Objective To determine the role of dynamic hip joint coverage in maintaining postoperative sagittal balance in adult spinal deformity (ASD) patients following S2-alar-iliac (S2AI) fixation.
Methods A total of 224 ASD patients who underwent S2AI fixation were enrolled. Patients were stratified into 2 groups based on pre-to-post (from preoperative to postoperative) changes in femoral head coverage (ΔFHC): change group (group C) and noncoverage change group (group NC). Group C was further subdivided according to FHC recovery during follow-up into rebound (group C-R) and nonrebound (group C-NR) groups. Clinical outcomes and radiographic parameters of hip and spinopelvic alignment were assessed preoperatively, at the initial postoperative standing, and at the 2-year follow-up.
Results Compared to group C, patients in group NC demonstrated a higher incidence of sagittal imbalance-related mechanical complications at 2-year follow-up, with a greater tendency for sagittal imbalance progression (p=0.013), a larger post-to-follow-up change in sagittal vertical axis (ΔSVA) (p=0.029), and a higher incidence of proximal junctional kyphosis (PJK) (p=0.031). Although there was no significant difference in PJK incidence between group C-NR and group C-R (p=0.845), group C-NR showed a greater tendency for postoperative sagittal imbalance aggravation (p=0.025), with a significantly larger ΔSVA during follow-up (p=0.002). The optimal cutoff values for predicting postoperative sagittal imbalance aggravation were 3.5% for pre-to-post ΔFHC (area under the curve [AUC]=0.694) and 1.8% for post-to-follow-up ΔFHC (AUC=0.713).
Conclusion Dynamic postoperative changes in hip joint coverage, characterized by the FHC, are associated with postoperative sagittal balance maintenance. Patients with limited pre-to-post and post-to-follow-up changes in the FHC demonstrate compromised hip joint compensatory capacity, thereby increasing the risk of postoperative sagittal imbalance-related mechanical complications.
Objective To compare perioperative and complication outcomes, focusing on the prevention of sagittal translation (ST), between a novel “prioritized correction with multiple-rod construct” (PC-MRC) technique and traditional multiple-rod constructs (M-RC) in adult spinal deformity (ASD) patients undergoing 3-column osteotomies (3-COs).
Methods In this retrospective study, 101 ASD patients with a minimum 2-year follow-up after 3-COs were divided into 2 groups: PC-MRC (n=65) and M-RC (n=36). The PC-MRC technique involved initial osteotomy closure with short rods followed by global alignment correction with long rods. Radiographic and clinical parameters were assessed preoperatively, postoperatively, and at final follow-up.
Results The PC-MRC group had significantly shorter operation time and lower estimated blood loss (p=0.045 and p=0.007, respectively). Major coronal and kyphotic deformity correction rates were similar between groups. No significant correction loss occurred at the final follow-up. Crucially, the incidence of ST was significantly lower in the PC-MRC group (1.5% vs. 25.0%, p<0.001). Correspondingly, the overall rate of neurological injury was lower in the PC-MRC group (7.7% vs. 22.2%, p=0.037).
Conclusion The PC-MRC technique offers a versatile and rigid fixation for 3-COs in ASD patients, facilitating significant correction of global deformity. This straightforward technique effectively prevents massive blood loss and ST caused by 3-COs, while minimizing the risk of neurological complication.
Objective Contact casting with plaster bandages is a standard technique for thoraco-lumbo-sacral orthosis (TLSO) fabrication. However, this hands-on process depends on the operator’s skill as well as requires a close physical contact, involving potential risks of coronavirus and influenza virus infection and the patient’s personal space violation. Recently, noncontact, highly accurate molding technology using 3-dimensional (3D) digital scanning has been developed. Although 3D scanning is widely applied for limb orthosis, its spinal application mainly focuses on pediatric scoliosis. Comparative studies across diverse body types remain limited. Therefore, this study aimed to clarify the adaptability, accuracy, and fabrication time of TLSO produced using noncontact 3D digital scanning, comparing with conventional contact plaster-bandage casting.
