Reliable Prediction of Discharge Disposition Following Cervical Spine Surgery With Ensemble Machine Learning and Validation on a National Cohort

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The purpose of this study is to develop a machine learning algorithm to predict nonhome discharge after cervical spine surgery that is validated and usable on a national scale to ensure generalizability and elucidate candidate drivers for prediction.

SUMMARY OF BACKGROUND DATA

Excessive length of hospital stay can be attributed to delays in postoperative referrals to intermediate care rehabilitation centers or skilled nursing facilities. Accurate preoperative prediction of patients who may require access to these resources can facilitate a more efficient referral and discharge process, thereby reducing hospital and patient costs in addition to minimizing the risk of hospital-acquired complications.

METHODS

Electronic medical records were retrospectively reviewed from a single-center data warehouse (SCDW) to identify patients undergoing cervical spine surgeries between 2008 and 2019 for machine learning algorithm development and internal validation. The National Inpatient Sample (NIS) database was queried to identify cervical spine fusion surgeries between 2009 and 2017 for external validation of algorithm performance. Gradient-boosted trees were constructed to predict nonhome discharge across patient cohorts. The area under the receiver operating characteristic curve (AUROC) was used to measure model performance. SHAP values were used to identify nonlinear risk factors for nonhome discharge and to interpret algorithm predictions.

RESULTS

A total of 3523 cases of cervical spine fusion surgeries were included from the SCDW data set, and 311,582 cases were isolated from NIS. The model demonstrated robust prediction of nonhome discharge across all cohorts, achieving an area under the receiver operating characteristic curve of 0.87 (SD=0.01) on both the SCDW and nationwide NIS test sets. Anterior approach only, age, elective admission status, Medicare insurance status, and total Elixhauser Comorbidity Index score were the most important predictors of discharge destination.

CONCLUSIONS

Machine learning algorithms reliably predict nonhome discharge across single-center and national cohorts and identify preoperative features of importance following cervical spine fusion surgery.

20-year Inflation-Adjusted Medicare Reimbursements (Years: 2000-2020) For Common Lumbar and Cervical Degenerative Disc Disease Procedures

OBJECTIVE

Reimbursement trends for common procedures have persistently declined over the past 2 decades. Spinal instrumentational and fusion procedures are increasingly utilized and have increased in clinical complexity, yet longitudinal inflation-adjusted data for Medicare reimbursements of these procedures have not been evaluated.

METHODS

The Centers for Medicare and Medicaid Services (CMS) Physician Fee Schedule Look-Up Tool was used to extract Medicare reimbursements for the 5 most common spinal procedures and associated instrumentations from 2000-2020. Current Procedural Terminology (CPT) codes include 22551, 22600, 22633, 63030, and 63047 as well as instrumentation CPT codes 22840 and 22842-6. The nominal values were adjusted for inflation according to the latest consumer price index (U.S. Bureau of Labor Statistics; reported as 2020 USD) and used to calculate average annual percent changes and compound annual growth rates (CAGRs) in reimbursements.

RESULTS

After inflation adjustment, the physician fee reimbursement decreased by 11.05% ± 8.46% (mean ± s.d., from $2,009.89 in 2011 to $1,787.85 in 2020) for anterior cervical discectomy and fusion (ACDF), 28.38% ± 8.42% (from $1,889.38 in 2000 to $1,353.14 in 2020) for posterior cervical fusion, 7.85% ± 8.20% (from $2,111.20 in 2012 to $1,945.49 in 2020) for transforaminal lumbar interbody fusion (TLIF), 28.17% ± 13.88% (from $1,421.78 in 2000 to $1,021.22 in 2020) for lower back disc surgery, and 31.88% ± 8.22% (from $1,700.38 in 2000 to $1,158.25 in 2020) for lumbar laminectomy. Instrumentation reimbursements showed an average decrease of 33.43% ± 8.4% over this period. Average CAGR was -1.7% ± .41% for procedures and -2.02% ± .14% for instrumentation.

CONCLUSION

Our analysis reveals a persistent decline in reimbursement rates of the most common spine procedures and instrumentation since the year 2000. If unaddressed, this trend can serve as a substantial disincentive for physicians to perform these procedures and can significantly limit access to spinal care at the population level.

Comparative Analysis of Early Outcomes and Complications of PSO Among Neurosurgeons and Orthopedic Surgeons

STUDY DESIGN

Retrospective comparative cohort study using the National Surgical Quality Improvement Program.

OBJECTIVE

The aim of this study was to evaluate trends in the annual number of PSOs performed, describe the patient populations associated with each cohort, and compare outcomes between specialties.Summary of Background Data:Pedicle subtraction osteotomies (PSO) are complex and advanced spine deformity surgical procedures performed by neurosurgeons and orthopedic surgeons. Though both sets of surgeons can be equally qualified and credentialed to perform a PSO, it is possible that differences in training and exposure could translate into differences in patient management and outcomes.

METHODS

Patients that underwent lumbar PSO from 2005 to 2014 in the American College of Surgeons-National Surgical Quality Improvement Program registry were identified. Relevant demographic, preoperative comorbidity, and postoperative 30-day complications were queried and analyzed. The data was divided into 2 cohorts consisting of those patients who were treated by neurosurgeons versus orthopedic surgeons. Additional data from the Scoliosis Research Society Morbidity and Mortality database was queried and analyzed for comparison.

RESULTS

Demographic and comorbidity factors were similar between the neurosurgery and orthopedic surgery cohorts, except there were higher rates of hypertension among orthopedic surgeon-performed PSOs (65.66% vs. 48.67%, P =0.004). Except for 2012, in every year queried, orthopedic surgeons reported more PSOs than neurosurgeons. In patients who underwent lumbar fusion surgery, there was a higher rate of PSOs if the surgery was performed by an orthopedic surgeon (OR 1.7824, 95% CI: 1.4017-2.2665). The incidence of deep vein thrombosis after PSOs was higher for neurosurgery compared with orthopedic surgery (8.85% vs. 1.20%, P =0.004). However, besides deep vein thrombosis, there were no salient differences in surgical complication rates between neurosurgeon-performed PSOs and orthopedic surgeon-performed PSOs.

CONCLUSIONS

The number of PSO procedures performed by neurosurgeons and orthopedic surgeons has increased annually. Differences in outcomes between neurosurgeons and orthopedic surgeons suggest an opportunity for wider assessment and alignment of adult spinal deformity surgery exposure and training across specialties.

Robust prediction of nonhome discharge following elective anterior cervical discectomy and fusion using explainable machine learning

PURPOSE

Predict nonhome discharge (NHD) following elective anterior cervical discectomy and fusion (ACDF) using an explainable machine learning model.

METHODS

2227 patients undergoing elective ACDF from 2008 to 2019 were identified from a single institutional database. A machine learning model was trained on preoperative variables, including demographics, comorbidity indices, and levels fused. The validation technique was repeated stratified K-Fold cross validation with the area under the receiver operating curve (AUROC) statistic as the performance metric. Shapley Additive Explanation (SHAP) values were calculated to provide further explainability regarding the model's decision making.

RESULTS

The preoperative model performed with an AUROC of 0.83 ± 0.05. SHAP scores revealed the most pertinent risk factors to be age, medicare insurance, and American Society of Anesthesiology (ASA) score. Interaction analysis demonstrated that female patients over 65 with greater fusion levels were more likely to undergo NHD. Likewise, ASA demonstrated positive interaction effects with female sex, levels fused and BMI.

CONCLUSION

We validated an explainable machine learning model for the prediction of NHD using common preoperative variables. Adding transparency is a key step towards clinical application because it demonstrates that our model's "thinking" aligns with clinical reasoning. Interactive analysis demonstrated that those of age over 65, female sex, higher ASA score, and greater fusion levels were more predisposed to NHD. Age and ASA score were similar in their predictive ability. Machine learning may be used to predict NHD, and can assist surgeons with patient counseling or early discharge planning.

MIS-TLIF Procedure is Improving With Experience: Systematic Review of the Learning Curve Over the Last Decade

STUDY DESIGN

This was a systematic review.

OBJECTIVE

This review evaluates the minimally invasive transforaminal lumbar interbody fusions (MIS-TLIF) learning curve in the literature and compares outcomes during and after completing the curve.

