Postoperative PI-LL Research Articles

Preoperative Planning of Lumbar Lordosis for Adult Degenerative Scoliosis Surgery in the Chinese Population

Pelvic incidence minus lumbar lordosis mismatch (PI-LL) is directly related to poor quality of life in adult degenerative scoliosis (ADS) patients. The purpose of the study was to determine the most appropriate postoperative PI-LL value for patients with ADS. The medical records of patients with ADS in our department were retrospectively collected. The data included age, sex, body mass index, age-adjusted Charlson comorbidity index, osteopenia, length of hospital stay, operative duration, estimated blood loss, American Society of Anesthesiologists score, number of fusion levels, lumbar lordosis, sagittal vertical axis, pelvic incidence, PI-LL, Scoliosis Research Society-22 score, Oswestry Disability Index score, and mechanical complications. A total of 316 patients were enrolled. PI-LL, lumbar lordosis, sagittal vertical axis, Scoliosis Research Society-22 score, Oswestry Disability Index score at the time of last follow-up were 20.7 ± 8.5°, 23.4 ± 14.1°, 4.0 ± 2.1cm, 3.7 ± 0.9, and 18.1 ± 5.5, respectively. In terms of mechanical complications, 88 patients (27.8%), 34 patients (10.8%), and 19 patients (6.0%) had proximal junctional kyphosis, distal junctional kyphosis, and implant-related complications, respectively. In the fully adjusted model, compared with 0 grade PI-LL group and++ grade PI-LL group,+ grade PI-LL group had the best clinical outcomes and the fewest mechanical complications. The stability of these conclusions was verified in sensitivity analyses. Optimal PI-LL value should be 10°-20° after corrective surgery in patients with ADS, which is associated with excellent clinical outcomes and lower complication rates. Previous criteria may be at risk of overcorrection, which may lead to proximal junctional kyphosis.

Bone Quality as Measured by Hounsfield Units More Accurately Predicts Proximal Junctional Kyphosis than Vertebral Bone Quality Following Long-Segment Thoracolumbar Fusion

To compare the prognostic power of Hounsfield units (HU) and Vertebral Bone Quality (VBQ) score for predicting proximal junctional kyphosis (PJK) following long-segment thoracolumbar fusion to the upper thoracic spine (T1-T6). Vertebral bone quality around the upper instrumented vertebrae (UIV) was measured using HU on preoperative CT and VBQ on preoperative MRI. Spinopelvic parameters were also categorized according to the Scoliosis Research Society-Schwab classification. Univariable analysis to identify predictors of the occurrence of PJK and survival analyses with Kaplan-Meier method and Cox regression were performed to identify predictors of time to PJK (defined as ≥10° change in Cobb angle of UIV+2 and UIV). Sensitivity analyses showed thresholds of HU < 164 and VBQ > 2.7 to be most predictive for PJK. Seventy-six patients (mean age 66.0 ± 7.0 years; 27.6% male) were identified, of whom 15 suffered PJK. Significant predictors of PJK were high postoperative pelvic tilt (P= 0.038), high postoperative T1-pelvic angle (P= 0.041), and high postoperative PI-LL mismatch (P= 0.028). On survival analyses, bone quality, as assessed by the average HU of the UIV and UIV+1 was the only significant predictor of time to PJK (odds ratio [OR] 3.053; 95% CI 1.032-9.032; P= 0.044). VBQ measured using the UIV, UIV+1, UIV+2, and UIV-1 vertebrae approached, but did not reach significance (OR 2.913; 95% CI 0.797-10.646; P= 0.106). In larger cohorts, VBQ may prove to be a significant predictor of PJK following long-segment thoracolumbar fusion. However, Hounsfield units on CT have greater predictive power, suggesting preoperative workup for long-segment thoracolumbar fusion benefits from computed tomography versus magnetic resonance imaging alone to identify those at increased risk of PJK.

286 Bone Quality as Measured by Hounsfield Units More Accurately Predicts Proximal Junctional Kyphosis Than Vertebral Bone Quality Following Long-segment Thoracolumbar Fusion

INTRODUCTION: Both Hounsfield units (HU) on computed tomography and Vertebral Bone Quality (VBQ) score on MRI have been advanced as means of assessing underlying bone quality and predicting mechanical complications amongst spine patients. METHODS: Patients = 50 with =12-month follow-up following long-segment thoracolumbar fusion were included. Bone quality around the upper instrumented vertebrae (UIV) was measured using HU on preoperative CT and VBQ on preoperative MRI. Spinopelvic parameters were also measured. PJK was defined as a change of =10° in the Cobb angle between the cephalad endplate of UIV+2 and caudal endplate of UIV. Univariable analysis to identify predictors of the occurrence of PJK and survival analyses with Kaplan-Meier method and Cox regression were performed to identify predictors of time to PJK. Sensitivity analyses showed thresholds of HU &lt; 164 and VBQ &gt; 2.7 to be most predictive for PJK. RESULTS: Seventy-six patients (66.0 ± 7.0 yr; 27.6% male) were identified, with 15 suffering PJK. On univariable analyses PJK was predicted by high postoperative pelvic tilt (p = 0.038), postoperative T1-pelvic angle (p=0.041), and postoperative PI-LL mismatch (p = 0.028). On multivariable survival analysis, bone quality, as assessed by average HU of the UIV and UIV+1 was the only significant predictor of time to PJK (OR=3.053; 95%CI [1.032, 9.032]; p = 0.044). VBQ measured using the UIV, UIV+1, UIV+2, and UIV-1 vertebrae approached, but did not reach significance (2.913; [0.797, 10.646]; 0.106). CONCLUSIONS: In larger cohorts, VBQ may prove to be a significant predictor of PJK following long-segment thoracolumbar fusion. However, it has less predictive power than Hounsfield units on CT, suggesting preoperative workup for patients undergoing long-segment thoracolumbar fusion may benefit from CT versus MRI alone to identify those at increased risk of PJK.

