We performed a systematic review and meta-analysis to determine the effect that a diagnosis of osteoporosis, based on ICD-10 coding, dual-energy X-ray absorptiometry (DEXA) or computed tomography, has on the incidence of adverse outcomes following surgical correction of ASD. Statistical analysis was performed using Comprehensive Meta-Analysis (Version 2) using a random effects model to account for heterogeneity between studies.

RESULTS

After application of inclusion and exclusion criteria, 36 and 28 articles were included in the systematic review and meta-analysis, respectively. The meta-analysis identified greater rates of screw loosening amongst osteoporotic patients (70.5% vs 31.9%, P = .009), and decreased bone mineral density in patients who developed proximal junctional kyphosis (PJK) (.69 vs .79 g/cm2, P = .001). The systematic review demonstrated significantly increased risk of any complication, reoperation, and proximal junctional failure (PJF) associated with reduced bone density. No statistical difference was observed between groups regarding fusion rates, readmission rates, and patient-reported and/or functional outcome scores.

CONCLUSION

This study demonstrates a higher incidence of screw loosening, PJK, and revision surgery amongst osteoporotic ASD patients. Future investigations should explore outcomes at various follow-up intervals in order to better characterize how risk changes with time and to tailor preoperative planning based on patient-specific characteristics.

Global tilt angle in spinal alignment of asymptomatic older women with low bone mass

This study investigated the relationship between sagittal spinal alignment and musculoskeletal health in older women, particularly those exhibiting diminished bone density without apparent symptoms. The study assessed the impact of global tilt (GT) and the presence of coronal malalignment on spinal health. The research involved 165 asymptomatic older women with an average age of 68.91 ± 7.25 years and average body mass index of 24.26 ± 3.66 kg/m². Comprehensive standing anteroposterior and lateral spine radiographs were used for assessment. Through multivariate linear regression analysis, the study identified significant correlations between increased GT angles and various factors, including coronal malalignment, the C7 slope, and pelvic incidence. This led to the formulation of a predictive GT model: GT = -9.79 + 0.06 × menopausal period + 0.19 × body mass index (BMI)- 0.81 × average T score - 0.11 × grip strength + 3.03 × (presence of coronal malalignment) + 0.08 × sagittal vertical axis (SVA) + 0.12 × C7 slope - 0.35 × upper lumbar lordosis (ULL) - 0.43 × lower lumbar lordosis (LLL) + 0.70 × pelvic incidence (PI), with an adjusted R² of 0.816. The study findings highlight the prevalence of coronal malalignment in this demographic and its significant associations with critical spinal parameters. The proposed GT predictive model may enable development of personalized treatment plans for older women with low bone mass.

Bone Health Optimization in Adult Spinal Deformity Patients: A Narrative Review

Osteoporosis and low bone mineral density (BMD) pose significant challenges in adult spinal deformity surgery, increasing the risks of complications such as vertebral compression fractures, hardware failure, proximal junctional kyphosis/failure, and pseudoarthrosis. This narrative review examines the current evidence on bone health optimization strategies for spinal deformity patients. Preoperative screening and medical optimization are crucial, with vitamin D supplementation showing particular benefit. Among the pharmacologic agents, bisphosphonates demonstrate efficacy in improving fusion rates and reducing hardware-related complications, though the effects may be delayed. Teriparatide, a parathyroid hormone analog, shows promise in accelerating fusion and enhancing pedicle screw fixation. Newer anabolic agents like abaloparatide and romosozumab require further study but show potential. Romosozumab, in particular, has demonstrated significant improvements in lumbar spine BMD over a shorter duration compared to other treatments. Surgical techniques like cement augmentation and the use of larger interbody cages can mitigate the risks in osteoporotic patients. Overall, a multifaceted approach incorporating medical optimization, appropriate pharmacologic treatment, and tailored surgical techniques is recommended to improve outcomes in adult spinal deformity patients with compromised bone quality. Future research should focus on optimizing the treatment protocols, assessing the long-term outcomes of newer agents in the spine surgery population, and developing cost-effective strategies to improve access to these promising therapies.

Comparison of three artificial intelligence algorithms for automatic cobb angle measurement using teaching data specific to three disease groups

Spinal deformities, including adolescent idiopathic scoliosis (AIS) and adult spinal deformity (ASD), affect many patients. The measurement of the Cobb angle on coronal radiographs is essential for their diagnosis and treatment planning. To enhance the precision of Cobb angle measurements for both AIS and ASD, we developed three distinct artificial intelligence (AI) algorithms: AIS/ASD-trained AI (trained with both AIS and ASD cases); AIS-trained AI (trained solely on AIS cases); ASD-trained AI (trained solely on ASD cases). We used 1612 whole-spine radiographs, including 1029 AIS and 583 ASD cases with variable postures, as teaching data. We measured the major and two minor curves. To assess the accuracy, we used 285 radiographs (159 AIS and 126 ASD) as a test set and calculated the mean absolute error (MAE) and intraclass correlation coefficient (ICC) between each AI algorithm and the average of manual measurements by four spine experts. The AIS/ASD-trained AI showed the highest accuracy among the three AI algorithms. This result suggested that learning across multiple diseases rather than disease-specific training may be an efficient AI learning method. The presented AI algorithm has the potential to reduce errors in Cobb angle measurements and improve the quality of clinical practice.

Characteristics of Spinal Morphology According to the Global Alignment and Proportion (GAP) Score in a Diverse, Asymptomatic Cohort: Multi-Ethnic Alignment Normative Study

STUDY DESIGN

Multi-Ethnic Alignment Normative Study (MEANS) cohort: prospective, cross-sectional, multicenter.

OBJECTIVE

To analyze the distribution of GAP scores in the MEANS cohort and compare the spinal shape via stratification by GAP alignment category, age, and country.

SUMMARY OF BACKGROUND DATA

The GAP score has been used to categorize spinal morphology and prognosticate adult spinal deformity surgical outcomes and mechanical complications. We analyzed a large, multiethnic, asymptomatic cohort to assess the distribution of GAP scores.

METHODS

Four hundred sixty-seven healthy volunteers without spinal disorders were recruited in five countries. Sagittal radiographic parameters were measured via the EOS imaging system. The GAP total and constituent factor scores were calculated for each patient. Kruskal-Wallis rank sum test was performed to compare variables across groups, followed by the post hoc Games-Howell test. Fisher exact test was used to compare categorical variables. The significance level was set to P <0.05.

RESULTS

In the MEANS cohort, 13.7% (64/467) of volunteers were ≥60 years old, and 86.3% (403/467) were <60 years old. 76.9% (359/467) was proportioned, 19.5% (91/467) was moderately disproportioned, and 3.6% (17/467) was severely disproportioned. There was no significant difference in the frequency of proportioned, moderately, or severely disproportioned GAP between subjects from different countries ( P =0.060). Those with severely disproportioned GAP alignment were on average 14.5 years older ( P =0.016), had 23.1° lower magnitude lumbar lordosis (LL) ( P <0.001), 14.2° higher pelvic tilt ( P <0.001), 13.3° lower sacral slope ( P <0.001), and 24.1° higher pelvic-incidence (PI)-LL mismatch ( P <0.001), 18.2° higher global tilt ( P <0.001) than those with proportioned GAP; thoracic kyphosis and PI were not significantly different ( P >0.05).

CONCLUSIONS

The GAP system applies to a large, multiethnic, asymptomatic cohort. Spinal alignment should be considered on a spectrum, as 19.5% of the asymptomatic volunteers were classified as moderately disproportioned and 3.6% severely disproportioned. Radiographic malalignment does not always indicate symptoms or pathology.

LEVEL OF EVIDENCE

3.

Topping-Off a Long Thoracic Stabilization With Semi-Rigid Constructs May Have Favorable Biomechanical Effects to Prevent Proximal Junctional Kyphosis: A Biomechanical Comparison

STUDY DESIGN

In-vitro cadaveric biomechanical study.

OBJECTIVES

Long posterior spinal fusion is a standard treatment for adult spinal deformity. However, these rigid constructs are known to alter motion and stress to the adjacent non-instrumented vertebrae, increasing the risk of proximal junctional kyphosis (PJK). This study aimed to biomechanically compare a standard rigid construct vs constructs "topped off" with a semi-rigid construct. By understanding semi-rigid constructs' effect on motion and overall construct stiffness, surgeons and researchers could better optimize fusion constructs to potentially decrease the risk of PJK and the need for revision surgery.

METHODS

Nine human cadaveric spines (T1-T12) underwent non-destructive biomechanical range of motion tests in pure bending or torsion and were instrumented with an all-pedicle-screw (APS) construct from T6-T9. The specimens were sequentially instrumented with semi-rigid constructs at T5: (i) APS plus sublaminar bands; (ii) APS plus supralaminar hooks; (iii) APS plus transverse process hooks; and (iv) APS plus short pedicle screws.

RESULTS

APS plus transverse process hooks had a range of motion (ie, relative angle) for T4-T5 and T5-T6, as well as an overall mechanical stiffness for T1-T12, that was more favourable, as it reduced motion at adjacent levels without a stark increase in stiffness. Moreover, APS plus transverse process hooks had the most linear change for range of motion across the entire T3-T7 range.

CONCLUSIONS

Present findings suggest that APS plus transverse process hooks has a favourable biomechanical effect that may reduce PJK for long spinal fusions compared to the other constructs examined.

Impact of Hip and Knee Osteoarthritis on Full Body Sagittal Alignment and Compensation for Sagittal Spinal Deformity

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

To investigate the effect of lower extremity osteoarthritis on sagittal alignment and compensatory mechanisms in adult spinal deformity (ASD).

BACKGROUND

Spine, hip, and knee pathologies often overlap in ASD patients. Limited data exists on how lower extremity osteoarthritis impacts sagittal alignment and compensatory mechanisms in ASD.

PATIENTS AND METHODS

In total, 527 preoperative ASD patients with full body radiographs were included. Patients were grouped by Kellgren-Lawrence grade of bilateral hips and knees and stratified by quartile of T1-Pelvic Angle (T1PA) severity into low-, mid-, high-, and severe-T1PA. Full-body alignment and compensation were compared across quartiles. Regression analysis examined the incremental impact of hip and knee osteoarthritis severity on compensation.

