Faculty Bibliography

BACKGROUND CONTEXT/BACKGROUND:Lateral lumbar interbody fusion is a popular technique used in spine surgery. It is minimally invasive, provides indirect decompression, and allows for coronal plane deformity correction. Despite these benefits, the approach to lateral lumbar interbody fusion has been linked to complications associated with the lumbosacral plexus and vascular anatomy. As a result, vascular surgeons may be recruited for the exposure portion of the procedure. PURPOSE/OBJECTIVE:The purpose of this study was to compare exposure related complication and post-operative (postop) neuropraxia rates between exposure (EXP) and spine surgeon only (SSO) groups when performing the approach for lateral lumbar interbody fusion (LLIF). STUDY DESIGN/SETTING/METHODS:Retrospective analysis of patients treated at a single institution PATIENT SAMPLE: Patients undergoing LLIF procedures between 2012-2018 OUTCOME MEASURES: Operative time, estimated blood loss, fluoroscopy, length of stay, intra- and post-operative complications, and physiologic measures including pre- and post-operative motor examinations and unresolved neuropraxia METHODS: Patients who underwent LLIF were separated into EXP and SSO groups based on the presence or absence of vascular/general surgeon during the approach. The entire clinical history of patients with a decrease in pre and postop motor examination were reviewed for the presence of neuropraxia. All other intra- and postop exposure related complications were recorded for comparison. PSM was performed to account for age, Charlston Comorbity Index (CCI) % LLIFs including L4-L5, and number levels fused. Independent T-test and Chi-squared analyses were used to identify significant differences between EXP and SSO groups. Statistical significance was set at p<0.05. RESULTS:Two hundred seventy-five patients underwent LLIF procedures, 155 SSO and 120 EXP. Post-operatively, 26 patients (11.1%) experienced a drop in any MRC score, and two patients (0.7%) experience unresolved quadriceps palsies. The mean recovery time for MRC scores was 84.4 days. Other complications included 2 pneumothoraces (0.7%), 1 iliac vein injury (0.4%), 14 cases of ileus (5.1%), 3 pulmonary emboli (1.1%), 2 deep vein thrombosis (0.7%), 3 cases of abdominal wall paresis (1.1%), and one abdominal hematoma (0.4%). After PSM, demographics including age, gender, BMI, CCI, levels fused and operative time were similar between cohorts. Twenty patients had changes in pre- to postop motor scores (SSO 9.4%, EXP 12.4%, p>0.05). Iliopsoas motor scores decreased at the highest rate (EXP 12.4%, 8.2% SSO, p>0.05) followed by quadriceps (EXP 5.2%, SSO 4.7%, p>0.05). One SSO patient's postop course was complicated by a foot drop but returned to baseline within 1-year. One patient in EXP group developed an unresolved quadriceps palsy (EXP 1.0%, SSO 0.0% p>0.05). Intra-op exposure complications included one pneumothorax (EXP 1.0%, SSO 0.0%, p>0.05). There were no differences in PE/DVT, Ileus, or LOS. In the EXP cohort, three patients experienced abdominal wall paresis (EXP 2.9%, SSO 0.00%, p=0.246). CONCLUSIONS:Comparing the LLIF exposures performed by EXP and SSO, we found no significant difference in the rates of complications. Additional research is needed to determine the etiology of the abdominal wall complications. In conclusion, neuropraxia- and approach-related complications are similarly low between exposure and spine surgeons.

STUDY DESIGN/UNASSIGNED:Retrospective clinical review. OBJECTIVE/UNASSIGNED:To assess the use of intraoperative computed tomography (CT) image-guided navigation (IGN) and robotic assistance in posterior lumbar surgery and their relationship with patient radiation exposure and perioperative outcomes. METHODS/UNASSIGNED:Patients ≥18 years old undergoing 1- to 2-level transforaminal lateral interbody fusion in 12-month period were included. Chart review was performed for pre- and intraoperative data on radiation dose and perioperative outcomes. All radiation doses are quantified in milliGrays (mGy). Univariate analysis and multivariate logistic regression analysis were utilized for categorical variables. One-way analysis of variance with post hoc Tukey test was used for continuous variables. RESULTS/UNASSIGNED:= .313, .051, and .644, respectively). CONCLUSION/UNASSIGNED:IGN and robotic assistance in posterior lumbar fusion were associated with higher intraoperative and total-procedure radiation exposure than open cases without IGN/robotics, but significantly less than MIS without IGN/robotics, without differences in perioperative outcomes. Fluoro-MIS procedures reported highest radiation exposure to patient, and of equal concern is that the proportion of total radiation dose also applied to the surgeon and operating room staff in fluoro-MIS group is higher than in IGN/robotics and open groups.

