Thrombocytopenia as an Independent Prognostic Indicator Following Extradural Spinal Tumor Resection.

OBJECTIVE: Few studies have examined the prognosis for patients with baseline thrombocytopenia undergoing extradural spine tumor resection. Our objective was to evaluate mortality, readmission, and other 30-day outcomes in patients with varying degrees of preoperative thrombocytopenia undergoing osseous extradural tumor excision. METHODS: A multicenter registry was queried for patients treated from 2011-2019. Patients were categorized according to baseline preoperative platelet count, in 25,000/µL increments: 125,000-149,000/µL, 100,000-125,000/µL, 75,000-100,000/µL, and <75,000/µL. These were compared to a control group with platelet count >150,000/µL. Outcomes in each cohort were analyzed using multivariate logistic regression analysis. RESULTS: The database search revealed 3574 patients undergoing extradural tumor resection; 2171 (60.7%) patients with platelets 125,000-149,000/µL, 114 (3.2%) with 100,000-125,000/µL, 43 (1.2%) with 75,000-100,000/µL, and 42 (1.2%) with <75,000/µL. Platelet counts <100,000/µL was associated with perioperative blood transfusion, cardiac complications, non-home discharge, and 30-day mortality. On subgroup analysis for mortality, an interaction was present between individuals with moderate/severe thrombocytopenia and cervical tumors. CONCLUSIONS: In patients undergoing surgery for extradural spine tumor, degree of baseline thrombocytopenia-rather than presence alone-is an independent predictor of several adverse events. Wherever possible, optimization of preoperative platelet count to at least 100,000/µL may improve outcomes.

Risk Factors for Medical and Surgical Complications After Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion.

BACKGROUND: The prevention of perioperative and postoperative complications is necessary to avoid poor postoperative outcomes and increased costs. Previous investigations have identified risk factors for complications after various spine procedures, but no such study exists in a population solely undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). The purpose of this study is to determine risk factors for the development of complications up to 2 years after MIS TLIF procedures. METHODS: Patients who underwent primary, single-level MIS TLIF from 2007 to 2016 were retrospectively reviewed. The incidence of medical and surgical complications up to 2 years postoperatively was determined. Patients were categorized according to demographic, comorbidity, and procedural characteristics. Bivariate Poisson regression with robust error variance was used to determine if an association existed between patient characteristics and complication incidence. A final multivariate model including all patient characteristics as controls was created using backwards, stepwise regression until only those variables with P < .05 remained. RESULTS: 390 patients were analyzed. Upon bivariate analysis, age >50 years (P = .025), diabetes mellitus (P = .001), and operative duration >105 minutes (P = .016) were associated with increased medical complication rates. Regarding surgical complications, age ≤50 years (P < .001), obesity (P = .012), and diabetes mellitus (P = .042) were identified as risk factors on bivariate analysis. Upon final multivariate analysis, operative time >105 minutes (P = .009) and diabetes mellitus (P = .001) were independent risk factors for medical complications. Independent risk factors for surgical complications on multivariate analysis included age ≤50 years (P < .001), diabetes mellitus (P = .002), and obesity (P = .030). CONCLUSIONS: Diabetic patients and those who underwent longer operations were at increased risk of medical complications, while younger patients, obese patients and those also with diabetes mellitus were at increased risk of surgical complications up to 2 years after MIS TLIF. Practitioners can use this information to identify patients who require preventative care before their procedure or increased postoperative vigilance and monitoring after single-level MIS TLIF. LEVEL OF EVIDENCE: 3.

Static Versus Expandable Devices Provide Similar Clinical Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion.

BACKGROUND: Few studies have analyzed differences in radiographic parameters and patient-reported outcomes (PROs) between expandable and static interbody devices in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). QUESTIONS/PURPOSES: To evaluate differences in radiographic parameters and PROs following MIS TLIF between static and expandable interbody devices. METHODS: Patients undergoing primary, single-level MIS TLIF between 2014 and 2017 were retrospectively identified. Radiographic measurements including lumbar lordosis (LL), segmental lordosis (SL), disc height (DH), and foraminal height (FH) were performed on lateral radiographs before and after MIS TLIF with a static or expandable articulating interbody device. Radiographic outcomes and PROs were compared using paired and unpaired Student's t test. RESULTS: Thirty patients received expandable interbody devices and 30 patients received static interbody devices. The expandable device cohort exhibited significantly greater improvement in DH and FH at final follow-up compared with those receiving a static device. Both device cohorts experienced significant improvements in PROs at 6 months post-operatively. CONCLUSION: MIS TLIF with an expandable interbody device led to a greater increase of DH and FH than with a static interbody device. Patients undergoing MIS TLIF can expect similar improvements in PROs whether receiving a static or an expandable interbody device. Further studies are required to better understand improvements in clinical outcomes afforded by expandable interbody devices.