RESULTS

The mean T1PA for low-, mid-, high-, and severe-T1PA groups was 7.3°, 19.5°, 27.8°, and 41.6°, respectively. Mid-T1PA patients with severe hip osteoarthritis had an increased sagittal vertical axis and global sagittal alignment ( P <0.001). Increasing hip osteoarthritis severity resulted in decreased pelvic tilt ( P =0.001) and sacrofemoral angle ( P <0.001), but increased knee flexion ( P =0.012). Regression analysis revealed that with increasing T1PA, pelvic tilt correlated inversely with hip osteoarthritis and positively with knee osteoarthritis ( r2 =0.812). Hip osteoarthritis decreased compensation through sacrofemoral angle (β-coefficient=-0.206). Knee and hip osteoarthritis contributed to greater knee flexion (β-coefficients=0.215, 0.101; respectively). For pelvic shift, only hip osteoarthritis significantly contributed to the model (β-coefficient=0.100).

CONCLUSIONS

For the same magnitude of spinal deformity, increased hip osteoarthritis severity was associated with worse truncal and full body alignment with posterior translation of the pelvis. Patients with severe hip and knee osteoarthritis exhibited decreased hip extension and pelvic tilt but increased knee flexion. This examines sagittal alignment and compensation in ASD patients with hip and knee arthritis and may help delineate whether hip and knee flexion is due to spinal deformity compensation or lower extremity osteoarthritis.

Machine learning clustering of adult spinal deformity patients identifies four prognostic phenotypes: a multicenter prospective cohort analysis with single surgeon external validation

BACKGROUND CONTEXT

Among adult spinal deformity (ASD) patients, heterogeneity in patient pathology, surgical expectations, baseline impairments, and frailty complicates comparisons in clinical outcomes and research. This study aims to qualitatively segment ASD patients using machine learning-based clustering on a large, multicenter, prospectively gathered ASD cohort.

PURPOSE

To qualitatively segment adult spinal deformity patients using machine learning-based clustering on a large, multicenter, prospectively gathered cohort.

STUDY DESIGN/SETTING

Machine learning algorithm using patients from a prospective multicenter study and a validation cohort from a retrospective single center, single surgeon cohort with complete 2-year follow up.

PATIENT SAMPLE

About 805 ASD patients; 563 patients from a prospective multicenter study and 242 from a single center to be used as a validation cohort.

OUTCOME MEASURES

To validate and extend the Ames-ISSG/ESSG classification using machine learning-based clustering analysis on a large, complex, multicenter, prospectively gathered ASD cohort.

METHODS

We analyzed a training cohort of 563 ASD patients from a prospective multicenter study and a validation cohort of 242 ASD patients from a retrospective single center/surgeon cohort with complete two-year patient-reported outcomes (PROs) and clinical/radiographic follow-up. Using k-means clustering, a machine learning algorithm, we clustered patients based on baseline PROs, Edmonton frailty, age, surgical history, and overall health. Baseline differences in clusters identified using the training cohort were assessed using Chi-Squared and ANOVA with pairwise comparisons. To evaluate the classification system's ability to discern postoperative trajectories, a second machine learning algorithm assigned the single-center/surgeon patients to the same 4 clusters, and we compared the clusters' two-year PROs and clinical outcomes.

RESULTS

K-means clustering revealed four distinct phenotypes from the multicenter training cohort based on age, frailty, and mental health: Old/Frail/Content (OFC, 27.7%), Old/Frail/Distressed (OFD, 33.2%), Old/Resilient/Content (ORC, 27.2%), and Young/Resilient/Content (YRC, 11.9%). OFC and OFD clusters had the highest frailty scores (OFC: 3.76, OFD: 4.72) and a higher proportion of patients with prior thoracolumbar fusion (OFC: 47.4%, OFD: 49.2%). ORC and YRC clusters exhibited lower frailty scores and fewest patients with prior thoracolumbar procedures (ORC: 2.10, 36.6%; YRC: 0.84, 19.4%). OFC had 69.9% of patients with global sagittal deformity and the highest T1PA (29.0), while YRC had 70.2% exhibiting coronal deformity, the highest mean coronal Cobb Angle (54.0), and the lowest T1PA (11.9). OFD and ORC had similar alignment phenotypes with intermediate values for Coronal Cobb Angle (OFD: 33.7; ORC: 40.0) and T1PA (OFD: 24.9; ORC: 24.6) between OFC (worst sagittal alignment) and YRC (worst coronal alignment). In the single surgeon validation cohort, the OFC cluster experienced the greatest increase in SRS Function scores (1.34 points, 95%CI 1.01-1.67) compared to OFD (0.5 points, 95%CI 0.245-0.755), ORC (0.7 points, 95%CI 0.415-0.985), and YRC (0.24 points, 95%CI -0.024-0.504) clusters. OFD cluster patients improved the least over 2 years. Multivariable Cox regression analysis demonstrated that the OFD cohort had significantly worse reoperation outcomes compared to other clusters (HR: 3.303, 95%CI: 1.085-8.390).

CONCLUSION

Machine-learning clustering found four different ASD patient qualitative phenotypes, defined by their age, frailty, physical functioning, and mental health upon presentation, which primarily determines their ability to improve their PROs following surgery. This reaffirms that these qualitative measures must be assessed in addition to the radiographic variables when counseling ASD patients regarding their expected surgical outcomes.

A 3-Year Study Investigating the Utility of Patient-Reported Outcomes Measurement Information System-29 for Long-Term Follow-Up in Adult Spinal Deformity

BACKGROUND

Adult spinal deformity (ASD) significantly impacts the quality of life due to three-dimensional spinal abnormalities. Patient-reported outcome measures, such as the Patient-Reported Outcomes Measurement Information System (PROMIS-29), play a crucial role in assessing postoperative outcomes. This study aims to investigate trends in PROMIS-29 scores over 36 months in patients undergoing long-segment thoracolumbar fusion for ASD and provide insights into its long-term utility.

METHODS

A retrospective study including 163 ASD patients undergoing long-segment thoracolumbar fusion was conducted. PROMIS-29 scores were collected at baseline and at postoperative (0-), 3-, 6-, 12-, 18-, 24-, 30-, and 36-month follow-ups. Statistical analyses was performed to assess significant score changes from baseline and in consecutive recordings.

RESULTS

Significant improvements in all PROMIS-29 categories were observed at 36 months, with the greatest changes in pain intensity (-35.19%, P < 0.001), physical function (+29.13%, P < 0.001), and pain interference (-28.8%, P < 0.001). Between the 0 and 3 month mark, the greatest significant changes were recorded in pain intensity (-26.5%, P < 0.001), physical function (+24.3%, P < 0.001), and anxiety (-16.9%, P < 0.018). However, scores plateaued after the 3-month mark, with zero categories showing significant changes with subsequent consecutive recordings.

CONCLUSIONS

PROMIS-29 scores demonstrated notable improvements in ASD patients particularly in pain intensity, pain interference, and physical function. However, scores plateaued beyond the 3-month mark, suggesting PROMIS-29's limited sensitivity to nuanced changes in long-term patient recovery. Future investigations exploring optimal combinations of patient reported outcome measures for comprehensive short- and long-term outcome assessments in ASD surgery would be beneficial.

Radiographic Alignment Parameters for Lumbosacral Reconstruction in Patients With Altered S1 Morphology

STUDY DESIGN

Retrospective quantitative analysis study.

OBJECTIVES

Pelvic incidence has been established as central radiographic marker which determines patient-specific correction goals during surgery for adult spinal deformity. In cases with sacral doming or sacral osteotomy where the PI cannot be calculated, reliable radiographic parameters need to be established to determine surgical goals. We aim to determine multiple radiographic parameters and formulas that can be utilized when the S1 superior endplate is obscured.

METHODS

Retrospective analysis was performed on 68 healthy volunteers without prior spine surgery with full-length radiographs. Pelvic incidence, sacral slope, and pelvic tilt were calculated for each patient. Additional measurements such as L4, L5, and S2 incidence, tilt, and slope were collected. A new radiographic parameter defined as the L4-Sciatic notch angle was measured. Regression analysis was performed on each value to determine its relationship with S1 based incidence, tilt, and slope.

RESULTS

Mean values for L5 incidence, L4 incidence, and L4 sciatic notch angle were 21.8° ± 8.9, 4.4° ± 8.1, and 44.4° ± 12, respectively. The linear regression analysis produced the following formulas which can be utilized to determine deformity correction goals when pelvic incidence can be calculated pre-operatively: L5i = .65*S1i-11.4, L4i = .44*S1i-18.6, and L4SNA = -.34*S1i + 66.5. In settings where pelvic incidence cannot be calculated, the following formulas can be utilized: L5i = .66*S2i-32.3 and L4SNA = -.02*S2i2 + 1.1*S2i + 63.5. P-values for all regression analyses were <.001.

CONCLUSION

This study provides target radiographic alignment values that can be utilized for patients with either pre-operative altered S1 endplates or in cases with intraoperative alteration of S1 (sacral osteotomy).

Investigation of the Role of Osteoporotic Vertebra Degeneration on the Stability of the Lumbar Spine: In Silico Modelling under Compressive Loading

An evaluation of the impact of osteoporosis on loss of spinal stability, with or without intervertebral disc degeneration, using computational analysis is presented. The research also investigates the correlation between osteoporosis and intervertebral disc degeneration. Three-dimensional finite element models of human lumbar spine segments were used to assess the influence of osteoporosis on spinal stability. Five different models of age-related degeneration were created using various material properties for trabecular bone and intervertebral discs. Calculation results indicate that in a spine with osteoporosis, the deformation of the intervertebral discs can increase by more than 30% when compared to a healthy spine. Thus, intervertebral disc deformation depends not only on the degree of degeneration of the discs themselves, but their deformation is also influenced by the degree of osteoporosis of the vertebrae. Additionally, the load-bearing capacity of the spine can decrease by up to 30% with osteoporosis, regardless of the degree of intervertebral disc deformation. In conclusion, osteoporosis can contribute to intervertebral disc degeneration.

