Influence of Obesity on Complications, Clinical Outcome, and Subsidence After Anterior Lumbar Interbody Fusion (ALIF): Prospective Observational Study

Analysis of the Frequency of Intraoperative Complications in Anterior Lumbar Interbody Fusion: A Systematic Review

OBJECTIVE

We assessed the frequency of intraoperative complication rates related to access surgery, operating time, and intraoperative bleeding rates described in the literature for patients undergoing anterior lumbar interbody fusion (ALIF) to evaluate the adverse effects and, thus, help in therapeutic decision making and contribute to future clinical trials.

METHODS

A systematic review was conducted of MEDLINE and Embase databases in March 2023. The main inclusion criteria were adult patients aged >18 years, with no maximum age limit; the use of ALIF; the presence of quantitative data on intraoperative complications; and randomized controlled trials and cohort studies. Vascular and peritoneal injuries were considered primary endpoints. The operative time and intraoperative bleeding rate were secondary endpoints. Reports and case series, case-control series, systematic reviews, and meta-analyses were excluded.

RESULTS

Eight studies were included with a total of 2395 patients. We found important quantitative data for future randomized clinical studies involving ALIF surgery, including the rate of vascular lesions (2.79%) and peritoneal lesions (0.37%). In addition to these factors, only 4 of the 8 studies addressed the average surgery time, with a total average of 145.61 minutes. Furthermore, 6 of the 8 articles reported the mean rate of intraoperative bleeding, with a total mean blood loss of 272.75 mL.

CONCLUSIONS

ALIF is a lumbar spine access technique with low intraoperative complications. Patients with contraindications have a higher risk of complications. Randomized clinical trials are needed to assess the efficacy and safety of the procedure.

Trabecular Bone Remodeling as a New Indicator of Osteointegration After Posterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

We newly found that trabecular bone remodeling (TBR) often appeared in the fixed adjacent vertebrae during bony fusion. Thus, TBR might indicate osteointegration. Hence, we aimed to investigate whether TBR in the early postoperative period could predict future bony fusion after posterior lumbar interbody fusion (PLIF).

METHODS

We retrospectively analyzed 78 patients who underwent one-level PLIF. Demographic data were reviewed. Using computed tomography (CT) images taken at 3 months and 1 year postoperatively, we investigated the vertebral endplate cyst (VEC) formation, TBR in the vertebral body, cage subsidence, and clear zone around pedicle screw (CZPS).

RESULTS

TBR had high interobserver reliability regardless of cage materials. VECs, TBR, and both were found in 30, 53, and 16 patients at 3 months postoperatively and in 30, 65, and 22 patients at 1 year postoperatively, respectively. The incidence of VEC, which indicates poor fixation, was lower in early (3 months postoperatively) TBR-positive patients, with a significant difference at 1 year postoperatively (3 months, P = .074; 1 year, P = .003). Furthermore, 3 (5.7%) of the 53 early TBR-positive patients had CZPS without instability at 1 year postoperatively. In 25 TBR-negative patients, 1 (4.0%) had pedicle screw cutout requiring reoperation, 1 (4.0%) had pseudarthrosis, and 4 (16%) had CZPS.

CONCLUSIONS

Patients with early TBR (3 months) did not experience pedicle screw cutout nor pseudarthrosis and had significantly fewer VECs than those without early TBR. Thus, TBR may be a new radiological marker of initial fixation after PLIF.

Risk Factors for Subsidence Following Anterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) may be complicated by subsidence, which can lead to significant morbidity including pain, disc space collapse, neural compression, segmental kyphosis, instability, and vertebral body fracture. This study sought to identify patient and procedural risk factors for subsidence in patients undergoing ALIF.

METHODS

This study analyzed consecutive patients who underwent ALIF at a single institution with a minimum of 2 years follow-up. Patients were grouped as either Non-Subsidence (NS-ALIF) or Cage Subsidence (CS-ALIF) based on the final postoperative radiograph. Demographic variables, operative characteristics, and radiographic outcomes were evaluated to identify significant predictors on univariate and multivariate statistics.

RESULTS

144 patients (170 levels) were included with an average follow-up of 50.70 ± 28.44 months (4.23 years). The incidence of subsidence was 22.94% (39/170 levels). On univariate statistics, the CS-ALIF group was significantly older (P = .020), had higher BMI (P = .048), worse ASA (P = .001), higher prevalence of comorbid osteoporosis (P < .001), and a more anteriorly placed interbody device (P = .005). On multivariate analysis, anterior cage placement remained the only significant predictor (OR: 1.08, 95% CI: 1.03-1.14; P = .003). There was a significantly higher rate of subsequent adjacent segment surgery among the CS-ALIF group (P = .035).

CONCLUSION

Factors contributing to subsidence in ALIF included older age, higher BMI, severe ASA, and osteoporosis, while anterior cage placement remained the only independent predictor on multivariate analysis. Subsidence was associated with a higher rate of subsequent adjacent segment surgery. Surgical technique should optimize placement of the interbody cage and avoid overstuffing the disc space.

Who bleeds during elective anterior lumbar surgery?

Background

Blood loss (BL) during elective anterior lumbar access for interbody fusion or disc replacement is a potentially major complication. This study sought to identify factors other than major vascular injury which contribute to BL and therefore this risk. Factors suggested to effect blood loss include age, increasing body mass index (BMI), sex, prothesis, intraoperative heparinization and continuation of low-dose aspirin (LD-ASA).

Methods

A Cell Saver was used in all cases with BL measured and recorded by an independent autotransfusionist. Heparin was administered intravenously when one or both of 2ndtoe saturation metre signal/s lost pulsatility indicating lower limb arterial flow was interrupted.

Results

The mean age of the 364 patients was 47 ± 13.2 yrs. [95% CI: 45 - 48]; and 191 (52%) were male. Age, BMI and heparinization showed a positive correlation with increased BL. There was no significant association with continuation of low-dose ASA with increased BL. Most patients underwent an ALIF - 265 (72%), 52 (14%) had a TDR, and 47 (13%) had a hybrid operation. There was a significant increase in mean BL between single- and two-level procedures in the non-heparinised group (48 vs 83 mls, p = 0.003). Intraoperative heparinization was administered in 102 patients (28%). The total mean BL for the heparin group (104 ml) which was significantly higher than for the non-heparin group (53 ml) (p = 0.001). Heparinisation did not significantly increase the mean BL in single or double level ALIF patients but did significantly increase the BL in single level TDR (57 vs 151 mls, p = 0.039).

