The Adult Deformity Surgery Complexity Index (ADSCI): a valid tool to quantify the complexity of posterior adult spinal deformity surgery and predict postoperative complications

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.

Development and validation of a point-of-care clinical risk score to predict surgical site infection following open spinal fusion

Background

Surgical site infection (SSI) after open spine surgery increases healthcare costs and patient morbidity. Predictive analytics using large databases can be used to develop prediction tools to aid surgeons in identifying high-risk patients and strategies for optimization. The purpose of this study was to develop and validate an SSI risk-assessment score for patients undergoing open spine surgery.

Methods

The Premier Healthcare Database of adult open spine surgery patients (n = 157,664; 2,650 SSIs) was used to create an SSI risk scoring system using mixed effects logistic regression modeling. Full and reduced multilevel logistic regression models were developed using patient, surgery or facility predictors. The full model used 38 predictors and the reduced used 16 predictors. The resulting risk score was the sum of points assigned to 16 predictors.

Results

The reduced model showed good discriminatory capability (C-statistic = 0.75) and good fit of the model ([Pearson Chi-square/DF] = 0.90, CAIC=25,517) compared to the full model (C-statistic = 0.75, [Pearson Chi-square/DF] =0.90, CAIC=25,578). The risk scoring system, based on the reduced model, included the following: female (5 points), hypertension (4), blood disorder (8), peripheral vascular disease (9), chronic pulmonary disease (6), rheumatic disease (16), obesity (12), nicotine dependence (5), Charlson Comorbidity Index (2 per point), revision surgery (14), number of ICD-10 procedures (1 per procedure), operative time (1 per hour), and emergency/urgent surgery (12). A final risk score as the sum of the points for each surgery was validated using a 1,000-surgery random hold-out (independent from the study cohort) sample (C-statistic = 0.77).

Conclusions

The resulting SSI risk score composed of readily obtainable clinical information could serve as a strong prediction tool for SSI in preoperative settings when open spine surgery is considered.

Patient-Reported Outcomes After Complex Adult Spinal Deformity Surgery: 5-Year Results of the Scoli-Risk-1 Study

STUDY DESIGN

Prospective cohort.

OBJECTIVE

To prospectively evaluate PROs up to 5-years after complex ASD surgery.

METHODS

The Scoli-RISK-1 study enrolled 272 ASD patients undergoing surgery from 15 centers. Inclusion criteria was Cobb angle of >80°, corrective osteotomy for congenital or revision deformity, and/or 3-column osteotomy. The following PROs were measured prospectively at intervals up to 5-years postoperative: ODI, SF36-PCS/MCS, SRS-22, NRS back/leg. Among patients with 5-year follow-up, comparisons were made from both baseline and 2-years postoperative to 5-years postoperative. PROs were analyzed using mixed models for repeated measures.

RESULTS

Seventy-seven patients (28.3%) had 5-year follow-up data. Comparing baseline to 5-year data among these 77 patients, significant improvement was seen in all PROs: ODI (45.2 vs. 29.3, P < 0.001), SF36-PCS (31.5 vs. 38.8, P < 0.001), SF36-MCS (44.9 vs. 49.1, P = 0.009), SRS-22-total (2.78 vs. 3.61, P < 0.001), NRS-back pain (5.70 vs. 2.95, P < 0.001) and NRS leg pain (3.64 vs. 2.62, P = 0.017). In the 2 to 5-year follow-up period, no significant changes were seen in any PROs. The percentage of patients achieving MCID from baseline to 5-years were: ODI (62.0%) and the SRS-22r domains of function (70.4%), pain (63.0%), mental health (37.5%), self-image (60.3%), and total (60.3%). Surprisingly, mean values (P > 0.05) and proportion achieving MCID did not differ significantly in patients with major surgery-related complications compared to those without.

CONCLUSIONS

After complex ASD surgery, significant improvement in PROs were seen at 5-years postoperative in ODI, SF36-PCS/MCS, SRS-22r, and NRS-back/leg pain. No significant changes in PROs occurred during the 2 to 5-year postoperative period. Those with major surgery-related complications had similar PROs and proportion of patients achieving MCID as those without these complications.

Failure in Adult Spinal Deformity Surgery: A Comprehensive Review of Current Rates, Mechanisms, and Prevention Strategies

STUDY DESIGN

Literature review.

OBJECTIVE

The aim of this review is to summarize recent literature on adult spinal deformity (ASD) treatment failure as well as prevention strategies for these failure modes.