5-year outcomes of surgical intervention in patients with adult spine deformity according to preoperative 5-item modified frailty index scores

PURPOSE

Frailty increases vulnerability to dependency and/or death, and is important in predicting the risk for adverse effects following adult spinal deformity (ASD) surgery. For easy determination of frailty, the 5-item modified frailty index (mFI-5) was established. However, there are few reports that show the relationship between frailty and mid-term operative outcomes after ASD surgery. The objective of this retrospective study is to determine the correlation of frailty using mFi-5 scores with postoperative medical complications, patient reported outcome measures (PROMs), and radiographic alignment 5 years after ASD surgery.

METHODS

208 patients were divided into robust (R), pre-frail (PF), and frail (F) groups based on mFI-5 scores. Postoperative medical complications, preoperative and 5-year follow-up PROMs and radiographic alignment were evaluated.

RESULTS

The study included 91, 79, and 38 patients in group R, PF, and F, respectively. There was no significant difference in age and sex. Discharge to care facility (16 (18%):21 (27%):16 (42%), p = 0.014) and postoperative cardiac complications (2 (2%):0 (0%):3 (8%), p = 0.031) were higher in frail patients. Preoperative ODI (38.3:45.3:54.7, p < 0.001) and SRS-22 (2.7:2.5:2.3, p = 0.004), 5-year postoperative ODI (27:27.2:37.9, p = 0.015), 5-year postoperative SVA (57.8°:78.5°:86.4°, p = 0.039) and 5-year postoperative TPA (23.9°:29.4°:29.5°, p = 0.011) were significantly worse in group F compared to group R.

CONCLUSION

Postoperatively, frail patients are more likely to have cardiac complications, inferior PROMs and deterioration of post-correction global spinal alignment. Preoperative assessment using mFI-5 is beneficial to individualize risks, optimize patients, and manage postoperative expectations.

LEVEL OF EVIDENCE: 3

Patient-specific rods in adult spinal deformity: a systematic review

PURPOSE

The purpose of this review was to evaluate the effectiveness of patient-specific rods for adult spinal deformity.

METHODS

A systematic review of the literature was performed through an electronic search of the PubMed, Scopus, and Web of Science databases. Human studies between 2012 and 2023 were included. Sample size, sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis (PI-LL), pelvic tilt (PT), operation time, blood loss, follow-up duration, and complications were recorded for each study when available.

RESULTS

Seven studies with a total of 304 adult spinal deformity patients of various etiologies were included. All studies reported SVA, and PT; two studies did not report PI-LL. Four studies reported planned radiographic outcomes. Two found a significant association between preoperative plan and postoperative outcome in all three outcomes. One found a significant association for PI-LL alone. The fourth found no significant associations. SVA improved in six of seven studies, PI-LL improved in all five, and three of seven studies found improved postoperative PT. Significance of these results varied greatly by study.

CONCLUSION

Preliminary evidence suggests potential benefits of PSRs in achieving optimal spino-pelvic parameters in ASD surgery. Nevertheless, conclusions regarding the superiority of PSRs over traditional rods must be judiciously drawn, given the heterogeneity of patients and study methodologies, potential confounding variables, and the absence of robust randomized controlled trials. Future investigations should concentrate on enhancing preoperative planning, standardizing surgical methodologies, isolating specific patient subgroups, and head-to-head comparisons with traditional rods to fully elucidate the impact of PSRs in ASD surgery.

A systematic review of pseudarthrosis and reoperation rates in minimally invasive adult spinal deformity correction

Background/objective

The recent development of minimally invasive surgical techniques (MIS) has made possible the correction of adult spinal deformity (ASD) with less blood loss and shorter hospital stays. However, minimally invasive placement of pedicle screws at the proximal level of the construct can increase pseudarthrosis risk, leading to implant failure, kyphosis, and reoperations. We aggregate existing literature to describe pseudarthrosis rates at the proximal thoracic or thoracolumbar junction in MIS and subsequent reoperation rates.

Methods

After a three-tied search strategy in PubMed, we identified 9 articles for study inclusion, describing outcomes from MIS correction of ASD, pseudarthrosis as complication, and surgery on 4+ levels. Baseline patient characteristics and combined rates of pseudarthrosis and reoperation were calculated.

Results

A total of 482 patients were studied with an average [range] age of 65.5 [60.4,72], 6.3 [4.4,11] levels fused per patient, follow-up time of 28.3 [12,39] months, and 64.8% females. Pseudarthrosis was reported in 28 of 482 pooled patients (5.8%) of which 15 of 374 pooled patients (4.0%) ultimately underwent a reoperation for pseudarthrosis. Post-operative characteristics included an estimated blood loss (EBL) of 527.1 [241,1466] mL, operating time of 297.9 [183,475] minutes, and length of stay of 7.7 [5,10] days. Among the papers comparing MIS to open surgery, all reported a significantly lower EBL in patients treated with MIS.

Conclusion

This analysis demonstrate a measurable pseudarthrosis risk when using MIS to treat ASD, overwhelming requiring reoperation. The benefits of MIS must be considered against the drawbacks of pseudarthrosis when determining ASD management.

Spinal Robotics in Adult Spinal Deformity Surgery: A Systematic Review

Spinal robotics have the potential to improve the consistency of outcomes in adult spinal deformity (ASD) surgery. The objective of this paper is to assess the accuracy of pedicle and S2 alar-iliac (S2AI) screws placed with robotic guidance in ASD patients. PubMed Central, Google Scholar, and an institutional library database were queried until May 2023. Articles were included if they described ASD correction via robotic guidance and pedicle and/or S2AI screw accuracy. Articles were excluded if they described pediatric/adolescent spinal deformity or included outcomes for both ASD and non-ASD patients without separating the data. Methodological quality was assessed using the Newcastle-Ottawa scale. Primary endpoints were pedicle screw accuracy based on the Gertzbein-Robbins Scale and self-reported accuracy percentages for S2AI screws. Data were extracted for patient demographics, operative details, and perioperative outcomes and assessed using descriptive statistics. Five studies comprising 138 patients were included (mean age 66.0 years; 85 females). A total of 1,508 screws were inserted using robotic assistance (51 S2AI screws). Two studies assessing pedicle screws reported clinically acceptable trajectory rates of 98.7% and 96.0%, respectively. Another study reported a pedicle screw accuracy rate of 95.5%. Three studies reported 100% accuracy across 51 total S2AI screws. Eight total complications and 4 reoperations were reported. Current evidence supports the application of robotics in ASD surgery as safe and effective for placement of both screw types. However, due to the paucity of data, a comprehensive assessment of its incremental benefit over other techniques cannot be made. Further work using expanded cohorts is merited.

Impact of obesity on adult spinal deformity (ASD) long-segment spinal fusion radiographic and clinical outcomes

STUDY DESIGN

Retrospective chart review of patients receiving long-segment fusion during a five-year period.

OBJECTIVE

To determine whether obese patients receive comparable benefits when receiving long-segment fusion compared to non-obese patients and to identify factors that may predict hardware failure and post-surgical complications among obese patients.

METHODS

Demographic, spinopelvic radiographic, patient-reported outcome measures (PROMs), and complications data was retrospectively collected from 120 patients who underwent long-segment fusion during a five-year period at one tertiary care medical center. Radiographic measurements were pelvic incidence, pelvic tilt (PT), lumbar lordosis, L4-S1 lordosis, thoracic kyphosis, sagittal vertical axis, PI-LL mismatch, and proximal junction cobb angle at upper instrumented vertebrae + 2 (UIV+2). PROMs were Oswestry disability index, numeric rating scale (NRS) Back Pain, NRS Leg Pain, RAND SF-36 pain, and RAND SF-36 physical functioning. Included patients were adults and had at least 2-years of postoperative follow-up. Descriptive and multivariate statistical analysis was performed with α = 0.05.

RESULTS

Patients with a BMI ≥ 30 (n=63) and patients with a BMI < 30 (n=57) demonstrated comparable improvements (P>0.05) for all spinopelvic radiographic measurements and PROMs. Each cohort demonstrated significant improvements from pre-assessment to post-assessment on nearly all spinopelvic radiographic measurements and PROMs (P<0.05), except PT and L4-S1 lordosis where neither group improved (p=0.95 and 0.58 for PT and P=0.23 and 0.11 for L4-S1 lordosis fornon-obese and obese cohorts respectively) and SF-36 physical functioning where the non-obese cohort not statistically improve (P=0.08). Patients with a BMI ≥ 30 demonstrated an increased incidence of cardiovascular complications (P=0.0293), acute kidney injury (P=0.0241), rod fractures (P=0.0293), and reoperations (P=0.0241) when compared to patients with a BMI < 30.

CONCLUSION

This study adds to a growing body of evidence linking demographic factors with risks of hardware failure. Further, this data challenges the assumption that obese patients may not receive sufficient benefit to be long-segment surgical candidates. However, given their elevated risk for post-operative and delayed hardware complications, obese patients should be appropriately counseling before undergoing surgery.

Characteristics of Spinal Morphology According to the "Current" and "Theoretical" Roussouly Classification Systems in a Diverse, Asymptomatic Cohort: Multi-Ethnic Alignment Normative Study (MEANS)

STUDY DESIGN

Cross-sectional cohort study.

OBJECTIVE

To classify spinal morphology using the "current" and "theoretical" Roussouly systems and assess sagittal alignment in an asymptomatic cohort.

METHODS

467 asymptomatic volunteers were recruited from 5 countries. Radiographic parameters were measured via the EOS imaging system. "Current" and "theoretical" Roussouly classification was assigned with sagittal whole spine imaging using sacral slope (SS), pelvic incidence (PI), and the lumbar apex. One-way analysis of variance (ANOVA) was performed to compare subject characteristics across Roussouly types, followed by post hoc Bonferroni correction.

