MIS LD Research Articles

Predicting Acute Changes in Depressive Symptoms Following Lumbar Decompression.

While depressive symptoms improve for most patients following minimally invasive lumbar decompression (MIS LD), for some, symptoms may worsen. This study aimed to investigate predictors of change in depressive symptoms in the short-term postoperative period following MIS LD. We retrospectively analyzed a prospective surgical database for patients undergoing primary MIS LD procedures from 2016 to 2020. Preoperative pain (visual analog scale back and leg) scores were recorded, and the 9-Item Patient Health Questionnaire (PHQ-9) was administered at the preoperative and postoperative (6 weeks, 12 weeks, 6 months, and 1 year) timepoints. Patients were grouped into 1 of 3 categories of depression severity based on preoperative PHQ-9 scores: minimal (0-4), mild (5-9), and moderate to severe (10-27). Postoperative change in depressive symptoms was calculated by determining differences from baseline scores to scores at 6 weeks, 12 weeks, and 6 months. Analysis of demographics, perioperative characteristics, and spinal pathologies was conducted using χ 2 test. Significant factors contributing to postoperative changes in depression were analyzed using multiple linear regression analysis. Significance was set at P = 0.05. The 216 patients included had a mean age of 48 years, and a majority were men (70.4%). Most patients had a preoperative diagnosis of spinal stenosis (90.3%) or herniated nucleus pulposus (69.9%). Univariate analysis identified age, ethnicity, insurance, and diabetes as significant variables among depression severity groups. Patients demonstrated significant improvements in depressive symptoms at all postoperative timepoints (P < 0.001). Multivariate analysis identified several significant predictors of postoperative change in PHQ-9, which included moderate to severe preoperative depression for all postoperative timepoints (all P ≤ 0.038), mild preoperative depression for 6 weeks and 12 weeks (both P ≤ 0.029), and private insurance (P = 0.002) and smoking status (P = 0.047) at 12 weeks. Depression improved at all postoperative timepoints following LD. Insurance type, smoking status, and preoperative depression severity were all identified as significant predictors of postoperative changes in depressive symptoms. This study explores predictors of changes in depressive symptoms following LD.

Validation of VR-12 Physical Function in Minimally Invasive Lumbar Discectomy

Although the Veterans RAND 12-item Physical Component Survey (VR-12 PCS) has been broadly used to evaluate patient-reported outcome measures (PROMs) in spine surgery, its feasibility for use in patients undergoing minimally invasive lumbar discectomy (MIS LD) has not been well studied. This study aimed to assess the feasibility of VR-12 PCS for use up to 2 years postoperatively for MIS LD by correlation with PROMs for physical function. Patients undergoing primary single-level MIS LD procedures were reviewed retrospectively. Results on the VR-12 PCS, 12-Item Short Form (SF-12) PCS, and Patient-Reported Outcomes Measurement Information System (PROMIS PF) were recorded preoperatively and up to 2 years postoperatively. Improvements in postoperative PROMs were calculated and assessed for significant differences from baseline values. Correlation significance and strength were evaluated between VR-12 PCS and SF-12 PCS or PROMIS PF. Scatterplots were constructed to demonstrate relationships of VR-12 PCS with SF-12 PCS and PROMIS PF at each time point. Our cohort comprised 402 patients. Patients improved significantly from preoperative baseline for all 3 PROMs at all postoperative time points. Both Pearson's correlation and time-independent partial correlation revealed statistically significant strong correlations of VR-12 PCS with SF-12 PCS and PROMIS PF through 2-years. Physical function scores for VR-12, SF-12, and PROMIS PF all demonstrated significant improvements following MIS LD. Strongly statistically significant correlations of VR-12 PCS with SF-12 PCS and PROMIS PF from preoperative measures through 2 years demonstrate the feasibility of VR-12 for assessing patient-reported physical function in MIS LD patients.

