Pelvic Kinematics during Gait Following Long-Segment Spinal Fusion Due to Adult Spinal Deformity: An Analysis Using a Smartphone-Based Inertial Measurement Unit

Introduction

Gait changes could occur after thoracic to pelvic long-segment corrective fusion surgery, a common procedure for adult spinal deformity (ASD), potentially affecting the occurrence and progression of postoperative hip osteoarthritis. We aimed to clarify postoperative pelvic kinematics in patients with ASD by performing gait analysis using a system based on a smartphone-integrated inertial measurement unit (IMU).

Methods

A total of 21 consecutive outpatients (73.6±4.6 years old, 2 men, 19 women) were enrolled. All had undergone long-segment fusion from the thoracic spine to the pelvis for ASD more than 1 year previously and could walk unassisted. A control group comprised 20 healthy volunteers. The IMU was fixed on the sacrum, and data were collected when subjects walked forward on a flat indoor floor. Acceleration in three axial directions and angular velocity around the three axes were recorded simultaneously during gait, and data were cut out for each gait cycle. Of 1043 features obtained, the top 20 features with the smallest p-value in a statistical comparison were selected. These features, plus gender and age, were classified using gradient boosting machine learning based on the decision tree algorithm. The classification accuracy and relative importance of the feature items were calculated.

Results

The accuracy rate for gait classification between groups was 96.7% and the F1-score was 0.968. The factor that contributed most to the classification of gait in both groups was "y-angular,_change_quantiles,_f_agg="var",_isabs=True,_qh=0.6,_ql=0.2," which means the variance of the change of the absolute value in the pelvic rotation angular velocity in the horizontal plane in the range of 20%-60% of the gait cycle. Its relative importance was 0.351, which was smaller in the group with fusion.

Conclusions

Patients with ASD following long-segment fusion from the thoracic spine to the pelvis apparently have a gait style characterized by suppressed pelvic rotation in the horizontal plane.

Long-term follow-up of non‑neurologic and neurologic complications after complex adult spinal deformity surgery: results from the Scoli-RISK-1 study

PURPOSE

To report all complications that occurred during the 2 to 5-year postoperative period, describe reoperations during this time period, and compare patients who did and did not have major, surgery-related complications and/or reoperations during this time period.

METHODS

The Scoli-RISK-1 study enrolled 272 ASD patients undergoing surgery from 15 centers. Inclusion criteria were Cobb angle of > 80°, corrective osteotomy for congenital/revision deformity, and/or 3-column osteotomy. At each follow-up visit, any neurologic or non-neurologic adverse event(AE) was documented & categorized.

RESULTS

77 patients had a minimum 5-year follow-up. 35 surgery-related AE's occurred during the 2 to 5-year period in 25(32.5%) patients. 23/35(65.7%) major, surgery-related complications occurred in 17 patients, 22/35(62.9%) requiring reoperations in 16 patients. Rod fracture and/or pseudarthrosis was the most common complication. The most common minor, surgery-related complication was asymptomatic rod fractures with no alignment changes. Four neurological complications were reported, one of which did not require reoperation. One death occurred at 6.1 years postoperative after multiple reoperations for mechanical complications. 14/17(82.4%) patients with major, surgery-related complication had a preceding AE during the initial 2-year postoperative period. 53 non-surgery-related AEs occurred in 21(27.3%) patients with musculoskeletal(37.7%) occurring most often. No differences were observed in ODI or SRS-22r in those with/without major surgery-related complications or those with/without reoperation.

CONCLUSION

During the study period, 25(32.5%) patients experienced 35 surgery-related complications, of which 23(65.7%) were major. Rod fracture with pseudarthrosis was the most common major, surgery-related complication. Neurologic complications were not found to be major drivers of reoperation. Surprisingly, PROs were similar in those with/without a major, surgery-related complication during the study period. This work has been presented as a podium presentation at the 55th Scoliosis Research Society annual meeting, Sep 9-13, 2020.

Analysis of factors related to patient satisfaction in adult spinal deformity with a minimum follow-up of 5 years

OBJECTIVE

Numerous studies have reported that corrective surgery improves postoperative health-related quality of life (HRQOL) in patients with adult spinal deformity (ASD), and postoperative HRQOL is maintained over 5-year follow-up. However, few studies have investigated factors associated with mid-term patient satisfaction. This study aimed to examine the factors contributing to 5-year patient satisfaction in patients with ASD following corrective surgery.

METHODS

This study included 51 patients who underwent corrective surgery and were followed up for > 5 years postoperatively. We investigated radiographic parameters and patient-reported outcomes using the Scoliosis Research Society 22r (SRS-22r) questionnaire and 36-item Short-Form Health Survey (SF-36) preoperatively and at two postoperative time points: two years (PO2Y) and five years (PO5Y). Spearman's rank correlation analysis was used to assess the relationship between patient satisfaction at PO5Y and both radiographic parameters and HRQOL scores at PO2Y and PO5Y. Correlation between patient satisfaction at PO5Y and improvement of both radiographic parameters and HRQOL scores were also assessed.

RESULTS

Patient satisfaction at PO5Y was significantly correlated with thoracic kyphosis, thoracolumbar kyphosis, and the distance between the C7-plumb line and the center of the sacral vertical line at PO2Y and PO5Y. Notably, the improvement of the function and social function domains of the SRS-22r and the SF-36, respectively, both at PO2Y and PO5Y, demonstrated a significantly weak correlation with patient satisfaction at PO5Y.

CONCLUSION

These findings underscore the significance of functional and social function improvements following corrective surgery, as they contribute to higher levels of satisfaction among patients with ASD.

Influence of implant density on mechanical complications in adult spinal deformity surgery

OBJECTIVE

The purpose was to analyze how rod characteristics, screw density and cages influence the incidence of mechanical complications compared to patient-related factors and alignment in adult spinal deformity instrumented T9-T11 to pelvis.

METHODS

Register data of 302 patients was analyzed. Relative lumbar lordosis (RLL) and relative sagittal alignment (RSA) was measured. Surgical data included rod characteristics, pedicle screw density and interbody cages. Univariate and multivariate logistic regression models were used.

