A cost-effectiveness comparisons of adult spinal deformity surgery in the United States and Japan.

PURPOSE: Information about the cost-effectiveness of surgical procedures for adult spinal deformity (ASD) is critical for providing appropriate treatments for these patients. The purposes of this study were to compare the direct cost and cost-effectiveness of surgery for ASD in the United States (US) and Japan (JP). METHODS: Retrospective analysis of 76 US and 76 JP patients receiving surgery for ASD with ≥2-year follow-up was identified. Data analysis included preoperative and postoperative demographic, radiographic, health-related quality of life (HRQOL), and direct cost for surgery. An incremental cost-effectiveness ratio (ICER) was determined using cost/quality-adjusted life years (QALY). The cost/QALY was calculated from the 2-year cost and HRQOL data. RESULTS: JP exhibited worse baseline spinopelvic alignment than the US (pelvic incidence and lumbar lordosis: 35.4° vs 22.7°, p < 0.01). The US had more three-column osteotomies (50 vs 16%), and shorter hospital stay (7.9 vs 22.7 days) (p < 0.05). The US demonstrated worse postoperative ODI (41.3 vs. 33.9%) and greater revision surgery rate (40 vs 10%) (p < 0.05). Due to the high initial cost and revision frequency, the US had greater total cost ($92,133 vs. $49,647) and cost/QALY ($511,840 vs. $225,668) at 2-year follow-up (p < 0.05). CONCLUSION: Retrospective analysis comparing the direct costs and cost-effectiveness of ASD surgery in the US vs JP demonstrated that the total direct costs and cost/QALY were substantially higher in the US than JP. Variations in patient cohort, healthcare costs, revision frequencies, and HRQOL improvement influenced the cost/QALY differential between these countries.

Analysis of National Rates, Cost, and Sources of Cost Variation in Adult Spinal Deformity.

BACKGROUND: Several studies suggest significant variation in cost for spine surgery, but there has been little research in this area for spinal deformity. OBJECTIVE: To determine the utilization, cost, and factors contributing to cost for spinal deformity surgery. METHODS: The cohort comprised 55 599 adults who underwent spinal deformity fusion in the 2001 to 2013 National Inpatient Sample database. Patient variables included age, gender, insurance, median income of zip code, county population, severity of illness, mortality risk, number of comorbidities, length of stay, elective vs nonelective case. Hospital variables included bed size, wage index, hospital type (rural, urban nonteaching, urban teaching), and geographical region. The outcome was total hospital cost for deformity surgery. Statistics included univariate and multivariate regression analyses. RESULTS: The number of spinal deformity cases increased from 1803 in 2001 (rate: 4.16 per 100 000 adults) to 6728 in 2013 (rate: 13.9 per 100 000). Utilization of interbody fusion devices increased steadily during this time period, while bone morphogenic protein usage peaked in 2010 and declined thereafter. The mean inflation-adjusted case cost rose from $32 671 to $43 433 over the same time period. Multivariate analyses showed the following patient factors were associated with cost: age, race, insurance, severity of illness, length of stay, and elective admission (P < .01). Hospitals in the western United States and those with higher wage indices or smaller bed sizes were significantly more expensive (P < .05). CONCLUSION: The rate of adult spinal deformity surgery and the mean case cost increased from 2001 to 2013, exceeding the rate of inflation. Both patient and hospital factors are important contributors to cost variation for spinal deformity surgery.

Operative Management of Adult Spinal Deformity Results in Significant Increases in QALYs Gained Compared to Nonoperative Management: Analysis of 479 Patients With Minimum 2-Year Follow-Up.

