Extended Length of Stay in Elderly Patients after Anterior Cervical Discectomy and Fusion Is Not Attributable to Baseline Illness Severity or Postoperative Complications

Association Between Age-stratified Cohorts and Perioperative Complications and 30-day and 90-day Readmission in Patients Undergoing Single-level Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To assess perioperative complication rates and readmission rates after ACDF in a patient population of advanced age.

SUMMARY OF BACKGROUND DATA

Readmission rates after ACDF are important markers of surgical quality and, with recent shifts in reimbursement schedules, they are rapidly gaining weight in the determination of surgeon and hospital reimbursement.

METHODS

Patients 18 years of age and older who underwent elective single-level ACDF were identified in the National Readmissions Database (NRD) and stratified into 4 cohorts: 18-39 ("young"), 40-64 ("middle"), 65-74 ("senior"), and 75+ ("elderly") years of age. For each cohort, the perioperative complications, frequency of those complications, and number of patients with at least 1 readmission within 30 and 90 days of discharge were analyzed. χ 2 tests were used to calculate likelihood of complications and readmissions.

RESULTS

There were 1174 "elderly" patients in 2016, 1072 in 2017, and 1010 in 2018 who underwent ACDF. Their rate of any complication was 8.95%, 11.00%, and 13.47%, respectively ( P <0.0001), with dysphagia and acute posthemorrhagic anemia being the most common across all 3 years. They experienced complications at a greater frequency than their younger counterparts (15.80%, P <0.0001; 16.98%, P <0.0001; 21.68%, P <0.0001). They also required 30-day and 90-day readmission more frequently ( P <0.0001).

CONCLUSION

It has been well-established that advanced patient age brings greater risk of perioperative complications in ACDF surgery. What remains unsettled is the characterization of this age-complication relationship within specific age cohorts and how these complications inform patient hospital course. Our study provides an updated analysis of age-specific complications and readmission rates in ACDF patients. Orthopedic surgeons may account for the rise in complication and readmission rates in this population with the corresponding reduction in length and stay and consider this relationship before discharging elderly ACDF patients.

Weekend Admission Increases Risk of Readmissions Following Elective Cervical Spinal Fusion

Objective: The “weekend effect” occurs when patients cared for during weekends versus weekdays experience worse outcomes. But reasons for this effect are unclear, especially amongst patients undergoing elective cervical spinal fusion (ECSF). Our aim was to analyze whether index weekend admission affects 30- and 90-day readmission rates post-ECSF.Methods: All ECSF patients > 18 years were retrospectively identified from the 2016–2018 Healthcare Cost and Utilization Project Nationwide Readmissions Database (NRD), using unique patient linkage codes and International Classification of Diseases, Tenth Revision codes. Patient demographics, comorbidities, and outcomes were analyzed. Univariate logistic regression analyzed primary outcomes of 30- and 90-day readmission rates in weekday or weekend groups. Multivariate regression determined the impact of complications on readmission rates.Results: Compared to the weekday group (n = 125,590), the weekend group (n = 1,026) held a higher percentage of Medicare/Medicaid insurance, incurred higher costs, had longer length of stay, and fewer routine home discharge (all p < 0.001). There was no difference in comorbidity burden between weekend versus weekday admissions, as measured by the Elixhauser Comorbidity Index (p = 0.527). Weekend admissions had higher 30-day (4.30% vs. 7.60%, p < 0.001) and 90-day (7.80% vs. 16.10%, p < 0.001) readmission rates, even after adjusting for sex, age, insurance status, and comorbidities. All-cause complication rates were higher for weekend admissions (8.62% vs. 12.7%, p < 0.001), specifically deep vein thrombosis, infection, neurological conditions, and pulmonary embolism.Conclusion: Index weekend admission increases 30- and 90-day readmission rates after ECSF. In patients undergoing ECSF on weekends, postoperative care for patients at risk for specific complications will allow for improved outcomes and health care utilization.

Racial Differences in Patients Undergoing Anterior Cervical Discectomy and Fusion: A Multi-Site Study

STUDY DESIGN

This was a retrospective chart review.

OBJECTIVE

The objective of this study was to examine disparities within patients undergoing anterior cervical discectomy and fusion (ACDF) at a multi-site tertiary referral center with specific focus on factors related to length of stay (LOS).

SUMMARY OF BACKGROUND DATA

There are previously described racial disparities in spinal surgery outcomes and quality metrics.

