Adult Spinal Deformity Correction Research Articles

The Intradiscal Osteotomy: An Alternative Technique for Adult Spinal Deformity Correction.

Adult spinal deformity (ASD) correction has changed considerably since the initial description of a Smith-Petersen osteotomy (SPO), including pedicle subtraction osteotomies (PSO), and more minimally invasive techniques. Here, we introduce and describe the intradiscal osteotomy (IDO), a novel variation of Schwab type 3 and 4 osteotomies allowing pedicle and vertebral body preservation, and its advantages and disadvantages.After pedicle screw placement, the posterior elements (except pedicles) are removed from the appropriate vertebrae, including the superior/inferior articulating processes, laminae, and spinous processes. An osteotome is used to remove the posterior aspect of the superior and inferior endplate, followed by the entire disc, creating more working room for eventual cage insertion. After the careful release of the annulus, an intradiscal distractor is used to distract the endplates and allow interbody cage insertion as anteriorly as possible. Pedicle and vertebral body preservation allow increased fixation and endplate cage support, which lengthens the anterior column and acts as a fulcrum when compressing posteriorly to restore lordosis. By allowing for anterior and posterior column release, the IDO technique provides a feasible, all-posterior approach for the correction of fixed or flexible kyphoscoliotic curves.This technical report introduces and describes the IDO as an alternative method for thoracic and/or lumbar ASD correction. More studies are required to fully elucidate its outcome vs. complication profile compared to other deformity correction techniques.

Multiple-Rod Constructs Do Not Reduce Pseudarthrosis and Rod Fracture After Pedicle Subtraction Osteotomy for Adult Spinal Deformity Correction but Improve Quality of Life.

ObjectiveTo compare the radiological and functional outcomes and complications of adult spinal deformity patients who underwent a pedicle subtraction osteotomy (PSO) below L2 but categorized according to their construct where either 2-rod or multiple-rod construct is applied. MethodsSixty-seven patients met the inclusion criteria, and were categorized into 3 groups: 2 rods (2R), multiple rods around the PSO (MRP), multiple rods around the PSO and lumbosacral junction (MRL). Demographic data, operative parameters, spinopelvic parameters, functional outcomes, and complications were collected. ResultsHealth-related quality of life scores showed a better outcome at 6 months and last follow-up visits in the MRP and MRL groups which were noted on different domains of Scoliosis Research Society-22 questionnaire, 36-item Short Form Health Surve, and Oswestry Disability Index scores (p<0.05). The 3 groups showed similar rates of rod-related complications with no significant difference (p=0.95). And inside each group, distribution of complications between pseudarthrosis with revision and rod fracture without revision was also similar (p=0.99). ConclusionThe use of multiple rods across the PSO did not show a better outcome when compared to single rods in terms of incidence and types of mechanical complications. However, better postoperative coronal alignment and health-related quality of life scores in the multiple rods group could be seen demonstrating an improved functional outcome.

Patient and Spine Surgeon Perceptions on Shared Decision-Making in the Treatment of Older Adults Undergoing Corrective Surgery for Adult Spinal Deformity.

Retrospective. To understand patients' and spine surgeons' perspectives about decision-making around surgery for adult spinal deformity. Surgery for correction of adult spinal deformity is often beneficial; however, in over 20% of older adults (≥ 65 yrs of age), outcomes from surgery are less desirable. We conducted semistructured, in-depth interviews with six patients and five spine surgeons. Two investigators independently coded the transcripts using constant comparative method, as well as an integrative, team-based approach to identify themes. Patients themes: 1) patients felt surgery was their only choice because they were running out of time to undergo invasive procedures; 2) patients mentally committed to surgery prior to the initial encounter with their surgeon and contextualized the desired benefits while minimizing the potential risks; 3) patients felt that the current decision support tools were ineffective in preparing them for surgery; and 4) patients felt that pain management was the most difficult part of recovery from surgery. Surgeons themes: 1) surgeons varied substantially in their interpretations of shared decision-making; 2) surgeons did not consider patients' chronological age as a major contraindication to undergoing surgery; 3) there is a goal mismatch between patients and surgeons in the desired outcomes from surgery, where patients prioritize complete pain relief whereas surgeons prioritize concrete functional improvement; and 4) surgeons felt that patient expectations from surgery were often established prior to their initial surgery visit, and frequently required recalibration. Older adult patients viewed the decision to have surgery as time-sensitive, whereas spine surgeons expressed the need for recalibrating patient expectations and balancing the risks and benefits when considering surgery. These findings highlight the need for improved understanding of both sides of shared decision-making which should involve the needs and priorities of older adults to help convey patient-specific risks and choice awareness. 3.

Efficacy and radiographic analysis of oblique lumbar interbody fusion in treating adult spinal deformity.