Conclusions

Younger, leaner, non-heparinized, single level ALIF patients represented the lowest bleeding risk in anterior lumbar surgery. Conversely, older, increasing BMI, two operative levels, TDR prosthesis and heparinization represent the highest bleeding risk. Continuation of LD-ASA was not associated with an increase in BL.

Obesity: An Independent Risk Factor for Complications in Anterior Lumbar Interbody Fusion? A Systematic Review

STUDY DESIGN

Systematic Review and Meta-analysis.

OBJECTIVES

Raised patient BMI is recognised as a relative contraindication to posterior lumbar interbody fusion (PLIF) due to the anaesthetic challenges, difficult positioning and increased intraoperative and postoperative complications, with the relative risk rising in patients with a BMI >25 kg/m2. The impact of obesity defined as a BMI > 30 kg/m² on Anterior Lumbar Interbody Fusion (ALIF) outcomes is not yet established. The aim of this review was to evaluate if the presence of a raised BMI in patients undergoing ALIF procedures was an independent risk factor for intra- and postoperative complications.

METHODS

A systematic review of search databases PubMed; Google Scholar and OVID Medline was made to identify studies related to complications in patients with increased body mass index during anterior lumbar interbody fusion. PRISMA guidelines were utilised for this review. Complication rates in raised BMI patient cohort was compared to normal BMI complication rates with meta-analysis where available.

RESULTS

315 articles returned with search criteria applied. Six articles were included for review, with 2190 patients included for analysis. Vascular complications in obese vs. non-obese patients undergoing the anterior approach demonstrate no significant difference in complication rates (P = .62; CI = -.03-.02). Obesity is found to result in an increased rate of overall complications (P = .002; CI = .04-.16).

CONCLUSIONS

Obesity was demonstrated to have an impact on overall complication rates in Anterior Lumbar Interbody Fusion procedures, with postoperative complications including wound infections and lower fusion rates more common in patients in increased BMIs. Increased focus on patient positioning and reporting of outcomes in this patient cohort is warranted to further evaluate perioperative complications.

Risk Assessment of Anterior Lumbar Interbody Fusion Access in Degenerative Spinal Conditions

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

Develop an evidence-based preoperative risk assessment scoring system for patients undergoing anterior lumbar interbody fusion (ALIF).

SUMMARY OF BACKGROUND DATA

ALIF may hold advantages over other fusion techniques in sagittal restoration and fusion rates, though it introduces unique risks to vascular and abdominal structures and thus possibly increased risk of operative morbidity.

METHODS

Primary, 1 or 2-level ALIFs were identified in a surgical registry. Baseline characteristics were recorded. Axial magnetic resonance imagings at L4-L5 and L5-S1 were reviewed for vascular confluence/bifurcation or anomalous structures, and measured for operative window size/slope. To assess favorable outcomes, a clinical grade was calculated: (clinical grade=blood loss×operative duration), higher value indicating poorer outcome. To establish a risk scoring system, a base risk score algorithm was established and stratified into 5 categories: high, high to intermediate, intermediate, intermediate to low, and low. Modifiers to base risk score included age, body mass index, operative level, history of bone morphogenic protein use, calcified vasculature, spondylolisthesis grade, working window size and slope, and abnormal vasculature. Modifiers were weighted for contribution to surgical risk. A total risk score was calculated and evaluated for strength of association with clinical outcome grades by Pearson correlation coefficient.

RESULTS

A total of 65 patients were included. Mean clinical outcome grade was 5.6, mean total risk score 21.3±21.5. Multilevel procedures (L4-S1) mean total risk score was 57.3±7.8. L4-L5 mean total risk score was 23.6±5.2; L5-S1 mean total risk score 8.3±6.6. Correlation analysis demonstrated a significant and strong relationship (| r |=0.753; P <0.001) between total risk scores and clinical outcome grades.

CONCLUSION

Calculated ALIF risk scores significantly correlated with operative duration and blood loss. This scoring system represents a potential framework to facilitate clinical decision-making and risk assessment for potential ALIF candidates with degenerative spinal pathologies.

Obesity Does Not Adversely Affect Long-term Outcomes of Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Matched Cohort Analysis

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is an established technique for the treatment of degenerative spine disease. The larger body habitus of obese patients increases the intraoperative complexity of MI-TLIF. Therefore, it is unclear whether this procedure is appropriate for this population. The goal of this study was to compare postoperative outcomes for obese patients vs nonobese patients undergoing MI-TLIF through a matched cohort analysis. A retrospective review was performed to identify patients who underwent MI-TLIF at a single institution with a minimum follow-up of 5 years. Patients were divided into 2 cohorts: nonobese (body mass index <30 kg/m²) and obese (body mass index ≥30 kg/m²). Each cohort was matched for age, sex, and levels operated. Perioperative data and patient-reported outcomes were compared. Radiographic outcomes were measured at final follow-up. Standard binomial and categorical comparative analyses were performed. A total of 148 patients were included. Of obese patients, 17.6% required revision surgery compared with 16.2% of nonobese patients (P=.826). Both cohorts had a similar proportion of pelvic incidence-lumbar lordosis mismatch correction (P=.780). Mean change in functional outcome scores for each cohort did not differ significantly. Obese patients had clinically minor but statistically significantly greater blood loss and longer operative times than nonobese patients (P<.001). Obese and non-obese patients undergoing MI-TLIF showed no long-term differences in revision rate, radiologic outcome, or functional outcome after long-term follow-up. Obese patients had slightly greater blood loss and longer operative times. Our findings suggest that MI-TLIF is an appropriate alternative to traditional open lumbar fusion for obese patients. [Orthopedics. 2022;45(4):203-208.].

Obesity and Spine Surgery: A Qualitative Review About Outcomes and Complications. Is It Time for New Perspectives on Future Researches?

STUDY DESIGN

Literature review.