METHODS

A total of 278 consecutive patients undergoing ACDF by 8 different surgeons over a 5-year period were identified retrospectively. Demographic data, including age at time of surgery, sex, smoking status, and self-identified race [White or African American (AA)], as well as surgical data and postoperative course were recorded. Preoperative health status was recorded, and comorbidities were scored by the Charlson Comorbidity Index. Univariable and multivariable linear regression models were employed to quantify the degree to which a patient's LOS was related to their self-identified race, demographics, and perioperative clinical data.

RESULTS

Of the 278 patients who received an ACDF, 71.6% (199) self-identified as White and 28.4% (79) identified as AA. AA patients were more likely to have an ACDF due to myelopathy, while White patients were more likely to have an ACDF due to radiculopathy (P=0.001). AA patients had longer LOS by an average of half a day (P=0.001) and experienced a larger percentage of extended stays (P=0.002). AA patients experienced longer overall operation times on average (P=0.001) across all different levels of fusion. AA race was not an independent driver of LOS (β=0.186; P=0.246).

CONCLUSIONS

As hypothesized, and consistent with previous literature on racial surgical disparities, AA race was associated with increased LOS, increased operative times, and increased indication of myelopathy in this study. Additional research is necessary to evaluate the underlying social determinants of health and other factors that may contribute to this study's results.

LEVEL OF EVIDENCE

Level III.

The incidence of acute myocardial infarction after elective spinal fusions or joint replacement surgery in the United States: a large-scale retrospective observational cohort study in 322,585 patients : Post-surgical myocardial infarction data

Background

Acute myocardial infarction (AMI) is an uncommon but fatal complication among patients undergoing elective spinal fusion surgery (SF), total hip arthroplasty (THA), and total knee arthroplasty (TKA). Our objective was to estimate the incidence of AMI among adults undergoing elective SF, THA, and TKA in different post-operative risk windows and characterize high-risk sub-populations in the United States.

Methods

A retrospective cohort study was conducted using data from a longitudinal electronic healthcare record (EHR) database from January 1, 2007 to June 30, 2018. ICD codes were used to identify SF, THA, TKA, AMI, and selected clinical characteristics. Incidence proportions (IPs) and 95% confidence intervals were estimated in the following risk windows: index hospitalization, ≤ 30, ≤ 90, ≤ 180, and ≤ 365 days post-operation.

Results

A total of 67,533 SF patients, 87,572 THA patients, and 167,480 TKA patients were eligible for the study. The IP of AMI after SF, THA, and TKA ranged from 0.36, 0.28, and 0.25% during index hospitalization to 1.05, 0.93, and 0.85% ≤ 365 days post-operation, respectively. The IP of AMI was higher among patients who were older, male, with longer hospital stays, had a history of AMI, and had a history of diabetes.

Conclusion

The IP of post-operative AMI was generally highest among the SF cohort compared to the THA and TKA cohorts. Additionally, potential high-risk populations were identified. Future studies in this area are warranted to confirm these findings via improved confounder control and to identify effect measure modifiers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13037-021-00305-6.

A Novel Scoring System to Predict Length of Stay After Anterior Cervical Discectomy and Fusion

INTRODUCTION

The movement toward reducing healthcare expenditures has led to an increased volume of outpatient anterior cervical diskectomy and fusions (ACDFs). Appropriateness for outpatient surgery can be gauged based on the duration of recovery each patient will likely need.

METHODS

Patients undergoing 1- or 2-level ACDFs were retrospectively identified at a single Level I spine surgery referral institution. Length of stay (LOS) was categorized binarily as either less than two midnights or two or more midnights. The data were split into training (80%) and test (20%) sets. Two multivariate regressions and three machine learning models were developed to predict a probability of LOS ≥ 2 based on preoperative patient characteristics. Using each model, coefficients were computed for each risk factor based on the training data set and used to create a calculatable ACDF Predictive Scoring System (APSS). Performance of each APSS was then evaluated on a subsample of the data set withheld from training. Decision curve analysis was done to evaluate benefit across probability thresholds for the best performing model.

RESULTS

In the final analysis, 1,516 patients had a LOS <2 and 643 had a LOS ≥2. Patient characteristics used for predictive modeling were American Society of Anesthesiologists score, age, body mass index, sex, procedure type, history of chronic pulmonary disease, depression, diabetes, hypertension, and hypothyroidism. The best performing APSS was modeled after a lasso regression. When applied to the withheld test data set, the APSS-lasso had an area under the curve from the receiver operating characteristic curve of 0.68, with a specificity of 0.78 and a sensitivity of 0.49. The calculated APSS scores ranged between 0 and 45 and corresponded to a probability of LOS ≥2 between 4% and 97%.

