Correction of proximal junctional failure using transforaminal thoracic interbody fusion: a technical note

P93. Semitendinosus ligament reinforcement for prevention of proximal junctional kyphosis and failure in adult spinal deformity

Retrospective cohort study. The purpose of the present study was to assess the impact of sarcopenia on the development of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following thoracolumbar spine fusion surgery using opportunistic evaluation of paraspinal fatty degeneration on preoperative magnetic resonance imaging. While paraspinal sarcopenia has been shown to have detrimental consequences following posterior cervicothoracic fusions, the impact of paraspinal sarcopenia on PJK and PJF following thoracolumbar spine fusion surgery remains unknown. We performed a retrospective review of patients who underwent posterior spine fusion surgery that extended caudally to the pelvis and terminated cranially between T10 and L2 between 2010 and 2017. The cohort was divided into three groups: (1) patients without PJK or PJF, (2) patients with PJK but no PJF, and (3) patients with PJF. Univariate and multivariate analyses were performed to determine risk factors for the development of proximal junctional complications. We identified 150 patients for inclusion in this study. Mean Hounsfield Units at the upper instrumented vertebra (UIV) was 148.3±34.5 in the cohort of patients without PJK or PJF, which was substantially higher than values recorded in the PJK (117.8±41.9) and PJF (118.8±41.8) subgroups (P<0.001). Severe multifidus sarcopenia was identified at a much higher rate in the subgroups of patients who developed PJK (76.0%) and PJF (78.9%) than in the subgroup of patients who developed neither PJK nor PJF (34.0%; P<0.001). Multivariate analysis demonstrated both low HU at the UIV and moderate-severe multifidus sarcopenia to be risk factors for the development of PJK and PJF. The results of this study suggest severe paraspinal sarcopenia and diminished bone density at the UIV impart an increased risk of developing PJK and PJF, while markers of systemic frailty such as modified Frailty Index and Charlson Comorbidity Index are not associated with an increased risk of these complications. III.

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) remain difficult problems following correction of adult spinal deformity (ASD). The goal of this study was to perform a comprehensive evaluation of risk factors associated with PJK and PJF using advanced statistical methods through inverse probability weighting (IPW). Patients who presented to the authors' institution with symptomatic ASD from 2013 to 2021 and who underwent thoracolumbar fusion ending in the pelvis were included in the study. The primary outcomes were development of PJK and PJF following ASD correction. PJK was classified using Glattes' criteria. PJF was defined as a proximal junctional angle > 20° from preoperative measures or complications at the upper instrumented vertebra (UIV) including vertebral body fracture, instability, and/or hardware failure. Patient charts and images (radiography, CT, and MRI) were used to extract demographics, measures of sagittal and coronal balance on pre- and postoperative radiography, operative techniques, and bone health metrics. Propensity score generation with IPW was used to control for confounding variables. In total, 187 patients were included in the study with a median follow-up of 24.6 months. Sixty-nine patients (36.9%) developed PJK, while 26 (13.9%) developed PJF. Kaplan-Meier analysis showed that both PJK and PJF largely occurred within the 1st year of index ASD correction. IPW showed that patients who developed PJK had a larger correction in the sagittal plane including global lumbar lordosis (p < 0.001) and sagittal vertical axis (p = 0.020). PJF development was associated with factors at the UIV including low Hounsfield units (p = 0.026) and cranially directed screws at the UIV (p = 0.040). PJK and PJF remain challenging postoperative complications following correction of ASD. In this large retrospective study that utilized IPW analysis, the authors found factors unique to each outcome. These results suggest that increased correction in the sagittal plane is more commonly associated with PJK, while junctional factors including bone quality and cranially directed screws at the UIV are associated with PJF. These findings can inform pre- and intraoperative medical and surgical strategies to reduce the incidence of PJK and PJF following ASD correction.