SUMMARY OF BACKGROUND DATA

MIS-TLIF are performed for various spine conditions. Proponents cite improved clinical outcomes while critics highlight the steep learning curve to attain proficiency.

METHODS

Literature searches on Medline and Embase utilized relevant subject headings and keywords. Manuscripts reporting learning curve statistics were included. Monotonic trends of operative duration were assessed with Mann-Kendall nonparametric testing.

RESULTS

Nine studies met inclusion criteria. Number of patients ranged from 26 to 150 (average 83.2, median of 86). Commonly reported metrics included number of procedures to complete the curve, operative duration, blood loss, ambulation time, length of stay, complication rate, follow-up visual analogue scale (VAS) for back and leg pain, and fusion rate. Various methods were employed to determine number of cases to complete the curve, all involving operative duration. Number of cases ranged from 14 to 44. A significant negative trend for operative duration of cases during the learning curve (τ=-0.733, P =0.039) was found over the years that studies were published. Initial complication rates varied from 6.8% to 23.8%. Initial VAS-back and VAS-leg ranged from 0.8 to 2.9 and 0.5 to 2.3, respectively. While definitions of "good" fusion varied, fusion rates meeting Bridwell grade I or II during the learning curve ranged from 84.0% to 95.2%.

CONCLUSIONS

Surgeons in their learning curve have become faster at the MIS-TLIF procedure. Clinical outcomes including postoperative pain and fusion rates showed satisfactory results, but surgeons learning the procedure should take measures to minimize complications in early cases, such as utilizing novel navigation technology or supervision from more experienced surgeons. Learning curve research methodology could benefit from standardization.

The Impact of Obstructive Sleep Apnea on Clinical, Perioperative, and Cost Outcomes in Patients Who Underwent Posterior Cervical Decompression and Fusion: A Single-Center Retrospective Analysis From 2008 to 2016

BACKGROUND

Obstructive sleep apnea (OSA) is a pervasive problem that can result in diminished neurocognitive performance, increased risk of all-cause mortality, and significant cardiovascular disease. While previous studies have examined risk factors that influence outcomes following cervical fusion procedures, to our knowledge, no study has examined the cost or outcome profiles for posterior cervical decompression and fusion (PCDF) procedures in patients with OSA.

METHODS

All cases at a single institution between 2008 and 2016 involving a PCDF were included. The primary outcome was prolonged extubation, defined as an extubation that took place outside of the operating room. Secondary outcomes included admission to the intensive care unit (ICU), complications, extended hospitalization, nonhome discharge, readmission within 30 and 90 days, emergency room visit within 30 and 90 days, and higher total costs.

RESULTS

We reviewed 1191 PCDF cases, of which 93 patients (7.81%) had a history of OSA. At the univariate level, patients with OSA had higher rates of ICU admissions (33.3% vs 16.8%, P < 0.0001), total complications (29.0% vs 19.0%, P = 0.0202), and respiratory complications (12.9% vs 6.6%, P = 0.0217). Multivariate regression analyses revealed no difference in the odds of a prolonged extubation (P = 0.4773) and showed that history of OSA was not predictive of higher costs. However, a significant difference was observed in the odds of having an ICU admission (P = 0.0046).

CONCLUSION

While patients with sleep apnea may be more likely to be admitted to the ICU postoperatively, OSA status a lone is not a risk factor for poor primary and secondary clinical outcomes following posterior cervical fusion procedures.

CLINICAL RELEVANCE

Various deformities of the cervical spine can exert extraluminal forces that partially collapse or obstruct the airway, thereby predisposing patients to OSA; however, no study has examined the cost or outcome profiles for PCDF procedures in patients with OSA. Therefore, this investigation highlights the ways in which OSA influences the risks, outcomes, and costs following PCDF using medical data from an institutional registry.

LEVEL OF EVIDENCE: 3

Neurosurgical Performance in the First 2 Years of Merit-Based Incentive Payment System: A Descriptive Analysis and Predictors of Receiving Bonus Payments

BACKGROUND

The merit-based incentive payment system (MIPS) program was implemented to tie Medicare reimbursements to value-based care measures. Neurosurgical performance in MIPS has not yet been described.

OBJECTIVE

To characterize neurosurgical performance in the first 2 years of MIPS.

METHODS

Publicly available data regarding MIPS performance for neurosurgeons in 2017 and 2018 were queried. Descriptive statistics about physician characteristics, MIPS performance, and ensuing payment adjustments were performed, and predictors of bonus payments were identified.

RESULTS

There were 2811 physicians included in 2017 and 3147 in 2018. Median total MIPS scores (99.1 vs 90.4, P < .001) and quality scores (97.9 vs 88.5, P < .001) were higher in 2018 than in 2017. More neurosurgeons (2758, 87.6%) received bonus payments in 2018 than in 2017 (2013, 71.6%). Of the 2232 neurosurgeons with scores in both years, 1347 (60.4%) improved their score. Reporting through an alternative payment model (odds ratio [OR]: 32.3, 95% CI: 16.0-65.4; P < .001) and any practice size larger than 10 (ORs ranging from 2.37 to 10.2, all P < .001) were associated with receiving bonus payments. Increasing years in practice (OR: 0.99; 95% CI: 0.982-0.998, P = .011) and having 25% to 49% (OR: 0.72; 95% CI: 0.53-0.97; P = .029) or ≥50% (OR: 0.48; 95% CI: 0.28-0.82; P = .007) of a physician's patients eligible for Medicaid were associated with lower rates of bonus payments.

CONCLUSION

Neurosurgeons performed well in MIPS in 2017 and 2018, although the program may be biased against surgeons who practice in small groups or take care of socially disadvantaged patients.

The Impact of Diabetes on Outcomes and Health Care Costs Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Anterior cervical discectomy and fusion (ACDF) is commonly used to treat an array of cervical spine pathology and is associated with good outcomes and low complication rates. Diabetes mellitus (DM) is a common comorbidity for patients undergoing ACDF, but the literature is equivocal about the impact it has on outcomes. Because DM is a highly prevalent comorbidity, it is crucial to determine if it is an associated risk factor for outcomes after ACDF procedures.

METHODS

Patients at a single institution from 2008 to 2016 undergoing ACDF were compared on the basis of having a prior diagnosis of DM versus no DM. The 2 cohorts were compared utilizing univariate tests and multivariate logistic and linear regressions.

RESULTS

Data for 2470 patients was analyzed. Diabetic patients had significantly higher Elixhauser scores (P < .0001). Univariate testing showed diabetic patients were more likely to suffer from sepsis (0.82% vs 0.10%, P = .03) and bleeding complications (3.0% vs 1.5%, P = .04). In multivariate analyses, diabetic patients had higher rates of non-home discharge (odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.07-1.75, P = .013) and prolonged length of stay (OR = 1.95, 95% CI = 1.25-3.05, P = .003), but similar complication (OR = 1.46, 95% CI = 0.85-2.52, P = .17), reoperation (OR = 0.77, 95% CI = 0.33-1.81, P = .55), and 90-day readmission (OR = 1.53, 95% CI = 0.97-2.43) rates compared to nondiabetic patients. Direct cost was also shown to be similar between the cohorts after adjusting for patient, surgical, and hospital-related factors (estimate = -$30.25, 95% CI = -$515.69 to $455.18, P = .90).

CONCLUSIONS

Diabetic patients undergoing ACDF had similar complication, reoperation, and readmission rates, as well as similar cost of care compared to nondiabetic patients.

Diabetes Is Predictive of Postoperative Outcomes and Readmission Following Posterior Lumbar Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The present study analyzes complication rates and episode-based costs for patients with and without diabetes mellitus (DM) following posterior lumbar fusion (PLF).

METHODS

PLF cases at a single institution from 2008 to 2016 were queried (n = 3226), and demographic and perioperative data were analyzed. Patients with and without the diagnosis of DM were compared using chi-square, Student's t test, and multivariable regression modeling.

