Ryan P. McLynn

Discriminative ability of commonly used indices to predict adverse outcomes after poster lumbar fusion: a comparison of demographics, ASA, the modified Charlson Comorbidity Index, and the modified Frailty Index

BACKGROUND CONTEXT As research tools, the American Society of Anesthesiologists (ASA) physical status classification system, the modified Charlson Comorbidity Index (mCCI), and the modified Frailty Index (mFI) have been associated with complications following spine procedures. However, with respect to clinical use for various adverse outcomes, no known study has compared the predictive performance of these indices specifically following posterior lumbar fusion (PLF). PURPOSE This study aimed to compare the discriminative ability of ASA, mCCI, and mFI, as well as demographic factors including age, body mass index, and gender for perioperative adverse outcomes following PLF. STUDY DESIGN/SETTING A retrospective review of prospectively collected data was performed. PATIENT SAMPLE Patients undergoing elective PLF with or without interbody fusion were extracted from the 2011-2014 American College of Surgeons National Surgical Quality Improvement Program (NSQIP). OUTCOME MEASURES Perioperative adverse outcome variables assessed included the occurrence of minor adverse events, severe adverse events, infectious adverse events, any adverse event, extended length of hospital stay, and discharge to higher-level care. METHODS Patient comorbidity indices and characteristics were delineated and assessed for discriminative ability in predicting perioperative adverse outcomes using an area under the curve analysis from the receiver operating characteristics curves. RESULTS In total, 16,495 patients were identified who met the inclusion criteria. The most predictive comorbidity index was ASA and demographic factor was age. Of these two factors, age had the larger discriminative ability for three out of the six adverse outcomes and ASA was the most predictive for one out of six adverse outcomes. A combination of the most predictive demographic factor and comorbidity index resulted in improvements in discriminative ability over the individual components for five of the six outcome variables. CONCLUSION For PLF, easily obtained patient ASA and age have overall similar or better discriminative abilities for perioperative adverse outcomes than numerically tabulated indices that have multiple inputs and are harder to implement in clinical practice.

Of 20,376 Lumbar Discectomies, 2.6% of Patients Readmitted within 30 Days: Surgical Site Infection, Pain, and Thromboembolic Events are the Most Common Reasons for Readmission.

Study Design. A retrospective cohort study of prospectively collected data. Objective. As an initial effort to address readmissions after lumbar discectomy, reasons for hospital readmission are identified and discussed. Summary of Background Data. Lumbar discectomy is a commonly performed procedure. The Affordable Care Act codifies penalties for hospital readmissions. New quality-based reimbursements tied to readmissions call for a better understanding of the causes of readmission after procedures such as lumbar discectomy. Methods. Lumbar discectomies performed in 2012 to 2014 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patient demographics, surgical variables, and reasons for readmissions within 30 days were recorded. Pearson chi square was used to compare rates of demographics and surgical variables between readmitted and nonreadmitted patients. Multivariate regression was used to identify risk factors for readmission. Results. Of 20,376 lumbar discectomies, 533 patients (2.62%) were readmitted within 30 days of surgery. The most common reasons for readmission were surgical site infections (n = 130, 0.64% of all discectomies, 24.4% of all readmissions), followed by pain issues (n = 89, 0.44%, 16.7%), and thromboembolic events (43, 0.21%, 8.1%). Overall time to readmission was 13.0 ± 8.0 days (mean ± standard deviation). Factors most associated with readmission after lumbar discectomy were higher American Society of Anesthesiologists class (relative risk = 1.49, P < 0.001) and prolonged operative time (relative risk = 1.41, P = 0.002). Conclusion. Surgical site infection, postoperative pain, and thromboembolic events were the most common reasons for readmission after lumbar discectomy. These findings identify potential areas for quality improvement initiatives. Level of Evidence: 3

Evaluating the effect of growing patient numbers and changing data elements in the National Surgical Quality Improvement Program (NSQIP) database over the years: a study of posterior lumbar fusion outcomes