STUDY DESIGN: Retrospective review of prospective multicenter adult spinal deformity (ASD) database. OBJECTIVE: To compare the quality-adjusted life years (QALYs) between operative and nonoperative treatments for ASD patients. SUMMARY OF BACKGROUND DATA: Operative management of ASD repeatedly demonstrates improvements in HRQOL over nonoperative treatment. However, little is reported regarding QALY improvements after surgical correction of ASD. METHODS: Inclusion criteria: ≥18 years, ASD. Health utility values were calculated from SF6D scores and used to calculate QALYs at minimum 2 years from the baseline utility value as well as at 1, 2, and 3 years for the available patients. A 1:1 propensity score matching using six baseline variables was conducted to account for the nonrandom distribution of operative and nonoperative treatments. RESULTS: Four hundred seventy-nine patients were included (OP:258, 70.7%, NONOP:221, 47.1%). One hundred fifty-one (OP:90, NONOP:61) had complete 1, 2, and 3 year data available for QALY trending. Unmatched results are not listed in the abstract. Mean baseline utility scores were statistically similar between the matched groups (OP: 0.609 ±â€Š0.093, NONOP: 0.600 ±â€Š0.091, P = 0.6401) and at 2 year min postop mean OP QALY was greater than NONOP (1.377 ±â€Š0.345 vs. 1.256 ±â€Š0.286, respectively, P < 0.01). For the subanalysis cohort, mean OP QALYs at 1, 2, and 3 years postoperative were all significantly greater than NONOP, P < 0.03 for all (1 yr: 0.651 ±â€Š0.089 vs. 0.61 ±â€Š0.079, 2 yr: 1.29 ±â€Š0.157 vs. 1.189 ±â€Š0.141, and 3 yr: 1.903 ±â€Š0.235 vs. 1.749 ±â€Š0.198, respectively). Matched OP had a larger QALYs gained (from baseline) at 2 year minimum postoperative (0.112 ±â€Š0.243 vs. 0.008 ±â€Š0.195, P < 0.01). For subanalysis of patients with complete 1 to 3 years data, OP had a significantly larger QALYs gained at 1, 2, and 3 years compared with NONOP: 1 year (0.073 ±â€Š0.121 vs. 0.029 ±â€Š0.082, P = 0.0447), 2 years (0.167 ±â€Š0.232 vs. 0.036 ±â€Š0.173, P = 0.0030), and 3years (0.238 ±â€Š0.379 vs. 0.059 ±â€Š0.258, P < 0.01). CONCLUSION: The operative treatment of adult spinal deformity results in significantly greater mean QALYs and QALYs gained at minimum 2 years postop as well as at the 1-, 2-, and 3-year time points compared with nonoperative management. LEVEL OF EVIDENCE: 3.

Comparison of Patient Outcomes in 3725 Overlapping vs 3633 Nonoverlapping Neurosurgical Procedures Using a Single Institution's Clinical and Administrative Database.

Background: Overlapping surgery is a common practice to improve surgical efficiency, but there are limited data on its safety. Objective: To analyze the patient outcomes of overlapping vs nonoverlapping surgeries performed by multiple neurosurgeons. Methods: Retrospective review of 7358 neurosurgical procedures, 2012 to 2015, at an urban academic hospital. Collected variables: patient age, gender, insurance, American Society of Anesthesiologists score, severity of illness, mortality risk, admission type, transfer source, procedure type, surgery date, number of cosurgeons, presence of neurosurgery resident/fellow/another attending, and overlapping vs nonoverlapping surgery. Outcomes: procedure time, length of stay, estimated blood loss, discharge location, 30-day mortality, 30-day readmission, return to operating room, acute respiratory failure, and severe sepsis. Statistics: univariate, then multivariate mixed-effect models. Results: Overlapping surgery patients (n = 3725) were younger and had lower American Society of Anesthesiologists scores, severity of illness, and mortality risk (P < .0001) than nonoverlapping surgery patients (n = 3633). Overlapping surgeries had longer procedure times (214 vs 172 min; P < .0001), but shorter length of stay (7.3 vs 7.9 d; P = .010) and lower estimated blood loss (312 vs 363 mL's; P = .003). Overlapping surgery patients were more likely to be discharged home (73.6% vs 66.2%; P < .0001), and had lower mortality rates (1.3% vs 2.5%; P = .0005) and acute respiratory failure (1.8% vs 2.6%; P = .021). In multivariate models, there was no significant difference between overlapping and nonoverlapping surgeries for any patient outcomes, except for procedure duration, which was longer in overlapping surgery (estimate = 23.03; P < .001). Conclusions: When planned appropriately, overlapping surgery can be performed safely within the infrastructure at our academic institution.

