Beyond Kyphosis: Modes of Failure at The Proximal Junction in Adult Spinal Deformity.

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.

P29. Caudally directed upper-instrumented vertebra pedicle screws minimize the risk of proximal junctional failure in patients with long posterior spinal fusion for adult spinal deformity

A retrospective review of large, multicenter adult spinal deformity (ASD) database. The aim of this study was to build a model based on baseline demographic, radiographic, and surgical factors that can predict clinically significant proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). PJF and PJK are significant complications and it remains unclear what are the specific drivers behind the development of either. There exists no predictive model that could potentially aid in the clinical decision making for adult patients undergoing deformity correction. Inclusion criteria: age ≥18 years, ASD, at least four levels fused. Variables included in the model were demographics, primary/revision, use of three-column osteotomy, upper-most instrumented vertebra (UIV)/lower-most instrumented vertebra (LIV) levels and UIV implant type (screw, hooks), number of levels fused, and baseline sagittal radiographs [pelvic tilt (PT), pelvic incidence and lumbar lordosis (PI-LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA)]. PJK was defined as an increase from baseline of proximal junctional angle ≥20° with concomitant deterioration of at least one SRS-Schwab sagittal modifier grade from 6 weeks postop. PJF was defined as requiring revision for PJK. An ensemble of decision trees were constructed using the C5.0 algorithm with five different bootstrapped models, and internally validated via a 70 : 30 data split for training and testing. Accuracy and the area under a receiver operator characteristic curve (AUC) were calculated. Five hundred ten patients were included, with 357 for model training and 153 as testing targets (PJF: 37, PJK: 102). The overall model accuracy was 86.3% with an AUC of 0.89 indicating a good model fit. The seven strongest (importance ≥0.95) predictors were age, LIV, pre-operative SVA, UIV implant type, UIV, pre-operative PT, and pre-operative PI-LL. A successful model (86% accuracy, 0.89 AUC) was built predicting either PJF or clinically significant PJK. This model can set the groundwork for preop point of care decision making, risk stratification, and need for prophylactic strategies for patients undergoing ASD surgery. 3.

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.

To investigate the cost-effectiveness and impact of prophylactic techniques on the development of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in the context of postoperative alignment. Adult spinal deformity patients with fusion to pelvis and 2-year data were included. Patients receiving PJK prophylaxis (hook, tether, cement, minimally-invasive surgery approach) were compared to those who did not. These cohorts were further stratified into "Matched" and "Unmatched" groups based on achievement of age-adjusted alignment criteria. Costs were calculated using the Diagnosis-Related Group costs accounting for PJK prophylaxis, postoperative complications, outpatient health care encounters, revisions, and medical-related readmissions. Quality-adjusted life years were calculated using Short Form-36 converted to Short-Form Six-Dimension (SF-6D) and used an annual 3% discount rate. Multivariate analysis controlling for age, sex, levels fused, and baseline deformity severity assessed outcomes of developing PJK/PJF if matched and/or with use of PJK prophylaxis. A total of 738 adult spinal deformity patients met inclusion criteria (age: 63.9 ± 9.9, body mass index: 28.5 ± 5.7, Charlson comorbidity index: 2.0 ± 1.7). Multivariate analysis revealed patients corrected to age-adjusted criteria postoperatively had lower rates of developing PJK or PJF (odds ratio [OR]: 0.4, [0.2-0.8]; P = .011) with the use of prophylaxis. Among those unmatched in T1 pelvic angle, pelvic incidence lumbar lordosis mismatch, and pelvic tilt, prophylaxis reduced the likelihood of developing PJK (OR: 0.5, [0.3-0.9]; P = .023) and PJF (OR: 0.1, [0.03-0.5]; P = .004). Analysis of covariance analysis revealed patients matched in age-adjusted alignment had better cost-utility at 2 years compared with those without prophylaxis ($361 539.25 vs $419 919.43; P < .001). Patients unmatched in age-adjusted criteria also generated better cost ($88 348.61 vs $101 318.07; P = .005) and cost-utility ($450 190.80 vs $564 108.86; P < .001) with use of prophylaxis. Despite additional surgical cost, the optimization of radiographic realignment in conjunction with prophylaxis of the proximal junction appeared to be a more cost-effective strategy, primarily because of the minimization of reoperations secondary to mechanical failure. Even among those not achieving optimal alignment, junctional prophylactic measures were shown to improve cost efficiency.

Surgery for adult spinal deformity (ASD) often involves long-segment posterior instrumentation that introduces stress at the proximal junction that can result in proximal junctional kyphosis (PJK) or proximal junctional failure (PJF). Recently, the use of tethers at the proximal junction has been proposed as a means of buffering the transitional stresses and reducing the risk of PJK/PJF. Our objectives are to summarize the clinical literature on proximal junctional tethers for PJK/PJF prophylaxis. Articles published between 1 January 2000 and 10 November 2022 were identified via a PubMed search using combinations of the search terms "spine surgery," "ASD," "complication," "surgery," "PJK," "PJF," "tether," "sublaminar band," and "prophylaxis." No restrictions were placed on the number of patients, surgical indications, or surgical procedures. Relevant articles were reviewed and summarized. Fifteen articles were identified, including 2 prospective cohorts (Level II), 10 retrospective cohorts (Level III), and 3 retrospective case series (Level IV). All studies were published between 2016 and 2022, and all focused on ASD patient populations. The mean age in each study ranged from 55 to 69 years, and most studies had a mean follow-up of at least 12 months (range, 5.5-45.4 months). Eleven studies used a polyethylene tether, 2 used soft sublaminar cables, and 2 used semitendinous allograft. The tether extended to the UIV+1 or UIV+2, passing either through or around the spinous processes, in 13 studies. In the remaining 2 studies, the tether was passed sublaminar at the UIV+1. Fourteen studies favored the use of tethers with regard to reduction of PJK/PJF rates, and one demonstrated similar rates of PJK between the tether and no-tether groups. PJK/PJF remain major challenges in ASD surgery. Most early studies suggest that the use of tethers for ligamentous augmentation may help to mitigate the development of PJK/PJF. However, the multifactorial etiology of PJK/PJF makes it unlikely that any single technique will solve this complex problem. Further study is needed to address not only the effectiveness of junctional tethers but also to clarify whether there are optimal tether configurations, tether materials, and tether tension. 3.