BACKGROUND CONTEXT The use of national databases in spinal surgery outcomes research is increasing. A number of variables collected by the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) changed between 2010 and 2011, coinciding with a rapid increase in the number of patients included per year. However, there has been limited study evaluating the effect that these changes may have on the results of outcomes studies. PURPOSE The present study aimed to investigate the influence of changing data elements and growth of the NSQIP database on results of lumbar fusion outcomes studies. STUDY DESIGN/SETTING This is a retrospective cohort study of prospectively collected data. PATIENT SAMPLE The NSQIP database was retrospectively queried to identify 19,755 patients who underwent elective posterior lumbar fusion surgery with or without interbody fusion between 2005 and 2014. Patients were split into two groups based on year of surgery: 2,802 from 2005 to 2010 and 16,953 from 2011 to 2014. OUTCOME MEASURES The occurrence of adverse events after discharge from the hospital, within postoperative day 30, was determined. METHODS Preoperative characteristics and 30-day perioperative outcomes were compared between the era groups using bivariate analysis. To illustrate the effect of such changing data elements, the association between age and postoperative outcomes in the era groups was analyzed using multivariate Poisson regression. The present study had no funding sources, and there were no study-related conflicts of interest for any authors. RESULTS There were significant differences between the era groups for a variety of preoperative characteristics. Postoperative events such blood transfusion and deep vein thrombosis were also significantly different between the era groups. For the 2005-2010 cohort, age was significantly associated with septic shock by multivariate analysis. For the 2011-2014 cohort, age was significantly associated with septic shock, urinary tract infection, blood transfusion, myocardial infarction, and extended length of stay. CONCLUSIONS The NSQIP database has undergone substantial changes between 2005 and 2014. These changes may contribute to different results in analyses, such as the association between age and postoperative outcomes, when using older versus newer data. Conclusions from early studies using this database may warrant reconsideration.

Dialysis is an independent risk factor for perioperative adverse events, readmission, reoperation, and mortality for patients undergoing elective spine surgery

BACKGROUND CONTEXT The prevalence of dialysis-dependent patients in the United States is growing. Prior studies evaluating the risk of perioperative adverse events for dialysis-dependent patients are either institutional cohort studies limited by patient numbers or administrative database studies limited to inpatient data. PURPOSE The present study uses a large, national sample with 30-day follow-up to investigate dialysis as risk factor for perioperative complications independent of patient demographics or comorbidities. STUDY DESIGN/SETTING This is a retrospective cohort study. PATIENT SAMPLE Patients undergoing elective spine surgery with or without dialysis from the 2005-2015 National Surgical Quality Improvement Program (NSQIP) database were included in the study. OUTCOME MEASURES Postoperative complications within 30 days and binomial reoperation, readmission, and mortality within 30 days were determined. METHODS The 2005-2015 NSQIP databases were queried for adult dialysis-dependent and dialysis-independent patients undergoing elective spinal surgery. Differences in 30-day outcomes were compared using risk-adjusted multivariate regression and coarsened exact matching analysis for adverse events, unplanned readmission, reoperation, and mortality. The percentage of complications occurring before versus after hospital discharge was also assessed. The authors have no financial disclosures related to the present study. RESULTS A total of 467 dialysis and 173,311 non-dialysis patients met the inclusion criteria. Controlling for age, gender, body mass index, functional status, and American Society of Anesthesiologists (ASA) class, dialysis patients were found to be at significantly greater odds of any adverse event (odds ratio [OR]=2.52 before, 2.17 after matching, p=<.001), major adverse event (OR=2.90 before, 2.52 after matching, p=<.001), and minor adverse event (OR=1.50 before matching, p=<.025, but not significantly different after matching). Further, dialysis patients were significantly more likely to return to the operating room (OR=2.77 before, 2.50 after matching, p=<.001), have unplanned readmissions (OR=2.73 before, 2.37 after matching, p=<.001), and die within 30 days (OR=3.77 before, 2.71 after matching, p=<.001). Adverse events occurred after discharge for 51.78% of non-dialysis patients and for 43.80% of dialysis patients. CONCLUSIONS Dialysis patients undergoing elective spine surgery are at significantly higher risk of aggregated adverse outcomes, return to the operating room, readmission, and death than non-dialysis patients, even after controlling for patient demographics and overall health (as indicated by ASA class). These differences need to be considered when determining treatment options. Additionally, with bundled payments expected in spine surgery, physicians and hospitals need to account for increased costs and liabilities when working with dialysis patients.