Comparison of Patient Outcomes and Cost of Overlapping Versus Nonoverlapping Spine Surgery.

BACKGROUND: Overlapping surgery recently has gained significant media attention, but there are limited data on its safety and efficacy. To date, there has been no analysis of overlapping surgery in the field of spine. Our goal was to compare overlapping versus nonoverlapping spine surgery patient outcomes and cost. METHODS: A retrospective review was undertaken of 2319 spine surgeries (n = 848 overlapping; 1471 nonoverlapping) performed by 3 neurosurgery attendings from 2012 to 2015 at the University of California San Francisco. Collected variables included patient age, sex, insurance, American Society of Anesthesiology score, severity of illness, risk of mortality, procedure type, surgeon, day of surgery, source of transfer, admission type, overlapping versus nonoverlapping surgery (≥1 minute of overlapping procedure time), Medicare-Severity Diagnosis-Related Group, osteotomy, and presence of another attending/fellow/resident. Univariate, then multivariate mixed-effect models were used to evaluate the effect of the collected variables on the following outcomes: procedure time, estimated blood loss, length of stay, discharge status, 30-day mortality, 30-day unplanned readmission, unplanned return to OR, and total hospital cost. RESULTS: Urgent spine cases were more likely to be done in an overlapping fashion (all P < 0.01). After we adjusted for patient demographics, clinical indicators, and procedure characteristics, overlapping surgeries had longer procedure times (estimate = 26.17; P < 0.001) and lower rates of discharge to home (odds ratio 0.65; P < 0.001), but equivalent rates of 30-day mortality, readmission, return to the operating room, estimated blood loss, length of stay, and total hospital cost (all P = ns). CONCLUSIONS: Overlapping spine surgery may be performed safely at our institution, although continued monitoring of patient outcomes is necessary. Overlapping surgery does not lead to greater hospital costs.

Results of the 2015 Scoliosis Research Society Survey on Single Versus Dual Attending Surgeon Approach for Adult Spinal Deformity Surgery.

STUDY DESIGN: An electronic survey administered to Scoliosis Research Society (SRS) membership. OBJECTIVE: To characterize surgeon practices and views regarding the use of two attending surgeons for adult spinal deformity (ASD) surgery. SUMMARY OF BACKGROUND DATA: The use of two experienced attending surgeons can decrease the operative time, estimated blood loss, and perioperative complication rates. However, the current practice patterns for the use of two attending surgeons remains unknown. METHODS: An electronic, 27-question survey regarding single/dual attending surgeons was administered to the SRS membership. Determinants included: surgeon/practice demographics, assistant type/level of training, and questions regarding use of two attending surgeons. Overall reporting and comparisons between groups were made: US versus international, academic versus private practice, and experience <15 years versus >15 years. RESULTS: A total of 199 surgeons responded from 27 different countries. Overall and between the groups, the respondents significantly reported believing that two attending spine surgeons improves safety, decreases complications, and improves outcomes (P < 0.01). Approximately, 67.3% reported using a second attending ≤25% of the time (33.2% do not), and 24.1% use one ≥51% of the time (similar between groups); 51.1% that have a second attending feel it's limited by reimbursement and access concerns and 71.9% have difficulty getting the second attending reimbursed. 72.3% use a second attending for ALL of the following reasons (no difference between groups): "it's safer/reduces complications," "it decreases operative time," "it decreases blood loss," "it results in improved outcomes," "it's less work and stress for me." If reimbursement was equal/assured for a second attending, 67.5% would use one "more often" or "always." CONCLUSION: The respondents feel that having a second attending surgeon improves patient care, however most do not use one often. Reasons include reimbursement/access concerns and the majority would use one if reimbursement was equal and assured. Based on the current literature and these results, there is a need for working with third party payers to improve dual surgeon reimbursement rates in complex cases. LEVEL OF EVIDENCE: 5.