Adult spinal deformity (ASD) is usually rigid and requires a combined anterior–posterior approach for deformity correction. Anterior lumbar interbody fusion (ALIF) allows direct access to the disc space and placement of a large interbody graft. A larger interbody graft facilitates correction of ASD. However, an anterior approach carries significant risks. Lateral lumbar interbody fusion (LLIF) through a minimally invasive approach has recently been used for ASD. The present study was performed to evaluate the effectiveness of oblique lumbar interbody fusion (OLIF) in the treatment of ASD. We performed a retrospective study utilizing the data of 74 patients with ASD. The inclusion criteria were lumbar coronal Cobb angle > 20°, pelvic incidence (PI)–lumbar lordosis (LL) mismatch > 10°, and minimum follow–up of 2 years. Patients were divided into two groups: ALIF combined with posterior spinal fixation (ALIF+PSF) (n = 38) and OLIF combined with posterior spinal fixation (OLIF+PSF) (n = 36). The perioperative spinal deformity radiographic parameters, complications, and health-related quality of life (HRQoL) outcomes were assessed and compared between the two groups. The preoperative sagittal vertical axis (SVA), LL, PI–LL mismatch, and lumbar Cobb angles were similar between the two groups. Patients in the OLIF+PSF group had a slightly higher mean number of interbody fusion levels than those in the ALIF+PSF group. At the final follow–up, all radiographic parameters and HRQoL scores were similar between the two groups. However, the rates of perioperative complications were higher in the ALIF+PSF than OLIF+PSF group. The ALIF+PSF and OLIF+PSF groups showed similar radiographic and HRQoL outcomes. These observations suggest that OLIF is a safe and reliable surgical treatment option for ASD.

Upper instrumented vertebra\u2013femoral angle and correlation with proximal junctional kyphosis in adult spinal deformity

IntroductionAlthough matching lumbar lordosis (LL) with pelvic incidence (PI) is an important surgical goal for adult spinal deformity (ASD), there is concern that overcorrection may lead to proximal junctional kyphosis (PJK). We introduce the upper instrumented vertebra–femoral angle (UIVFA) as a measure of appropriate postoperative position in the setting of lower thoracic to pelvis surgical correction for patients with sagittal imbalance. We hypothesize that a more posterior UIV position in relation to the center of the femoral head is associated with an increased risk of PJK given compensatory hyperkyphosis above the UIV.MethodsIn this retrospective cohort study, adult patients undergoing lower thoracic (T9–T12) to pelvis correction of ASD with a minimum of 2-year follow-up were included. UIVFA was measured as the angle subtended by a line from the UIV centroid to the femoral head center to the vertical axis. Patients who developed PJK and those who did not were compared with preoperative and postoperative UIVFA as well as change between postoperative and preoperative UIVFA (deltaUIVFA).ResultsOf 119 patients included with an average 3.6-year follow-up, 51 (42.9%) had PJK and 24 (20.2%) had PJF. Patients with PJK had significantly higher postoperative UIVFA (12.6 ± 4.8° vs. 9.4 ± 6.6°, p = 0.04), deltaUIVFA (6.1 ± 7.6° vs. 2.1 ± 5.6°, p < 0.01), postoperative pelvic tilt (27.3 ± 9.2 vs. 23.3 ± 11, p = 0.04), postoperative lumbar lordosis (47.7 ± 13.9° vs. 42.4 ± 13.1, p = 0.04) and postoperative thoracic kyphosis (44.9 ± 13.2 vs. 31.6 ± 18.8) than patients without PJK. With multivariate logistic regression, postoperative UIVFA and deltaUIVFA were found to be independent risk factors for PJK (p < 0.05). DeltaUIVFA was found to be an independent risk factor for PJF (p < 0.05). A receiver operating characteristic (ROC) curve for UIVFA as a predictor for PJK was established with an area under the curve of 0.67 (95% CI 0.59–0.76). Per the Youden index, the optimal UIVFA cut-off value is 11.5 degrees.ConclusionThe more posterior the UIV is from the femoral head center after lower thoracic to pelvis surgical correction for ASD, the more patients are at risk for PJK. The greater the magnitude of posterior translation of the UIV from the femoral head center from preop to postop, the greater the likelihood for PJF.

The Scoli-RISK 1 results of lower extremity motor function 5 years after complex adult spinal deformity surgery.

Neurologic complications after complex adult spinal deformity (ASD) surgery are important, yet outcomes are heterogeneously reported, and long-term follow-up of actual lower extremity motor function is unknown. To prospectively evaluate lower extremity motor function scores (LEMS) before and at 5years after surgical correction of complex ASD. Retrospective analysis of a prospective, multicenter, international observational study. The Scoli-RISK-1 study enrolled 272 ASD patients undergoing surgery from 15 centers around the world. Inclusion criteria were Cobb angle of > 80°, corrective osteotomy for congenital or revision deformity and/or 3-column osteotomy. Among patients with 5-year follow-up, comparisons of LEMS to baseline and within each follow-up period were made via documented neurologic exams on each patient. Seventy-seven (28.3%) patients had 5-year follow-up. Among these 77 patients with 5-year follow-up, rates of postoperative LEMS deterioration were: 14.3% hospital discharge, 10.7% at 6 weeks, 6.5% at 6months, 9.5% at 2years and 9.3% at 5years postoperative. During the 2-5year window, while mean LEMS did not change significantly (-0.5, p = 0.442), eight (11.1%) patients deteriorated (of which 3 were ≥ 4 motor points), and six (8.3%) patients improved (of which 2 were ≥ 4 points). Of the 14 neurologic complications, four (28.6%) were surgery-related, three of which required reoperation. While mean LEMS were not impacted in patients with a major surgery-related complication, mean LEMS were significantly lower in patients with neurologic surgery-related complications at discharge (p = 0.041) and 6 months (p = 0.008) between the two groups as well as the change from baseline to 5years (p = 0.041). In 77 patients undergoing complex ASD surgery with 5-year follow-up, while mean LEMS did not change from 2 to 5years, subtle neurologic changes occurred in approximately 1 in 5 patients (11.1% deteriorated; 8.3% improved). Major surgery-related complication did not result in decreased LEMS; however, those with neurologic surgery-related complications continued to have decreased lower extremity motor function at 5years postoperative. These results underscore the importance of long-term follow-up to 5years, using individual motor scores rather than group averages, and comparing outcomes to both baseline and last follow-up.