RESULTS

Pseudarthrosis occurred in 24.1%. On univariate analysis Odds Ratio (OR) was 0.74 for ≥ 3 cages (p = 0.452), 0.48 for 4 rods (p = 0.008), 4.30 for high screw density (p = 0.001). Patient-related factors were non-significant. Multivariate OR was 0.59 for 4 rods (p = 0.084) and 4.67 for high screw density (p = 0.005). PJK/PJF occurred in 19.2%. Age > 60 had an OR 2.83 (p = 0.023), postoperative RSA malaligned OR 2.84 (p = 0.030), severely malaligned OR 6.54 (p < 0.001). Implant characteristics were non-significant. Multivariate OR was 1.26 for age > 60 (p = 0.657), 2.32 for malaligned RSA (p = 0.097), 5.69 for severely malaligned RSA (p = 0.001). Screw loosening occurred in 8.9%. Univariate OR was 0.95 for ≥ 3 cages (p = 0.920), 1.64 for 4 rods (p = 0.235), 0.25 for high screw density 1.5-2 (p = 0.011). Patient-related factors were non-significant. Multivariate OR for high screw density was 0.23 (p = 0.022).

CONCLUSION

Four rods decrease the pseudarthrosis risk. Cages have a secondary role. High screw density doesn't prevent from pseudarthrosis. Postoperative malalignment is the main PJK/PJF risk factor. Age plays a secondary role. Implant characteristics have a minor influence. High screw density constructs have a lower risk for screw loosening.

LEVEL OF EVIDENCE

3-Retrospective register study.

The Effect of Osteoporosis on Complications and Reoperation Rates After Surgical Management of Adult Thoracolumbar Spinal Deformity: A Systematic Review and Meta Analysis

STUDY DESIGN

Systematic Review.

OBJECTIVES

While substantial research has explored the impact of osteoporosis on patients undergoing adult spinal deformity (ASD) correction, the literature remains inconclusive. As such, the purpose of this study is to synthesize and analyze existing studies pertaining to osteoporosis as a predictor of postoperative outcomes in ASD surgery.

METHODS

We performed a systematic review and meta-analysis to determine the effect that a diagnosis of osteoporosis, based on ICD-10 coding, dual-energy X-ray absorptiometry (DEXA) or computed tomography, has on the incidence of adverse outcomes following surgical correction of ASD. Statistical analysis was performed using Comprehensive Meta-Analysis (Version 2) using a random effects model to account for heterogeneity between studies.

RESULTS

After application of inclusion and exclusion criteria, 36 and 28 articles were included in the systematic review and meta-analysis, respectively. The meta-analysis identified greater rates of screw loosening amongst osteoporotic patients (70.5% vs 31.9%, P = .009), and decreased bone mineral density in patients who developed proximal junctional kyphosis (PJK) (.69 vs .79 g/cm2, P = .001). The systematic review demonstrated significantly increased risk of any complication, reoperation, and proximal junctional failure (PJF) associated with reduced bone density. No statistical difference was observed between groups regarding fusion rates, readmission rates, and patient-reported and/or functional outcome scores.

CONCLUSION

This study demonstrates a higher incidence of screw loosening, PJK, and revision surgery amongst osteoporotic ASD patients. Future investigations should explore outcomes at various follow-up intervals in order to better characterize how risk changes with time and to tailor preoperative planning based on patient-specific characteristics.

Defining the Post-Operative Progression of Degenerative Scoliosis: An Analysis of Cases without Instrument Failure

OBJECTIVE

The expected post-operative changes in radiographic alignment over time remain poorly defined in patients surgically treated for degenerative scoliosis without instrument failure. Here we aim to describe the optimal natural progression of radiographic degenerative scoliosis at multiple timepoints in patients treated with a transforaminal lumbar interbody fusion (TLIF).

METHODS

We identified an initial retrospective cohort of 114 patients treated with a TLIF for degenerative scoliosis between 2018 and 2022, with 39 patients ultimately meeting the imaging inclusion criteria. Patients who completed a primary or revision procedure with no evidence of instrument failure, proximal junctional kyphosis, or proximal junctional failure at last follow-up were included. Radiographic measurements of spinopelvic alignment were manually extracted from X-Ray scoliosis films.

RESULTS

Thirty-nine patients (mean age 62.6 ± 8.7, mean follow-up 2.9 years), of which 23 underwent a primary TLIF (Primary) and 16 a revision procedure (Revision), were analyzed. Patients in the Primary group experienced a durable improvement in Thoracolumbar Cobb angle (-25° ± 15°), Thoracic Kyphosis (10° ± 13°), and Pelvic Incidence/lumbar lordosis mismatch (PI/LL) (-19° ± 19°) through the first year of follow-up. In the Revision group, at one year follow-up, all measures of spinopelvic alignment except PI/LL mismatch had reverted to pre-operative levels. Thoracolumbar Cobb angle decreased to a significantly greater degree in the Primary group compared to the Revision group.

CONCLUSION

Primary TLIF operations without instrument failure consistently improve radiographic outcomes in three key measures through the first year. For revision procedures, there appears to be modest radiographic benefit at follow-up.

Identifying Correlation Among Patient-Reported Outcome Measures: A Study of PROMIS-29, ODI, and VAS in Adult Spinal Deformity Patients

BACKGROUND

Adult spinal deformity (ASD) is becoming increasingly common in aging populations. Patient-reported outcome measures (PROMs) are self-reported patient surveys administered pre- and postoperatively that provide insight into patient improvement. We aim to compare 3 of the most utilized PROMs: PROMIS-29, Oswestry Disability Index (ODI), and Visual Analogue Scale (VAS), to investigate whether they provide unique and independent assessments of patient outcomes when assessed longitudinally.

METHODS

We retrospectively reviewed a database of ASD at UT Southwestern Medical Center between 2016 and 2021. Adult patients (>18 years old) were included if they underwent long-segment (>4 levels) thoracolumbar fusion. PROMIS-29, ODI, and VAS scores were collected preoperatively and at 3-, 6-, 12-, 18-, 24-, 30-, and 36-month follow-ups. Scores were recorded ±1 month of the time points. Pearson correlation coefficients for each PROM were then calculated in a pairwise fashion.