Missing data treatments matter: an analysis of multiple imputation for anterior cervical discectomy and fusion procedures

BACKGROUND CONTEXT The presence of missing data is a limitation of large datasets, including the National Surgical Quality Improvement Program (NSQIP). In addressing this issue, most studies use complete case analysis, which excludes cases with missing data, thus potentially introducing selection bias. Multiple imputation, a statistically rigorous approach that approximates missing data and preserves sample size, may be an improvement over complete case analysis. PURPOSE The present study aims to evaluate the impact of using multiple imputation in comparison with complete case analysis for assessing the associations between preoperative laboratory values and adverse outcomes following anterior cervical discectomy and fusion (ACDF) procedures. STUDY DESIGN/SETTING This is a retrospective review of prospectively collected data. PATIENT SAMPLE Patients undergoing one-level ACDF were identified in NSQIP 2012-2015. OUTCOME MEASURES Perioperative adverse outcome variables assessed included the occurrence of any adverse event, severe adverse events, and hospital readmission. METHODS Missing preoperative albumin and hematocrit values were handled using complete case analysis and multiple imputation. These preoperative laboratory levels were then tested for associations with 30-day postoperative outcomes using logistic regression. RESULTS A total of 11,999 patients were included. Of this cohort, 63.5% of patients had missing preoperative albumin and 9.9% had missing preoperative hematocrit. When using complete case analysis, only 4,311 patients were studied. The removed patients were significantly younger, healthier, of a common body mass index, and male. Logistic regression analysis failed to identify either preoperative hypoalbuminemia or preoperative anemia as significantly associated with adverse outcomes. When employing multiple imputation, all 11,999 patients were included. Preoperative hypoalbuminemia was significantly associated with the occurrence of any adverse event and severe adverse events. Preoperative anemia was significantly associated with the occurrence of any adverse event, severe adverse events, and hospital readmission. CONCLUSIONS Multiple imputation is a rigorous statistical procedure that is being increasingly used to address missing values in large datasets. Using this technique for ACDF avoided the loss of cases that may have affected the representativeness and power of the study and led to different results than complete case analysis. Multiple imputation should be considered for future spine studies.

Incidence and Considerations of 90 day Readmissions following Posterior Lumbar Fusion

BACKGROUND CONTEXT Posterior lumbar fusion (PLF) is a commonly performed procedure. The evolution of bundled payment plans is beginning to require physicians to more closely consider patient outcomes up to 90 days after an operation. Current quality metrics and other databases often consider only 30 postoperative days. The relatively new Healthcare Cost and Utilization Project Nationwide Readmissions Database (HCUP-NRD) tracks patient-linked hospital admissions data for up to one calendar year. PURPOSE To identify readmission rates within 90 days of discharge following PLF and to put this in context of 30 day readmission and baseline readmission rates. STUDY DESIGN Retrospective study of patients in the HCUP-NRD. PATIENT SAMPLE Any patient undergoing PLF performed in the first 9 months of 2013 were identified in the HCUP-NRD. OUTCOME MEASURES Readmission patterns up to a full calendar year after discharge. METHODS PLFs performed in the first 9 months of 2013 were identified in the HCUP-NRD. Patient demographics and readmissions were tracked for 90 days after discharge. To estimate the average admission rate in an untreated population, the average daily admission rate in the last quarter of the year was calculated for a subset of PLF patients who had their operation in the first quarter of the year. This study was deemed exempt by the institutions Human Investigation Committee. RESULTS Of 26,727 PLFs, 1,580 patients (5.91%) were readmitted within 30 days of discharge and 2,603 patients (9.74%) were readmitted within 90 days of discharge. Of all readmissions within 90 days, 54.56% occurred in the first 30 days. However, if only counting readmissions above the baseline admission rate of a matched population from the 4th quarter of the year (0.08% of population/day), 89.78% of 90 day readmissions occurred within the first 30 days. CONCLUSIONS The current study delineates readmission rates after PLF and puts this in the context of 30-day readmission rates and baseline readmission rates for those undergoing PLF. These results are important for patient counseling, planning, and preparing for potential bundled payments in spine surgery.