OBJECTIVES

An increasing number of obese patients requires operative care for degenerative spinal disorders. The aim of this review is to analyze the available evidence regarding the role of obesity on outcomes after spine surgery. Peri-operative complications and clinical results are evaluated for both cervical and lumbar surgery. Furthermore, the contribution of MIS techniques for lumbar surgery to play a role in reducing risks has been analyzed.

METHODS

Only articles published in English in the last 10 years were reviewed. Inclusion criteria of the references were based on the scope of this review, according to PRISMA guidelines. Moreover, only paper analyzing obesity-related complications in spine surgery have been selected and thoroughly reviewed. Each article was classified according to its rating of evidence using the Sacket Grading System.

RESULTS

A total number of 1636 articles were found, but only 130 of them were considered to be relevant after thorough evaluation and according to PRISMA checklist. The majority of the included papers were classified according to the Sacket Grading System as Level 2 (Retrospective Studies).

CONCLUSION

Evidence suggest that obese patients could benefit from spine surgery and outcomes be satisfactory. A higher rate of peri-operative complications is reported among obese patients, especially in posterior approaches. The use of MIS techniques plays a key role in order to reduce surgical risks. Further studies should evaluate the role of multidisciplinary counseling between spine surgeons, nutritionists and bariatric surgeons, in order to plan proper weight loss before elective spine surgery.

Underweight patients are the highest risk body mass index group for perioperative adverse events following stand-alone anterior lumbar interbody fusion

BACKGROUND CONTEXT

Prior studies investigating the association between Body Mass Index (BMI) and patient outcomes following spine surgery have had inconsistent conclusions, likely owing to insufficient power, confounding variables, and varying definitions and cutoffs for BMI categories (eg, underweight, overweight, obese, etc.). Further, few studies have considered outcomes among low BMI cohorts.

PURPOSE

The current study analyzes how anterior lumbar interbody fusion (ALIF) perioperative outcomes vary along the BMI spectrum, using World Health Organization (WHO) categories of BMI.

STUDY DESIGN/SETTING

A retrospective cohort study.

PATIENT SAMPLE

Patients undergoing stand-alone one or two-level anterior lumbar interbody fusion (ALIF) found in the 2005-2018 American College of Surgeons National Surgical Quality Improvement Program (NSQIP) databases.

OUTCOME MEASURES

Thirty-day adverse events, hospital readmissions, post-operative infections, and mortality.

METHODS

Stand-alone one or two-level ALIF surgical cases were identified and extracted from the 2005-2018 National Surgical Quality Improvement Program (NSQIP) database. Posterior cases and those primary diagnoses of trauma, tumor, infection, or emergency presentation were excluded. Patients were then binned into WHO guidelines of BMI. The incidence of adverse outcomes within 30-day post-operation was defined. Odds ratios of adverse outcomes, normalized to the average risk of normal-weight subjects (BMI 18.5-24.9 kg/m³), were calculated. Multivariate analysis was then performed controlling for patient factors.

RESULTS

In total, 13,710 ALIF patients were included in the study. Incidence of adverse events was elevated in both the underweight (BMI<18.5 kg/m³) and super morbidly obese (>50 kg/m³), however, multivariate risks for adverse events and postoperative infection were elevated for underweight patients beyond those found in any other BMI category. No effect was noted in these identical variables between normal, overweight, obese class 1, or even obese class 2 patients. Multivariate analysis also found overweight patients to show a slightly protective trend against mortality while the super morbidly obese had elevated odds.

CONCLUSIONS

Underweight patients are at greater odds of experiencing postoperative adverse events than normal, overweight, obese class 1, or even obese class 2 patients. The present study identifies underweight patients as an at-risk population that should be given additional consideration by health systems and physicians, as is already done for those on the other side of the BMI spectrum.

Increased risk of postoperative wound complications among obesity classes II & III after ALIF in 10-year ACS-NSQIP analysis of 10,934 cases

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) procedures for lumbar spine disease have been increasing amid a growing obese patient population with limited studies available focusing exclusively on risk-factors for post-operative ALIF complications.

PURPOSE

The objective of this study was to compare 30-day post-operative complications among different obesity World Health Organization classes according to body mass index (BMI) in comparison to non-obese patients who underwent an ALIF procedure.

STUDY DESIGN/SETTING

Retrospective cohort study of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) from 2009 to 2019.

PATIENT SAMPLE

A total of 10,934 patients undergoing an ALIF.

OUTCOME MEASURES

Primary outcome measures include 30 day cardiac, pulmonary, urinary, infectious, and wound complications. Secondary outcomes included rates of blood transfusion, reintubation, deep vein thrombosis, pulmonary embolism, 30-day return to the operating room (OR), and 30 day mortality.

METHODS

Patients were identified by use of the current procedural terminology codes 22558 and 22585 from 2009 to 2019. Patients were divided into the following groups: non-obese (BMI 18.5-29.9 kg/m²), Obese I (BMI 30-34.9 kg/m²), Obese II (BMI 35-39.9 kg/m²), and Obese III (BMI ≥40 kg/m²). Age, gender, race, American Society of Anesthesiologists status, smoking status, hypertension requiring medication, steroid used, chronic obstructive pulmonary disease, history of a bleeding disorder, and diabetes was identified as risk factors after a univariate analysis conducted for demographic variables and pre-operative comorbidities. A multivariate logistic regression analysis was then performed to adjust for these preoperative risk factors and compare obesity classes I-III to non-obese patients.

RESULTS

Obesity classes II and III had a significant odds ratio (OR) for superficial infection (OR:2.7, 95%CI(1.7-4.5); OR:2.8, 95%CI(1.5-5.2) respectively), organ space infection (OR:3.8, 95%CI(1.6-7.4); OR:3.2, 95%CI(1.1-9.9) respectively), wound disruption (OR:2.8, 95%CI(1.1-7.4); OR:4.6, 95%CI(1.6-13.6) respectively), and total wound complication (OR:2.6, 95%CI(1.8-3.9); OR:3.4, 95%CI(2.2-5.4) respectively) following a multivariate logistic regression analysis.

CONCLUSIONS

Risk for post-operative wound complications following an ALIF were found to be significantly higher for obesity classes II-III in comparison to non-obese patients. These findings can further support the use of additional wound care in the perioperative setting for certain levels of obesity.