RESULTS

A total of 163 patients were included in our analysis. ODI and VAS showed significant covariance, with VAS Neck and VAS Back having Pearson coefficients of 0.95 and 0.94, respectively. ODI and PROMIS-29 also showed significant covariance, with Physical Function and ODI showing a Pearson coefficient of 0.95. PROMIS-29 and VAS demonstrated less correlation regarding Pain and Physical Function; however, they showed a significantly high Pearson coefficient when comparing VAS Back with PROMIS-29 Sleep and Pain Intensity (r = 0.97 and r = 0.96, respectively).

CONCLUSIONS

All 3 PROMs demonstrated significant correlation over 36 months, indicating that simultaneous administration of each during follow-up is redundant. The measure that provided the least unique information was ODI, as both VAS and PROMIS-29 demonstrated similar progression and assessed additional metrics. PROMIS-29 provided the same information as VAS and ODI, with extra facets of patient-reported outcomes, indicating that it may be a more comprehensive measure of longitudinal patient improvement.

Proximal and distal mechanical repercussions of instrumentation by double rods and interbody grafts in adult scoliosis

INTRODUCTION

Correction of adult scoliosis by instrumentation with double rods and interbody grafts aims to reduce the risk of pseudarthrosis with rod fracture. An increase in instrumentation rigidity can lead to an increase in stresses at the proximal and distal ends of the construct. The aim of this study was to analyze the incidence and clinical repercussions of proximal junctional kyphosis (PJK), proximal junctional failure (PJF) and iliac screw loosening.

MATERIEL AND METHODS

An analysis of patients operated on for adult scoliosis with instrumentation to the pelvis using 4 rods and interbody cages was carried out from a prospective register. The Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Scoliosis Research Society 22 (SRS-22) clinical scores and radiological parameters were collected preoperatively, postoperatively at 3 months, 1 year and 2 years. The appearance of PJK, PJF or distal screw loosening was sought; the clinical impact and the risk factors were analyzed by Bayesian inference.

RESULTS

Fifty-one patients with a mean age of 64.5 years were included. The clinical scores improved significantly (Pr>0.95) at 2 years: VAS back 6.9 versus 2.6, VAS leg 4.9 versus 2.5, ODI 48.2 versus 25.4, SRS-22 2.4 versus 3.5. The radiological parameters were corrected (Pr>0.95): Cobb angle 63.9° versus 22.8°, spinosacral angle (SSA) 112.4° versus 118.8°, T1-pelvic angle (TPA) 24, 8° versus 20.8°, lumbar lordosis 43.8° versus 51.0°, thoracic kyphosis 45.2° versus 53.6°. Thirteen patients (25.5%) presented with PJK and 11 (21.6%) with PJF. Seven patients (13.7%) presented with iliac screw loosening. None of these complications was associated with a significant deterioration in clinical scores. Cranial migration of the lumbar apex increased the risk of distal screw loosening: Odds-Ratio 10.31 (Pr>0.999). Two patients were re-operated on for PJF and one patient for iliac screw loosening (5.9%). No rod fracture with pseudarthrosis was found.

CONCLUSION

Instrumentation with double rods and interbody grafts was associated with a rate of 47.1% of mechanical repercussions at the extremity of the construct. However, these complications were not associated with a significant deterioration in clinical scores.

LEVEL OF EVIDENCE

III.

Long-Term Durability of Stand-Alone Lateral Lumbar Interbody Fusion

BACKGROUND

The long-term durability of stand-alone lateral lumbar interbody fusion (LLIF) remains unknown.

OBJECTIVE

To evaluate whether early patient-reported outcome measures after stand-alone LLIF are sustained on long-term follow-up.

METHODS

One hundred and twenty-six patients who underwent stand-alone LLIF between 2009 and 2017 were included in this study. Patient-reported outcome measures included the Oswestry Disability Index (ODI), EuroQOL-5D (EQ-5D), and visual analog score (VAS) scores. Durable outcomes were defined as scores showing a significant improvement between preoperative and 6-week scores without demonstrating any significant decline at future time points. A repeated measures analysis was conducted using generalized estimating equations (model) to assess the outcome across different postoperative time points, including 6 weeks, 1 year, 2 years, and 5 years.

RESULTS

ODI scores showed durable improvement at 5-year follow-up, with scores improving from 46.9 to 38.5 ( P = .001). Improvements in EQ-5D showed similar durability up to 5 years, improving from 0.48 to 0.65 ( P = .03). VAS scores also demonstrated significant improvements postoperatively that were durable at 2-year follow-up, improving from 7.0 to 4.6 ( P < .0001).

CONCLUSION

Patients undergoing stand-alone LLIF were found to have significant improvements in ODI and EQ-5D at 6-week follow-up that remained durable up to 5 years postoperatively. VAS scores were found to be significantly improved at 6 weeks and up to 2 years postoperatively but failed to reach significance at 5 years. These findings demonstrate that patients undergoing stand-alone LLIF show significant improvement in overall disability after surgery that remains durable at long-term follow-up.

A 5-year follow-up of the effect of corrective surgery in young adults with idiopathic scoliosis

PURPOSE

The purpose of this study was to determine mid-long-term outcomes (5 years) following surgery for young adult idiopathic scoliosis (YAdIS).

METHODS

This is a retrospective review of a prospective, multicenter adult deformity database including patients operated on idiopathic scoliosis by a single posterior approach, age at surgery between 19 and 29 (considered young adults), and 5-year follow-up. Demographic, radiographic and PROMS were analyzed preoperatively, at 2 years and at final follow-up.

RESULTS

Forty-two patients were included. Mean preoperative major curve angle was 59.65 ± 18.94. Main coronal curve initial correction was 56.38%, with 6% loss at 5 years. From baseline to 5 years after surgery, there was improvement in all PROMs (P < 0.004)-especially self-image-, except NRS-leg pain. This improvement was present at 6 months for all PROMs except for functional outcomes (SRS-Function and ODI) in which the improvement took place between 6 months and 2 years. In the 2- to 5-year follow-up period, no significant changes were seen in any PROMs. The percentage of patients reaching MCID from baseline at 5 years was: 75% for SRS-image, 45% for SRS-pain, 47.5% for SRS-function, 51.3% for SRS-mental, 42.5% for SRS-total and 15.4% for ODI. Patients reaching PASS at 5 years were: 88.1% for SRS-image, 81% for SRS-pain, 92.9% for SRS-function, 57.1% for SRS-mental, 88.1% for SRS-total, 92.7% for ODI and 69% for NRS pain. 11 minor and 4 major complications were identified.

