Background
Proximal junctional kyphosis (PJK) following long instrumented fusion is a well-recognized complication that does not negatively affect the clinical outcomes. However, there were few studies with regard to the long-term consequences of PJK. Objective: To investigate the long-term clinical and radiographic consequences of proximal junctional kyphosis (PJK) following the long instrumented fusion for elderly patients with sagittal imbalance.
Methods
Patients older than 60 years who underwent ≥4 fusion including the sacrum for sagittal imbalance were followed up longer than five years. PJK was defined as proximal junctional angle (PJA) >10° without any bony compromise or myelopathy. The radiographic and clinical outcomes were compared between PJK and non-PJK groups. Clinical outcome measures included visual analog scale (VAS) for back and leg, Oswestry disability index (ODI), and Scoliosis Research Society (SRS)-22 scores.
Results
A mean age was 69.2 years. An average follow-up duration was 92.4 months. There were 30 patients in PJK group and 43 in non-PJK group. At the final follow-up, pelvic incidence-lumbar lordosis mismatch, pelvic tilt, and sacral vertical axis were not different between the two groups. In PJK group, PJA significantly increased from 6.5° postoperatively to 21.2° at the final follow-up. At the final follow-up, clinical outcomes were worse in PJK group than in non-PJK group with regard to VAS for back, ODI, and SRS-22 scores except satisfaction domain. Three (10%) of 30 patients underwent a revision surgery for PJK progression.
Conclusions
PJK progressed with time and negatively affect the clinical outcomes in a long-term follow-up after ASD surgery.

Purpose
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.
Materials and Methods
We carried out a systematic search of PubMed for literatures published up to September 2016 with “proximal junctional kyphosis” and “proximal junctional failure” as search terms. A total of 57 literatures were searched. Finally, the 33 articles were included in this review.
Result
PJK and PJF are recognized complications after long instrumented posterior fusion in ASD surgery. PJK is multifactorial in origin and likely results from surgical, radiographic, and patient related risk factors. PJF is a progressive form of the PJK spectrum including bony fracture of uppermost instrumented vertebra (UIV) or UIV+1, subluxation between UIV and UIV+1, failure of fixation, neurological deficit, which may require revision surgery for proximal extension of fusion. Variable risk factors for PJK and PJF have been investigated, and they can be categorized into surgical, radiographic, and patient-related factors. There are several strategies to minimize PJK and PJF. Soft tissue protections, adequate selection of the UIV, prophylactic rib fixation, hybrid instrumentation such as hooks, vertebral cement augmentation at UIV and UIV+1, and age-appropriate spinopelvic alignment goals are worth consideration.
Conclusion
The ability to perform aggressive global realignment of spinal deformities has also led to the discovery of new complications such as PJK and PJF. Continuous research on PJK and PJF should be proceeded in order to comprehend the pathophysiology of these complications.