The Posterior Cranial Vertical Line: A Novel Radiographic Marker for Classifying Global Sagittal Alignment.

OBJECTIVE: To define a novel radiographic measurement, the posterior cranial vertical line (PCVL), in an asymptomatic adult population to better understand global sagittal alignment. METHODS: We performed a multicenter retrospective review of prospectively collected radiographic data on asymptomatic volunteers aged 20-79. The PCVL is a vertical plumb line drawn from the posterior-most aspect of the occiput. The horizontal distances of the PCVL to the thoracic apex (TA), posterior sagittal vertical line (PSVL, posterosuperior endplate of S1), femoral head center, and tibial plafond were measured. Classification was either grade 1 (PCVL posterior to TA and PSVL), grade 2 (PCVL anterior to TA and posterior to PSVL), or grade 3 (PCVL anterior to TA and PSVL). RESULTS: Three hundred thirty-four asymptomatic patients were evaluated with a mean age of 41 years. Eighty-three percent of subjects were PCVL grade 1, 15% were grade 2, and 3% were grade 3. Increasing PCVL grade was associated with increased age (p < 0.001), C7-S1 sagittal vertical axis (SVA) (p < 0.001), C2-7 SVA (p < 0.001). Additionally, it was associated with decreased SS (p = 0.045), increased PT (p < 0.001), and increased knee flexion (p < 0.001). CONCLUSION: The PCVL is a radiographic marker of global sagittal alignment that is simple to implement and interpret. Increasing PCVL grade was significantly associated with expected changes and compensatory mechanisms in the aging population. Most importantly, it incorporates cervical alignment parameters such as C2-7 SVA. The PCVL defines global sagittal alignment in adult volunteers and naturally distributes into 3 grades, with only 3% being grade 3 where the PCVL lies anterior to the TA and PSVL.

Is There a Difference in Screw Accuracy, Robot Time Per Screw, Robot Abandonment, and Radiation Exposure Between the Mazor X and the Renaissance? A Propensity-Matched Analysis of 1179 Robot-Assisted Screws.

STUDY DESIGN: Prospective single-cohort analysis. OBJECTIVES: To compare the outcomes/complications of 2 robotic systems for spine surgery. METHODS: Adult patients (≥18-years-old) who underwent robot-assisted spine surgery from 2016-2019 were assessed. A propensity score matching (PSM) algorithm was used to match Mazor X to Renaissance cases. Preoperative CT scan for planning and an intraoperative O-arm for screw evaluation were preformed. Outcomes included screw accuracy, robot time/screw, robot abandonment, and radiation. Screw accuracy was measured using Vitrea Core software by 2 orthopedic surgeons. Screw breach was measured according to the Gertzbein/Robbins classification. RESULTS: After PSA, a total of 65 patients (Renaissance: 22 vs. X: 43) were included. Patient/operative factors were similar between robot systems (P > .05). The pedicle screw accuracy was similar between robots (Renaissance: 1.1%% vs. X: 1.3%, P = .786); however, the S2AI screw breach rate was significantly lower for the X (Renaissance: 9.5% vs. X: 1.2%, P = .025). Robot time per screw was not statistically different (Renaissance: 4.6 minutes vs. X: 3.9 minutes, P = .246). The X was more reliable with an abandonment rate of 2.3% vs. Renaissance:22.7%, P = .007. Radiation exposure were not different between robot systems. Non-robot related complications including dural tear, loss of motor/sensory function, and blood transfusion were similar between robot systems. CONCLUSION: This is the first comparative analyses of screw accuracy, robot time/screw, robot abandonment, and radiation exposure between the Mazor X and Renaissance systems. There are substantial improvements in the X robot, particularly in the perioperative planning processes, which likely contribute to the X's superiority in S2AI screw accuracy by nearly 8-fold and robot reliability by nearly 10-fold.

How common is acute pelvic fixation failure after adult spine surgery? A single-center study of 358 patients.