CONCLUSION

YAdIS surgery resulted in an early and significant improvement in PROMs, especially for self-image, significantly reaching MCID and PASS thresholds. These results were maintained during long-term (5-year) follow-up.

Patient-Reported Outcomes After Complex Adult Spinal Deformity Surgery: 5-Year Results of the Scoli-Risk-1 Study

STUDY DESIGN

Prospective cohort.

OBJECTIVE

To prospectively evaluate PROs up to 5-years after complex ASD surgery.

METHODS

The Scoli-RISK-1 study enrolled 272 ASD patients undergoing surgery from 15 centers. Inclusion criteria was Cobb angle of >80°, corrective osteotomy for congenital or revision deformity, and/or 3-column osteotomy. The following PROs were measured prospectively at intervals up to 5-years postoperative: ODI, SF36-PCS/MCS, SRS-22, NRS back/leg. Among patients with 5-year follow-up, comparisons were made from both baseline and 2-years postoperative to 5-years postoperative. PROs were analyzed using mixed models for repeated measures.

RESULTS

Seventy-seven patients (28.3%) had 5-year follow-up data. Comparing baseline to 5-year data among these 77 patients, significant improvement was seen in all PROs: ODI (45.2 vs. 29.3, P < 0.001), SF36-PCS (31.5 vs. 38.8, P < 0.001), SF36-MCS (44.9 vs. 49.1, P = 0.009), SRS-22-total (2.78 vs. 3.61, P < 0.001), NRS-back pain (5.70 vs. 2.95, P < 0.001) and NRS leg pain (3.64 vs. 2.62, P = 0.017). In the 2 to 5-year follow-up period, no significant changes were seen in any PROs. The percentage of patients achieving MCID from baseline to 5-years were: ODI (62.0%) and the SRS-22r domains of function (70.4%), pain (63.0%), mental health (37.5%), self-image (60.3%), and total (60.3%). Surprisingly, mean values (P > 0.05) and proportion achieving MCID did not differ significantly in patients with major surgery-related complications compared to those without.

CONCLUSIONS

After complex ASD surgery, significant improvement in PROs were seen at 5-years postoperative in ODI, SF36-PCS/MCS, SRS-22r, and NRS-back/leg pain. No significant changes in PROs occurred during the 2 to 5-year postoperative period. Those with major surgery-related complications had similar PROs and proportion of patients achieving MCID as those without these complications.

Psychometric Evaluation and External Validity of the Japanese Version of Lumbar Stiffness Disability Index

Introduction

Long fusion surgery for adult spinal deformity may restrict activities of daily living due to lumbar stiffness. While the Lumbar Stiffness Disability Index (LSDI) can help assess lumbar stiffness, in Asia the external validity of this questionnaire has not been sufficiently examined. We performed the psychometric evaluation and external validation of the Japanese version of the LSDI (LSDI-J).

Methods

Fifty consecutive patients (14 males and 36 females; mean age 70.6 years) who underwent lumbar fusion surgery at our institution a minimum of one year after surgery and who visited the outpatient clinic between April and May 2019, were surveyed using the LSDI-J. The mean number of fusion levels was 4.4. Cronbach's alpha coefficients were calculated for internal consistency, and the intraclass correlation coefficient (ICC) was calculated to evaluate reliability. External validity was assessed by comparisons with the Oswestry Disability Index (ODI), the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), and the lumbar range of motion (LROM) with LSDI-J scores.

Results

Cronbach's alpha coefficient was 0.652 overall, and 0.849 after excluding Question 10 due to a low response rate. The ICC was 0.824 overall and 0.851 after excluding Question 10. The correlation with the ODI was 0.684, and the correlation coefficients with each domain of the JOABPEQ ranged from -0.590 to -0.413, indicating moderate correlation. However, LROM and the LSDI-J were not correlated (r=-0.055, P=0.734).

Conclusions

The LSDI-J may not be suitable in Japan because there was no correlation with LROM, the most important factor for external validity. It may be necessary to investigate why the LSDI-J did not apply to the Japanese population in terms of lower limb function. Alternatively, a unique method may be needed to assess lumbar stiffness disability that is more suitable for actual clinical practice in Japan.

Perioperative Predictive Factors for Positive Outcomes in Spine Fusion for Adult Deformity Correction

Purpose: Identifying perioperative factors that may influence the outcomes of long spine fusion for the treatment of adult deformity is key for tailored surgical planning and targeted informed consent. The aim of this study was to analyze the association between demographic or perioperative factors and clinical outcomes 2 years after long spine fusion for the treatment of adult deformity. Methods: This study is a multivariate analysis of retrospectively collected data. All patients who underwent long fusion of the lumbar spine for adult spinal deformity (January 2016–June 2019) were included. The outcomes of interest were the Oswestry disability index (ODI), visual analogic scale (VAS) preoperatively and at 1 and 2 years’ follow up, age, body mass index, American Society of Anaesthesiologists (ASA) score, upper and lowest instrumented vertebrae (UIV and LIV, respectively), length of surgery, estimated blood loss, and length of hospital stay. Results: Data from 192 patients were available. The ODI at 2 years correlated weakly to moderately with age (r = 0.4), BMI (r = 0.2), ASA (r = 0.3), and LIV (r = 0.2), and strongly with preoperative ODI (r = 0.6). The leg VAS at 2 years moderately correlated with age (r = 0.3) and BMI (r = 0.3). Conclusion: ODI and VAS at 2 years’ follow-up had no to little association to preoperative age, health status, LIV, or other peroperative data, but showed a strong correlation with preoperative ODI and pain level.

Analysis of factors associated with sagittal alignment deterioration after correction of degenerative scoliosis by in situ contouring

INTRODUCTION

In situ contouring is one of the surgical techniques used for scoliosis reduction. The initial correction could change over time, with deterioration of the sagittal balance. The purpose of this study was to analyze the loss of correction after degenerative lumbar scoliosis surgery using in situ contouring.

