Faculty Bibliography

OBJECTIVE Patients with adult spinal deformity (ASD) experience significant quality of life improvements after surgery. Treatment, however, is expensive and complication rates are high. Predictive analytics has the potential to use many variables to make accurate predictions in large data sets. A validated minimum clinically important difference (MCID) model has the potential to assist in patient selection, thereby improving outcomes and, potentially, cost-effectiveness. METHODS The present study was a retrospective analysis of a multiinstitutional database of patients with ASD. Inclusion criteria were as follows: age ≥ 18 years, radiographic evidence of ASD, 2-year follow-up, and preoperative Oswestry Disability Index (ODI) > 15. Forty-six variables were used for model training: demographic data, radiographic parameters, surgical variables, and results on the health-related quality of life questionnaire. Patients were grouped as reaching a 2-year ODI MCID (+MCID) or not (-MCID). An ensemble of 5 different bootstrapped decision trees was constructed using the C5.0 algorithm. Internal validation was performed via 70:30 data split for training/testing. Model accuracy and area under the curve (AUC) were calculated. The mean quality-adjusted life years (QALYs) and QALYs gained at 2 years were calculated and discounted at 3.5% per year. The QALYs were compared between patients in the +MCID and -MCID groups. RESULTS A total of 234 patients met inclusion criteria (+MCID 129, -MCID 105). Sixty-nine patients (29.5%) were included for model testing. Predicted versus actual results were 50 versus 40 for +MCID and 19 versus 29 for -MCID (i.e., 10 patients were misclassified). Model accuracy was 85.5%, with 0.96 AUC. Predicted results showed that patients in the +MCID group had significantly greater 2-year mean QALYs (p = 0.0057) and QALYs gained (p = 0.0002). CONCLUSIONS A successful model with 85.5% accuracy and 0.96 AUC was constructed to predict which patients would reach ODI MCID. The patients in the +MCID group had significantly higher mean 2-year QALYs and QALYs gained. This study provides proof of concept for using predictive modeling techniques to optimize patient selection in complex spine surgery.

MINI: Despite differences in sagittal malalignment, antero-posterior pelvic translation maintained the position of T9 in line with the ankles, independently of sagittal vertical axis. Pelvic tilt was directly predicted by lower limb compensatory mechanisms. Therefore, these adaptation mechanisms being included in pelvic tilt analysis, it does not need additional consideration in the surgical planning. STUDY DESIGN: Retrospective review. OBJECTIVE: To investigate the role of lower limbs compensation with progressive sagittal malalignment. SUMMARY OF BACKGROUND DATA: Although lower limb compensatory mechanisms are established response to progressive sagittal malalignment, their specific role and potential impact on surgical planning has not been evaluated. METHODS: Single center retrospective review of full body x-rays was performed in patients of age >20 years. Parameters were measured with dedicated software. Population was stratified by 50 mm intervals of sagittal vertical axis (SVA) and one-way ANOVA was performed to compare P.shift (P.shift = anteroposterior translation of the pelvis vs. the feet) across SVA groups. Anteroposterior offset of each vertebra in relation to a vertical line extended from the distal tibial metaphysis (TM) was investigated. Linear regression was performed to predict pelvic tilt (PT) using Knee angle (KA) and P.shift, whereas controlling for pelvic incidence minus lumbar lordosis mismatch (PI-LL) and SVA. RESULTS: A total of 2124 patient visits were included (PI = 55.1 +/- 14.1 degrees , PT=21.0 +/- 11 degrees , PI-LL=6.3 +/- 17.3 degrees , SVA = 29 +/- 51 mm). With progressively increased SVA, P.shift decreased from 30 to -100 mm (all P < 0.005). Analysis of vertebral offset from the distal tibial metaphysis revealed that T9 was aligned with the TM line across all SVA groups. Prediction of PT based on PI-LL and SVA yielded R=0.76 (P < 0.001). Subsequent addition of KA and P.shift as independent parameters using hierarchical multiple regression led to significant improvement in R, demonstrating the independent role of lower limbs parameters in PT prediction. KA and P.shift had a positive standardized coefficient (all P < 0.05). CONCLUSION: Lower limb compensatory mechanisms increase with progressive sagittal malalignment. Anteroposterior translation of pelvis allows the T9 vertebra to remain in line with the ankle ("conus of economy"). Lower limb compensatory mechanisms are positive predictors of PT and thus do not require additional consideration in surgical realignment planning. LEVEL OF EVIDENCE: 3.