OBJECTIVE: There is a paucity of literature on pelvic fixation failure after adult spine surgery in the early postoperative period. The purpose of this study was to determine the incidence of acute pelvic fixation failure in a large single-center study and to describe the lessons learned. METHODS: The authors performed a retrospective review of adult (≥ 18 years old) patients who underwent spinal fusion with pelvic fixation (iliac, S2-alar-iliac [S2AI] screws) at a single academic medical center between 2015 and 2020. All patients had a minimum of 3 instrumented levels. The minimum follow-up was 6 months after the index spine surgery. Patients with prior pelvic fixation were excluded. Acute pelvic fixation failure was defined as revision of the pelvic screws within 6 months of the primary surgery. Patient demographics and operative, radiographic, and rod/screw parameters were collected. All rods were cobalt-chrome. All iliac and S2AI screws were closed-headed screws. RESULTS: In 358 patients, the mean age was 59.5 ± 13.6 years, and 64.0% (n = 229) were female. The mean number of instrumented levels was 11.5 ± 5.5, and 79.1% (n = 283) had ≥ 6 levels fused. Three-column osteotomies were performed in 14.2% (n = 51) of patients, and 74.6% (n = 267) had an L5-S1 interbody fusion. The mean diameter/length of pelvic screws was 8.5/86.6 mm. The mean number of pelvic screws was 2.2 ± 0.5, the mean rod diameter was 6.0 ± 0 mm, and 78.5% (n = 281) had > 2 rods crossing the lumbopelvic junction. Accessory rods extended to S1 (32.7%, n = 117) or S2/ilium (45.8%, n = 164). Acute pelvic fixation failure occurred in 1 patient (0.3%); this individual had a broken S2AI screw near the head-neck junction. This 76-year-old woman with degenerative lumbar scoliosis and chronic lumbosacral zone 1 fracture nonunion had undergone posterior instrumented fusion from T10 to pelvis with bilateral S2AI screws (8.5 × 90 mm); i.e., transforaminal lumbar interbody fusion L4-S1. The patient had persistent left buttock pain postoperatively, with radiographically confirmed breakage of the left S2AI screw 68 days after surgery. Revision included instrumentation removal at L2-pelvis and a total of 4 pelvic screws. CONCLUSIONS: The acute pelvic fixation failure rate was exceedingly low in adult spine surgery. This rate may be the result of multiple factors including the preference for multirod (> 2), closed-headed pelvic screw constructs in which large-diameter long screws are used. Increasing the number of rods and screws at the lumbopelvic junction may be important factors to consider, especially for patients with high risk for nonunion.

Rod fractures after multi-rod constructs in adult spinal deformity patients fused to the sacrum/pelvis: where do they occur and why?

PURPOSE: (1) To describe the use of multi-rod constructs (MRCs) in adult spinal deformity (ASD) surgery, (2) to report rod fractures occurring at MRC sites, and (3) to evaluate risk factors for rod fractures. METHODS: A single-center, retrospective cohort study was conducted of patients undergoing ASD surgery with these inclusion criteria: minimum 2-year follow-up, MRCs used, ≥ 10-level fusion, and fused to sacrum/pelvis. The primary outcome was rod fracture. Univariate/multivariate logistic regression was performed controlling for age, kickstand rod usage, number of rods across the lumbosacral junction (LSJ), and the amount of coronal/sagittal Cobb correction. RESULTS: Among 57 patients undergoing ASD surgery with MRCs, mean age was 60 ± 11 years. With respect to MRCs, 32 (56%) patients had 3 rods, 18 (32%) had 4, and 7 (12%) had 5. Rods crossing the LSJ were most often three (63%), followed by four (25%) and five (5%) rods. Nine (16%) patients experienced rod fractures with eight (89%) patients having no more than three rods crossing the LSJ. A coronal correction > 30 mm was more often seen in patients with rod fracture (p = 0.030), while an SVA correction > 50 mm was not significantly different (p = 0.608). Multivariate logistic regression revealed that the amount of coronal correction was significantly associated with rod fracture (OR 1.03, 95% CI 1.01-1.07, p = 0.044), as was achieving a coronal correction > 30 mm (OR 7.72, 95% CI 1.17-51.10, p = 0.034), with no association between the amount of sagittal correction obtained and rod fracture. CONCLUSION: This study found that greater coronal correction was associated with an increased odds of rod fracture. We suggest adding at least four rods across the LSJ cephalad to the interbody fusions to avoid rod fractures in these high demand areas. LEVEL OF EVIDENCE: III.

Incidence, mechanism, and protective strategies for 2-year pelvic fixation failure after adult spinal deformity surgery with a minimum six-level fusion.

OBJECTIVE: The purpose of this study was to determine the incidence, mechanism, and potential protective strategies for pelvic fixation failure (PFF) within 2 years after adult spinal deformity (ASD) surgery. METHODS: Data for ASD patients (age ≥ 18 years, minimum of six instrumented levels) with pelvic fixation (S2-alar-iliac [S2AI] and/or iliac screws) with a minimum 2-year follow-up were consecutively collected (2015-2019). Patients with prior pelvic fixation were excluded. PFF was defined as any revision to pelvic screws, which may include broken rods across the lumbosacral junction requiring revision to pelvic screws, pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws, a broken or loose pelvic screw, or sacral/iliac fracture. Patient information including demographic data and health history (age, sex, BMI, smoking status, American Society of Anesthesiologists score, osteoporosis), operative (total instrumented levels [TIL], three-column osteotomy [3CO], interbody fusion), screw (iliac, S2AI, length, diameter), rod (diameter, kickstand), rod pattern (number crossing lumbopelvic junction, lowest instrumented vertebra [LIV] of accessory rod[s], lateral connectors, dual-headed screws), and pre- and postradiographic (lumbar lordosis, pelvic incidence, pelvic tilt, major Cobb angle, lumbosacral fractional curve, C7 coronal vertical axis [CVA], T1 pelvic angle, C7 sagittal vertical axis) parameters was collected. All rods across the lumbosacral junction were cobalt-chrome. All iliac and S2AI screws were closed-headed tulips. Both univariate and multivariate analyses were performed to determine risk factors for PFF. RESULTS: Of 253 patients (mean age 58.9 years, mean TIL 13.6, 3CO 15.8%, L5-S1 interbody 74.7%, mean pelvic screw diameter/length 8.6/87 mm), the 2-year failure rate was 4.3% (n = 11). The mechanisms of failure included broken rods across the lumbosacral junction (n = 4), pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws (n = 3), broken pelvic screw (n = 1), loose pelvic screw (n = 1), sacral/iliac fracture (n = 1), and painful/prominent pelvic screw (n = 1). A higher number of rods crossing the lumbopelvic junction (mean 3.8 no failure vs 2.9 failure, p = 0.009) and accessory rod LIV to S2/ilium (no failure 54.2% vs failure 18.2%, p = 0.003) were protective for failure. Multivariate analysis demonstrated that accessory rod LIV to S2/ilium versus S1 (OR 0.2, p = 0.004) and number of rods crossing the lumbar to pelvis (OR 0.15, p = 0.002) were protective, while worse postoperative CVA (OR 1.5, p = 0.028) was an independent risk factor for failure. CONCLUSIONS: The 2-year PFF rate was low relative to what is reported in the literature, despite patients undergoing long fusion constructs for ASD. The number of rods crossing the lumbopelvic junction and accessory rod LIV to S2/ilium relative to S1 alone likely increase construct stiffness. Residual postoperative coronal malalignment should be avoided to reduce PFF.

