Faculty Bibliography

Endoscopic spine surgery (ESS) is growing in popularity as a minimally invasive approach to a variety of spinal conditions. Similar to other types of minimally invasive spine surgery (MISS), ESS aims to address the underlying pathology while minimizing surrounding tissue disruption. Its use in the lumbar spine has progressed over the past 50 years and is now routinely used in cases of lumbar disc herniations and stenosis. This review defines common terminology, highlights important developments in the history of ESS, and discusses its current and future application in the lumbar spine.

BACKGROUND CONTEXT: C5 palsy stands as a known but poorly understood complication of cervical spine surgery with rates reported as high as 30%. Although there are multiple studies presenting different risk factors, variability in findings have led to controversy in the etiology of postoperative C5 palsy. PURPOSE: To evaluate factors that predispose a patient to developing C5 palsy following cervical spine surgery. STUDY DESIGN/SETTING: Retrospective review of a large single center academic institution. PATIENT SAMPLE: This study included 239 cervical spinal procedures from 2013 to 2018. OUTCOME MEASURES: Patient demographics, surgical procedure and approach, perioperative clinical characteristics, postoperative rate of C5 palsy, C5 palsy resolution, and radiographic outcomes.
METHOD(S): Patients >=18 years of age who underwent cervical spinal surgery including the C4/C5 level, with minimum 1-year follow-up were included. C5 palsy was defined as deltoid +/- bicep weakness with Modified Rankin Scale grading at least 1 point below baseline (BL). Characteristics studied include: demographics, surgical procedure and approach (decompression and/or fusion). Radiographic analyses of MRI and CT measurements of foramen dimensions and spinal cord drift at BL and follow-up were performed. Statistical analyses included t-tests, chi-square analysis, and multivariate logistic regression to determine independent predictive factors. A receiver operating characteristic curve was run to determine the cutoff levels for predictive factors. Significance set at p<0.05.
RESULT(S): A total of 239 patients were included, with a C5 palsy rate of 6.3% for all cases. Subjects that developed C5 palsy were older (64.67+/-8.61 vs 57.56+/-11.61, p=0.021), had more levels decompressed posteriorly (3.20+/-1.82 vs 1.12+/-1.74, p<0.001), a higher rate of preoperative myelomalacia (60% vs 19.6%, p=0.008), and higher CCI (3.80+/-1.97 vs 2.35+/-1.95, p=0.005). Anterior cervical discectomy and fusion (ACDF) surgeries had a 2.4% rate of C5 palsy while the posterior approach rate was 11.9% (p<0.007). The highest rate was in laminectomy and posterior fusion at 15.2% (p<0.001). There were no significant differences in palsy resolution between those treated surgically compared to those not treated. Radiographically, C5 palsy patients had smaller postoperative foramen width measurements than those who did not develop C5 palsy (2.16+/-1.04 vs 3.31+/-1.25, p=0.023 on the right; 1.84+/-0.80 vs 3.02+/-1.25, p=0.014 on the left). When controlling for technique, CCI, age, BMI, and myelomalacia, multivariate regression analysis revealed increasing levels of laminectomy to be a significant independent predictor of C5 palsy (1.602 (2.258-1.136) for each additional level decompressed, p=0.007). The cut-off value for levels decompressed via laminectomy was determined to be 3.50 levels (>=0.7 AUC <=0.8). Postoperative foramen width was also an independent risk factor for C5 palsy (0.009 (0.000-0.726), p=0.035), it was determined that risk of C5 palsy increases at <2.625mm foramen width (>=0.8 AUC <=0.9).
CONCLUSION(S): C5 palsy following cervical spine surgery is correlated with residual postoperative foraminal stenosis and posterior surgery with increasing number levels decompressed. Patients undergoing more than 3.5 level laminectomy with less than 2.625mm foramen width postoperatively are at highest risk of developing C5 palsy. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: The thoracolumbar junction poses increased risk for high stress on upper lumbar discs when not adequately fused. However, controversy persists. This study evaluates outcomes of upper instrumented vertebrae (UIV) selection in the thoracic versus the upper lumbar spine when fusing to the sacrum. PURPOSE: To compare revision rates for thoracolumbar fusions to the sacrum and pelvis at 1- and 2-year follow-up, stratified by UIV selection. STUDY DESIGN/SETTING: Retrospective cohort study at a single institution. PATIENT SAMPLE: A total of 968 patients who had thoracolumbar fusion surgery between 2012-2018 with at least one year of postoperative follow-up. OUTCOME MEASURES: Reoperation rates from 1 and 2 years after revision surgery, reoperation diagnoses, body mass index (BMI), gender, Charleston Comorbidity Index (CCI), perioperative complications, ASA grade (ASA), operative time (OT), and blood loss (EBL).