219. Assessing PHQ-9 vs SF-12 mental composite score as predictors of postoperative outcomes

<h3>BACKGROUND CONTEXT</h3> A number of previous studies have demonstrated the significance of preoperative mental health scores, such as the Patient-Health Questionnaire-9 and the 12-Item Short Form Mental Composite Score (SF-12 MCS), as predictors of postoperative patient-reported outcome measures (PROMs) for physical health. However, these measures have not yet been compared as predictors of physical health outcomes following spine surgery. <h3>PURPOSE</h3> To assess the predictive value of PHQ-9 and SF-12 MCS in patients undergoing minimally invasive lumbar decompression (MIS LD). <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> This study included 416 patients undergoing primary, elective, single- or multilevel MIS LD procedures for degenerative spinal pathology. <h3>OUTCOME MEASURES</h3> Demographic and perioperative characteristics, Patient Health Questionnaire-9 (PHQ-9), Short Form 12 Mental Composite Score (SF-12 MCS), Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS PF), SF-12 Physical Composite Score (PCS), visual analog scale (VAS) back, VAS leg, and Oswestry Disability Index (ODI). <h3>METHODS</h3> A prospectively maintained surgical database was retrospectively reviewed for patients who underwent primary, elective, single- or multilevel MIS LD procedures for degenerative spinal pathology. Patient demographics, baseline characteristics, pre-existing spinal pathology, and perioperative outcomes were collected. PROMs including PHQ-9, SF-12 MCS, Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS PF), SF-12 Physical Composite Score (PCS), Visual analog scale (VAS) back, VAS leg, and Oswestry Disability Index (ODI) were administered preoperatively and at postoperative timepoints. Descriptive statistics were performed for baseline and perioperative variables. Paired Student's t-test was used to assess postoperative improvement in PROM scores from preoperative baseline. PHQ-9 and SF-12 MCS were assessed as predictors of postoperative scores in other PROMs using linear regression analysis at each timepoint. Post-hoc estimations were performed using standardized beta coefficients to compare PHQ-9 and SF-12 MCS as predictors of postoperative PROM scores. <h3>RESULTS</h3> A total of 416 MIS LD patients were included with a mean age of 45.7. A majority were male (69.0%), and non-obese (58.2%). Mean preoperative PHQ-9 and SF-12 MCS scores were 5.8 ± 5.5 and 48.8 ± 11.8, respectively. PROMIS PF, SF-12 PCS, VAS back, VAS leg, and ODI demonstrated significant improvements from preoperative baseline at all postoperative timepoints (all p<0.001). PHQ-9 was a significant predictor of PROMIS PF and SF-12 at preoperative, 6-week, 12-week, and 2-year timepoints (all p≤0.045), VAS back at all timepoints except 1-year (all p≤0.047), VAS leg at preoperative, 6-week, 12-week, and 1-year timepoints (all p≤0.021), and ODI from preoperative through 1-year timepoints (all p≤0.005). SF-12 MCS was a significant predictor of PROMIS PF at preoperative, 6-week, 12-week, and 2-year timepoints (all p≤0.016), SF-12 PCS at 6-week, 12-week, and 2-year timepoints (all p≤0.022), VAS back at preoperative, 12-week, and 6-month timepoints (all p≤0.017), and VAS leg and ODI at all timepoints except 2-years (all p≤0.025). Significant differences in effect size as predictor variables were demonstrated between PHQ-9 and SF-12 MCS at all timepoints except 6-months and 1-year for PROMIS PF and SF-12 PCS (all p≤0.027), 1-year for VAS back (all p≤0.015), and 2-years for VAS leg (all p≤0.014). <h3>CONCLUSIONS</h3> Both PHQ-9 and SF-12 MCS were demonstrated as significant predictors of physical function, pain, and disability PROMs at most timepoints. However, significant differences in the effect sizes of these predictive models were demonstrated. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

253. Mental health improvement predicts acute changes in physical health outcomes following minimally invasive lumbar decompression

<h3>BACKGROUND CONTEXT</h3> Previous studies have assessed the impact of preoperative depressive symptoms on postoperative outcomes with inconsistent results. However, the influence of postoperative improvement in depression has not been assessed in terms of other patient-reported outcomes. <h3>PURPOSE</h3> To assess the association between improvement in depressive symptoms and other postoperative outcomes following minimally invasive lumbar decompression (MIS LD). <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> A total of 193 patients undergoing primary, elective, single level MIS LD procedures. <h3>OUTCOME MEASURES</h3> Demographic and perioperative characteristics, Patient Health Questionnaire-9 (PHQ-9), Patient-Reported Outcomes Measurement Information System physical function (PROMIS PF), 12-Item Short Form Physical Composite Score (SF-12 PCS), Oswestry Disability Index (ODI), visual analog scale (VAS) back and VAS leg. <h3>METHODS</h3> Prospectively collected data were recorded in a private surgical database and reviewed for primary, elective, single level MIS LD procedures. Patients lacking pre- or postoperative PHQ-9 data or whose procedures were indicated due to infection, malignancy, or trauma were excluded. Descriptive statistics were performed for patient demographics, preoperative spinal pathology, and perioperative characteristics. Patient reported outcome measures (PROMs) were administered at preoperative and 6-week, 12-week, 6-month, 1-year and 2-year postoperative timepoints. PROMs included PHQ-9, PROMIS PF, SF-12 PCS, ODI, VAS back and VAS leg. Delta (Δ) scores were calculated for each PROM based on postoperative improvement from preoperative baseline values. Achievement of a minimum clinically important difference (MCID) was determined by comparing Δ scores to the following previously established threshold values: AS back (2.2), VAS leg (5.0), ODI (8.2), SF-12 PCS (2.5), PROMIS PF (4.5). Postoperative improvement in PROM scores from preoperative baseline was assessed using a paired Student's t-test. Correlation between ΔPHQ-9 and other ΔPROM scores was assessed using Pearson's correlation coefficient. Multivariate regression analysis was used to assess PHQ-9 MCID achievement as a predictor of MCID achievement for other PROMs. <h3>RESULTS</h3> A total of 193 patients met inclusion/exclusion criteria. The study cohort had a mean age of 44.0 years, 72.0% were male, and the mean body mass index was 29.5 kg/m2. Herniated nucleus pulposus was the most common preoperative spinal pathology (92.8%). Mean perioperative characteristics were as follows: operative duration 39.8 minutes, estimated blood loss 25.6 mL and postoperative length of stay 4.8 hours. All PROMs demonstrated significant postoperative improvement from preoperative baseline (p≤0.012), with the exception of PHQ-9 at 2-years (p=0.248). ΔPHQ-9 was significant correlated with ΔPROMIS at 12-weeks through 1-year (all p≤0.002), ΔSF-12 PCS at 6-weeks through 1-year (all p≤0.018), ODI from 6-weeks through 6-months (all p≤0.024), VAS back at 6-weeks and 2-years (both p≤0.033), and VAS leg at 6-weeks only (p=0.009). Multivariate analysis revealed PHQ-9 MCID achievement as a significant predictor of MCID achievement in other PROMs at 12-weeks (p=0.005), 6-months (p<0.001) and overall (p=0.002). <h3>CONCLUSIONS</h3> Improvement in depressive symptoms, as measured by PHQ-9, was significantly associated with improvement in other PROMs primarily at short-term and intermediate postoperative timepoints. Therefore, lessening of depressive symptoms may be a particularly pertinent factor for overall outcomes in the first few months following MIS LD procedures. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