STUDY DESIGN: Observational database review. OBJECTIVE: To determine the effect of patient severity of illness (SOI) on the cost of spine surgery among New York state hospitals. SUMMARY OF BACKGROUND DATA: National health care spending has risen at an unsustainable rate with musculoskeletal care, and spine surgery in particular, accounting for a significant portion of this expenditure. In an effort towards cost-containment, health care payers are exploring novel payment models some of which reward cost savings but penalize excessive spending. To mitigate risk to health care institutions, accurate cost forecasting is essential. No studies have evaluated the effect of SOI on costs within spine surgery. MATERIALS AND METHODS: The New York State Hospital Inpatient Cost Transparency Database was reviewed to determine the costs of 69,831 hospital discharges between 2009 and 2011 comprising the 3 most commonly performed spine surgeries in the state. These costs were then analyzed in the context of the specific all patient refined diagnosis-related group (DRG) SOI modifier to determine this index's effect on overall costs. RESULTS: Overall, hospital-reported cost increases with the patient's SOI class and patients with worse baseline health incur greater hospital costs (P<0.001). Moreover, these costs are increasingly variable for each worsening SOI class (P<0.001). This trend of increasing costs is persistent for all 3 DRGs across all 3 years studied (2009-2011), within each of the 7 New York state regions, and occurs irrespective of the hospital's teaching status or size. CONCLUSIONS: Using the 3M all patient refined-DRG SOI index as a measure of patient's health status, a significant increase in cost for spine surgery for patients with higher SOI index was found. This study confirms the greater cost and variability of spine surgery for sicker patients and illustrates the inherent unpredictability in cost forecasting and budgeting for these same patients.

OBJECTIVE Using 2 complication-reporting methods, the authors investigated the incidence of major medical complications and mortality in elderly patients after surgery for adult spinal deformity (ASD) during a 2-year follow-up period. METHODS The authors queried a multicenter, prospective, surgeon-maintained database (SMD) to identify patients 65 years or older who underwent surgical correction of ASD from 2008 through 2014 and had a minimum 2 years of follow-up (n = 153). They also queried a Centers for Medicare & Medicaid Services claims database (MCD) for patients 65 years or older who underwent fusion of 8 or more vertebral levels from 2005 through 2012 (n = 3366). They calculated cumulative rates of the following complications during the first 6 weeks after surgery: cerebrovascular accident, congestive heart failure, deep venous thrombosis, myocardial infarction, pneumonia, and pulmonary embolism. Significance was set at p < 0.05. RESULTS During the perioperative period, rates of major medical complications were 5.9% for pneumonia, 4.1% for deep venous thrombosis, 3.2% for pulmonary embolism, 2.1% for cerebrovascular accident, 1.8% for myocardial infarction, and 1.0% for congestive heart failure. Mortality rates were 0.9% at 6 weeks and 1.8% at 2 years. When comparing the SMD with the MCD, there were no significant differences in the perioperative rates of major medical complications except pneumonia. Furthermore, there were no significant intergroup differences in the mortality rates at 6 weeks or 2 years. The SMD provided greater detail with respect to deformity characteristics and surgical variables than the MCD. CONCLUSIONS The incidence of most major medical complications in the elderly after surgery for ASD was similar between the SMD and the MCD and ranged from 1% for congestive heart failure to 5.9% for pneumonia. These complications data can be valuable for preoperative patient counseling and informed consent.