STUDY DESIGN/METHODS:Retrospective analysis OBJECTIVE.: Determine whether deformity corrections should vary by pelvic incidence (PI). SUMMARY OF BACKGROUND DATA/BACKGROUND:Alignment targets for deformity correction have been reported for various radiographic parameters. The T1 pelvic-angle (TPA) has gained in applications for ASD surgical-planning since it directly measures spinal alignment separate from pelvic- and lower-extremity compensation. Recent studies have demonstrated that ASD corrections should be age specific. METHODS:A prospective database of consecutive ASD patients was analyzed in conjunction with a normative spine database. Clinical measures of disability included the Oswestry Disability Index (ODI) and SF-36 Physical Component Score (PCS). Baseline relationships between TPA, age, PI and ODI/SF-36 PCS scores were analyzed in the ASD and asymptomatic patients. Linear regression modeling was used to determine alignment targets based on PI and age-specific normative SF-36-PCS values. RESULTS:903 ASD patients (mean 53.7y) and 111 normative subjects (mean 50.7y) were included. Patients were subanalyzed by PI: low, medium, high (<40, 40-75, >75); and age: elderly(>65y, n = 375) middle age(45-65y, n = 387) and young(18-45y, n = 141). TPA and SRS-Schwab parameters correlated with age and PI in ASD and normative subjects (r = .42, p < .0001). ODI correlated with PCS(r = .71, p < .0001). Linear regression analysis using age-normative SF-36-PCS values demonstrated that ideal spinopelvic alignment is less strict with increasing PI and age. CONCLUSIONS:Targets for ASD correction should vary by age and PI. This is demonstrated in both asymptomatic and ASD subjects. Using age-normative SF-36 PCS values, alignment targets are described for different age and PI categories. High-PI patients do not require as rigorous realignments to attain age-specific normative levels of health status. As such, sagittal spinal alignment targets increase with increasing age as well as PI. LEVEL OF EVIDENCE/METHODS:3.

STUDY DESIGN/METHODS:Single-center retrospective study. OBJECTIVE:Investigate how differing degrees of PI modulate the recruitment of pelvic tilt (PT) in response to similar amounts of sagittal malalignment as measured by T1-Pelvic Angle (TPA). SUMMARY OF BACKGROUND DATA/BACKGROUND:Past research has shown that some patients do not recruit PT in response to sagittal malalignment. Given the anatomic relationship between PI and PT, we sought to determine whether differing PI is associated with variable recruitment of PT. METHODS:Single-center retrospective study of 2077 patients undergoing full body radiographs and TPA>10°. Five groups of patients (Very Low, Low, Average, High, and Very High PI) were defined utilizing PI ranges on a gaussian distribution. Linear regression (LR) evaluated correlation of TPA to PT within each PI group. Multivariate LR evaluated whether correlation between TPA and PT differed between each PI group. RESULTS:Mean PT increased with increasing levels of PI (p < 0.05). Within the full cohort, PT correlated with TPA (r = 0.80, p < 0.001). Multivariate LR revealed significant differences between slopes and intercepts of the linear relationship between PT and TPA within the PI groups. Compared to patients with an average PI, patients with Very Low PI had 3.4° lower PT while holding TPA constant (p < 0.001). Further, patients with Very High PI displayed a PT of 1.9° higher than patients with an Average PI while holding TPA constant (p = 0.01). A similar difference of -1.8°, and 1.2° with respect to the Average PI group was observed in the Low and High PI groups, respectively (p < 0.001). Means and standard deviations of PT at varying levels of TPA were defined for PI groups. CONCLUSIONS:This is the first study which demonstrated that PI is associated with varied recruitment of PT while maintaining constant sagittal malalignment. The results reported herein are intended to allow surgeons to assess a patient's magnitude of compensatory PT for an individual patient's PI. LEVEL OF EVIDENCE/METHODS:3.

STUDY DESIGN/UNASSIGNED:This was a single-center retrospective review. OBJECTIVES/UNASSIGNED:To explore how age and gender affect PROMIS scores compared with traditional health-related quality of life (HRQL) in spine patients. METHODS/UNASSIGNED:Patients presenting with a primary complaint of back pain (BP) or neck pain (NP) were included. Legacy HRQLs were Oswestry Disability Index (ODI), Neck Disability Index (NDI), and Visual Analogue Scale (VAS). PROMIS Physical Function (PF), Pain Intensity (Int), and Pain Interference (Inf) were also administered to patients in a clinical setting. Patients were grouped by chief complaint, age (18-44, 45-64, 65+ years) and gender. Two parallel analyses were conducted to identify the effects of age and gender on patient-reported outcomes. Age groups were compared after propensity-score matching by VAS-pain and gender. Separately, genders were compared after propensity-score matching by age and VAS-pain. RESULTS/UNASSIGNED:= .022) but not PROMIS-Int or PROMIS-Inf. CONCLUSIONS/UNASSIGNED:Age and gender confound traditional HRQLs as well as PROMIS domains. However, PROMIS offers age and gender-specific scores, which traditional HRQLs lack.