P106. Lower Hounsfield units and severe multifidus sarcopenia are independent predictors of increased risk for proximal junctional kyphosis and failure following thoracolumbar fusion

Proximal junction kyphosis (PJK) is a common imaging finding after long-level fusion, and proximal junctional failure (PJF) is an aggravated form of the progressive disease spectrum of PJK. This includes vertebral fracture of upper instrumented vertebra (UIV) or UIV+1, instability between UIV and UIV+1, neurological deterioration requiring surgery. Many studies have reported on PJK and PJF after long segment instrumentation for adult spinal deformity (ASD). In particular, for spine deformity surgeons, risk factors and prevention strategies of PJK and PJF are very important to minimize reoperation. Therefore, this review aims to help reduce the occurrence of PJK and PJF by updating the latest contents of PJK and PJF by 2023, focusing on the risk factors and prevention strategies of PJK and PJF. We conducted a search on multiple database for articles published until February 2023 using the search keywords "proximal junctional kyphosis," "proximal junctional failure," "proximal junctional disease," and "adult spinal deformity." Finally, 103 papers were included in this study. Numerous factors have been suggested as potential risks for the development of PJK and PJF, including a high body mass index, inadequate postoperative sagittal balance and overcorrection, advanced age, pelvic instrumentation, and osteoporosis. Recently, with the increasing elderly population, sarcopenia has been emphasized. The quality and quantity of muscle in the surgical site have been suggested as new risk factor. Therefore, spine surgeon should understand the pathophysiology of PJK and PJF, as well as individual risk factors, in order to develop appropriate prevention strategies for each patient.

Incidence of neurological deficits following proximal junctional kyphosis or failure in adult spinal deformity surgery: a systematic review and meta-analysis.

The effect of prophylactic vertebroplasty on the incidence of proximal junctional kyphosis and proximal junctional failure following posterior spinal fusion in adult spinal deformity: a 5-year follow-up study

One of the risks involved after long-segment fusions includes proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). There are reported modalities to help prevent this, including 2-level prophylactic vertebroplasty. In this study, our goal was to report the largest series of prophylactic cement augmentation with upper instrumented vertebra (UIV) + 1 vertebroplasty and a literature review. We retrospectively reviewed our long-segment fusions for adult spinal deformity from 2018 to 2022. The primary outcome measures included the incidence of PJK and PJF. Secondary outcomes included preoperative and postoperative Oswestry Disability Index, visual analog scale back and leg scores, surgical site infection, and plastic surgery closure assistance. In addition, we performed a literature review searching PubMed with a combination of the following words: "cement augmentation," "UIV + 1 vertebroplasty," "adjacent segment disease," and "prophylactic vertebroplasty." We found a total of 8 articles including 4 retrospective reviews, 2 prospective reviews, and 2 systematic reviews. The largest cohort of these articles included 39 patients with a PJK/PJF incidence of 28%/5%. Overall, we found 72 long-segment thoracolumbar fusion cases with prophylactic UIV cement augmentation with UIV + 1 vertebroplasty. The mean follow-up time was 17.25 months. Of these cases, 8 (11.1%) developed radiographic PJK and 3 (4.2%) required reoperation for PJF. Of the remaining 5 patients with radiographic PJK, 3 were clinically asymptomatic and treated conservatively and 2 had distal fractured rods that required only rod replacement. In this study, we report the largest series of patients with prophylactic percutaneous vertebroplasty and UIV cement augmentation with a low PJK and PJF incidence of 11.1% and 4.2%, respectively, compared with previously reported literature. Surgeons who regularly perform long-segment fusions for adult spinal deformity can consider this in their armamentarium when using methods to prevent adjacent segment disease because it is an effective modality in reducing early PJK and PJF that can often result in revision surgery.