RESULTS

Patients with diabetes were older (63.10 vs 56.48 years, P < .001) and possessed a greater number of preoperative comorbidities (47.84% of patients had Elixhauser Comorbidity Index >0 vs 42.24%, P < .001) than did patients without diabetes. When controlling for preexisting differences, diabetes remained a significant risk factor for prolonged length of stay (OR = 1.59, 95% CI 1.26-2.01, P < .001), intensive care unit stay (OR = 1.52, 95% CI 1.07-2.17, P = .021), nonhome discharge (OR = 1.86, 95% CI 1.46-2.37, P < .001), 30-day readmission (OR = 2.15, 95% CI 1.28-3.60, P = .004), 90-day readmission (OR = 1.65, 95% CI 1.05-2.59, P = .031), 30-day emergency room visit (OR = 2.15, 95% CI 1.27-3.63, P = .004), and 90-day emergency room visit (OR = 2.27, 95% CI 1.41-3.65, P < .001). Cost modeling controlling for overall comorbidity burden demonstrated that diabetes was associated with a $1709 increase in PLF costs (CI $344-$3074, P = .014).

CONCLUSIONS

The present findings indicate a correlation between diabetes and a multitude of postoperative adverse outcomes and increased costs, thus illustrating the substantial medical and financial burdens of diabetes for PLF patients. Future studies should explore preventive measures that may mitigate these downstream effects.

Intraoperative Navigation in Spine Surgery: Effects On Complications and Reoperations

INTRODUCTION

Intraoperative navigation during spine surgery improves pedicle screw placement accuracy. However, limited studies have correlated navigation with clinical factors including operative time and safety. This study compares complications and reoperations between surgeries with and without navigation.

METHODS

Posterior cervical and lumbar fusions and deformity surgeries from 2011-2018 were queried from the NSQIP database and divided by navigation use. Patients aged >89, deformity patients aged <25, and patients undergoing surgery for tumors, fractures, infections, or non-elective indications were excluded. Demographics and perioperative factors were compared with univariate analysis. Outcomes were compared with multivariable logistic regression adjusting for age, sex, BMI, ASA class, surgical region, and multiple levels. Outcomes were also compared stratifying by revision status.

RESULTS

Navigated surgery patients had higher ASA status (p<0.0001), more multiple-level surgeries (p<0.0001), and longer operations (p<0.0001). Adjusted analysis revealed navigated lumbar surgeries had lower odds of complications (OR=0.82, 95%CI=0.77-0.90, p<0.0001), blood transfusion (OR=0.79, 95%CI=0.72-0.87, p<0.0001), and wound debridement/drainage (OR=0.66, 95%CI=0.44-0.97, p=0.04) compared to non-navigated procedures. Navigated cervical fusions had increased odds of transfusion (OR=1.53, 95%CI=1.06-2.23, p=0.02). Navigated primary fusions had decreased odds of complications (OR=0.91, 95%CI=0.85-0.98, p=0.01); no difference was found in revisions (OR=0.89, 95%CI=0.69-1.14, p=0.34).

CONCLUSIONS

Navigated surgery patients experienced longer operations due to a combination of time using navigation, more multi-level procedures and larger comorbidity burden, without differences in infections. There were fewer complications and wound washouts in navigated lumbar surgeries due to a higher percentage of minimally invasive cases. Co-utilization of navigation and minimally invasive surgery may benefit properly indicated patients.

Clinical Trials in Spinal Tumors: A Two-Decade Review

OBJECTIVE

Clinical trials are essential for assessing advancements in spine tumor therapeutics. The purpose of this study is to characterize trends in clinical trials for primary and metastatic tumor treatments over the past two decades.

METHODS

ClinicalTrials.gov was queried using the search term "spine" for all interventional studies spanning 1999 to 2020 with categories of "Cancer", "Neoplasm", "Tumor", or "Metastasis". Tumor type, phase data, enrollment numbers and home institution country were recorded. The sponsor was categorized as academic institution, industry, government or other and intervention type as procedure, drug, device, radiation or other. Frequency of each category and cumulative frequency over twenty years were calculated.

RESULTS

106 registered trials for spine tumors were listed. All except two that began before 2008 have been completed, enrollment of 51-100 subjects (29.8%) was the most common, and the majority were phase II (54.4%). Most examined metastatic tumors (58.5%) and new trials per year increased 3.4-fold between 2009 and 2020. The majority were conducted in the United States (56.4%). The most common intervention strategy was radiation (32.1%), although between 2010-2020 procedural studies became the most frequent (2.4 per year). The majority were sponsored by academic institutions (63.2%), and over twenty years have sponsored 3.2-fold more studies than industry partners.

CONCLUSIONS

The number of clinical trials for spine tumor therapies has rapidly increased over the past 15 years, driven by studies at United States academic medical institutions investigating radiosurgery for treatment of metastases. Targeted therapies for tumor subtypes and sequelae have updated international best practices.

The Impact of ASA Status on Cost of Care and Length of Stay Following Posterior Cervical Decompression and Fusion

BACKGROUND

Increasing numbers of posterior cervical decompression and fusion (PCDF) over the past decade have raised the prospect of bundled payment plans. The American Society of Anesthesiologists (ASA) Physical Status Classification system may enable accurate estimation of healthcare costs, length of stay, and other postoperative outcomes in PCDF patients.

OBJECTIVE

To evaluate correlations between ASA and postoperative outcomes, length of stay (LOS), and healthcare costs in patients undergoing PCDF.

METHODS

971 patients that underwent PCDF between 2008 and 2016 at a single institution were evaluated by low (I and II) versus high (III and IV) ASA. Demographics were compared using univariate analysis. Cost of care, LOS and postoperative complications were compared using multivariable logistic and linear regression, controlling for gender, age, length of surgery and number of segments fused.

RESULTS

The high ASA cohort had greater mean age (62 vs. 55, p<0.0001) and higher Elixhauser comorbidity index (ECI) scores (p<0.0001). ASA was independently associated with longer LOS (+2.1 days, CI: 1.3-2.9; p<0.0001) and higher cost (+$2,936, CI: $1,457-$4,415; p<0.0001). High ASA patients were more likely to have a non-home discharge (3.9, 95% CI 2.8-5.6, p<0.0001), delayed extubation (3.2, 95% CI 1.4-7.3, p=0.006), ICU stay (2.4, 95% CI 1.5-3.7, p=0.0001), in-hospital complications (1.5, 95% CI 1.0-2.2, p=0.03) and 30-day (3.2, 95% CI 1.5-6.8, p=0.003) and 90-day (3.2, 95% CI 1.8-5.7, p=0.0001) readmission.

CONCLUSIONS

High ASA is strongly associated with increased costs, LOS and adverse outcomes following PCDF. Therefore, ASA could be useful for preoperative prediction of these outcomes.

The Impact of Non-Elective Admission on Cost of Care and Length of Stay in Anterior Cervical Discectomy and Fusion: A Propensity-Matched Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate the impact of admission status on patient outcomes and healthcare costs in anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Undergoing ACDF non-electively has been associated with higher patient comorbidity burdens. However, the impact of non-elective status on the total cost of hospital stay has yet to be quantified.

METHODS

Patients undergoing ACDF at a single institution were placed into elective or non-elective cohorts. Propensity score-matching analysis in a 5:1 ratio controlling for insurance type and comorbidities was used to minimize selection bias. Demographics were compared by univariate analysis. Cost of care, length of stay (LOS), and clinical outcomes were compared between groups using multivariable linear and logistic regression with elective patients as reference cohort. All analyses controlled for sex, preoperative diagnosis, elixhauser comorbidity index (ECI), age, length of surgery, number of segments fused, and insurance type.

RESULTS

Of 708 patients in the final ACDF cohort, 590 underwent an elective procedure and 118 underwent a non-elective procedure. The non-elective group was significantly younger (53.7 vs. 49.5 yr; P = 0.0007). Cohorts had similar proportions of private versus public health insurance, although elective had higher rates of commercial insurance (39.22% vs. 15.25%; P < 0.0001) and non-elective had higher rates of managed care (32.77% vs. 56.78%; P < 0.0001). Operation duration was significantly longer in non-elective patients (158 vs. 177 minutes; P = 0.01). Adjusted analysis also demonstrated that admission status independently affected cost (+$6877, 95% confidence interval [CI]: $4906-$8848; P < 0.0001) and LOS (+4.9 days, 95% CI: 3.9-6.0; P < 0.0001) for the non-elective cohort. The non-elective cohort was significantly more likely to return to the operating room (OR: 3.39; 95% CI: 1.37-8.36, P = 0.0008) and experience non-home discharge (OR: 10.95; 95% CI: 5.00-24.02, P < 0.0001).