The Influence of Sex on Clinical Outcomes in Minimally Invasive Lumbar Decompression.

Research focused on postoperative outcomes among men and women undergoing minimally invasive lumbar decompression (MIS LD) spine surgery is sparse. This study aims to assess the influence of sex on postoperative patient-reported outcome measure (PROM) evaluations and achievement of a minimum clinically important difference (MCID). A prospectively maintained surgical database was retrospectively queried for patients undergoing primary or revision, single or multilevel LD procedures from 2011 to 2019. Patients with incomplete visual analog scale (VAS) leg or back surveys were excluded. Demographic and operative variables were recorded, and a chi-squared analysis or t tests were used to compare by sex. PROMs were evaluated from preoperative to postoperative time points. PROM score differences and postoperative improvement were evaluated between sexes by a t test. Achievement of MCID by sex was compared using chi-squared analysis. The study cohort (n = 572) was 70% male (n = 398), had an average age of 47 years, and 42% were obese. Sexes differed in preoperative VAS leg, Oswestry Disability Index (ODI), and 12-item short form (SF-12)-physical composite score (PCS) scores (all P < .05) and in ODI at 6 and 12 weeks (P = .048; P = .001) and VAS back and leg scores at 6 months (P = .039; P = .019). Both sexes significantly improved (P < .050) all PROMs at all time points except for VAS back at 1 year for women and ODI at 6 weeks and 6 months for men. The only significant difference in achievement of MCID was for ODI at 6 months (P = .008). Significant preoperative differences were observed among sexes with ODI, SF-12-PCS, and VAS leg scores. By 1 year, there were no significant sex differences for any PROM or for achievement of MCID. MIS LD has an equivalent role for both sexes in achieving MCID. 3. Results demonstrate no sex difference in PROMs following LD.

Patient Health Questionnaire-9 Is a Valid Assessment for Depression in Minimally Invasive Lumbar Discectomy.

ObjectiveThe Patient Health Questionnaire-9 (PHQ-9) is a screening tool for evaluating depressive symptoms. Research is scarce regarding the validity and correlation of PHQ-9 scores with other patient-reported outcomes of mental health after minimally invasive lumbar discectomy (MIS LD). We aim to validate PHQ-9 as a metric for assessing mental health in MIS LD patients. MethodsA database was retrospectively reviewed for patients who underwent elective, single-level MIS LD. Patients were excluded if they had incomplete preoperative PHQ-9, 12-item Short Form Health Survey (SF-12), or Veterans RAND 12-item health survey (VR-12). Survey scores were collected preoperatively and postoperatively through 1 year. Mean scores were used to calculate postoperative improvement from preoperative scores. Correlation of PHQ-9 with SF-12 mental composite score (MCS) and VR-12 MCS scores was also calculated. Correlation strength was assessed by the following categories: 0.1 ≤ |r| < 0.3 = low; 0.3 ≤ |r| < 0.5 = moderate; |r| ≥ 0.5 = strong. ResultsA total of 239 patients underwent single-level MIS LD. PHQ-9, VR-12 MCS, and SF-12 MCS all demonstrated statistically significant increases from preoperative scores at all postoperative timepoints (p ≤ 0.001). SF-12 MCS and VR-12 MCS were each observed to have strong and significant correlations with PHQ-9 at all timepoints when evaluated with both Pearson correlation coefficients and partial correlation coefficients. ConclusionWe observed that PHQ-9, SF-12 MCS and VR-12 MCS all significantly improve following lumbar discectomy and that PHQ-9 scores strongly correlated with these previously established measures. Our results substantiate evidence from other surgical fields that PHQ-9 scores are a valid tool to evaluate pre- and postsurgical depressive symptoms.

Does day of surgery affect length of stay and hospital charges following lumbar decompression?

