Faculty Bibliography

BACKGROUND CONTEXT: Spine surgery is usually associated with large blood loss necessitating blood transfusions. Blood loss-associated morbidity can be due to direct risks, such as hypotension and organ damage, or as result of blood transfusions. The antifibrinolytic, tranexamic acid (TXA) is a lysine analogues which inhibits activation of plasminogen and has shown to be beneficial in reducing surgical blood loss. PURPOSE: The purpose of the meta-analysis is to consolidate the findings of randomized controlled trials (RCTs) investigating the use of TXA on surgical bleeding in spine surgery. STUDY DESIGN: Meta-analysis STUDY SAMPLE: RCTs investigating effectiveness of intravenous TXA in reducing blood loss in spine surgery, compared to a placebo/ no treatment group. METHODS: MEDLINE, Embase, Cochrane controlled trials register and Google Scholar were used to identify RCTs published before January 2014 that examined the effectiveness of intravenous TXA on reduction of blood loss and blood transfusions, compared to a placebo/ no treatment group in spine surgery. Meta analysis was performed using RevMan 5. Weighted mean difference was used to summarize findings across the trials for continuous outcomes. Dichotomous data were expressed as risk ratio with 95% confidence intervals (CI). A p < 0.05 was considered statistically significant. RESULTS: Eleven RCTs were included for TXA (644 total patients). TXA reduced intraoperative, postoperative and total blood loss by an average of 219 ml ([-322,-116], p<0.05), 119 ml ([-141,-98], p<0.05) and 202 ml ([-299, -105], p<0.05) respectively. TXA led to a reduction in proportion of patients who received a blood transfusion (RR 0.67 ([0.54, 0.83], p <0.05) relative to placebo. There was one myocardial infarction (MI) in the TXA group and one deep vein thrombosis (DVT) in placebo. CONCLUSION: TXA reduces surgical bleeding and transfusion requirements in patients undergoing spine surgery. TXA does not appear to be associated with an increased incidence of pulmonary embolism, DVT, or MI.

The purpose of this study was to investigate the potential of a high-throughput, easily implemented, cost-effective, video analysis software-based mobility protocol to quantify spine kinematics. This prospective cohort study of clinical biomechanics implemented 2-dimensional (2D) image processing at a tertiary-care academic institution. Ten healthy, able-bodied volunteers were recruited for 2D videography of gait and functional motion. The reliability of a 2D video analysis software program for gait and range of motion metrics was evaluated over 2 independent experimental sessions, assessing for inter-trial, inter-session, and inter-rater reliability. Healthy volunteers were evaluated for simple forward and side bending, rotation, treadmill stride length, and more complex seated-to-standing tasks. Based on established intraclass correlation coefficients, results indicated that reliability was considered good to excellent for simple forward and side bending, rotation, stride length, and more complex sit-to-standing tasks. In conclusion, a cost-effective, 2D, video analysis software-based mobility protocol represents a feasible and clinically useful approach for objective spine kinematics and gait metrics. As the complication rate of operative management in the setting of spinal deformity is weighed against functional performance and quality of life measures, an objective analysis tool in combination with an appropriate protocol will aid in clinical assessments and lead to an increased evidence base for management options and decision algorithms.