CONCLUSION

Patients undergoing ACDF non-electively had higher cost of care and longer LOS, as well as higher rates of postoperative adverse outcomes.Level of Evidence: 3.

Anesthesia provider performance in the first two years of merit-based incentive payment system: Shifts in reporting and predictors of receiving bonus payments

STUDY OBJECTIVE

The Merit-Based Incentive Payment System (MIPS) program was intended to align CMS quality and incentive programs. To date, no reports have described anesthesia clinician performance in the first two years of the program.

DESIGN

Observational retrospective cohort study.

SETTING

Centers for Medicare and Medicaid Services public datasets for their Quality Payment Program.

PATIENTS

Anesthesia clinicians who participated in MIPS for 2017 and 2018 performance years.

INTERVENTIONS

Descriptive statistics compared anesthesia clinician characteristics, practice setting, and MIPS performance between the two years to determine associations with MIPS-based payment adjustments.

MEASUREMENTS

Logistic regression identified independent predictors of bonus payments for exceptional performance.

MAIN RESULTS

Compared with participants in 2017 (n = 25,604), participants in 2018 (n = 54,381) had a higher proportion of reporting through groups and alternative payment models (APMs) than as individuals (p < 0.001). The proportion of clinicians earning performance bonuses increased from 2017 to 2018 except for those MIPS participants reporting as individuals. Median total MIPS scores were higher in 2018 than 2017 (84.6 vs. 82.4, p < 0.001), although median total scores fell for participants reporting as individuals (40.9 vs 75.5, p < 0.001). Among clinicians with scores in both years (n = 20,490), 10,559 (51.3%) improved their total score between 2017 and 2018, and 347 (1.7%) changed reporting from individual to APM. Reporting as an individual compared with group reporting (OR: 0.75; 95% CI: 0.71 to 0.80; p < 0.001) was associated with lower rates of bonus payments, as was having a greater proportion of patients dual-eligible for Medicaid and Medicare. Reporting through an APM (OR: 149.6; 95% CI: 110 to 203.4; p < 0.001) and increasing practice group size were associated with higher likelihood of bonus payments.

CONCLUSIONS

Anesthesia clinician MIPS participation and performance were strong during 2017 and 2018 performance years. Providers who reported through groups or APMs have a higher likelihood of receiving bonus payments.

Application of Cooperative Game Theory Principles to Interpret Machine Learning Models of Nonhome Discharge Following Spine Surgery

STUDY DESIGN

Retrospective analysis of prospectively acquired data.

OBJECTIVE

The aim of this study was to identify interaction effects that modulate nonhome discharge (NHD) risk by applying coalitional game theory principles to interpret machine learning models and understand variable interaction effects underlying NHD risk.

SUMMARY OF BACKGROUND DATA

NHD may predispose patients to adverse outcomes during their care. Previous studies identified potential factors implicated in NHD; however, it is unclear how interaction effects between these factors contribute to overall NHD risk.

METHODS

Of the 11,150 reviewed cases involving procedures for degenerative spine conditions, 1764 cases (15.8%) involved NHD. Gradient boosting classifiers were used to construct predictive models for NHD for each patient. Shapley values, which assign a unique distribution of the total NHD risk to each model variable using an optimal cost-sharing rule, quantified feature importance and examined interaction effects between variables.

RESULTS

Models constructed from features identified by Shapley values were highly predictive of patient-level NHD risk (mean C-statistic = 0.91). Supervised clustering identified distinct patient subgroups with variable NHD risk and their shared characteristics. Focused interaction analysis of surgical invasiveness, age, and comorbidity burden suggested age as a worse risk factor than comorbidity burden due to stronger positive interaction effects. Additionally, negative interaction effects were found between age and low blood loss, indicating that intraoperative hemostasis may be critical for reducing NHD risk in the elderly.

CONCLUSION

This strategy provides novel insights into feature interactions that contribute to NHD risk after spine surgery. Patients with positively interacting risk factors may require special attention during their hospitalization to control NHD risk.Level of Evidence: 3.

A Comparison of Outcomes for Spinal Trauma Patients at Level I and Level II Centers

STUDY DESIGN

Retrospective analysis of a national database.

OBJECTIVE

To characterize the spine trauma population, describe trauma center (TC) resources, and compare rates of outcomes between the American College of Surgeons (ACS) level I and level II centers.

SUMMARY OF BACKGROUND DATA

Each year, thousands of patients are treated for spinal trauma in the United States. Although prior analyses have explored postsurgical outcomes for patients with trauma, no study has evaluated these metrics for spinal trauma at level I and level II TCs.

MATERIALS AND METHODS

The ACS Trauma Quality Improvement Program was queried for all spinal trauma cases between 2013 and 2015, excluding polytrauma cases, patients discharged within 24 hours, data from TCs without a designated level, and patients transferred for treatment.

RESULTS

Although there were similar rates of severe spine traumas (Abbreviated Injury Scale≥3) at ACS level I and level II centers (P=0.7), a greater proportion of level I patients required mechanical ventilation upon emergency department arrival (P=0.0002). Patients at level I centers suffered from higher rates of infectious complications, including severe sepsis (0.58% vs. 0.31%, P=0.02) and urinary tract infections (3.26% vs. 2.34%, P=0.0009). Intensive care unit time (1.90 vs. 1.65 days, P=0.005) and overall length of stay (8.37 days vs. 7.44 days, P<0.0001) was higher at level I TCs. Multivariate regression revealed higher adjusted overall complication rates at level II centers (odds ratio, 1.15, 95% confidence interval, 1.06-1.24; P<0.001), but no difference in mortality (odds ratio, 1.18; 95% confidence interval, 0.92-1.52; P>0.10).

CONCLUSIONS

ACS level I TCs possess larger surgical staff and are more likely to be academic centers. Patients treated at level I centers experience fewer overall complications but have a greater incidence of infectious complications. Mortality rates are not statistically different.

Surgeon experience influences patient characteristics and outcomes in spine deformity surgery

PURPOSE

To characterize differences in patient demographics and outcomes by surgeon experience in a cohort of patients undergoing adult spinal deformity surgery.

METHODS

Patients undergoing degenerative spinal deformity were included. Patients whose surgeons graduated from fellowship ≤ 5 years prior to surgery versus > 5 years were compared. Multivariable linear and logistic regression, controlling for age, sex, comorbidity burden, number of segments fused, blood loss and operative time were used to evaluate differences in outcomes. Characteristics of operative invasiveness were plotted against surgeons' level of experience, and trends in these measures were assessed with univariate linear regression.

RESULTS

Three-hundred sixty-three patients were included. 147 patients' surgeons had ≤ 5 years of experience. Patient demographics were evenly matched. Patients with junior surgeons had more pre-existing medical complications, and senior surgeons were less likely to take care of patients with Medicare/Medicaid (p < 0.001). Junior surgeons were more likely to operate on non-elective patients (p < 0.001). Patients of junior surgeons received larger fusions (9.6 vs. 7.6 segments fused, p < 0.001). There were no differences in complication rates or death. Patients of junior surgeons had longer overall length of stays (p = 0.037) and higher rates of nonhome discharge (OR 2.0, p < 0.001), 30- and 90-day (p < 0.005) ED visits, and higher costs (+ $8548, 95% CI: $1596 to $15,502; p = 0.016).

CONCLUSION

Junior surgeons tend to perform more extensive deformity operations on more medically complex patients compared to senior surgeons, associated with higher costs and more resource utilization than senior surgeons.

Surgery for spinal deformity: non-elective admission status is associated with higher cost of care and longer length of stay

INTRODUCTION

Surgery is commonly indicated for adult spinal deformity. Annual rates and costs of spinal deformity surgery have both increased over the past two decades. However, the impact of non-elective status on total cost of hospitalization and patient outcomes has not been quantified.

OBJECTIVE

To evaluate the impact of admission status on patient outcomes and healthcare costs in spinal deformity surgery.