Study Design: This is a retrospective cohort study. Introduction: Spine procedures are the most expensive surgical interventions on a per-case basis. Previously, orthopedic procedures occurring later in the week have been associated with an increased length of stay (LOS) and consequent increase in costs. However, no such analysis has been performed on common spinal procedures such as minimally invasive lumbar decompression (MIS LD). The purpose of this study is to determine if there is an association between day of surgery and LOS or direct hospital costs after MIS LD. Materials and Methods: A prospectively maintained surgical database of patients who underwent primary, single, or multilevel MIS LD for degenerative spinal pathology between 2008 and 2017 was reviewed. Patients undergoing MIS LD were grouped as early in the week (Monday/Tuesday) or late in the week (Thursday/Friday). Differences in patient demographics and preoperative characteristics were compared using χ 2 analysis or Student’s t-test. Associations between date of surgery, LOS, and costs were assessed using multivariate linear regression. Results: A total of 717 patients were included. Of these, 420 (58.6%) were in the early surgery cohort and 297 (41.4%) were in the late surgery cohort. There were no differences in demographic characteristics, operative levels, operative time, blood loss, or hospital LOS between cohorts ( p &gt; 0.05). Furthermore, there was no difference in total direct costs or specific cost categories between cohorts ( p &gt; 0.05). Discussion: The timing of surgery within the week is not associated with differences in inpatient LOS or hospital costs following MIS LD. As such, hospitals should not alter surgical scheduling patterns to restrict these procedures to certain days within the week.

Preoperative patient activation is predictive of improvements in patient-reported outcomes following minimally invasive lumbar decompression.

To determine whether there is an association between preoperative 10-Item Patient Activation Measure (PAM-10) scores and clinical outcomes following MIS LD. Patients undergoing a primary MIS LD were retrospectively reviewed and stratified according to their preoperative PAM-10 scores: "low PAM," "moderate PAM," and "high PAM." Preoperative PAM score cohorts were tested for improvements in Oswestry Disability Index (ODI), 12-Item Short-Form Physical Component Score (SF-12 PCS), and Visual Analog Scale (VAS) back and leg pain using multivariate linear regression. Eighty-nine patients were included: 29 had a low PAM score, 32 had a moderate PAM score, and 28 had a high PAM score. Cohorts experienced similar preoperative VAS back pain, VAS leg pain, ODI, and SF-12 PCS. Patients with low PAM scores experienced a trend of higher pain scores throughout 6 months with VAS back pain being significant at 3 months and VAS leg pain being significant at 6-week and 3-month follow-up. Patients with lower PAM scores experienced a worse improvement in ODI at 6-week, 3-month, and 6-month timepoints. Lastly, patients with lower PAM scores demonstrated less improvement in SF-12 PCS at 3-month and 6-month follow-up. Lower preoperative PAM scores were associated with worse improvement in clinical outcomes following MIS LD. Patients with lower PAM scores had diminished improvement in long-term patient-reported outcomes including ODI, SF-12, and VAS back and leg pain. Our investigation suggests that preoperative PAM assessments may be an effective tool to predict postoperative outcomes following MIS LD.

Sex Differences on Postoperative Pain and Disability Following Minimally Invasive Lumbar Discectomy.

Retrospective cohort. To determine if sex is associated with differences in postoperative pain scores, narcotic consumption, and long-term improvements in pain and disability following minimally invasive lumbar discectomy (MIS LD). There exists a question as to what extent sex influences surgical and clinical outcomes following MIS LD. Patients undergoing primary, single-level MIS LD were retrospectively reviewed and stratified on the basis of sex. Immediate postoperative Visual Analog Scale (VAS) pain scores and narcotic consumption were collected. Patient-reported outcomes, including Oswestry Disability Index (ODI), 12-Item Short-Form- (SF-12) Physical Component Score, and VAS back and leg pain, were collected preoperatively and at 6-week, 3-month, 6-month, and 12-month follow-up. Sex differences were tested for an association between immediate postoperative pain, narcotics utilization, and long-term improvements in patient-reported outcomes using linear regression. A total of 188 patients were included and 62.8% were male individuals. At the time of surgery, female individuals were older than male individuals (P=0.045). There were no observed differences in other demographic or perioperative characteristics between cohorts. Female individuals had similar inpatient VAS pain scores and narcotic consumption compared with male individuals. Female individuals had a higher ODI score than male individuals preoperatively, however, both cohorts had similar improvements in ODI at all postoperative time points. Both sexes had similar VAS back and leg pain and SF-12 PCS scores preoperatively and at all postoperative time points. Our study demonstrated that sex does not affect immediate postoperative pain, narcotic consumption, and long-term recovery following MIS LD. Female individuals demonstrated similar preoperative back and pain scores compared with male individuals but reported greater disability before surgery. However, both sexes experienced similar improvements in pain and disability at all follow-up time points through 12 months. The results of this study may enable providers to better counsel patients regarding the expected improvement in pain and disability.

Minimally invasive lumbar decompression in an ambulatory surgery center.