Sexual function after cervical spine surgery: Independent predictors of functional impairment.

Sexual function (SF) is an important component of patient-focused health related quality of life (HRQoL), but it has not been well studied in spine surgery. This study aims to assess SF after cervical spine surgery and identify predictors of SF. This single-center retrospective study evaluates SF of adults who underwent cervical spine surgery 2007-2012. Predictor variables included demographics, medical/surgical history, operative information, HRQoL measures (Neck Disability Index, SF-12), validated SF surveys [Female Sexual Function Index (FSFI) and Brief Sexual Function Inventory (BSFI) for males], and a study-specific SF questionnaire. 59 patients (31M, 28F; mean age=56±8.4) had significantly lower SF scores compared to age-matched peers: average BSFI = 2.26±1.22 (vs. 06±0.74), average FSFI=13.05±11.42 (<26.55 indicating sexual dysfunction). In men, lower mental SF-12 and higher NDI, back pain, and number of operated levels were associated with lower BSFI scores (all p<0.05). In women, higher total number of medications and pain medications were associated with lower FSFI scores (both p<0.05). 46% of patients reported difficulty performing a sexual position after surgery that they had previously enjoyed. 39% of men had difficulty on top during intercourse, and 32% of participants reported difficulty performing oral sex. 39% of patients reported worse SF, while only 5% reported an improvement in postoperative SF. Men and women who underwent cervical spine surgery had lower SF scores than age-matched peers, likely attributable to general mental health, regional neck disability, back pain, and medications. A large portion of patients reported subjectively worsened SF after surgery.

Initial Experience With Real-Time Continuous Physical Activity Monitoring in Patients Undergoing Spine Surgery.

STUDY DESIGN: Multicenter prospective pilot study. OBJECTIVE: To evaluate if continuous physical activity monitoring by a personal electronic 3-dimensional accelerometer device is feasible and can provide objective data that correlates with patient-reported outcomes following spine surgery. SUMMARY OF BACKGROUND DATA: Self-reported health-related quality-of-life (HRQOL) metrics are inherently limited by being very subjective, having a low frequency of data collection, and inconsistent follow-up. METHODS: Inclusion criteria: adults (18+), thoracolumbar deformity or degenerative disease, and regular access to a computer with internet connection. Physical activity parameters included: number of daily steps, maximum hourly steps, and activity intensity. Patients completed the Oswestry Disability Index (ODI), the Short-Form Health Survey 36 (SF-36), and the Scoliosis Research Society-22r (SRS22) preoperatively and postoperatively at 6 weeks, 3 months, and 6 months. RESULTS: Thirty-two patients were enrolled, 8 (25%) withdrew, 1 (3.1%) died, and 1 (3.1%) did not end up undergoing surgery resulting in 22 (68.8%) available patients. Mean preoperative and postoperative step ranges were 1278±767 to 17,800±6464 and 891±587 to 12,655±7038, respectively. Eleven patients improved in mean total daily steps at the final postoperative month with 2 having significant improvements (P<0.05). Five patients did not significantly change (P>0.05) and 6 patients had significantly lower mean total daily steps at 6 months (P<0.05). The entire cohort significantly improved in ODI, SF-36 Physical Component Summary, SRS Activity, SRS Appearance, SRS Mental, SRS Satisfaction, and SRS Total score at 6 months postoperative (P<0.05 for all). Both ODI and Physical Component Summary were significantly correlated with preoperative average total daily steps (r=-0.61, P=0.0058 and r=0.60, P=0.0114, respectively). No other HRQOL metrics were significantly correlated at baseline or at 6 months postoperative (P>0.05). CONCLUSIONS: A prospective pilot study for continuous real-time physical activity monitoring was successfully completed. This is the first study of its kind and demonstrates a foundation to continuous physical activity monitoring following spine surgery. A larger and longer prospective study is needed to confirm long-term results and its relationship with HRQOL scores.

