Faculty Bibliography

Study Design. Retrospective analysis.Objective. To determine patient demographics, incidence of comorbidities and procedure-related complications, and identify risk factors associated with morbidity and mortality after spinal surgery for cauda equina syndrome (CES).Summary of Background Data. To our knowledge, no study has provided nationwide estimates of patient characteristics and procedure-related complication rates after spinal surgery for CES relative to an unaffected population.Methods. Nationwide Inpatient Sample data collected between 2001 and 2010 was analyzed. Discharges with procedural codes for lumbar spinal fusion, decompression, or discectomy were included. The CES cohort included diagnoses of CES, and the unaffected cohort included lumbar spinal pathology diagnoses. Patient demographics, incidence of comorbidities and procedure-related complications, and risk factors associated with morbidity and mortality were compared.Results. Discharges for 11,207 CES and 689,799 unaffected patients were identified. Differences between cohorts were found for demographic and hospital data. Average comorbidity indices for the CES cohort were found to be increased (0.23 vs.0.13, p< 0.0001), as well as the incidence of total procedure-related complications (18.63% vs. 13.12%, p< 0.0001). In-hospital mortality rate was significantly increased for the CES cohort (0.30% vs. 0.08%, p< 0.0001). A number of comorbidities associated with additional risk for morbidity and mortality among the CES cohort were identified.Conclusion. Relative to an unaffected population undergoing similar treatment, CES patients were more likely to have increased associated comorbidities on presentation, as well as increased complication rates with a prolonged hospital course postoperatively. CES was found to carry an increased incidence of procedure-related complications as well as in-hospital mortality. A number of comorbidities associated with additional risk for morbidity and mortality among the CES cohort were identified. This study provides clinically useful data for surgeons to educate patients at risk for morbidity and mortality as well as direct future research to improve patient outcomes.

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.

Object Lateral mass screws (LMS) have been used extensively with a low complication rate in the subaxial spine. Recently, cervical pedicle screws (CPS) have been introduced, and are thought to provide more optimal stabilization of the subaxial spine in certain circumstances. However, because of the concern for neurovascular injury, the routine use of CPS in this location remains controversial. Despite this controversy, however, there are no articles directly comparing screw-related complications of each procedure in the subaxial cervical spine. The purpose of this study was to evaluate screw-related complications of LMS and CPS in the subaxial cervical spine. Methods A PubMed/MEDLINE and Cochrane Collaboration Library search was executed, using the key words "lateral mass screw" and "cervical pedicle screw." Clinical studies evaluating surgical procedures of the subaxial cervical spine in which either LMS or CPS were used and complications were reported were included. Studies in which the number of patients who had subaxial cervical spine surgery and the number of screws placed from C-3 to C-7 could not be specified were excluded. Data on screw-related complications of each study were recorded and compared. Results Ten studies of LMS and 12 studies of CPS were included in the analysis. Vertebral artery injuries were slightly but statistically significantly higher with the use of CPS relative to LMS in the subaxial cervical spine. Although the use of LMS was associated with a higher rate of screw loosening, screw pullout, loss of reduction, pseudarthrosis, and revision surgery, this finding was not statistically significant. Conclusions Based on the available literature, it appears that perioperative neurological and late biomechanical complication rates, including pseudarthrosis, are similarly low for both LMS and CPS techniques. In contrast, vertebral artery injuries, although statistically significantly more common when using CPS, are extremely rare with both techniques, which may justify their nonroutine use in select cases. Given the paucity of well-designed studies available, this recommendation may be a reflection of deficiencies in the available studies. Surgeons using either technique should have intimate knowledge of cervical anatomy and an adequate preoperative evaluation for each patient, with the final selection based on individual case requirements and anatomical limitations.