Performing the 3-level Anterior Cervical Discectomy and Fusion (ACDF): Technical Pearls to Maximize Fusion Rates and Reduce Postoperative Complications.

The anterior cervical discectomy and fusion is a common and effective treatment for degenerative cervical myelopathy, either with or without concomitant radiculopathy. In many cases, patients with degenerative cervical spondylosis can present with disease at multiple levels. With each additional level included in the procedure, rates of complication rate can increase-both due to the nature of the anterior cervical approach (dysphagia) as well as fusion across all levels. Here, we review several technical considerations with the goal of increasing efficiency and improving outcomes with the 3-level anterior cervical discectomy and fusion.

Determining the relationship between preoperative mental health scores and postoperative outcomes in adult spinal deformity surgeries.

OBJECTIVE: The objective of this study was to examine the relationship between the mental health domain of the refined 22-item Scoliosis Research Society Outcome Questionnaire (SRS) and various postoperative outcome measures in the adult spinal deformity (ASD) population. Given the scale and involved nature of deformity surgery, some surgeons have proposed that preoperative mental health scores (MHSs) may assist in screening out poor surgical candidates. In this study, the authors aimed to further assess the SRS MHS as a preoperative metric and its association with postoperative outcomes and to comment on its potential use in patient selection and optimization for ASD surgery. METHODS: The authors conducted a retrospective study of 100 consecutive patients who had undergone primary or revision ASD surgery at a single academic institution between 2015 and 2019. Each patient had a minimum 2-year follow-up. Patients were categorized on the basis of their baseline mental health per the SRS mental health domain, with a score < 4 indicating low baseline mental health (LMH) and a score ≥ 4 indicating high baseline mental health (HMH). Baseline and follow-up SRS and Oswestry Disability Index scores, surgical procedures, lengths of stay, discharge locations, intraoperative or postoperative complications, and other outcome metrics were then compared between the HMH and LMH groups, as well as these groups stratified by an age ≤ 45 and > 45 years. RESULTS: Among patients aged ≤ 45 and those aged > 45, the LMH group had significantly worse baseline health-related quality-of-life (HRQOL) metrics in nearly all domains. The LMH group also had an increased median estimated blood loss (EBL; 1200 vs 800 ml, p = 0.0026) and longer average surgical duration (8.3 ± 2.8 vs 6.9 ± 2.6 hours, p = 0.014). Both LMH and HMH groups had significant improvements in nearly all HRQOL measures postoperatively. Despite their worse preoperative HRQOL baseline, patients in the LMH group actually improved the most and reached the same HRQOL endpoints as those in the HMH group. CONCLUSIONS: While patients with lower baseline MHSs may require slightly longer hospital courses or more frequent discharges to rehabilitation facilities, these patients actually attain greater absolute improvements from their preoperative baseline and surprisingly have the same postoperative HRQOL metrics as the patients with high MHSs, despite their poorer starting point. This finding suggests that patients with LMH may be uniquely positioned to substantially benefit from surgical intervention and improve their HRQOL scores and thus should be considered for ASD surgery to an extent similar to patients with HMH.

A national analysis on complications and readmissions for adult cerebral palsy patients undergoing primary spinal fusion surgery.