SUMMARY OF BACKGROUND DATA

There is substantial evidence that ASD surgery can provide significant clinical benefits to patients. The volume of ASD surgery is increasing, and significantly more complex procedures are being performed, especially in the aging population with multiple comorbidities. Although there is potential for significant improvements in pain and disability with ASD surgery, these procedures continue to be associated with major complications and even outright failure.

METHODS

A systematic search of the PubMed database was performed for articles relevant to failure after ASD surgery. Institutional review board approval was not needed.

RESULTS

Failure and the potential need for revision surgery generally fall into 1 of 4 well-defined phenotypes: clinical failure, radiographic failure, the need for reoperation, and lack of cost-effectiveness. Revision surgery rates remain relatively high, challenging the overall cost-effectiveness of these procedures.

CONCLUSION

By consolidating the key evidence regarding failure, further research and innovation may be stimulated with the goal of significantly improving the safety and cost-effectiveness of ASD surgery.

Individual differences in postoperative recovery trajectories for adult symptomatic lumbar scoliosis

OBJECTIVE

The Adult Symptomatic Lumbar Scoliosis-1 (ASLS-1) trial demonstrated the benefit of adult symptomatic lumbar scoliosis (ASLS) surgery. However, the extent to which individuals differ in their postoperative recovery trajectories is unknown. This study's objective was to evaluate variability in and factors moderating recovery trajectories after ASLS surgery.

METHODS

The authors used longitudinal, multilevel models to analyze postoperative recovery trajectories following ASLS surgery. Study outcomes included the Oswestry Disability Index (ODI) score and Scoliosis Research Society-22 (SRS-22) subscore, which were measured every 3 months until 2 years postoperatively. The authors evaluated the influence of preoperative disability level, along with other potential trajectory moderators, including radiographic, comorbidity, pain/function, demographic, and surgical factors. The impact of different parameters was measured using the R2, which represented the amount of variability in ODI/SRS-22 explained by each model. The R2 ranged from 0 (no variability explained) to 1 (100% of variability explained).

RESULTS

Among 178 patients, there was substantial variability in recovery trajectories. Applying the average trajectory to each patient explained only 15% of the variability in ODI and 21% of the variability in SRS-22 subscore. Differences in preoperative disability (ODI/SRS-22) had the strongest influence on recovery trajectories, with patients having moderate disability experiencing the greatest and most rapid improvement after surgery. Reflecting this impact, accounting for the preoperative ODI/SRS-22 level explained an additional 56%-57% of variability in recovery trajectory, while differences in the rate of postoperative change explained another 7%-9%. Among the effect moderators tested, pain/function variables-such as visual analog scale back pain score-had the biggest impact, explaining 21%-25% of variability in trajectories. Radiographic parameters were the least influential, explaining only 3%-6% more variance than models with time alone. The authors identified several significant trajectory moderators in the final model, such as significant adverse events and the number of levels fused.

CONCLUSIONS

ASLS patients have highly variable postoperative recovery trajectories, although most reach steady state at 12 months. Preoperative disability was the most important influence, although other factors, such as number of levels fused, also impacted recovery.

Combined anterior-posterior versus all-posterior approaches for adult spinal deformity correction: a matched control study

PURPOSE

Anterior approaches are gaining popularity for adult spinal deformity (ASD) surgeries especially with the introduction of hyperlordotic cages and improvement in MIS techniques. Combined Approaches provide powerful segmental sagittal correction potential and increase the surface area available for fusion in ASD surgery, both of which would improve overall. This is the first study directly comparing surgical outcomes between combined anterior-posterior approaches and all-posterior approach in a matched ASD population.

METHODS

This is a retrospective matched control cohort analysis with substitution using a multicenter prospectively collected ASD data of patients with > 2 year FU. Matching criteria include: age, American Society of Anesthesiologists Score, Lumbar Cobb angle, sagittal deformity (Global tilt) and ODI.

RESULTS

In total, 1024 ASD patients were available for analysis. 29 Combined Approaches patients met inclusion criteria, and only 22 could be matched (1:2 ratio). Preoperative non-matched demographical, clinical, surgical and radiological parameters were comparable between both groups. Combined approaches had longer surgeries (548 mns vs 283) with more blood loss (2850 ml vs 1471) and needed longer ICU stays (74 h vs 27). Despite added morbidity, they had comparable complication rates but with significantly less readmissions (9.1% vs 38.1%) and reoperations (18.2% vs 43.2%) at 2 years. Combined Approaches achieved more individualised and harmonious deformity correction initially. At the 2 years control, Combined Approaches patients reported better outcomes as measured by COMI and SRS scores. This trend was maintained at 3 years.

CONCLUSION

Despite an increased initial surgical invasiveness, combined approaches seem to achieve more harmonious correction with superior sagittal deformity control; they need fewer revisions and have improved long-term functional outcomes when compared to all-posterior approaches for ASD deformity correction.