BACKGROUND CONTEXT: Vertebral compression fractures secondary to low bone mass are responsible for almost 130,000 inpatient admissions and 133,500 emergency department visits annually, totaling over $5 billion of direct inpatient costs. Although most vertebral compression fractures heal within a few months with conservative therapy, a significant portion fail to improve with conservative treatment and require long-term care, conservative treatment, or both. Fractures that fail conservative therapy are treated with vertebral augmentation procedures (VAPs) such as vertebroplasty (VP) and kyphoplasty (KP). Two large randomized clinical trials published in 2009 questioned the efficacy of VP in treatment of VAPs. PURPOSE: This study aimed to investigate trends in utilization of VP and KP between 2005 and 2010 to capture the impact of the 2009 literature on utilization of VAPs. The study also compares patient characteristics and perioperative outcomes between VP and KP to further delineate the risks of each procedure. STUDY DESIGN: Retrospective analysis of national utilization rates, clinical outcomes, patient demographics, and patient comorbidities using a large national inpatient database. PATIENT SAMPLE: A total of 63,459 inpatient admissions from 46 states and more than 1,000 different hospitals were included in the analysis. OUTCOME MEASURES: Length of stay (LOS), total direct cost, mortality, postoperative complications. METHODS: Data were obtained from the National Inpatient Sample database for the period between 2005 and 2010. National Inpatient Sample is the largest publicly available all payer inpatient database in the United States. Patients undergoing VP and KP were identified via corresponding the International Classification of Diseases, 9th Revision procedure codes. National utilization trends were estimated using weights supplied as part of the National Inpatient Sample dataset. Information on patient comorbidities and demographics was collected. A series of univariate and multivarariate analyses were used to identify statistically significant differences in patient characteristics, clinical outcomes, as well as cost and LOS between patients undergoing VP versus KP. RESULTS: A total of 307,050 inpatient VAPs were performed in the United States between 2005 and 2010. Of those procedures, 225,259 were KP and 81,790 were VP. Kyphoplasty utilization showed an increasing trend between 2005 and 2007, increasing from 27 to 33 procedures per 100,000 capita older than 40 years. During the same time period, VP utilization remained constant at approximately nine procedures per 100,000 capita older than 40 years. After 2007, utilization of both VP and KP decreased. The most precipitous decrease in VAP utilization occurred in 2009. Patients undergoing VP were on average older (76.7 vs. 77.8, p<.0001), more frequently women (74.48% vs. 73.15%, p=.00083), and black (1.77% vs. 1.55%, p=.004059). Patients undergoing VP had on average more comorbidities then those undergoing KP. Patients undergoing VP had a higher rate of postoperative anemia secondary to acute bleeding and higher rate of venous thromboembolic events. Those undergoing KP had a greater rate of cardiac complications; however, this difference was not statistically significant when taking into account patient age and comorbidity burden. Vertebroplasty was associated with higher mortality (0.93% vs. 0.60%, p<.001), longer LOS (6.78 vs. 5.05 days, p<.0001), and lower total cost ($42,154 vs. $46,101, p<.0001). CONCLUSIONS: Overall, KP was associated with lower complication rates, shorter LOS, and a higher total direct cost compared with VP. Utilization rates showed a significant decrease since 2009 in both VP and KP, suggesting that both procedures were impacted by the two randomized controlled trials published in 2009 that suggested poor efficacy of VP.

BACKGROUND: Spine procedures continue to increase significantly. As such, a more precise understanding of the anatomy, especially the pars interarticularis (PI) is critical. Current data characterizing the PI level-by-level is lacking. This study analyzed the average PI width at each level of the lumbar spine in order to elucidate statistically significant PI variations between lumbar levels. METHODS: The interpars distance, the narrowest distance between the lateral edges of the left and right PI, was measured directly with calipers on 53 complete lumbar specimens and digitally via Fastrack measurements of 30 sets of lumbar vertebrae. For both methods, the mean interpars distances were compared moving down the lumbar spine. RESULTS: For direct measurements, the average interpars distances increased from L2 to L5. Analysis revealed significant differences across all levels. A significant difference was noted between male and female vertebrae only at L1. For Fastrack measurements, the average interpars distances also increased from L2 to L5. An increase in spinal canal width was observed across all but L1-L2, and an increase in the interpars-to-spinal-canal-width ratio was noted at all levels except L1-L2 and L4-L5. CONCLUSIONS: The amount of bone in the PI available for surgical removal becomes smaller moving from L5 to L1. There is a larger "margin-for-error" at L4 and L5 when decompressing the spinal canal from one side to the other than there is in the upper lumbar spine. At L1 and L2, de- compressing the entire width of the spinal canal leaves only a millimeter of remaining pars on either side. Care should be taken to use "undercutting techniques" in upper lumbar decompressions to preserve the PI.

BACKGROUND: Antifibrinolytics can reduce intraoperative blood loss. The primary aim of this study was to determine the efficacy of intraoperative tranexamic acid, epsilon-aminocaproic acid, and placebo at reducing perioperative blood loss and the transfusion rate in patients with adolescent idiopathic scoliosis undergoing posterior spinal arthrodesis. METHODS: This is a prospective, randomized, double-blind comparison of tranexamic acid, epsilon-aminocaproic acid, and placebo used intraoperatively in patients with adolescent idiopathic scoliosis. One hundred and twenty-five patients with adolescent idiopathic scoliosis were randomly assigned to the tranexamic acid, epsilon-aminocaproic acid, or control groups. Parameters recorded included estimated blood loss, hematocrit, blood product usage, drain output, and total blood losses. The primary outcomes were intraoperative blood loss and postoperative drainage. Secondary outcomes were transfusion requirements and hematocrit changes both intraoperatively and postoperatively. RESULTS: One hundred and twenty-five patients (ninety-seven female and twenty-eight male, with a mean age of fifteen years) were randomized to receive tranexamic acid (thirty-six patients), epsilon-aminocaproic acid (forty-two patients), or saline solution (forty-seven patients). The groups were similar at baseline, with one exception: the saline solution group had a higher estimated blood volume at baseline than the tranexamic acid group. Both tranexamic acid and epsilon-aminocaproic acid reduced the estimated blood loss per degree and estimated blood loss per pedicle screw. Epsilon-aminocaproic acid, but not tranexamic acid, reduced estimated blood loss and estimated blood loss per level. Tranexamic acid also reduced total blood losses compared with epsilon-aminocaproic acid or saline solution. In an analysis controlling for level, degree, and number of anchors, tranexamic acid reduced drain output and total blood losses. Tranexamic acid or epsilon-aminocaproic acid had a smaller decrease in hematocrit postoperatively. In an analysis controlling for the mean arterial pressure during surgical exposure, tranexamic acid reduced estimated blood loss and total blood losses. Overall, antifibrinolytics (tranexamic acid or epsilon-aminocaproic acid) reduced estimated blood loss, total blood losses, and the decline in hematocrit postoperatively compared with saline solution. There was no difference among the groups with respect to the transfusion rate, duration of surgery, levels fused, or pedicle screws placed. CONCLUSIONS: Tranexamic acid and epsilon-aminocaproic acid reduced operative blood loss but not transfusion rate. Tranexamic acid is more effective at reducing postoperative drainage and total blood losses compared with epsilon-aminocaproic acid. Maintenance of the mean arterial pressure at <75 mm Hg during surgical exposure appears to be critical for maximizing antifibrinolytic benefit. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