1073 Prone Transpsoas (PTP)-LLIF Approach Versus Standard LLIF in Patients Undergoing Surgical Revision Following Adult Spinal Deformity Correction Surgery

INTRODUCTION: Both the prone transpsoas (PTP) and standard LLIF have been developed to facilitate minimally invasive (MIS) indirect decompression, alignment correction, and posterior instrumentation. METHODS: A multi-center cohort of all patients was identified and all relevant data were retrospectively collected. Preoperative standing 36” scoliosis radiographs were retrospectively reviewed for pelvic incidence (PI), lumbar lordosis (LL), and PI minus LL (PI-LL mismatch). Postoperative regional sagittal alignment parameters were measured using the first postoperative standing 36” scoliosis radiographs. Finally, multivariable analysis was performed to assess the primary outcome measure: postoperative change in regional sagittal alignment (PI-LL mismatch). RESULTS: Two-hundred and two (n = 202) patients were retrospectively identified and included for formal analysis. One-hundred and fifty one (n = 151, 74.8%) of the patients underwent PTP revision while 51 (25.2%) underwent standard LLIF revision. Univariate analysis demonstrated a greater value for baseline mean pre-operative PI-LL mismatch in the PTP versus standard LLIF cohort (21.4 vs. 10.45°; p = 0.0001). Furthermore, multiple linear regression demonstrated that the PTP approach enabled significantly greater PI-LL mismatch change (p = 0.0017) and that this change was associated with the number of levels fused (p = 0.0481) as well as percutaneous (vs. open) screw placement (p = 0.0193). Finally, multiple logistic regression identified standard LLIF (p = 0.0378), female sex (p &lt; 0.0001), non-osteoporotic bone density (p &lt; 0.0001), and younger age (p &lt; 0.0001) as predictive of postoperative PI-LL mismatch &lt; 10° (the threshold under which such mismatch is no longer regarded as clinically significant deformity). CONCLUSIONS: Ultimately, PTP-LLIF was associated with greater net improvement in postoperative PI-LL mismatch, the primary outcome measure of this study. The present retrospective analysis therefore corroborated results of previous studies in suggesting that the utility of PTP-LLIF is translatable to ASD revision surgery.

Automated machine learning-based model for the prediction of pedicle screw loosening after degenerative lumbar fusion surgery.

The adequacy of screw anchorage is a critical factor in achieving successful spinal fusion. This study aimed to use machine learning algorithms to identify critical variables and predict pedicle screw loosening after degenerative lumbar fusion surgery. A total of 552 patients who underwent primary transpedicular lumbar fixation for lumbar degenerative disease were included. The LASSO method identified key features associated with pedicle screw loosening. Patient clinical characteristics, intraoperative variables, and radiographic parameters were collected and used to construct eight machine learning models, including a training set (80% of participants) and a test set (20% of participants). The XGBoost model exhibited the best performance, with an AUC of 0.884 (95% CI: 0.825-0.944) in the test set, along with the lowest Brier score. Ten crucial variables, including age, disease diagnosis: degenerative scoliosis, number of fused levels, fixation to S1, HU value, preoperative PT, preoperative PI-LL, postoperative LL, postoperative PT, and postoperative PI-LL were selected. In the prospective cohort, the XGBoost model demonstrated substantial performance with an accuracy of 83.32%. This study identified crucial variables associated with pedicle screw loosening after degenerative lumbar fusion surgery and successfully developed a machine learning model to predict pedicle screw loosening. The findings of this study may provide valuable information for clinical decision-making.

Development of End-to-End Artificial Intelligence Models for Surgical Planning in Transforaminal Lumbar Interbody Fusion.

Transforaminal lumbar interbody fusion (TLIF) is a commonly used technique for treating lumbar degenerative diseases. In this study, we developed a fully computer-supported pipeline to predict both the cage height and the degree of lumbar lordosis subtraction from the pelvic incidence (PI-LL) after TLIF surgery, utilizing preoperative X-ray images. The automated pipeline comprised two primary stages. First, the pretrained BiLuNet deep learning model was employed to extract essential features from X-ray images. Subsequently, five machine learning algorithms were trained using a five-fold cross-validation technique on a dataset of 311 patients to identify the optimal models to predict interbody cage height and postoperative PI-LL. LASSO regression and support vector regression demonstrated superior performance in predicting interbody cage height and postoperative PI-LL, respectively. For cage height prediction, the root mean square error (RMSE) was calculated as 1.01, and the model achieved the highest accuracy at a height of 12 mm, with exact prediction achieved in 54.43% (43/79) of cases. In most of the remaining cases, the prediction error of the model was within 1 mm. Additionally, the model demonstrated satisfactory performance in predicting PI-LL, with an RMSE of 5.19 and an accuracy of 0.81 for PI-LL stratification. In conclusion, our results indicate that machine learning models can reliably predict interbody cage height and postoperative PI-LL.