Surgeons' risk perception in ASD surgery: The value of objective risk assessment on decision making and patient counselling

BACKGROUND

Surgeons often rely on their intuition, experience and published data for surgical decision making and informed consent. Literature provides average values that do not allow for individualized assessments. Accurate validated machine learning (ML) risk calculators for adult spinal deformity (ASD) patients, based on 10 year multicentric prospective data, are currently available. The objective of this study is to assess surgeon ASD risk perception and compare it to validated risk calculator estimates.

METHODS

Nine ASD complete (demographics, HRQL, radiology, surgical plan) preoperative cases were distributed online to 100 surgeons from 22 countries. Surgeons were asked to determine the risk of major complications and reoperations at 72 h, 90 d and 2 years postop, using a 0-100% risk scale. The same preoperative parameters circulated to surgeons were used to obtain ML risk calculator estimates. Concordance between surgeons' responses was analyzed using intraclass correlation coefficients (ICC) (poor < 0.5/excellent > 0.85). Distance between surgeons' and risk calculator predictions was assessed using the mean index of agreement (MIA) (poor < 0.5/excellent > 0.85).

RESULTS

Thirty-nine surgeons (74.4% with > 10 years' experience), from 12 countries answered the survey. Surgeons' risk perception concordance was very low and heterogeneous. ICC ranged from 0.104 (reintervention risk at 72 h) to 0.316 (reintervention risk at 2 years). Distance between calculator and surgeon prediction was very large. MIA ranged from 0.122 to 0.416. Surgeons tended to overestimate the risk of major complications and reintervention in the first 72 h and underestimated the same risks at 2 years postop.

CONCLUSIONS

This study shows that expert surgeon ASD risk perception is heterogeneous and highly discordant. Available validated ML ASD risk calculators can enable surgeons to provide more accurate and objective prognosis to adjust patient expectations, in real time, at the point of care.

Adult Spinal Deformity Surgery and Frailty: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

Adult spinal deformity (ASD) can be a debilitating condition with a profound impact on patients' health-related quality of life (HRQoL). Many reports have suggested that the frailty status of a patient can have a significant impact on the outcome of the surgery. The present review aims to identify all pre-operative patient-specific frailty markers that are associated with postoperative outcomes following corrective surgery for ASD of the lumbar and thoracic spine.

METHODS

A systematic review of the literature was performed to identify findings regarding pre-operative markers of frailty and their association with postoperative outcomes in patients undergoing ASD surgery of the lumbar and thoracic spine. The search was performed in the following databases: PubMed, Embase, Cochrane and CINAHL.

RESULTS

An association between poorer performance on frailty scales and worse postoperative outcomes. Comorbidity indices were even more frequently employed with similar patterns of association between increased comorbidity burden and postoperative outcomes. Regarding the assessment of HRQoL, worse pre-operative ODI, SF-36, SRS-22 and NRS were shown to be predictors of post-operative complications, while ODI, SF-36 and SRS-22 were found to improve post-operatively.

CONCLUSIONS

The findings of this review highlight the true breadth of the concept of "frailty" in ASD surgical correction. These parameters, which include frailty scales and various comorbidity and HRQoL indices, highlight the importance of identifying these factors preoperatively to ensure appropriate patient selection while helping to limit poor postoperative outcomes.

Quality metrics in adult spinal deformity surgery over the last decade: a combined analysis of the largest prospective multicenter data sets

OBJECTIVE

The reported rate of complications and cost of adult spinal deformity (ASD) surgery, associated with an exponential increase in the number of surgeries, cause alarm among healthcare payers and providers worldwide. The authors conjointly analyzed the largest prospective available ASD data sets to define trends in quality-of-care indicators (complications, reinterventions, and health-related quality of life [HRQOL] outcomes) since 2010.

METHODS

This is an observational prospective longitudinal cohort study. Patients underwent surgery between January 2010 and December 2016, with > 2 years of follow-up data. Demographic, surgical, radiological, and HRQOL (i.e., Oswestry Disability Index, SF-36, Scoliosis Research Society-22r) data obtained preoperatively and at 3, 6, 12, and 24 months after surgery were evaluated. Trends and changes in indicators were analyzed using local regression (i.e., locally estimated scatterplot smoothing [LOESS]) and adjusted odds ratio (OR).

