Nicholas S. Golinvaux

Variations in Data Collection Methods Between National Databases Affect Study Results: A Comparison of the Nationwide Inpatient Sample and National Surgical Quality Improvement Program Databases for Lumbar Spine Fusion Procedures

BACKGROUND There has been an increasing use of national databases to conduct orthopaedic research. Questions regarding the validity and consistency of these studies have not been fully addressed. The purpose of this study was to test for similarity in reported measures between two national databases commonly used for orthopaedic research. METHODS A retrospective cohort study of patients undergoing lumbar spinal fusion procedures during 2009 to 2011 was performed in two national databases: the Nationwide Inpatient Sample and the National Surgical Quality Improvement Program. Demographic characteristics, comorbidities, and inpatient adverse events were directly compared between databases. RESULTS The total numbers of patients included were 144,098 from the Nationwide Inpatient Sample and 8434 from the National Surgical Quality Improvement Program. There were only small differences in demographic characteristics between the two databases. There were large differences between databases in the rates at which specific comorbidities were documented. Non-morbid obesity was documented at rates of 9.33% in the Nationwide Inpatient Sample and 36.93% in the National Surgical Quality Improvement Program (relative risk, 0.25; p < 0.05). Peripheral vascular disease was documented at rates of 2.35% in the Nationwide Inpatient Sample and 0.60% in the National Surgical Quality Improvement Program (relative risk, 3.89; p < 0.05). Similarly, there were large differences between databases in the rates at which specific inpatient adverse events were documented. Sepsis was documented at rates of 0.38% in the Nationwide Inpatient Sample and 0.81% in the National Surgical Quality Improvement Program (relative risk, 0.47; p < 0.05). Acute kidney injury was documented at rates of 1.79% in the Nationwide Inpatient Sample and 0.21% in the National Surgical Quality Improvement Program (relative risk, 8.54; p < 0.05). CONCLUSIONS As database studies become more prevalent in orthopaedic surgery, authors, reviewers, and readers should view these studies with caution. This study shows that two commonly used databases can identify demographically similar patients undergoing a common orthopaedic procedure; however, the databases document markedly different rates of comorbidities and inpatient adverse events. The differences are likely the result of the very different mechanisms through which the databases collect their comorbidity and adverse event data. Findings highlight concerns regarding the validity of orthopaedic database research.

Nationwide Inpatient Sample and National Surgical Quality Improvement Program Give Different Results in Hip Fracture Studies

BackgroundNational databases are being used with increasing frequency to conduct orthopaedic research. However, there are important differences in these databases, which could result in different answers to similar questions; this important potential limitation pertaining to database research in orthopaedic surgery has not been adequately explored.Questions/purposesThe purpose of this study was to explore the interdatabase reliability of two commonly used national databases, the Nationwide Inpatient Sample (NIS) and the National Surgical Quality Improvement Program (NSQIP), in terms of (1) demographics; (2) comorbidities; and (3) adverse events. In addition, using the NSQIP database, we identified (4) adverse events that had a higher prevalence after rather than before discharge, which has important implications for interpretation of studies conducted in the NIS.MethodsA retrospective cohort study of patients undergoing operative stabilization of transcervical and intertrochanteric hip fractures during 2009 to 2011 was performed in the NIS and NSQIP. Totals of 122,712 and 5021 patients were included from the NIS and NSQIP, respectively. Age, sex, fracture type, and lengths of stay were compared. Comorbidities common to both databases were compared in terms of more or less than twofold difference between the two databases. Similar comparisons were made for adverse events. Finally, adverse events that had a greater postdischarge prevalence were identified from the NSQIP database. Tests for statistical difference were thought to be of little value given the large sample size and the resulting fact that statistical differences would have been identified even for small, clinically inconsequential differences resulting from the associated high power. Because it is of greater clinical importance to focus on the magnitude of differences, the databases were compared by absolute differences.ResultsDemographics and hospital lengths of stay were not different between the two databases. In terms of comorbidities, the prevalences of nonmorbid obesity, coagulopathy, and anemia in found in the NSQIP were more than twice those in the NIS; the prevalence of peripheral vascular disease in the NIS was more than twice that in the NSQIP. Four other comorbidities had prevalences that were not different between the two databases. In terms of inpatient adverse events, the frequencies of acute kidney injury and urinary tract infection in the NIS were more than twice those in the NSQIP. Ten other inpatient adverse events had frequencies that were not different between the two databases. Because it does not collect data after patient discharge, it can be implied from the NSQIP data that the NIS does not capture more than ½ of the deaths and surgical site infections occurring during the first 30 postoperative days.ConclusionsThis study shows that two databases commonly used in orthopaedic research can identify similar populations of operative patients but may generate very different results for specific commonly studied comorbidities and adverse events. The NSQIP identified higher rates of morbid obesity, coagulopathy, and anemia. The NIS identified higher rates of peripheral vascular disease, acute kidney injury, and urinary tract infection.Level of EvidenceLevel II, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.