MATERIALS AND METHODS

Full spine radiographs of 73 patients (mean age 63.3 years, mean follow-up 27 months) were analyzed before surgery, after surgery, and at the final follow-up. The following radiographic parameters were measured: C2-C7 lordosis, T4-T12 kyphosis, L1-S1 lordosis, pelvic tilt, pelvic incidence, sacral slope, SVA C7, SVA C2, Cobb angle. Bayesian inference was used to compare the changes in these parameters. A probability>0.95 was considered as a significant change.

RESULTS

After surgery, lumbar lordosis increased from -28.4° to -37.8° (probability 0.999), then decreased to -32.1° at the final follow-up (probability 0.953). Thoracic kyphosis increased from 29.6° to 37.4° after surgery (probability 1.00) and continued to increase to 41.6° at the final follow-up (probability 0.999). SVA C7 increased from 38.5mm to 62.3mm (probability 0.999) and pelvic tilt from 19.4° to 25.1° (probability 1.00) during the follow-up period. Ten patients had to be reoperated because of a surgical site infection. Infection (14%) was associated with an increase of SVA C7 (probability 0.989) and thoracic kyphosis (probability 0.987). Nonunion (16%) was associated with a decrease in lumbar lordosis (probability 0.756).

CONCLUSION

Correction of degenerative lumbar scoliosis by in situ contouring resulted in sagittal balance correction; however, some of this correction was lost during the follow-up period. The main risk factors were deep wound infection and nonunion.

LEVEL OF EVIDENCE

IV, Retrospective study.

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

INTRODUCTION

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.

OBJECTIVE

To prospectively evaluate lower extremity motor function scores (LEMS) before and at 5 years after surgical correction of complex ASD.

DESIGN

Retrospective analysis of a prospective, multicenter, international observational study.

METHODS

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.

RESULTS

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 6 months, 9.5% at 2 years and 9.3% at 5 years postoperative. During the 2-5 year 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 5 years (p = 0.041).

CONCLUSIONS

In 77 patients undergoing complex ASD surgery with 5-year follow-up, while mean LEMS did not change from 2 to 5 years, 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 5 years postoperative. These results underscore the importance of long-term follow-up to 5 years, using individual motor scores rather than group averages, and comparing outcomes to both baseline and last follow-up.

Frailty Severity Impacts Development of Hospital-acquired Conditions in Patients Undergoing Corrective Surgery for Adult Spinal Deformity

STUDY DESIGN

This was a retrospective cohort study of a national dataset.

PURPOSE

The purpose of this study was to consider the influence of frailty on the development of hospital-acquired conditions (HACs) in adult spinal deformity (ASD).

SUMMARY OF BACKGROUND DATA

HACs frequently include reasonably preventable complications. Eleven events are identified as HACs by the Affordable Care Act. In the surgical ASD population, factors leading to HACs are important to identify to optimize health care.

METHODS

Patients 18 years and older undergoing corrective surgery for ASD identified in the American College of Surgeons' National Surgical Quality Improvement Program (ACS-NSQIP). The relationship between HACs and frailty as defined by the NSQIP modified 5-factor frailty index (mFI-5) were assessed using χ2 and independent sample t tests. The mFI-5 is assessed on a scale 0-1 [not frail (NF): <0.3, mildly frail (MF): 0.3-0.5, and severely frail (SF): > 0.5]. Binary logistic regression measured the relationship between frailty throughout HACs.

RESULTS

A total of 9143 ASD patients (59.1 y, 56% female, 29.3 kg/m2) were identified. Overall, 37.6% of procedures involved decompression and 100% fusion. Overall, 6.5% developed at least 1 HAC, the most common was urinary tract infection (2.62%), followed by venous thromboembolism (2.10%) and surgical site infection (1.88%). According to categorical mFI-5 frailty, 82.1% of patients were NF, 16% MF, and 1.9% SF. Invasiveness increased with mFI-5 severity groups but was not significant (NF: 3.98, MF: 4.14, SF: 4.45, P>0.05). Regression analysis of established factors including sex [odds ratio (OR): 1.22; 1.02-146; P=0.030], diabetes mellitus (OR: 0.70; 0.52-0.95; P=0.020), total operative time (OR: 1.01; 1.00-1.01; P<0.001), body mass index (OR: 1.02; 1.01-1.03; P=0.008), and frailty (OR: 8.44; 4.13-17.26; P<0.001), as significant predictors of HACs. Overall, increased categorical frailty severity individually predicted increased total length of stay (OR: 1.023; 1.015-1.030; P<0.001) and number of complications (OR: 1.201; 1.047-1.379; P=0.009).

CONCLUSIONS

For patients undergoing correction surgery for ASD, the incidence of HACs increased with worsening frailty score. Such findings suggest the importance of medical optimization before surgery for ASD.

How is staging of ALIF following posterior spinal arthrodesis to the pelvis related to functional improvement in patients with adult spinal deformity?

STUDY DESIGN

Retrospective cohort.

OBJECTIVES

To compare postoperative functional improvement in patients who underwent staged versus non-staged anterior-posterior spinal arthrodesis for adult spinal deformity (ASD). In patients with ASD, spinal arthrodesis can be performed in 2 stages to avoid the physiologic insult of a lengthy surgery. The association between staged surgery and postoperative functional improvement has not been well studied.

METHODS

We included 87 patients (59 women) with ASD who underwent anterior-posterior spinal arthrodesis of > 5 levels with fixation to the pelvis from 2010-2014. Primary outcomes were the frequency of achieving at least a minimal clinically important difference (MCID) in the Scoliosis Research Society-22r (SRS-22r) Activity domain and the timeframe in which it was achieved. The secondary outcome was patient satisfaction (SRS-22r Patient Satisfaction domain). A Cox proportional hazard model was used to compare functional improvement over time between staged and non-staged groups. Our study was powered to detect a relative hazard ratio of 0.53, β = 0.20. α = 0.05.

RESULTS

The frequency of achieving an MCID in SRS-22r Activity score did not differ significantly between the staged group (33/41 patients) and the non-staged group (34/46 patients) (hazard ratio 0.74; 95% confidence interval 0.41-1.36). Median times to achieving an MCID in SRS-22r Activity score were 191 days (interquartile range: 86-674) in the staged group and 181 days (interquartile range: 72-474) in the non-staged group (p = .75). The staged and non-staged groups had similar SRS-22r Patient Satisfaction scores at 3-9 months postoperatively and at final follow-up (both, p > .05).