Clinical Significance of Lordosis Orientation on Proximal Junctional Kyphosis Development in Long-Segment Fusion Surgery for Adult Spinal Deformity

To evaluate the clinical impact of lordosis orientation (LO) on proximal junctional failure (PJK) development in adult spinal deformity (ASD) surgery METHODS: This study included 152 patients who underwent low thoracic (T9 -T12) to pelvis fusion and followed up for ≥2 years. In the literature, six radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV - femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors, including six LO parameters, were investigated using logistic regression analysis to identify risk factors for PJK. The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI) - lumbar lordosis (LL) (Odds ratio [OR] = 0.962, 95% CI : 0.929 - 0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% CI : 1.028 - 1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = -0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle. LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection as well as overcorrection to prevent PJK development.

Patient-specific spinal rods in adult spinal deformity surgery reduce proximal junctional failure: a review of patient outcomes and surgical technique in a prospective observational cohort.

Spinal rods used for adult spinal deformity (ASD) correction are usually manufactured straight and bent manually during surgery. Pre-bent patient-specific spinal rods (PSSR) developed with software provide the surgeon with an intraoperative deformity correction consistent with the surgical plan. Our aim was to report clinical and radiological outcomes using PSSR. We investigated rates of junctional complications both proximally [kyphosis (PJK) and failure (PJF)] and distally [failure (DJF)]. Prospective case series of 20 consecutive patients who underwent ≥4 level ASD surgery with PSSR at a single institution between January 2019 and December 2022. Preoperative, 6-week, 6-month, 12-month, 24-month, and final follow-ups assessed patient satisfaction (Ottawa decision regret questionnaire) and patient reported outcome measures (PROMs) [visual analogue scale (VAS; Back/Leg), Oswestry disability index (ODI), and 12-Item Short Form Survey (SF-12)]. Sagittal spinopelvic parameters [sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence and lumbar lordosis mismatch (PI-LL)] measured by serial EOS scans were performed preoperatively then compared to planned correction and postoperative measures. Interoperative cages (narrow/wide) were placed for interbody support. PJK risk score assessed likelihood of developing kyphosis. Serial computed tomography (CT) imaging assessed complication (fusion/subsidence). The mean age of the patients (75% female) was 71.9±6.9 years, and the mean follow-up was 25.2±8.6 [7-40] months. Preoperative mean PROMs showed statistically significant overall improvement (P<0.001) postoperatively to final follow-up. Four patients without wide footprint cages at L4/5 or L5/S1, suffered DJF and reported regret undergoing surgery. Statistically significant difference (P<0.001) between preoperative and surgical plan in SVA and PI-LL but not in PT (P=0.058). No statistically significant difference in surgical plan versus the postoperative SVA, PI-LL, and PT (due to difficulty achieving the surgical plan, and also to maintaining the correction). One patient suffered PJF. There was a mean proximal kyphotic angle (PKA) of 17.8±13.0 degrees and PJK risk score of 3.7±1.0 with 40% who experienced PJK. No rod breakages were observed. In this series, PSSR improved PROMs and treated ASD. Sagittal parameters planned preoperatively correlated with postoperative correction. PJF was reduced, compared to the literature (35%), but PJK was observed over time. DJF occurred and was related to the absence of interbody cages at the lumbosacral junction and decisional regret.

Effect of spinal-pelvic sagittal balance on the clinical outcomes after lumbar fusion surgery

BackgroundSpinal-pelvic sagittal balance is important for maintaining energy-efficient posture in normal and diseased states.Few reports to date have evaluated the effect of spinal-pelvic sagittal balance on clinical outcomes after lumbar interbody fusion in patients with lumbar degenerative diseases (LDD).MethodsA total of 303 patients treated with posterior lumbar interbody fusion surgery for lumbar degenerative disease from January 2012 to December 2019 were enrolled in this retrospective study according to the inclusion criteria. Preoperative and postoperative spinal-pelvic sagittal parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS) and lumbar lordosis (LL) of the patients were evaluated and compared. 163 patients whose postoperative PI-LL ≤ 10° were divided into the spinal-pelvic match group (Group M), while 140 patients were divided into the spinal-pelvic mismatch group (Group MM). Preoperative and postoperative Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) for back pain of both groups were compared.ResultsThere was no significant difference between the two groups in demographic and surgical data, except for blood loss in surgery. LL, PI, PT and SS of the patients at final follow-up were all statistically different from the preoperative values in the two groups(P < 0.05). There was no significant difference in LL, PI, PT and SS between the two groups before surgery. At the final follow-up, LL, PI and PT differed significantly between the two groups(P < 0.05). Compared with the preoperative results, ODI and VAS of low back in both groups decreased significantly at the final follow-up (P < 0.05). Significant differences in VAS and ODI were found between the two groups at the final follow-up (P < 0.05). The improvement rates of VAS and ODI of Group M are both significantly higher than Group MM. Regression analysis showed that age and spinal-pelvic match had significant effects on the improvement of patients’ low back pain at the final follow-up.Conclusionslumbar interbody fusion can significantly improve the prognosis of patients with LDD. In terms of outcomes with an average follow-up time of more than 2 years, the spinal-pelvic match has a positive effect on patients’ quality of life and the release of low back pain.