Comparison of Structural Disease Burden to Health-related Quality of Life Scores in 264 Adult Spinal Deformity Patients With 2-Year Follow-up: Novel Insights into Drivers of Disability.

STUDY DESIGN: This is a review of a prospective multicenter database. OBJECTIVE: To investigate the relationship between preoperative disability and sagittal deformity in patients with high Oswestry Disability Index (ODI) and no sagittal malalignment, or low ODI and high sagittal malalignment. SUMMARY OF BACKGROUND DATA: The relationship between ODI and sagittal malalignment varies between each adult spinal deformity (ASD) patient. METHODS: A prospective multicenter database of 365 patients with ASD undergoing surgical reconstruction was analyzed. Inclusion criteria entailed: age 18 years or above and the presence of spinal deformity as defined by a coronal Cobb angle≥20 degrees, sagittal vertical axis (SVA)≥5 cm, pelvic tilt (PT) angle≥25 degrees, or thoracic kyphosis≥60 degrees. Radiographic and health-related quality of life (HRQOL) variables were examined and compared, preoperatively and at 2-year postoperative follow-up. Group 1 (low disability high sagittal-LDHS) consisted of ODI<40 and SVA≥5 cm or PT≥25 degrees or pelvic incidence-lumbar lordosis≥11 degrees and group 2 (high disability low sagittal-HDLS) consisted of ODI>40 and SVA<5 cm and PT<25 degrees and pelvic incidence-lumbar lordosis<11 degrees. RESULTS: Of 264 patients with follow-up, 58 (22.0%) patients were included in LDHS and 30 (11.4%) were included in HDLS. Both groups had similar demographics and preoperative coronal angles. HDLS had worse baseline HRQOL for all measures (P<0.05) except leg and back pain. HDLS had a higher rate of self-reported leg weakness, arthritis, depression and neurological disorder. Both groups had similar 2-year improvements in HRQOL (P>0.05), except only HDLS had a significant Scoliosis Research Society Mental improvement and a significantly higher rate of reaching minimal clinically important differences in Scoliosis Research Society Mental scores (P<0.05). CONCLUSIONS: There is an association of worse baseline HRQOL measures, weakness, arthritis, and mental disease in HDLS. Furthermore, HDLS patients demonstrated similar improvements to LDHS. However, HDLS had greater improvements in the mental domains, perhaps indicating the responsiveness of the mental disability to surgical treatment. LEVEL OF EVIDENCE: Level III.

Impact of poor mental health in adult spinal deformity patients with poor physical function: a retrospective analysis with a 2-year follow-up.