RESULTS

Volunteers were categorized into 4 groups (Types 1-4) and 1 subgroup (Type 3 AP) using the "current" and "theoretical" Roussouly systems. The mean PI in "current" Roussouly groups was 40.8° (Type 1), 43.6° (Type 2), 52.4° (Type 3), 62.4° (Type 4), and 43.7° (Type 3AP). The mean PI in "theoretical" Roussouly groups was 36.5° (Type 1), 39.1°(Type 2), 52.5° (Type 3), 67.3° (Type 4), and 51.0° (Type 3AP). The difference in PI between "current" and "theoretical" Roussouly types was significant for Type 1 (P = .02), Type 2 (P < .001), Type 4 (P < .001), and Type 3AP (P < .001). 34.7% of subjects had a "current" Roussouly type different from the "theoretical" type. Type 3 theoretical shape had the most frequent mismatch, constituting 61.1% of the mismatched subjects. 51.5% of mismatched Type 3 become "current" Type 4.

CONCLUSION

The distribution of Roussouly types differs depending on whether the "current" or "theoretical" classification are employed. A sizeable proportion of volunteers exhibited current and theoretical type mismatch, highlighting the need to interpret sagittal alignment cautiously when utilizing the Roussouly system.

Defining the Post-Operative Progression of Degenerative Scoliosis: An Analysis of Cases without Instrument Failure

OBJECTIVE

The expected post-operative changes in radiographic alignment over time remain poorly defined in patients surgically treated for degenerative scoliosis without instrument failure. Here we aim to describe the optimal natural progression of radiographic degenerative scoliosis at multiple timepoints in patients treated with a transforaminal lumbar interbody fusion (TLIF).

METHODS

We identified an initial retrospective cohort of 114 patients treated with a TLIF for degenerative scoliosis between 2018 and 2022, with 39 patients ultimately meeting the imaging inclusion criteria. Patients who completed a primary or revision procedure with no evidence of instrument failure, proximal junctional kyphosis, or proximal junctional failure at last follow-up were included. Radiographic measurements of spinopelvic alignment were manually extracted from X-Ray scoliosis films.

RESULTS

Thirty-nine patients (mean age 62.6 ± 8.7, mean follow-up 2.9 years), of which 23 underwent a primary TLIF (Primary) and 16 a revision procedure (Revision), were analyzed. Patients in the Primary group experienced a durable improvement in Thoracolumbar Cobb angle (-25° ± 15°), Thoracic Kyphosis (10° ± 13°), and Pelvic Incidence/lumbar lordosis mismatch (PI/LL) (-19° ± 19°) through the first year of follow-up. In the Revision group, at one year follow-up, all measures of spinopelvic alignment except PI/LL mismatch had reverted to pre-operative levels. Thoracolumbar Cobb angle decreased to a significantly greater degree in the Primary group compared to the Revision group.

CONCLUSION

Primary TLIF operations without instrument failure consistently improve radiographic outcomes in three key measures through the first year. For revision procedures, there appears to be modest radiographic benefit at follow-up.

Pelvic Incidence as a Predictor of Proximal Junctional Failure in Patients Undergoing Anterior Column Realignment with Anterior Longitudinal Ligament Release to Restore Lordosis in Adult Spinal Deformity: A Retrospective Cohort Study

OBJECTIVE

To identify variables that may contribute to the development of proximal junctional failure (PJF) in patients with long lumbo-sacral and thoraco-lumbo-pelvic constructs undergoing anterior column realignment (ACR) with anterior longitudinal ligament release (ALLR).

METHODS

Data of patients with adult spinal deformity who underwent ACR with ALLR at L3-4 were collected retrospectively from medical records and a prospectively maintained spine research database between 2016 and 2022.

RESULTS

Eleven (41%) developed PJF at a mean of 24 ± 21 months from the index surgery. The cohort was then divided into 2 groups for analysis, 13 subjects in the high pelvic incidence (PI) group (defined as PI ≥ 55°) and 14 subjects in the low PI group (defined as PI < 55°). Visual Analog Scale for back pain and Oswestry Disability Index decreased from 9.5 to 2.1 and 61 to 10 in the high PI group, and from 8.9 to 2.4 and 60.9 to 10.3 in the low PI group, respectively. PI (P = 0.004), sacral slope (P = 0.005), and postoperative PI-lumbar lordosis mismatch (P = 0.02) were found to be significant predictors of PJF. The receiver operator curve revealed a cutoff PI value ≤ 53° (95% confidence interval: 52°-64°), below which the risk of PJF becomes significantly higher in patients undergoing ACR with ALLR at L3-4.

CONCLUSIONS

PI may be a predictor of PJF and highly correlates with ACR-ALLR levels. In patients undergoing L3-4 ACR-ALLR, a PI value of ≤53° is associated with a significantly elevated risk of PJF. Preoperative planning of ACR-ALLR level based on normal sagittal alignment in otherwise healthy individuals may mitigate the risk of PJF development in patients with adult spinal deformity treated with ACR-ALLR.

Approaches in Anterior Column Support in Adult Spinal Deformity Surgery: A Meta-Analysis of Clinical and Radiologic Outcomes

OBJECTIVE

This meta-analysis was conducted to compare anterior lumbar interbody fusion (ALIF) with transforaminal lumbar interbody fusion (TLIF) in terms of postoperative complications, improvement in radiographic parameters, and patient-reported outcomes.

METHODS

PubMed, Cochrane, and Google Scholar (pages 1-20) databases were searched up to June 2023. The studied outcomes were the rate of rod failures, rod failures requiring revision surgery, all complications, all revision surgeries, the change in pelvic tilt, sacral slope, Cobb angle, lumbar lordosis (LL), sagittal vertical axis, the postoperative pelvic incidence-LL, and LL, and the improvement in back pain and Oswestry Disability Index (ODI).

RESULTS

Six studies were included in this meta-analysis. ALIF showed higher postoperative lordosis (P = 0.003) and better improvement in ODI (P = 0.0001). No difference was seen in the remaining outcomes between ALIF and TLIF.

CONCLUSIONS

Although ALIF had better improvement in ODI, the mean difference was 6.5 points, which is below the minimal clinically important difference, stripping this result of any clinical value. Furthermore, even though ALIF had better postoperative lordosis, the change in LL postoperatively was not different between ALIF and TLIF. With no difference in complications, sagittal and coronal alignment, and patient-reported outcomes, TLIF was shown in this study to be favored instead of ALIF in adult spinal deformity surgery to avoid all the double approach-related comorbidity.

Evaluating Computer Vision, Large Language, and Genome-Wide Association Models in a Limited Sized Patient Cohort for Pre-Operative Risk Stratification in Adult Spinal Deformity Surgery

Background: Adult spinal deformities (ASD) are varied spinal abnormalities, often necessitating surgical intervention when associated with pain, worsening deformity, or worsening function. Predicting post-operative complications and revision surgery is critical for surgical planning and patient counseling. Due to the relatively small number of cases of ASD surgery, machine learning applications have been limited to traditional models (e.g., logistic regression or standard neural networks) and coarse clinical variables. We present the novel application of advanced models (CNN, LLM, GWAS) using complex data types (radiographs, clinical notes, genomics) for ASD outcome prediction. Methods: We developed a CNN trained on 209 ASD patients (1549 radiographs) from the Stanford Research Repository, a CNN pre-trained on VinDr-SpineXR (10,468 spine radiographs), and an LLM using free-text clinical notes from the same 209 patients, trained via Gatortron. Additionally, we conducted a GWAS using the UK Biobank, contrasting 540 surgical ASD patients with 7355 non-surgical ASD patients. Results: The LLM notably outperformed the CNN in predicting pulmonary complications (F1: 0.545 vs. 0.2881), neurological complications (F1: 0.250 vs. 0.224), and sepsis (F1: 0.382 vs. 0.132). The pre-trained CNN showed improved sepsis prediction (AUC: 0.638 vs. 0.534) but reduced performance for neurological complication prediction (AUC: 0.545 vs. 0.619). The LLM demonstrated high specificity (0.946) and positive predictive value (0.467) for neurological complications. The GWAS identified 21 significant (p < 10-5) SNPs associated with ASD surgery risk (OR: mean: 3.17, SD: 1.92, median: 2.78), with the highest odds ratio (8.06) for the LDB2 gene, which is implicated in ectoderm differentiation. Conclusions: This study exemplifies the innovative application of cutting-edge models to forecast outcomes in ASD, underscoring the utility of complex data in outcome prediction for neurosurgical conditions. It demonstrates the promise of genetic models when identifying surgical risks and supports the integration of complex machine learning tools for informed surgical decision-making in ASD.

Trends of the Oswestry Disability Index in Adult Spinal Deformity Patients: A 3-Year Study

BACKGROUND

Patients with adult spinal deformity (ASD) undergoing operative treatment may have varying degrees of improvement in patient-reported outcomes. The Oswestry Disability Index (ODI) assesses improvement in quality of life. We aim to measure longitudinal outcomes of ODI scores over 3 years to determine if early ODI scores predict late ODI scores and to analyze longitudinal changes in ODI scores.

METHODS

Two hundred thirty-five patients above the age of 18 who underwent surgical correction of ASD at a single institution from 2016 to 2021 and completed ODI questionnaires at follow-up appointments met inclusion criteria. ODI scores were included from follow-up visits at 0 months (immediately postoperative) and within ±1 month of 3, 6, 12, 18, 24, 30, and 36 months. Percent change in ODI from 0 months was calculated, and unpaired t tests were conducted.

RESULTS

ODI scores increased by 8.8% immediately postoperatively, and the percent change from preoperative ODI scores at each subsequent visit were as follows: -11.1% at 3 months, -21.4% at 6 months, -25.4% at 12 months, -28% at 18 months, -31.3% at 24 months, -25.7% at 30 months, and -36.5% at 36 months. ODI scores at each follow-up visit showed significant improvement from baseline (P < 0.001). There was an improvement in scores from 3 to 6 months (P = 0.04), but no significant difference in 6-month interval visits following 6 months.

CONCLUSIONS

Our results demonstrate a significant and sustained improvement in ODI scores over 3 years following surgical correction of ASD. ODI scores were stable after 6 months, indicating that ODI scores at 6 months may be predictive of scores out to 3 years postoperatively. Examining individual components of ODI sub-scores and comparing ODI results to other PROMs are critical to better assess long-term outcomes in ASD.