METHOD(S): A retrospective review of patients undergoing revision spinal fusion with lower instrumented vertebra of S1 or pelvis between 2012-2018 at a single institution was performed. Patients with less than 1 year of follow-up after their index procedure were excluded from the analysis. Patients were categorized based on UIV into 6 groups: T9-T11, L1, L2, L3, L4, and L5. Demographic and operative data were collected and compared between the different UIV groups in each cohort using chi-squared and ANOVA tests. Revision rates at 1- and 2-year follow-up and the reasons for revision were compared between groups.
RESULT(S): There were 168 revision spinal fusions that reached 1-year follow-up, with 54 having UIV at T9-T11, 2 fusions L1 to sacrum, 26 fusions L2 to sacrum, 25 fusions L3 to sacrum, 36 fusions L4 to sacrum, 23 fusions L5 to sacrum. There was significant difference in patient age, with oldest in the L1 group (65.5+/-3.5) and youngest in the L5 group (51+/-15.4 p<0.001). There was significant difference in gender as both cases in L2 was female and L5 fusions only had 39.1% females (p = 0.006). There were no differences in BMI, CCI, and ASA. EBL (1891.6mL+/-1226.9mL p <0.001) and length of stay (7.7+/-3.0 p <0.001) was highest in the T9-11 UIV group. Operative time was highest in the L1 (464.5+/-174.7 p<0.001) UIV group. Levels added on top of prior fusion were calculated by subtracting UIV of index fusion to past UIV. Adding on 2 levels had a 1-year revision rate of 14.3% (p = 0.032), while adding on 1 level had a 0% 1-year revision rate. Adding on 4 levels had a revision rate of 12.5%, and adding on 7 levels had a 50% 1-year revision rate. At 2 years, adding on 1 level had revision rate of 25% and adding on 2 levels had a revision rate of 20% (p = 0.769). There is no statistically significant difference in perioperative complication rates between UIV groups (p = 0.114). The reoperation rate at 1 year for all levels was 9% and highest in UIV at L1 (50%, p=0.06). At 2-year follow-up, the reoperation rate for the total cohort was 32.34% with the highest revision rate for fusion from L2 to sacrum (53.85%) followed by (T9-T11 sacrum fusion 42.31%, L4 to sacrum31.71%, L3 to sacrum 30%, L5 to sacrum 25.04%, L1 to sacrum 25%, p=0.195). Grouping the UIV into lower thoracic (T9-T11), upper lumbar (L2-L3), and lower lumbar (L4-L5) showed similar revision rates at one year (p=0.697). At two years, lower thoracic group had a revision rate of 40% versus, 23.3% in the upper lumbar group (p =0.399).
CONCLUSION(S): There is no statistically significant difference in reoperation rates for revision thoracolumbar fusions to the sacrum/pelvis associated with different UIV selection. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND:Lumbar herniated nucleus pulposus (HNP) is a common spinal pathology often treated by microscopic lumbar discectomy (MLD), though prior reports have not demonstrated which preoperative MRI factors may contribute to significant clinical improvement after MLD. PURPOSE/OBJECTIVE:To analyze the MRI characteristics in patients with HNP that predict meaningful clinical improvement in Health Related Quality of Life scores (HRQoL) after MLD. STUDY DESIGN/SETTING/METHODS:Retrospective clinical and radiological study of patients undergoing MLD for HNP at a single institution over a two-year period. PATIENT SAMPLE/METHODS:88 patients receiving MLD treatment for HNP. OUTCOME MEASURES/METHODS:Cephalocaudal Canal Migration; Canal & HNP Anterior-Posterior (AP) Lengths and Ratio; Canal & HNP Axial Areas and Ratio; Hemi-Canal & Hemi-HNP Axial Areas and Ratio; Disc appearance (black, grey or mixed), Baseline (BL) and 3-Month (3M) postoperative Health Related Quality of Life Scores. METHODS:Patients > 18 years old who received MLD for HNP with BL and 3M HRQoL scores of PROMIS (Physical Function, Pain Interference, and Pain Intensity), ODI, VAS Back, and VAS Leg scores were included. HNP and spinal canal measurements of cephalocaudal migration, AP length, area, hemi-area, and disc appearance were performed using T2 axial and sagittal MRI. HNP measurements were divided by corresponding canal measurements to calculate AP, Area, and Hemi-Area ratios. Using known minimal clinically important differences (MCID) for each ΔHRQoL score, patients were separated into two groups based on whether they reached MCID (MCID+) or did not reach MCID (MCID-). The MCID for PROMIS Pain Intensity was calculated using a decision tree. A linear regression illustrated correlations between PROMIS vs ODI and VAS Back/Leg scores. Independent t-tests and chi [2] tests were utilized to investigate significant differences in HNP measurements between the MCID+ and MCID- groups. RESULTS:± 43.2, p<.04). MCID+ patients had a greater Hemi-Area Ratio than MCID- patients had in 4 out of 6 HRQoL score comparisons (51.8% ± 14.7 vs 43.9% ± 14.9, p<.05). CONCLUSIONS:Patients who met MCID after MLD had larger HNP areas and larger Hemi-HNP Areas than those who did not meet MCID. These patients were also 2.7x more likely to have a grey MRI signal than a mixed or black MRI signal. When accounting for HNP area relative to canal area, patients who met MCID had greater Hemi-HNP canal occupation than patients who did not meet MCID. The results of this study suggest that preoperative MRI parameters can be useful in predicting patient reported improvement after MLD.

