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Gautam Nayar, Souvik Roy, Waseem Lutfi, Nitin Agarwal, Nima Alan, Alp Ozpinar, D. Kojo Hamilton, David O. Okonkwo, and Adam S. Kanter

OBJECTIVE

Adjacent-segment disease (ASD) requiring operative intervention is a relatively common long-term consequence of lumbar fusion surgery. Although the incidence of ASD requiring reoperation is well described for traditional posterior lumbar approaches (2.5%–3.9% per year), it remains poorly characterized for stand-alone lateral lumbar interbody fusion (LLIF). In this study, the authors report their institutional experience with ASD requiring reoperation after LLIF over an extended follow-up period of 4 years.

METHODS

Medical records were reviewed for 276 consecutive patients who underwent stand-alone LLIF by a single surgeon for degenerative spinal disorders. Inclusion criteria (single-stage, stand-alone LLIF without posterior supplementation, with no prior lumbar instrumentation, and a minimum of 4 years of follow-up) were met by 182 patients, who were analyzed for operative ASD incidence (per-year rate), demographics, and Oswestry Disability Index (ODI) score. Operative ASD was strictly defined as new-onset pathology following index surgery at directly adjacent levels to the prior construct. Operative, rather than symptomatic or radiographic, ASD was analyzed to provide a consistent and impactful endpoint while avoiding retrospective diagnosis.

RESULTS

The study cohort of 182 patients had an operative ASD rate of 3.3% (n = 6 procedures) over 4 years of follow-up, for an incidence on Kaplan-Meier survival analysis of 0.88% (95% CI 0.67%–1.09%) per year. In comparing patients with operative ASD with those without, there were no significant differences in mean age (53.7 vs 56.2 years), male sex (33.3% vs 44.9%), smoking status (16.7% vs 25.0%), or number of levels fused (mean 1.33 vs 1.46). The operative ASD cohort had a greater mean BMI (37.3 vs 30.2, p < 0.01). Operative ASD patients had lower baseline ODI scores (33.8 vs 48.3, p = 0.02); however, no difference was observed in ODI at 6 weeks (34.0 vs 39.0) or 3 months (16.0 vs 32.8) postoperatively.

CONCLUSIONS

The incidence of ASD in LLIF for degenerative lumbar etiologies in this cohort was 0.88% (95% CI 0.67%–1.09%) per year. Meanwhile, the reported reoperation rates for ASD in posterior spinal approaches was 2.5% to 3.9% per year, which implies that LLIF may be preferable for well-selected patients.

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Nitin Agarwal, Michael D. White, Xiaoran Zhang, Nima Alan, Alp Ozpinar, David J. Salvetti, Zachary J. Tempel, David O. Okonkwo, Adam S. Kanter, and D. Kojo Hamilton

OBJECTIVE

Stand-alone lateral lumbar interbody fusion (LLIF) is a useful minimally invasive approach for select spinal disorders, but implant subsidence may occur in up to 30% of patients. Previous studies have suggested that wider implants reduce the subsidence rate. This study aimed to evaluate whether a mismatch of the endplate and implant area can predict the rate and grade of implant subsidence.

METHODS

The authors conducted a retrospective review of prospectively collected data on consecutive patients who underwent stand-alone LLIF between July 2008 and June 2015; 297 patients (623 surgical levels) met inclusion criteria. Imaging studies were examined to grade graft subsidence according to Marchi criteria. Thirty patients had radiographic evidence of implant subsidence. The endplates above and below the implant were measured.

RESULTS

A total of 30 patients with implant subsidence were identified. Of these patients, 6 had Marchi grade 0, 4 had grade I, 12 had grade II, and 8 had grade III implant subsidence. There was no statistically significant correlation between the endplate-implant area mismatch and subsidence grade or incidence. There was also no correlation between endplate-implant width and length mismatch and subsidence grade or incidence. However, there was a strong correlation between the usage of the 18-mm-wide implants and the development of higher-grade subsidence (p = 0.002) necessitating surgery. There was no significant association between the degree of mismatch or Marchi subsidence grade and the presence of postoperative radiculopathy. Of the 8 patients with 18-mm implants demonstrating radiographic subsidence, 5 (62.5%) required reoperation. Of the 22 patients with 22-mm implants demonstrating radiographic subsidence, 13 (59.1%) required reoperation.