Morbidity and clinicoradiological outcomes of anterior lumbar arthrodesis using tantalum intervertebral implants

PURPOSE

The objective of this study was to assess the morbidity of Anterior Lumbar Interbody Fusion (ALIF) using an intervertebral tantalum implant. Tantulum is an extremely porous metallic material which possesses properties of osseointegration, osteoinduction and osteoconduction while offering superior primary stability, compared to other materials more commonly used (polyether ether ketone or PEEK, titanium). Perioperative morbidity, short-term functional outcomes (2 years) and radiographic impaction of implants were also analysed.

METHODS

This retrospective monocentric study involved 94 patients operated on between 2014 and 2017 for degenerative disc disease (75%), degenerative spondylolisthesis (3%) or isthmic lytic spondylolisthesis (22%). Sixty-five patients (69%) had isolated ("stand-alone") ALIF procedures, 24 (26%) with associated anterior osteosynthesis and 5 (5%) with associated posterior osteosynthesis. A Kaplan-Meier survival curve was established with surgical revision listed as the main criterion for failure. Perioperative complications were identified. The clinical evaluation at the last follow-up used a Visual Analogue Scale for radicular pain (VAS-R), for lumbar pain (VAS-L) and the Oswestry Disability Index (ODI) score. The impactions, assessed on x-rays, were divided into 2 groups according to severity in order to establish risk factors (RF).

RESULTS

The primary objective showed a 2-year survival rate of 94% (95% CI [0.88; 0.99]). Two patients had early surgical revision for impaction and 4 patients had late surgical revision for pseudarthrosis. The rate of perioperative complications was 8.5%, mostly due to vascular causes. At the average follow-up of 33 months (24-59), the clinical results were significantly improved and the impaction rate was 36% in the immediate postoperative period (IPO) and 47% at one year.

CONCLUSION

ALIF using an intervertebral tantalum implant is a reliable, reproducible and low morbidity technique. However, it is accompanied by a significant rate of immediate and secondary impaction but without any resounding influence on short-term clinical outcomes.

LEVEL OF EVIDENCE

IV.

Endplate volumetric bone mineral density is a predictor for cage subsidence following lateral lumbar interbody fusion: a risk factor analysis

BACKGROUND CONTEXT

It has been reported in previous studies that a decreased bone mineral density (BMD) as measured by dual X-ray absorptiometry (DXA) is associated with subsidence. However, there is limited research on the role of volumetric BMD (vBMD) as measured by quantitative computed tomography (QCT). Further, metabolic conditions such as obesity and type 2 diabetes have been associated with poor bone quality, but the impact of these metabolic conditions on on subsidence rates following lateral lumbar interbody fusion (LLIF) remains unclear. As such, risk factors for subsidence following LLIF is an area of ongoing research.

PURPOSE

The purpose of this study is to identify risk factors for subsidence following LLIF with a focus on metabolic conditions and vBMD as measured by QCT.

STUDY DESIGN/SETTING

Retrospective cohort study at a single academic institution.

PATIENT SAMPLE

Consecutive patients undergoing LLIF with or without posterior screws from 2014 to 2019 at a single academic institution who had a pre-operative CT and radiological imaging including radiographs or CT scans between 5 and 14 months post-operatively to assess for cage subsidence.

OUTCOME MEASURE

Subsidence prevalence following LLIF.

METHODS

We reviewed patients undergoing LLIF with or without posterior screws from 2014 to 2019 with a follow-up ≥5 months. Cage subsidence was assessed using the grading system by Marchi et al. Endplate volumetric BMD (EP-vBMD), vertebral bone volumetric BMD (VB-vBMD), BMI, and diabetes status were measured. Univariable analysis and multivariable logistic regression analyses with a generalized mixed model were conducted. Ad hoc analysis, including receiver operative characteristic curve analysis, was used for identifying the cut-off values in significant continuous variables for subsidence. Chi-Squared and ANOVA tests were used for categorical comparisons.

RESULTS

Five hundred sixty-seven levels in 347 patients were included in the final analysis. Mean age (± SD) was 61.7 ± 11.1yrs, 50.3% were male, and 89.6% were Caucasian. Subsidence was observed in 160 levels (28.2%). Multivariable analysis demonstrated an absence of posterior screws [OR = 2.854 (1.483 - 5.215), p=.001] and decreased EP-vBMD [0.996 (0.991 - 1.000), p=.032] were associated with an increased risk of subsidence. Increased BMI and diabetes status were not associated with increased rates of subsidence. Patients without posterior screws and low EP-vBMD experienced subsidence at 44.9% of levels.

CONCLUSIONS

Our results demonstrated that decreased EP-vBMD and standalone status were significantly associated with increased rates of subsidence following LLIF independent of BMI or diabetes status. Further analysis demonstrated that patients with a decreased EP-vBMD and without posterior screws experienced subsidence nearly 2.5 times higher than patients with no risk factors. In patients with a low EP-vBMD undergoing LLIF, posterior screws should be considered.

Factors Affecting Postoperative Length of Stay in Patients Undergoing Anterior Lumbar Interbody Fusion

BACKGROUND

With hospital leaders and policy makers increasingly seeking ways to improve resource use, there has been heightened interest in reducing hospital length of stay (LOS) and performing spine procedures on an outpatient basis. We aimed to determine which risk factors correlated with prolonged LOS after anterior lumbar interbody fusion (ALIF).

METHODS

Medical records for patients who underwent ALIF were retrospectively reviewed. Patients were divided into those who had extended (≥3 days) versus nonextended (<3 days) LOS, and patient demographics, medical comorbidities, and preoperative medications were analyzed. Univariate and multivariate regression were then used to determine preoperative risk factors for extended LOS.

RESULTS

A total of 166 patients were included (mean age, 48.7 years). Medical comorbidities included hypertension (31.9%), diabetes (8.4%), and obesity (body mass index >30 kg/m²) (48.8%). LOS was not extended in 121 patients and extended in 45. Mean LOS was 2.2 days (95% confidence interval, 1.9-2.5). On multivariate logistic analysis, age ≥65 years (P = 0.001), preoperative benzodiazepine use (P = 0.014), 12-item Short Form mental component score (P = 0.008), estimated blood loss (P = 0.015), time to mobilization (P < 0.001), and total operative time (P = 0.020) were independent predictors for extended LOS.