There is limited data regarding clinical and surgical outcomes of minimally invasive lumbar decompression (MIS LD) as an outpatient procedure. In this context, our purpose is to evaluate a single surgeon's experience with performing MIS LD in the outpatient versus inpatient setting and determining if there are differences in surgical and clinical outcomes. Patients undergoing primary, one- to three-level MIS LD were retrospectively reviewed and stratified by surgical setting: ambulatory surgical center (ASC) versus hospital. The cohorts were compared with respect to demographics, perioperative characteristics, complications, postoperative pain and narcotics consumption, and improvements in patient-reported outcomes. Five hundred and nine patients were included: 332 patients underwent surgery at an ASC and 177 patients underwent surgery at a hospital. The ASC patients were younger, more likely to be male, and carry Workers' Compensation insurance. The hospital patients were older, more likely to be diabetic, and had a greater comorbidity burden. Patients undergoing MIS LD in an ASC were less likely to have multi-level procedures and more likely to have decompression with discectomy compared to patients in the hospital cohort. There were two cases of superficial wound infection in the ASC cohort and a single case of a pulmonary embolus in the hospital cohort. Additionally, a total of 28 patients had recurrent herniated nucleus pulposus in the ASC cohort compared to 12 patients in the hospital cohort. There was one case of residual stenosis in the ASC cohort compared to eight cases in the hospital cohort. Both cohorts demonstrated similar preoperative ODI, VAS back pain, and VAS leg pain scores through 12-month follow-up. MIS LD is a safe and effective procedure in an ASC, however, appropriate patient selection and postoperative protocols are imperative in minimizing complications and optimizing safety and efficacy in the outpatient setting.

P56. Preoperative patient activation is not associated with inpatient pain or narcotic utilization after minimally invasive lumbar discectomy

BACKGROUND CONTEXT Minimally invasive lumbar microdiscectomy (MIS LD) is a commonly utilized treatment for symptomatic lumbar disc herniations. Recent investigations have focused on the role of patient engagement and involvement in their postoperative outcomes, referred to as patient activation. Increased patient activation has been associated with superior pain relief and functional recovery after spine procedures. However, no previous study has investigated the association of patient activation with immediate postoperative pain and narcotic consumption following MIS spinal procedures. PURPOSE To determine if an association exists between preoperative Patient Activation Measure (PAM) score and inpatient postoperative pain scores and narcotic utilization after MIS LD. STUDY DESIGN/SETTING Retrospective analysis. PATIENT SAMPLE Forty-seven patients with complete PAM scores and postoperative pain records who underwent primary, single-level MIS LD from 2015-2017. OUTCOME MEASURES Inpatient Visual Analogue Scale (VAS) pain score and inpatient narcotic consumption, quantified as oral morphine equivalents (OMEs). METHODS A prospectively maintained surgical database of patients who underwent primary, single-level MIS LD from 2015-2017 for degenerative pathology was retrospectively reviewed. Patients were grouped by top and bottom halves of preoperative PAM score (≤62, >62). VAS pain scores were used to characterize postoperative pain perception in patients. Inpatient narcotic consumption through discharge were quantified as OMEs. PAM score group was tested for an association with preoperative demographic and perioperative characteristics using student's t-test and chi-square analysis for continuous and categorical variables, respectively. Multivariate linear regression was used to test for an association between PAM score group and inpatient pain scores, and narcotic consumption on postoperative day (POD) 0. RESULTS Of the 47 patients were included in this analysis, 46.8% (22) had a PAM score of ≤62, while 53.2% (25) had a PAM score of >62. There were no significant differences in age, gender, body mass index, smoking status, preoperative comorbidity burden, or preoperative VAS pain score between cohorts (p>0.05 for each). Additionally, there were no significant differences between PAM score groups in regards to perioperative variables including operative time, estimated blood loss, and length of inpatient stay (p>0.05 for each). Finally, there were no significant differences in VAS pain scores or total and hourly narcotic consumption between PAM score groups and on POD 0 after MIS LD (p>0.05 for each). CONCLUSIONS Patient engagement and involvement, as measured by PAM score, was not associated with demographic or perioperative differences among those undergoing MIS LD. Additionally, patient activation was not a predictive factor for perceived pain and narcotics use in the immediate postoperative period after MIS LD. The reduced surgical trauma of MIS LD compared to other spine procedures limits the degree of postoperative pain that patients experience, thus reducing overall narcotic requirement. This may minimize the effect of patient motivation and therefore patient activation on postoperative narcotic use in this cohort. More investigation is required, specifically analyzing the role of patient activation in long-term, post-discharge narcotics usage and dependence after MIS procedures. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Safety and Efficacy of Revision Minimally Invasive Lumbar Decompression in the Ambulatory Setting.