Patient Perceptions of Iliac Crest Bone Grafting in Minimally Invasive Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: The objective of this study was to determine patients' perception of iliac crest bone graft (ICBG) harvesting and donor site pain following minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). SUMMARY OF BACKGROUND DATA: The incidence of donor site pain has been debated in the literature because of the varying techniques associated with its harvest. METHODS: Patients undergoing primary, single-level MIS TLIF with ICBG were retrospectively identified. ICBG harvesting was performed using a percutaneous technique with a tubular retractor. A survey was administered to assess if patients could accurately describe which side of their iliac crest they believed was harvested, and if they were experiencing any pain perceived to be originating from the donor site. Patient characteristics were compared using χ analysis and independent t test. RESULTS: In total, 82 patients were included. The majority of patients had the ICBG harvested from the left iliac crest (97.5%). Approximately half of the patients correctly identified the side of harvest (50.6%). 48.1% of patients reported they were not confident or had guessed on their response. Patients that reported pain from the ICBG were more likely to feel confident or somewhat confident in their harvest site identification (57.9% vs. 46.3%) but less likely to be correct (36.8% vs. 63.4%) than patients without pain. 22 patients (27.8%) correctly identified the side of harvest without guessing. Of these, 11 (13.9%) reported pain. CONCLUSIONS: Approximately half of patients undergoing MIS TLIF with ICBG are able to correctly identify which side of their iliac crest was harvested. However, the majority of patients reporting pain were unable to correctly identify the side of harvest. This suggests that most patients are likely attributing other sources of pain to their ICBG. Therefore, rates of donor site pain may be over-reported in the current literature with contemporary harvesting techniques.

The Influence of Conflicts of Interest on Outcomes in the Lumbar Disc Arthroplasty Literature: A Systematic Review.

STUDY DESIGN: A systematic review. OBJECTIVE: The aim of this study was to determine the association between study outcomes and the presence of a conflict of interest (COI) in the lumbar disc arthroplasty (LDA) literature. SUMMARY OF BACKGROUND DATA: Previous studies have evaluated the efficacy of LDA as a surgical alternative to arthrodesis. As investigators may have financial relationships with LDA device companies, it is important to consider the role of COI on study outcomes. METHODS: A systematic review was performed to identify articles reporting clinical outcomes of LDA. Any financial COIs disclosed were recorded and confirmed through Open Payments and ProPublica databases. Study outcomes were graded as favorable, unfavorable, or equivocal. Pearson Chi-squared analysis was used to determine an association between COI and study outcomes. Favorable outcomes were tested for an association with study characteristics using Poisson regression with robust error variance. RESULTS: Fifty-seven articles were included, 30 had a financial COI, while 27 did not. Ninety percent of the conflicted studies disclosed their COI in the article. Studies with United States authors were more likely to be conflicted (P = 0.019). A majority of studies reported favorable outcomes for LDA (n = 39). Conflicted studies were more likely to report favorable outcomes than nonconflicted studies (P = 0.020). Articles with COIs related to consultant fees (P = 0.003), research funding (P = 0.002), and stock ownership (P < 0.001) were more likely to report favorable outcomes. CONCLUSION: This study highlights the importance for authors to accurately report conflicting relationships with industry. As such, orthopedic surgeons should critically evaluate study outcomes with regard to potential conflicts before recommending LDA as a surgical option to their patients. LEVEL OF EVIDENCE: 3.

Does the Day of the Week Affect Length of Stay and Hospital Charges Following Anterior Cervical Discectomy and Fusion?