Novel Distributed Loading Technique Using Multimaterial, Long-Segment Spinal Constructs to Prevent Proximal Junctional Pathology in Adult Spinal Deformity Correction—Operative Technique and Radiographic Findings

Proximal junctional kyphosis (PJK) and proximal junction failure are common and costly complications after long-segment adult spinal deformity (ASD) correction. Although much research has focused on the concept of "softening the landing" to prevent proximal junction pathologies, long-segment constructs largely deviate from the force-deformation curve of the physiologic spine. Our novel distributed loading technique for ASD correction is described using multimaterial, long-segment constructs to create a biomechanically sound, yet physiologic, decremental stiffness toward the rostral end. Operative steps detail the custom-designed constructs of dual-headed pedicle screws and varied rod diameters and materials (cobalt chromium or titanium) for an initial 20 patients (mean 66.6 ± 4.8 years). Standing scoliosis films were obtained preoperatively and at regular intervals postoperatively to assess for PJK. No patient had evidence of PJK or proximal junction failure at latest radiographic follow-up (mean 17.9 months, range 13-25 months). Radiographic findings for sagittal vertical axis averaged 11.2 ± 5.6 cm preoperatively and 3.6 ± 2.3 cm postoperatively. Compared with preoperative parameters, postoperative reductions in pelvic incidence-lumbar lordosis mismatch averaged 28.7 ± 12.9 degrees, and sagittal vertical axis averaged 7.6 ± 5.2 cm while PJA was essentially unchanged. Preliminary results suggest that the distributed loading technique is promising for prevention of PJK with stiffness gradients that mimic the force-deformation curve of the physiologic posterior tension band. Our technique may optimize the degree of stress at the proximal junction without overwhelming the anterior column bony while remodeling and mature arthrodesis takes place.

Minimally invasive osteotomies for adult deformity

Correction of adult spinal deformity is associated with substantial improvements in patient quality of life. However, traditional open osteotomy techniques are associated with notably high rates of morbidity particularly when utilizing larger, more powerful, 3-column osteotomies. Data exists that support the use of minimally invasive posterior column osteotomies in the context of transforaminal lumbar interbody fusion, but further research is warranted to confirm the clinical utility of mini-open 3-column osteotomies.

P106. Normalization of pelvic tilt following corrective adult spinal deformity surgery: Analysis of prevalence, timing, and factors determining occurrence

<h3>BACKGROUND CONTEXT</h3> Increasing pelvic tilt (PT) is a primary compensatory mechanism in adult spinal deformity (ASD). By SRS-Schwab criteria, PT >20° is considered pathologic. Some ASD patients improve their PT following ASD correction, while others do not. The driving forces behind this lack of PT-response are not well defined. <h3>PURPOSE</h3> To determine the perioperative characteristics associated with PT normalization after ASD corrective surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> A total of 176 ASD patients. <h3>OUTCOME MEASURES</h3> Patient profile, radiographic parameters, and surgical factors associated with PT normalization. <h3>METHODS</h3> Operative ASD patients fused to S1/pelvis with full preoperative data as well as preoperative (BL), 6-week (6W), 1-year (1Y), and 2-year (2Y) postop PT measurements were included. PT normalization was assessed at 6W and 2-year follow-up. Univariate analyses were used to compare normalized (PTNorm) and non-normalized (NON) patients in terms of demographics, surgical and radiographic descriptors, postoperative alignment, and clinical outcomes. Multivariate regression and ROC curve assessed periop factors predicting 6W PT normalization. Conditional inference tree (CIT) determined thresholds for the continuous variables identified as independent predictors of PT normalization. <h3>RESULTS</h3> There were 176 ASD patients that met inclusion criteria (62.9±10.2years, 80%F, BMI 26.9±4.9 kg/m2, CCI: 1.88), and underwent surgery (levels fused 12.1±3.9, EBL: 1955mL, op time: 402min). At each time point, mean PT was as follows: BL: 25.7º, 6-week: 19.0º, 1-year: 21.2º, and 2-year: 22.3°. Patients classified as having normal PT by SRS-Schwab criteria (PT<20º): BL: 27.8%(n=49), 6W: 52.3%, 1-year: 47.2%, 2-year: 40.9%. Of the 127 patients with non-normal PT at BL, 50 (39.4%) normalized postoperatively by 6 weeks. Few patients normalized in PT after the 6-week mark: 7 by 1-year and another 2 by 2-year postop for a total of 37 2-year PTNorm patients. Sixteen patients with non-normal PT at BL normalized by 6W, but reverted at 2-year. Both 6 weeks and 2 years PTNorm patients had higher levels fused than NON patients (both p<0.05). 6W PTNorm patients were more likely to undergo combined approach(p=0.005). Two-year PTNorm patients were more likely to have undergone VCR(p=0.011). Normalized and non-normalized patients did not differ in BL SRS-Schwab PI-LL and SVA or in GAP proportionality (all p>0.05). Six weeks PTNorm patients were more likely to be overcorrected in PT, PI-LL, and SVA compared to NON patients at 6 weeks postop (all p<0.05). The same held true for 2-year PTNorm patients and 2-year radiographic alignment. Compared to non-normalized patients, both 6 weeks PTNorm patients and 2-year PTNorm patients had lower rates of implant failure and rod fracture (all p<0.05). 6W PTNorm patients had a lower revision rate(p=0.018). Binary logistic regression with CIT identified independent predictors of PT normalization by 6 weeks: undergoing combined approach, UIV at or above T8, levels fused >10, invasiveness score >109, baseline cSVA<41.5°, 6 weeks PI-LL diff ≥21.0°, 6 weeks sacral slope diff ≥7.9°, 6 weeks PT diff ≥7.5°; all p<0.05. Validation of a predictive model for 6 weeks normalized vs non-normalized patients including these factors yielded an AUC of 85.2%. <h3>CONCLUSIONS</h3> PT normalization following ASD correction occurred in almost 40% of patients by 6 weeks postop. Normalization is more likely to occur in patients where reconstruction addresses lumbopelvic mismatch, extends above the apex of the thoracic kyphosis, and has adequate surgical invasiveness to achieve full alignment correction. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P148. Determinants of cost ineffectiveness in adult spinal deformity surgery