STUDY DESIGN: Retrospective review. OBJECTIVE: To analyze the trends in complications and mortality after spinal fusions. SUMMARY OF BACKGROUND DATA: Utilization of spinal fusions has been increasing during the past decade. It is essential to evaluate surgical outcomes to better identify patients who benefit most from surgical intervention. Integration of empiric evidence from large administrative databases into clinical decision making is instrumental in providing higher-quality, evidence-based, patient-centered care. METHODS: This study used Nationwide Inpatient Sample data from 2001 through 2010. Patients who underwent spinal fusions were identified using the CCS (Clinical Classifications Software) and ICD-9 (International Classification of Diseases, 9th Revision) codes. Data on patient comorbidities, primary diagnosis, and postoperative complications were obtained via ICD-9 diagnosis codes and via CCS categories. National estimates were calculated using weights provided as part of the database. Time trend analysis for average length of stay, total charges, mortality, and comorbidity burden was performed. Univariate and multivariate models were constructed to identify predictors of mortality and postoperative complications. RESULTS: An estimated 3,552,873 spinal fusions were performed in the United States between 2001 and 2010. The national bill for spinal fusions increased from $10 billion to $46.8 billion. Today, patients are older and have a greater comorbidity burden than 10 years ago. Mortality remained relatively constant at 0.46%, 1.2%, and 0.14% for cervical, thoracic, and lumbar fusions, respectively. Morbidity rates showed an increasing trend at all levels. Multivariate analysis of 19 procedures and patient-related risk factors and 9 perioperative complications identified 85 statistically significant (P< 0.01) interactions. CONCLUSION: The data on perioperative risks and risk factors for postoperative complications of spinal fusions presented in this study is pivotal to appropriate surgical patient selection and well-informed risk-benefit evaluation of surgical intervention.Level of Evidence: N/A.

Study Design. Retrospective review of prospectively collected surgical dataObjective. This study sought to determine the effect of fellow education over the course of the academic year (August - July) on surgical outcomes in adolescent idiopathic scoliosis (AIS). One surgeon and one type of surgery were chosen to minimize confounding factors.Summary of Background Data. Educating and training the next generation of physicians and surgeons is necessary for the survival and continuation of medical care. There has been recent momentum to scientifically document that medical education is safe. Spine surgery is complex and demanding, with a steep learning curve making it an ideal model to detect any potential negative impact of medical education.Methods. Subjects: adolescent patients undergoing posterior spinal surgery, between August 2007-July 2010, by a single senior surgeon at one institution with a fellow as the only surgical assistant. Demographic and perioperative data were collected then segmented by surgical date into quarters according to the rotations of the academic year. One fellow was included in each quarter over four years, resulting in 16 fellows across the four quarters. An ANOVA was used to assess differences in operative time, blood loss, length of stay and complications between the quarters of the year.Results. There were no significant differences between the groups regarding age, sex, or Lenke curve type. No statistically significant differences were found between the four quarters of the fellowship year for estimated blood loss, use of cell saver, length of stay, operative time, and complication rate.Conclusions. This study is the first to show that fellow education over the course of the academic year did not impact the patient outcomes studied. It is clear that while there is significant academic benefit for the fellows as they complete their spine fellowship, there is no negative impact for patients.

BACKGROUND CONTEXT: Surgical planning is essential to attaining adequate radiographic correction, however, there are multiple methods of planning osteotomy procedures. Additionally, several surgical planning parameters are involved in the attempt to achieve ideal spinopelvic alignment in operative cases of adult spinal deformity. It is important for the surgeon to not only understand necessary radiographic thresholds but also to utilize available planning techniques prior to performing surgery. PURPOSE: The purpose of this study was to compare two methods of planning sagittal plane correction, a geometric and a validated formula. STUDY DESIGN/SETTING: Prospective consecutive case series. PATIENT SAMPLE: 26 adult spinal deformity patients requiring sagittal realignment. OUTCOME MEASURES: Radiographic parameters. METHODS: Prospective review of 26 adult patients with realignment procedures. Preoperative surgical plans were collected preop, defining the expected change in lumbar lordosis (LL) and in max kyphosis (mTK). Plan was based on geometrical method as well as a validated formula to predict postoperative SVA and PT. Periop long cassette and postop x-rays were obtained. Expected, predicted, and radiographic measurements (pre- peri-, and postop) were compared. RESULTS: For 6 patients, planning or perioperative X-ray images were unusable due to radiographic quality. The comparison of the two planning methods on the remaining 20 patients revealed significant differences in the planned LL, but no significant difference in mTK or predicted PT and SVA. Respectively 6 (geometric) and 12 (formula) patients were planned to reach IA in all 3 parameters. The comparison of intraoperative radiographs with the planning demonstrated an intra-operative under-correction of LL. Perioperative radiographs were a good prediction of postoperative LL, but a poor predictor of mTK. Postoperative change in mTK was underestimated with the 2 planning methods. Finally, 12 of the 14 patients planned to reach IA in SVA reac!