How Does Spino-Pelvic Fixation Affect Post-Operative Compensatory Mechanisms in Adult Spinal Deformity?

Retrospective single-center multi-surgeon cohort study. Compare the post-operative changes in the compensatory mechanisms of the sagittal balance according to the type of pelvic fixation: S2-Alar-iliac screws (S2AI) vs iliac screws (IS) in patients with Adult spine deformity (ASD). ASD patients who underwent spino-pelvic fixation and remained with a PI-LL >10° mismatch post-operatively were included. Pre-operative and 1-year-follow-up PI, Lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (TK), femur obliquity angle (FOA), knee flexion angle (KFA) and ankle flexion angle (AFA) were analyzed on EOS imaging. Patients were categorized based on their pelvic fixation type (S2AI vs IS), and the pre-operative to 1-year-post-operative changes (ΔX°) in the compensatory mechanisms were compared between groups. Patients with S2AI (n = 53) and those with IS (n = 26) screws were comparable at baseline. ΔSS averaged 9.87° in the S2AI compared to 13.2° in the IS (P = .001), whereas the ΔKFA reached 6.01° in the S2AI as opposed to 3.06° in the IS (P = .02). The ΔPT was comparable between both groups (6.35°[S2AI group] vs 5.21°[ISgroup], P = .42). ΔTK, ΔLL, ΔFOA and ΔAFA were comparable between both groups. The type of pelvic fixation impacts significantly the post-operative compensatory mechanisms in patients with ASD. Patients with S2AI screws are more likely to compensate their remaining post-operative PI-LL mismatch through their knees and less likely through their pelvis compared to patients with IS, despite similar changes in PT. This could be explained by an increased SI joint laxity in ASD patient and the lower resistance of the iliac connectors to the junctional mechanical stresses, allowing for sacro-iliac joint motion in patients with IS.

Sarcopenia at the upper instrumented vertebra is more significantly associated with proximal junctional kyphosis after long fusion for adult spinal deformity surgery than osteopenia

Proximal junctional kyphosis (PJK) is a major mechanical complication after adult spinal deformity (ASD) surgery, and is multifactorial. Osteopenia and sarcopenia are patient risk factors, but it has not yet been well-documented which of them is the more significant risk factor. We retrospectively studied patients older than 50 years who underwent ASD surgery from the lower thoracic spine to the pelvis. In addition to patient demographic data and pre- and post-operative radiographic sagittal parameters (PI: pelvic incidence; LL: lumbar lordosis; SVA: sagittal vertical axis; PT: pelvic tilt), Hounsfield unit (HU) values on preoperative computed tomography and cross sectional area (CSA) and fatty infiltration ratio (FI%) of the paraspinal musculature (PSM) on preoperative magnetic resonance image were measured from the upper-instrumented vertebra (UIV) to UIV + 2 and averaged. PJK was observed in 11 of 29 patients. There was no statistical difference between the patients with and without PJK in age at surgery, sex, body mass index, bone mineral density, preoperative PI-LL, SVA, PT, postoperative PI-LL, SVA, PT, HU, and CSA. FI% in patients with PJK (25.0) was significantly higher than that (15.3) in patients without PJK (P = 0.001). Logistic regression analysis identified FI% of PSM as a significant independent factor of PJK (odds ratio, 1.973; 95% confidence interval, 1.290–5.554; P < 0.0001). After successful elimination of possible factors related to PJK other than sarcopenia and osteopenia, sarcopenia assessed by fatty degeneration of the PSM at the UIV was shown to be a more important factor than osteopenia for PJK after long fusion for ASD.

Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change Be Affected By the Type of Pelvic Fixation?

Retrospective review. To assess the change in pelvic incidence (PI) after lumbo-pelvic fixation and the differential impact of the type of pelvic fixation: S2-alar-iliac screws(S2AI) versus Iliac screws(IS) on post-operative PI. Recent studies suggest that changes occur to the previously assumed fixed PI after spino-pelvic fixation. Adult spine deformity(ASD) patients who underwent spino-pelvic fixation with≥4 levels fusion were included. Pre-operative and post-operative PI, lumbar lordosis(LL), thoracic kyphosis(TK), pelvic tilt(PT), sacral slope(SS), PI-LL mismatch and the Sagittal Vertical Axis(SVA) were analyzed on EOS imaging. A significant PI change was established at≥6⁰. Patients were categorized based on the type of pelvic fixation (S2AI vs. IS). One-hundred-forty-nine patients were included. Of these, 77(52%) had a>6⁰ change in their PI post-operatively. In patients with high pre-operative PI (>60⁰), 62% had a significant PI change compared to 33% of patients with normal PI (40⁰-60⁰) and 53% in patients with low PI(<40⁰; P=0.01). PI was likely to decrease in patients with high baseline PI (>60⁰) and to increase in patients with low baseline PI (<40⁰). Patients with a significant PI change had a higher PI-LL. Patients in the S2AI group (n=99) and those in the IS group (n=50) were comparable at baseline. In the S2AI group, 50 (51%) patients had>6⁰ change in their PI compared to 27(54%) patients in the IS group(P=0.65). In both groups, patients with high pre-operative PI were more prone to significant post-operative changes (P=0.02 in IS, P=0.01 in S2AI). PI changed significantly in 50% of patients post-operatively, especially in those with high/low pre-operative PI and those with severe baseline sagittal imbalance. This occurs similarly in patients with S2AI and those with IS screws. Surgeons should keep in mind these anticipated changes while planning ideal LL, as this impacts post-operative PI-LL mismatch. IV.