The aim of this study was to analyze risk factors and avoidance techniques for proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in the upper thoracic spine with an emphasis on bone mineral density (BMD) as estimated by Hounsfield units (HU). A retrospective chart review identified patients at least 50 years of age who underwent instrumented fusion extending from the pelvis to an upper instrumented vertebra (UIV) between T1 and T6 and had a preoperative CT, pre- and postoperative radiographs, and a minimum follow-up of 12 months. HU were measured in the UIV, the vertebral body cephalad to the UIV (UIV+1), and the L3 and L4 vertebral bodies. Numerous perioperative variables were collected, including basic demographics, smoking and steroid use, preoperative osteoporosis treatment, multiple frailty indices, use of a proximal junctional tether, UIV soft landing, preoperative dual-energy x-ray absorptiometry, spinopelvic parameters, UIV screw tip distance to the superior endplate, UIV pedicle screw/pedicle diameter ratio, lumbar lordosis distribution, and postoperative spinopelvic parameters compared with age-adjusted normal values. Eighty-one patients were included in the study (21 men and 60 women) with a mean (SD) age of 66 years (6.9 years), BMI of 29 (5.5), and follow-up of 38 months (25 months). Spinal fusion constructs at the time of surgery extended from the pelvis to a UIV of T1 (5%), T2 (15%), T3 (25%), T4 (33%), T5 (21%), and T6 (1%). Twenty-seven patients (33%) developed PJK and/or PJF; 21 (26%) had PJK and 15 (19%) had PJF. Variables associated with PJK/PJF with p < 0.05 were included in the multivariable analysis, including HU at the UIV/UIV+1, HU at L3/L4, DXA femoral neck T-score, UIV screw tip distance to the superior endplate, UIV pedicle screw/pedicle diameter ratio, and postoperative lumbar lordosis distribution. Multivariable analysis (area under the curve = 0.77) demonstrated HU at the UIV/UIV+1 to be the only independent predictor of PJK and PJF with an OR of 0.96 (p = 0.005). Patients with < 147 HU (n = 27), 147-195 HU (n = 27), and > 195 HU (n = 27) at the UIV/UIV+1 had PJK/PJF rates of 59%, 33%, and 7%, respectively. In patients with upper thoracic-to-pelvis spinal reconstruction, lower HU at the UIV and UIV+1 were independently associated with PJK and PJF, with an optimal cutoff of 159 HU that maximizes sensitivity and specificity.

Systematic review of literature. To perform a comprehensive English language systematic literature review of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF), concentrating on incidence, risk factors, health related quality of life impact, prevention strategy, and classification systems. PJK and PJF are well described clinical pathologies and are a frequent cause of revision surgery. The development of a PJK classification that correlates with clinical outcomes and guides treatment decisions and possible prevention strategies would be of significant benefit to patients and surgeons. The phrases "proximal junctional," "proximal junctional kyphosis," and "proximal junctional failure" were used as search terms in PubMed for all years up to 2014 to identify all articles that included at least one of these terms. Fifty-three articles were identified overall. Eighteen articles assessed for risk factors. Eight studies specifically reviewed prevention strategies. There were no randomized prospective studies. There were 3 published studies that have attempted to classify PJK. The reported incidence of PJK ranged widely, from 5% to 46% in patients undergoing spinal instrumentation and fusion for adult spinal deformity. It is reported that 66% of PJK occurs within 3 months and 80% within 18 months after surgery. The reported revision rates due to PJK range from 13% to 55%. Modifiable and nonmodifiable risk factors for PJK have been characterized. PJK and PJF affect many patients after long segment instrumentation after the correction of adult spinal deformity. The epidemiology and risk factors for the disease are well defined. A PJK and PJF scoring system may help describe the severity of disease and guide the need for revision surgery. The development and prospective validation of a PJK classification system is important considering the prevalence of the problem and its clinical and economic impact. N/A.

Preliminary Results of the Effect of Prophylactic Vertebroplasty on the Incidence of Proximal Junctional Complications After Posterior Spinal Fusion to the Low Thoracic Spine