STUDY DESIGN: Retrospective National Database Study. OBJECTIVE: Surgical intervention with spinal fusion is often indicated in cerebral palsy (CP) patients with progressive scoliosis. The purpose of this study was to utilize the National Readmission Database to determine the national estimates of complication rates, 90-day readmission rates, and costs associated with spinal fusion in adult patients with CP. METHODS: The 2012-2015 NRD databases were queried for all adult (age ≥ 19 years) patients diagnosed with CP (ICD-9: 333.71, 343.0-4, and 343.8-9) undergoing spinal fusion (ICD-9: 81.00-08). RESULTS: 1166 adult patients with CP (42.7% female) underwent spinal fusion surgery between 2012 and 2015. 153 (13.1%) were readmitted within 90 days following the primary surgery, with a mean 33.8 ± 26.5 days. Mean hospital charge of the primary admission was $141,416 ± $157,359 and $167,081 ± $145,416 for the non-readmitted and readmitted patients, respectively (p = 0.06). The mean 90-day readmission charge was $72,479 ± $104,100. Most common complications with the primary admission included UTIs (no readmission vs. readmission: 7.6% vs. 4.8%; p = 0.18), respiratory (6.9% vs. 5.6%; p = 0.62), implant (3.8% vs. 6.0%; p = 0.21), and paralytic ileus (3.6% vs. 3.2%; p = 0.858). Multivariate analyses demonstrated the following as independent predictors for 90-day readmission: comorbid anemia (OR: 2.8; 95% CI: 1.6-4.9; p < 0.001), coagulopathy (2.9, 1.1-8.0, 0.037), perioperative blood transfusion (2.0, 1.1-3.8, 0.026), wound complication (6.4, 1.3-31.6, 0.023), and transfer to short-term hospital versus routine disposition (4.9, 1.0-23.3, 0.045). CONCLUSION: Quality improvement efforts should be aimed at reducing rates of infection related complications as this was the most common reason for short-term complications and unplanned readmission following surgery.

CT-to-fluoroscopy registration versus scan-and-plan registration for robot-assisted insertion of lumbar pedicle screws.

OBJECTIVE: Pedicle screw insertion for stabilization after lumbar fusion surgery is commonly performed by spine surgeons. With the advent of navigation technology, the accuracy of pedicle screw insertion has increased. Robotic guidance has revolutionized the placement of pedicle screws with 2 distinct radiographic registration methods, the scan-and-plan method and CT-to-fluoroscopy method. In this study, the authors aimed to compare the accuracy and safety of these methods. METHODS: A retrospective chart review was conducted at 2 centers to obtain operative data for consecutive patients who underwent robot-assisted lumbar pedicle screw placement. The newest robotic platform (Mazor X Robotic System) was used in all cases. One center used the scan-and-plan registration method, and the other used CT-to-fluoroscopy for registration. Screw accuracy was determined by applying the Gertzbein-Robbins scale. Fluoroscopic exposure times were collected from radiology reports. RESULTS: Overall, 268 patients underwent pedicle screw insertion, 126 patients with scan-and-plan registration and 142 with CT-to-fluoroscopy registration. In the scan-and-plan cohort, 450 screws were inserted across 266 spinal levels (mean 1.7 ± 1.1 screws/level), with 446 (99.1%) screws classified as Gertzbein-Robbins grade A (within the pedicle) and 4 (0.9%) as grade B (< 2-mm deviation). In the CT-to-fluoroscopy cohort, 574 screws were inserted across 280 lumbar spinal levels (mean 2.05 ± 1.7 screws/ level), with 563 (98.1%) grade A screws and 11 (1.9%) grade B (p = 0.17). The scan-and-plan cohort had nonsignificantly less fluoroscopic exposure per screw than the CT-to-fluoroscopy cohort (12 ± 13 seconds vs 11.1 ± 7 seconds, p = 0.3). CONCLUSIONS: Both scan-and-plan registration and CT-to-fluoroscopy registration methods were safe, accurate, and had similar fluoroscopy time exposure overall.

What Is the Comparison in Robot Time per Screw, Radiation Exposure, Robot Abandonment, Screw Accuracy, and Clinical Outcomes Between Percutaneous and Open Robot-Assisted Short Lumbar Fusion?: A Multicenter, Propensity-Matched Analysis of 310 Patients.

STUDY DESIGN: Multicenter cohort. OBJECTIVE: To compare the robot time/screw, radiation exposure, robot abandonment, screw accuracy, and 90-day outcomes between robot-assisted percutaneous and robot-assisted open approach for short lumbar fusion (1- and 2-level). SUMMARY OF BACKGROUND DATA: There is conflicting literature on the superiority of robot-assisted minimally invasive spine surgery to open techniques. A large, multicenter study is needed to further elucidate the outcomes and complications between these two approaches. METHODS: We included adult patients (≥18 yrs old) who underwent robot-assisted short lumbar fusion surgery from 2015 to 2019 at four independent institutions. A propensity score matching algorithm was employed to control for the potential selection bias between percutaneous and open surgery. The minimum follow-up was 90 days after the index surgery. RESULTS: After propensity score matching, 310 patients remained. The mean (standard deviation) Charlson comorbidity index was 1.6 (1.5) and 53% of patients were female. The most common diagnoses included high-grade spondylolisthesis (grade >2) (48%), degenerative disc disease (22%), and spinal stenosis (25%), and the mean number of instrumented levels was 1.5(0.5). The operative time was longer in the open (198 min) versus the percutaneous group (167 min, P value = 0.007). However, the robot time/screw was similar between cohorts (P value > 0.05). The fluoroscopy time/ screw for percutaneous (14.4 s) was longer than the open group (10.1 s, P value = 0.021). The rates for screw exchange and robot abandonment were similar between groups (P value > 0.05). The estimated blood loss (open: 146 mL vs. percutaneous: 61.3 mL, P value < 0.001) and transfusion rate (open: 3.9% vs. percutaneous: 0%, P value = 0.013) were greater for the open group. The 90-day complication rate and mean length of stay were not different between cohorts (P value > 0.05). CONCLUSION: Percutaneous robot-assisted spine surgery may increase radiation exposure, but can achieve a shorter operative time and lower risk for intraoperative blood loss for short-lumbar fusion. Percutaneous approaches do not appear to have an advantage for other short-term postoperative outcomes. Future multicenter studies on longer fusion surgeries and the inclusion of patient-reported outcomes are needed.Level of Evidence: 3.