<h3>BACKGROUND CONTEXT</h3> Adult spinal deformity correction has been demonstrated to result in improved pain and function. However, the financial implications of these procedures on health care systems can be profound, particularly when subject to complications/failures. <h3>PURPOSE</h3> Evaluate pre- and postoperative patient and surgical metrics, and to elucidate their relationship to total health care costs. <h3>STUDY DESIGN/SETTING</h3> Retrospective. <h3>PATIENT SAMPLE</h3> A total of 183 Adult Spinal Deformity (ASD) patients. <h3>OUTCOME MEASURES</h3> Utility Gained, Oswestry Disability Index (ODI), Cost, Quality Adjusted Life Year (QALY), Cost Effectiveness (Cost/QALY). <h3>METHODS</h3> The cohort was isolated to those who had baseline and 2-year Health Related Quality of Life (HRQL) data. Total cost was derived from PearlDiver, which accounts for costs within 30 days (including length of stay and mortality) differentiated by surgical approach, complications, and reoperation. Cost per Quality Adjusted Life Year (QALY), was calculated via published methods from ODI. Patients who did not have a positive utility gained indicated cost ineffectiveness. This cohort of patients (utility lost, UL) was compared to those who were cost effective (utility gained, UG) by means comparison analyses (chi-squared ANOVA) to determine the differentiating factors between cost ineffectiveness and effectiveness. Conditional Inference Tree analysis (CIT) ranked associated factors. <h3>RESULTS</h3> There were 183 patients, 53 (29.0%) UL and 140 (20.6%) UG. Patients in these groups differed in baseline radiographic and HRQL measurements as well as complication rates:Pelvic Tilt: UL=17.68; UG=24.25; p=0.001PI-LL: UL=3.52; UG=12.97; p=0.013L1-S1: UL=50.39; UG=41.06; p=0.021TPA: UL=14.91; UG=22.29; p=0.002SVA: UL=25.06; UG=53.01; p=0.011Any Complication: UL=32.1%; UG=48.5%; p=0.043Major Complication: UL=5.66%; UG=23.1%; p=0.005BL ODI: UL=18.96; UG=34.47; p<0.001Y2 ODI: UL=28.61; UG=16.88; p<0.001After CIT, the factors most associated with UL in descending order: BL pelvic tilt, BL T1 PA, Age, CCI, BL L1S1, operative time, number of major and minor complications, BL T2-T12 thoracic kyphosis, BL TS-CL, BL Frailty, BL cSVA. Factors that were most influential in a high overall cost in decreasing order by CIT: number of complications, number of reoperations, number of major and minor complications, BL cSVA, osteotomy, frailty, body mass index, LOS. <h3>CONCLUSIONS</h3> Patients that had Utility Lost had better HRQL scores and less severe radiographic measures at baseline compared to patients that were Utility Gained. This possibly indicates that instance of complications, despite being lower than those of Utility Gained, outweighed the benefits of surgery for Utility Lost patients who had less severe radiographic measures. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

192. The effects of global alignment and proportionality scores on postoperative outcomes following adult spinal deformity correction