CONCLUSIONS

As attempts are made to perform more spine procedure in ambulatory surgical centers, strict patient selection criteria are all critical in making this possible. Our results suggest that age, preoperative benzodiazepine use, higher intraoperative blood loss, delayed mobilization, and lower 12-item Short Form mental component score were correlated with increased LOS. Therefore, inpatient ALIF may be more suitable for patients with these risk factors.

[Advances in research on Cage subsidence following lumbar interbody fusion]

Objective

To summarize the advances in research on Cage subsidence following lumbar interbody fusion, and provide reference for its prevention.

Methods

The definition, development, clinical significance, and related risk factors of Cage subsidence following lumbar interbody fusion were throughout reviewed by referring to relevant domestic and doreign literature in recent years.

Results

At present, there is no consensus on the definition of Cage subsidence, and mostly accepted as the disk height reduction greater than 2 mm. Cage subsidence mainly occurs in the early postoperative stage, which weakens the radiological surgical outcome, and may further damage the effectiveness or even lead to surgical failure. Cage subsidence is closely related to the Cage size and its placement location, intraoperative endplate preparation, morphological matching of disk space to Cage, bone mineral density, body mass index, and so on.

Conclusion

The appropriate size and shape of the Cage usage, the posterolateral Cage placed, the gentle endplate operation to prevent injury, the active perioperative anti-osteoporosis treatment, and the education of patients to control body weight may help to prevent Cage subsidence and ensure good surgical results.

Three- and 4-Level Lumbar Arthrodesis Using Adjunctive Pulsed Electromagnetic Field Stimulation: A Multicenter Retrospective Evaluation of Fusion Rates and a Review of the Literature

BACKGROUND

The incidence of 3- and 4-level lumbar arthrodesis is rising due to an aging population, and fusion rates affect clinical success in this population. Pulsed electromagnetic field (PEMF) stimulation is used as an adjunct to increase fusion rates following multilevel arthrodesis. The purpose of the study was to evaluate the fusion rates for subjects who underwent 3- and 4-level lumbar interbody arthrodesis following PEMF treatment.

METHODS

In this retrospective, multicenter study, patient charts that listed 3- or 4-level lumbar arthrodesis with adjunctive use of a PEMF device were evaluated. Inclusion criteria included patients who were diagnosed with lumbar degenerative disease, spinal stenosis, and/or spondylolisthesis (grade 1 or 2). A radiographic evaluation of fusion status was performed at 12 months by the treating physicians. Fusion rates were stratified by graft material, surgical interbody approach, and certain clinical risk factors for pseudoarthrosis.

RESULTS

A total of 55 patients were identified who had a 12-month follow-up. The radiographic fusion rate was 92.7% (51 patients) at 12 months. There were no significant differences in fusion rates for patients treated with allograft or autograft, for patients with different interbody approaches, or for those with or without certain clinical risk factors.

CONCLUSIONS

With modern fusion techniques and PEMF, the overall fusion rate was high following 3- and 4-level lumbar arthrodesis.

LEVEL OF EVIDENCE

4.

CLINICAL RELEVANCE

PEMF may be a useful adjunct for treatment of patients with surgical risk factors, such as multilevel arthrodesis, and clinical risk factors.

Implications of sagittal alignment and complication profile with stand-alone anterior lumbar interbody fusion versus anterior posterior lumbar fusion

Background

Anterior lumbar interbody fusion (ALIF) is commonly utilized in lumbar degenerative pathologies. Standalone ALIF (ST-ALIF) systems were developed to avoid added morbidity, surgical time, and cost of anterior and posterior fusion (APF). Controversy exists in the literature about which of these two techniques yields superior clinical and radiographic outcomes, and few studies have directly compared them. This study seeks to compare ST-ALIF and APF in terms of sagittal correction and surgical complications.

Methods

Ninty-two consecutive ALIF cases performed from 2013-2018 were retrospectively reviewed and separated into 2 groups. Radiographic measurements were performed on pre- and post-operative radiographs, including segmental lordosis (SL), lumbar lordosis (LL), and pelvic incidence-lumbar lordosis mismatch (PI-LL). Surgical complications were determined. Statistical analysis was performed using chi-square test of homogeneity, Fisher's exact test, and independent sample t-test. Comparisons between groups were deemed statistically significant at the P<0.05 threshold.

Results

Fifty-seven ST-ALIF, 35 APF were identified. There were no differences in age, gender, BMI, Charlson Comorbidity Index (CCI), preoperative diagnosis, or surgical level between the 2 cohorts. Bone Morphogenetic Protein (BMP) was utilized in 24.6% of ST-ALIF versus none of APF (P=0.001). No differences were detected in SL, LL, and PI-LL mismatch. ST-ALIF cohort had significantly greater risk of subsidence and revision surgery versus APF (12.3% vs. 0%, RD 95% CI: 3.8-20.8%, P=0.042). Recurrent spondylolisthesis occurred in 5 ST-ALIF cases, 3 cases with implant failure, and 2 nonunions versus none in the APF group.

Conclusions

ST-ALIF was associated with significantly greater subsidence and revision surgery versus APF. Careful patient selection is paramount when considering ST-ALIF. The potential for revision surgery may offset the potential benefit in avoiding posterior fusion. Despite the greater risk of subsidence, sagittal alignment was not significantly affected.

Predictors of inpatient admission in the setting of anterior lumbar interbody fusion: a Minimally Invasive Spine Study Group (MISSG) investigation

OBJECTIVE

While the anterior lumbar interbody fusion (ALIF) procedure may be amenable to ambulatory surgery, it has been hypothesized that limitations such as the risk of postoperative ileus and vascular complications have hindered transition of this procedure to the outpatient setting. Identification of independent risk factors predisposing patients to inpatient stays of ≥ 24 hours after ALIF may facilitate better postsurgical outcomes, target modifiable risk factors, and assist in the development of screening tools to transition appropriate patients to the ambulatory surgery center (ASC) setting for this procedure. The purpose of this study was to identify the most relevant risk factors that predispose patients to ≥ 24-hour admission following ALIF.