The purpose of this review is the current understanding of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following adult spinal deformity (ASD) surgery. We carried out a systematic search of PubMed for literatures published up to September 2017 with “proximal junctional kyphosis,” “proximal junctional failure,” and “adult spinal deformity” as search terms. A total of 98 literatures were searched. The 37 articles were included in this review. PJK is multifactorial in origin and likely results from variable risk factors. PJF is a progressive form of the PJK spectrum including bony fracture, subluxation between UIV and UIV+1, failure of fixation, neurological deficit, which may require revision surgery for proximal extension of fusion. Soft tissue protections, adequate selection of the UIV, prophylactic rib fixation, hybrid instrumentation such as hooks, vertebral cement augmentation at UIV and UIV+1, adequate selection material of rods and age-appropriate spinopelvic alignment goals are strategies to minimize PJK and PJF. The ability to perform aggressive global realignment of spinal deformities has also led to the discovery of new complications such as the PJK and PJF. Continuous research on PJK and PJF should be proceeded in order to comprehend the pathophysiology of these complications.

Background and Objectives: Proximal junctional kyphosis (PJK) remains a significant complication in adult spinal deformity (ASD) surgery, often resulting in severe clinical consequences. This study evaluates the effectiveness of the thoracolumbar junction (TLJ) distraction technique in reducing PJK incidence, with a focus on its potential to preserve sagittal alignment and mitigate mechanical stress at the proximal junction. Materials and Methods: This retrospective cohort study included 122 patients who underwent ASD surgery between February 2018 and June 2022. Patients were stratified into a control group and an intervention group based on the application of the TLJ distraction technique. Radiographic and clinical outcomes, including proximal junctional angle (PJA), thoracolumbar angle (TLA), and PJK incidence, were assessed one year postoperatively. Statistical analyses were performed using t-tests and chi-square tests. Results: The incidence of PJK was significantly lower in the intervention group compared with that in the control group (24.6% vs. 44.3%, p = 0.036). Additionally, the intervention group exhibited a significant reduction in postoperative TLA (−10.6° ± 6.3° vs. −6.8° ± 6.8°, p = 0.002) and ΔTLA (2.6° ± 9.0° vs. −2.4° ± 9.5°, p = 0.003). Although improvements in radiographic parameters were associated with a trend toward reduced rates of proximal junctional failure (PJF), statistical significance was not achieved. Conclusions: The TLJ distraction technique effectively reduces PJK incidence by optimizing thoracolumbar alignment and minimizing abrupt sagittal transitions. This simple and reproducible approach presents a promising strategy for mitigating proximal junctional complications in ASD surgery, warranting further validation in multicenter trials.

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.

Harnessing machine learning to predict and prevent proximal junctional kyphosis and failure in adult spinal deformity surgery: A systematic review.

CORR Synthesis: What Is the Evidence for Age-appropriate Alignment Goals in Surgery for Adult Spinal Deformity?

144. Prophylactic proximal junctional measures improves cost efficacy of adult spinal deformity surgery, with optimal cost utility seen in those with concurrent optimal realignment

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

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.

Introduction Proximal Junction Failure (PJF) and Proximal Junction Kyphosis (PJK) are significant complications. It remains unclear what are the specific drivers behind the development of either. This study attempts to develop a preoperative predictive model to identify patients at risk to develop PJF or PJK. Material and Methods Inclusion criteria: age ≥18, adult spinal deformity (ASD), ≥4 levels fused. Variables included in the model were: demographics, primary/revision, use of 3-column osteotomy, UIV/LIV levels and anchor (screw, hooks), number of levels fused, and baseline sagittal radiographs (PT, PI, PI-LL, TK, and SVA). PJF was defined as requiring revision for PJK and PJK was defined as an increase from baseline of PJK &gt; 20° and with deterioration by at least 1 SRS-Schwab sagittal modifier grade from 6wks postop. An ensemble of decision trees were constructed using the C5.0 algorithm with 5 different bootstrapped models, and internally validated via a 70:30 data split for training and testing. Accuracy and the area under a receiver operator characteristic curve (AUC) were calculated. Final model utilized 13 preoperative variables. Results 510 patients were included, with 357 for model training and 153 as testing targets (PJF: 37, PJK: 102). The overall model accuracy was 86.3% with an AUC of 0.89 indicating a good model fit. The 6 strongest (importance ≥0.95) predictors were (% target): age (&gt;64yrs, 41.4%), PI-LL (&gt;48.7deg, 35.6%), UIV (T10-L3, 35.1%), SVA (&gt;13.5cm, 32.5%), LIV (sacroiliac, 31.6%), and UIV Type (screws, 29.8%). If a patient met these criteria, they had a 66.7% chance of developing PJF or PJK with deterioration of sagittal alignment. Conclusion A successful model (86% accuracy, 0.89 AUC) was built predicting either PJF or clinically significant PJK. This model can set the groundwork for preoperative point of care decision making, risk stratification, and need for prophylactic strategies for patients undergoing ASD surgery.