<h3>BACKGROUND CONTEXT</h3> Restoring sagittal alignment in adult spinal deformity (ASD) surgery is a common goal to improve patient clinical outcomes and minimize long-term complications. Recent enthusiasm has suggested that achievement of global alignment and proportionality alignment may influence mechanical failures and as such may potentially influence ultimate outcomes. <h3>PURPOSE</h3> To investigate which components of the GAP score are most associated with patient-reported and clinical outcomes. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study of prospective, multicenter ASD database. <h3>PATIENT SAMPLE</h3> This study included 227 ASD patients. <h3>OUTCOME MEASURES</h3> Complications; health-related quality of life (HRQL): ODI, SRS-22r, SF-36. <h3>METHODS</h3> Operative ASD patients (scoliosis >20°, SVA>5cm, PT>25°, or TK>60 °,) with a fusion at L1 or higher with available baseline and 2-year radiographic and HRQL data were included. Multivariate analysis (MVA) was used to find an association between the global alignment and proportionality (GAP) score higher risk individual categories: moderately disproportioned (MD) - (GAP >2 and <7) and severely disproportioned (SD) - (GAP >7). Severe sagittal deformity was defined by a ++ in SRS-Schwab for SVA, or PI-LL. Mechanical complications excluded PJK. <h3>RESULTS</h3> A total of 227 ASD patients met the inclusion criteria (59.9yrs±14.0, 79%F, BMI: 27.7 kg/m2 ±6.0, ASD-FI: 3.3±1.6, CCI: 1.8 ±1.7). Surgically, patients had mean levels fused of 11.1±4.4, length of stay (LOS) of 7.9 days±4.4, estimated blood loss (EBL) of 1577 mL, operative time of 377 min, with 63% undergoing an osteotomy. In the full cohort, controlling for age, and CCI, MVA showed no association of GAP MD or SD patients with PJF, or mechanical complications, (p>0.05) but MD patients showed a positive correlation with development of PJK [OR: 2, 95% CI: 1-3.7, p<0.05]. In a cohort of patients with severe sagittal deformity, GAP MD (4.2[1.3-13.4]) and GAP SD (3.3[1.06-10]) criteria was predictive of PJK by 2 years, and in a cohort of patients 65 and older, GAP MD (5[1.4-18], p=.014) and GAP SD (3.6[1-12], p=.04) were also predictive of 2-year PJK development. There was no association with PJF or mechanical complications. In a cohort of patients with a history of prior fusion, or in patients less than 65 years of age, there was no correlation of GAP MD/GAP SD with PJK, PJF, or mechanical complications. The continuous 6W GAP score, as well as the GAP categories, did not show significant correlations with patient reported outcomes at 2 years. <h3>CONCLUSIONS</h3> Since the introduction of the global alignment and proportionality (GAP), literature has been inconclusive on the utility of the GAP score in clinical practice. Our study shows that the GAP score had strong predictive potential for proximal junctional kyphosis (PJK), specifically, in patients with severe baseline sagittal malalignment and/or those 65 and older, and, may have less utility in younger patients, or those with a previous fusion. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

171. Overcorrection of the upper instrumented vertebra relative to the center of the femoral heads is associated with proximal junctional kyphosis

<h3>BACKGROUND CONTEXT</h3> Although matching lumbar lordosis (LL) with pelvic incidence (PI) is an important surgical goal for adult spinal deformity (ASD), there is concern that overcorrection may lead to proximal junctional kyphosis (PJK). We introduce the upper instrumented vertebra – femoral angle (UIVFA) as a measure of appropriate postoperative position in the setting of lower thoracic to pelvis surgical correction for patients with sagittal imbalance. We hypothesize that a more posterior UIV position in relation to the center of the femoral head is associated with an increased risk of PJK given compensatory hyperkyphosis above the UIV. <h3>PURPOSE</h3> The purpose of this study is to evaluate if increased UIVFA is associated with PJK in operative management of ASD. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Adult patients undergoing lower thoracic (T9-T12) to pelvis correction of ASD with a minimum of two-year follow-up were included. <h3>OUTCOME MEASURES</h3> The primary outcome is PJK and proximal junctional failure (PJF). <h3>Methods</h3> In this retrospective cohort study, adult patients undergoing lower thoracic (T9-T12) to pelvis correction of ASD with a minimum of two-year follow-up were included. UIVFA was measured as the angle subtended by a line from the UIV centroid to the femoral head center to the vertical axis. UIV posterior to the femoral head center was positive (+) and UIV anterior the femoral head center was negative (-). A >10° kyphotic angle between the UIV and UIV+2 or a >10° increase from preop to postop were used to determine PJK. Patients with PJK that required revision surgery were defined as proximal junctional failure (PJF). Patients who developed PJK and those who did not were compared with preoperative and postoperative UIVFA, change between postoperative and preoperative UIVFA (deltaUIVFA), sagittal vertical axis (SVA), pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence minus lumbar lordosis (PI-LL), thoracic kyphosis at T5-12 (TK) and the central sacral vertical line (CSVL). <h3>Results</h3> Of the 119 patients included in the study with an average 3.6-year follow-up, 51 (42.9%) had PJK and 24 (20.2%) had PJF. The average preoperative UIVFA was 7.0±0.7°, the average postoperative UIVFA 10.8±0.6°, and the average deltaUIVFA was 3.8±0.6°. Patients with PJK had significantly higher postoperative UIVFA (12.6±4.8° vs 9.4±6.6°, p=0.04), deltaUIVFA (6.1±7.6° vs 2.1±5.6°, p<0.01), postoperative PT (27.3±9.2 vs 23.3±11, p=0.04), postoperative lumbar lordosis (47.7±13.9° vs 42.4±13.1, p=0.04) and postoperative thoracic kyphosis (44.9±13.2 vs 31.6±18.8) than patients without PJK at two-year follow-up. With multivariate logistic regression, postoperative UIVFA and deltaUIVFA were found to be independent risk factors for PJK (p<0.05). DeltaUIVFA was found to be an independent risk factor for PJF (p<0.05). A receiver operating characteristic (ROC) curve for UIVFA as a predictor for PJK was established with an area under the curve of 0.67 (95% CI: 0.59-0.76). Per the Youden index, the optimal UIVFA cut-off value is 11.5°. <h3>Conclusions</h3> The more posterior the UIV is from the femoral head center after lower thoracic to pelvis surgical correction for ASD, the more patients are at risk for PJK. The greater the magnitude of posterior translation of the UIV from the femoral head center from preop to postop, the greater the likelihood for PJF. Further investigation into the consequences of sagittal overcorrection in the setting of ASD is warranted. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