METHODS

A prospectively maintained surgical registry was reviewed for patients undergoing single ALIF between May 2006 and December 2019. Demographics, preoperative diagnosis, perioperative variables, and postoperative complications were evaluated according to their relative risk (RR) elevation for an inpatient stay of ≥ 24 hours. A Poisson regression model was used to evaluate predictors of inpatient stays of ≥ 24 hours. Risk factors for inpatient admission of ≥ 24 hours were identified with a stepwise backward regression model.

RESULTS

A total of 111 patients underwent single-level ALIF (50.9% female and 52.6% male, ≤ 50 years old). Eleven (9.5%) patients were discharged in < 24 hours and 116 remained admitted for ≥ 24 hours. The average inpatient stay was > 2 days (53.7 hours). The most common postoperative complications were fever (body temperature ≥ 100.4°F; n = 4, 3.5%) and blood transfusions (n = 4, 3.5%). Bivariate analysis revealed a preoperative diagnosis of retrolisthesis or lateral listhesis to elevate the RR for an inpatient stay of ≥ 24 hours (RR 1.11, p = 0.001, both diagnoses). Stepwise multivariate analysis demonstrated significant predictors for inpatient stays of ≥ 24 hours to be an operation on L4-5, coexisting degenerative disc disease (DDD) with foraminal stenosis, and herniated nucleus pulposus (RR 1.11, 95% CI 1.03-1.20, p = 0.009, all covariates).

CONCLUSIONS

This study provides data regarding the incidence of demographic and perioperative characteristics and postoperative complications as they pertain to patients undergoing single-level ALIF. This preliminary investigation identified the most relevant risk factors to be considered before appropriately transitioning ALIF procedures to the ASC. Further studies of preoperative characteristics are needed to elucidate ideal ASC ALIF patients.

The impact of obesity on perioperative complications in patients undergoing anterior lumbar interbody fusion

OBJECTIVE

Anterior approaches to the lumbar spine provide wide exposure that facilitates placement of large grafts with high fusion rates. There are limited data on the effects of obesity on perioperative complications.

METHODS

Data from consecutive patients undergoing anterior lumbar interbody fusion (ALIF) from 2007 to 2016 at a single academic center were analyzed. The primary outcome was any perioperative complication. Complications were divided into those occurring intraoperatively and those occurring postoperatively. Multivariate logistic regression was used to assess the association of obesity and other variables with these complications. An estimation table was used to identify a body mass index (BMI) threshold associated with increased risk of postoperative complication.

RESULTS

A total of 938 patients were identified, and the mean age was 57 years; 511 were females (54.5%). The mean BMI was 28.7 kg/m2, with 354 (37.7%) patients classified as obese (BMI ≥ 30 kg/m2). Forty patients (4.3%) underwent a lateral transthoracic approach, while the remaining 898 (95.7%) underwent a transabdominal retroperitoneal approach. Among patients undergoing transabdominal retroperitoneal ALIF, complication rates were higher for obese patients than for nonobese patients (37.0% vs 28.7%, p = 0.010), a difference that was driven primarily by postoperative complications (36.1% vs 26.0%, p = 0.001) rather than intraoperative complications (3.2% vs 4.3%, p = 0.416). Obese patients had higher rates of ileus (11.7% vs 7.2%, p = 0.020), wound complications (11.4% vs 3.4%, p < 0.001), and urinary tract infections (UTI) (5.0% vs 2.5%, p = 0.049). In a multivariate model, age, obesity, and number of ALIF levels fused were associated with an increased risk of postoperative complication. An estimation table including 19 candidate cut-points, odds ratios, and adjusted p values found a BMI ≥ 31 kg/m2 to have the highest association with postoperative complication (p = 0.012).

CONCLUSIONS

Obesity is associated with increased postoperative complications in ALIF, including ileus, wound complications, and UTI. ALIF is a safe and effective procedure. However, patients with a BMI ≥ 31 kg/m2 should be counseled on their increased risks and warrant careful preoperative medical optimization and close monitoring in the postoperative setting.

Complexities of spine surgery in obese patient populations: a narrative review

The obese population is particularly challenging to the spine surgeon in all phases of care. A narrative literature review was performed to review difficulties in spine surgery on the obese patient population and techniques for mitigation. We specifically aimed to assess several topics with regard to this population: patient selection and preoperative care; intraoperative and surgical techniques; and postoperative care, outcomes, and complications. The literature review demonstrated that obese patients are at increased surgical risk with spine surgery due to a variety of factors at all stages of intervention. Preoperatively, obese patients have worse outcomes with physical therapy and present technical difficulties for injections. Transport to a hospital, imaging, resuscitation, and intubation are all challenged by increased body habitus. Intraoperatively, obese patients have increased operative times, blood loss, surgical site infections, and nerve palsies. Patient positioning and intraoperative imaging may be limited. Surgery itself may be technically challenging due to body habitus and minimally invasive techniques are becoming more prevalent in this population. Postoperatively, several studies demonstrate that obese patients have inferior outcomes compared with nonobese counterparts. Patient selection is a key for elective interventions, and appropriate infrastructure aids in the ultimate outcomes for both elective and nonelective surgical treatments. Overall, obese patients present several challenges to the spine surgeon, and certain precautions can be undertaken preoperatively, intraoperatively, and postoperatively to mitigate the associated risks to optimize outcomes.

The effect of obesity on perioperative morbidity in oblique lumbar interbody fusion

OBJECTIVE

Obese patients have been shown to have longer operative times and more complications from surgery. However, for obese patients undergoing minimally invasive surgery, these differences may not be as significant. In the lateral position, it is thought that obesity is less of an issue because gravity pulls the visceral fat away from the spine; however, this observation is primarily anecdotal and based on expert opinion. The authors performed oblique lumbar interbody fusion (OLIF) and they report on the perioperative morbidity in obese and nonobese patients.

METHODS

The authors conducted a retrospective review of patients who underwent OLIF performed by 3 spine surgeons and 1 vascular surgeon at the University of California, San Francisco, from 2013 to 2018. Data collected included demographic variables; approach-related factors such as operative time, blood loss, and expected temporary approach-related sequelae; and overall complications. Patients were categorized according to their body mass index (BMI). Obesity was defined as a BMI ≥ 30 kg/m2, and severe obesity was defined as a BMI ≥ 35 kg/m2.

