Owing to rapidly changing global demographics, adult spinal deformity (ASD) now accounts for a significant proportion of the Global Burden of Disease. Sagittal imbalance caused by age-related degenerative changes leads to back pain, neurological deficits, and deformity, which negatively affect the health-related quality of life (HRQoL) of patients. Along with the recognized regional, global, and sagittal spinopelvic parameters, poor paraspinal muscle quality has recently been acknowledged as a key determinant of the clinical outcomes of ASD. Although the Scoliosis Research Society-Schwab ASD classification system incorporates the radiological factors related to HRQoL, it cannot accurately predict the mechanical complications. With the rapid advances in surgical techniques, many surgical options for ASD have been developed, ranging from minimally invasive surgery to osteotomies. Therefore, structured patient-specific management is important in surgical decision-making, selecting the proper surgical technique, and to prevent serious complications in patients with ASD. Moreover, utilizing the latest technologies such as robotic-assisted surgery and machine learning, should help in minimizing the surgical risks and complications in the future.

Study Design. Retrospective study. Objective. To identify the risk factors for revision surgery among neurologically intact patients with proximal junctional failure (PJF) after adult spinal deformity (ASD) surgery. Summary of Background Data. PJF following long fusion for ASD is a well-recognized complication that negatively affects clinical outcomes. However, revision surgery is not required for every patient with PJF especially if the patient does not present with neurologic deficit. Identifying the risk factors of revision surgery is necessary to determine who will need revision surgery as well as when is the right time for the revision surgery. Methods. Sixty-nine neurologically intact patients with PJF following ASD surgery were followed up with more than 2 years after PJF development or until undergoing revision surgery. PJF was divided into ligamentous failure (proximal junctional angle [PJA] of more than 208) and bony failure. According to the conduct of revision surgery, two groups (revision and no revision) were created. Risk factors for revision surgery were analyzed in univariate and multivariate analysis with regard to patient, surgical and radiographic variables. Results. The mean age at the time of PJF development was 70.9 years. There were 45 patients with bony failure and 24 with ligamentous failure. Revision surgery was performed for 23 patients (33.3%). Multivariate analysis revealed that bony failure (odds ratio: 10.465) and PJA (odds ratio: 1.131) were significant risk factors. For those with bony failure, the cutoff value of PJA for performing revision surgery was calculated as 228. The revision rate was significantly highest in patients (63.6%) with bony failure þ PJA 228 or higher followed by patients (26.1%) with bony failure þ PJA less than 228 and patients (12.5%) with ligamentous failure (P ¼ 0.002). Conclusion. Bony failure with PJA of greater than 228 increased the likelihood for revision surgery. Therefore, early surgical intervention should be considered in these patients.

Study Design. Retrospective study.Objective. The aim of this study was to investigate the longterm fate of asymptomatic PJK focusing on the elderly patients with sagittal imbalance by comparing the patients with and without PJK. Summary of Background Data. Most of previous studies demonstrated that PJK does not negatively affect the clinical outcome compared to that of the patients without PJK. The question ''will the asymptomatic PJK remain asymptomatic even in long-term follow-up?'' has not been answered yet because the previous results were based on the short follow-up duration. Methods. Patients >60 years who underwent four or more level fusions to the sacrum for sagittal imbalance were followed up for >5 years. The radiographic and clinical outcomes were compared between PJK (n ¼ 30) and non-PJK groups (n ¼ 43). PJK was defined by proximal junctional angle (PJA) >108. Only patients with >3 years of follow-up duration after PJK development were included in PJK group. The clinical outcome measures included visual analog scale (VAS) for the back and leg, Oswestry disability index (ODI), and Scoliosis Research Society (SRS)-22 scores. Results. The mean age was 69.2 years. Total follow-up duration was 92.4 months. Time between PJK development and the last follow-up was 67.4 months in PJK group. Although there were no differences between the two groups in terms of pelvic incidence-lumbar lordosis mismatch, pelvic tilt, or sacral vertical axis, PJA significantly increased from 6.58 postoperatively to 21.28 at the final follow-up in the PJK group. The clinical outcomes were worse (such as VAS for the back, ODI, and SRS-22 scores) in the PJK group than in non-PJK group, except for the satisfaction domain. Three (10%) of 30 patients underwent a revision surgery for PJK progression. Conclusion. Even if PJK was asymptomatic at initial development, it progressed radiographically with time and eventually gave a negative impact on the clinical outcomes in long-term follow-up.