34. Optimal intraoperative fluid management in adult spinal deformity correction surgery

<h3>BACKGROUND CONTEXT</h3> Intraoperative fluid management is a vital component in adult spinal deformity (ASD) surgery that is not standardized nor has consensus on the ideal management. Increased intraoperative use of crystalloids and colloids is correlated with an increased risk for developing postoperative complications, especially pulmonary complications. <h3>PURPOSE</h3> This study aims to assess and describe the fluid management protocol for ASD at a single-center with minimal pulmonary complications, high intraoperative extubation rate, and no intraoperative coagulopathies. Hypothesis: Intraoperative fluid management using liberal amounts of crystalloids and reduced colloids is safe and results in optimal postoperative outcomes in ASD correction surgery. <h3>STUDY DESIGN/SETTING</h3> Observational, retrospective cohort. <h3>PATIENT SAMPLE</h3> A total of 161 consecutive surgical adult spinal deformity patients at a single institution. <h3>OUTCOME MEASURES</h3> Postoperative pulmonary complications and length of stay. <h3>METHODS</h3> A total of 161 consecutive ASD patients who underwent corrective surgery at a single institution were included. Preop medical records, intraoperative anesthesia and surgical records, and postop complications were compiled. Descriptive statistics including means, percentages, and ratios were calculated. <h3>RESULTS</h3> Average age was 44.6±18.7 years, 67% (108) were female, and 53% (85) were primary cases. The average number of levels fused was 11.4±5.2 and an average length of surgery of 7.4±2.4 hours. 18% (26) of patients had a 3-column osteotomy (PSO or VCR) and the average estimated blood loss was 1373±793ccs. Only 50.3% of patients received an intraoperative packed red blood cell transfusion and there was 1 patient that received platelets and 3 patients that received fresh frozen plasma transfusions. Average intraoperative crystalloids given was 4917±1778cc while the average colloids given was 1565±1190cc. The ratio of crystalloids:colloids administered intraoperatively was 3.1:1. A total of 84% (135) were extubated intraoperatively. Twenty patients had postoperative pulmonary complications of either pulmonary edema or pleural effusion and 2 patients had a pulmonary embolism, with an average length of stay of 7.0±3.9 days. <h3>CONCLUSIONS</h3> Minimizing blood loss and administering a 3:1 ratio of crystalloids:colloids is an optimal intraoperative fluid management protocol that results in no intraoperative coagulopathies, an 84% intraoperative extubation rate, and minimal postoperative pulmonary complications in adult spinal deformity correction surgery. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

Instrumentation Techniques to Prevent Proximal Junctional Kyphosis and Proximal Junctional Failure in Adult Spinal Deformity Correction: A Systematic Review of Clinical Studies.

Study Design:Systematic review.Objectives:To summarize the results of clinical studies investigating spinal instrumentation techniques aiming to reduce the postoperative incidence of proximal junctional kyphosis (PJK) and/or failure (PJF) in adult spinal deformity (ASD) patients.Methods:EMBASE and Medline® were searched for articles dating from January 2000 onward. Data was extracted by 2 independent authors and methodological quality was assessed using ROBINS-I.Results:18 retrospective- and prospective cohort studies with a severe or critical risk of bias were included. Different techniques were applied at the upper instrumented vertebra (UIV): tethers in various configurations, 2-level prophylactic vertebroplasty (2-PVP), transverse process hooks (TPH), flexible rods (FR), sublaminar tapes (ST) and multilevel stabilization screws (MLSS). Compared to a pedicle screw (PS) group, significant differences in PJK incidence were found using tethers in various configurations (18% versus 45%, P = 0.001, 15% versus 38%, P = 0.045), 2-PVP (24% vs 36%, P = 0.020), TPH (0% vs. 30%, P = 0.023) and FR (15% versus 38%, P = 0.045). Differences in revision rates for PJK were found in studies concerning tethers (4% versus 18%, P = 0.002), 2-PVP (0% vs 13%, P = 0.031) and TPH (0% vs 7%, P = n.a.).Conclusion:Although the studies are of low quality, the most frequently studied techniques, namely 2-PVP as anterior reinforcement and (tensioned) tethers or TPH as posterior semi-rigid fixation, show promising results. To provide a reliable comparison, more controlled studies need to be performed, including the use of clinical outcome measures and a uniform definition of PJF.