Systematic review and meta-analysis. To evaluate the impact of posterior ligamentous augmentation (PLA) on proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in adult spinal deformity (ASD) surgery. Adult spinal deformity (ASD) surgery is frequently complicated by PJK and PJF, with reported rates ranging from 17% to 61.7%. Techniques such as PLA, which involves spinous process or sublaminar tethering at the upper instrumented vertebra (UIV) +1 or +2, have been investigated as potential methods to mitigate these complications. A systematic literature review and meta-analysis was performed according to the PRISMA guidelines. Most studies defined PJK as an increase of ≥10° or ≥20° in the sagittal Cobb angle from UIV to UIV+2 compared with preoperative measurements. PJF was defined as PJK necessitating revision surgery. Eight comparative studies comprising 1333 patients (PLA: 579; no PLA: 754) were included. The mean age ranged from 55 to 68.6 years across studies, with a mean follow-up period of 17.6 to 31.2 months. There were no significant differences between the PLA and no PLA groups in terms of age (MD: 2.53; 95% CI: -0.28 to 5.34, I2 : 64.8%), BMI (MD: 1.03; 95% CI: -0.87 to 2.93, I2 : 69%), or sagittal vertical axis (SVA) preoperatively (MD: 3.92; 95% CI: -1.90 to 9.75, I2 : 73.1%) and postoperatively (MD: -1.54; 95% CI: -4.10 to 1.01, I2 : 56.2%). However, the PLA group demonstrated significantly lower odds of developing PJK compared with the no PLA group (PLA: 25.8%; no PLA: 28.8%; OR: 0.54; 95% CI: 0.34-0.85, I2 : 37.4%). Furthermore, PLA was associated with significantly lower odds of PJF (PLA: 3.3%; no PLA: 12.3%; OR: 0.23; 95% CI: 0.12-0.47, I2 : 17.9%). PLA in ASD surgery is associated with reduced odds of developing PJK and PJF over a follow-up period of 17.6 to 31.2 months.

182. Impact of realignment schemas on rates of proximal junctional changes in adult spinal deformity surgery

Mechanical complications after adult deformity surgery are typically considered as a composite variable. This study aims to differentiate their characteristics and analyze their behavioral patterns based on time-to-onset and predisposing factors. This retrospective observational study analyzed patients from a prospective multicenter database. Operated patients were analyzed for proximal junctional kyphosis (PJK), proximal junctional failure (PJF), pseudarthrosis (PA), rod breakage (RB), and no complications. Kaplan-Meier survival analysis and multivariate Cox regression models encompassing clinical, biological, radiographic, and surgical parameters were utilized to identify complication-related factors. Among 1,505 patients analyzed, 260 (17.3%) developed mechanical complications: PJK (65), PJF (43), PA (56), and RB (96). Similar time-to-event patterns were observed for PJK and PJF (Log-Rank test p = 0.446) (160days [Q1 = 72; Q3 = 492]), and PA and RB (Log-Rank test p = 0.782) (695days [Q1 = 371; Q3 = 1059]), clustering them in pairs. Proximal junctional problems (PJK/PJF) and failure of fusion (PA/RB) demonstrated different survival curves (Log-Rank test p < 0.001). Multivariate models associated (p < 0.05) proximal junctional problems with age (OR = 1.039), SF36-PCS (OR = 0.963), number of instrumented levels (OR = 1.123), and immediate postoperative alignment (Relative Lumbar Lordosis [OR = 1.025] and Relative Spinopelvic Alignment [OR = 1.064]). Failure of fusion occurrence was associated (p < 0.05) with number of instrumented levels (OR = 1.127) and 1-year postoperative: age (OR = 1.017), body mass index (OR = 1.044), SF36-PCS (OR = 0.975) and Relative Spinopelvic Alignment (OR = 1.034). Time-to-onset differed between proximal junctional problems and failure of fusion, and predisposing factors overlap. Nevertheless, the former was associated with immediate postoperative lumbar and global sagittal misalignment, the latter with mid-term biological factors and global sagittal misalignment.

Proximal junctional kyphosis (PJK) occurs commonly after surgery for adult spinal deformity. PJK exists on a spectrum, from a pure radiographic diagnosis to those patients with more severe deformity leading to notable pain, morbidity, and neurologic compromise requiring revision surgery-often described as proximal junctional failure (PJF). In this review, we describe the evaluation of patients with PJK and PJF, including different classification systems as well as modifiable and nonmodifiable risk factors. We then discuss the wide variety of strategies that have been proposed to reduce the risk of PJK and PJF. These include optimizing bone health with anabolic agents, use of bone cement at levels above the upper instrumented vertebra, optimizing alignment targets for correction, upper instrumented vertebra selection, posterior ligamentous complex preservation and augmentation, inducing a more gradual transition in stiffness above the construct, and instrumentation modifications. We end with a discussion of nonsurgical and surgical management of PJK, as well as our approach to revision surgery after PJF. Although a substantial increase in research on this topic has enhanced our understanding of proximal junction pathologies, notable work remains to demonstrate the reliability and reproducibility of prevention strategies.