Study Design/UNASSIGNED:Retrospective cohort study. Objective/UNASSIGNED:To investigate radiological differences in lumbar disc herniations (herniated nucleus pulposus [HNP]) between patients receiving microscopic lumbar discectomy (MLD) and nonoperative patients. Methods/UNASSIGNED:test and chi-square analyses compared differences in the groups, binary logistic regression analysis determined odds ratios (ORs), and decision tree analysis compared the cutoff values for risk factors. Results/UNASSIGNED:< .01). Conclusion/UNASSIGNED:Patients who underwent MLD treatment had significantly different axial HNP area, frequency of caudal migration, magnitude of cephalad/caudal migration, and disc herniation MRI signal compared to patients with nonoperative treatment.

Previous efforts to evaluate the detection of human papilloma viral (HPV) DNA in whole saliva as a diagnostic measure for HPV-associated oropharyngeal cancer (HPV-OPC) have not shown sufficient clinical performance. We hypothesize that salivary exosomes are packaged with HPV-associated biomarkers, and efficient enrichment of salivary exosomes through isolation can enhance diagnostic and prognostic performance for HPV-OPC. In this study, an acoustofluidic (the fusion of acoustics and microfluidics) platform was developed to perform size-based isolation of salivary exosomes. These data showed that this platform is capable of consistently isolating exosomes from saliva samples, regardless of viscosity variation and collection method. Compared with the current gold standard, differential centrifugation, droplet digital RT-PCR analysis showed that the average yield of salivary exosomal small RNA from the acoustofluidic platform is 15 times higher. With this high-yield exosome isolation platform, we show that HPV16 DNA could be detected in isolated exosomes from the saliva of HPV-associated OPC patients at 80% concordance with tissues/biopsies positive for HPV16. Overall, these data demonstrated that the acoustofluidic platform can achieve high-purity and high-yield salivary exosome isolation for downstream salivary exosome-based liquid biopsy applications. Additionally, HPV16 DNA sequences in HPV-OPC patients are packaged in salivary exosomes and their isolation will enhance the detection of HPV16 DNA.

War has historically been a major catalyst for advancement in military medical care and medicine in general. In our current conflicts, advances in battlefield medicine, evacuation techniques, and personal protective equipment have improved survival rates among members of the armed services. With increased survival, there has been increased prevalence of serious but nonfatal injuries, particularly from blunt and penetrating trauma. Blast injuries are the major cause of trauma and have both blunt and penetrating components. With respect to the spine, blasts have led to open, contaminated wounds that are complex and difficult to treat. Additionally, blasts have led to an increased incidence of lower lumbar burst fractures and lumbosacral dissociation. As these and other injuries are being seen more commonly during war, we must ensure that our military medical system is adapting to ensure we are taking care of our military personnel at the highest level.