Patient-specific spinal rods in adult spinal deformity surgery reduce proximal junctional failure: a review of patient outcomes and surgical technique in a prospective observational cohort

Background

Spinal rods used for adult spinal deformity (ASD) correction are usually manufactured straight and bent manually during surgery. Pre-bent patient-specific spinal rods (PSSR) developed with software provide the surgeon with an intraoperative deformity correction consistent with the surgical plan. Our aim was to report clinical and radiological outcomes using PSSR. We investigated rates of junctional complications both proximally [kyphosis (PJK) and failure (PJF)] and distally [failure (DJF)].

Methods

Prospective case series of 20 consecutive patients who underwent ≥4 level ASD surgery with PSSR at a single institution between January 2019 and December 2022. Preoperative, 6-week, 6-month, 12-month, 24-month, and final follow-ups assessed patient satisfaction (Ottawa decision regret questionnaire) and patient reported outcome measures (PROMs) [visual analogue scale (VAS; Back/Leg), Oswestry disability index (ODI), and 12-Item Short Form Survey (SF-12)]. Sagittal spinopelvic parameters [sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence and lumbar lordosis mismatch (PI-LL)] measured by serial EOS scans were performed preoperatively then compared to planned correction and postoperative measures. Interoperative cages (narrow/wide) were placed for interbody support. PJK risk score assessed likelihood of developing kyphosis. Serial computed tomography (CT) imaging assessed complication (fusion/subsidence).

Results

The mean age of the patients (75% female) was 71.9±6.9 years, and the mean follow-up was 25.2±8.6 [7-40] months. Preoperative mean PROMs showed statistically significant overall improvement (P<0.001) postoperatively to final follow-up. Four patients without wide footprint cages at L4/5 or L5/S1, suffered DJF and reported regret undergoing surgery. Statistically significant difference (P<0.001) between preoperative and surgical plan in SVA and PI-LL but not in PT (P=0.058). No statistically significant difference in surgical plan versus the postoperative SVA, PI-LL, and PT (due to difficulty achieving the surgical plan, and also to maintaining the correction). One patient suffered PJF. There was a mean proximal kyphotic angle (PKA) of 17.8±13.0 degrees and PJK risk score of 3.7±1.0 with 40% who experienced PJK. No rod breakages were observed.

Conclusions

In this series, PSSR improved PROMs and treated ASD. Sagittal parameters planned preoperatively correlated with postoperative correction. PJF was reduced, compared to the literature (35%), but PJK was observed over time. DJF occurred and was related to the absence of interbody cages at the lumbosacral junction and decisional regret.

The Veterans Rand-12 Physical Composite Score Prognosticates Postoperative Clinical Outcomes in Patients Undergoing Anterior Cervical Discectomy and Fusion

OBJECTIVE

To determine prognostic value of preoperative Veterans RAND 12-Item Health Survey (VR-12) physical composite score (PCS) on outcomes in patients undergoing anterior cervical discectomy and fusion (ACDF).

METHODS

ACDF patients with preoperative VR-12 PCS formed 2 cohorts: VR-12 PCS <35 and VR-12 PCS ≥35. The following patient-reported outcome measures (PROMs) were gathered preoperatively and postoperatively up to 2 years: VR-12 mental composite score (MCS)/PCS, Neck Disability Index (NDI), Patient-Reported Outcomes Measurement Information System (PROMIS) PF, 9-Item Patient Health Questionnaire (PHQ-9), visual analog scale (VAS) neck/arm pain, and 12-Item Short Form Health Survey (SF-12) PCS/MCS. Comparing PROMs change with established thresholds determined achievement of minimum clinically important difference (MCID). Univariate analysis compared demographics, perioperative characteristics, and preoperative PROMs. Multivariable regression analysis compared postoperative PROMs and MCID achievement.

RESULTS

Of 174 patients, 83 had VR-12 PCS <35. Preoperatively, patients with reduced PF displayed lower patient-reported outcome scores in NDI, PHQ-9, and SF-12 MCS (P ≤ 0.008), but not in VAS arm. At 6 weeks postoperatively, these patients continued to score lower in NDI (P ≤ 0.014) and SF-12 PCS (P ≤ 0.001), among others. By the final check, most scores remained lower (P ≤ 0.002) except for PHQ-9 and VAS arm (P > 0.05). Greater improvements at 6 weeks postoperatively were especially noted in patients with lower initial VR-12 PCS for NDI, PROMIS PF, and SF-12 PCS (P < 0.05). However, by final follow-up, only PROMIS PF showed noteworthy improvement (P = 0.19). Regarding MCID achievement, significant differences were largely absent except in NDI, where patients with reduced PF exhibited more MCID achievement (P = 0.016).

CONCLUSIONS

ACDF patients with VR-12 PCS <35 experienced inferior PF, mental health, and disability postoperatively until final follow-up. There were no significant differences in postoperative improvement magnitude and MCID achievement. Results suggest that baseline VR-12 PCS in ACDF patients may indicate poorer PF, mental health, and disability postoperatively. However, VR-12 PCS does not limit extent of postoperative improvement.

The Effect of Visual Impairment on Postural Stability After Lumbar Spine Fracture: A Case Report and Review of the Literature

The role of vision in maintaining postural stability is crucial, and its loss, whether congenital or acquired, can significantly impact sensory-motor interactions, leading to musculoskeletal abnormalities and defective gait patterns. This case report discusses the complex interplay between visual impairment, post-traumatic kyphosis, and the development of spinal deformity in a 79-year-old blind patient. The patient sustained a simple fall resulting in an L1 compression fracture in 2016. Despite conservative treatment for the fracture, progressive spinal deformity became evident both clinically and radiographically. Further assessments, including evaluation of bone healing, facet arthroplasty, disc degeneration, and canal compromise, were performed. The patient's altered gait and postural abnormalities were indicative of the impact of visual impairment on postural stability. After addressing osteoporosis through endocrinology consultation and medical management, the patient underwent posterior spinal instrumentation and deformity correction, leading to a successful post-operative recovery with a return to baseline functional status. Visual impairment disrupts postural stability by limiting sensory input and prompting compensatory mechanisms, which may increase postural sway and instability. This abnormal gait further contributes to spinal deformities, and the fear of falling can exacerbate postural instability, limiting mobility. Over time, persistent postural imbalance leads to the creation of a state of continual asymmetric stress related to the spinal axis, which can progress to the development of spinal deformities, creating a self-perpetuating cycle.  This case underscores the significance of vision in postural stability and the adverse effects of visual impairment on spinal alignment. The development of spinal deformities in visually impaired individuals, especially in the presence of risk factors like osteoporosis, emphasizes the need for early intervention and postural training to prevent irreversible deformities. Decisions regarding surgical or non-surgical interventions for spinal deformities in visually impaired patients must consider multiple factors, including clinical symptoms, appearance, pain, functional limitations, and social issues. Future research should explore effective interventions for improving postural stability in visually impaired individuals and preventing the development of spinal deformity.

Artificial Intelligence to Preoperatively Predict Proximal Junction Kyphosis Following Adult Spinal Deformity Surgery: Soft Tissue Imaging May Be Necessary for Accurate Models

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

In a cohort of patients undergoing adult spinal deformity (ASD) surgery, we used artificial intelligence to compare three models of preoperatively predicting radiographic proximal junction kyphosis (PJK) using: (1) traditional demographics and radiographic measurements, (2) raw preoperative scoliosis radiographs, and (3) raw preoperative thoracic magnetic resonance imaging (MRI).

SUMMARY OF BACKGROUND DATA

Despite many proposed risk factors, PJK following ASD surgery remains difficult to predict.

MATERIALS AND METHODS

A single-institution, retrospective cohort study was undertaken for patients undergoing ASD surgery from 2009 to 2021. PJK was defined as a sagittal Cobb angle of upper-instrumented vertebra (UIV) and UIV+2>10° and a postoperative change in UIV/UIV+2>10°. For model 1, a support vector machine was used to predict PJK within 2 years postoperatively using clinical and traditional sagittal/coronal radiographic variables and intended levels of instrumentation. Next, for model 2, a convolutional neural network (CNN) was trained on raw preoperative lateral and posterior-anterior scoliosis radiographs. Finally, for model 3, a CNN was trained on raw preoperative thoracic T1 MRIs.

RESULTS

A total of 191 patients underwent ASD surgery with at least 2-year follow-up and 89 (46.6%) developed radiographic PJK within 2 years. Model 1: Using clinical variables and traditional radiographic measurements, the model achieved a sensitivity: 57.2% and a specificity: 56.3%. Model 2: a CNN with raw scoliosis x-rays predicted PJK with a sensitivity: 68.2% and specificity: 58.3%. Model 3: a CNN with raw thoracic MRIs predicted PJK with average sensitivity: 73.1% and specificity: 79.5%. Finally, an attention map outlined the imaging features used by model 3 elucidated that soft tissue features predominated all true positive PJK predictions.

CONCLUSIONS

The use of raw MRIs in an artificial intelligence model improved the accuracy of PJK prediction compared with raw scoliosis radiographs and traditional clinical/radiographic measurements. The improved predictive accuracy using MRI may indicate that PJK is best predicted by soft tissue degeneration and muscle atrophy.

Advances and Evolving Challenges in Spinal Deformity Surgery

BACKGROUND

Surgical intervention is a critical tool to address adult spinal deformity (ASD). Given the evolution of spinal surgical techniques, we sought to characterize developments in ASD correction and barriers impacting clinical outcomes.

METHODS

We conducted a literature review utilizing PubMed, Embase, Web of Science, and Google Scholar to examine advances in ASD surgical correction and ongoing challenges from patient and clinician perspectives. ASD procedures were examined across pre-, intra-, and post-operative phases.

RESULTS

Several factors influence the effectiveness of ASD correction. Standardized radiographic parameters and three-dimensional modeling have been used to guide operative planning. Complex minimally invasive procedures, targeted corrections, and staged procedures can tailor surgical approaches while minimizing operative time. Further, improvements in osteotomy technique, intraoperative navigation, and enhanced hardware have increased patient safety. However, challenges remain. Variability in patient selection and deformity undercorrection have resulted in heterogenous clinical responses. Surgical complications, including blood loss, infection, hardware failure, proximal junction kyphosis/failure, and pseudarthroses, pose barriers. Although minimally invasive approaches are being utilized more often, clinical validation is needed.