BACKGROUND: To reduce the economic impact of excessive costs, risk factors for increased length of stay (LOS) must be identified. Previous literature has demonstrated that surgeries later in the week can affect the LOS and costs following joint arthroplasty. However, few investigations regarding the day of surgery have been performed in the spine literature. The present study attempts to identify the association between day of surgery on LOS and hospital charges following anterior cervical discectomy and fusion (ACDF) procedures. METHODS: A prospectively maintained surgical database of primary, level 1-2 ACDF patients between 2008 and 2015 was retrospectively reviewed. Patients were stratified by surgery day: early week (Tuesday) or late week (Friday) ACDF. Differences in patient demographics and preoperative characteristics were compared between cohorts using chi-square analysis or Student t test for categorical and continuous variables, respectively. Direct hospital costs were obtained using hospital charges for each procedure and subsequent care prior to discharge. Associations between date of surgery and costs were assessed using multivariate linear regression controlled for. RESULTS: Two hundred and ninety-five patients were included in the analysis. One hundred and fifty-three patients underwent early week ACDF, and 142 underwent late week ACDF. Surgery day cohorts reported similar baseline characteristics. There were no differences in operative characteristics or hospital LOS between cohorts. Additionally, no differences in total or subcategorical hospital costs were identified between surgery day cohorts. CONCLUSIONS: Patients undergoing ACDF later in the week exhibit similar LOS and hospital costs compared to those undergoing ACDF early in the week. These results suggest that outpatient procedures with short postoperative stays are likely not affected by the changes in hospital work efficiency that occur during the transition to the weekend. As such, hospitals should not restrict outpatient procedures to specific days of the week. LEVEL OF EVIDENCE: 3.

Impact of Iliac Crest Bone Grafting on Postoperative Outcomes and Complication Rates Following Minimally Invasive Transforaminal Lumbar Interbody Fusion.

OBJECTIVE: The relationship between bone graft technique and postoperative outcomes for minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has not been well-defined. This study aims to determine the effect of iliac crest bone grafting (ICBG) on patient-reported outcomes (PROs) and complication rates following MIS TLIF. METHODS: Primary, single-level MIS TLIF patients were consecutively analyzed. Patients that prospectively received a percutaneous technique of ICBG were compared to patients that retrospectively received bone morphogenetic protein-2 (BMP-2). Complication rates were assessed perioperatively and up to 1 year postoperatively. Changes in Oswestry Disability Index (ODI), visual analogue scale (VAS) back, and VAS leg pain were compared. Rates of minimum clinically important difference (MCID) achievement at final follow-up for ODI, VAS back, and VAS leg scores were compared. RESULTS: One hundred forty-nine patients were included: 101 in the BMP-2 cohort and 48 in the ICBG cohort. The ICBG cohort demonstrated increases in intraoperative blood loss and shorter lengths of stay. ICBG patients also experienced longer operative times, though this did not reach statistical significance. No significant differences in complication or reoperation rates were identified. The ICBG cohort demonstrated greater improvements in VAS leg pain at 6-week and 12-week follow-up. No other significant differences in PROs or MCID achievement rates were identified. CONCLUSION: Patients undergoing MIS TLIF with ICBG experienced clinically insignificant increases in intraoperative blood loss and did not experience increases in postoperative pain or disability. Complication and reoperation rates were similar between groups. These results suggest that ICBG is a safe option for MIS TLIF.

Swallowing Function Following Anterior Cervical Discectomy and Fusion With and Without Anterior Plating: A SWAL-QOL (Swallowing-Quality of Life) and Radiographic Assessment.

OBJECTIVE: Anterior cervical plating in anterior cervical discectomy and fusion (ACDF) procedures are associated with improved outcomes compared to stand-alone cages. However, concerns exist regarding increased rates of postoperative dysphagia following an ACDF. This study aims to quantify the effect of anterior plating on swallowing-quality of life (SWAL-QOL) scores and radiographic swelling assessments following a primary, single-level ACDF. METHODS: Patients retrospectively reviewed. Patients grouped into those receiving a cage or anterior plate. SWAL-QOL scores were recorded preoperatively and 6 weeks and 12 weeks postoperatively. Lateral radiographs were used to create a swelling index with a ratio of the prevertebral swelling distance to the anterior-posterior diameter of each involved vertebral body. An air index was created using the same methodology. Statistical analysis was performed using chi-square analysis and independent t-tests for categorical and continuous variables. RESULTS: Sixty-eight primary, single-level ACDF patients were included. Forty-one (60.3%) received a stand-alone cage and 27 (39.7%) received a cage with anterior plating. No differences in demographics, comorbidities, operative time, estimated blood loss, or length of hospital stay were identified between Cage and Plate cohorts. Finally, no differences were observed in postoperative SWAL-QOL scores or swelling and air indices between groups. CONCLUSION: The results demonstrate that patients undergoing a primary, single-level ACDF with or without anterior plating experience similar operative times and lengths of stay. Patients that receive a cage with anterior plating did not experience significant increases in dysphagia as measured by the SWAL-QOL questionnaire compared to patients that received a stand-alone cage. Furthermore, radiographic assessments of swelling are comparable.