RESULTS

There were 238 patients (95 males and 143 females). There were no significant differences between the obese and nonobese groups in terms of sex, levels fused, or smoking status. For the entire cohort, there was no difference in operative time, blood loss, or complications when comparing obese and nonobese patients. However, a subset analysis of the 77 multilevel OLIFs that included L5-S1 demonstrated that the operative times for the nonobese group was 223.55 ± 57.93 minutes, whereas it was 273.75 ± 90.07 minutes for the obese group (p = 0.004). In this subset, the expected approach-related sequela rate was 13.2% for the nonobese group, whereas it was 33.3% for the obese group (p = 0.039). However, the two groups had similar blood loss (p = 0.476) and complication rates (p = 0.876).

CONCLUSIONS

Obesity and morbid obesity generally do not increase the operative time, blood loss, approach-related sequelae, or complications following OLIF. However, obese patients who undergo multilevel OLIF that includes the L5-S1 level do have longer operative times or a higher rate of expected approach-related sequelae. Obesity should not be considered a contraindication to multilevel OLIF, but patients should be informed of potentially increased morbidity if the L5-S1 level is to be included.

The Impact of Body Mass Index (BMI) on 30-day Outcomes Following Posterior Spinal Fusion in Neuromuscular Scoliosis

STUDY DESIGN

Retrospective.

OBJECTIVE

Assess the impact of varying severity of BMI on 30-day outcomes following posterior spinal fusions in neuromuscular scoliosis.

SUMMARY OF BACKGROUND DATA

Obesity in the pediatric population is shown to be associated with adverse outcomes across varying specialties. The weight-outcome relationship in neuromuscular scoliosis has not been thoroughly investigated.

METHODS

The 2012-2016 American College of Surgeons - National Surgical Quality Improvement (ACS-NSQIP) database was queried using Current Procedural Terminology codes 22800, 22802, and 22804 to identify patients undergoing posterior spinal fusion for neuromuscular scoliosis only. BMI was classified into four groups based on the Center for Disease Control (CDC) BMI-for-age percentile chart - Normal weight (BMI ≥5th to <85th percentile), Underweight (<5th percentile), Overweight (≥85th to <95th percentile) and Obese (≥95th percentile). Multivariate regression models were built to understand the impact of varying BMI severity classes on 30-day outcomes.

RESULTS

A total of 1291 patients underwent posterior spinal fusion for neuromuscular scoliosis. A total of 695 (53.8%) were normal weight, 286 (22.2%) were underweight, 145 (11.2%) were overweight, and 165 (12.8%) were obese. Obese patients versus normal weight patients were at a significantly higher risk of surgical site infections (OR 2.15; P = 0.035), wound dehiscence (OR 1.58; P = 0.037), urinary tract infections (OR 3.41; P = 0.010), and 30-day readmissions (OR 1.94; P = 0.029). Of note, overweight versus normal weight individuals had higher odds of cardiopulmonary complications (OR 8.82; P = 0.024). No significant associations were seen for varying BMI and other 30-day outcomes.

CONCLUSIONS

Obese neuromuscular patients undergoing PSF have higher odds of experiencing adverse outcomes, particularly surgical site infections, urinary tract infections, and readmissions. Providers should promote prevention strategies, such as dietary modification and/or early physical activity in these high-risk patients to minimize the risks of experiencing complications in the acute postoperative period.

LEVEL OF EVIDENCE

3.

Obesity does not impact clinical outcome but affects cervical sagittal alignment and adjacent segment degeneration in short term follow-up after an anterior cervical decompression and fusion

BACKGROUND CONTEXT

Obesity increases complications and cost following spine surgery. However, the impact on sagittal alignment and adjacent segment degeneration (ASD) after anterior cervical decompression and fusion is less understood.

PURPOSE

To compare clinical and radiographic outcomes after anterior cervical decompression and fusion between obese and nonobese patients.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

In all, 467 patients that underwent an anterior cervical decompression and fusion procedure from January 2008 through December 2015 were assessed. Surgery indications were radiculopathy, myelopathy, or myeloradiculopathy that had failed nonoperative treatments. Exclusion criteria included patients who had postoperative follow-up less than 6 months. Of 467 patients originally identified, 399 fulfilled the inclusion and exclusion criteria.

OUTCOME MEASURES

The following patient-reported outcomes were obtained: Neck Disability Index and Visual Analog Scale scores for the neck and arm pain. Radiographic assessments included: C2-C7 lordosis, T1 angle, levels fused, sagittal vertical axis (SVA), fusion mass lordosis, proximal and distal adjacent segment lordosis, ASD, and presence of fusion.

METHODS

Plain radiographs were performed preoperatively, immediately postoperatively, and final follow-up. Demographic information was collected on all patients. Baseline patient characteristics were compared using chi-squared analysis and independent sample t tests for categorical and continuous data, respectively. For analysis, patients were divided into 4 groups based on obesity stratification as defined by Center for Disease Control: body mass index (BMI) <25 kg/m² (normal weight), BMI≥25 kg/m² to <30 kg/m² (overweight), ≥30 kg/m² to <35 kg/m² (Class I obesity), BMI≥35 kg/m² to <40 kg/m² (Class II obesity), and BMI≥40 kg/m² (Class III obesity). Additionally, obese (≥30 kg/m²) and nonobese (<30 kg/m²) patients were compared in a separate analysis. Multivariate analysis was used to compare clinical and radiographic outcomes among all BMI classes, as well as between BMI≥30 kg/m² versus BMI<30 kg/m² study groups. Multivariate analyses controlled for differences in baseline patient characteristics and included age, sex, smoking, American Society of Anesthesiologists Physical Status Score, diabetes mellitus, and number of levels.

RESULTS

Of the 399 patients assessed, 97 were identified as normal weight, 157 as overweight, 81 with Class I obesity, 45 with Class II obesity, and 19 with Class III obesity. On multivariate analysis, despite having similar SVA measurements on preoperative radiographs, increase in BMI was associated with increase in postoperative SVA (p=0.041) along with significantly larger SVA in immediate postoperative (p=0.004) and final follow-up radiographs (p=0.003) for patients with BMI≥30 kg/m² versus BMI<30 kg/m². Furthermore, patients with BMI≥30 kg/m² had smaller preoperative (p=0.012), immediate postoperative (p=0.017), and final lordosis (p<0.001) in addition to smaller immediate postoperative (p=0.025) and final fusion segment lordosis (p=0.015) and smaller preoperative (p=0.024) and final distal lordosis (p=0.021) compared with patients with BMI<30 kg/m². Additionally, greater BMI was associated with lower final Visual Analog Scale neck scores (p=0.008). Radiographic early ASD rates were higher in patients BMI≥30 kg/m² versus BMI<30 kg/m² (p=0.028).