CONCLUSION

Patients with ASD who underwent staged anterior-posterior spinal arthrodesis within 3 months after index surgery were similarly likely to experience functional improvement in the same timeframe as patients who underwent non-staged surgery. Patient satisfaction did not differ significantly between staged and non-staged groups.

LEVEL OF EVIDENCE

III.

Predictors and Correlative Factors for Low Back Pain after Long Fusion Arthrodesis in Patients with Adult Scoliosis

INTRODUCTION

Low back pain (LBP) still exists at the follow-up visit in some cases after long fusion arthrodesis for adult scoliosis. However, few available studies have elaborated the reasons and factors associated with this symptom. Therefore, the aim of the current study was to identify the correlative factors and predictors of postoperative LBP after long fusion arthrodesis and provide evidence to improve the surgical strategy.

METHODS

Seventy-nine patients with adult scoliosis who underwent long fusion arthrodesis were divided into a group with no or mild LBP (NLBP group) and one with moderate or severe LBP (MLBP group) according to the average Oswestry Dability Index (ODI) at the last follow-up visit. The Japanese Orthopaedic Association (JOA) score, ODI and complications were used to evaluate clinical outcomes. %Fat infltration area (%FIA), sagittal and coronal parameters were recorded to evaluate radiological outcomes. Multivariate logistic regression analysis was conducted to identify the predictors and correlative factors for postoperative LBP.

RESULTS

Thirty-three patients (41.77%) with ODI (30.06% ± 6.92%) higher than the average at the last follow-up were divided into the MLBP group, while the rest (58.23%) with last follow-up ODI (13.26% ± 5.31%) lower than the average were divided into the NLBP group. In multivariate logistic regression, the preoperative sagittal vertical axis (SVA) (P < 0.001), %FIA (P = 0.003) and osteoporosis (P = 0.016) were identified to be predictors and last follow-up SVA (P < 0.001), last follow-up lumbar lordosis (LL) (P = 0.031) and adjacent segment degeneration (ASD) (P = 0.043) were identified as correlative factors. The receiver-operating characteristic (ROC) curve showed satisfactory accuracy in preoperative SVA (P < 0.001) and %FIA (P < 0.001) to predict postoperative LBP.

CONCLUSION

Postoperative LBP after long fusion arthrodesis for adult scoliosis was common. Postoperative LBP was associated with increased SVA and decreased LL and ASD. Preoperative SVA > 3.54 cm, %FIA > 24.82% and osteoporosis showed good accuracy to predict the postoperative symptoms. Optimal surgical methods should be used for patients with these factors to decrease the incidence and degree of postoperative LBP.

Comparison of degenerative lumbar scoliosis correction and risk for mechanical failure using posterior 2-rod instrumentation versus 4-rod instrumentation and interbody fusion

PURPOSE

Four-rod instrumentation and interbody fusion may reduce mechanical complications in degenerative scoliosis surgery compared to 2-rod instrumentation. The purpose was to compare clinical results, sagittal alignment and mechanical complications with both techniques.

METHODS

Full spine radiographs were analysed in 97 patients instrumented to the pelvis: 58 2-rod constructs (2R) and 39 4-rod constructs (4R). Clinical scores (VAS, ODI, SRS-22, EQ-5D-3L) were assessed preoperatively, at 3 months, 1 year and last follow-up (average 4.2 years). Radiographic measurements were: thoracic kyphosis, lumbar lordosis, spinopelvic parameters, segmental lordosis distribution. The incidence of non-union and PJK were investigated.

RESULTS

All clinical scores improved significantly in both groups between preoperative and last follow-up. In the 2R-group, lumbar lordosis increased to 52.8° postoperatively and decreased to 47.0° at follow-up (p = 0.008). In the 4R-group, lumbar lordosis increased from 46.4 to 52.5° postoperatively and remained at 53.4° at follow-up. There were 8 (13.8%) PJK in the 2R-group versus 6 (15.4%) in the 4R-group, with a mismatch between lumbar apex and theoretic lumbar shape according to pelvic incidence. Non-union requiring revision surgery occurred on average at 26.9 months in 28 patients (48.3%) of the 2R-group. No rod fracture was diagnosed in the 4R-group.

CONCLUSION

Multi-level interbody fusion combined with 4-rod instrumentation decreased risk for non-union and revision surgery compared to select interbody fusion and 2-rod instrumentation. The role of additional rods on load sharing still needs to be determined when multiple cages are used. Despite revision surgery in the 2R group, final clinical outcomes were similar in both groups.

LEVEL OF EVIDENCE

III.

Outcomes of Same-Day Orthopedic Surgery: Are Spine Patients More Likely to Have Optimal Immediate Recovery From Outpatient Procedures?

BACKGROUND

Spinal surgery is associated with an inherently elevated risk profile, and thus far there has been limited discussion about how these outpatient spine patients are benefiting from these same-day procedures against other typical outpatient orthopedic surgeries.

METHODS

Orthopedic patients who received either inpatient or outpatient surgery were isolated in the American College of Surgeons National Surgical Quality of Improvement Program (2005-2016). Patients were stratified by type of orthopedic surgery received (spine, knee, ankle, shoulder, or hip). Mean comparisons and chi-squared tests assessed basic demographics. Perioperative complications were analyzed via regression analyses in regard to their principal inpatient or outpatient orthopedic surgery received.

RESULTS

This study included 729 480 surgical patients: 32.5% received spinal surgery, 36.5% knee, 24.1% hip, 4.9% shoulder, and 1.7%ankle. Of those who received a spinal procedure, 74.7% were inpatients (IN), and 25.3% were outpatients (OUT): knee: 96.1% IN, 3.9% OUT; hip:98.9% IN, 1.1% OUT; ankle: 29% IN, 71% OUT; and shoulder: 52.6% IN, 47.6% OUT. Hip patients were the oldest, and knee patients had the highest body mass index out of the orthopedic groups (P < .00). Spine IN patients experienced more complications than the other orthopedic groups and had the lowest OUT complications(both P < .05). This same trend of having higher IN complications than OUT complications was identified for hip, shoulder, and knee. However, ankle procedures had greater OUT procedure complications than IN (P < .05). After controlling for age, body mass index, and Charlson Comorbidity Index, IN procedures, such as knee, hip, spine, and shoulder, were significantly associated with experiencing postoperative complications. From 2006 to 2016, IN and OUT surgeries were significantly different among complications experienced for all of the orthopedic groups (P < .05) with complications decreasing for IN and OUT patients by 2016.