CONCLUSIONS

The growing prevalence of ASD requires surgical solutions that can lead to sustained symptom resolution. Leveraging computational and imaging advances will be necessary as we seek to provide comprehensive treatment plans for patients.

Rod angulation does not reflect sagittal curvature in adult spinal deformity surgery: comparison of lumbar lordosis and rod contouring

STUDY DESIGN

A retrospective study.

OBJECTIVE

Relationship between rod and spinal shape in the sagittal plane in adult spinal deformity (ASD) surgery.

BACKGROUND

Corrective surgery for adult spinal deformity (ASD) involves the use of contoured rods to correct and modify the spinal curvatures. Adequate rod bending is crucial for achieving optimal correction. The correlation between rods and spinal shape in long constructs has not been reported previously.

METHODS

We conducted a retrospective analysis of a prospective, multicenter database of patients who underwent surgery for ASD. The inclusion criteria were patients who underwent pelvic fixation and had an upper instrumented vertebra at or above T12. Pre- and post-operative standing radiographs were used to assess lumbar lordosis at the L4S1 and L1S1 levels. The angle between the tangents to the rod at the L1, L4, and S1 pedicles was calculated to determine the L4S1 and L1S1 rod lordosis. The difference between the lumbar lordosis (LL) and the rod lordosis (RL) was calculated as ΔL = LL-RL. The correlation between this difference (ΔL) and various characteristics was analyzed using descriptive and statistical methods.

RESULTS

Eighty-three patients were included in the study, resulting in 166 analyzed differences (ΔL) between the rod and spinal lordosis. The values for rod lordosis were found to be both greater and lesser than those of the spine but were mostly lower. The range for total ΔL was -24 °-30.9 °, with a mean absolute ΔL of 7.8 ° for L1S1 (standard deviation (SD) = 6.0) and 9.1 ° for L4S1 (SD = 6.8). In 46% of patients, both rods had a ΔL of over 5 °, and over 60% had at least one rod with a ΔL difference of over 5 °. Factors found to be related to a higher ΔL included postoperative higher lumbar lordosis, presence of osteotomies, higher corrected degrees, older age, and thinner rods. Multivariate analysis correlated only higher postoperative L1S1 lordosis with higher ΔL. No correlation was found between a higher ΔL and sagittal imbalance.

CONCLUSIONS

Variations between spinal and rod curvatures were observed despite the linear regression correlation. The shape of the rod does not seem to be predictive of the shape of the spine in the sagittal plane in ASD long-construct surgeries. Several factors, other than rod contouring, are involved in explaining the postoperative shape of the spine. The observed variation calls into question the fundamentals of the ideal rod concept.

Multiple-Rod Constructs in Adult Spinal Deformity Surgery: A Systematic Review and Meta-Analysis

The purpose of this research was to compare the therapeutic efficacy of multiple-rod constructs vis-a-vis 2-rod constructs in the treatment of adult spinal deformity. A systematic review and meta-analysis were performed to determine whether the multiple-rod construct outperformed the 2-rod construct. We initially retrieved 357 papers, but only 12 were chosen for further meta-analysis. The rod breakage rates in the multiple-rod and the 2-rod groups were 10.66% and 29.87%, respectively. The multiple-rod construct inhibited rod breakage (odds ratio [OR], 0.28; 95% confidence interval [CI], 0.19-0.41; p<0.001), pseudarthrosis (OR, 0.30; 95% CI, 0.18-0.50; p<0.001) and rod fracture at the osteotomy site (OR, 0.34; 95% CI, 0.13-0.89; p=0.03). Furthermore, the multiple-rod construct reduces the risk of revision surgery (OR, 0.38; 95% CI, 0.20-0.73; p=0.04) as well as the revision risk of pseudarthrosis/rod fracture in the multiple- rod group (OR, 0.31; 95% CI, 0.18-0.52; p<0.001), but increases the risk of caudal screw loosening (OR, 4.99; 95% CI, 1.87-13.30; p=0.001). There was no statistically significant difference in proximal junctional kyphosis (PJK) parameters (p=0.85), cerebrospinal fluid leakage (p=0.09), wound infection (p =0.71), age at surgery (p=0.62), gender distribution (p=0.93), body mass index (p =0.86), smoking status (p=0.05), hospital stay (p=0.09), osteoporosis (p=0.95), CoCr rod material (p=0.15), bone morphogenetic protein-2 (p=0.58), L5/S1 interbody fusion (p=0.07), high-grade osteotomies (p=0.07), the number of fusion levels (p=0.11), operation time (p=0.30), and blood loss volume (p=0.34). Regarding radiographic parameters, only preoperative sagittal vertical axis was found to be higher (weight means difference [WMD], 25.60; 95% CI, 15.43-35.77; p<0.001) in the multiple-rod group. There was no difference in preoperative Oswestry Disability Index (ODI) (WMD, -3.32; 95% CI, -7.38 to 0.73; p=0.11), but the multiple-rod group had a lower ODI at follow-up (WMD, -7.71; 95% CI, -11.62 to -3.86; p<0.001). Multiple-rod constructs could prevent rod breakage and pseudarthrosis while also lowering the revision rate, resulting in a better clinical outcome than the 2-rod construct. Nonetheless, due consideration should be given to PJK and screw loosening in multiple-rod constructs, possibly due to the increased stiffness caused by the multiple-rod structure.

Adult Spinal Deformity Correction in Patients with Parkinson Disease: Assessment of Surgical Complications, Reoperation, and Cost

BACKGROUND

Parkinson disease (PD) is a neurodegenerative disorder that manifests with postural instability and gait imbalance. Correction of spinal deformity in patients with PD presents unique challenges.

METHODS

The PearlDiver database was queried between 2010 and 2020 to identify adult patients with spinal deformity before undergoing deformity correction with posterior spinal fusion. Two cohorts were created representing patients with and without a preoperative diagnosis of PD. Outcome measures included reoperation rates, surgical technique, cost, surgical complications, and medical complications. Multivariable logistic regression adjusting for Charlson Comorbidity Index, age, gender, 3-column osteotomy, pelvic fixation, and number of levels fused was used to assess rates of reoperation and complications.

RESULTS

In total, 26,984 patients met the inclusion criteria and were retained for analysis. Of these patients, 725 had a diagnosis of PD before deformity correction. Patients with PD underwent higher rates of pelvic fixation (odds ratio [OR], 1.33; P < 0.001) and 3-column osteotomies (OR, 1.53; P < 0.001). On adjusted regression, patients with PD showed increased rates of reoperation at 1 year (OR, 1.37; P < 0.001), 5 years (OR, 1.32; P < 0.001), and overall (OR, 1.33; P < 0.001). Patients with PD also experienced an increased rate of medical complications within 30 days after deformity correction including deep venous thrombosis (OR, 1.60; P = 0.021), pneumonia (OR, 1.44; P = 0.039), and urinary tract infections (OR, 1.54; P < 0.001). Deformity correction in patients with PD was associated with higher 90-day cost (P = 0.007).

CONCLUSIONS

Patients with PD undergoing long fusion for deformity correction are at significantly increased risk of 30-day medical complications and revision procedures after 1 year, controlling for comorbidities, age, and invasiveness. Surgeons should consider the risk of complications, subsequent revision procedures, and increased cost.

Comparison of complications, revisions, spinopelvic parameters, and health-related quality of life after posterior spinal fusion using multiple-rod constructs or two-rod constructs for adult spinal deformity: a systematic review and meta-analysis

BACKGROUND

The incidence of mechanical complications is high in patients undergoing posterior spinal fusion (PSF) for adult spinal deformity (ASD), especially for cases with severe sagittal malalignment or a prior spinal fusion requiring three-column osteotomy (3-CO) or spinopelvic fixation (SPF). The purpose of this systematic review and meta-analysis was to compare the complications, revisions, radiographic spinopelvic parameters, health-related quality of life (HRQoL), and surgical data of PSF using multiple-rod constructs to those of two-rod constructs for the treatment of ASD.

METHODS

A comprehensive literature search was performed for relevant studies in PubMed, EMBASE, Web of Science, and the Cochrane Library. Complications, revisions, spinopelvic parameters, HRQoL, and surgical date were compared between patients with ASD who underwent PSF using multiple-rod constructs (multi-rod group) and two-rod constructs (two-rod group).

RESULTS

Ten studies, comprising 797 patients with ASD (399 in the multi-rod group and 398 in the two-rod group), were included. All these studies were retrospective cohort studies. There were no significant differences in the surgical, wound-related, and systemic complications between the groups. In the multi-rod group, we noted a significantly lower incidence of rod fracture (RR, 0.43; 95% CI 0.33 to 0.57, P < 0.01), pseudoarthrosis (RR, 0.38; 95% CI 0.28 to 0.53, P < 0.01), and revisions (RR, 0.44; 95% CI 0.33 to 0.58, P < 0.01); a superior restoration of PI-LL (WMD, 3.96; 95% CI 1.03 to 6.88, P < 0.01) and SVA (WMD, 31.53; 95% CI 21.16 to 41.90, P < 0.01); a better improvement of ODI score (WMD, 6.82; 95% CI 2.33 to 11.31, P < 0.01), SRS-22 total score (WMD, 0.44; 95% CI 0.06 to 0.83, P = 0.02), and VAS-BP score (WMD, 1.02; 95% CI 0.31 to 1.73, P < 0.01).

CONCLUSION

Compared with the two-rod constructs, PSF using multiple-rod constructs was associated with a lower incidence of mechanical complications, a lower revision rate, a superior restoration of sagittal alignment, and a better improvement of HRQoL, without increasing surgical invasiveness. Multiple-rod constructs should be routinely considered to for ASD patients, especially for cases with severe sagittal malalignment or a prior spinal fusion requiring 3-CO or SPF.