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. LEVEL OF EVIDENCE: III.

Evaluating the Concurrent Validity of PROMIS Physical Function in Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: This study was a retrospective cohort analysis. OBJECTIVES: This study aims to evaluate the concurrent validity of Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) domain as compared with legacy measures of patient-reported outcomes (PROs) among patients undergoing anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: As PROMIS becomes increasingly utilized, it is important to assess its validity among procedure-specific populations. METHODS: Patients undergoing a primary, 1-3 level ACDF were retrospectively identified from a prospectively maintained surgical registry. PROMIS PF and legacy PRO scores were obtained at preoperative, 6-week, 12-week, and 6-month postoperative visits. Legacy PROs included Neck Disability Index (NDI), Short Form-12 (SF-12) physical composite, Visual Analog Scale (VAS) neck pain, and VAS arm pain. Postoperative improvements in PROs were assessed using paired t tests. Correlations between PROMIS and legacy PROs were tested using Pearson correlation coefficient. RESULTS: A total of 57 ACDF patients were analyzed. The mean preoperative PROMIS PF was 40.0±6.4. PROMIS PF significantly improved at 12-week and 6-month follow-up. NDI, VAS neck pain, and VAS arm pain scores demonstrated significant improvement at all postoperative time points. SF-12 scores only exhibited significant improvement at the 6-month follow-up visit. Significant correlations between PROMIS PF, NDI, and SF-12 were identified at all preoperative and postoperative time points. PROMIS PF exhibited strong correlations with VAS neck pain at postoperative time points, and a moderate correlation preoperatively. CONCLUSIONS: Patients undergoing a primary 1-3 level ACDF experience significant improvements in PROMIS PF scores at 12-week and 6-month follow-up. Furthermore, PROMIS PF exhibits strong correlations to NDI and SF-12 at all preoperative and postoperative time points. These results suggest that PROMIS PF accurately measures PF and may be used in lieu of legacy PF instruments for patients undergoing ACDF.

The Patient-Reported Outcomes Measurement Information System in spine surgery: a systematic review.

OBJECTIVEThe Patient-Reported Outcomes Measurement Information System (PROMIS) was developed to provide a standardized measure of clinical outcomes that is valid and reliable across a variety of patient populations. PROMIS has exhibited strong correlations with many legacy patient-reported outcome (PRO) measures. However, it is unclear to what extent PROMIS has been used within the spine literature. In this context, the purpose of this systematic review was to provide a comprehensive overview of the PROMIS literature for spine-specific populations that can be used to inform clinicians and guide future work. Specifically, the authors aimed to 1) evaluate publication trends of PROMIS in the spine literature, 2) assess how studies have used PROMIS, and 3) determine the correlations of PROMIS domains with legacy PROs as reported for spine populations.METHODSStudies reporting PROMIS scores among spine populations were identified from PubMed/MEDLINE and a review of reference lists from obtained studies. Articles were excluded if they did not report original results, or if the study population was not evaluated or treated for spine-related complaints. Characteristics of each study and journal in which it was published were recorded. Correlation of PROMIS to legacy PROs was reported with 0.1 ≤ |r| < 0.3, 0.3 ≤ |r| < 0.5, and |r| ≥ 0.5 indicating weak, moderate, and strong correlations, respectively.RESULTSTwenty-one articles were included in this analysis. Twelve studies assessed the validity of PROMIS whereas 9 used PROMIS as an outcome measure. The first study discussing PROMIS in patients with spine disorders was published in 2012, whereas the majority were published in 2017. The most common PROMIS domain used was Pain Interference. Assessments of PROMIS validity were most frequently performed with the Neck Disability Index. PROMIS domains demonstrated moderate to strong correlations with the legacy PROs that were evaluated. Studies assessing the validity of PROMIS exhibited substantial variability in PROMIS domains and legacy PROs used for comparisons.CONCLUSIONSThere has been a recent increase in the use of PROMIS within the spine literature. However, only a minority of studies have incorporated PROMIS for its intended use as an outcomes measure. Overall, PROMIS has exhibited moderate to strong correlations with a majority of legacy PROs used in the spine literature. These results suggest that PROMIS can be effective in the assessment and tracking of PROs among spine populations.