METHODS

All patients who underwent spinal deformity surgery at a single institution between 2008 and 2016 were grouped by admission status: elective, emergency (ED), or transferred. Demographics were compared by univariate analysis. Cost of care and length of stay (LOS) were compared between admission statuses using multivariable linear regression with elective admissions as reference. Multivariate logistic regression was utilized to assess in-hospital complications, discharge destination, and readmission rates.

RESULTS

There were 427 spinal deformity surgeries included in this study. Compared to elective patients, ED patients had higher Elixhauser Comorbidity Index scores (p < 0.0001), longer LOS (+ 10.9 days, 97.5% CI 6.1-15.6 days, p < 0.0001), and higher costs (+ $20,076, 97.5% CI $9,073-$31,080, p = 0.0008). Transferred patients had significantly higher Elixhauser scores (p = 0.0002), longer LOS (+ 8.8 days, 97.5% CI 3.0-14.7 days, p < 0.0001), and higher rates of non-home discharge (OR = 15.8, 97.5% CI 2.3-110.0, p = 0.001).

CONCLUSION

Patients admitted from the ED undergoing spinal deformity surgery had significantly higher cost of care and longer LOS compared to elective patients. Transferred patients had significantly longer LOS and a higher rate of non-home discharge compared to elective patients.

Surgical Start Time Is Not Predictive of Microdiscectomy Outcomes

STUDY DESIGN

Retrospective analysis of clinical data from a single institution.

OBJECTIVE

The objective of this study was to assess the time of surgery as a possible predictor for outcomes, length of stay, and cost following microdiscectomy.

SUMMARY OF BACKGROUND DATA

The volume of microdiscectomy procedures has increased year over year, heightening interest in surgical outcomes. Previous investigations have demonstrated an association between time of procedures and clinical outcomes in various surgeries, however, no study has evaluated its influence on microdiscectomy.

METHODS

Demographic and outcome variables were collected from all patients that underwent a nonemergent microdiscectomy between 2008 and 2016. Patients were divided into 2 cohorts: those receiving surgery before 2 pm were assigned to the early group and those with procedures beginning after 2 pm were assigned to the late group. Outcomes and patient-level characteristics were compared using bivariate, multivariable logistic, and linear regression models. Adjusted length of stay and cost were coprimary outcomes. Secondary outcomes included operative complications, nonhome discharge, postoperative emergency department visits, or readmission rates.

RESULTS

Of the 1261 consecutive patients who met the inclusion criteria, 792 were assigned to the late group and 469 were assigned to the early group. There were no significant differences in demographics or baseline characteristics between the 2 cohorts. In the unadjusted analysis, mean length of stay was 1.80 (SD=1.82) days for the early group and 2.00 (SD=1.70) days for the late group (P=0.054). Mean direct cost for the early cohort was $5088 (SD=$4212) and $4986 (SD=$2988) for the late cohort (P=0.65). There was no difference in adjusted length of stay or direct cost. No statistically significant differences were found in operative complications, nonhome discharge, postoperative emergency department visits, or readmission rates between the 2 cohorts.

CONCLUSION

The study findings suggest that early compared with late surgery is not significantly predictive of surgical outcomes following microdiscectomy.

Assessing the Impact of Neurogenic Claudication on Outcomes Following Decompression With Lumbar Interbody Fusions in Patients With Lumbar Spinal Stenosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To conduct the first comprehensive national-level study examining specific risks, outcomes, and costs surrounding surgical treatment of lumar spinal stenosis (LSS) in patients with and without neurogenic claudication (NC).

METHODS

Data for patients with or without NC who underwent decompression with a lumbar interbody fusion approached anteriorly (ALIF), posteriorly (PLIF), or laterally (LLIF) for LSS was collected from the 2013-2014 National Inpatient Sample using International Classification of Disease codes.

RESULTS

A total of 121 025 LSS cases without NC and 20 095 cases with NC were included in this study. The most significant complications associated with NC status by organ system included renal (P = .0030) and hematological complications (P = .0003). Multivariate regression controlling for key demographic and comorbidity variables showed that patients with NC did not have significantly higher odds of complication, non-home discharge, or extended hospitalization compared to patients without NC regardless of fusion type. Interestingly, NC patients had comparatively lower total charges for their hospitalization following PLIFs (P = .0001) and LLIFs (P < .0001), but not ALIFs (P = .6121).

CONCLUSION

NC does not appear to significantly increase odds of adverse outcomes following fusion in LSS. Given the large prevalence of LSS and coincidental NC, these findings may carry important implications in managing this challenging patient population and justifies future prospective investigation of this topic.

Comparison of Surgical Outcomes of Microdiskectomy Procedures by Patient Admission Status

OBJECTIVE

We sought to compare the cost and in-hospital outcomes following lumbar microdiskectomy procedures by admission type.

METHODS

Patients undergoing lumbar microdiskectomy at a single institution from 2008 to 2016 following an elective admission (EL) were compared against those who were admitted from the emergency department (ED) or from elsewhere within or outside the hospital system (TR) for their perioperative outcomes and cost. Multivariable modeling controlled for age, sex, self-reported race, Elixhauser comorbidity score, payer type, number of segments, and procedure length.

RESULTS

Of the 1249 patients included in this study, 1116 (89.4%) were admitted electively while 123 (9.8%) were admitted from the ED and 10 (0.8%) were transferred from other hospitals. EL patients had significantly lower comorbidity burdens (P < 0.0001). Univariate and multivariable analyses revealed that transfer admission patients experienced significantly longer hospitalizations (ED: +1.7 days; P < 0.0001; TR: +5.3 days; P < 0.0001) and higher direct costs (ED: $1889; P < 0.0001; TR: $7001; P < 0.0001) compared with EL patients. Despite these risks, ED and TR patients only had increased odds of nonhome discharge compared with EL patients (ED: 3.4; P = 0.002; TR: 7.9; P = 0.02).

CONCLUSIONS

Patients admitted as transfers and from the ED had significantly increased hospitalization lengths of stay and direct costs compared with electively admitted patients.

Drivers of Prolonged Hospitalization Following Spine Surgery: A Game-Theory-Based Approach to Explaining Machine Learning Models

BACKGROUND

Understanding the interactions between variables that predict prolonged hospital length of stay (LOS) following spine surgery can help uncover drivers of this risk in patients. This study utilized a novel game-theory-based approach to develop explainable machine learning models to understand such interactions in a large cohort of patients treated with spine surgery.

METHODS

Of 11,150 patients who underwent surgery for degenerative spine conditions at a single institution, 3,310 (29.7%) were characterized as having prolonged LOS. Machine learning models predicting LOS were built for each patient. Shapley additive explanation (SHAP) values were calculated for each patient model to quantify the importance of features and variable interaction effects.

RESULTS

Models using features identified by SHAP values were highly predictive of prolonged LOS risk (mean C-statistic = 0.87). Feature importance analysis revealed that prolonged LOS risk is multifactorial. Non-elective admission produced elevated SHAP values, indicating a clear, strong risk of prolonged LOS. In contrast, intraoperative and sociodemographic factors displayed bidirectional influences on risk, suggesting potential protective effects with optimization of factors such as estimated blood loss, surgical duration, and comorbidity burden.

CONCLUSIONS

Meticulous management of patients with high comorbidity burdens or Medicaid insurance who are admitted non-electively or spend clinically indicated time in the intensive care unit (ICU) during their hospitalization course may be warranted to reduce their risk of unanticipated prolonged LOS following spine surgery.

LEVEL OF EVIDENCE

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

Utilization of the American Society of Anesthesiologists (ASA) classification system in evaluating outcomes and costs following deformity spine procedures

PURPOSE

Adult spinal deformity (ASD) has increased prevalence in aging populations. Due to the high cost of surgery, studies have evaluated risk factors that predict readmissions and poor outcomes. The American Society of Anesthesiologists (ASA) classification system has been applied to patients with ASD to assess preoperative health and assess the correlation between ASA class and postoperative complications. This study evaluates the relationship between ASA and complications, length of stay (LOS), and direct costs following spine deformity surgery.

METHODS

Patients undergoing spine deformity surgery at a single institution from 2008-2016 were included and stratified based upon ASA status. Primary outcomes included patient demographics, adjusted LOS, and cost of care. Secondary measures compared between cohorts included adverse events, non-home discharge, and readmission rates.