Methods TLSO was fabricated using both contact and noncontact techniques for mannequins with 4 different body types. High-precision scanner and computed tomography (CT) were used to assess the shape reproducibility by quantifying the gap area between the orthosis and mannequin. In addition, total fabrication time was compared between the 2 techniques.
Results High-precision scanner identified that 3D scanning showed a higher shape reproducibility than conventional casting, particularly in curvilinear areas (all p<0.001). In CT measurement, 3D scanning demonstrated a smaller gap area in all the body types (all p<0.001). Fabrication time was also shorter during 3D scanning (54.9±0.9 minutes) than during conventional casting (100.0±5.5 minutes) (p<0.001).
Conclusion Noncontact 3D digital scanning facilitates a rapid, accurate, and reproducible TLSO fabrication across diverse body types, providing a safer and more efficient alternative to conventional contact plaster-bandage casting.
Objective To determine the optimal targets of the L1 pelvic angle (L1PA) that minimize the risk of both proximal junctional kyphosis (PJK) and pelvic nonresponse (PNR) following adult spinal deformity (ASD) surgery.
Methods A retrospective study was conducted on 323 patients who underwent fusion surgery from the low thoracic spine (T9–12) to the pelvis and were followed up for 2 years. Risk factors for PJK and PNR were evaluated separately using multivariate logistic regression analysis. Receiver operating characteristic (ROC) curve analyses were performed to identify L1PA cutoff values predictive of PJK and PNR across 3 pelvic incidence (PI) categories: <45°, 45°–60°, and ≥60°. L1PA thresholds were defined to delineate “ideal” alignment.
Results Risk factor analyses revealed that low L1PA was an independent risk factor for PJK (odds ratio [OR], 0.927; p=0.019), while high PI–LL (OR, 1.101; p<0.001) and high L1PA (OR, 1.249; p<0.001) were significant risk factors for PNR. On ROC curve analyses, optimal L1PA ranges were 2.5°–4.5° for PI<45°, 8.7°–12.6° for PI 45°–60°, and 15.1°–17.3° for PI≥60°. Patients within these ideal L1PA ranges had significantly lower rates of both PJK and PNR compared to those exceeding ideal L1PA ranges.
Conclusion This study demonstrated that optimal correction based on these L1PA targets reduced the risk of both PJK and PNR. Therefore, these L1PA targets can serve as reliable alignment goals to optimize surgical outcomes in ASD surgery.
Objective Spinal fusion surgery is effective for treating various adult spinal deformities. However, spinal fusion surgery is associated with the risk of adjacent segment disease (ASD; 5%–30%), particularly proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Proximal junctional tethering (PJT) has become a popular technique owing to increasing evidence that it can decrease the rate of PJK or PJF.
Methods A literature search was conducted using PubMed, Embase, and Cochrane Library. Twelve eligible studies were identified. These studies were predominantly retrospective in nature and compared the incidence of PJK or PJF in adults undergoing spinal fusion surgery with or without PJT. Risk of bias was assessed using the Newcastle-Ottawa scale. All outcomes were analyzed using R software (ver. 4.4.1).
Results We included 8 retrospective cohort studies and 3 propensity-score-matched analyses; these studies comprised 1,424 patients. PJT was associated with a significant decrease in the odds of development of PJK (odds ratio [OR], 0.44; 95% confidence interval [CI], 0.27–0.71) and PJF (OR, 0.36; 95% CI, 0.19–0.69) compared with control. Subgroup analysis results revealed no significant difference in ASD rates between geographical locations, between tethering with and without crosslinks, and between specific tethering techniques.
Conclusion PJT significantly reduces the odds of both PJK and PJF in adults undergoing spinal fusion surgery.
Objective We aimed to investigate the incidence of delayed-onset neurological deficits (DONDs), DOND-related reoperation rates following adult spinal deformity (ASD) surgery, and efficacy of transverse process hooks (TPHs) at the uppermost instrumented vertebra (UIV) compared to pedicle screws (PSs).