The Impact of Comorbidity Burden on Complications, Length of Stay, and Direct Hospital Costs After Minimally Invasive Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: A retrospective cohort. OBJECTIVE: The aim of this study was to determine whether comorbidity as determined by Charlson Comorbidity Index (CCI) is associated with inpatient complication rate, length of stay (LOS), or direct hospital costs after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). SUMMARY OF BACKGROUND DATA: In the spine literature, comorbidity burden has been associated with an increased risk for complications, prolonged LOS, and greater hospital costs. Few studies have investigated the influence of comorbidity burden on these outcomes in minimally invasive spine surgery populations. METHODS: A prospectively maintained surgical registry of patients undergoing primary, single-level MIS-TLIF was retrospectively reviewed. Patients were stratified by CCI and tested for association with preoperative demographics and perioperative characteristics using Chi-squared analysis or one-way analysis of variance for categorical and continuous variables, respectively. Complication rates, LOS, and direct hospital costs were compared between groups using a one-way analysis of variance. RESULTS: Two hundred ninety-eight patients were included. About 19.8% had a CCI of 0, 41.3% had a CCI of 1 to 2, 27.2% had a CCI of 3 to 4, and 11.7% had a CCI ≥ 5. Elevated CCI was associated with older age, smoking, and insurance status. Elevated CCI was significantly associated with a greater total inpatient complication rate. Regarding LOS and total direct hospital costs, there were no associations identified. However, elevated CCI was associated with greater costs accrued in the intensive care unit, laboratory costs, and cardiology-related costs. CONCLUSION: Greater comorbidity burden as reflected by higher CCI was associated with increased postoperative complication rates following primary, single-level MIS-TLIF. However, this did not lead to prolongations in hospital stay or increased total direct hospital costs. This lack of association may suggest that the limited tissue trauma and operative exposure utilized in minimally invasive approaches may limit the utility of CCI as a predictor of surgical outcomes and costs. LEVEL OF EVIDENCE: 4.

The Effect of Preoperative Medications on Length of Stay, Inpatient Pain, and Narcotics Consumption After Minimally Invasive Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: To determine the association between preoperative medications and length of stay, inpatient pain, and narcotics consumption after a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). SUMMARY OF BACKGROUND DATA: Previous studies have identified risk factors for increased length of hospital stay, inpatient pain, and narcotics consumption. However, little is known regarding the effects of preoperative medications on outcomes after spine surgery. METHODS: A prospectively maintained surgical database of patients undergoing primary, single-level MIS TLIF was retrospectively reviewed. Preoperative medications taken within 30 days before surgery were recorded for each patient and categorized by medication type. Poisson regression with robust error variance was used to determine the association between preoperative medications and length of stay, pain scores, and narcotics consumption. Multivariate analysis was performed using a backwards, stepwise regression to identify independent risk factors. RESULTS: In total, 138 patients were included in this analysis. On bivariate analysis, benzodiazepines were associated with longer hospital stays [relative risk (RR)=2.03; P=0.031]. Benzodiazepines (RR=3.71; P<0.001) and preoperative narcotics (RR=2.60; P=0.012) were risk factors for pain ≥7 on postoperative day 0. On multivariate analysis, benzodiazepines were an independent risk factor for prolonged stay. Benzodiazepines, narcotics, and nonsteroidal anti-inflammatories were identified as independent risk factors for increased postoperative pain. CONCLUSIONS: These results suggest that benzodiazepines are a risk factor for increased length of stay and postoperative pain after MIS TLIF. Preoperative narcotics and nonsteroidal anti-inflammatories were also identified as risk factors for postoperative pain though this did not lead to increases in narcotics consumption. Patients taking these medications should undergo more vigilant perioperative monitoring for adequate pain management. More work must be done to further elucidate the association between preoperative medications and postoperative outcomes after MIS TLIF.