The accuracy of robot-assisted S2 alar-iliac screw placement at two different healthcare centers.

BACKGROUND: Current literature on robot-assisted S2 alar-iliac (S2AI) screw placement shows favorable outcomes and screw accuracy; however, the data is limited by a few retrospective, single-surgeon studies. To the author's knowledge, this is the first multicenter study which evaluates the accuracy of robot-assisted S2AI screws. METHODS: Adult (≥18 years old) patients who underwent robot-assisted S2AI screw placement from 2017-2019 were reviewed. All surgeries used the same proprietary robotic guidance system, Mazor X (Mazor Robotics Ltd). RESULTS: A total of 65 screws were assessed in 31 patients. The mean follow-up ± standard deviation was 362±190 days (minimum was 90 days). The mean age was 61.1±11 years old, and 54.8% (n=17) of patients were female. Nearly half of the patients had a primary diagnosis of degenerative scoliosis (48.4%, n=15). Other diagnosis included pseudarthrosis (22.6%, n=7), degenerative disc disease (16.1%, n=5), and high-grade spondylolisthesis (12.9%, n=4). The mean length and diameter of screws were 84.6±6.1 mm and 8.4±0.7, respectively. The mean axial and sagittal angles were 50.0±6.3 and 24.0±10.5, respectively. The overall screw accuracy was 93.8% (n=61). There were four iliac cortex breaches (anterior =3, inferior 1) with a mean breach distance of 3.5±3.2. No statistically significant differences in screw length, diameter, axial angle, and sagittal angle were observed between screws with and without a breach. No intraoperative neurologic, vascular, or visceral complications from the S2AI screw were observed. No post-discharge wound complications, screw prominence issues, or revision of S2AI screws were observed during the study's follow-up period. CONCLUSIONS: Robot-assisted S2AI screw placement was found to be safe and accurate in this multicenter study. This is largely attributed to the versatility of the robotic guidance software that allows for detailed and precise preoperative and intraoperative planning.

A narrative review of infection prevention techniques in adult and pediatric spinal deformity surgery.

Spinal infections associated with pediatric and adult spinal deformity surgery are associated with postoperative morbidity and mortality along with elevated health-care costs. Prevention requires meticulous technique by the spine surgeon throughout the perioperative period. There is significant variability in the current practices of spinal deformity surgeons with regard to infection prevention, stemming from the lack of reliable evidence available in the literature. There has also been a lack of literature detailing the difference in infection rates and risk factors between pediatric and adult patients undergoing deformity correction surgery. In this narrative review we looked at 60 studies in the adult population and 9 studies in the pediatric population. Most of these studies of surgical site infections (SSI) in spinal deformity surgery have been performed in adult patients, however it is clear that the pediatric neuromuscular patient requires particular attention that we discuss in detail. This narrative review of the literature outlines evidence and compares and contrasts data for preventive strategies and modifiable risk factors to decrease rates of SSI in the pediatric and adult spinal deformity patient populations. In this review we discuss techniques relating to preoperative cleansing protocols, antibiotic administration, gentle soft tissue handling, appropriate closure, drain usage, and intraoperative technique itself to minimize EBL and operative time.

Protection of Retinal Function by Nucleoside Reverse Transcriptase Inhibitors Following Retinal Ischemia/Reperfusion Injury.