BACKGROUND CONTEXT: Patients with degenerative lumbar stenosis (DLS) adopt a forward flexed posture in an attempt to decompress neural elements. The relationship between sagittal alignment and severity of lumbar stenosis has not previously been studied. PURPOSE: We hypothesized that patients with increasing radiological severity of lumbar stenosis will exhibit worsening sagittal alignment. STUDY DESIGN: This is a cross-sectional study. PATIENT SAMPLE: Our sample consists of patients who have DLS. OUTCOME MEASURES: Standing pelvic, regional, lower extremity and global sagittal alignment, and health-related quality of life (HRQoL) were the outcome measures. METHODS: Patients with DLS were identified from a retrospective clinical database with corresponding full-body stereoradiographs. Exclusion criteria included coronal malalignment, prior spine surgery, spondylolisthesis>Grade 1, non-degenerative spinal pathology, or skeletal immaturity. Central stenosis severity was graded on axial T2-weighted magnetic resonance imaging (MRI) from L1-S1. Foraminal stenosis and supine lordosis was graded on sagittal T1-weighted images. Standing pelvic, regional, lower extremity, and global sagittal alignment were measured using validated software. The HRQoL measures were also analyzed in relation to severity of stenosis. RESULTS: A total of 125 patients were identified with DLS on appropriate imaging. As central stenosis grade increased, patients displayed significantly increasing standing T1 pelvic angle, pelvic tilt, sagittal vertical axis, and pelvic incidence-lumbar lordosis (p<.05). No significant difference wasfound in pelvic incidence, supine lordosis, thoracic kyphosis, or T1 spinopelvic inclination between central stenosis groups. Despite similar supine lordosis between stenosis groups, patients with Grades 2 and 3 stenosis had less standing lordosis, suggesting antalgic posturing. Upper lumbar (L1-L3) stenosis predicted worse alignment than lower lumbar (L4-S1) stenosis. Increasing severity of foraminal stenosis was associated with reduced lumbar lordosis; however, no significant postural difference in lordosis, thoracolumbar, or lower extremity compensatory mechanisms were noted between foraminal stenosis groups. Stenosis grading did not predict worsening HRQoLs in central or foraminal stenosis. CONCLUSIONS: Severity of central lumbar stenosis as graded on MRI correlates with severity of sagittal malalignment. These findings support theories of sagittal malalignment as a compensatory mechanism for central lumbar stenosis.

STUDY DESIGN: Retrospective review of a prospective multicenter database. OBJECTIVE: To develop a method to analyze sagittal alignment, free of PJK's influence, and then compare PJK to non-PJK patients using this method. SUMMARY OF BACKGROUND DATA: Proximal Junctional Kyphosis (PJK) following Adult Spinal Deformity (ASD) surgery remains problematic as it alters sagittal alignment. This study proposes a novel virtual modeling technique that attempts to eliminate the confounding effects of PJK on postoperative spinal alignment. METHODS: A virtual spinal modeling technique was developed on a retrospective ASD cohort of patients with multilevel spinal fusions to the pelvis with at least 2 year post-operative follow-up. The virtual post-op alignment (VIRTUAL) was created from the post-op alignment of the instrumented segments and the pre-op alignment of the unfused segments. VIRTUAL was validated by comparisons to actual 2-year post-op alignment (REAL) in NOPJK patients. Patients were then divided into two groups: PJK and NOPJK based on the presence/absence of PJK at 2 years post-op. PJK and NOPJK patients were compared using VIRTUAL and REAL. RESULTS: 458 patients (78F, mean 57.9y) were analyzed. The validation of VIRTUAL versus REAL demonstrated correlation coefficients above 0.7 for all measures except SVA (r = 0.604). At 2-years, REAL alignment in PJK patients demonstrated a smaller PI-LL and a larger thoracic kyphosis than NOPJK patients, but similar SVA, TPA, and PT. An analysis of VIRTUAL demonstrated that PJK patients had a smaller PI-LL, PT, SVA, and TPA than NOPJK patients (p < 0.05). CONCLUSION: This technique demonstrated strong correlations with actual postoperative alignment. Comparisons between REAL and VIRTUAL alignments revealed that postoperative PJK may develop partially as a compensatory mechanism to the over-correction of sagittal deformities. Future research will evaluate the appropriate thresholds for deformity correction according to age and ASD severity. LEVEL OF EVIDENCE: 3.