General Compared with Spinal Anesthesia for Total Hip Arthroplasty

BACKGROUND Total hip arthroplasty may be performed under general or spinal anesthesia. The purpose of the current study was to compare perioperative outcomes between anesthetic types for patients undergoing primary elective total hip arthroplasty. METHODS Patients who had undergone primary elective total hip arthroplasty from 2010 to 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program database. Operating room times, length of stay, thirty-day adverse events, and readmission were compared between patients who had received general anesthesia and those who had received spinal anesthesia. Propensity-adjusted multivariate analysis was used to control for selection bias and baseline patient characteristics. RESULTS A total of 20,936 patients who had undergone total hip arthroplasty met inclusion criteria for this study. Of these, 12,752 patients (60.9%) had received general anesthesia and 8184 patients (39.1%) had received spinal anesthesia. On propensity-adjusted multivariate analyses, general anesthesia for total hip arthroplasty was associated with increased operative time (+12 minutes [95% confidence interval, +11 to +13 minutes]; p < 0.001) and postoperative room time (+5 minutes [95% confidence interval, +4 to +6 minutes]; p < 0.001). General anesthesia was also associated with the occurrence of any adverse event (odds ratio, 1.31 [95% confidence interval, 1.23 to 1.41]; p < 0.001), prolonged postoperative ventilator use (odds ratio, 5.81 [95% confidence interval, 1.35 to 25.06]; p = 0.018), unplanned intubation (odds ratio, 2.17 [95% confidence interval, 1.11 to 4.29]; p = 0.024), stroke (odds ratio, 2.51 [95% confidence interval, 1.02 to 6.20]; p = 0.046), cardiac arrest (odds ratio, 5.04 [95% confidence interval, 1.15 to 22.07]; p = 0.032), any minor adverse event (odds ratio, 1.35 [95% confidence interval, 1.25 to 1.45]; p = 0.001), and blood transfusion (odds ratio, 1.34 [95% confidence interval, 1.25 to 1.45]; p < 0.001). General anesthesia was not associated with any difference in preoperative room time, postoperative length of stay, or readmission. CONCLUSIONS General anesthesia was associated with an increased rate of adverse events and mildly increased operating room times.

Using the ACS-NSQIP to identify factors affecting hospital length of stay after elective posterior lumbar fusion.

Study Design. Retrospective cohort study of the American College of Surgeons National Surgical Quality Improvement Program database from 2005 to 2010 that included 1861 patients who had undergone elective posterior lumbar fusion. Objective. To characterize factors that were independently associated with increased hospital length of stay (LOS) in patients who had undergone elective posterior lumbar fusion. Summary of Background Data. Posterior lumbar spine fusion is a common surgical procedure used to treat lumbar spine pathology. LOS is an important clinical variable and a major determinant of inpatient hospital costs. There is lack of studies in the literature using multivariate analysis to examine specifically the predictors of LOS after elective posterior lumbar fusion. Methods. Patients who underwent elective posterior lumbar fusion from 2005 to 2010 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Preoperative and intraoperative variables were extracted for each case and a multivariate linear regression was performed to assess the contribution of each variable to LOS. Results. A total of 1861 patients who had undergone elective posterior lumbar fusion were identified. The average age for patients in this cohort was 60.6 ± 13.9 years (mean ± standard deviation) with a body mass index of 30.3 ± 6.2 kg/m2. Of the total patients, 44.7% of patients were male. LOS was in the range from 0 days to 51 days. Multivariate linear regression identified age (P < 0.001), morbid obesity (body mass index ≥ 40 kg/m2, P < 0.001), American Society of Anesthesiologists class (P = 0.001), operative time (P < 0.001), multilevel procedure (P = 0.001), and intraoperative transfusion (P < 0.001) as significant predictors of extended LOS. Conclusion. The identified preoperative and intraoperative variables associated with extended LOS after elective posterior lumbar fusion may be helpful to clinicians for patient counseling and postoperative planning. Level of Evidence: 3

Postoperative length of stay and 30-day readmission after geriatric hip fracture: an analysis of 8434 patients.