Purpose: Retinal ischemia/reperfusion (I/R) injury is a common cause of visual impairment and blindness for which there remain limited treatment options. Nucleoside reverse transcriptase inhibitors (NRTIs), such as zidovudine (AZT), have been shown to block the NLRP3 inflammasome and prevent retinal degeneration in a mouse model of age-related macular degeneration. The NLRP3 inflammasome has also been shown to be triggered in I/R injury. Therefore, we studied the neuroprotective effects of AZT using a pressure-induced retinal ischemia mouse model. Methods: C57BL/6J mice were randomly assigned to 1 of 2 treatment groups: vehicle-treated retinal I/R injury (n = 6) or AZT-treated retinal I/R injury (n = 6). Vehicle (1% dimethyl sulfoxide [DMSO] in phosphate-buffered saline [PBS]) or AZT 50 mg/kg in 1% DMSO in PBS were injected intraperitoneally twice daily for 5 days. On day 2 of treatment, retinal ischemia was induced by transient elevation of intraocular pressure for 45 min. Scotopic electroretinography (ERG) was used to quantify retinal function before and 1 week after retinal ischemic insult. Retinal morphology was examined 1 week after ischemic insult. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and caspase 1 immunostaining was performed 24 h after retinal I/R injury. Results: Following I/R injury, ERG a- and b-wave amplitudes were significantly reduced in the vehicle-treated mice. AZT treatment significantly attenuated I/R-induced loss of retinal function as compared with vehicle-treated mice. Additionally, AZT-treated mice experienced significantly less inner retinal thinning as compared with vehicle-treated mice. TUNEL-positive cells were prevalent in the vehicle-treated I/R injury mouse retinas compared with the AZT-treated I/R injury mouse retinas. More caspase-1 immunoreactivity was detected in ganglion cell layer and inner nuclear layer (INL) in vehicle-treated I/R injury group than in AZT-treated I/R injury group. Conclusion: AZT treatment resulted in relative preservation of retinal structure and function following ischemic insult as compared with controls. This suggests AZT may have therapeutic value in the management of retinal ischemic diseases.

Is there a difference between navigated and non-navigated robot cohorts in robot-assisted spine surgery? A multicenter, propensity-matched analysis of 2,800 screws and 372 patients.

BACKGROUND CONTEXT: Robot-assisted spine surgery continues to rapidly develop as evidenced by the growing literature in recent years. In addition to demonstrating excellent pedicle screw accuracy, early studies have explored the impact of robot-assisted spine surgery on reducing radiation time, length of hospital stay, operative time, and perioperative complications in comparison to conventional freehand technique. Recently, the Mazor X Stealth Edition was introduced in 2018. This robotic system integrates Medtronic's Stealth navigation technology into the Mazor X platform, which was introduced in 2016. It is unclear what the impact of these advancements have made on clinical outcomes. PURPOSE: To compare the outcomes and complications between the most recent iterations of the Mazor Robot systems: Mazor X and Mazor X Stealth Edition. STUDY DESIGN: Multicenter cohort PATIENT SAMPLE: Among four different institutions, we included adult (≥18 years old) patients who underwent robot-assisted spine surgery with either the Mazor X (non-navigated robot) or Stealth (navigated robot) platforms. OUTCOME MEASURES: Primary outcomes included robot time per screw, fluoroscopic radiation time, screw accuracy, robot abandonment, and clinical outcomes with a minimum 90 day follow up. METHODS: A one-to-one propensity-score matching algorithm based on perioperative factors (e.g. demographics, comorbidities, primary diagnosis, open vs. percutaneous instrumentation, prior spine surgery, instrumented levels, pelvic fixation, interbody fusion, number of planned robot screws) was employed to control for the potential selection bias between the two robotic systems. Chi-square/fisher exact test and t-test/ANOVA were used for categorical and continuous variables, respectively. RESULTS: From a total of 646 patients, a total of 372 adult patients were included in this study (X: 186, Stealth: 186) after propensity score matching. The mean number of instrumented levels was 4.3. The mean number of planned robot screws was 7.8. Similar total operative time and robot time per screw occurred between cohorts (p>0.05). However, Stealth achieved significantly shorter fluoroscopic radiation time per screw (Stealth: 7.2 seconds vs. X: 10.4 seconds, p<.001) than X. The screw accuracy for both robots was excellent (Stealth: 99.6% vs. X: 99.1%, p=0.120). In addition, Stealth achieved a significantly lower robot abandonment rate (Stealth: 0% vs. X: 2.2%, p=0.044). Furthermore, a lower blood transfusion rate was observed for Stealth than X (Stealth: 4.3% vs. X: 10.8%, p=0.018). Non-robot related complications such as dura tear, motor/sensory deficits, return to the operating room during same admission, and length of stay was similar between robots (p>0.05). The 90-day complication rates were low and similar between robot cohorts (Stealth: 5.4% vs. X: 3.8%, p=0.456). CONCLUSION: In this multicenter study, both robot systems achieved excellent screw accuracy and low robot time per screw. However, using Stealth led to significantly less fluoroscopic radiation time, lower robot abandonment rates, and reduced blood transfusion rates than Mazor X. Other factors including length of stay, and 90-day complications were similar.

Pathophysiological mechanisms underlying gastrointestinal symptoms in patients with COVID-19.