CONCLUSIONS

Over the past decade, spine surgery has decreased in complications for IN and OUT procedures along with IN/OUT knee, ankle, hip, and shoulder procedures, reflecting greater tolerance for risk in an outpatient setting.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

Despite the increase in riskier spine procedures, complications have decreased over the years. Surgeons should aim to continue to decrease inpatient spine complications to the level of other orthopedic surgeries.

Surgeon experience influences patient characteristics and outcomes in spine deformity surgery

PURPOSE

To characterize differences in patient demographics and outcomes by surgeon experience in a cohort of patients undergoing adult spinal deformity surgery.

METHODS

Patients undergoing degenerative spinal deformity were included. Patients whose surgeons graduated from fellowship ≤ 5 years prior to surgery versus > 5 years were compared. Multivariable linear and logistic regression, controlling for age, sex, comorbidity burden, number of segments fused, blood loss and operative time were used to evaluate differences in outcomes. Characteristics of operative invasiveness were plotted against surgeons' level of experience, and trends in these measures were assessed with univariate linear regression.

RESULTS

Three-hundred sixty-three patients were included. 147 patients' surgeons had ≤ 5 years of experience. Patient demographics were evenly matched. Patients with junior surgeons had more pre-existing medical complications, and senior surgeons were less likely to take care of patients with Medicare/Medicaid (p < 0.001). Junior surgeons were more likely to operate on non-elective patients (p < 0.001). Patients of junior surgeons received larger fusions (9.6 vs. 7.6 segments fused, p < 0.001). There were no differences in complication rates or death. Patients of junior surgeons had longer overall length of stays (p = 0.037) and higher rates of nonhome discharge (OR 2.0, p < 0.001), 30- and 90-day (p < 0.005) ED visits, and higher costs (+ $8548, 95% CI: $1596 to $15,502; p = 0.016).

CONCLUSION

Junior surgeons tend to perform more extensive deformity operations on more medically complex patients compared to senior surgeons, associated with higher costs and more resource utilization than senior surgeons.

Utilization of the American Society of Anesthesiologists (ASA) classification system in evaluating outcomes and costs following deformity spine procedures

PURPOSE

Adult spinal deformity (ASD) has increased prevalence in aging populations. Due to the high cost of surgery, studies have evaluated risk factors that predict readmissions and poor outcomes. The American Society of Anesthesiologists (ASA) classification system has been applied to patients with ASD to assess preoperative health and assess the correlation between ASA class and postoperative complications. This study evaluates the relationship between ASA and complications, length of stay (LOS), and direct costs following spine deformity surgery.

METHODS

Patients undergoing spine deformity surgery at a single institution from 2008-2016 were included and stratified based upon ASA status. Primary outcomes included patient demographics, adjusted LOS, and cost of care. Secondary measures compared between cohorts included adverse events, non-home discharge, and readmission rates.

RESULTS

442 patients with ASD were included in this study. Higher ASA class was correlated with greater Elixhauser Comorbidity Index (ECI) scores (p < 0.0001) and older age (p < 0.0001). Univariate analysis showed longer LOS (p < 0.0001) and greater direct costs in patients with higher ASA class (p < 0.0001). Patients in ASA Class III or IV had the greatest incidence of ICU stay when compared to patients without systemic disease (p < 0.0001). Upon multivariable regression analysis, high ASA class was associated with higher rates of non-home discharge (OR 5.0, 95% CI 3.1-8.1). Direct costs were greater for higher ASA class (regression estimate =  + $9,666, p = 0.002).

CONCLUSION

This study demonstrates that ASA class is correlated with a more complicated postoperative hospital course, greater rates of non-home discharge, total direct costs in spine deformity patients.

Predictive Model for Selection of Upper Treated Vertebra Using a Machine Learning Approach

OBJECTIVE

To train and validate an algorithm mimicking decision making of experienced surgeons regarding upper instrumented vertebra (UIV) selection in surgical correction of thoracolumbar adult spinal deformity.

METHODS

A retrospective review was conducted of patients with adult spinal deformity who underwent fusion of at least the lumbar spine (UIV > L1 to pelvis) during 2013-2018. Demographic and radiographic data were collected. The sample was stratified into 3 groups: training (70%), validation (15%) and performance testing (15%). Using a deep learning algorithm, a neural network model was trained to select between upper thoracic (T1-T6) and lower thoracic (T7-T12) UIV. Parameters used in the deep learning algorithm included demographics, coronal and sagittal preoperative alignment, and postoperative pelvic incidence-lumbar lordosis mismatch.

RESULTS

The study included 143 patients (mean age 63.3 ± 10.6 years, 81.8% women) with moderate to severe deformity (maximum Cobb angle: 43° ± 22°; T1 pelvic angle: 27° ± 14°; pelvic incidence-lumbar lordosis mismatch: 22° ± 21°). Patients underwent a significant change in lumbar alignment (Δpelvic incidence-lumbar lordosis mismatch: 21° ± 16°, P < 0.001); 35.0% had UIV in the upper thoracic region, and 65.0% had UIV in the lower thoracic region. At 1 year, revision rate was 11.9%, and rate of radiographic proximal junctional kyphosis was 29.4%. Neural network comprised 8 inputs, 10 hidden neurons, and 1 output (upper thoracic or lower thoracic). After training, results demonstrated an accuracy of 81.0%, precision of 87.5%, and recall of 87.5% on testing.

CONCLUSIONS

An artificial neural network successfully mimicked 2 lead surgeons' decision making in the selection of UIV for adult spinal deformity correction. Future models integrating surgical outcomes should be developed.

Robot-assisted orthopedic surgery in the treatment of adult degenerative scoliosis: a preliminary clinical report

Study design

A single-institution, retrospective cohort study.

Objective

To compare the accuracy and short-term clinical outcomes of pedicle screw placement between robot-assisted (RA) and freehand (FH) technique in the treatment of adult degenerative scoliosis (ADS).