RESULTS

Of the 2286 patients included in the 2 registries, 1520 underwent surgery between 2010 and 2016. A total of 1151 (75.7%) patients who were treated surgically at 23 centers in 5 countries met inclusion criteria. Patient recruitment increased progressively (2010-2011 vs 2015-2016: OR 1.64, p < 0.01), whereas baseline clinical characteristics (age, American Society of Anesthesiologists class, HRQOL scores, sagittal deformity) did not change. Since 2010 there has been a sustained reduction in major and minor postoperative complications observed at 90 days (major: OR 0.59; minor: OR 0.65; p < 0.01); at 1 year (major: OR 0.52; minor: 0.75; p < 0.01); and at 2 years of follow-up (major: OR 0.4; minor: 0.80; p < 0.01) as well as in the 2-year reintervention rate (OR 0.41, p < 0.01). Simultaneously, there has been a slight improvement in the correction of sagittal deformity (i.e., pelvic incidence-lumbar lordosis mismatch: OR 1.11, p = 0.19) and a greater gain in quality of life (i.e., Oswestry Disability Index 26% vs 40%, p = 0.02; Scoliosis Research Society-22r, self-image domain OR 1.16, p = 0.13), and these are associated with a progressive reduction of surgical aggressiveness (number of fused segments: OR 0.81, p < 0.01; percent pelvic fixation: OR 0.66, p < 0.01; percent 3-column osteotomies: OR 0.63, p < 0.01).

CONCLUSIONS

The best available data show a robust global improvement in quality metrics in ASD surgery over the last decade. Surgical complications and reoperations have been reduced by half, while improvement in disability increased and correction rates were maintained, in patients with similar baseline characteristics.

A Risk-Benefit Analysis of Increasing Surgical Invasiveness Relative to Frailty Status in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective review of a prospectively enrolled multicenter Adult Spinal Deformity (ASD) database.

OBJECTIVE

Investigate invasiveness and outcomes of ASD surgery by frailty state.

SUMMARY OF BACKGROUND DATA

The ASD Invasiveness Index incorporates deformity-specific components to assess correction magnitude. Intersections of invasiveness, surgical outcomes, and frailty state are understudied.

METHODS

ASD patients with baseline and 3-year (3Y) data were included. Logistic regression analyzed the relationship between increasing invasiveness and major complications or reoperations and meeting minimal clinically important differences (MCID) for health-related quality-of-life measures at 3Y. Decision tree analysis assessed invasiveness risk-benefit cutoff points, above which experiencing complications or reoperations and not reaching MCID were higher. Significance was set to P < 0.05.

RESULTS

Overall, 195 of 322 patients were included. Baseline demographics: age 59.9 ± 14.4, 75% female, BMI 27.8 ± 6.2, mean Charlson Comorbidity Index: 1.7 ± 1.7. Surgical information: 61% osteotomy, 52% decompression, 11.0 ± 4.1 levels fused. There were 98 not frail (NF), 65 frail (F), and 30 severely frail (SF) patients. Relationships were found between increasing invasiveness and experiencing a major complication or reoperation for the entire cohort and by frailty group (all P < 0.05). Defining a favorable outcome as no major complications or reoperation and meeting MCID in any health-related quality of life at 3Y established an invasiveness cutoff of 63.9. Patients below this threshold were 1.8[1.38-2.35] (P < 0.001) times more likely to achieve favorable outcome. For NF patients, the cutoff was 79.3 (2.11[1.39-3.20] (P < 0.001), 111 for F (2.62 [1.70-4.06] (P < 0.001), and 53.3 for SF (2.35[0.78-7.13] (P = 0.13).

CONCLUSION

Increasing invasiveness is associated with increased odds of major complications and reoperations. Risk-benefit cutoffs for successful outcomes were 79.3 for NF, 111 for F, and 53.3 for SF patients. Above these, increasing invasiveness has increasing risk of major complications or reoperations and not meeting MCID at 3Y.Level of Evidence: 3.

Identification of Risk Factors for Readmission in Patients Undergoing Anterior Cervical Discectomy Fusion: A Predictive Risk Scale

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The objective of this study was to analyze readmission rates among patients undergoing anterior cervical discectomy and fusion (ACDF), determine which factors were associated with higher readmission rates, and develop a scale for utilization during surgical planning.

SUMMARY OF BACKGROUND DATA

ACDF is the most common surgical treatment for many cervical disk pathologies. With the Centers for Medicare and Medicaid Services selecting readmissions as a measure of health care quality, there has been an increased focus on reducing readmissions.

MATERIALS AND METHODS

There were 114,174 recorded ACDF surgeries in the derivation cohort, the State Inpatient Database (SID) of New York and California between 2006 and 2014. There were 115,829 ACDF surgeries recorded in the validation cohort, the SID from Florida and Washington over the same time period. After identification of risk factors using univariate and multivariate analysis of the derivation cohort, a predictive scale was generated and tested utilizing the validation cohort.