Time-Dependent Changes in Stiffness-Related Functional Disability After Long Segmental Fusion in Elderly Patients With Adult Spinal Deformity-Minimum 2-Year Follow-up Results

BACKGROUND

Although several studies were performed to measure stiffness-related functional disability (SRFD) after long segmental fusion for adult spinal deformity, the evaluation of SRFD was done at a single point in time. We do not know whether the disability will stay the same, worsen, or improve over time.

OBJECTIVE

To evaluate the time-dependent changes of SRFD and any factors affecting these changes.

METHODS

Patients who had ≥4-segment fusion with the sacrum were reviewed retrospectively. Specific Functional Disability Index (SFDI), consisting of a 12-item tool with 4 categories (sitting on the floor, sanitation activities, lower body activities, and moving activities), was used to assess the severity of SRFD. The SFDI taken at 3 months, 1 year, and 2 years postoperatively and at the last follow-up were used for evaluating the changes in SRFD. The presumed factors affecting these changes were analyzed.

RESULTS

This study included 116 patients. Total SFDI scores significantly improved from 3-month to the last follow-up. Among the 4-category of SFDI, sitting on the floor showed the highest scores followed by lower body activities, sanitation activities, and moving activities at all time points. All categories except for sitting on the floor showed significant improvement from 3 months until the last follow-up. This improvement was most pronounced between 3 months and 1 year. American Society of Anaesthesiologists grade was identified as the only factor affecting time-dependent changes.

CONCLUSION

SRFD was highest at 3 months, but it improved over time except for sitting on the floor. The improvement was observed greatest between 3 months and 1 year. Patients with less American Society of Anaesthesiologists grade experienced more improvement in SRFD.

Proximal Junctional Kyphosis or Failure After Adult Spinal Deformity Surgery - Review of Risk Factors and Its Prevention

Proximal junction kyphosis (PJK) is a common imaging finding after long-level fusion, and proximal junctional failure (PJF) is an aggravated form of the progressive disease spectrum of PJK. This includes vertebral fracture of upper instrumented vertebra (UIV) or UIV+1, instability between UIV and UIV+1, neurological deterioration requiring surgery. Many studies have reported on PJK and PJF after long segment instrumentation for adult spinal deformity (ASD). In particular, for spine deformity surgeons, risk factors and prevention strategies of PJK and PJF are very important to minimize reoperation. Therefore, this review aims to help reduce the occurrence of PJK and PJF by updating the latest contents of PJK and PJF by 2023, focusing on the risk factors and prevention strategies of PJK and PJF. We conducted a search on multiple database for articles published until February 2023 using the search keywords "proximal junctional kyphosis," "proximal junctional failure," "proximal junctional disease," and "adult spinal deformity." Finally, 103 papers were included in this study. Numerous factors have been suggested as potential risks for the development of PJK and PJF, including a high body mass index, inadequate postoperative sagittal balance and overcorrection, advanced age, pelvic instrumentation, and osteoporosis. Recently, with the increasing elderly population, sarcopenia has been emphasized. The quality and quantity of muscle in the surgical site have been suggested as new risk factor. Therefore, spine surgeon should understand the pathophysiology of PJK and PJF, as well as individual risk factors, in order to develop appropriate prevention strategies for each patient.

The Thoracolumbar Inflection Point in a Population of Asymptomatic Volunteers: A Multi-Ethnic Alignment Normative Study Cohort Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To show population variance in the Inflection Point (IP) and its role in defining maximum Thoracic Kyphosis (TK) and Lumbar Lordosis (LL).

METHODS

468 asymptomatic adult volunteers were included in the Multi-Ethnic Normative Alignment Study (MEANS). To find parameters correlating with IP, the vertebrae and discs were numbered such that C7 was 0, T1 was 1, with T1-T2 disc being 1.5, etc. Statistical analysis was performed by a correlation matrix for IP and the 9 other selected parameters along with linear regressions.

RESULTS

The overall mean IP was 12.44 approximately corresponding to T12-L1 disc with the median being 12.50, range was T8-L4. The cohort was then stratified by sex and ethnicity, but there was no significant difference in IP between groups. IP in younger subjects was 13 (L1), compared to 12.5 (T12-L1 disc) in older subjects (P < .05). IP was moderately correlated with the TK apex (r = .66). No strong correlation was found between IP and LL magnitude or apex, TK magnitude, sacral slope, or Pelvic Incidence (PI). In terms of other sagittal parameters, PI and LL demonstrated a significant positive correlation. PI and TK did not have a strong association.

CONCLUSIONS

The mean IP was at the T12-L1 disc, however IP ranged from T8 to L4. Older subjects tended to have a relatively more cephalad IP. No radiographic variable was found to be a strong predictor of the IP. TK apex was found to have a moderate correlation.

Radiographic Factors of Proximal Junctional Failure According to Age Groups in Adult Spinal Deformity

Background

Patient age has been associated with the development of proximal junctional failure (PJF). The characteristics of adult spinal deformity (ASD) are considered different between younger and older age groups. We hypothesized that the radiographic risk factors of PJF would be different according to age groups. This study aimed to evaluate different radiographic risk factors of PJF between two age groups undergoing thoracolumbar fusion for ASD.

Methods

ASD patients aged ≥ 60 years who underwent thoracolumbar fusion from the low thoracic level (T9-T12) to the sacrum were included. The minimum follow-up duration was 2 years. PJF was defined as proximal junctional angle (PJA) ≥ 20°, fixation failure, fracture, myelopathy, or necessity of revision surgery. Using various radiographic risk factors including age-adjusted ideal pelvic incidence (PI)-lumbar lordosis (LL), univariate and multivariate analyses were performed separately in two age groups: < 70 years and ≥ 70 years.

Results

A total of 186 patients (90.3% women) with a mean age of 69 years were enrolled. The mean follow-up duration was 67.4 months. PJF developed in 97 patients (52.2%). There were fractures in 53 patients, PJA ≥ 20° in 26, fixation failure in 12, and myelopathy in 6. PJF developed more frequently in patients 70 years or older than in those younger than 70 years. In patients aged less than 70 years, preoperative LL, PI-LL, and a change in LL were significant risk factors in univariate analysis. Multivariate analysis showed only a change in LL was significant for PJF development (odds ratio [OR], 1.025; p = 0.021). On the other hand, in patients 70 years or older, postoperative LL, postoperative PI-LL, and overcorrection relative to the conventional PI-LL target (within ± 10°) and age-adjusted ideal PI-LL target were significant risk factors. On multivariate analysis, only overcorrection of PI-LL relative to the age-adjusted ideal target was a single significant risk factor of PJF (OR, 5.250; p = 0.024).

Conclusions

In patients younger than 70 years, a greater change in LL was associated with PJF development regardless of PI-related values. However, in older patients, overcorrection of PI-LL relative to the age-adjusted PI-LL target was a significant risk factor of PJF.

Learning Curve for Minimally Invasive Scoliosis Surgery in Adolescent Idiopathic Scoliosis

OBJECTIVE

To evaluate the learning curve of minimally invasive scoliosis surgery (MISS) in patients with adolescent idiopathic scoliosis (AIS).

METHODS

A total of 76 AIS patients who underwent MISS were included from March 2015 to February 2017. The cases were divided chronologically into early period group (Group A, March 2015-February 2016, n = 31) and late period group (Group B, March 2016-February 2017, n = 45). Radiological parameters, operative parameters, and clinical outcomes were included in this study. The selected criteria for receiver operating characteristic analysis used to assess learning curve were mean operative time (≤389 minutes) and estimated blood loss (EBL) (≤948 mL).

RESULTS

The mean operative time was 389 minutes, and the EBL was 948 mL. The mean operative time was significantly reduced in the late period group (360 minutes) compared to the early period group (431 minutes) (P < 0.005). The mean EBL was significantly reduced for the late period group (798 mL) compared to the early period group (1164 mL) (P < 0.001). Forty-six cases were required to achieve the preset criteria (area under the curve 0.858; P < 0.001; sensitivity 0.778; specificity 0.796).

CONCLUSIONS

A mild learning curve was demonstrated in MISS for AIS with significant improvement in operative times and EBL over time. Experience of more than 46 cases of MISS was required to obtain proficient surgical skills for a trained surgeon of conventional open scoliosis surgery.

Significance of paraspinal muscle quality in risk between single and multiple osteoporotic vertebral fractures

PURPOSE

To compare paraspinal muscle quality between patients with single and multiple osteoporotic vertebral fractures (OVFs) and evaluate the role of the paraspinal muscles in OVFs.

METHODS

A total of 262 consecutive patients with OVFs were retrospectively analyzed in two groups: those with single OVF (n = 173) and those with multiple OVFs (n = 89). The cross-sectional area (CSA) and fatty degeneration of the paraspinal muscles were calculated from axial T2-weighted magnetic resonance imaging at the level of the L4 upper endplate by manual tracing in ImageJ software. Pearson's correlation analysis was performed to analyze correlations of paraspinal muscle quality to multiple OVFs.

RESULTS

FD in all the paraspinal muscles was significantly higher in the multiple OVF group than the single OVF group (all p < 0.005). The functional CSA (fCSA) of the paraspinal muscles was significantly lower in the multiple OVF group than the single OVF group (all Ps < 0.001), except for the erector spine (p = 0.304). The Pearson's correlation analysis showed significant positive inter-correlations for the fCSAs of all the paraspinal muscles and the occurrence of multiple OVFs.

CONCLUSIONS

The pure muscle volumes of the multifidus, psoas major, and quadratus lumborum were lower in patients with multiple OVFs than in those with a single OVF. Furthermore, the inter-correlation among all the paraspinal muscles indicate that the muscle-bone crosstalk profoundly existed in vertebral fracture cascade. Therefore, special attention to paraspinal muscle quality is needed to prevent progression to multiple OVFs.