Methods

From February 2018 to October 2019, 97 adult patients with degenerative scoliosis admitted to our department were retrospectively reviewed. Thirty-one patients received robot-assisted pedicle screw placement (RA group), and 66 patients underwent freehand pedicle screw placement (FH group). Patient demographics and short-term clinical outcomes were recorded and compared between two groups. Gertzbein-Robbins grading system was adopted to evaluate the accuracy of pedicle screw placement by means of postoperative CT scan. Short-term clinical outcomes consist of operative time, intraoperative blood loss, length of hospital stay (LOS), radiological parameters, Scoliosis Research Society-22 (SRS-22) scores before the operation, 6 months after operation, adverse events, and revisions.

Results

The accuracy of screw placement was higher than that of the FH group (clinically acceptable 98.7% vs. 92.2%; P< 0.001). Intraoperative blood loss of the RA group was less than those in the FH group (499 vs. 573 ml; P < 0.001). Operative time (283.1 vs. 291.9 min; P = 0.31) and length of stay (12.8 vs. 13.7 days; P = 0.36) were compared between RA and FH groups. In terms of radiological parameters, both of groups were improved postoperatively. The SRS-22 scores at 6 months after operation from both groups were better than those before operation. For surgery-related complication, one case had pressure sores in the RA group while two cases developed dural tears in the FH group. No revision was required in both groups.

Conclusion

Combined with other surgical correction modalities, robot-assisted pedicle screw fixation is an effective and safe method of treating degenerative scoliosis. Due to its satisfactory surgical outcomes such as higher accuracy and less trauma, it provides a good alternative for clinical practice.

Level of evidence

3.

Obesity negatively affects cost efficiency and outcomes following adult spinal deformity surgery

BACKGROUND CONTEXT

Obesity has risen to epidemic proportions within the United States. As the rates of obesity have increased, so has its prevalence among patients undergoing adult spinal deformity (ASD) surgery. The effect of obesity on the cost efficiency of corrective procedures for ASD has not been effectively evaluated.

PURPOSE

To investigate differences in cost efficiency of ASD surgery for patients stratified by body mass index (BMI).

STUDY DESIGN/SETTING

Retrospective review of a single-center ASD database.

PATIENT SAMPLE

Five hundred five ASD patients.

OUTCOME MEASURES

Complications, revisions, costs, EuroQol-5D (EQ5D), quality-adjusted life years (QALYs), cost per QALY.

METHODS

ASD patients (scoliosis≥20°, SVA≥5 cm, PT≥25°, or TK ≥60°) ≥18, undergoing ≥4 level fusions were included. Patients were stratified into NIH-defined obesity groups based on their preoperative BMI: underweight 18.5< (U), normal 18.5 to 24.9 (N), overweight 25.0 to 29.9 (O), obese I 30.0 to 34.9 (OI), obese II 35.0 to 39.9 (OII), and obesity class III 40.0+ (OIII). Total surgery costs for each ASD obesity group were calculated. Costs were calculated using the PearlDiver database, which reflects both private insurance and Medicare reimbursement claims. Overall complications and major complications were assessed according to CMS definitions. QALYs and cost per QALY for obesity groups were calculated using an annual 3% discount up to life expectancy (78.7 years).

RESULTS

In all, 505 patients met inclusion criteria. Baseline demographics and surgical details were: age 60.8±14.8, 67.6% female, BMI 28.8±7.30, 81.0% posterior approach, 18% combined approach, 10.1±4.2 levels fused, op time 441.2±146.1 minutes, EBL 1903.8±1594.7 cc, and LOS 8.7±10.7 days. There were 17 U, 154 N patients, 151 O patients, 100 OI, 51 OII, and 32 OIII patients. Revision rates by obesity group were: 0% U, 3% N patients, 3% O patients, 5% OI, 4% OII, and 6% for OIII patients. The total surgery costs by obesity group were: $48,757.86 U, $49,688.52 N, $47,219.93 O, $50,467.66 OI, $51,189.47 OII, and $53,855.79 OIII. In an analysis of patients with baseline and 1 Y EQ5D follow-up, the cost per QALY by obesity group was: $153,737.78 U, $229,222.37 N, $290,361.68 O, $493,588.47 OI, $327,876.21 OII, and $171,680.00 OIII. If that benefit was sustained to life expectancy, the cost per QALY was $8,588.70 U, $12,805.72 N, $16,221.32 O, $27,574.77 OI, $18,317.11 OII, and $9,591.06 for OIII.

CONCLUSIONS

Among adult spinal deformity patients, those with BMIs in the obesity I, obesity II, or obesity class III range had more expensive total surgery costs. When assessing 1 year cost per QALY, obese patients had costs 32% higher than nonobese patients ($224,440.61 vs. $331,048.23). Further research is warranted on the utility of optimizing modifiable preoperative health factors for patients undergoing corrective adult spinal deformity surgery.

Scoliosis surgery in adulthood: what challenges for what outcome?

Adolescent idiopathic scoliosis that has progressed over time, de novo scoliosis, and degenerative scoliosis represent different types of adult spinal deformity (ASD). Functional impairment and muscular fatigue are due to sagittal and coronal imbalance of the trunk. Surgical treatment can provide a significant improvement of three-dimensional (3D) thoracolumbar alignment, function, and health-related quality of life (QoL). A patient-specific benefit-risk assessment, including clinical expectations, comorbidities, and the spinal deformity itself, has to be done preoperatively since the risk for mechanical complications is relatively high. Minimal invasive techniques combine posterior percutaneous instrumentation and lateral interbody fusion cages which enables vertebral realignment and indirect foraminal stenosis decompression. This strategy seems appropriate in mild and moderate ASD with a limited number of degenerated segments in the lumbar spine and remaining curve flexibility. Severe ASD needs to be addressed by open surgery, which combines posterior instrumentation, interbody fusion, and osteotomies in stiff deformities. Longer posterior instrumentation of the thoracolumbar spine, the sacrum, and the pelvis carries a risk for mechanical complications such as non-union and proximal junctional kyphosis (PJK). Modern surgical techniques including circumferential lumbosacral fusion and double rods might lower the risk for non-union. Accurate sagittal alignment planning, setting the lumbar sagittal apex according to pelvic incidence, and segmental lordosis distribution, are mandatory for minimizing the risk of PJK.