RESULTS

Overall, readmission rates within 30 days of discharge were 5.87% and 5.52% in the derivation and validation cohorts, respectively. On multivariate analysis of the derivation cohort, age older than 80 years [odds ratio (OR), 1.67] male sex (OR, 1.16), Medicaid insurance (OR, 1.90), Medicare insurance (OR, 1.64), revision ACDF (OR, 1.43), anemia (OR, 1.45), chronic lung disease (OR, 1.23), coagulopathy (OR, 1.42), congestive heart failure (OR, 1.31), diabetes (OR, 1.23), fluid and electrolyte disorder (OR, 1.56), liver disease (OR, 1.37), renal failure (OR, 1.59), and myelopathy (OR, 1.19) were found to be statistically significant predictors for readmission. These factors were incorporated into a numeric scale that, that when tested on the validation cohort, could explain 97.1% of the variability in readmission rate.

CONCLUSIONS

Overall, 30-day readmission following ACDF surgery was 5%-6%. A novel risk scale based on factors associated with increased readmission rates may be helpful in identifying patients who require additional optimization to reduce perioperative morbidity.

LEVEL OF EVIDENCE

Level III-prognostic.

Medical optimization of modifiable risk factors before thoracolumbar three-column osteotomies: an analysis of 195 patients

PURPOSE

To determine the rate of preoperative modifiable laboratory abnormalities (both major and minor) and the association with early postoperative medical and surgical complications.

METHODS

All patients undergoing thoracolumbar three-column osteotomy between 2013 and 2016 with preoperative laboratory data were identified. Potential preoperative modifiable laboratory abnormalities (major and minor) were assessed including hyponatremia (sodium < 130 and < 135 mEq/L), anemia (hematocrit < 25% and < 30%), renal insufficiency (creatinine ≥ 1.8 and ≥ 1.2 mg/dL), coagulopathy (INR ≥ 1.8 and ≥ 1.2), and hypoalbuminemia (albumin < 2.5 and < 3.5 g/dL). Multivariate logistic regression was used to determine associations with 30-day complications after controlling for possible confounding factors.

RESULTS

A total of 195 patients were identified. The rates of major and minor preoperative laboratory abnormalities were 7.7% and 31.3%, respectively. The rates of serious medical, minor medical, and surgical complications over 30-days were 6.7%, 21.5%, and 10.3%, respectively. In multivariate analysis the presence of major preoperative laboratory abnormalities had a significant association with serious medical complications (odds ratio [OR] 77.8, P < 0.001), and minor medical complications (OR 13.3, P < 0.001), but not surgical complications (P = 0.243). The presence of minor preoperative laboratory abnormalities had a significant association with serious medical complications (OR 10.4, P = 0.041) and minor medical complications (OR 2.4, P = 0.045), but not surgical complications (P = 0.490).

CONCLUSIONS

While major laboratory abnormalities had a strong association with complications, even minor modifiable laboratory abnormalities had a significant association with both serious and minor medical complications.

The effect of anterior lumbar interbody fusion staging order on perioperative complications in circumferential lumbar fusions performed within the same hospital admission

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) is a powerful technique that provides wide access to the disc space and allows for large lordotic grafts. When used with posterior spinal fusion (PSF), the procedures are often staged within the same hospital admission. There are limited data on the perioperative risk profile of ALIF-first versus PSF-first circumferential fusions performed within the same hospital admission. In an effort to understand whether these procedures are associated with different perioperative complication profiles, the authors performed a retrospective review of their institutional experience in adult patients who had undergone circumferential lumbar fusions.

METHODS

The electronic medicals records of patients who had undergone ALIF and PSF on separate days within the same hospital admission at a single academic center were retrospectively analyzed. Patients carrying a diagnosis of tumor, infection, or traumatic fracture were excluded. Demographics, surgical characteristics, and perioperative complications were collected and assessed.

RESULTS

A total of 373 patients, 217 of them women (58.2%), met the inclusion criteria. The mean age of the study cohort was 60 years. Surgical indications were as follows: degenerative disease or spondylolisthesis, 171 (45.8%); adult deformity, 168 (45.0%); and pseudarthrosis, 34 (9.1%). The majority of patients underwent ALIF first (321 [86.1%]) with a mean time of 2.5 days between stages. The mean number of levels fused was 2.1 for ALIF and 6.8 for PSF. In a comparison of ALIF-first to PSF-first cases, there were no major differences in demographics or surgical characteristics. Rates of intraoperative complications including venous injury were not significantly different between the two groups. The rates of postoperative ileus (11.8% vs 5.8%, p = 0.194) and ALIF-related wound complications (9.0% vs 3.8%, p = 0.283) were slightly higher in the ALIF-first group, although the differences did not reach statistical significance. Rates of other perioperative complications were no different.