CONCLUSIONS

There was no correlation between endplate-implant area, width, or length mismatch and Marchi subsidence grade for stand-alone LLIF. There was also no correlation between either endplate-implant mismatch or Marchi subsidence grade and postoperative radiculopathy. The data do suggest that the use of 18-mm-wide implants in stand-alone LLIF may increase the risk of developing high-grade subsidence necessitating reoperation compared to the use of 22-mm-wide implants.

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Lateral lumbar interbody fusion in the elderly: a 10-year experience

Presented at the 2018 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Nitin Agarwal, Andrew Faramand, Nima Alan, Zachary J. Tempel, D. Kojo Hamilton, David O. Okonkwo, and Adam S. Kanter

OBJECTIVE

Elderly patients, often presenting with multiple medical comorbidities, are touted to be at an increased risk of peri- and postoperative complications following spine surgery. Various minimally invasive surgical techniques have been developed and employed to treat an array of spinal conditions while minimizing complications. Lateral lumbar interbody fusion (LLIF) is one such approach. The authors describe clinical outcomes in patients over the age of 70 years following stand-alone LLIF.

METHODS

A retrospective query of a prospectively maintained database was performed for patients over the age of 70 years who underwent stand-alone LLIF. Patients with posterior segmental fixation and/or fusion were excluded. The preoperative and postoperative values for the Oswestry Disability Index (ODI) were analyzed to compare outcomes after intervention. Femoral neck t-scores were acquired from bone density scans and correlated with the incidence of graft subsidence.

RESULTS

Among the study cohort of 55 patients, the median age at the time of surgery was 74 years (range 70–87 years). Seventeen patients had at least 3 medical comorbidities at surgery. Twenty-three patients underwent a 1-level, 14 a 2-level, and 18 patients a 3-level or greater stand-alone lateral fusion. The median estimated blood loss was 25 ml (range 5–280 ml). No statistically significant relationship was detected between volume of blood loss and the number of operative levels. The median length of hospital stay was 2 days (range 1–4 days). No statistically significant relationship was observed between the length of hospital stay and age at the time of surgery. There was one intraoperative death secondary to cardiac arrest, with a mortality rate of 1.8%. One patient developed a transient femoral nerve injury. Five patients with symptomatic graft subsidence subsequently underwent posterior instrumentation. A lower femoral neck t-score < −1.0 correlated with a higher incidence of graft subsidence (p = 0.006). The mean ODI score 1 year postoperatively of 31.1 was significantly (p = 0.003) less than the mean preoperative ODI score of 46.2.

CONCLUSIONS

Stand-alone LLIF can be safely and effectively performed in the elderly population. Careful evaluation of preoperative bone density parameters should be employed to minimize risk of subsidence and need for additional surgery. Despite an association with increased comorbidities, age alone should not be a deterrent when considering stand-alone LLIF in the elderly population.

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Jonathan Cohen, Nima Alan, James Zhou, and D. Kojo Hamilton

OBJECTIVE

Despite the growing neurosurgical literature, a subset of pioneering studies have significantly impacted the field of metastatic spine disease. The purpose of this study was to identify and analyze the 100 most frequently cited articles in the field.

METHODS

A keyword search using the Thomson Reuters Web of Science was conducted to identify articles relevant to the field of metastatic spine disease. The results were filtered based on title and abstract analysis to identify the 100 most cited articles. Statistical analysis was used to characterize journal frequency, past and current citations, citation distribution over time, and author frequency.

RESULTS

The total number of citations for the final 100 articles ranged from 74 to 1169. Articles selected for the final list were published between 1940 and 2009. The years in which the greatest numbers of top-100 studies were published were 1990 and 2005, and the greatest number of citations occurred in 2012. The majority of articles were published in the journals Spine (15), Cancer (11), and the Journal of Neurosurgery (9). Forty-four individuals were listed as authors on 2 articles, 9 were listed as authors on 3 articles, and 2 were listed as authors on 4 articles in the top 100 list. The most cited article was the work by Batson (1169 citations) that was published in 1940 and described the role of the vertebral veins in the spread of metastases. The second most cited article was Patchell's 2005 study (594 citations) discussing decompressive resection of spinal cord metastases. The third most cited article was the 1978 study by Gilbert that evaluated treatment of epidural spinal cord compression due to metastatic tumor (560 citations).