STUDY DESIGN/METHODS:Retrospective review of a prospectively-collected database. OBJECTIVE:To define a simplified singular measure of cervical deformity (CD), C2 slope (C2S), which correlates with post-operative outcomes. SUMMARY OF BACKGROUND DATA/BACKGROUND:Sagittal malalignment of the cervical spine, defined by the cervical sagittal vertical axis (cSVA), has been associated with poor outcomes following surgical correction of the deformity. There has been a proliferation of parameters to describe cervical deformity (CD). This added complexity can lead to confusion in classifying, treating and assessing outcomes of CD surgery. METHODS:A prospective database of CD patients was analyzed. Inclusion criteria were cervical kyphosis>10°, cervical scoliosis>10°, cSVA>4 cm, or chin-brow vertical angle (CBVA) >25°. Patients were categorized into two groups and compared based on whether the apex of the deformity was in the cervical (C) or the cervicothoracic (CT) region. Radiographic parameters were correlated to C2S, T1-slope (T1S) and 1-year health-related quality-of-life (HRQL) outcomes as measured by the EuroQol 5 Dimension questionnaire (EQ5D), modified Japanese Orthopedic Association Scale (mJOA), numeric rating scale for neck pain (NRS neck), and the Neck Disability Index (NDI). RESULTS:104 CD patients (C = 74, CT = 30; mean age 61y, 56% women, 42% revisions) were included. CT patients had higher baseline cSVA and T1S (p < 0.05). C2S correlated with T1 slope minus cervical lordosis (TS-CL) (r = 0.98, p < 0.001) and C0-C2 angle, cSVA, CL, T1S (r = 0.37-0.65, p < .001). Correlation of cSVA with C0-C2 was weaker (r = 0.48, p < .001). At 1-year postoperatively, higher C2S correlated with worse EQ-5D (r = 0.28, p = .02); in CT patients, higher C2S correlated with worse NDI, mJOA, NRS neck and EQ5D (all r > 0.5, p≤.05). Using linear regression, moderate disability by EQ5D corresponded to C2S of 20°(r = 0.08). For CT patients, C2S = 17° corresponded to moderate disability by NDI (r = 0.4), and C2S = 20° by EQ5D (r = 0.25). CONCLUSION/CONCLUSIONS:C2S correlated with upper-cervical and subaxial alignment. C2S correlated strongly with TS-CL (R = .98, p < .001) because C2S is a mathematical approximation of TS-CL. C2S is a useful marker of CD, linking the occipitocervical and cervico-thoracic spine. C2S defines the presence of a mismatch between cervical lordosis and thoracolumbar alignment. Worse 1-year postoperative C2 slope correlated with worse health outcomes. LEVEL OF EVIDENCE/METHODS:3.

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.

Metabolic syndrome is a clustering of clinical findings defined in the literature including hypertension, high glucose, abdominal obesity, high triglyceride, and low high-density lipoprotein cholesterol levels. The purpose of this study was to assess perioperative outcomes in patients undergoing spine fusion surgery with (MetS) and without (no-MetS) a history of metabolic syndrome. Included: Patients ≥18 yrs old undergoing spine fusion procedures diagnosed with MetS components with BL and 1-year follow-up were isolated in a single-center database. Patients in the two groups were propensity score matched for levels fused. 250 spine fusion patients (58 yrs, 52.2%F, 39.0 kg/m²) with an average CCI of 1.92 were analyzed. 125 patients were classified with MetS (60.2 yrs, 52%F, CCI: 3.2). MetS patients were significantly older (p = 0.012). MetS patients underwent significantly more open (Met-S: 78.4% vs No-MetS: 45.6%, p < 0.001) and posterior approached procedures (Met-S: 60.8% vs No-MetS: 47.2%, p = 0.031). Mean operative time: 272.4 ± 150 min (MetS: 288.1 min vs. no-MetS: 259.7; p = 0.089). Average length of stay: 4.6 days (MetS: 5.27 vs no-MetS: 3.95; p = 0.095). MetS patients had more post-operative complications (29.6% vs. 18.4%; p = 0.038), specifically neuro (6.4% vs 2.4%), pulmonary (4% vs. 1.6%), and urinary (4.8% vs 2.4%) complications. Binary logistic regression analyses found that MetS was an independent risk factor for post-operative complications (OR: 1.865 [1.030-3.375], p = 0.040). With longer surgeries and greater open-exposure types, MetS patients were at greater risk for complications, despite controlling for total number of levels fused. Surgeons should be aware of the increased threat to spine surgery patients with metabolic syndrome in order to optimize surgical decision-making.