Objectives: To identify factors associated with increased postoperative length of stay (LOS) and readmission after surgical repair of geriatric hip fractures. Methods: Patients aged 70 years and older who underwent hip fracture surgery from January 2011 through December 2012 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patient characteristics were tested for association with postoperative LOS and readmission using bivariate and multivariate analyses. Results: For the 8434 patients with hip fracture identified, the average age was 83.8 ± 5.9 years (mean ± SD), and 26.9% were male. Average postoperative LOS was 5.6 ± 6.0 days. Ten percent were readmitted within the first 30 postoperative days. Increased postoperative LOS of at least 1 full day was associated with increased time from admission to surgery, non–general anesthesia, and procedure type on multivariate analysis. Readmission was associated with increased age, male sex, body mass index ≥35 kg/m2, American Society of Anesthesiologists class ≥3, pulmonary disease, hypertension, steroid use, dependent functional status, and discharge to a facility on multivariate analysis. Conclusions: Ten percent of patients were readmitted after hip fracture repair in this national sample. Preoperative time to surgery, anesthesia type, and implant selection are 3 risk factors for increased LOS that can potentially be modified. A clinically significant risk factor for readmission was body mass index ≥35 kg/m2, which was not associated with increased postoperative LOS. The identified risk factors illuminate opportunities for optimizing care for hip fracture patients aged 70 and older. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Patient characteristics associated with increased postoperative length of stay and readmission after elective laminectomy for lumbar spinal stenosis.

Study Design. Retrospective cohort. Objective. To identify factors that were independently associated with increased postoperative length of stay (LOS) and readmission in patients who underwent elective laminectomy for lumbar spinal stenosis. Summary of Background Data. Lumbar spinal stenosis is a common pathology that is traditionally treated with decompressive laminectomy. Risk factors associated with increased LOS and readmission have not been fully characterized for laminectomy. Methods. Patients who underwent laminectomy for lumbar spinal stenosis during 2011 and 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program database. Patient characteristics were tested for association with LOS and readmission using bivariate and multivariate analyses. Patients with LOS more than 10 days were excluded from the readmission analysis as the American College of Surgeons National Surgical Quality Improvement Program only captures readmissions within 30 postoperative days, and the window for potential readmission was deemed too short for patients staying longer than 10 days. Results. A total of 2358 patients who underwent laminectomy met inclusion criteria. The average age was 66.4 ± 11.7 years (mean ± standard deviation). Average postoperative LOS was 2.1 ± 2.6 days. Of those meeting criteria for readmission analysis, 3.7% of patients (86 of 2339) were readmitted within 30 days postoperatively. Independent risk factors for prolonged LOS were increased age (P < 0.001), increased body mass index (P = 0.004), American Society of Anesthesiologists class 3–4 (P = 0.005), and preoperative hematocrit less than 36.0 (P = 0.001). Independent risk factors for readmission were increased age (P = 0.013), increased body mass index (P = 0.040), American Society of Anesthesiologists class 3–4 (P < 0.001), and steroid use (P = 0.001). The most common reason for readmission was surgical site-related infections (25.0% of patients readmitted in 2012). Conclusion. The identified factors associated with LOS and readmission after lumbar laminectomy may be useful for optimizing patient care. Level of Evidence: 3

Administrative database concerns: accuracy of International Classification of Diseases, Ninth Revision coding is poor for preoperative anemia in patients undergoing spinal fusion.

Study Design. Cross-sectional study. Objective. To objectively evaluate the ability of International Classification of Diseases, Ninth Revision (ICD-9) codes, which are used as the foundation for administratively coded national databases, to identify preoperative anemia in patients undergoing spinal fusion. Summary of Background Data. National database research in spine surgery continues to rise. However, the validity of studies based on administratively coded data, such as the Nationwide Inpatient Sample, are dependent on the accuracy of ICD-9 coding. Such coding has previously been found to have poor sensitivity to conditions such as obesity and infection. Methods. A cross-sectional study was performed at an academic medical center. Hospital-reported anemia ICD-9 codes (those used for administratively coded databases) were directly compared with the chart-documented preoperative hematocrits (true laboratory values). A patient was deemed to have preoperative anemia if the preoperative hematocrit was less than the lower end of the normal range (36.0% for females and 41.0% for males). Results. The study included 260 patients. Of these, 37 patients (14.2%) were anemic; however, only 10 patients (3.8%) received an “anemia” ICD-9 code. Of the 10 patients coded as anemic, 7 were anemic by definition, whereas 3 were not, and thus were miscoded. This equates to an ICD-9 code sensitivity of 0.19, with a specificity of 0.99, and positive and negative predictive values of 0.70 and 0.88, respectively. Conclusion. This study uses preoperative anemia to demonstrate the potential inaccuracies of ICD-9 coding. These results have implications for publications using databases that are compiled from ICD-9 coding data. Furthermore, the findings of the current investigation raise concerns regarding the accuracy of additional comorbidities. Although administrative databases are powerful resources that provide large sample sizes, it is crucial that we further consider the quality of the data source relative to its intended purpose. Level of Evidence: 3

Complication rates following elective lumbar fusion in patients with diabetes: insulin dependence makes the difference.