Methods We included 90 consecutive patients who underwent instrumented fusion from the sacrum to the distal thoracic spine for ASD, with a minimum follow-up of 24 months. Clinical and radiological outcomes were compared between 33 patients in the TPH group and 57 patients in the PS group, using the Scoliosis Research Society-22 Outcomes questionnaire (SRS-22), Medical Outcomes Study Questionnaire Short-Form 36 (SF-36), and various spinal sagittal parameters.
Results While absent in the TPH group, myelopathy occurred in 15.8% of the PS group, wherein 15 patients underwent reoperation. The change in the proximal junctional angle, from the pre- to postoperative assessment, was lower in the TPH group than in the PS group (0.2 vs. 6.6, p=0.002). Postoperative facet degeneration in the PS group progressed more significantly than in the TPH group (0.5 vs. 0.1, p=0.002). Surgical outcomes were comparable for both groups, except for the back visual analogue scale (3.5 vs. 4.1, p=0.010) and SRS-22 domains, including pain and satisfaction (3.3 vs. 2.9, p=0.033; 3.7 vs. 3.3, p=0.041). No intergroup difference was observed in SF-36.
Conclusion Using TPHs at the UIV level can prevent DOND, and thereby prevent postoperative myelopathy that necessitates reoperation; thus, TPHs is preferable over PSs in ASD surgery.
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Objective To identify the risk factors for proximal junctional failure (PJF) after adult spinal deformity (ASD) surgery despite ideal sagittal correction according to age-adjusted alignment target.
Methods The study included patients who underwent low thoracic to pelvic fusion for ASD and obtained ideal correction according to age-adjusted pelvic incidence minus lumbar lordosis. PJF was defined either radiographically as a proximal junctional angle (PJA) of >28° plus a difference in PJA of >22° or clinically as revision surgery for proximal junctional complications. Clinical and radiographic variables were assessed to identify the risk factors for PJF.
Results The final study cohort consisted of 196 patients, of whom 170 were women (86.7%), with an average age of 68.3 years. During mean follow-up duration of 45.9 months, PJF occurred in 43 patients (21.9%). Multivariate logistic regression analysis revealed that old age (odds ratio [OR], 1.063; 95% confidence interval [CI], 1.001–1.129; p=0.046), large preoperative sagittal vertical axis (OR, 1.007; 95% CI, 1.001–1.013; p=0.024), nonuse of a transverse process (TP) hook (OR, 5.556; 95% CI, 1.205–19.621; p=0.028), and high lumbar distribution index (LDI) (OR, 1.136; 95% CI, 1.109–1.164; p<0.001) were significant risk factors for PJF development.
Conclusion A sizeable proportion of patients (21.9%) developed PJF despite achieving ideal sagittal correction. Using TP hooks with avoiding excessive LDI can be helpful to further mitigate the risk of PJF development in this patient group.
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Objective To identify risk factors and establish radiographic criteria for distal junctional failure (DJF) in patients with adult spinal deformity (ASD), who underwent fusion surgery stopping at L5.
Methods This retrospective study was undertaken from January 2016 to December 2020. Patients with ASD who underwent fusion surgery (≥5 levels) stopping at L5 were analyzed. DJF was defined as symptomatic adjacent segment pathology at the lumbosacral junction necessitating consideration for revision surgery. Demographic data and radiographic measurements were compared between the DJF and non-DJF groups. Receiver operating characteristic curve analysis was performed to identify the radiographic cutoff value for DJF.
Results Among 76 patients, 16 (21.1%) experienced DJF. DJF was associated with older age, antidepressant/anxiolytic medication, longer level of fusions, and worse preoperative sagittal alignment. Antidepressant/anxiolytic medication (odds ratio, 5.60) and preoperative pelvic incidence (PI)–lumbar lordosis (LL) mismatch>40° (odds ratio, 5.87) were independent risk factors for DJF. Without both factors, the incidence of DJF has been greatly reduced (9.1%). Two radiographic criteria were determined for DJF: last distal junctional angle (DJA)>-5° and Δ last DJA–post DJA>5°. When both criteria were met, the sensitivity and specificity of the DJF were 93.3% and 91.7%, respectively.