BACKGROUND CONTEXT: The effects of spinal fusion on gait kinematics in AIS are poorly understood. Center of mass (COM) displacement during gait has been used as an indicator of gait efficiency with the least energy consumption when the COM travels in a straight line. PURPOSE: Sixteen patients with adolescent idiopathic scoliosis (AIS) were studied for the interaction between center of mass and center of pressure (COM-COP) before and after scoliosis fusion surgery to evaluate the effect of fusion and curve correction on measures of balance and efficiency during gait. STUDY DESIGN/SETTING: Prospective clinical cohort. PATIENT SAMPLE: 16 subjects with operative AIS. OUTCOME MEASURES: COM and COP interaction and COM sway. METHODS: Prospective clinical, radiographic, and formal 3D motioncapture gait analysis were collected pre- and post spinal fusion for AIS (n, 5, 16). COM-sway was calculated based on side-to-side displacement from a straight line fitted to the patient's path. In sagittal and coronal planes, the left- and right-sided peak COM-COP inclination angles were also measured during gait. Pre- and Postoperative COM sway, and sagittal/coronal plane left- and right-sided peak inclination angles were evaluated with paired t-test. Multivariate analysis was used to identify radiographic parameters with the greatest influence on motion. RESULTS: Sixteen patients (12 females, age 14.4 +/- 3.8 at surgery, with predominantly 1AN and 5CN curves) were included in the analysis. Sixteen patients were included in the analysis. The preoperative COM peak lateral displacement decreased from a mean of 7.2 cm (SD58.0) to 2.6 cm (SD52.5) (p=0.012). In the sagittal plane left pre- and postoperative means of peak inclination angles were 25.6degree and 21.6degree (p=0.029), and right pre- and postoperative means were 26.4 and 22.8 (p=0.026), while left and right coronal peak inclination did not reach significance (p=0.349 and 0.055, respectively). A multivariate linear regression identified changes in sagittal al!

BACKGROUND CONTEXT: Pre-donation of autologous blood prior to spine fusion for adolescent idiopathic scoliosis (AIS) has been common practice. However, the effect of predonation on pre-incision hematocrit has not been studied. This study aims to determine if pre-donation of autologous blood leads to a lower pre-incision hematocrit. PURPOSE: To compare the effects of autologous blood donation on preincisional hematocrit levels. STUDY DESIGN/SETTING: Retrospective cohort study of prospective randomized trial. PATIENT SAMPLE: Patients (ages 10-21) undergoing posterior spinal fusion in a prospective, randomized controlled trial in which 125 patients were randomized to TXA, EACA, or Saline for surgery from January 2009 to January 2011. Of the 125 patients that enrolled in the study, 28 patients donated blood and 62 patients did not donate blood. 35 patients were omitted as the autologous blood donation status was not clearly documented in the medical record. OUTCOME MEASURES: Primary outcome measure was the pre-incisional hematocrit of patients immediately prior to surgery. METHODS: This is a retrospective review of data from a prospective, randomized controlled trial in which 125 patients were randomized to TXA, EACA, or Saline for surgery from January 2009 to January 2011. As part of the prospective study, all patients had a complete blood count (CBC) drawn just prior to incision. Of the 125 patients that enrolled in the study, 28 patients donated blood and 62 patients did not donate blood. 35 patients were omitted as the autologous blood donation status was not clearly documented in the medical record. Patient demographics and CBC values were compared between groups using a T-test. Statistical significance was achieved at P<0.05. RESULTS: Pre-donation patients (n528) had an average age of 15.662.2and were 75% female (21F, 7M) which was comparable to non-donation patients (n562) who had a mean age of 15.0 +/- 2.3 and were 82% female (51F, 11M) (p=0.259, p=0.425 respectively). However, pre-donation!