Study Design. Retrospective cohort. Objective. To determine the effect of non–insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) on postoperative complications after elective lumbar fusion surgery. Summary of Background Data. Diabetes mellitus (DM) is a common chronic disease. The effects of NIDDM and IDDM on rates of postoperative complications, extended length of stay, and readmission after lumbar fusion surgery are not well established. Methods. A retrospective cohort study was conducted using the American College of Surgeons National Surgical Quality Improvement Program database. Patients undergoing lumbar fusion between 2005 and 2012 were identified and characterized as having NIDDM, IDDM, or neither. Bivariate and multivariate analyses were used to test patients with NIDDM and IDDM for increased risk of adverse postoperative outcomes over the initial 30 postoperative days. Results. A total of 15,480 patients who underwent lumbar fusion were identified (13,043 were patients without DM, 1,650 patients had NIDDM, and 787 patients had IDDM). NIDDM was independently associated with an increased risk of wound dehiscence (relative risk = 2.3; P = 0.033) and extended length of stay (1.2; P < 0.003). IDDM was independently associated with an increased risk of death (2.7; P = 0.020), sepsis (2.2; P = 0.002), septic shock (3.3; P = 0.032), unplanned intubation (2.8; P = 0.003), ventilator-assisted respiration for more than 48 hours postoperatively (2.8; P = 0.005), wound-related infection (1.9; P = 0.001), urinary tract infection (1.6; P = 0.011), pneumonia (3.1; P < 0.001), extended length of stay (1.5; P < 0.001), and readmission within 30 days (1.5; P = 0.036). Conclusion. Compared with patients without DM, IDDM was associated with an increased risk of a considerably higher number of postoperative complications than NIDDM. These complications were also of greater severity. This important designation may improve preoperative risk stratification and counseling of patients with diabetes prior to lumbar fusion surgery. Level of Evidence: 3

General versus spinal anaesthesia for patients aged 70 years and older with a fracture of the hip

The aim of this study was to compare the operating time, length of stay (LOS), adverse events and rate of re-admission for elderly patients with a fracture of the hip treated using either general or spinal anaesthesia. Patients aged ≥ 70 years who underwent surgery for a fracture of the hip between 2010 and 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database. Of the 9842 patients who met the inclusion criteria, 7253 (73.7%) were treated with general anaesthesia and 2589 (26.3%) with spinal anaesthesia. On propensity-adjusted multivariate analysis, general anaesthesia was associated with slightly increased operating time (+5 minutes, 95% confidence interval (CI) +4 to +6, p < 0.001) and post-operative time in the operating room (+5 minutes, 95% CI +2 to +8, p < 0.001) compared with spinal anaesthesia. General anaesthesia was associated with a shorter LOS (hazard ratio (HR) 1.28, 95% CI 1.22 to 1.34, p < 0.001). Any adverse event (odds ratio (OR) 1.21, 95% CI 1.10 to 1.32, p < 0.001), thromboembolic events (OR 1.90, 95% CI 1.24 to 2.89, p = 0.003), any minor adverse event (OR 1.19, 95% CI 1.09 to 1.32, p < 0.001), and blood transfusion (OR 1.34, 95% CI 1.22 to 1.49, p < 0.001) were associated with general anaesthesia. General anaesthesia was associated with decreased rates of urinary tract infection (OR 0.73, 95% CI 0.62 to 0.87, p < 0.001). There was no clear overall advantage of one type of anaesthesia over the other, and surgeons should be aware of the specific risks and benefits associated with each type.

July effect in elective spine surgery: analysis of the American College of Surgeons National Surgical Quality Improvement Program database.

Study Design. Retrospective cohort. Objective. To evaluate for the presence and magnitude of the “July effect” within elective spine surgery. Summary of Background Data. The July effect is the hypothetical increase in morbidity and mortality thought to be associated with the influx of new (or newly promoted) trainees during the first portion of the academic year. Studies evaluating for the presence and magnitude of the July effect have demonstrated conflicting results. Methods. We accessed the American College of Surgeons National Surgical Quality Improvement Program database from 2005–2010. Statistical analyses were conducted using bivariate and multivariate logistic regression. Results. A total of 14,986 cases met inclusion criteria and constitute the study population. Of these, 26.5% occurred in the first academic quarter and 25.3% had resident involvement. The rate of serious adverse events was 1.9 times higher and the rate of any adverse events was 1.6 times higher among cases with resident involvement than among those without (P < 0.001 for both). Among cases without resident involvement, the rates of serious adverse events and any adverse events did not differ by academic quarter. Similarly, among cases with resident involvement, the rates of serious adverse events and any adverse events did not differ by academic quarter. Conclusion. We could not demonstrate that the training of new (or newly promoted) residents is associated with an increase in the adverse events of spine surgery. Safeguards that have been put in place to ensure patient safety during this training period seem to be effective. Although adverse events were more common among cases with resident involvement than among cases without resident involvement, our data suggest that this association is more likely a product of the riskier population of cases in which residents participate than of the resident involvement itself. Level of Evidence: 3