A retrospective analysis. The aim of this study was to investigate differences in perioperative outcomes between patients undergoing revision minimally invasive lumbar spine decompression (MIS LD) in the ambulatory and hospital-based surgical settings. Revision LD has been associated with an increased risk of complications compared with primary LD. Furthermore, ambulatory primary LD has been demonstrated to be a safe and viable option in appropriately selected patients. However, there is a paucity of information comparing hospital-based versus ambulatory outcomes in revision LD. A prospectively maintained surgical registry of patients undergoing revision MIS lumbar laminectomy and/or discectomy for degenerative pathology from 2013 to 2017 was retrospectively reviewed. Propensity score matching was performed to adjust for measured confounding variables, including patient age, comorbidity burden as measured by Charlson Comorbidity Index, and preoperative diagnosis. Differences in operative variables, complication rates, pain scores, narcotics consumption, and reoperation rates were assessed using Pearson Chi-squared analysis (categorical) and Student t test (continuous). Seventy patients were included, of whom 35 underwent revision MIS LD at a hospital-based center (HBC), and 35 underwent surgery at an ambulatory surgical center (ASC). HBC and ASC patients demonstrated similar postoperative visual analog scale pain scores and hourly narcotics consumption during surgical stay (P < 0.001). ASC patients exhibited a significantly shorter length of stay than hospital-based patients (2.7 vs. 11.6 hours, P < 0.001). Patients undergoing revision MIS LD in an ASC demonstrated similar perioperative outcomes as compared to patients undergoing revision MIS LD in a HBC. These results suggest that revision MIS LD can be performed safe and effectively in the ambulatory setting in an appropriately selected surgical population. Further study of patient outcomes following spine surgery performed outside of the traditional hospital setting is crucial, as the delivery of care in the ambulatory setting continues to grow in popularity. 3.

Narcotic Consumption Following Minimally Invasive Lumbar Decompression: A Comparison Between Hospital and Ambulatory-Based Surgery Centers.

Several studies have compared outcomes between hospital-based centers (HBCs) and ambulatory surgery centers (ASCs) following minimally invasive lumbar decompression (MIS LD). However, the association between narcotic consumption and pain in the immediate postoperative period has not been well characterized. As such, this study aims to examine pain, narcotic consumption, and length of stay (LOS) among patients discharged on postoperative day 0 following a 1-level MIS LD between HBCs or ASCs. Patients who underwent a primary, 1-level MIS LD were retrospectively reviewed and stratified by operative location. Differences between groups in patient demographics were assessed using independent-sample t tests for continuous variables and χ2 analysis for categoric variables. The operative location and its effect on perioperative characteristics, inpatient pain scores, and narcotics consumption were analyzed using multivariate linear regression adjusted for significant patient characteristics. There were 235 patients identified, of whom 90 and 145 underwent surgery at an HBC or ASC, respectively. The HBC cohort exhibited an increased comorbidity burden and had a greater percentage of privately insured patients. The HBC cohort recorded shorter operative time and greater total estimated blood loss. Patients in the HBC cohort experienced prolonged LOS, and consumed greater total oral morphine equivalents compared with the ASC cohort. No differences were observed in the remaining outcomes. The results of the current study suggest that patients who underwent MIS LD at an ASC received fewer narcotics than patients treated at an HBC, which may contribute to shortened LOS. Additionally, there was no difference in patient-reported pain between cohorts despite the differences in narcotic use. As such, postoperative narcotics administration varied, indicating HBC patients perhaps required more narcotic pain medications to achieve the same pain scores that were sufficient enough to allow patient discharge, thus prolonging LOS. III.

PROMIS Physical Function Score Strongly Correlates With Legacy Outcome Measures in Minimally Invasive Lumbar Microdiscectomy.

Retrospective cohort. This study aims to determine the validity of the patient-reported outcomes measurement information system (PROMIS) physical function (PF) in minimally invasive lumbar discectomy (MIS LD) patients. PROMIS was designed to allow for assessment of clinical outcomes in fewer questions than previous outcome measures with the goal of reducing noncompliance associated with longer, time-consuming surveys. However, there exists a paucity of evidence regarding the efficacy of the PROMIS PF domain in patients undergoing MIS LD. A surgical database of patients undergoing 1-3 level MIS LD was retrospectively reviewed. Postoperative changes in PROMIS PF scores were analyzed at 6-weeks, 12-weeks, and 6-months using paired Student t tests. PROMIS scores were compared to Oswestry disability index (ODI), visual analog scale (VAS) back, and VAS leg scores. Correlations were tested using Pearson correlation coefficient. Forty-one MIS LD patients were identified, reporting an average preoperative PROMIS PF score of 35.36 ± 7. Patients demonstrated significant improvement in ODI, VAS back, and VAS leg scores. Additionally, strong associations with PROMIS scores were observed for preoperative and postoperative ODI (r range: 0.5735-0.8543) and postoperative VAS back (r range: 0.5332-0.6522) and VAS leg pain (r range: 0.5257-0.6412). Patients undergoing MIS LD demonstrated significant improvements in PROMIS PF, ODI, VAS back, and VAS leg pain postoperatively. Additionally, improvements in PROMIS physical function scores at each postoperative time point were determined to be significantly correlated with ODI, VAS back, and VAS leg pain. The results of the current study demonstrate PROMIS PF has strong utility as a postoperative outcome assessment tool. 4.

Risk Factors for a Long Hospital Stay Following Minimally Invasive Lumbar Discectomy.