BACKGROUND: Although cervical spondylotic myelopathy (CSM) can be devastating, its relative impact on general health remains unclear. Patient responses to the SF-36 PCS/MCS were compared between CSM and other diseases to evaluate their respective impacts on quality of life. OBJECTIVE: Compare SF-36 PCS/MCS scores in CSM to population and disease-specific norms. METHODS: Retrospective analysis of a prospective, multi-center AOSpine North American CSM Study database. Inclusion criteria were symptomatic disease, age>18, cord compression on MRI or CT myelography, and baseline SF-36 values. SF-36 PCS/MCS in CSM were compared to national normative values and disease-specific norms using student's t-test. ANOVA was used to assess differences across age groups and offsets from age-matched controls. Threshold for significance was p<0.05. RESULTS: 285 patients met inclusion criteria. Mean age was 56.6+12.0 years with male predominance (60%). SF-36 scores revealed significant baseline disability (PCS 34.5+9.8; MCS 41.5+/- 14.4). While there were no differences across age groups, when compared to age-matched normative data, younger patients had a larger PCS offset than older patients. CSM caused worse physical disability than most diseases except heart failure. Only back pain/sciatica induced worse mental disability. CONCLUSION: CSM affects quality of life to an extent greater than diabetes or cancer. Although mean impact of CSM does not vary with age, younger patients suffer from greater differences in baseline function. This study highlights the impact of myelopathy on patient function, particularly among younger age groups, and suggests that CSM merits similar caliber of healthy policy attention as more well-studied diseases.

BACKGROUND CONTEXT: Current metrics to assess patients' health-related quality of life (HRQOL) may not reflect a true change in the patients' specific perception of what is most important to them. PURPOSE: This study aimed to describe the initial experience of a Patient Generated Index (PGI) in which patients create their own outcome domains. STUDY DESIGN: This is a single-center prospective study. PATIENT SAMPLE: Patients with adult spinal deformity (ASD) comprise the study sample. OUTCOME MEASURES: Oswestry Disability Index (ODI), Short Form-36 (SF-36 Physical Component Score [PCS] and Mental Component Score [MCS]), Scoliosis Research Society-22r (SRS-22r), and PGI. METHODS: Oswestry Disability Index, SF-36, SRS-22r, and PGI were administered preoperatively and postoperatively at 6 weeks, 3 months, 6 months, and 1 and 2 years. PGI correlations with ODI, SF-36, SRS total score, free-text frequency analysis of PGI exact response with text in ODI and SRS-22r questionnaires, and the responsiveness (effect size [ES]) of the HRQOL metrics were analyzed. No funding was used for this study and there are no conflicts of interest. RESULTS: A total of 59 patients with 209 clinical encounters produced 370 PGI written response topics that included affect or emotions, relationships, activities of daily life, personal care, work, and hobbies. Mean preoperative PGI score was 18.6+/-13.5 (0-71.7 out of 100 [best]), and mean scores significantly improved at every postoperative time point (p<.05). Preoperative PGI scores significantly correlated with preoperative ODI (r=-0.28, p=.03), MCS (r=0.48, p<.01), and SRS total (r=0.57, p<.01). Postoperative PGI scores correlated with all HRQOL measures (p<.0001): ODI (r=-0.65), PCS (r=0.50), MCS (r=0.55), and SRS total (r=0.63). PGI responses exactly matched ODI and SRS-22r text at 47.8% and 35.4%, respectively, and at 63.2% and 58.9%, respectively, for categories. Patient Generated Index ES at a minimum of 1-year follow-up was -2.39, indicating substantial responsiveness (|ES|>0.8). Effect sizes for ODI, SRS-22r total, SF-36 PCS, and SF-36 MCS were 2.16, -2.06, -2.05, and -0.80, respectively. CONCLUSIONS: The PGI is easy to administer and offers additional information about the patients' perspective not captured in standard HRQOL metrics. Patient Generated Index scores correlated with all of the standard HRQOL scores and were more responsive than ODI, SF-36, and SRS-22r, suggesting that the PGI may be a step closer to one HRQOL measure that better encompasses concerns and goals of the individual patients.