CONCLUSION

Using classic statistics and machine learning, this scoring system provides a platform for stratifying patients undergoing ACDF into an inpatient or outpatient surgical setting.

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.

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.

Portending Influence of Racial Disparities on Extended Length of Stay after Elective Anterior Cervical Discectomy and Interbody Fusion for Cervical Spondylotic Myelopathy

OBJECTIVE

The aim of this study was to investigate whether race is an independent predictor of extended length of stay (LOS) after elective anterior cervical discectomy and fusion (ACDF) for cervical spondylotic myelopathy (CSM).

METHODS

A retrospective cohort study was performed using the National Inpatient Sample database from 2016 to 2017. All adult patients undergoing ACDF for CSM were identified using the International Classification of Diseases, Tenth Revision, Clinical Modification coding system.

RESULTS

A total of 15,400 patients were identified, of whom 13,250 (86.0%) were Caucasian (C) and 2150 (14.0%) were African American (AA). The C cohort tended to be older, whereas the AA cohort had 2 times as many patients in the 0-25th income quartile. The prevalence of comorbidities was greater in the AA cohort. Intraoperative fusion levels were similar between the cohorts, whereas the AA cohort had a higher rate of cerebrospinal fluid leak/dural tear. In relation to the number of complications, the C cohort had a lower rate compared with the AA cohort (P = 0.006), including no complication (89.4% vs. 85.3%), 1 complication (9.9% vs. 12.8%), and >1 complication (0.7% vs. 1.9%). The AA cohort experienced significantly longer hospital stays (C, 1.9 ± 2.3 days vs. AA, 2.7 ± 3.5; P < 0.001), greater proportion of extended LOS (C, 17.5% vs. AA, 29.1%; P < 0.001) and nonroutine discharges (C, 16.1% vs. AA, 28.6%; P < 0.001). AA race was a significant independent risk factor for extended LOS (odds ratio, 1.98; 95% confidence interval, 1.50-2.61; P < 0.001).

CONCLUSIONS

Our study suggests that AA patients have a significantly higher risk of prolonged LOS after elective ACDF for CSM compared with C patients.

Enhanced recovery after spine surgery: a systematic review

OBJECTIVEEnhanced recovery after surgery (ERAS) is a multidimensional approach to improving the care of surgical patients using subspecialty- and procedure-specific evidence-based protocols. The literature provides evidence of the benefits of ERAS implementation, which include expedited functional recovery, decreased postoperative morbidity, reduced costs, and improved subjective patient experience. Although extensively examined in other surgical areas, ERAS principles have been applied to spine surgery only in recent years. The authors examine studies investigating the application of ERAS programs to patients undergoing spine surgery.METHODSThe authors conducted a systematic review of the PubMed and MEDLINE databases up to November 20, 2018.RESULTSTwenty full-text articles were included in the qualitative analysis. The majority of studies were retrospective reviews of nonrandomized data sets or qualitative investigations lacking formal control groups; there was 1 protocol for a future randomized controlled trial. Most studies demonstrated reduced lengths of stay and no increase in rates of readmissions or complications after introduction of an ERAS pathway.CONCLUSIONSThese introductory studies demonstrate the potential of ERAS protocols, when applied to spine procedures, to reduce lengths of stay, accelerate return of function, minimize postoperative pain, and save costs.

Most of the variation in length of stay in emergency general surgery is not related to clinical factors of patient care

BACKGROUND

Hospital length of stay (LOS) is currently recognized as a key quality indicator. We sought to investigate how much of the LOS variation in the high-risk group of patients undergoing Emergency general surgery could be explained by clinical versus nonclinical factors.

METHODS

Using the 2007 to 2015 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, we included all patients who underwent an emergency appendectomy, cholecystectomy, colectomy, small intestine resection, enterolysis, or hernia repair. American College of Surgeons National Surgical Quality Improvement Program defines emergency surgery as one that is performed no later than 12 hours after admission or symptom onset. Using all the ACS-NSQIP demographic, preoperative (comorbidities, laboratory variables), intraoperative (e.g., duration of surgery, wound classification), and postoperative variables (i.e., complications), we created multivariable linear regression models to predict LOS. LOS was treated as a continuous variable, and the degree to which the models could explain the variation in LOS for each type of surgery was measured using the coefficient of determination (R).