Retrospective cohort study. The purpose of the study was to determine risk factors for discharge after postoperative day (POD) 0 in patients undergoing 1-level minimally invasive lumbar discectomy (MIS LD). MIS LD has proven to be an effective treatment modality for low back pain and radiculopathy associated with intervertebral disc herniations. With increasing focus on cost reduction and value-based care, minimization of postoperative length of stay has become an important topic for physicians and hospital administrators. A prospectively maintained surgical database of patients who underwent 1-level MIS LD by a single surgeon from 2011 to 2016 was reviewed. Long length of stay was defined as discharge after POD 0. Bivariate and stepwise multivariate Poisson regression with robust error variance was used to determine risk factors for discharge after POD 0. Variables analyzed included patient demographics, comorbidities, operative characteristics, preoperative pain scores, postoperative inpatient pain scores, and postoperative narcotics consumption. A total of 176 patients were included; 9.7% of included patients were discharged on POD 1 or later. On bivariate analysis, diabetic status (57.1% vs. 7.7%; relative risk [RR]=7.43; P<0.01) and narcotic consumption <6.00 oral morphine equivalents/h (13.1% vs. 1.2%; RR=11.11; P=0.019) were associated with a prolonged length of stay. On stepwise multivariate analysis, diabetic status (RR=10.5; 95% confidence interval, 3.60-30.98; P<0.001) was found to be independently associated with a prolonged length of stay after MIS LD. The results indicate that diabetic status is an independent risk factor for increased LOS following single-level MIS LD. Delayed hospital discharge can lead to increased costs, increased risk of complications, and decreased patient satisfaction. Thus, providers can use this information to better counsel diabetic patients and monitor them more closely following MIS LD. Additional work must be done to better understand risk factors for increased length of stay following MIS LD in procedure-specific populations. Level II.

The Effect of Preoperative Symptom Duration on Postoperative Outcomes After a Tubular Lumbar Microdiscectomy.

This is a retrospective cohort study. This study aims to characterize the effect of preoperative symptom duration on postoperative outcomes after minimally invasive lumbar microdiscectomy (MIS LD). It is unknown whether extended nonoperative treatment before MIS LD has implications for long-term clinical outcomes even after surgery is performed. A prospectively maintained surgical registry of patients undergoing MIS LD by a single surgeon between 2013 and 2017 was reviewed. Preoperative symptom duration was dichotomized into 2 groups (≤6 and >6 mo). Only patients with full clinical data at 6 months postoperative follow-up were included in the study. Clinical outcomes were assessed at 6, 12 weeks, and 6 months after surgery. The number of patients obtaining a minimum clinically important difference was assessed. Groups were compared with the χ analysis and the student t tests for categorical and continuous data, respectively. In total, 94 patients were identified. A total of 45 patients (47.9%) had symptom duration ≤6 months. No differences in baseline characteristics were found (P>0.05). Patients with shorter symptom duration had significantly greater improvement in Oswestry Disability Index scores at 6 weeks (P=0.004), 12 weeks (P=0.022), and 6 months (P=0.005). Patients with shorter duration of symptoms also obtained minimum clinically important difference for Oswestry Disability Index at a greater rate than those with longer duration of symptoms (P=0.015). Although patients who underwent MIS LD within 6 months of symptom onset had similar baseline characteristics compared with patients who underwent surgery after 6 months of symptoms, the patients with longer preoperative symptom duration had worse functional outcomes at 6 months after surgery. These results suggest that earlier MIS lumbar microdiscectomy may provide a functional benefit for patients. Further studies should therefore evaluate the efficacy of nonoperative treatment in the setting of lumbar herniated nucleus pulposus, as prolonged conservative management may potentially impair functional recovery after surgery.

Wednesday, September 26, 2018 2:00 PM – 3:00 PM Surgery and Opioids: 73. Narcotic consumption following minimally invasive lumbar decompression: a comparison between hospital and ambulatory-based surgery centers