Conclusion Use of antidepressant/anxiolytic medication and preoperative PI–LL mismatch >40° were independent risk factors for DJF. DJF could be diagnosed using postoperative changes in the DJA. If both criteria were met, DJF could be strongly suggested.
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Objective To determine the clinical impact of the baseline sagittal imbalance severity in patients with adult spinal deformity (ASD).
Methods We retrospectively reviewed patients who underwent ≥ 5-level fusion including the pelvis, for ASD with a ≥ 2-year follow-up. Using the Scoliosis Research Society-Schwab classification system, patients were classified into 3 groups according to the severity of the preoperative sagittal imbalance: mild, moderate, and severe. Postoperative clinical and radiographic results were compared among the 3 groups.
Results A total of 259 patients were finally included. There were 42, 62, and 155 patients in the mild, moderate, and severe groups, respectively. The perioperative surgical burden was greatest in the severe group. Postoperatively, this group also showed the largest pelvic incidence minus lumbar lordosis mismatch, suggesting a tendency towards undercorrection. No statistically significant differences were observed in proximal junctional kyphosis, proximal junctional failure, or rod fractures among the groups. Visual analogue scale for back pain and Scoliosis Research Society-22 scores were similar across groups. However, severe group’s last follow-up Oswestry Disability Index (ODI) scores significantly lower than those of the severe group.
Conclusion Patients with severe sagittal imbalance were treated with more invasive surgical methods along with increased the perioperative surgical burden. All patients exhibited significant radiological and clinical improvements after surgery. However, regarding ODI, the severe group demonstrated slightly worse clinical outcomes than the other groups, probably due to relatively higher proportion of undercorrection. Therefore, more rigorous correction is necessary to achieve optimal sagittal alignment specifically in patients with severe baseline sagittal imbalance.
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Adult degenerative scoliosis (ADS) is a coronal plane deformity often accompanied by sagittal plane malalignment. Surgical correction may involve the major and/or distally-located fractional curves (FCs). Correction of the FC has been increasingly recognized as key to ameliorating radicular pain localized to the FC levels. The present study aims to summarize the literature on the rationale for FC correction in ADS. Three databases were systematically reviewed to identify all primary studies reporting the rationale for correcting the FC in ADS. Articles were included if they were English full-text studies with primary data from ADS ( ≥ 18 years old) patients. Seventy-four articles were identified, of which 12 were included after full-text review. Findings suggest FC correction with long-segment fusion terminating at L5 increases the risk of distal junctional degeneration as compared to constructs instrumenting the sacrum. Additionally, circumferential fusion offers greater FC correction, lower reoperation risk, and shorter construct length. Minimally invasive surgery (MIS) techniques may offer effective radiographic correction and improve leg pain associated with foraminal stenosis on the FC concavity, though experiences are limited. Open surgery may be necessary to achieve adequate correction of severe, highly rigid deformities. Current data support major curve correction in ASD where the FC concavity and truncal shift are concordant, suggesting that the FC contributes to the patient’s overall deformity. Circumferential fusion and the use of kickstand rods can improve correction and enhance the stability and durability of long constructs. Last, MIS techniques show promise for milder deformities but require further investigation.
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Objective Few studies have reported radiographic and clinical outcomes of transverse process hook (TPH) placement at the proximal thoracic upper instrumented vertebra (UIV) in adult spinal deformity (ASD) surgery. This study aims to investigate radiographic and clinical outcomes of TPH placement at the UIV for ASD surgery.
Methods This is a retrospective cohort of 56 patients with ASD (age, 59 ± 13 years; followup, 44 ± 19 months) from Johns Hopkins Hospital, who underwent long posterior spinal fusion to the proximal thoracic spine (T2–5). Visual analogue scale (VAS) for back pain, Oswestry Disability Index (ODI), 36-item Short Form health survey scores, thoracic kyphosis (TK), lumbar lordosis, sacral slope, pelvic tilt, pelvic incidence, proximal junctional kyphosis (PJK) angle, PJK incidence, pattern of PJK, grades of TPH dislodgement, revision surgery, and factors associated with high-grade TPH dislodgement were analyzed.