Safety of lateral access to the concave side for adult spinal deformity.

Minimally invasive surgery (MIS) techniques, particularly lateral lumbar interbody fusion (LLIF), have become increasingly popular for adult spinal deformity (ASD) correction. Much discussion has been had regarding theoretical and clinical advantages to addressing coronal curvature from the convex versus concave side of the curve. In this study, the authors aimed to broadly evaluate the clinical outcomes of addressing ASD with circumferential MIS (cMIS) techniques while accessing the lumbar coronal curvature from the concave side. A multi-institution, retrospective chart and radiographic review was performed for all ASD patients with at least a 10° curvature, as defined by the Scoliosis Research Society, who underwent cMIS correction. The data collected included convex versus concave access to the coronal curve, durable or sensory femoral nerve injury lasting longer than 6 weeks, vascular injury, visceral injury, and any additional major complication, with at least a 2-year follow-up. Neither health-related quality-of-life metrics nor spinopelvic parameters were included within the scope of this study. A total of 152 patients with ASD treated with cMIS correction via lateral access were identified and analyzed. Of these, 126 (82.9%) were approached from the concave side and 26 (17.1%) were approached from the convex side. In the concave group, 1 (0.8%) motor and 4 (3.2%) sensory deficit cases remained at 6 weeks after the operation. No vascular, visceral, or catastrophic intraoperative injuries were encountered in the concave group. Of the 26 patients in the convex group, 2 (7.7%) experienced motor deficits lasting longer than 6 weeks and 5 (19.2%) had lower-extremity sensory deficits. It has been reported that lateral access to the convex side is associated with similar clinical and radiographic outcomes with fewer complications when compared with access to the concave side. Advantages to approaching the lumbar spine from the concave side include using one incision to access multiple levels, breaking the operative table to assist with curvature correction, easier access to the L4-5 disc space, the ability to release the contracted side, and, often, avoidance of the need to access or traverse the thoracic cavity. This study illustrates the largest reported cohort of concave access for cMIS scoliosis correction; few postoperative sensory and motor deficits were found.

Timing of conversion to cervical malalignment and proximal junctional kyphosis following surgical correction of adult spinal deformity: a 3-year radiographic analysis.

The goal of this study was to assess the conversion rate from baseline cervical alignment to postoperative cervical deformity (CD) and the corresponding proximal junctional kyphosis (PJK) rate in patients undergoing thoracolumbar adult spinal deformity (ASD) surgery. The operative records of patients with ASD with complete radiographic data beginning at baseline up to 3 years were included. Patients with no baseline CD were postoperatively stratified by Ames CD criteria (T1 slope-cervical lordosis mismatch [TS-CL] > 20°, cervical sagittal vertical axis [cSVA] > 40 mm), where CD was defined as fulfilling one or more of the Ames criteria. Severe CD was defined as TS-CL > 30° or cSVA > 60 mm. Follow-up intervals were established after ASD surgery, with 6 weeks postoperatively defined as early; 6 weeks-1 year as intermediate; 1-2 years as late; and 2-3 years as long-term. Descriptive analyses and McNemar tests identified the CD conversion rate, PJK rate (< -10° change in uppermost instrumented vertebra and the superior endplate of the vertebra 2 levels superior to the uppermost instrumented vertebra), and specific alignment parameters that converted. Two hundred sixty-six patients who underwent ASD surgery (mean age 59.7 years, 77.4% female) met the inclusion criteria; 103 of these converted postoperatively, and the remaining 163 did not meet conversion criteria. Thirty-eight patients converted to CD early, 26 converted at the intermediate time point, 29 converted late, and 10 converted in the long-term. At conversion, the early group had the highest mean TS-CL at 25.4° ± 8.5° and the highest mean cSVA at 33.6 mm-both higher than any other conversion group. The long-term group had the highest mean C2-7 angle at 19.7° and the highest rate of PJK compared to other groups (p = 0.180). The early group had the highest rate of conversion to severe CD, with 9 of 38 patients having severe TS-CL and only 1 patient per group converting to severe cSVA. Seven patients progressed from having only malaligned TS-CL at baseline (with normal cSVA) to CD with both malaligned TS-CL and cSVA by 6 weeks. Conversely, only 2 patients progressed from malaligned cSVA to both malaligned cSVA and TS-CL. By 1 year, the former number increased from 7 to 26 patients, and the latter increased from 2 to 20 patients. The revision rate was highest in the intermediate group at 48.0%, versus the early group at 19.2%, late group at 27.3%, and long-term group at 20% (p = 0.128). A higher pelvic incidence-lumbar lordosis mismatch, lower thoracic kyphosis, and a higher thoracic kyphosis apex immediately postoperatively significantly predicted earlier rather than later conversion (all p < 0.05). Baseline lumbar lordosis, pelvic tilt, and sacral slope were not significant predictors. Patients with ASD with normative cervical alignment who converted to CD after thoracolumbar surgery had varying radiographic findings based on timing of conversion. Although the highest number of patients converted within 6 weeks postoperatively, patients who converted in the late or long-term follow-up intervals had higher rates of concurrent PJK and greater radiographic progression.