RESULTS

442 patients with ASD were included in this study. Higher ASA class was correlated with greater Elixhauser Comorbidity Index (ECI) scores (p < 0.0001) and older age (p < 0.0001). Univariate analysis showed longer LOS (p < 0.0001) and greater direct costs in patients with higher ASA class (p < 0.0001). Patients in ASA Class III or IV had the greatest incidence of ICU stay when compared to patients without systemic disease (p < 0.0001). Upon multivariable regression analysis, high ASA class was associated with higher rates of non-home discharge (OR 5.0, 95% CI 3.1-8.1). Direct costs were greater for higher ASA class (regression estimate =  + $9,666, p = 0.002).

CONCLUSION

This study demonstrates that ASA class is correlated with a more complicated postoperative hospital course, greater rates of non-home discharge, total direct costs in spine deformity patients.

Lower Mortality and Morbidity with Low-Molecular-Weight Heparin for Venous Thromboembolism Prophylaxis in Spine Trauma

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

The objective of this study was to evaluate outcomes between patients receiving LMWH versus UH in a retrospective cohort of patients with spine trauma.

SUMMARY OF BACKGROUND DATA

Although multiple clinical trials have been conducted, current guidelines do not have enough evidence to suggest low-molecular-weight heparin (LMWH) or unfractionated heparin (UH) for venous thromboembolism (VTE) prophylaxis in spine trauma.

METHODS

Patients with spine trauma in the Trauma Quality Improvement Program datasets were identified. Those who died, were transferred within 72 hours, were deemed to have a fatal injury, were discharged within 24 hours, suffered from polytrauma, or were missing data for VTE prophylaxis were excluded. A propensity score was created using age, sex, severity of injury, time to prophylaxis, presence of a cord injury, and altered mental status or hypotension upon arrival, and inverse probability weighted logistic regression modeling was used to evaluate mortality, venous thromboembolic, return to operating room, and total complication rates. E values were used to calculate the likelihood of unmeasured confounders.

RESULTS

Those receiving UH (n = 7172) were more severely injured (P < 0.0001), with higher rates of spinal cord injury (32.26% vs. 25.32%, P < 0.0001) and surgical stabilization (29.52% vs. 22.94%, P < 0.0001) compared to those receiving LMWH (n = 20,341). Patients receiving LMWH had lower mortality (odds ratio [OR]: 0.47; 95% CI: 0.42-0.53; P < 0.001; E = 3.68), total complication (OR: 0.92; 95% CI: 0.88-0.95; P < 0.001; E = 1.39), and VTE event (OR: 0.80; 95% CI: 0.72-0.88; P < 0.001; E = 1.81) rates than patients receiving UH. There were no differences in rates of unplanned return to the operating room (OR: 1.01; 95% CI: 0.80-1.27; P = 0.93; E = 1.11).

CONCLUSION

There is an association between lower mortality and receiving LMWH for VTE prophylaxis in patients with spine trauma. A large randomized clinical trial is necessary to confirm these findings.

LEVEL OF EVIDENCE

3.

Utility of the Hospital Frailty Risk Score for Predicting Adverse Outcomes in Degenerative Spine Surgery Cohorts

BACKGROUND

As spine surgery becomes increasingly common in the elderly, frailty has been used to risk stratify these patients. The Hospital Frailty Risk Score (HFRS) is a novel method of assessing frailty using International Classification of Diseases, Tenth Revision (ICD-10) codes. However, HFRS utility has not been evaluated in spinal surgery.

OBJECTIVE

To assess the accuracy of HFRS in predicting adverse outcomes of surgical spine patients.

METHODS

Patients undergoing elective spine surgery at a single institution from 2008 to 2016 were reviewed, and those undergoing surgery for tumors, traumas, and infections were excluded. The HFRS was calculated for each patient, and rates of adverse events were calculated for low, medium, and high frailty cohorts. Predictive ability of the HFRS in a model containing other relevant variables for various outcomes was also calculated.

RESULTS

Intensive care unit (ICU) stays were more prevalent in high HFRS patients (66%) than medium (31%) or low (7%) HFRS patients. Similar results were found for nonhome discharges and 30-d readmission rates. Logistic regressions showed HFRS improved the accuracy of predicting ICU stays (area under the curve [AUC] = 0.87), nonhome discharges (AUC = 0.84), and total complications (AUC = 0.84). HFRS was less effective at improving predictions of 30-d readmission rates (AUC = 0.65) and emergency department visits (AUC = 0.60).

CONCLUSION

HFRS is a better predictor of length of stay (LOS), ICU stays, and nonhome discharges than readmission and may improve on modified frailty index in predicting LOS. Since ICU stays and nonhome discharges are the main drivers of cost variability in spine surgery, HFRS may be a valuable tool for cost prediction in this specialty.

Correction to: Adult spinal deformity surgery: the effect of surgical start time on patient outcomes and cost of care

The original version of this article unfortunately contained a mistake. The first name of the author "Samuel Z. Maron" was incorrectly provided as "Sam" instead of "Samuel".

Machine Learning With Feature Domains Elucidates Candidate Drivers of Hospital Readmission Following Spine Surgery in a Large Single-Center Patient Cohort

BACKGROUND

Unplanned hospital readmissions constitute a significant cost burden in healthcare. Identifying factors contributing to readmission risk presents opportunities for actionable change to reduce readmission rates.

OBJECTIVE

To combine machine learning classification and feature importance analysis to identify drivers of readmission in a large cohort of spine patients.

METHODS

Cases involving surgical procedures for degenerative spine conditions between 2008 and 2016 were retrospectively reviewed. Of 11 150 cases, 396 patients (3.6%) experienced an unplanned hospital readmission within 30 d of discharge. Over 75 pre-discharge variables were collected and categorized into demographic, perioperative, and resource utilization feature domains. Random forest classification was used to construct predictive models for readmission from feature domains. An ensemble tree-specific method was used to quantify and rank features by relative importance.

RESULTS

In the demographics domain, age and comorbidity burden were the most important features for readmission prediction. Surgical duration and intraoperative oral morphine equivalents were the most important perioperative features, whereas total direct cost and length of stay were most important in the resource utilization domain. In supervised learning experiments for predicting readmission, the demographic domain model performed the best alone, suggesting that demographic features may contribute more to readmission risk than perioperative variables following spine surgery. A predictive model, created using only enriched features showing substantial importance, demonstrated improved predictive capacity compared to previous models, and approached the performance of state-of-the-art, deep-learning models for readmission.

CONCLUSION

This strategy provides insight into global patterns of feature importance and better understanding of drivers of readmissions following spine surgery.

A Comparison of the Elixhauser and Charlson Comorbidity Indices: Predicting In-Hospital Complications Following Anterior Lumbar Interbody Fusions

OBJECTIVE

The Elixhauser Comorbidity Index (ECI) and Charlson Comorbidity Index (CCI) are commonly used measures that use administrative data to characterize a patient's comorbidity burden. The purpose of this study was to compare the ability of these measures to predict outcomes following anterior lumbar interbody fusion.

METHODS

The National Inpatient Sample was queried for all ALIF procedures between 2013 and 2014. The area under the receiver operating curve (AUC) was used to compare the ECI and CCI in their ability to predict postoperative complications when incorporated into a base model containing age, sex, race, and primary payer. Percent superiority was computed using AUC values for ECI, CCI, and base models.

RESULTS

A total of 43,930 hospitalizations were included in this study. The ECI was superior to the CCI and baseline models in predicting minor (AUC 71 vs. 0.66, P < 0.0001) and major (AUC 0.74 vs. 0.67, P < 0.0001) complications. When evaluating individual complications, the ECI was superior to the CCI in predicting airway complications (65% superior, AUC 0.85 vs. 0.72, P = 0.0001); hemorrhagic anemia (83% superior, AUC 0.71 vs. 0.66, P < 0.0001); myocardial infarction (76% superior, AUC 0.86 vs. 0.67, P < 0.0001); cardiac arrest (75% superior, AUC 0.85 vs. 0.67, P < 0.0001); pulmonary embolism (105% superior, AUC 0.91 vs. 0.71, P < 0.0001); and urinary tract infection (43% superior, AUC 0.76 vs. 0.73, P = 0.046).