BACKGROUND CONTEXT Studies have compared outcomes between hospital-based (HBC) and ambulatory surgery (ASC) centers following minimally invasive lumbar decompression (MIS LD). However, the association between narcotic consumption and pain in the immediate postoperative period has not been well characterized. PURPOSE To examine pain, narcotic consumption, and length of stay (LOS) among patients discharged on postoperative day (POD) 0 following a 1-level MIS LD between an HBC and ASC. STUDY DESIGN/SETTING Retrospective analysis of a prospectively maintained surgical database. PATIENT SAMPLE A total of 235 patients who underwent a primary, 1-level MIS LD procedure from 2013 to 2017. OUTCOME MEASURES Inpatient pain using visual analog scale (VAS) pain scores, and narcotic consumption as oral morphine equivalents (OMEs). METHODS A surgical registry of patients who underwent a primary, 1-level MIS LD during 2013-2017 was reviewed, and were stratified by operative location. Differences between groups in demographics were assessed using independent sample t tests for continuous variables and chi-squared analysis for categorical variables. The operative location and its effect on perioperative characteristics, inpatient pain scores and narcotics consumption was analyzed using multivariate linear regression adjusted for significant patient characteristics. RESULTS A total of 235 patients were identified, of which 90 and 145 underwent surgery at a HBC or ASC, respectively. The HBC cohort exhibited an increased comorbidity burden, as defined by the Charlson Comorbidity Index (HBC: 1.1, ASC: 0.8; p=.041) and were more likely to have private insurance (HBC: 76.7%, ASC: 37.2%; p=.026). Distributions of age, sex, body mass index, and smoking status was similar between groups (p>.05 for each). The HBC cohort recorded shorter operative time (p CONCLUSIONS The results of the current study suggest that patients at who underwent MIS LD at an ASC receive fewer narcotics than patients treated at a HBC, which may contribute to shortened length of stay. Additionally, there was no difference in patient-reported pain between cohorts despite the differences in narcotic utilization. As such, postoperative narcotics administration can be decreased without compromising pain control and may contribute to faster discharge. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Minimally invasive lumbar discectomy (MIS LD) has proven to be an effective treatment modality for low back pain and radiculopathy associated with intervertebral disc herniations. With the increasing focus on cost reduction and value-based care, minimization of postoperative length of stay has become an important topic for physicians and hospital administrators. Despite this, risk factors for prolonged length of stay after MIS LD have not been previously described. PURPOSE To determine risk factors for discharge after postoperative (POD) 0 in patients undergoing one-level MIS LD. STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE A total of 176 patients who underwent one-level MIS LD from 2011 to 2016. OUTCOME MEASURES Relative Risk (RR) of preoperative and operative characteristics for discharge after POD 0. METHODS A prospectively maintained surgical database of patients who underwent one-level MIS LD by a single surgeon from 2011 to 2016 was reviewed. Long length of stay was defined as discharge after POD 0. Bivariate and stepwise multivariate Poisson regression with robust error variance was used to determine risk factors for discharge after POD 0. Variables analyzed included patient demographics, comorbidities, operative characteristics, preoperative pain scores, postoperative inpatient pain scores and postoperative narcotics consumption as measured by oral morphine equivalents (OMEs). A p-value RESULTS A total of 176 patients were included in this analysis. 9.7% of included patients were discharged on POD 1 or later, qualifying as having a long length of stay. On bivariate analysis, diabetic status (57.1% vs. 7.7%, Relative Risk [RR]=7.43, p CONCLUSIONS The results of this study suggest that patients with diabetes mellitus and those with low postoperative narcotic consumption have longer lengths of inpatient stay upon undergoing a one-level MIS LD. Diabetic patients may experience longer length of stay due to requiring extensive postoperative blood glucose management or as a result of increased susceptibility to postoperative infection. Surgeons can use this information to better counsel patients on expected length of stay and optimal narcotics utilization postoperatively.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT There is considerable debate regarding the appropriate duration of nonoperative treatment before surgery is considered for a lumbar disc herniation. Moreover, it is unknown if extended nonoperative treatment has implications for long term clinical outcomes even after surgery is performed. PURPOSE To characterize the effect of preoperative symptom duration on postoperative outcomes following minimally invasive lumbar microdiscectomy (MIS LD). STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE A total of 94 patients who underwent a MIS LD between 2013 and 2017. OUTCOME MEASURES Improvements in ODI, VAS back and VAS leg scores from preoperative to postoperative time points (6 week, 12 week and 6 month). METHODS A prospectively maintained surgical registry of patients undergoing MIS LD by a single surgeon between 2013 and 2017 was reviewed. Preoperative symptom duration was dichotomized into two groups (≤6 months, >6 months). Only patients with full clinical data at 6 months postoperative follow-up were included in the study. Clinical outcomes including Oswestry Disability Index (ODI), Visual Analog Scale (VAS) back, and VAS leg were assessed at 6 weeks, 12 weeks and 6 months postoperative. The amounts of patients obtaining a minimum clinically important difference (MCID) for each clinical outcome were also assessed. Groups were compared with chi-square analysis and student t-tests for categorical and continuous data, respectively. Statistical significance was set at p RESULTS After exclusion of those with incomplete data, a total of 94 patients were identified, 45 with symptom duration ≤6 months and 49 with symptom duration >6 months. No differences in baseline or perioperative characteristics were found (p>.05). When comparing patient reported outcomes, patients with shorter symptom duration had significantly greater improvement in ODI scores at 6 weeks (P=.004), 12 weeks (P=.022) and 6 months (P=.005) was found for patients with shorter preoperative symptom duration. Patients with shorter symptom duration also obtained MCID for ODI at a greater rate than those with longer duration of symptoms, (p=.015). Additionally, patients with a shorter duration of symptoms had greater postoperative improvements in VAS leg pain, though this was not statistically significant. For VAS back pain, no differences were found between groups. CONCLUSIONS Patients that underwent MIS LD within 6 months of symptom onset had similar baseline characteristics compared to patients who underwent surgery after 6 months. However, the patients with shorter preoperative symptom duration had greater clinical improvement postoperatively. Further studies should evaluate the efficacy of nonoperative treatment in the setting of lumbar disc herniations particularly as it may potentially impair functional recovering following delayed surgical intervention.