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

STUDY DESIGN: A retrospective analysis. OBJECTIVE: 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. SUMMARY OF BACKGROUND DATA: 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. METHODS: 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). RESULTS: 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). CONCLUSION: 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. LEVEL OF EVIDENCE: 3.

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

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: 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). SUMMARY OF BACKGROUND DATA: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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 OF EVIDENCE: Level II.

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

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: This study aims to characterize the effect of preoperative symptom duration on postoperative outcomes after minimally invasive lumbar microdiscectomy (MIS LD). SUMMARY OF BACKGROUND DATA: It is unknown whether extended nonoperative treatment before MIS LD has implications for long-term clinical outcomes even after surgery is performed. MATERIALS AND 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 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. RESULTS: 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). CONCLUSIONS: 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.

Sagittal Imbalance Does Not Influence Cup Anteversion in Total Hip Arthroplasty Dislocations.

STUDY DESIGN: Retrospective Cohort. SUMMARY OF BACKGROUND DATA: Studies have shown that lumbar fusion procedures are associated with an increased risk of total hip arthroplasty (THA) dislocation. Some have speculated that the increased risk of dislocation is caused by mispositioning of the acetabular component because of spinal sagittal imbalance. Unfortunately, the exact relationship between spinal sagittal balance and cup orientation is unknown. OBJECTIVE: The objective of this study was to investigate the effect of spinal sagittal alignment on cup anteversion in THA dislocation. METHODS: Patients that suffered a THA dislocation were retrospectively identified. Cross-table lateral hip radiographs were used to measure cup anteversion with normal acetabular anteversion defined as 15±10 degrees. Lateral lumbar spine radiographs were used to measure lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt, and sacral slope. Normal sagittal balance was defined as a PI-LL difference of <10 degrees. The association between sagittal balance and THA characteristics was assessed using Pearson correlation coefficient, χ analysis, and independent t tests. RESULTS: A total of 29 patients had full radiographic imaging. Among these patients, 62.1% dislocated following a primary THA and 37.9% following a revision THA. Abnormal spinal sagittal balance was identified in 20 patients (69.0%). Eight (27.6%) patients had undergone spinal fusion prior to THA. Abnormal cup anteversion was demonstrated in 51.7% of all patients. Presence of a spinal fusion was not associated with cup anteversion, sagittal balance, or time to dislocation. Sagittal balance was not associated with direction of dislocation, time to dislocation, or cup anteversion. CONCLUSIONS: A majority of patients with a THA dislocation demonstrated abnormal sagittal balance. However, sagittal balance was not associated with acetabular cup anteversion. As such, the relationship between spinal deformity and dislocation rates after THA may not be because of inaccurate cup orientation.

Impact of the Number of Levels on Adverse Events and Length of Stay Following Posterior Lumbar Fusion Procedures.

STUDY DESIGN: Retrospective SUMMARY OF BACKGROUND DATA:: Little is known regarding the impact of the number of operative levels on the risk for adverse events following spinal procedures. OBJECTIVE: The objective of this study was to test for associations between the number of operative levels and occurrence of adverse events following posterior lumbar fusion (PLF). METHODS: Patients undergoing 1-, 2-, or 3-level PLFs were identified in the American College of Surgeons National Surgical Quality Improvement Program database. The number of operative levels was tested for association with occurrence of adverse events in the 30-days following the procedure using multivariate regression. Post hoc pairwise comparisons were made between 1- and 2-level and between 2- and 3-level procedures. Analyses were adjusted for differences in baseline characteristics. RESULTS: In total, 8162 underwent 1-level, 3,527 underwent 2-level, and 718 underwent 3-level procedures. Patients undergoing 2-level procedures had a higher rate of anemia requiring blood transfusion than 1-level procedures (23.4% vs. 8.6%; adjusted relative risk [RR]=2.5; P<0.001). Furthermore, patient undergoing 3-level procedures had a higher rate of anemia requiring blood transfusion than 2-level procedures (29.9% vs. 23.4%; adjusted RR=1.3; P<0.001). In addition, patients undergoing 3-level procedures had a longer length of stay than 2-level procedures (4.6 vs. 3.9 d; P<0.001) and 2-level procedures had a longer length of stay than 1-level procedures (3.9 vs. 3.5 d; P<0.001). CONCLUSIONS: Increasing the number of operative levels by one level has minimal impact on the rates of most short-term postoperative adverse events following PLF. This is true both for an increase from 1 to 2 levels and from 2 to 3 levels. While surgeons should consider that an increase in the number of operative levels may increase the risk for blood transfusion and will almost certainly prolong the hospital stay, they need not fear a major increase in the rates of postoperative adverse events.