OBJECT: Incremental cost-effectiveness analysis is critical to the efficient allocation of health care resources; however, the incremental cost-effectiveness ratio (ICER) of surgical versus nonsurgical treatment for adult spinal deformity (ASD) has eluded the literature, due in part to inherent empirical difficulties when comparing surgical and nonsurgical patients. Using observed preoperative health-related quality of life (HRQOL) for patients who later underwent surgery, this study builds a statistical model to predict hypothetical quality-adjusted life years (QALYs) without surgical treatment. The analysis compares predicted QALYs to observed postoperative QALYs and forms the resulting ICER. METHODS: This was a single-center (Baylor Scoliosis Center) retrospective analysis of consecutive patients undergoing primary surgery for ASD. Total costs (expressed in 2010 dollars) incurred by the hospital for each episode of surgical care were collected from administrative data and QALYs were calculated from the 6-dimensional Short-Form Health Survey, each discounted at 3.5% per year. Regression analysis was used to predict hypothetical QALYs without surgery based on preoperative longitudinal data for 124 crossover surgical patients with similar diagnoses, baseline HRQOL, age, and sex compared with the surgical cohort. Results were projected through 10-year follow-up, and the cost-effectiveness acceptability curve (CEAC) was estimated using nonparametric bootstrap methods. RESULTS: Three-year follow-up was available for 120 (66%) of 181 eligible patients, who were predominantly female (89%) with average age of 50. With discounting, total costs averaged $125,407, including readmissions, with average QALYs of 1.93 at 3-year follow-up. Average QALYs without surgery were predicted to be 1.6 after 3 years. At 3- and 5-year follow-up, the ICER was $375,000 and $198,000, respectively. Projecting through 10-year follow-up, the ICER was $80,000. The 10-year CEAC revealed a 40% probability that the ICER was $80,000 or less, a 90% probability that the ICER was $90,000 or less, and a 100% probability that the ICER was less than $100,000. CONCLUSIONS: Based on the WHO's suggested upper threshold for cost-effectiveness (3 times per capita GDP, or $140,000 in 2010 dollars), the analysis reveals that surgical treatment for ASD is cost-effective after a 10-year period based on predicted deterioration in HRQOL without surgery. The ICER well exceeds the WHO threshold at earlier follow-up intervals, highlighting the importance of the durability of surgical treatment in assessing the value of surgical intervention. Due to the study's methodology, the results are dependent on the predicted deterioration in HRQOL without surgery. As such, the results may not extend to patients whose HRQOL would remain steady without surgery. Future research should therefore pursue a direct comparison of QALYs for surgical and nonsurgical patients to better understand the cost-effectiveness of surgery for the average ASD patient.

BACKGROUND CONTEXT: The maintenance of horizontal gaze is an essential function of upright posture and global sagittal spinal alignment. Horizontal gaze is classically measured by the Chin Brow Vertical Angle (CBVA), which is not readily measured on most lateral spine radiographs. PURPOSE: This study proposes to evaluate the correlation of CBVA with two more accessible angles: the Slope of the Line of Sight (SLS) (slope of Frankfort line: anterior/inferior margin of orbit to the top of the external auditory meatus) and the slope of McGregor's line (McGS). Furthermore, this study also aims to correlate these 3 angles with HRQOL, specifically the Oswestry Disability Index (ODI). STUDY DESIGN/SETTING: Single-center, retrospective, non-consecutive case series. PATIENT SAMPLE: 531 Patients with spinal pathologies (primary cervical, lumbar, or adult scoliosis) from November 2012 to November 2013. OUTCOME MEASURES: Oswestry Disability Index (ODI). METHODS: Patients were identified from a multicenter database of 531 spine patients who underwent full body EOS X-rays with a variety of presenting complaints (primary cervical, lumbar, or adult scoliosis). Exclusion criteria were age<18y, total hip arthroplasty, total knee arthroplasty, neuropathic scoliosis, fractures, and tumor. Correlations between CBVA, SLS, and McGS and were assessed. Using a quadratic regression with ODI and CBVA, we established a low disability range of values for the CBVA and then, by simple regression, a low disability range of values for SLS and McGS. RESULTS: 435 patients were included (67% females, mean age 57 +; 15yo, mean BMI 27.4 +; 6.4 kg/m²). CBVA strongly correlated with SLS (r=.996, p<.001) and McGS (r=.862, p<.001). A significant negative correlation was observed between ODI and all 3 angles (with CBVA: r= -0.232, p=.022, with SLS: r=-0.228, p=.024, with McGS: r=-0.213, p=.036). By applying a quadratic regression on the ODI and CBVA establishing range of values corresponding to low disability (-4.7degree to 17!