Prediction of Pedicle Screw Loosening Using an MRI-Based Vertebral Bone Quality Score in Patients with Lumbar Degenerative Disease

To explore a new magnetic resonance imaging (MRI)-based bone quality assessment method for predicting pedicle screw loosening in the lumbar spine. We reviewed 174 patients aged ≥50years who were treated for lumbar degenerative diseases using posterior lumbar interbody fusion. All patients were followed-up for ≥12months. Based on the presence of radiolucent areas on follow-up MRI images, the patients were divided into loosening and nonloosening groups. The vertebral bone quality (VBQ) score was calculated using T1-weighted MRI images. Demographic data, health history, and radiological parameters were also recorded and compared between the 2 groups. Logistic regression analysis was used to predict the independent risk factors affecting screw loosening. Screw loosening occurred in 29.88% (52/174) of patients. A total of 83 screws (9.18%, 83/904) were loosened. There were differences in the age, fixation length, fixation at S1, preoperative and postoperative PI-LL, PT, preoperative LL, lowest bone mineral density (BMD), and VBQ scores (P<0.05) between the nonloosening and loosening groups. In the logistic regression, the VBQ score (OR=1.02 per point; 95% CI: 1.01-1.03; P < 0.001) was identified as an independent factor influencing screw loosening. As an independent risk factor for screw loosening after lumbar spine fusion, the VBQ score provides a new noninvasive protocol for assessing bone quality during surgical planning.

Clinical Application of the Roussouly Classification in the Sagittal Balance Reconstruction of 101 Adolescent Idiopathic Scoliosis Patients.

Although Roussouly classification has been widely used in spinal surgery, it was mainly applied to degenerative scoliosis patients and correlational studies concerning adolescent idiopathic scoliosis (AIS) are still insufficient. This retrospective study explored the clinical application of Roussouly classification in surgeries and prognosis prediction for AIS. This clinical research selected 101 AIS patients who received surgeries between August 2005 and November 2019. Whole spine standing radiographs were obtained for each patient preoperatively, postoperatively, and at the last follow-up (>24months). All patients were classified into "theoretical types" and "current types." Patients were further divided into mismatch or match groups based on the consistency of their current type and theoretical type. The main parameters include: proximal junctional angle (PJA), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), fixed thoracic kyphosis (TK), global TK, fixed lumbar lordosis (LL), global LL, thoracic tilt, proximal thoracic alignment (PTA), lumbar tilt, spino-sacral angle (SSA), and spinal tilt (ST). A total of 47.5% of AIS patients were subject to a preoperative mismatch of Roussouly classification. There was a significant difference in PI-LL between the preoperative mismatch and match groups (p=0.008). There was a significant difference in the rate of PI-LL deformity between the match and mismatch groups with a preoperative mismatch (p=0.037). A significant difference in thoracic tilt was observed between the postoperative mismatch and match groups (p=0.019). The preoperative mismatch group has a higher risk of postoperative PI-LL malformation than match group (OR=2.303, 95% CI: 1.026, 5.165). When mismatch occurred postoperatively, there were significant differences between groups in the rate of pelvic deformity (p=0.002) and PI-LL deformity (p=0.025) at the last follow-up. Compared with the postoperative match group, mismatch group had an increased risk of pelvic deformity (OR=5.029, 95% CI: 1.618, 15.629) and PJK deformity (OR=3.017, 95% CI: 1.709, 11.375) at the last follow-up. Short Form-36 and Scoliosis Research Society 22 score of the match group was significantly higher than that of the mismatch group at the last follow-up. The Roussouly classification mismatch before or after operation leads to increased risks of PI-LL deformity and pelvis deformity postoperatively or at the follow-up, which seriously worsens the clinical symptoms and prognosis of patients. Therefore, recovering to the theoretical type in Roussouly classification may effectively improve patients' prognosis.