Background/UNASSIGNED:Robotic-guided navigation systems for pedicle screw placement has gained recent interest to ensure accuracy and safety and diminish radiation exposure. There have been no published studies using a new combined robotics and navigation system (Globus ExcelsiusGPS system). The purpose of this study was to demonstrate safety with this system. Methods/UNASSIGNED:This is a case series of consecutive patients at a single institution from February 1, 2018, to August 31, 2018. All patients who had planned placement of thoracic and lumbar pedicle screws using the combined robotics-navigation system were included. Chart review was performed for operative details. A subgroup analysis was performed on patients with postoperative computed tomography (CT) scans to assess screw placement accuracy using the Gertzbein and Robbins system. Acceptable pedicle screw position was defined as grade A or B. Results/UNASSIGNED:One hundred six patients were included, with 636 pedicle screws, 6 iliac screws, and 1 S2AI screw. Five cases were aborted for technical issues. In the remaining 101 patients, 88 patients had screws placed using preoperative CT planning and 13 patients using intraoperative fluoroscopy planning. All screws except for 5 pedicle screws in 2 patients were placed successfully using the robot (99%). These 5 pedicle screws were placed by converting to a fluoro-guided technique without robotic assistance. Eighty-six patients had screws placed using a percutaneous technique, and 15 patients had screws placed using an open technique. Ninety-eight patients underwent interbody placement: 28 anterior lumbar interbody fusions (ALIFs), 12 lateral lumbar interbody fusions (LLIFs), and 58 transforaminal lumbar interbody fusions (TLIFs). All ALIFs and LLIFs were performed prior to placement of the screws. Four LIF patients had screws placed in the lateral position. No patients had screw-related complications intraoperatively or postoperatively, and no patients returned to the operating room for screw revision. Thirteen patients underwent postoperative CT for various reasons. Of the 66 pedicle screws that were examined with postoperative CT, all screws (100%) had acceptable position. Conclusion/UNASSIGNED:This study demonstrates that the combined robotics and navigation system is a novel technology that can be utilized to place pedicle screws and pelvic screws safely and has the potential to reduce screw-related complications. Level of Evidence/UNASSIGNED:4 (case series).

BACKGROUND CONTEXT: Existing health outcome (HRQL) metrics do not adequately capture disability from cervical deformity (CD) and do not correlate with cervical malalignment. In the novel Patient Generated Index (PGI) patients report their greatest difficulties related to their CD. These results were used to determine items that should be included in a CD-specific HRQL. PURPOSE: To utilize the PGI to reveal the aspects of CD disability not captured by existing HRQLs. STUDY DESIGN/SETTING: Retrospective review of a prospective CD database. PATIENT SAMPLE: A total of 45 CD patients. OUTCOME MEASURES: HRQL metrics: PGI, NDI, mJOA, EQ-5D.
METHOD(S): CD patients completed the PGI by describing aspects of their disability that bother them the most. The responses were weighted and scored. PGI responses were categorized into domains: Sagittal discomfort/range of motion (ROM), Activities of Daily Living (ADL), and Social Life/Hobbies. PGI scores and legacy HRQL metrics were correlated with alignment, pain, age, sex, BMI, and medical comorbidities. R2 values are reported for linear regression models that include the drivers significantly associated with each HRQL metric.
RESULT(S): Forty-five CD patients (mean cSVA: 51mm) including 12 PGI patients (mean cSVA: 62mm) were included for analysis. PGI scores were found to be driven significantly by age and C2 Slope (r2=0.50). NDI was driven significantly by neck pain, back pain, and BMI (r2=0.32). mJOA was driven significantly by Charlson Comorbidity Score, back pain and weight (r2=0.33). EQ5D was significantly driven by CBVA, age and T1 Slope (r2=0.78). When examining PGI domains, Sagittal Discomfort/ROM score was driven significantly by cSVA and age (r2=0.54). ADL score was driven by CBVA and a medical history of neuromuscular disease (r2=0.87). Social Life/Hobbies score was driven by Charlson Comorbidity Scores, a medical history of ankylosing spondylitis, and a medical history of connective tissue disease (r2=1.0). Horizontal Gaze/Walking Safety, Pain, and Neurologic Complaints did not correlate significantly with alignment, pain, demographic info or past medical history.
CONCLUSION(S): Legacy HRQLs do not adequately capture CD disability and do not correlate with cervical malalignment. In a CD cohort, PGI scores and EQ5D scores were driven significantly by sagittal alignment. However, mJOA and NDI were driven by pain and medical comorbidities. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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