No Significant Radiological Signs of Adult Spinal Deformity Progression after a Mean of 11 Years of Follow-Up Following Harrington Rod Instrumentation Removal and Watchful Waiting

The study aimed to assess long-term radiological outcomes in patients from our institution who were primarily treated for adolescent idiopathic scoliosis with surgical correction using Harrington rod (HR) instrumentation, and afterward with watchful waiting of residual spinal deformity after HR removal, whereby no patient consented to spinal deformity correction. A single-institution case series of 12 patients was retrospectively evaluated. Preoperative and most recent post-instrumentation removal radiographic measurements were compared, along with baseline characteristics. The average age of patients (all females) at the time of HR instrumentation removal was 38 ± 10 years (median 40, range 19-54). The mean follow-up from the HR instrumentation implantation to the HR instrumentation removal was 21 ± 10 years (median 25, range 2-37), with a further mean of 11 ± 10 years (median 7, range 2-36) of follow-up following HR instrumentation removal and watchful waiting. No significant change in radiological parameters was observed: LL (p = 0.504), TK (p = 0.164), PT (p = 0.165), SS (p = 0.129), PI (p = 0.174), PI-LL (p = 0.291), SVA (p = 0.233), C7-CSVL (p = 0.387), SSA (p = 0.894), TPA (p = 0.121), and coronal Cobb angle (proximal (p = 0.538), main thoracic (p = 0.136), and lumbar (p = 0.413)). No significant change in coronal or sagittal parameters was observed in this single-institution long-term radiological outcome study of adults following HR instrumentation removal and watchful waiting of residual spinal deformity.

Comparison of staged LLIF combined with posterior instrumented fusion with posterior instrumented fusion alone for the treatment of adult degenerative lumbar scoliosis with sagittal imbalance

BACKGROUND

To retrospectively compare the clinical and radiological outcomes of staged lateral lumbar interbody fusion (LLIF) combined with posterior instrumented fusion(PIF)with PIF alone for the treatment of adult degenerative lumbar scoliosis (ADLS) with sagittal imbalance.

METHODS

ADLS patients with sagittal imbalance underwent corrective surgery were included and divided into staged group (underwent multilevel LLIF in the first-stage and PIF in the second-stage) and control group (PIF alone). The clinical and radiological outcomes were evaluated and compared between the two groups.

RESULTS

Forty-five patients with an average age of 69.7±6.3 years were enrolled, including 25 in the staged group and 20 in the control group. Compared with preoperative values, patients in both groups achieved significant improvement in terms of ODI, VAS back, VAS leg and spinopelvic parameters after surgery, which were maintained well during the follow-up period. Compared with control group, total operative time in the staged group was longer, but the amounts of blood loss and blood transfusion were reduced. The average posterior fixation segments were 6.20±1.78 in the staged group and 8.25±1.16 in the control group (P<0.01), respectively. Posterior column osteotomy (PCO) was performed in 9 patients (36%) in the staged group, while PCO and/or pedicle subtraction osteotomy were performed in 15 patients (75%) in the control group (P<0.01). There was no difference in complications between the two groups.

CONCLUSION

Both surgical strategies were effective for the treatment of ADLS with sagittal imbalance. However, staged treatment was less invasive, which reduced the number of posterior fixation segments and osteotomy requirement.

Biomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery

Background: Posterior long spinal fusion was the common procedure for adult spinal deformity (ASD). Although the application of sacropelvic fixation (SPF), the incidence of pseudoarthrosis and implant failure is still high in long spinal fusion extending to lumbosacral junction (LSJ). To address these mechanical complications, advanced SPF technique by multiple pelvic screws or multirod construct has been recommended. This was the first study to compare the biomechanical performance of combining multiple pelvic screws and multirod construct to other advanced SPF constructs for the augmentation of LSJ in long spinal fusion surgery through finite element (FE) analysis.

Methods: An intact lumbopelvic FE model based on computed tomography images of a healthy adult male volunteer was constructed and validated. The intact model was modified to develop five instrumented models, all of which had bilateral pedicle screw (PS) fixation from L1 to S1 with posterior lumbar interbody fusion and different SPF constructs, including No-SPF, bilateral single S2-alar-iliac (S2AI) screw and single rod (SS-SR), bilateral multiple S2AI screws and single rod (MS-SR), bilateral single S2AI screw and multiple rods (SS-MR), and bilateral multiple S2AI screws and multiple rods (MS-MR). The range of motion (ROM) and stress on instrumentation, cages, sacrum, and S1 superior endplate (SEP) in flexion (FL), extension (EX), lateral bending (LB), and axial rotation (AR) were compared among models.

Results: Compared with intact model and No-SPF, the ROM of global lumbopelvis, LSJ, and sacroiliac joint (SIJ) was decreased in SS-SR, MS-SR, SS-MR, and MS-MR in all directions. Compared with SS-SR, the ROM of global lumbopelvis and LSJ of MS-SR, SS-MR, and MS-MR further decreased, while the ROM of SIJ was only decreased in MS-SR and MS-MR. The stress on instrumentation, cages, S1-SEP, and sacrum decreased in SS-SR, compared with no-SPF. Compared with SS-SR, the stress in EX and AR further decreased in SS-MR and MS-SR. The most significantly decreased ROM and stress were observed in MS-MR.

Conclusion: Both multiple pelvic screws and multirod construct could increase the mechanical stability of LSJ and reduce stress on instrumentation, cages, S1-SEP, and sacrum. The MS-MR construct was the most adequate to reduce the risk of lumbosacral pseudarthrosis, implant failure, and sacrum fracture. This study may provide surgeons with important evidence for the application of MS-MR construct in the clinical settings.

[Effectiveness of three-dimensional visible technique without fluoroscopy versus two-dimensional fluoroscopy in reduction of unstable pelvic fractures]

Objective

To compare the reduction qualities of three-dimensional visible technique without fluoroscopy and two-dimensional fluoroscopy for unstable pelvic fractures during operations.

Methods

The clinical data of 40 patients with unstable pelvic fractures, who met the selection criteria in three clinical centers between June 2021 and September 2022, were retrospectively analyzed. According to the reduction methods, the patients were divided into two groups. Twenty patients in trial group were treated with unlocking closed reduction system combined with three-dimensional visible technique without fluoroscopy; 20 patients in control group with unlocking closed reduction system under two-dimensional fluoroscopy. There was no significant difference in the gender, age, injury mechanism, Tile type of fracture, Injury Severity Score (ISS), and the time between injury to operation between the two groups ( P>0.05). The qualities of fracture reduction according to the Matta criteria, operative time, intraoperative blood loss, fracture reduction time, times of fluoroscopy, and System Usability Scale (SUS) score were recorded and compared.

Results

All operations were successfully completed in both groups. According to the Matta criteria, the qualities of fracture reduction were rated as excellent in 19 patients (95%) in trial group, which was better than that in the control group (13 cases, 65%), with a significant difference ( χ ²=3.906, P=0.048). The operative time and intraoperative blood loss had no significant differences between the two groups ( P>0.05). The fracture reduction time and times of fluoroscopy were significantly less in trial group than in control group ( P<0.05), and SUS score in trial group was significantly higher in trial group than in control group ( P<0.05).

Conclusion

Compared to using unlocking closed reduction system under two-dimensional fluoroscopy, three-dimensional visible technique without fluoroscopy can significantly improve the reduction quality of unstable pelvic fractures without prolonging the operative time, and is valuable to reduce iatrogenic radiation exposure for patients and medical workers.

Re-stooping after Corrective Osteotomy in Patients with Ankylosing Spondylitis

Background

Corrective osteotomy is an effective surgery for correcting posture in patients with ankylosing spondylitis (AS). Despite satisfactory correction, some patients experience re-stooping during follow-up. However, there have been no studies on re-stooping in AS. We aimed to analyze the factors that affect re-stooping.

Methods

Fifty patients (50 cases) who underwent thoracolumbar corrective osteotomy for AS from March 2006 to April 2018 were analyzed. We defined re-stooping as global kyphosis that recurs after corrective osteotomy. The patients were divided into two groups based on the ratio of correction loss: non-re-stooping group (N group) and re-stooping group (R group). We analyzed the demographic data and radiological parameters, such as modified Stoke Ankylosing Spondylitis Spine Score (mSASSS), sagittal vertical axis, and various angles. We also investigated the factors affecting re-stooping by analyzing the correlation between the ratio of correction loss and various factors.

Results

A significant difference was seen in the change in the mSASSS from before surgery to the last follow-up between the N group (2.87 ± 3.08) and the R group (9.20 ± 5.44). In multivariate analysis, only the change in the mSASSS from before surgery to the last follow-up was significantly correlated with the ratio of correction loss.

Conclusions

Thoracolumbar corrective osteotomy seems to provide high satisfaction among patients with AS but can lead to re-stooping during follow-up. The change in mSASSS was related with re-stooping in the current study. We recommend active rehabilitative exercises and appropriate medication depending on the patient's condition, which may help delay the postoperative progression of AS.

Comparison of Korean Body Image Questionnaires in Adolescent Idiopathic Scoliosis

STUDY DESIGN

A prospective study.

PURPOSE

To obtain the results of four body image questionnaires analyzed for validity in Korean and compare them to radiographic findings and quality of life scores.

OVERVIEW OF LITERATURE

Each of the four body image questionnaires has been studied, but comparative studies of each other are rare.

METHODS

Adolescent idiopathic scoliosis (AIS) patients ages 10 to 19 years completed the Korean version of the Quality of Life Profile for Spinal Deformities (K-QLPSD), the Scoliosis Research Society-22 self-image subscale (K-SRS-22-si), Korean version of the Spinal Appearance Questionnaire (K-SAQ), Korean version of the Body Image Disturbance Questionnaire-Scoliosis (K-BIDQ-S), and Korean version of the Italian Spine Youth Quality of Life (K-ISYQOL). Four body image questionnaires were compared with K-ISYQOL and radiographic major curve magnitude, coronal balance, and sagittal balance. Spearman's correlation was performed to compare the four body image questionnaires.

RESULTS

The study included 84 AIS patients, with a mean age of 12.6 years and a major Cobb angle of 29.4°. The four surveys were correlated with major curve magnitude and K-ISYQOL. K-SAQ and K-BIDQ-S were correlated better than K-QLPSD, and K-SRS-22-si was correlated with K-ISYQOL. The four surveys were moderately correlated with major curve magnitude, but there was no correlation with age, coronal balance, and sagittal balance.

CONCLUSIONS

K-SAQ and K-BIDQ-S correlate better with K-ISYQOL than K-QLPSD and K-SRS-22-si.