92. Distinctions between two-year recovery patterns and outcomes in circumferential lumbar reconstructions based on surgical positioning: comparative analysis of single-position vs staged vs same day approaches

<h3>BACKGROUND CONTEXT</h3> Versatility in patient positioning during spine surgery has recently gained popularity. This includes single-position circumferential minimally invasive surgery, staged and same-day procedure. Overall analysis of outcomes between these approaches is lacking in the literature. <h3>PURPOSE</h3> To investigate the perioperative and postoperative outcomes of single-position, staged or same-day patients. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of a single-center database. <h3>PATIENT SAMPLE</h3> This study included 580 spine fusion patients. <h3>OUTCOME MEASURES</h3> Complications, health-related quality of life (HRQL) alignment. <h3>METHODS</h3> Operative spine patients with available baseline (BL) and up to 2-year (2Y) radiographic and HRQL data were included. Patients were stratified into three different categories based on surgical approach: single-position (SP), staged (ST), and same-day (SD). ANCOVA analysis was used to assess differences in demographic, radiographic, clinical, surgical factors and outcomes. <h3>RESULTS</h3> A total of 133 patients were included (age 57.8±11.4, BMI 30.6±7, 42% female, ASA 2.36±.57). Patients had an average of 2.42±1.3 levels fused, operative time was 293±141 minutes, EBL was 326±325, most common UIV was L3, and LIV was L5. Mean LOS was 5±4 days. Fifty-six patients were SP, 30 patients ST, and 47 were SD. SP patients were older on average (SP: 62, ST: 56, and SD: 55, <.05), had a lower BMI (SP: 29, S: 32, SD 32, p <.05) and lower mean ASA (SP: 2.2, ST: 2.5, SD: 2.5 p=.094). ST patients had a greater baseline T1PA (SP: 17.7, ST: 23.3, SD: 18.6, p=.11), with lower PI-LL (SP: 3.5, ST: .5, SD: 9.5, p=.06), PT (SP: 20.7, ST: 15.3, SD: 19.4, p=.03), and LL (SP: 55, ST: 56, SD: 48, p=.06). Prior fusion was more common among ST (SP: 29%, ST: 47%, SD 19% p=.033). ST patients had a lower number of levels fused (SP: 2.1, ST: 2.6, SD: 2.7, p=.037). ST patients had a greater amount of interbody fusions (SP: 1.53, ST: 2.3, SD: 1.9, p=.012). SD patients had a greater amount of osteotomies (SP: 14%, ST: 7%, SD: 74%, p <.001), corpectomies (SP: 2%, ST: 7%, SD: 41%, p <.001), and decompressions (SP: 57%, ST: 66%, SD: 100%, p <.001). SP patients had a lower operative time (SP: 386 min, ST: 652, SD: 498, p=.059), lower EBL (SP: 296 ml, ST: 498 ml, SD: 418 ml, p <0.001), and shorter LOS (SP: 4.53, ST: 8.15, SD: 5.71, p=.022). SD approach resulted in more patients going to rehab postoperatively (SP:7%, ST: 8%, SD: 29%, p=.030). SP patients had a lower NRS back score (SP: 3.2, ST: 4, SD: 6, p=.011), and lower NRS leg score (SP: 2.6, ST: 3.5, SD: 4.7, p=.118). Patients had a comparable postoperative T1PA, PI-LL, PT, and LL, with a comparable degree of correction. SP patients had a lower amount of pulmonary, GI/renal complications, and underwent fewer reoperations compared to ST and SD patients. <h3>CONCLUSIONS</h3> Although the SP alternative for circumferential lumbar reconstruction surgery has demonstrated good patient outcomes in the degenerative lumbar spondylosis population, few studies exist comparing outcomes of single position to those of more traditional dual positioning approaches. This study demonstrates that SP is associated with significant improvements in perioperative outcomes, reoperation rates, and pain scores when compared to both the staged and same-day manner of dual positioning with comparable degrees of correction. SP may prove to be a superior approach for certain degenerative spondylosis patients and warrants further studies to determine ideal patient candidacy and elucidate long-term outcomes. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Analysis of measures against mechanical complications in circumferential minimally invasive surgery for adult spinal deformity

Aim: We evaluated the reduction of mechanical complications (MCs) in circumferential minimally invasive spinal surgery (c-MIS) to treat adult spinal deformity (ASD) using lateral lumbar interbody fusion and a percutaneous pedicle screw. Methods: Patients with ASD who underwent c-MIS with a follow-up period of &gt; 24 months were enrolled. Groups were as follows: c-MIS using 5.5 mm rods (P group), c-MIS using a 5.5 mm single rod with cement augmentations in the upper instrumented vertebra (UIV)/UIV + 1 (B group), c-MIS using 6 mm rods (6P group), and multi-rod c-MIS (M group). Terminal rod contour was optimized to prevent proximal junctional kyphosis (PJK) in the P, 6P, and M groups. Patients were divided into an MC group, consisting of 68 patients with MCs, and a non-MC group, consisting of 78 patients without MCs. We examined various spinopelvic- and implant-related parameters between the groups. Results: Overall, 146 patients with ASD who underwent c-MIS were included. The incidence of PJK was significantly lower in the P and M groups than in the B group, and rod fracture was significantly lower in the M group than in the B and P groups. In the MC group, preoperative PT, postoperative PI-LL, and PSA were significantly larger than those in the non-MC group. Use of the 5.5 mm single rod and postoperative PI-LL were significant risk factors for MCs. Conclusion: The complication incidence decreased with improvements in surgical techniques and measures. Use of the 5.5 mm single rod and postoperative PI-LL were significant risk factors for MCs.