RESULTS

A total of 215,724 patients were included. The mean age was 47.1 years; 52.0% were female. In summary, the median LOS ranged between 1 day for appendectomies (n = 124, 426) and cholecystectomies (n = 21,699) and 8 days for colectomies (n = 19,557) and small intestine resections (n = 7,782). The R for all clinical factors ranged between 0.28 for cholecystectomy and 0.44 for hernia repair, suggesting that 56% to 72% of the LOS variation for each of the six procedures studied cannot be explained by the wide range of clinical factors included in ACS-NSQIP.

CONCLUSION

Most of the LOS variation is not explained by clinical factors and may be explained by nonclinical factors (e.g., logistical delays, insurance type). Further studies should evaluate these nonclinical factors to identify target areas for quality improvement.

LEVELS OF EVIDENCE

Epidemiological study, level III.

Reporting Methodology of Neurosurgical Studies Utilizing the American College of Surgeons-National Surgical Quality Improvement Program Database: A Systematic Review and Critical Appraisal

BACKGROUND

Use of large databases such as the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) has become increasingly common in neurosurgical research.

OBJECTIVE

To perform a critical appraisal and evaluation of the methodological reporting for studies in neurosurgical literature that utilize the ACS-NSQIP database.

METHODS

We queried Ovid MEDLINE, EMBASE, and PubMed databases for all neurosurgical studies utilizing the ACS-NSQIP. We assessed each study according to number of criteria fulfilled with respect to Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement, REporting of studies Conducted using Observational Routinely-collected Health Data (RECORD) Statement, and Journal of American Medical Association–Surgical Section (JAMA-Surgery) Checklist. A separate analysis was conducted among papers published in core and noncore journals in neurosurgery according to Bradford's law.

RESULTS

A total of 117 studies were included. Median (interquartile range [IQR]) scores for number of fulfilled criteria for STROBE Statement, RECORD Statement, and JAMA-Surgery Checklist were 20 (IQR:19-21), 9 (IQR:8-9), and 6 (IQR:5-6), respectively. For STROBE Statement, RECORD Statement, and JAMA-Surgery Checklist, item 9 (potential sources of bias), item 13 (supplemental information), and item 9 (missing data/sensitivity analysis) had the highest number of studies with no fulfillment among all studies (56, 68, 50%), respectively. When comparing core journals vs noncore journals, no significant difference was found (STROBE, P = .94; RECORD, P = .24; JAMA-Surgery checklist, P = .60).

CONCLUSION

While we observed an overall satisfactory reporting of methodology, most studies lacked mention of potential sources of bias, data cleaning methods, supplemental information, and external validity. Given the pervasive role of national databases and registries for research and health care policy, the surgical community needs to ensure the credibility and quality of such studies that ultimately aim to improve the value of surgical care delivery to patients.

Characterization of antimicrobial prescription frequency and diversity in a large animal veterinary medical teaching hospital

Antimicrobials are commonly used in veterinary medicine for therapeutic and prophylactic purposes, but little is known about the frequency with which they are prescribed or the quantity administered, especially in large animals. Furthermore, there are no standardized metrics for characterizing antimicrobial use, which can lead to confusion when comparing antimicrobial use among different units (institution, clinical service, clinician). Because there is no gold standard metric, the most comprehensive characterization of antimicrobial use will be achieved using a variety of metrics. The goal of this study was to characterize antimicrobial use from 2013 to 2018 at a tertiary care teaching hospital for large animals using different metrics, including novel ones. We found that at least one antimicrobial was prescribed in 42% of visits and that antimicrobials were prescribed at a rate of 919 animal-defined daily doses (ADDs) per 1000 animal days. A median of 3.6 ADDs and a mean of 2 different classes of antimicrobial were prescribed per patient, and penicillin was the most commonly used antimicrobial. The prescription diversity, a metric accounting for richness and evenness (similarity of frequencies) of different types of antimicrobials, was 0.82, with 1.0 representing maximal richness and diversity. Antimicrobial use differed significantly by species and by organ system affected for all metrics, though in general antimicrobials were prescribed most frequently and with the largest amounts in animals presenting with integumentary or respiratory signs. Many of our findings were consistent with those of other studies examining antimicrobial use in the species represented in our patient population, but more research is needed to determine how to best characterize antimicrobial use and assess appropriateness of prescribing.