OBJECTIVE Although 3-column osteotomy (3CO) can provide powerful alignment correction in adult spinal deformity (ASD), these procedures are complex and associated with high complication rates. The authors' objective was to assess complications associated with ASD surgery that included 3CO based on a prospectively collected multicenter database. METHODS This study is a retrospective review of a prospectively collected multicenter consecutive case registry. ASD patients treated with 3CO and eligible for 2-year follow-up were identified from a prospectively collected multicenter ASD database. Early ( 6 weeks after surgery) complications were collected using standardized forms and on-site coordinators. RESULTS Of 106 ASD patients treated with 3CO, 82 (77%; 68 treated with pedicle subtraction osteotomy [PSO] and 14 treated with vertebral column resection [VCR]) had 2-year follow-up (76% women, mean age 60.7 years, previous spine fusion in 80%). The mean number of posterior fusion levels was 12.9, and 17% also had an anterior fusion. A total of 76 early (44 minor, 32 major) and 66 delayed (13 minor, 53 major) complications were reported, with 41 patients (50.0%) and 45 patients (54.9%) affected, respectively. Overall, 64 patients (78.0%) had at least 1 complication, and 50 (61.0%) had at least 1 major complication. The most common complications were rod breakage (31.7%), dural tear (20.7%), radiculopathy (9.8%), motor deficit (9.8%), proximal junctional kyphosis (PJK, 9.8%), pleural effusion (8.5%), and deep wound infection (7.3%). Compared with patients who did not experience early or delayed complications, those who had these complications did not differ significantly with regard to age, sex, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists score, smoking status, history of previous spine surgery or spine fusion, or whether the 3CO performed was a PSO or VCR (p >/= 0.06). Twenty-seven (33%) patients had 1-11 reoperations (total of 44 reoperations). The most common indications for reoperation were rod breakage (n = 14), deep wound infection (n = 15), and PJK (n = 6). The 24 patients who did not achieve 2-year follow-up had a mean of 0.85 years of follow-up, and the types of early and delayed complications encountered in these 24 patients were comparable to those encountered in the patients that achieved 2-year follow-up. CONCLUSIONS Among 82 ASD patients treated with 3CO, 64 (78.0%) had at least 1 early or delayed complication (57 minor, 85 major). The most common complications were instrumentation failure, dural tear, new neurological deficit, PJK, pleural effusion, and deep wound infection. None of the assessed demographic or surgical parameters were significantly associated with the occurrence of complications. These data may prove useful for surgical planning, patient counseling, and efforts to improve the safety and cost-effectiveness of these procedures.

STUDY DESIGN: Retrospective study OBJECTIVE:: To propose radiographic characteristics of patients with cervical disability and to investigate the relevant parameters when assessing cervical alignment. SUMMARY OF BACKGROUND DATA: Although cervical kyphosis is traditionally recognized as presentation of cervical deformity, an increasing number of studies demonstrated that cervical kyphosis may not equal cervical deformity. Therefore, several other differentiating criteria for cervical deformity should be investigated and supported with quality of life scores. METHODS: A database of full-body radiographs was retrospectively reviewed. Patients without previous cervical surgery, with a well aligned thoracolumbar profile (defined as T1 pelvis angle (TPA) <15 degrees ) and with an available Neck Disability Index (NDI) score were reviewed in this study. Subjects were stratified into an asymptomatic (64 subjects with NDI15, VAS neck>3, or VAS arm>3). Independent t-tests were performed to investigate differences between two groups. Logistic regressions and principle component analyses were then performed. RESULTS: NDI averaged 5.43 in asymptomatic group, significantly smaller than symptomatic group (5.43 vs. 41.25). T-test revealed that C2-C7 SVA, McGregor slope (McGS) and the slope of line of sight (SLS were significantly different while C2C7 angle (Cervical curvature, CC) did not show statistical difference (P = 0.09). Logistic regressions were performed using the significantly different parameters as well as CC. Results identified C2-C7 SVA and SLS as independent risk factors for low HRQoL. The principle component analysis, lead to a new factor (0.55 x C2C7 SVA + 0.34 x C0C2 + 0.77 x CC) with strong correlations with NDI, VAS and EQ5D measurements. CONCLUSION: The traditional concept of cervical kyphosis should not be regarded as a standalone criterion of cervical deformity. The most clinically relevant components of cervical analysis are the C2-C7 SVA, C0C2 angle and C2C7 angle. In addition, the three components should be assessed in together in harmony and not individually. LEVEL OF EVIDENCE: 4.