CONCLUSIONS

In patients undergoing staged circumferential fusion with ALIF and PSF, there was no statistically significant difference in the rate of perioperative complications when comparing ALIF-first to PSF-first surgeries.

Evaluation of Predictive Models for Complications following Spinal Surgery

BACKGROUND

 Complications rates vary across spinal surgery procedures and are difficult to predict due to heterogeneity in patient characteristics, surgical methods, and hospital volume. Incorporation of predictive models for complications may guide surgeon decision making and improve outcomes.

METHODS

 We evaluate current independently validated predictive models for complications in spinal surgery with respect to study design and model generation, accuracy, reliability, and utility. We conducted our search using Preferred Reporting Items for Systematic Review and Meta-analysis guidelines and the Participants, Intervention, Comparison, Outcomes, Study Design model through the PubMed and Ovid Medline databases.

RESULTS

 A total of 18 articles met inclusion criteria including 30 validated predictive models of complications after adult spinal surgery. National registry databases were used in 12 studies. Validation cohorts were used in seven studies for verification; three studies used other methods including random sample bootstrapping techniques or cross-validation. Reported area under the curve (AUC) values ranged from 0.37 to 1.0. Studies described treatment for deformity, degenerative conditions, inclusive spinal surgery (neoplasm, trauma, infection, deformity, degenerative), and miscellaneous (disk herniation, spinal epidural abscess). The most commonly cited risk factors for complications included in predictive models included age, body mass index, diabetes, sex, and smoking. Those models in the deformity subset that included radiographic and anatomical grading features reported higher AUC values than those that included patient demographics or medical comorbidities alone.

CONCLUSIONS

 We identified a cohort of 30 validated predictive models of complications following spinal surgery for degenerative conditions, deformity, infection, and trauma. Accurate evidence-based predictive models may enhance shared decision making, improve rehabilitation, reduce adverse events, and inform best practices.

State-of-the-Art Reviews: Safety in Complex Spine Surgery

The surgical correction of spinal deformities carries a high risk of perioperative morbidity. As the incidence of debilitating spinal deformities continues to increase, so too does our obligation to search for ways to enhance safety in our delivery of surgical care. Standardized work processes and other lean manufacturing methodologies have the potential to improve efficiency, safety, and hence value in our delivery of surgical care to patients with complex spine pathologies by reducing variability in our work processes. These principles can be applied to patient care from the initial preoperative assessment to long-term postoperative follow-up in the creation of comprehensive protocols that guide the management of these complex patients. Early evidence suggests that short-term outcomes can be improved by implementing packages of systems reform aimed at reducing variability in our work processes; however, contradicting evidence exists on the utility of several specific components of these systems-reform packages.

Adult Spinal Deformity Over 70 Years of Age: A 2-Year Follow-Up Study

Background

Treatment of adult spinal deformity (ASD) in elderly patients remains controversial. The aim of this study was to identify the factors leading to the surgical treatment by comparing the baseline characteristics of operative versus nonoperative patients, to evaluate the safety and efficacy of surgery, and to compare operative and nonoperative management of elderly ASD patients at the end of the 2-year follow-up period.

Methods

Retrospective review of a multicenter, prospective ASD database was performed. Patients over 70 years of age with ASD who were scheduled to undergo surgical treatment and who were treated and/or followed without surgical intervention participated in the study. Demographic, clinical, surgical, and radiological characteristics and health-related quality-of-life (HRQOL) (Core Outcome Measures Index [COMI], Oswestry Disability Index [ODI], Short-Form-36 Mental Component Summary [SF-36 MCS], Short-Form-36 Physical Component Summary [SF36-PCS], and Scoliosis Research Society-22 [SRS-22]) parameters of such group of patients were evaluated pre- and posttreatment.

Results

A total 90 patients (females: 71, males: 29; operative: 61, nonoperative: 29) made up the study group. The comparison between the operative and the nonoperative groups at baseline showed statistical significance for all the HRQOL parameters and the major coronal Cobb angle (P < .05). The calculated optimal cutoff values to diverge operative and nonoperative groups for COMI, ODI, SF-36 PCS, and SRS-22 were 5.7, 37.0, 37.5, and 3.2, respectively (P < .05). All operative patients were treated with posterior surgery. Overall, 135 complications (71 major, 64 minor) and 1 death were observed. Surgically treated patients were found to be improved both clinically and in HRQOL parameters 2 years after surgery for all HRQOL parameters except SF-36 MCS, even in the presence of complications (P < .05), while nonoperative patients have not changed or deteriorated at the end of 2 years.