CONCLUSIONS

The field of metastatic spine disease has witnessed numerous milestones and so it is increasingly important to recognize studies that have influenced the field. In this bibliographic study the authors identified and analyzed the most influential articles in the field of metastatic spine disease.

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Andreea Seicean, Nima Alan, Sinziana Seicean, Duncan Neuhauser, Warren R. Selman, and Nicholas C. Bambakidis

OBJECT

Preoperative anemia may be treated with a blood transfusion. Both are associated with adverse outcomes in various surgical procedures, but this has not been clearly elucidated in surgery for cerebral aneurysms. In this study the authors assessed the association of preoperative anemia and perioperative blood transfusion, separately, on 30-day morbidity and mortality in patients undergoing open surgery for ruptured and unruptured intracranial aneurysms.

METHODS

The authors identified 668 cases (including 400 unruptured and 268 unruptured intracranial aneurysms) of open surgery for treatment of intracranial aneurysms in the 2006–2012 National Surgical Quality Improvement Program, a validated and reproducible prospective clinical database. Anemia was defined as a hematocrit level less than 39% in males and less than 36% in females. Perioperative transfusion was defined as at least 1 unit of packed or whole red blood cells given at any point between the start of surgery to 72 hours postoperatively. The authors separately compared surgical outcome between patients with (n = 198) versus without (n = 470) anemia, and those who underwent (n = 78) versus those who did not receive (n = 521) a transfusion, using a 1:1 match on propensity score.

RESULTS

In the matched cohorts, all observed covariates were comparable between anemic (n = 147) versus nonanemic (n = 147) and between transfused (n = 67) versus nontransfused patients (n = 67). Anemia was independently associated with prolonged hospital length of stay (LOS; odds ratio [OR] 2.5, 95% confidence interval [CI] 1.4–4.5), perioperative complications (OR 1.9, 95% CI 1.1–3.1), and return to the operating room (OR 2.1, 95% CI 1.1–4.5). Transfusion was also independently associated with perioperative complications (OR 2.4, 95% CI 1.1–5.3).

CONCLUSIONS

Preoperative anemia and transfusion are each independent risk factors for perioperative complications in patients undergoing surgery for cerebral aneurysms. Perioperative anemia is also associated with prolonged hospital LOS and 30-day return to the operating room.

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Nima Alan, Andreea Seicean, Sinziana Seicean, Nicholas K. Schiltz, Duncan Neuhauser, and Robert J. Weil

Object

The goal in this study was to assess whether a current or prior history of smoking and the number of smoking pack years affect the risk for adverse outcomes in the 30-day postoperative period in patients who undergo elective cranial surgery.

Methods

Data from the 2006–2011 American College of Surgeons' National Surgical Quality Improvement Project were used in this study. The authors identified 8296 patients who underwent elective cranial surgery, of whom 1718 were current smokers, 854 were prior smokers, and 5724 were never smokers. Using propensity scores and age, the authors matched current and prior smokers to never smokers. Odds ratios for adverse postoperative outcomes were predicted with logistic regression. The relationship between number of pack years and poor outcomes was also examined.

Results

In unadjusted analyses, prior and current smokers did not differ from never smokers for having poor outcomes postoperatively. Similarly, in matched analyses, no association was found between smoking and adverse outcomes. Number of pack years in propensity-matched analyses did not predict worse outcomes in prior or current smokers versus never smokers.

Conclusions

The authors did not find smoking to be associated with 30-day postoperative morbidity or mortality. Although smoking cessation is beneficial for overall health, it may not improve the short-term (≤ 30 days) outcome of elective cranial surgery. Thus postponement of elective cranial cases only for smoking cessation may not be necessary.

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Nima Alan, Andreea Seicean, Sinziana Seicean, Duncan Neuhauser, and Robert J. Weil

Object

The objective of this study was to assess whether preoperative anemia in patients undergoing elective cranial surgery influences outcomes in the immediate perioperative period (≤ 30 days).