Results VAS for back pain and ODI values improved significantly from preoperatively to final follow-up. Mean change in PJK angle was 12° (range, 0.5°–43°). Twenty patients (36%) developed PJK, of whom 13 had compression fractures at 1 vertebra distal to the UIV (UIV–1). Final TPH position was stable in 42 patients (75%). In most patients (86%), TPH dislodgement did not progress after 6-month postoperative follow-up. Three patients (5.3%) underwent revision surgery to extend the fusion because of symptomatic PJK. Unstable TPH position was associated only with revision surgery and TK.
Conclusion TPH placement at the proximal thoracic UIV for long fusion showed favorable clinical and radiographic outcomes in terms of the incidence of PJK and mean PJK angle at mean 44-month follow-up. TPHs placed in the proximal thoracic UIV were in stable position in 75% of patients. Compression fracture at UIV–1 was the most common pattern of PJK. PJK angle progression was greater in revision cases and in patients with greater preoperative thoracic kyphosis.
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Neurospine 2023;20(4):1272-1280. Published online December 31, 2023
Objective Although adult spinal deformity (ASD) surgery aims to restore and maintain alignment, proximal junctional kyphosis (PJK) may occur. While existing scoring systems predict PJK, they predominantly offer a generalized 3-tier risk classification, limiting their utility for nuanced treatment decisions. This study seeks to establish a personalized risk calculator for PJK, aiming to enhance treatment planning precision.
Methods Patient data for ASD were sourced from the Korean spinal deformity database. PJK was defined a proximal junctional angle (PJA) of ≥ 20° at the final follow-up, or an increase in PJA of ≥ 10° compared to the preoperative values. Multivariable analysis was performed to identify independent variables. Subsequently, 5 machine learning models were created to predict individualized PJK risk post-ASD surgery. The most efficacious model was deployed as an online and interactive calculator.
Results From a pool of 201 patients, 49 (24.4%) exhibited PJK during the follow-up period. Through multivariable analysis, postoperative PJA, body mass index, and deformity type emerged as independent predictors for PJK. When testing machine learning models using study results and previously reported variables as hyperparameters, the random forest model exhibited the highest accuracy, reaching 83%, with an area under the receiver operating characteristics curve of 0.76. This model has been launched as a freely accessible tool at: (https://snuspine.shinyapps.io/PJKafterASD/).
Conclusion An online calculator, founded on the random forest model, has been developed to gauge the risk of PJK following ASD surgery. This may be a useful clinical tool for surgeons, allowing them to better predict PJK probabilities and refine subsequent therapeutic strategies.
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Adult spinal deformity (ASD) surgery aims to correct abnormal spinal curvature in adults, leading to improved functionality and reduced pain. However, this surgery is associated with various complications, one of which is proximal junctional failure (PJF). PJF can have a significant impact on a patient’s quality of life, necessitating a comprehensive understanding of its causes and the development of effective management strategies. This review aims to provide an in-depth understanding of PJF in ASD surgery. PJF is a complex complication resulting from a multitude of factors including patient characteristics, surgical techniques, and postoperative management. Age, osteoporosis, overcorrection of sagittal alignment, and poor bone quality are identified as significant risk factors. The clinical implications of PJF are substantial, often requiring revision surgery and causing a considerable decrease in patients’ quality of life. Prevention strategies include careful preoperative planning, appropriate patient selection, and optimization of surgical techniques. Treatment often necessitates a multifaceted approach, including surgical intervention and the management of underlying risk factors. Predictive modeling is an emerging field that may offer a promising avenue for the risk stratification of patients and individualized preventive strategies. A thorough understanding of PJF’s pathogenesis, risk factors, and clinical implications is essential for surgeons involved in ASD surgery. Current preventive measures and treatment strategies aim to mitigate the risk and manage the complications of PJF, but the complication cannot be entirely prevented. Future research should focus on the development of more effective preventive and treatment strategies, and predictive models could be valuable in this pursuit.
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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.
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