Conclusions

Despite a relatively high incidence of complications, the likelihood of achieving a clinically significant and relevant HRQOL improvement was superior for patients who were treated surgically in the present population.

Spinal Fusion in Parkinson's Disease Patients: A Propensity Score-Matched Analysis With Minimum 2-Year Surveillance

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To compare outcomes and complication rates between patients with and without Parkinson's disease (PD) patients undergoing surgery for adult spinal deformity (ASD).

SUMMARY OF BACKGROUND DATA

There is limited literature evaluating the impact of PD on long-term outcomes after thoracolumbar fusion surgery for ASD.

METHODS

Patients admitted from 2009 to 2011 with diagnoses of ASD who underwent any thoracolumbar fusion procedure with a minimum 2-year follow-up surveillance were retrospectively reviewed using New York State's Statewide Planning and Research Cooperative System. A 1:1 propensity score-match by age, Deyo score, and number of fused vertebral levels was conducted before comparing surgical outcomes of patients with ASD with and without PD. Univariate analysis compared demographics, complications, and subsequent revision. Multivariate binary stepwise logistic regression models identified independent predictors of these outcomes (covariates: age, sex, Deyo Index score, and PD diagnosis).

RESULTS

A total of 576 propensity score-matched patients were identified (PD: n = 288; no-PD: n = 288), with a mean age of 69.7 years (PD) and 70.2 years (no-PD). Each cohort had comparable distributions of age, sex, race, insurance provider, Deyo score, and number of levels fused (all P > 0.05). Patients with PD incurred higher total charges across ASD surgery-related visits ($187,807 vs. $126,610, P < 0.001), yet rates of medical complications (35.8% PD vs. 34.0% no-PD, P = 0.662) and revision surgery (12.2% vs. 10.8%, P > 0.05) were comparable. Postoperative mortality rates were comparable between PD and no-PD cohorts (2.8% vs. 1.4%, P = 0.243). Logistic regression identified nine-level or higher spinal fusion as a significant predictor for an increase in total complications (odds ratio = 5.64); PD was not associated with increased odds of any adverse outcomes.

CONCLUSION

Aside from higher hospital charges incurred, patients with PD experienced comparable overall complication and revision rates to a propensity score-matched patient cohort without PD from the general population undergoing thoracolumbar fusion surgery. These results can support management of concerns and postoperative expectations in this patient cohort.

LEVEL OF EVIDENCE

3.

Adult spinal deformity

Adult spinal deformity affects the thoracic or thoracolumbar spine throughout the ageing process. Although adolescent spinal deformities taken into adulthood are not uncommon, the most usual causes of spinal deformity in adults are iatrogenic flatback and degenerative scoliosis. Given its prevalence in the expanding portion of the global population aged older than 65 years, the disorder is of growing interest in health care. Physical examination, with a focus on gait and posture, along with radiographical assessment are primarily used and integrated with risk stratification indices to establish optimal treatment planning. Although non-operative treatment is regarded as the first-line response, surgical outcomes are considerably favourable. Global disparities exist in both the assessment and treatment of adults with spinal deformity across countries of varying incomes, which represents an area requiring further investigation. This Seminar presents evidence and knowledge that represent the evolution of data related to spinal deformity in adults over the past several decades.

Artificial Intelligence Based Hierarchical Clustering of Patient Types and Intervention Categories in Adult Spinal Deformity Surgery: Towards a New Classification Scheme that Predicts Quality and Value

STUDY DESIGN

Retrospective review of prospectively-collected, multicenter adult spinal deformity (ASD) databases.

OBJECTIVE

To apply artificial intelligence (AI)-based hierarchical clustering as a step toward a classification scheme that optimizes overall quality, value, and safety for ASD surgery.

SUMMARY OF BACKGROUND DATA

Prior ASD classifications have focused on radiographic parameters associated with patient reported outcomes. Recent work suggests there are many other impactful preoperative data points. However, the ability to segregate patient patterns manually based on hundreds of data points is beyond practical application for surgeons. Unsupervised machine-based clustering of patient types alongside surgical options may simplify analysis of ASD patient types, procedures, and outcomes.

METHODS

Two prospective cohorts were queried for surgical ASD patients with baseline, 1-year, and 2-year SRS-22/Oswestry Disability Index/SF-36v2 data. Two dendrograms were fitted, one with surgical features and one with patient characteristics. Both were built with Ward distances and optimized with the gap method. For each possible n patient cluster by m surgery, normalized 2-year improvement and major complication rates were computed.