Predicting Reciprocal Thoracic Change, Proximal Junctional Kyphosis, and Revision Surgery in Adult Spinal Deformity

Compensatory mechanisms in patients with adult spinal deformity (ASD) that lead to poor quality of life include positive sagittal balance and pelvic retroversion. The objective of this retrospective review was to identify demographic and radiographic parameters of sagittal alignment that are correlated with thoracic kyphosis (TK), PJK, and reoperation in patients undergoing surgical correction for ASD. A single-center database of 155 patients with ASD undergoing surgery from 2008 to 2015 was reviewed. Patients >18 years old who underwent multilevel thoracolumbar fusion or fusion of thoracic vertebrae to the pelvis were included. Demographics and radiographic measurements of sagittal alignment were collected preoperatively, 6 weeks postoperatively, and 1 year postoperatively. Statistical analysis was performed to compare groups that did or did not develop change in thoracic kyphosis or PJK at early or late follow-up. Additionally, patients requiring reoperation were evaluated. Increased thoracic kyphosis was associated with older age, hypolordosis, and comorbid PJK. Early PJK was associated with older age, hypolordosis, and increased T1 pelvic angle. Reoperation was associated with older age, higher positive sagittal balance, hypolordosis, and pelvic retroversion; PJK and thoracic kyphosis did not increase risk for reoperation. Thoracic reciprocal change following surgical correction of ASD is highly associated with PJK, although neither increased risk of reoperation. PJK may be predicted by older age, hypolordosis, and increased T1 pelvic angle. Reoperation in patients with ASD is more likely in older patients with positive sagittal balance, a compensatory flat lower back, and compensatory pelvic retroversion.

Posterior Displacement of L1 May be a Risk Factor for Proximal Junctional Kyphosis After Adult Spinal Deformity Correction.

Retrospective cohort study. Overcorrection in adult spinal deformity (ASD) surgery may lead to proximal junctional kyphosis (PJK) because of posterior spinal displacement. The aim of this paper is to determine if the L1 position relative to the gravity line (GL) is associated with PJK. ASD patients fused from the lower thoracic spine to sacrum by 4 spine surgeons at our hospital were retrospectively studied. Lumbar-only and upper thoracic spine fusions were excluded. Spinopelvic parameters, the L1 plumb line (L1PL), L1 distance to the GL (L1-GL), and Roussouly type were measured. One hundred fourteen patients met inclusion criteria (63 patients with PJK, 51 without). Mean age and follow up was 65.51 and 3.39 years, respectively. There was no difference between the PJK and the non-PJK groups in baseline demographics, pre-operative and immediate post-operative pelvic incidence-lumbar lordosis mismatch, sagittal vertical axis, or coronal Cobb. The immediate postoperative L1-GL was -7.24 cm in PJK and -3.45 cm in non-PJK (P < 0.001), L1PL was 1.71 cm in PJK and 3.07 cm in non-PJK (P = 0.004), and PT (23.76° vs 18.90°, P = 0.026) and TK (40.56° vs 31.39°, P < 0.001) were larger in PJK than in non-PJK. After univariate and multivariate analyses, immediate postoperative TK and immediate postoperative L1-GL were independent risk factors for PJK without collinearity. A dorsally displaced L1 relative to the GL was associated with an increased risk of PJK after ASD surgery. The postoperative L1-GL distance may be a factor to consider during ASD surgery.

Optimal Correction of Adult Spinal Deformities Requires Restoration of Distal Lumbar Lordosis.

Purpose The aim of this study is to analyze results according to postoperative pelvic incidence-lumbar lordosis (PI-LL) mismatch in the management of adult spine deformity (ASD) patients. Recently, it has been reported that in addition to lumbar lordosis amount, lordosis repartition between its proximal and distal parts was crucial. Methods We enrolled 77 consecutive ASD patients who underwent posterior spinal fusion and deformity correction between 2015 and 2018. On preoperative and 1-year follow-up radiographs, we analyzed different parameters such as L1-S1 lumbar lordosis, L1-L4 proximal lordosis (PLL), L4-S1 distal lordosis (DLL), pelvic tilt (PT), sagittal vertical axis (SVA), and PI-LL mismatch. Comparisons were performed according to postoperative PI-LL mismatch (defined as “aligned” when PI-LL was <10°). The relationship between lordosis distribution and postoperative alignment status was investigated. Results On the whole series, average lumbar lordosis, SVA, and PI-LL improved (28.2° vs.43.5°, 82 vs. 51 mm, and 26°vs. 14°, all p < 0.001, respectively). On the other hand, PT remained unchanged (30° vs. 28°, p > 0.05). 35 patients were classified as “aligned” and 42 as “not aligned.” Patients from the “aligned” group had a significantly lower PI than patients from the “not aligned” group (52° vs. 61°, p=0.009). Postoperative PLL was not different between groups (18° vs. 16° p > 0.05), whereas DLL was significantly higher in the “aligned” group (31° vs. 22°, p=0.003). PI-LL was significantly correlated to DLL (rho = 0.407, p < 0.001) but not with PLL (rho = 0.110, p=0.342). Conclusions Our results revealed that in ASD patients, postoperative malalignment was associated with a lack of DLL restoration. “Not aligned” patients had also a significantly higher pelvic incidence. Specific attention must be paid to restore optimal distal lumbar lordosis in order to set the amount and the distribution of optimal postoperative lumbar lordosis.