BACKGROUND CONTEXT: Previous force plate studies analyzing the impact of sagittal spinal deformity (SSD) on pelvic parameters have demonstrated compensatory mechanisms of translation in addition to rotation. However, compensatory changes in the hip, knee and ankle joints have not been assessed in patients with sagittal malalignment. PURPOSE: This study aims to 1) analyze the relationship between sagittal spinopelvic (SPP) and lower limb (LLP) parameters, 2) to clarify the role of pelvic translation (pelvic shift) and 3) to correlate Oswestry Disability Index with spinopelvic parameters and compensatory mechanisms. STUDY DESIGN/SETTING: Retrospective single center study. PATIENT SAMPLE: From November 2012 to November 2013, 409 patients with spinal deformity and full-body EOS images (EOS system) were included, without age or gender restriction. Patients with only a diagnosis of stenosis or low back pain were excluded. Subjects were grouped by T1 Spino Pelvic inclination (T1SPi): sagittal forward (FW, > 0.6degree), neutral (NE, -6.6degree to 0.6degree) and backward (BW,<-6.6degree). OUTCOME MEASURES: T1SPi, Pelvic Shift (P.Shift), sagittal vertical axis (SVA), pelvic tilt (PT), lumbar lordosis (LL), "pelvic incidence minus lumbar lordosis" (PI-LL), TK (T1T12 kyphosis), T9SPi (T9 spinopelvic inclination), Sacro Femoral Angle (SFA), Knee Angle, Ankle Angle, chin brow vertical angle, and ODI (Oswestry Disability Index). METHODS: Pelvic translation was quantified by Pelvic Shift (the sagittal offset between the postero-superior corner of the sacrum and the anterior cortex of distal tibia). SPP were measured such as: SVA, PT, PI-LL, TK, T9SPi. Hip extension was measured using the SFA (angle between a line from middle of sacral endplate to bicoxo femoral axis and the femoral mechanical axis), Knee Angle (KA, angle of knee flexion), and Ankle Angle (AA, between tibial axis and vertical reference line) were positive in case of flexion. CBVA (chin brow vertical angle, between the chin-brow line and the ver!

BACKGROUND CONTEXT: Adult spinal deformity (ASD) surgery is known for its high complication rate. The incidence of radiographic and implant-related complications in the context of ASD surgery, and risk factors for its development has not been well defined. PURPOSE: This study examines the incidence of radiographic and implant- related complications in ASD surgery and their effect on the rate of reoperation. It also identifies risk factors for the development of radiographic and implant-related complications, and examines their impact on HRQOL. STUDY DESIGN/SETTING: Multicenter, prospective, consecutive case series. PATIENT SAMPLE: 245 surgical ASD patients. OUTCOME MEASURES: Radiographic and implant related complications, ODI, SF-36, and SRS questionnaires. METHODS: A multicenter prospective database of surgical ASD patients was reviewed. Patients with 2-yr follow-up were included. Radiographic and implant-related complications included: implant prominence, breakage, loosening, malposition or dislodgement, proximal / distal junctional kyphosis, pseudoarhrosis, fracture, and imbalance. HRQOL were measured using the ODI, SF-36, and SRS. Univariate testing was performed as appropriate. Multivariate logistic regression modeling was used to determine independent predictors of radiographic and implant related complications. Multivariate repeated measures mixed models were used to examine HRQOL, accounting for confounders. RESULTS: 246 patients met inclusion criteria. The incidence of radiographic and implant-related complications was 31.7%. 52.6% of those patients required reoperation. Rod breakage accounted for 47% of the implant- related complications, and proximal junctional kyphosis (PJK) accounted for 54.5% of radiographic complication Univariate analysis identified the following potential risk factors for radiographic and implant-related complications: weight (p=0.012), ASA (p=0.004), revision setting (p=0.026), stopping the fusion in the lower vs the upper thoracic spine (p=0.005), Schwab PT m!