Total Disc Arthroplasty Versus Anterior Interbody Fusion in the Lumbar Spine Have Relatively a Few Differences in Readmission and Short-term Adverse Events

Study Design. Retrospective matched cohort study of prospectively collected data. Objective. To compare rates of adverse events and readmission between lumbar total disc arthroplasty (TDA) and anterior lumbar interbody fusion (ALIF) using the American College of Surgeons National Surgical Quality Improvement Program database. Summary of Background Data. TDA and ALIF may be considered for similar degenerative indications. However, there have been a few large-cohort comparison studies of short-term clinical outcomes for these procedures. Methods. The 2011−2015 NSQIP databases were retrospectively queried to identify patients who underwent elective stand-alone ALIF and TDA. After propensity matching, the association of procedure type with adverse events and readmission was determined using McNemars test. Operative time and postoperative length of stay (LOS) were compared using multivariate linear regression. Risk factors for adverse events were determined using multivariate Poisson regression. Results. In total, 1801 ALIF and 255 TDA patients were identified. After matching with propensity scores, there were no significant differences in the rates of any adverse event, serious adverse events, individual adverse events, or readmission other than blood transfusion, which occurred more frequently in the ALIF cohort (3.92% vs. 0.39%, P = 0.007). Operative time was not significantly different between the two cohorts, but postoperative LOS was significantly longer for ALIF cases (+0.28 days, P < 0.001). When evaluating 10 preoperative variables as potential risk factors for adverse events and readmission after TDA and ALIF, the majority of results were similar. Conclusion. The only identified differences in perioperative outcomes between TDA and ALIF were a 3.53% higher incidence of blood transfusion and 0.28-day longer LOS for the ALIF group. These results suggest overall similar short-term general-health outcomes between the two groups, and that the choice between the two procedures, for the appropriately selected patient, should be based on longer-term functional outcomes. Level of Evidence: 3

Longer Operative Time Is Associated With Increased Adverse Events After Anterior Cervical Diskectomy and Fusion: 15-Minute Intervals Matter

Little is known about the impact of operative time, as an independent and interval variable, on general health perioperative outcomes following anterior cervical diskectomy and fusion. Therefore, patients undergoing a 1-level anterior cervical diskectomy and fusion were identified in the American College of Surgeons National Surgical Quality Improvement Program. Operative time (as an interval variable) was tested for association with perioperative outcomes using a multivariate regression that was adjusted for differences in baseline characteristics. A total of 15,241 patients were included. Increased surgical duration was consistently correlated with a rise in any adverse event postoperatively, with each additional 15 minutes of operating time raising the risk for having any adverse event by an average of 10% (99.64% confidence interval, 3%-17%, P<.001). In fact, 15-minute increases in surgical duration were associated with incremental increases in the rates of venous thromboembolism, sepsis, unplanned intubation, extended length of hospital stay, and hospital readmission. Greater operative time, despite controlling for other patient variables, increases the risk for overall postoperative adverse events and multiple individual adverse outcomes. This increased risk may be attributed to anesthetic effects, physiologic stresses, and surgical site issues. Although it is difficult to fully isolate operative time as an independent variable because it may be closely related to the complexity of the surgical pathology being addressed, the current study suggests that surgeons should maximize operative efficiency as possible (potentially using strategies that have been shown to improve operative time in the 15-minute magnitude), without compromising the technical components of the procedure. [Orthopedics. 2018; 41(4):e483-e488.].

General Health Adverse Events Within 30 Days Following Anterior Cervical Discectomy and Fusion in US Patients: A Comparison of Spine Surgeons’ Perceptions and Reported Data for Rates and Risk Factors