Methods

The National Surgical Quality Improvement Program (NSQIP) was used to identify 6576 patients undergoing elective cranial surgery between 2006 and 2011. Propensity scores were used to match patients with moderate to severe anemia (moderate-severe) or mild anemia with patients without anemia. Logistic regression analysis was used to predict the outcomes of interest. Sensitivity analyses were used to limit the sample to patients without perioperative transfusion as well as those who underwent craniotomy for definitive resection of a malignant brain tumor.

Results

A total of 6576 patients underwent elective cranial surgery, of whom 175 had moderate-severe anemia and 1868 had mild anemia. Patients with moderate-severe (odds ratio 1.8, 95% CI 1.1–2.8) and mild (odds ratio 1.5, 95% CI 1.3–1.7) anemia were more likely to have prolonged length of stay (LOS) in the hospital compared to those with no anemia. Similarly, in patients who underwent craniotomy for a malignant tumor resection (n = 2537), anemia of any severity was associated with prolonged LOS, but not postoperative complications nor death.

Conclusions

Anemia is not associated with an overall increased risk for adverse outcomes in patients undergoing elective cranial surgery. However, patients with anemia are more likely to experience prolonged hospitalization postoperatively, resulting in increased resource utilization.

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Farideh Nejat, Pari Zarrini, and Mostafa El Khashab

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Nima Alan, Sunil Manjila, Nori Minich, Nancy Bass, Alan R. Cohen, Michele Walsh, and Shenandoah Robinson

Object

Although survival for extremely low gestational age newborns (ELGANs) has improved in the past 3 decades, these infants remain prone to complications of prematurity, including intraventricular hemorrhage (IVH). The authors reviewed the outcomes for an entire cohort of ELGANs who suffered severe IVH at their institution during the past 12 years to gain a better understanding of the natural history of IVH and frequency of ventriculoperitoneal (VP) shunt placement in this population.

Methods

Data from the neonatal ICU (NICU) database, neurosurgery operative log, and medical records were used to identify and follow up all ELGANs who suffered a severe IVH between 1997 and 2008. Trends between Period 1 (1997–2001) and Period 2 (2004–2008) were analyzed using the Pearson chi-square test.

Results

Between 1997 and 2008, 1335 ELGANs were admitted to the NICU at the authors' institution within 3 days of birth, and 111 (8.3%) of these infants suffered a severe IVH. Survival to 2 years, incidence of severe IVH, neonatal risk factors (gestational age, birth weight, and incidence of necrotizing enterocolitis), ventriculomegaly on cranial ultrasonography, and use of serial lumbar punctures for symptomatic hydrocephalus were all stable. Infants from Period 2 had a significantly lower incidence of bronchopulmonary dysplasia and sepsis than infants from Period 1 (both p < 0.001). All ELGANs with severe IVH and ventriculomegaly underwent long-term follow-up to identify shunt status at late follow-up. Twenty-two ELGANs (20%) with severe IVH required a temporary ventriculosubgaleal (VSG) shunt. Three infants with VSG shunts showed spontaneous hydrocephalus resolution, and 2 infants died of unrelated causes during the neonatal admission. The temporary VSG shunt complication rate was 20% (12% infection and 8% malfunction). Sixteen percent of all ELGANs (18 of 111) with severe IVH eventually required permanent ventricular shunt insertion. Six (35%) of 17 infants with a permanent VP shunt required at least 1 permanent shunt revision during the 1st year. The proportion of ELGANs with severe IVH who required a temporary VSG (35%) or permanent VP shunt (30%) during Period 1 decreased by more than 60% in Period 2 (10% [p = 0.005] and 8.3% [p = 0.009], respectively).

Conclusions

The authors report for the first time a marked reduction over the past 12 years in the proportion of ELGANs with severe IVH who required surgical intervention for hydrocephalus. Using the NICU database, the authors were able to identify and follow all ELGANs with severe IVH and ventriculomegaly. They speculate that the reduction in ventricular shunt rate results from improved neonatal medical care, including reduced infection, improved bronchopulmonary dysplasia, and postnatal steroid avoidance, which may aid innate repair mechanisms. Multicenter prospective trials and detailed analyses of NICU parameters of neonatal well-being are needed to understand how perinatal factors influence the propensity to require ventricular shunting.