Chronological Evaluation of Gait Ability and Posture Balance after Adult Spinal Deformity Surgery

Adult spinal deformity (ASD) is highly prevalent in persons older than 65 years, affecting more than 30% of the total population. There are many important reports that describe excellent postoperative results for ASD surgery. However, there is no report that describes a chronological evaluation of gait ability and spinal balance after ASD surgery. The present prospective study aimed to determine the recovery time of gait and spinal balance ability after adult spinal deformity (ASD) surgery. Patients with ASD (n = 25: mean age, 73.0 years) who underwent corrective surgery and preoperative and postoperative gait and spinal balance ability evaluation. Spinal radiographs and gait analysis data (static balance; single-leg standing, dynamic balance; time-up and go test, gait ability; 10 m walk velocity) were acquired preoperatively, 1 month, 6 months, and 12 months after surgery. The radiographic parameters of the spine and pelvis (lumbar lordosis; LL, pelvic tilt; PT, sagittal vertical axis; SVA, pelvic incidence; PI) were measured. The mean postoperative SVA, LL, PT, and PI-LL became 30.0 mm, 50.1 degrees, 14.1 degrees, and 0.35 degrees, respectively. Preoperatively, all spinal balance and gait ability were worse than the normal threshold (one-leg standing; 14.2 s vs. 15.0 s, time-up and go test; 13.9 s vs. 13.5 s, 10-m walk speed; 0.91 m/s vs. 1.00 m/s). At 12 months after surgery, all spinal balance and gait ability became normal or improved (single-leg standing; 14.7 s, time-up and go test; 11.0 s, 10-m walk speed; 1.09 m/s). The ODI at one-year follow-up improved from 46.8 ± 12.6% to 27.8 ± 18.1%. In conclusion, gait and spinal balance analysis revealed that ASD patients could not recover gait and spinal balance ability one month after surgery. At 12 months after surgery, gait ability and dynamic spinal balance became better than preoperative levels. However, the static spinal balance was at the same level as that of preoperative status.

Two- and three-year outcomes of minimally invasive and hybrid correction of adult spinal deformity.

Previous studies have demonstrated the short-term radiographic and clinical benefits of circumferential minimally invasive surgery (cMIS) and hybrid (i.e., minimally invasive anterior or lateral interbody fusion with an open posterior approach) techniques to correct adult spinal deformity (ASD). However, it is not known if these benefits are maintained over longer periods of time. This study evaluated the 2- and 3-year outcomes of cMIS and hybrid correction of ASD. A multicenter database was retrospectively reviewed for patients undergoing cMIS or hybrid surgery for ASD. Patients were ≥ 18 years of age and had one of the following: maximum coronal Cobb angle (CC) ≥ 20°, sagittal vertical axis (SVA) > 5 cm, pelvic incidence-lumbar lordosis mismatch (PI-LL) ≥ 10°, or pelvic tilt (PT) > 20°. Radiographic parameters were evaluated at the latest follow-up. Clinical outcomes were compared at 2- and 3-year time points and adjusted for age, preoperative CC, levels operated, levels with interbody fusion, presence of L5-S1 anterior lumbar interbody fusion, and upper and lower instrumented vertebral level. Overall, 197 (108 cMIS, 89 hybrid) patients were included with 187 (99 cMIS, 88 hybrid) and 111 (60 cMIS, 51 hybrid) patients evaluated at 2 and 3 years, respectively. The mean (± SD) follow-up duration for cMIS (39.0 ± 13.3 months, range 22-74 months) and hybrid correction (39.9 ± 16.8 months, range 22-94 months) were similar for both cohorts. Hybrid procedures corrected the CC greater than the cMIS technique (adjusted p = 0.022). There were no significant differences in postoperative SVA, PI-LL, PT, and sacral slope (SS). At 2 years, cMIS had lower Oswestry Disability Index (ODI) scores (adjusted p < 0.001), greater ODI change as a percentage of baseline (adjusted p = 0.006), less visual analog scale (VAS) back pain (adjusted p = 0.006), and greater VAS back pain change as a percentage of baseline (adjusted p = 0.001) compared to hybrid techniques. These differences were no longer significant at 3 years. At 3 years, but not 2 years, VAS leg pain was lower for cMIS compared to hybrid techniques (adjusted p = 0.032). Those undergoing cMIS had fewer overall complications compared to hybrid techniques (adjusted p = 0.006), but a higher odds of pseudarthrosis (adjusted p = 0.039). In this review of a multicenter database for patients undergoing cMIS and hybrid surgery for ASD, hybrid procedures were associated with a greater CC improvement compared to cMIS techniques. cMIS was associated with superior ODI and back pain at 2 years, but this difference was no longer evident at 3 years. However, cMIS was associated with superior leg pain at 3 years. There were fewer complications following cMIS, with the exception of pseudarthrosis.

Risk Factors and Three Radiological Predictor Models for the Progression of Proximal Junctional Kyphosis in Adult Degenerative Scoliosis Following Posterior Corrective Surgery: 113 Cases With 2-years Minimum Follow-Up.