CONCLUSIONS

The ECI was superior to the CCI in predicting 6 of the 15 complications analyzed in this study. Combined with previous results, the ECI may be a better predictive model in spine surgery.

Large Rises in Thoracolumbar Fusions by 2040: A Cause for Concern with an Increasingly Elderly Surgical Population

BACKGROUND

With a growing aging population in the United States, the number of operative lumbar spine pathologies continues to grow. Therefore, our objective was to estimate the future demand for lumbar spine surgery volumes for the United States to the year 2040.

METHODS

The National/Nationwide Inpatient Sample was queried for years 2003-2015 for anterior interbody and posterior lumbar fusions (ALIF, PLF) to create national estimates of procedural volumes for those years. The average age and comorbidity burden was characterized, and Poisson modeling controlling for age and sex allowed for surgical volume prediction to 2040 in 10-year increments. Age was grouped into categories (<25, 25-34, 35-44, 45-54, 55-64, 65-74, 75-84, and >85 years), and estimates of surgical volumes for each age subgroup were created.

RESULTS

ALIF volume is expected to increase from 46,903 to 55,528, and PLF volume is expected to increase from 248,416 to 297,994 from 2020 to 2040. For ALIF, the largest increases are expected in the 45-54 years (10,316 to 12,216) and 75-84 years (2,898 to 5,340) age groups. Similarly the largest increases in PLF will be seen in the 65-74 years (71,087 to 77,786) and 75-84 years (28,253 to 52,062) age groups.

CONCLUSIONS

The large increases in expected volumes of ALIF and PLF could necessitate training of more spinal surgeons and an examination of projected costs. Further analyses are needed to characterize the needs of this increasingly large population of surgical patients.

A case of adult α-type spinal deformity with spinal cord rotation greater than 90°

This report describes a 42-year-old man who presented with an α-type spinal deformity with a Cobb angle of 224.9° and associated spinal cord rotation greater than 90°. Preoperative imaging revealed extensive spinal deformity, and 3D modeling confirmed the α-type nature of his deformity. Intraoperative photography demonstrated spinal cord rotation greater than 90°, which likely contributed to the patient's poor neurological status. Reports of patients with Cobb angles ≥ 100° are rare, and to the authors' knowledge, there have been no published cases of adult α-type spinal deformity. Furthermore, very few cases or case series of spinal cord rotation have been published previously, with no single patient having rotation greater than 90° to the authors' knowledge. Given these two rarities presenting in the same patient, this report can provide important insights into the operative management of this difficult form of spinal deformity.

Predicting Trends in Cervical Spinal Surgery in the United States from 2020 to 2040

OBJECTIVE

We sought to predict surgical volumes for 2 common cervical spine procedures from 2020 to 2040.

METHODS

Using the National Inpatient Sample from 2003-2016, nationwide estimates of anterior cervical diskectomy and fusion (ACDF) and posterior cervical decompression and fusion (PCDF) volumes were calculated using International Classification of Diseases, Ninth and Tenth Revision (ICD-9, ICD-10) procedure codes. With data from the U.S. Census Bureau, estimates of the U.S. population were used to create Poisson models controlling for age and sex. Age was categorized into ranges (<25 years old, 25-34, 35-44, 45-54, 55-64, 65-74, 75-84, and >85), and estimates of surgical volume for each age group were created.

RESULTS

From 2020-2040, increases in surgical volume from 13.3% (153,288-173,699) and 19.3% (29,620-35,335) are expected for ACDF and PCDF, respectively. For ACDF, the largest increases are expected in the 45-54 (42,077-49,827) and 75-84 (8065-14,862) age groups, whereas for PCDF, the largest increases will be seen in the 75-84 (3710-6836) age group. In accordance with an aging population, modest increases will be seen for ACDF (858-1847) and PCDF (730-1573) in the >85-year-old cohort.

CONCLUSIONS

As expected, large growth in cervical spine surgical volumes is likely to be seen, which could indicate a need for increased numbers of spinal neurosurgeons and orthopedic surgeons. Further studies are needed to investigate the needs of the field in light of these expected increases in volume.

Increases in Subdural Hematoma with an Aging Population-the Future of American Cerebrovascular Disease

BACKGROUND

Subdural hematomas (SDHs) are a common and dangerous condition, with potential for a rapid rise in incidence given the aging U.S. population, but the magnitude of this increase is unknown. Our objective was to characterize the number of SDHs and practicing neurosurgeons from 2003-2016 and project these numbers to 2040.

METHODS

Using the National Inpatient Sample years 2003-2016 (nearly 500 million hospitalizations), all hospitalizations with a diagnosis of SDH were identified and grouped by age. Numerical estimates of SDHs were projected to 2040 in 10-year increments for each age group using Poisson modeling with population estimates from the U.S. Census Bureau. The number of neurosurgeons who billed the Centers for Medicare and Medicaid Services from 2012 to 2017 was noted and linearly projected to 2040.

RESULTS

From 2020-2040, SDH volume is expected to increase by 78.3%, from 135,859 to 208,212. Most of this increase will be seen in the elderly, as patients 75-84 years old will experience an increase from 37,941 to 69,914 and patients older than 85 years old will experience an increase from 31,200 to 67,181. The number of neurosurgeons is projected to increase from 4675 in 2020 to 6252 in 2040.

CONCLUSIONS

SDH is expected to increase significantly from 2020-2040, with the majority of this increase being concentrated in elderly patients. While the number of neurosurgeons will also increase, the ability of current neurosurgical resources to properly handle this expected increase in SDH will need to be addressed on a national scale.

Characterizing the risk and outcome profiles of lumbar fusion procedures in patients with opioid use disorders: a step toward improving enhanced recovery protocols for a unique patient population

OBJECTIVEThe authors set out to conduct the first national-level study assessing the risks and outcomes for different lumbar fusion procedures in patients with opioid use disorders (OUDs) to help guide the future development of targeted enhanced recovery after surgery (ERAS) protocols for this unique population.METHODSData for patients with or without OUDs who underwent an anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), or lateral transverse lumbar interbody fusion (LLIF) for lumbar disc degeneration (LDD) were collected from the 2013-2014 National (Nationwide) Inpatient Sample database. Multivariable logistic regression was implemented to analyze how OUD status impacted in-hospital complications, length of hospital stay, discharge disposition, and total charges by procedure type.RESULTSA total of 139,995 patients with LDD were identified, with 1280 patients (0.91%) also having a concurrent OUD diagnosis. Overall complication rates were higher in OUD patients (48.44% vs 31.01%, p < 0.0001). OUD patients had higher odds of pulmonary (p = 0.0006), infectious (p < 0.0001), and hematological (p = 0.0009) complications. Multivariate regression modeling of outcomes by procedure type showed that after ALIF, OUD patients had higher odds of nonhome discharge (p = 0.0007), extended hospitalization (p = 0.0002), and greater total charges (p = 0.0054). This analysis also revealed that OUD patients faced higher odds of complication (p = 0.0149 and p = 0.0471), extended hospitalization (p = 0.0439 and p = 0.0001), and higher total charges (p < 0.0001 and p < 0.0001) after PLIF and LLIF procedures, respectively.CONCLUSIONSObtaining a better understanding of the risks and outcomes that OUD patients face perioperatively is a necessary step toward developing more effective ERAS protocols for this vulnerable population. This study, which sought to characterize the outcome profiles for lumbar fusion procedures in OUD patients on a national level, found that this population tended to experience increased odds of complications, extended hospitalization, nonhome discharge, and higher total costs. Results from this study warrant future prospective studies to better the understanding of these associations and to further the development of better ERAS programs that may improve patient care and reduce cost burden.

A National Snapshot Detailing the Impact of Parkinson's Disease on the Cost and Outcome Profiles of Fusion Procedures for Cervical Myelopathy

BACKGROUND

Studies suggest a higher prevalence of cervical deformities in Parkinson's Disease (PD) patients who predispose to cervical myelopathy (CM). Despite the profound effect of CM on function and quality of life, no study has assessed the influence of PD on costs and outcomes of fusion procedures for CM.

OBJECTIVE

To conduct the first national-level study that provides a snapshot of the current outcome and cost profiles for different fusion procedures for CM in PD and non-PD populations.