RESULTS

Five hundred-seventy patients were included. Three optimal patient types were identified: young with coronal plane deformity (YC, n = 195), older with prior spine surgeries (ORev, n = 157), and older without prior spine surgeries (OPrim, n = 218). Osteotomy type, instrumentation and interbody fusion were combined to define four surgical clusters. The intersection of patient-based and surgery-based clusters yielded 12 subgroups, with major complication rates ranging from 0% to 51.8% and 2-year normalized improvement ranging from -0.1% for SF36v2 MCS in cluster [1,3] to 100.2% for SRS self-image score in cluster [2,1].

CONCLUSION

Unsupervised hierarchical clustering can identify data patterns that may augment preoperative decision-making through construction of a 2-year risk-benefit grid. In addition to creating a novel AI-based ASD classification, pattern identification may facilitate treatment optimization by educating surgeons on which treatment patterns yield optimal improvement with lowest risk.

LEVEL OF EVIDENCE

4.

Development and validation of risk stratification models for adult spinal deformity surgery

OBJECTIVE

Adult spinal deformity (ASD) surgery has a high rate of major complications (MCs). Public information about adverse outcomes is currently limited to registry average estimates. The object of this study was to assess the incidence of adverse events after ASD surgery, and to develop and validate a prognostic tool for the time-to-event risk of MC, hospital readmission (RA), and unplanned reoperation (RO).

METHODS

Two models per outcome, created with a random survival forest algorithm, were trained in an 80% random split and tested in the remaining 20%. Two independent prospective multicenter ASD databases, originating from the European continent and the United States, were queried, merged, and analyzed. ASD patients surgically treated by 57 surgeons at 23 sites in 5 countries in the period from 2008 to 2016 were included in the analysis.

RESULTS

The final sample consisted of 1612 ASD patients: mean (standard deviation) age 56.7 (17.4) years, 76.6% women, 10.4 (4.3) fused vertebral levels, 55.1% of patients with pelvic fixation, 2047.9 observation-years. Kaplan-Meier estimates showed that 12.1% of patients had at least one MC at 10 days after surgery; 21.5%, at 90 days; and 36%, at 2 years. Discrimination, measured as the concordance statistic, was up to 71.7% (95% CI 68%-75%) in the development sample for the postoperative complications model. Surgical invasiveness, age, magnitude of deformity, and frailty were the strongest predictors of MCs. Individual cumulative risk estimates at 2 years ranged from 3.9% to 74.1% for MCs, from 3.17% to 44.2% for RAs, and from 2.67% to 51.9% for ROs.

CONCLUSIONS

The creation of accurate prognostic models for the occurrence and timing of MCs, RAs, and ROs following ASD surgery is possible. The presented variability in patient risk profiles alongside the discrimination and calibration of the models highlights the potential benefits of obtaining time-to-event risk estimates for patients and clinicians.

Surgical risk stratification based on preoperative risk factors in adult spinal deformity

BACKGROUND CONTEXT

Corrective surgery for adult spinal deformity (ASD) improves health-related quality of life but has high complication rates. Predicting a patient's risk of perioperative and late postoperative complications is difficult, although several potential risk factors have been reported.

PURPOSE

To establish an accurate, ASD-specific model for predicting the risk of postoperative complications, based on baseline demographic, radiographic, and surgical invasiveness data in a retrospective case series.

STUDY DESIGN/SETTING

Multicentered retrospective review and the surgical risk stratification.

PATIENT SAMPLE

One hundred fifty-one surgically treated ASD at our hospital for risk analysis and model building and 89 surgically treated ASD at 2 other our hospitals for model validation.

OUTCOME MEASURES

HRQoL measures and surgical complications.

METHODS

We analyzed demographic and medical data, including complications, for 151 adults with ASD who underwent surgery at our hospital and were followed for at least 2years. Each surgical risk factor identified by univariate analyses was assigned a value based on its odds ratio, and the values of all risk factors were summed to obtain a surgical risk score (range 0-20). We stratified risk scores into grades (A-D) and analyzed their correlations with complications. We validated the model using data from 89 patients who underwent ASD surgery at two other hospitals.

RESULTS

Complications developed in 48% of the patients in the model-building cohort. Univariate analyses identified 10 demographic, physical, and surgical risk indicators, with odds ratios from 5.4 to 1.4, for complications. Our risk-grading system showed good calibration and discrimination in the validation cohort. The complication rate increased with and correlated well with the risk grade using receiver operating characteristic curves.

CONCLUSIONS

This simple, ASD-specific model uses readily accessible indicators to predict a patient's risk of perioperative and postoperative complications and can help surgeons adjust treatment strategies for best outcomes in high-risk patients.