CONCLUSIONS

Overall, obese patients who underwent anterior cervical decompression and fusion had similar patient-reported outcomes compared with nonobese patients but had worse radiographic parameters and higher rates of ASD development compared with nonobese patients. This underscores the importance of patient selection and surgical approach for both patient populations.

The Influence of Body Mass Index on Functional Outcomes, Satisfaction, and Return to Work After Single-level Minimally-invasive Transforaminal Lumbar Interbody Fusion: A Five-year Follow-up Study

STUDY DESIGN

Retrospective study using prospectively collected registry data.

OBJECTIVES

To evaluate the effect of obesity on patient-reported outcome measures of pain, disability, quality of life, satisfaction, and return to work after single-level minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

SUMMARY OF BACKGROUND DATA

MIS-TLIF is an appealing alternative for obese patients with potentially lower complication risk. However, there is limited data investigating the influence of obesity on outcomes 5 years after MIS-TLIF.

METHODS

Prospectively collected registry data of 296 patients who underwent single-level MIS-TLIF at a single institution were reviewed. Patients had complete 2- and 5-year follow-up data. Patients were stratified into control (<25.0 kg/m), overweight (25.0-29.9 kg/m), and obese (≥30.0 kg/m) groups. Outcomes assessed were visual analogue scale for back pain, leg pain, Oswestry Disability Index, Short-form 36, North American Spine Society score for neurogenic symptoms, return to work (RTW), return to function (RTF), satisfaction, and expectation fulfilment. Length of operation, length of stay, and comorbidities were recorded.

RESULTS

Among the patients, 156 (52.7%) had normal weight, 108 (36.5%) were overweight, and 32 (10.8%) were obese. There was no difference in length of operation or hospitalization (P > 0.05). All three groups had comparable preoperative scores at baseline (P > 0.05). At 5 years, the control group had significantly higher PCS compared with the overweight (P = 0.043) and obese groups (P = 0.007), although the change in scores was similar (P > 0.05). The rate of MCID attainment, RTW, RTF, expectation fulfilment, and satisfaction was comparable.

CONCLUSION

Nonobese patients had better physical well-being in the mid-term, although obese patients experienced a comparable improvement in clinical scores. Obesity had no impact on patients' ability to RTW or RTF. Equivalent proportions of patients were satisfied and had their expectations fulfilled up to 5 years after MIS-TLIF.

LEVEL OF EVIDENCE

3.

Outcomes of direct lateral interbody fusion (DLIF) in an Australian cohort

Background

Direct lateral interbody fusion (DLIF) mitigates many of the vascular complications and bony resections associated with other interbody fusion techniques. However, there are concerns regarding postoperative neural complications and that indirect decompression of the foramen has not been consistently demonstrated. This study prospectively assessed the clinical and radiological outcomes and the complication rates of the DLIF approach.

Methods

A prospective review was conducted of the first 50 consecutive DLIF cases of a single neurosurgeon between 2010 and 2014. Clinical outcomes were assessed using Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) and Roland Morris Disability Questionnaire (RMDQ) surveys. Radiological outcomes, including spondylolisthesis, disc height, local disc angle, lumbar lordosis and foraminal height and width, were measured using Surgimap Spine software at the preoperative, 6 weeks, 6 months, and 12 months postoperative follow-up. Complication rates were also reported.

Results

A total of 50 patients (84 levels) were treated with DLIF. The mean patient age was 68.2±9.8 years and 62.0% were female. At latest follow-up, mean VAS pain score improved from 7.7±1.5 to 1.9±0.9 (P<0.0001), mean ODI improved from 42.1±14.5 to 16.9±6.7 (P<0.0001) and mean RMDQ score improved from 12.1±5.2 to 6.2±4.7 (P<0.0001). Mean spondylolisthesis reduced from 7.5%±6.5% to 1.3%±1.1% at 6 weeks (P<0.0001), 0.95%±0.74% at 6 months (P<0.0001) and recurred to 1.9%±1.7% at 12 months postoperatively (P=0.0006). Mean anterior disc height improved from 7.3±3.2 to 11.6±2.5 mm at 6 weeks (P<0.0001), 12.2±3.3 mm at 6 months (P<0.0001) and 9.8±2.1 mm at 12 months (P=0.0032) postoperatively. Mean posterior disc height improved from 4.4±2.0 to 6.8±2.1 mm at 6 weeks (P<0.0001), 6.6±2.5 mm at 6 months (P=0.0003), and 5.9±1.4 mm at 12 months (P=0.0039) postoperatively. Mean local disc angle improved from 7.0°±3.7° to 9.2°±3.3° at 6 weeks (P=0.0072), 10.4°±3.9° at 6 months (P=0.0013) and 8.2°±2.9° at 12 months (P=0.2487) postoperatively. No significant postoperative changes in lumbar lordosis were observed. Mean foraminal height improved from 18.3±3.5 to 21.5±3.9 mm at 6 weeks (P=0.0004), 20.6±3.4 mm at 6 months (P=0.0266), and 18.7±1.9 mm at 12 months (P=0.8021) postoperatively. Mean foraminal width improved from 7.9±2.0 to 10.2±2.8 mm at 6 weeks (P=0.0001), 9.4±2.6 mm at 6 months (P=0.0219) and 8.3±1.6 mm at 12 months (P=0.5734) postoperatively. Fusion rate at 6 and 12 months was 62.2% and 89.2%, respectively. A total of 6 patients (12%) had postoperative complications. Three patients (6%) had pain-related psoas muscle weakness and 3 patients (6%) had sensory neural complications that had resolved entirely by 8 and 16 weeks postoperatively, respectively.

Conclusions

The study provides encouraging short and medium-term clinical and radiological results for DLIF. In this patient series, there was a low complication rate with no permanent neural injury reported.