Study Design: Survey study and retrospective review of prospective data. Objectives: To contrast surgeons’ perceptions and reported national data regarding the rates of postoperative adverse events following anterior cervical discectomy and fusion (ACDF) and to assess the accuracy of surgeons in predicting the impact of patient factors on such outcomes. Methods: A survey investigating perceived rates of perioperative complications and the perceived effect of patient risk factors on the occurrence of complications following ACDF was distributed to spine surgeons at the Cervical Spine Research Society (CSRS) 2015 Annual Meeting. The equivalent reported rates of adverse events and impacts of patient risk factors on such complications were assessed in patients undergoing elective ACDF from the National Surgical Quality Improvement Program (NSQIP). Results: There were 110 completed surveys from attending physicians at CSRS (response rate = 44%). There were 18 019 patients who met inclusion criteria in NSQIP years 2011 to 2014. The rates of 11 out of 17 (65%) postoperative adverse events were mildly overestimated by surgeons responding to the CSRS questionnaire in comparison to reported NSQIP data (overestimates ranged from 0.24% to 1.50%). The rates of 2 out of 17 (12%) postoperative adverse events were mildly underestimated by surgeons (range = 0.08% to 1.2%). The impacts of 5 out of 10 (50%) patient factors were overestimated by surgeons (range relative risk = 0.56 to 1.48). Conclusions: Surgeon estimates of risk factors for and rates of adverse events following ACDF procedures were reasonably nearer to national data. Despite an overall tendency toward overestimation, surgeons’ assessments are roughly appropriate for surgical planning, expectation setting, and quality improvement initiatives.

The Rothman Index Is Associated With Postdischarge Adverse Events After Hip Fracture Surgery in Geriatric Patients

Background The Rothman Index is a comprehensive measure of overall patient status in the inpatient setting already in use at many medical centers. It ranges from 100 (best score) to -91 (worst score) and is calculated based on 26 variables encompassing vital signs, routine laboratory values, and organ system assessments from nursing rounds from the electronic medical record. Past research has shown an association of Rothman Index with complications, readmission, and death in certain populations, but it has not been evaluated in geriatric patients with hip fractures, a potentially vulnerable patient population. Questions/purposes (1) Is there an association between Rothman Index scores and postdischarge adverse events in a population aged 65 years and older with hip fractures? (2) What is the discriminative ability of Rothman Index scores in determining which patients will or will not experience these adverse events? (3) Are there Rothman Index thresholds associated with increased incidence of postdischarge adverse outcomes? Methods One thousand two hundred fourteen patients aged 65 years and older who underwent hip fracture surgery at an academic medical center between 2013 and 2016 were identified. Demographic and comorbidity characteristics were characterized, and 30-day postdischarge adverse events were calculated. The associations between a 10-unit change in Rothman Index scores and postdischarge adverse events, mortality, and readmission were determined. American Society of Anesthesiologists (ASA) class was used as a measure of comorbidity because prior research has shown its performance to be equivalent or superior to that of calculated comorbidity measures in this data set. We assessed the ability of Rothman Index scores to determine which patients experienced adverse events. Finally, Rothman Index thresholds were assessed for an association with increased incidence of postdischarge adverse outcomes. Results We found a strong association between Rothman Index scores and postdischarge adverse events (lowest score: odds ratio [OR] = 1.29 [1.18-1.41], p < 0.001; latest score: OR = 1.37 [1.24-1.52], p < 0.001) after controlling for age, sex, body mass index, ASA class, and surgical procedure performed. The discriminative ability of lowest and latest Rothman Index scores was better than those of age, sex, and ASA class for any adverse event (lowest value: area under the curve [AUC] = 0.641; 95% confidence interval [CI], 0.601-0.681; latest value: AUC = 0.640; 95% CI, 0.600-0.680); age (0.534; 95% CI, 0.493-0.575, p < 0.001 for both), male sex (0.552; 95% CI, 0.518-0.585, p = 0.001 for both), and ASA class (0.578; 95% CI, 0.542-0.614; p = 0.004 for lowest Rothman Index, p = 0.006 for latest Rothman Index). There was never a difference when comparing lowest Rothman Index value and latest Rothman Index value for any of the outcomes (Table 5). Patients experienced increased rates of postdischarge adverse events and mortality with a lowest Rothman Index of ⩽ 35 (p < 0.05) or latest Rothman Index of ⩽ 55 (p < 0.05). Conclusions The Rothman Index provides an objective method of assessing perioperative risk in the setting of hip fracture surgery in patients older than age 65 years and is more accurate than demographic measures or ASA class. Furthermore, there are Rothman Index thresholds that can be used to identify patients at increased risk of complications. Physicians can use this tool to monitor the condition of patients with hip fracture, recognize patients at high risk of adverse events to consider changing their plan of care, and counsel patients and families. Further investigation is needed to determine whether interventions based on Rothman Index values contribute to improved outcomes or value of hip fracture care. Level of Evidence Level II, diagnostic study.