STUDY DESIGN/METHODS:Retrospective review. OBJECTIVE:The aim of this study was to develop a novel surgical invasiveness index for cervical deformity (CD) surgery that incorporates CD-specific parameters. SUMMARY OF BACKGROUND DATA/BACKGROUND:There has been a surgical invasiveness index for general spine surgery and adult spinal deformity, but a CD index has not been developed. METHODS:CD was defined as at least one of the following: C2-C7 Cobb > 10°, cervical lordosis (CL) > 10°, cervical sagittal vertical axis (cSVA) > 4 cm, chin brow vertical angle (CBVA) > 25°. Consensus from experienced spine and neurosurgeons selected weightings for each variable that went into the invasiveness index. Binary logistic regression predicted high operative time (>338 minutes), estimated blood loss (EBL) (>600 cc), or length of stay (LOS; > 5 days) based on the median values of operative time, EBL and LOS. Multivariable regression modeling was utilized to construct a final model incorporating the strongest combination of factors to predict operative time, LOS, and EBL. RESULTS:85 CD patients were included (61yrs, 66%F). The variables in the newly developed CD invasiveness index with their corresponding weightings were: history of prior cervical surgery (3), anterior cervical discectomy and fusion (ACDF) (2/level), corpectomy (4/level), levels fused (1/level), implants (1/level), posterior decompression (2/level), Smith-Peterson osteotomy (2/level), three column osteotomy (8/level), fusion to upper cervical spine (2), absolute change in T1 slope minus cervical lordosis (TS-CL), cSVA, T4-T12 thoracic kyphosis and sagittal vertical axis (SVA) from baseline to 1-year. The newly developed CD-specific invasiveness index strongly predicted long LOS (R = 0.310, p < 0.001), high EBL (R = 0.170, p = 0.011), and extended operative time (R = 0.207, p = 0.031). A second analysis used multivariable regression modeling to determine which combination of factors in the newly developed index were the strongest determinants of operative time, LOS, and EBL. The final predictive model included: number of corpectomies, levels fused, decompression, combined approach, and absolute changes in SVA, cSVA and TK. This model predicted EBL (R = 0.26), operative time (R = 0.12), and LOS (R = 0.13). CONCLUSIONS:Extended length of stay, operative time, and high blood loss were strongly predicted by the newly developed CD invasiveness index, incorporating surgical factors and radiographic parameters clinically relevant for patients undergoing cervical deformity corrective surgery. LEVELS OF EVIDENCE/METHODS:4.

BACKGROUND:Distal junctional kyphosis (DJK) development after cervical deformity (CD)-corrective surgery is a growing concern for surgeons and patients. Few studies have investigated risk factors that predict the occurrence of DJK. OBJECTIVE:To predict DJK development after CD surgery using predictive modeling. METHODS:CD criteria was at least one of the following: C2-C7 Coronal/Cobb > 10°, C2-7 sagittal vertical axis (cSVA) > 4 cm, chin-brow vertical angle > 25°. DJK was defined as the development of an angle <-10° from the end of fusion construct to the second distal vertebra, and change in this angle by <-10° from baseline to postoperative. Baseline demographic, clinical, and surgical information were used to predict the occurrence of DJK using generalized linear modeling both as one overall model and as submodels using baseline demographic and clinical predictors or surgical predictors. RESULTS:One hundred seventeen CD patients were included. At any postoperative visit up to 1 yr, 23.1% of CD patients developed DJK. DJK was predicted with high accuracy using a combination of baseline demographic, clinical, and surgical factors by the following factors: preoperative neurological deficit, use of transition rod, C2-C7 lordosis (CL)<-12°, T1 slope minus CL > 31°, and cSVA > 54 mm. In the model using only baseline demographic/clinical predictors of DJK, presence of comorbidities, presence of baseline neurological deficit, and high preoperative C2-T3 angle were included in the final model (area under the curve = 87%). The final model using only surgical predictors for DJK included combined approach, posterior upper instrumented vertebrae below C4, use of transition rod, lack of anterior corpectomy, more than 3 posterior osteotomies, and performance of a 3-column osteotomy. CONCLUSION/CONCLUSIONS:Preoperative assessment and consideration should be given to these factors that are predictive of DJK to mitigate poor outcomes.