BACKGROUND CONTEXT: Previous analysis of acute (8 weeks) perioperative complications in a prospective, multi-center, consecutive ASD cohort demonstrated no differences in major, infectious, wound, neurological or complications requiring surgery for ASD patients receiving BMP vs patients not receiving BMP. PURPOSE: The purpose of this study was to evaluate and compare the complication rates for the same operative cohorts at one year postoperative. STUDY DESIGN/SETTING: Multi-center, prospective, consecutive case/control series. PATIENT SAMPLE: 261 ASD patients consecutively enrolled into a prospective, multicenter database. OUTCOME MEASURES: Complications including: total, major and minor complications, superficial and deep infections, wound seroma/hematoma, neurological, operative, cardiovascular, renal, and gastrointestinal and complications requiring surgery. METHODS: Multicenter, prospective analysis of postoperative complications for consecutive ASD patients receiving BMP (BMP) or no BMP (NOBMP). Inclusion criteria: ASD, age >=18 years, spinal fusion >=4 levels, complete demographic, radiographic, and operative data, and minimum one-year follow up. ASD5scoliosis >=20 degrees, sagittal vertical axis (SVA) >=5 cm, pelvic tilt (PT) >=25 degrees, or thoracic kyphosis (TK) >60 degrees. Total, major, minor and specific complications evaluated. Multivariate adaptive regression splines analysis (MARS) performed. RESULTS: 261 patients, mean follow up 30.3 months (range 12.2-47.9), met inclusion criteria. BMP (n5158; average posterior (PSF) dose 2.5mg/ level, average interbody dose 5 mg/level) and NOBMP (n5 103) had similar preoperative demographic and radiographic values. Mean PSF levels were similar (BMP=12, NOBMP=12.1; p>0.05). BMP had greater operative time, osteotomies/patient, and anteroposterior surgery (p<0.05). Total and minor complications/ patient were greater for BMP vs NOBMP (1.4 vs 0.6, and 0.3 vs 0.9; p<0.05). Major, neurological, wound complications and infections/patient were similar!

BACKGROUND CONTEXT: Incremental cost-utility analysis is critical to the efficient allocation of health care resources, but few cost-utility studies currently exist in the adult spinal deformity (ASD) literature. PURPOSE: Examine the cost-effectiveness of surgical treatment of ASD with extended follow-up on observed costs, payments, and quality-adjusted life-years (QALYs) following index surgery, including any related readmissions. STUDY DESIGN/SETTING: Single-center, retrospective, consecutive case series. PATIENT SAMPLE: 239 consecutive patients undergoing primary surgery for ASD with three-year follow-up data, out of 278 patients eligible for three-year follow-up. OUTCOME MEASURES: Payments (expressed in 2010 dollars) to the hospital were collected from administrative data, with QALYs calculated from the SF-6D. Minimum three-year follow-up was required. METHODS: Payments and QALYs were discounted at 3.5% per year. The study analyzed the average cost-effectiveness ratio (ACER) and a range of incremental cost-effectiveness ratios (ICERs) based on improvement in QALYs from baseline and alternative assumptions of the reduction in health-related quality-of-life (HRQOL) without surgical intervention. Results were projected through 10-year follow-up, and 95% confidence intervals (CIs) were calculated using nonparametric bootstrap methods. RESULTS: Patients were predominantly female (n5203, 85%) with average age of 49 (range 18 to 82). Total discounted per-patient payments averaged >=211,529, including any readmissions over the follow-up period. Discounted QALYs averaged 1.9 over 3-year follow-up. Projecting through 10-year follow-up, the ACER (>=/QALY) was >=37,973 (95% CI; >=35,123 to >=41,066). ICERs ranged from >=58,027 (95% CI; >=53,537 to >=63,271) based on an assumed 20% reduction in quality-of-life per year without surgery to >=357,950 (95% CI; >=276,276 to >=475,997) assuming no reduction in quality-of-life without surgery. CONCLUSIONS: This study considers the cost-effectiveness of surgica!