Does Gender Influence Postoperative Outcomes in Minimally Invasive Transforaminal Lumbar Interbody Fusion?

STUDY DESIGN: Retrospective cohort. OBJECTIVE: The objective of this study was to determine if an association exists between gender and postoperative improvements in patient-reported outcomes (PRO) measures following minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). SUMMARY OF BACKGROUND DATA: Current spine literature presents conflicting findings regarding the influence of gender on clinical outcomes. METHODS: Patients undergoing primary, single-level MIS TLIF were retrospectively reviewed. PRO measures including Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) back and leg pain scores were collected preoperatively and 6-week, 12-week, and 6-month postoperatively. Rates of minimum clinically important difference (MCID) achievement were determined at 6-months postoperative. Statistical analysis was performed using Pearson χ analysis or Student t test. RESULTS: In total, 169 patients, 40.83% females and 59.17% males, were included. Females experienced greater inpatient pain scores than males (POD 0: 5.30 vs. 4.69, P=0.041; POD 1: 4.80 vs. 4.13, P=0.019). Females demonstrated significantly greater ODI (43.77 vs. 36.22; P=0.002) and VAS leg (6.20 vs. 5.27; P=0.039) scores than males. No differences in postoperative improvements in ODI, VAS back or VAS leg pain scores were identified between genders, with exception to females demonstrating greater improvement in VAS leg pain at 6 months postoperatively (female: -4.40 vs. male: -3.32; P=0.033). Furthermore, no differences in MCID achievement for PROs were identified between cohorts. CONCLUSIONS: Females demonstrated greater preoperative pain and disability as well as inpatient VAS pain scores compared to males. Furthermore, gender was not associated with differences in length of stay, perioperative complication rates, or narcotics consumption. Improvements in pain and disability, as well as rates of MCID achievement were similar between genders. These findings suggest that gender is not associated with surgical or clinical outcomes and should not be used as a predictor of outcomes following MIS TLIF. LEVEL OF EVIDENCE: Level III.

Comparison of Postoperative Outcomes Between Primary MIS TLIF and MIS TLIF With Revision Decompression.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: To compare postoperative improvements in surgical and patient-reported outcomes (PROs) between patients undergoing minimally invasive laminectomy and minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) as a primary procedure to patients undergoing MIS laminectomy and TLIF as a revision to primary lumbar decompression (LD). SUMMARY OF BACKGROUND DATA: MIS TLIF and LD have demonstrated to be effective surgical options for lumbar degenerative disease. However, some patients undergoing LD experience recurrent symptoms and eventually require a revision decompression with fusion. METHODS: A prospectively maintained surgical database of patients who underwent a primary or revision one-level MIS TLIF for degenerative spinal pathology between 2014 and 2016 was reviewed. Consecutive patients undergoing primary MIS TLIF and revision lumbar discectomy and/or laminectomy were matched in a one-to-one fashion to primary MIS TLIF patients who had not undergone a previous LD by age and preoperative diagnosis. Differences in patient demographic, comorbidity, and perioperative characteristics between procedure groups were assessed using Pearson chi-squared analysis and Student t test for categorical and continuous variables, respectively. Improvements in PROs from preoperative values were compared between primary and revision cohorts using Student t tests. Pearson chi-squared analysis was used to compare rates of minimum clinically important difference achievement between procedure groups. Statistical significant was set at P < 0.05. RESULTS: A total of 52 patients were included in this analysis. Twenty-six underwent primary MIS laminectomy and TLIF and 26 underwent MIS TLIF with a revision decompression. No differences in baseline or perioperative variables were observed. Revision and primary MIS TLIF patients experienced similar improvements in PROs at all postoperative time points. CONCLUSION: The results of the present study demonstrate patients undergoing primary MIS TLIF with LD as a revision to a primary decompression experienced similar postoperative improvements in PROs as compared to primary MIS TLIF patients. This indicates a primary decompression does not compromise clinical outcomes in patients undergoing MIS TLIF. As such, patients should not be precluded from undergoing MIS TLIF based on the history of a previous LD. LEVEL OF EVIDENCE: 3.