METHODS

Patients with or without PD who underwent cervical decompression and fusion anteriorly (ACDF), posteriorly (PCDF), or both (Frontback), for CM were identified from the 2013 to 2014 National Inpatient Sample using International Classification of Disease codes.

RESULTS

A total of 75 870 CM patients were identified, with 535 patients (0.71%) also having PD. Although no difference existed between in-hospital mortality rates, overall complication rates were higher in PD patients (38.32% vs 22.05%; P < .001). PD patients had higher odds of pulmonary (P = .002), circulatory (P = .020), and hematological complications (P = .035). Following ACDFs, PD patients had higher odds of complications (P = .035), extended hospitalization (P = .026), greater total charges (P = .003), and nonhome discharge (P = .006). Although PCDFs and Frontbacks produced higher overall complication rates for both populations than ACDFs, PD status did not affect complication odds for these procedures.

CONCLUSION

PD may increase risk for certain adverse outcomes depending on procedure type. This study provides data with implications in healthcare delivery, policy, and research regarding a patient population that will grow as our population ages and justifies further investigation in future prospective studies.

Perioperative Outcomes of Spinal Cord Stimulator Placement in Patients with Complex Regional Pain Syndrome Compared with Patients without Complex Regional Pain Syndrome

BACKGROUND AND OBJECTIVE

Complex regional pain syndrome (CRPS) is a multifaceted disorder resulting in an abnormal pain response to tissue injury. Among key CRPS features are neurogenic inflammation, maladaptive plasticity, and vasomotor dysfunction, which can result in severe pain and disability. Spinal cord stimulation (SCS) is an efficacious treatment for several chronic pain conditions and may improve pain and life quality in CRPS patients with CRPS. However, little information exists regarding perioperative outcomes of patients with CRPS undergoing surgical implantation of an SCS device.

METHODS

Patients were included if they underwent an SCS procedure at our institution between 2008 and 2016 for chronic pain. Cases were excluded if the procedure involved stimulator removal or if it was an outpatient procedure. Multivariate regression assessed the effect of CRPS and other clinical variables on perioperative outcomes.

RESULTS

Eighty-one inpatient SCS implantation cases for chronic pain were included, with 9 patients (11.1%) having a CRPS diagnosis. The CRPS cohort received higher mean quantities of intraoperative opioids and had a lower proportion of patients reporting meaningful pain reduction (16.7%) in the 24-hour postoperative setting compared with patients without CRPS (35.9%), although this was not statistically significant. Multivariate regression modeling suggested that CRPS was a significant predictor of increased odds of extended time to the postanesthesia care unit discharge (P = 0.0406) and higher direct costs of hospitalization (P = 0.0326).

CONCLUSIONS

Our data suggest that CRPS may pose several unique risks in the perioperative period after inpatient SCS implantation. These findings support the need for future prospective investigations examining risks and outcomes for SCS procedures in this population.

Predicting In-Hospital Complications After Anterior Cervical Discectomy and Fusion: A Comparison of the Elixhauser and Charlson Comorbidity Indices

OBJECTIVE

The objective of this study was to determine the ability of the Elixhauser Comorbidity Index (ECI) and Charlson Comorbidity Index (CCI) to predict postoperative complications after anterior cervical discectomy and fusion (ACDF).

METHODS

This was a retrospective study of ACDF hospitalizations in the National Inpatient Sample from 2013 to 2014. The ECI and CCI were calculated, and patients who experienced postoperative complications were identified. The ability of these indexes to predict complications was compared using the c statistic (area under the receiver operating characteristic curve [AUC]). In addition, the CCI and ECI were compared with a base model that included age, sex, race, and primary payer.

RESULTS

A total of 261,780 patients were included. Patients who experienced a complication were more often male (P < 0.0001) and older (P < 0.0001). They also had a higher comorbidity burden as assessed by both the ECI (P < 0.0001) and the CCI (P < 0.0001). The ECI was superior in predicting airway complications (AUC, 0.81 vs. 0.75; P < 0.0001), hemorrhagic anemia (AUC, 0.67 vs. 0.63; P = 0.0015), pulmonary embolism (AUC, 0.91 vs. 0.77; P < 0.0001), wound dehiscence (AUC, 0.80 vs. 0.55; P = 0.0080), sepsis (AUC, 0.87 vs. 0.82; P = 0.0001), and septic shock (AUC, 0.94 vs. 0.83; P < 0.0001). The CCI was not found to be superior to the ECI for predicting any complications. Both were excellent for predicting mortality (ECI AUC, 0.87; CCI AUC, 0.90).

CONCLUSIONS

The ECI was superior to the CCI in predicting 6 of 15 complications in this study. Both are excellent tools for predicting mortality after ACDF.

The case for T2 pedicle subtraction osteotomy in the surgical treatment of rigid cervicothoracic deformity

OBJECTIVE

Rigid cervicothoracic kyphotic deformity (CTKD) remains a difficult pathology to treat, especially in the setting of prior cervical instrumentation and fusion. CTKD may result in chronic neck pain, difficulty maintaining horizontal gaze, and myelopathy. Prior studies have advocated for the use of C7 or T1 pedicle subtraction osteotomies (PSOs). However, these surgeries are fraught with danger and, most significantly, place the C7, C8, and/or T1 nerve roots at risk.

METHODS

The authors retrospectively reviewed their experience with performing T2 PSO for the correction of rigid CTKD. Demographics collected included age, sex, details of prior cervical surgery, and coexisting conditions. Perioperative variables included levels decompressed, levels instrumented, estimated blood loss, length of surgery, length of stay, complications from surgery, and length of follow-up. Radiographic measurements included C2-7 sagittal vertical axis (SVA) correction, and changes in the cervicothoracic Cobb angle, lumbar lordosis, and C2-S1 SVA.

RESULTS

Four male patients were identified (age range 55-72 years). Three patients had undergone prior posterior cervical laminectomy and instrumented fusion and developed postsurgical kyphosis. All patients underwent T2 PSO: 2 patients received instrumentation at C2-T4, and 2 patients received instrumentation at C2-T5. The median C2-7 SVA correction was 3.85 cm (range 2.9-5.3 cm). The sagittal Cobb angle correction ranged from 27.8° to 37.6°. Notably, there were no neurological complications.

CONCLUSIONS

T2 PSO is a powerful correction technique for the treatment of rigid CTKD. Compared with C7 or T1 PSO, there is decreased risk of injury to intrinsic hand muscle innervators, and there is virtually no risk of vertebral artery injury. Laminectomy may also be safer, as there is less (or no) scar tissue from prior surgeries. Correction at this distal level may allow for a greater sagittal correction. The authors are optimistic that these findings will be corroborated in larger cohorts examining this challenging clinical entity.

Lung adenocarcinoma presumed to be Pott's disease in a 28-year-old patient: A case report and review of literature

Background:

Tuberculous spondylitis (Pott’s disease), a common extrapulmonary manifestation of tuberculosis (TB), typically presents with back pain, tenderness, paraparesis/paraplegia, and various constitutional symptoms. Due to radiological similarities between Pott’s disease and lung cancer, some lung cancer patients may initially be erroneously diagnosed and treated for TB, allowing for extensive progression of their cancer.

Case Description:

A 28-year-old male presented with a chronic dry cough, weight loss, and 2 months of increased back pain accompanied by bilateral lower extremity weakness. Magnetic resonance imaging revealed an epidural collection causing compression of the spinal cord at the T5-T6 level. The initial diagnosis was Mycobacterium tuberculosis/Pott’s disease. A thoracic T4-T8 decompression fusion was performed; however, pathologic examination of the tissue revealed adenocarcinoma. Postoperatively, after the patient experienced several episodes of acute respiratory distress and a tension pneumothorax, lung imaging confirmed multiple tumor infiltrates along with lung cancer extending into the thoracic vertebrae. Pelvic studies also confirmed the presence of pelvic metastases. The patient passed away 3 weeks following surgery.

Conclusion:

In this case report, a 28-year-old male was treated for thoracic Pott’s disease that proved to be metastatic lung adenocarcinoma. To avoid such misdiagnoses in the future, physicians should better differentiate spinal TB from other malignancies that may affect the spine. This study underscores the importance of obtaining at least a chest X-ray in any patient with suspected Pott’s disease, irrespective of age, to help rule out lung cancer or other pathologies.