Gastrointestinal (GI) symptoms, such as diarrhea, abdominal pain, vomiting, and anorexia, are frequently observed in patients with coronavirus disease 2019 (COVID-19). However, the pathophysiological mechanisms connecting these GI symptoms to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections remain elusive. Previous studies indicate that the entry of SARS-CoV-2 into intestinal cells leads to downregulation of angiotensin converting enzyme 2 (ACE2) receptors resulting in impaired barrier function. While intestinal ACE2 functions as a chaperone for the amino acid transporter B0AT1, the B0AT1/ACE2 complex within the intestinal epithelium acts as a regulator of gut microbiota composition and function. Alternations to the B0AT1/ACE2 complex lead to microbial dysbiosis through increased local and systemic immune responses. Previous studies have also suggested that altered serotonin metabolism may be the underlying cause of GI disorders involving diarrhea. The findings of elevated plasma serotonin levels and high fecal calprotectin in COVID-19 patients with diarrhea indicate that the viral infection evokes a systemic inflammatory response that specifically involves the GI. Interestingly, the elevated proinflammatory cytokines correlate with elevated serotonin and fecal calprotectin levels further supporting the evidence of GI inflammation, a hallmark of functional GI disorders. Moreover, the finding that rectal swabs of COVID-19 patients remain positive for SARS-CoV-2 even after the nasopharynx clears the virus, suggests that viral replication and shedding from the GI tract may be more robust than that of the respiratory tract, further indicating fecal-oral transmission as another important route of viral spread. This review summarized the evidence for pathophysiological mechanisms (impaired barrier function, gut inflammation, altered serotonin metabolism and gut microbiota dysbiosis) underlying the GI symptoms in patients with COVID-19.

Do robot-related complications influence 1 year reoperations and other clinical outcomes after robot-assisted lumbar arthrodesis? A multicenter assessment of 320 patients.

BACKGROUND: Robot-assisted platforms in spine surgery have rapidly developed into an attractive technology for both the surgeon and patient. Although current literature is promising, more clinical data is needed. The purpose of this paper is to determine the effect of robot-related complications on clinical outcomes METHODS: This multicenter study included adult (≥18 years old) patients who underwent robot-assisted lumbar fusion surgery from 2012-2019. The minimum follow-up was 1 year after surgery. Both bivariate and multivariate analyses were performed to determine if robot-related factors were associated with reoperation within 1 year after primary surgery. RESULTS: A total of 320 patients were included in this study. The mean (standard deviation) Charlson Comorbidity Index was 1.2 (1.2) and 52.5% of patients were female. Intraoperative robot complications occurred in 3.4% of patients and included intraoperative exchange of screw (0.9%), robot abandonment (2.5%), and return to the operating room for screw exchange (1.3%). The 1-year reoperation rate was 4.4%. Robot factors, including robot time per screw, open vs. percutaneous, and robot system, were not statistically different between those who required revision surgery and those who did not (P>0.05). Patients with robot complications were more likely to have prolonged length of hospital stay and blood transfusion, but were not at higher risk for 1-year reoperations. The most common reasons for reoperation were wound complications (2.2%) and persistent symptoms due to inadequate decompression (1.5%). In the multivariate analysis, robot related factors and complications were not independent risk factors for 1-year reoperations. CONCLUSION: This is the largest multicenter study to focus on robot-assisted lumbar fusion outcomes. Our findings demonstrate that 1-year reoperation rates are low and do not appear to be influenced by robot-related factors and complications; however, robot-related complications may increase the risk for greater blood loss requiring a blood transfusion and longer length of stay.

Complications in ambulatory pediatric patients with nonidiopathic spinal deformity undergoing fusion to the pelvis using the sacral-alar-iliac technique within 2 years of surgery.

OBJECTIVE: Significant investigation in the adult population has generated a body of research regarding proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following long fusions to the sacrum and pelvis. However, much less is known regarding early complications, including PJK and PJF, in the ambulatory pediatric patient. As such, the objective of this study was to address the minimal literature on early complications after ambulatory pediatric patients underwent fusion to the sacrum with instrumentation to the pelvis in the era of sacral-alar-iliac (S2AI) instrumentation. METHODS: The authors performed a retrospective review of pediatric patients with nonidiopathic spinal deformity < 18 years of age with ambulatory capacity who underwent fusion to the pelvis at a multisurgeon pediatric academic spine practice from 2016 to 2018. All surgeries were posterior-only approaches with S2AI screws as the primary technique for sacropelvic fixation. Descriptive, outcome, and radiographic data were obtained. The definition of PJF included symptomatic PJK presenting as fracture, screw pullout, or disruption of the posterior osseoligamentous complex. RESULTS: Twenty-five patients were included in this study. Nine patients (36.0%) had 15 complications for an overall complication rate of 60.0%. Unplanned return to the operating room occurred 8 times in 6 patients (24.0%). Four patients (16.0%) had wound issues (3 with deep wound infection and 1 with wound breakdown) requiring reoperation. Three patients (12.0%) had PJF, all requiring reoperation. A 16-year-old female patient with syndromic scoliosis underwent extension of fusion due to posterior tension band failure at 6 months. A 17-year-old male patient with neuromuscular scoliosis underwent extension of fusion due to proximal screw pullout at 5 months. A 10-year-old female patient with congenital scoliosis underwent extension for PJF at 5 months following posterior tension band failure. One patient had pseudarthrosis requiring reoperation 20 months postoperatively. CONCLUSIONS: Fixation to the pelvis enables significant deformity correction, but with rather high rates of complications and unexpected returns to the operating room. Considerations of sagittal plane dynamics for PJK and PJF should be strongly analyzed when performing fixation to the pelvis in ambulatory pediatric patients.