Retrospective cohort study. To identify risk factors and predictive models for proximal junctional kyphosis (PJK) in a long-term follow-up of patients with adult degenerative scoliosis (ADS) following posterior corrective surgeries. A consecutive 113 ADS patients undergoing posterior corrective surgery between January 2008 and April 2019 with minimum 2-year follow-up were included. All patients underwent preoperative, postoperative, and final follow-up by X-ray imaging. Multivariate logistic analysis was performed on various risk factors and radiological predictor models. PJK was identified radiographically in 46.9% of patients. Potential risk factors for PJK included postoperative thoracic kyphosis (TK) (P < .05), final follow-up Pelvic Tilt (PT) (P < .05), PT changes at final follow-up (P < .05), age over 55 years old at the surgery (P < .05), theoretical thoracic kyphosis-actual thoracic kyphosis mismatch (TK mismatch) (P < .05) and theoretical lumbar lordosis-acutal lumbar lordosis mismatch (LL mismatch) (P < .05). As for the predictive models, PJK was predictive by the following indicators: preoperative global sagittal alignment ≥45° (Model 1), postoperative pelvic incidence-lumbar lordosis mismatch (PI-LL)≤10° and postoperative PI-LL overcorrection (Model 2), and TK+LL≥0° (Model 3) (P < .05). Postoperative TK mismatch (OR = 1.064) was independent as risk factors for PJK, with the cut-off values respectively set at -28.56° to predict occurrence of PJK. The risk of radiographic PJK increases with an age over 55 years old and higher postoperative TK. In addition, postoperative TK mismatch is an independent risk factor for developing PJK. All three predictive models could effectively indicate the occurrence of PJK.

P141. Do age adjusted parameters influence patient reported outcomes after lumbar decompression?

<h3>BACKGROUND CONTEXT</h3> The impact of sagittal malalignment after lumbar fusion has been well described. However, few studies have examined the impact of sagittal alignment on outcomes after lumbar decompression. The existing literature has focused exclusively on normative measures of alignment (e.g., pelvic incidence lumbar lordosis mismatch [PI-LL] > 10) but has not considered age-adjusted alignment. <h3>PURPOSE</h3> To determine if age-adjusted sagittal malalignment (PI-LL or pelvic tilt [PT]), influences postoperative patient reported outcomes (PROs) after lumbar decompression surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of 62 patients who underwent lumbar decompression. <h3>PATIENT SAMPLE</h3> A total of 62 patients. <h3>OUTCOME MEASURES</h3> Oswestry disability index (ODI), Visual analog scale (VAS) Back, VAS leg <h3>METHODS</h3> Patients with >3 months follow-up who underwent one to four level lumbar decompression at a single institution were included. Patients were stratified into three groups based on achievement of age-adjusted thresholds in PI-LL and PT postoperatively. The first group included patients within the age-adjusted threshold ±10 years (MATCHED), and the other groups included those who were outside of the age-adjusted threshold ±10 years as over corrected (OVER), and under corrected (UNDER). The equations used to determine their age-adjusted sagittal parameters included: PT = [(Age-55)/3] + 20, and PI-LL = [(Age-55)/2] +3. Oswestry Disability Index (ODI), Visual Analog Scale (VAS) Back, and VAS Leg were evaluated. The percent of patients achieving MCID at final follow-up was calculated. <h3>RESULTS</h3> A total of 62 patients (mean 66 years, 50% female) were included with a mean follow-up of 368 days (range, 40 to 1,401). Groups for postoperative age-adjusted PI-LL included 12 MATCHED patients, 30 OVER patients and 20 UNDER patients. Groups for postoperative age-adjusted PT included 16 MATCHED patients, 27 OVER patients and 19 UNDER patients. For the entire cohort, there was a significant decrease in PI-LL (preop 8.7° vs postop 5.5°, p=0.001). There was no significant change in PT for the entire group (preop 22.5° vs postop 23.1°, p=0.39). There was no significant preoperative to postoperative PI-LL difference in the MATCHED (10.5° vs 7.9°, p=0.08) or UNDER patients (22.2° vs 19.3°, p=0.08), but PI-LL significantly decreased in the OVER group (preop -0.9°vs postop -4.7°, p=0.02). There were no significant differences in the preoperative to postoperative PT in the MATCHED (22.0° vs 22.8°, p=0.22), UNDER (28.4° vs 31.3°, p=0.11) or OVER groups (18.7° vs 17.5°, p=0.12). All groups exhibited significant improvements postoperatively for VAS Back, VAS Leg, and ODI scores (p<0.05). With respect to preoperative PROs, postoperative PROs and improvement in PROs, there was no difference between the MATCHED, UNDER or OVER groups. There were no significant differences between the groups in the percent that met MCID for ODI, VAS Back or VAS Leg scores. However, there was a trend towards increased PI-LL mismatch and increased ODI (p=0.09) and VAS-back scores (p=0.07). <h3>CONCLUSIONS</h3> Patients with postoperative age-adjusted spinopelvic abnormalities after lumbar decompression surgery had similar PROs when compared to patients without age-adjusted spinopelvic abnormalities. Therefore, isolated decompression is a viable treatment strategy in patients with sagittal malalignment. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.