OBJECTIVE Mental disease burden can have a significant impact on levels of disability and health-related quality of life (HRQOL) measures. Therefore, the authors investigated the significance of mental health status in adults with spinal deformity and poor physical function. METHODS A retrospective analysis of a prospective multicenter database of 365 adult spinal deformity (ASD) patients who had undergone surgical treatment was performed. Health-related QOL variables were examined preoperatively and at the 2-year postoperative follow-up. Patients were grouped by their 36-Item Short Form Health Survey mental component summary (MCS) and physical component summary (PCS) scores. Both groups had PCS scores ≤ 25th percentile for matched norms; however, the low mental health (LMH) group consisted of patients with an MCS score ≤ 25th percentile, and the high mental health (HMH) group included patients with an MCS score ≥ 75th percentile. RESULTS Of the 264 patients (72.3%) with a 2-year follow-up, 104 (28.5%) met the inclusion criteria for LMH and 40 patients (11.0%) met those for HMH. The LMH group had a significantly higher overall rate of comorbidities, specifically leg weakness, depression, hypertension, and self-reported neurological and psychiatric disease processes, and were more likely to be unemployed as compared with the HMH group (p < 0.05 for all). The 2 groups had similar 2-year postoperative improvements in HRQOL (p > 0.05) except for the greater improvements in the MCS and the Scoliosis Research Society-22r questionnaire (SRS-22r) mental domain (p < 0.05) in the LMH group and greater improvements in PCS and SRS-22r satisfaction and back pain domains (p < 0.05) in the HMH group. The LMH group had a higher rate of reaching a minimal clinically important difference (MCID) on the SRS-22r mental domain (p < 0.01), and the HMH group had a higher rate of reaching an MCID on the PCS and SRS-22r activity domain (p < 0.05). On multivariable logistic regression, having LMH was a significant independent predictor of failure to reach an MCID on the PCS (p < 0.05). At the 2-year postoperative follow-up, 14 LMH patients (15.1%) were categorized as HMH. Two LMH patients (2.2%), and 3 HMH patients (7.7%) transitioned to a PCS score ≥ 75th percentile for age- and sex-matched US norms (p < 0.01). CONCLUSIONS While patients with poor mental and physical health, according to their MCS and PCS scores, have higher medical comorbidity and unemployment rates, they still demonstrate significant improvements in HRQOL measurements postoperatively. Both LMH and HMH patient groups demonstrated similar improvements in most HRQOL domains, except that the LMH patients had difficulties in obtaining improvements in the PCS domain.

Importance of patient-reported individualized goals when assessing outcomes for adult spinal deformity (ASD): initial experience with a Patient Generated Index (PGI).

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.

Results of the AANS membership survey of adult spinal deformity knowledge: impact of training, practice experience, and assessment of potential areas for improved education: Clinical article.

OBJECT: Adult spinal deformity (ASD) surgery is increasing in the spinal neurosurgeon's practice. METHODS: A survey of neurosurgeon AANS membership assessed the deformity knowledge base and impact of current training, education, and practice experience to identify opportunities for improved education. Eleven questions developed and agreed upon by experienced spinal deformity surgeons tested ASD knowledge and were subgrouped into 5 categories: (1) radiology/spinopelvic alignment, (2) health-related quality of life, (3) surgical indications, (4) operative technique, and (5) clinical evaluation. Chi-square analysis was used to compare differences based on participant demographic characteristics (years of practice, spinal surgery fellowship training, percentage of practice comprising spinal surgery). RESULTS: Responses were received from 1456 neurosurgeons. Of these respondents, 57% had practiced less than 10 years, 20% had completed a spine fellowship, and 32% devoted more than 75% of their practice to spine. The overall correct answer percentage was 42%. Radiology/spinal pelvic alignment questions had the lowest percentage of correct answers (38%), while clinical evaluation and surgical indications questions had the highest percentage (44%). More than 10 years in practice, completion of a spine fellowship, and more than 75% spine practice were associated with greater overall percentage correct (p < 0.001). More than 10 years in practice was significantly associated with increased percentage of correct answers in 4 of 5 categories. Spine fellowship and more than 75% spine practice were significantly associated with increased percentage correct in all categories. Interestingly, the highest error was seen in risk for postoperative coronal imbalance, with a very low rate of correct responses (15%) and not significantly improved with fellowship (18%, p = 0.08). CONCLUSIONS: The results of this survey suggest that ASD knowledge could be improved in neurosurgery. Knowledge may be augmented with neurosurgical experience, spinal surgery fellowships, and spinal specialization. Neurosurgical education should particularly focus on radiology/spinal pelvic alignment, especially pelvic obliquity and coronal imbalance and operative techniques for ASD.