Flexion-extension standing radiographs underestimate instability in patients with single-level lumbar spondylolisthesis: comparing flexion-supine imaging may be more appropriate.

BACKGROUND: Generally, most spine surgeons agree that increased segmental motion viewed on flexion-extension radiographs is a reliable predictor of instability; however, these views can be limited in several ways and may underestimate the instability at a given lumbar segment. METHODS: Consecutively collected adult (≥18 years old) patients with symptomatic single-level lumbar spondylolisthesis were reviewed from a two-surgeon database from 2015 to 2019. Routine standing lumbar X-rays (neutral, flexion, extension) and supine lumbar MRI (sagittal T2-weighted imaging sequence) were performed. Patients were excluded if they had prior lumbar surgery, missing radiographic data, or if the time between X-rays and MRI was >6 months. RESULTS: All 39 patients with symptomatic, single-level lumbar spondylolisthesis were identified. The mean age was 57.3±16.7 years and 66% were female. There was good intra- and inter-rater reliability agreement between measured values on the presence of instability. The slip percentage (SP) difference was significantly highest in the flexion-supine (FS) (5.7 mm, 12.3%) and neutral standing-supine (NS) (4.3 mm, 8.7%) groups, both of which were significantly higher compared with the flexion-extension (FE) group (1.8 mm, 4.5%, P<0.001). Ventral instability based on SP >8% was observed more frequently in FS (79.5%) and NS (52.6%) groups compared with FE group (16.7%, P<0.001). No statistically significant correlation was found between SP and disc angle for all radiographic views. CONCLUSIONS: Comparing standing lateral and flexion X-rays with supine MRIs provides higher sensitivity to assess instability than standard flexion-extension radiographs. The FS and NS comparisons also show greater slip percentage differences at higher slip grades, but not at different lumbar levels. These changes are not dependent on age or gender.

The role of ketamine in opioid-free spinal deformity surgery: is it possible and beneficial?

BACKGROUND: As the opioid epidemic in the United States has continued to gain momentum in recent years, the current study aims to explore the efficacy of ketamine in a traditionally challenging setting regarding pain control, and contribute toward developing an opioid-free intraoperative pain protocol in spinal deformity surgery. METHODS: Fifty-four patients who underwent spinal deformity surgery between January 1, 2017 and December 31, 2017 by one senior surgeon were included. Demographic data and preoperative opioid use was collected. Surgical details including number of levels fused, estimated blood loss, and operative time was also collected. All patients received a hydromorphone patient-controlled anesthesia (PCA) device postoperatively. 36/54 patients received perioperative ketamine during their procedure, both intraoperatively and postoperatively. The consumption of postoperative hydromorphone and the ratio of doses given by doses attempted postoperatively were recorded. Patient charts were also reviewed for documented ileus during their inpatient stay. RESULTS: Mean age was 49 years, and 31% were male. Average BMI was 24.3 kg/m2. The average number of levels fused was 11.6. Mean operative time was 10.7 hrs, and average EBL was 1,522 mL. The mean length of stay was 8 days. Average postoperative PCA use of hydromorphone in the no ketamine group (NK) (n=18) was 5.99 mg compared to 6.91 mg for those who received perioperative ketamine (K) (n=36); there was no significant difference between populations (P=0.57), although the variances was significant (P=0.044). There was no correlation between intraoperative ketamine and postoperative PCA use (r=-0.05; P=0.72). Additionally, there was no correlation between postoperative PCA use and dose of postoperative ketamine received (r=-0.15; P=0.27). The ratio of doses given: attempted was 0.61 in the NK group and 0.59 in those in the K group (P=0.79). Average postoperative hydromorphone use was 5.48 mg in patients that did not use opioids preoperatively (n=39) compared to 12.77 mg in those who used opioids preoperatively (n=9; P=0.0003). 9/54 patients had a documented ileus during their admission, while 4/9 (11%) had received ketamine (P=0.095). CONCLUSIONS: Though our study showed no significant change in postoperative opioid requirement in our population, our results show that integration of ketamine in these extensive operations fare similarly to traditional opioid-based regimens. There was also no significant association seen between ketamine use and adverse side effects such as ileus. At our institution we are currently establishing opioid-free intraoperative pain protocols that use ketamine as an adjunct, and further study will explore the effect this may have on postoperative opioid consumption for spinal surgery patients as well as postoperative patients in general.

Postoperative COVID-19 Pneumonia following Resection of a Large Thoracic Chondrosarcoma.

CASE: A 57-year-old man presenting with two months of insidious shoulder pain was found to have a large thoracic chondrosarcoma invading the spinal canal. The patient's orthopedic oncologist organized an interdisciplinary team including interventional radiology, thoracic surgery, neurosurgery, and plastic surgery. This allowed safe, en bloc tumor resection. The patient's postoperative course was complicated by COVID-19 pneumonia, which was rapidly identified and medically managed with full recovery. CONCLUSION: Postoperative COVID-19 pneumonia can present insidiously and mimic other postoperative complications. Early identification and testing can promote rapid isolation, proper personal protective equipment use, and guide outcome-improving treatments.