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.

Minimally invasive TLIF has been reported to be a useful treatment option for the patients with various degenerative lumbar diseases. Many studies have reported the favorable clinical results of MIS TLIF. However it remains technically demanding, leading to higher complication rates and longer operative times during the early period of the learning curve. It showed some potential complications due to small working space and visual field. In this study, authors tried to find out various possible complications and some tips avoiding these complications through the review of various articles and authors’ clinical experiences. In many studies, the general complication fusion rates of MIS TLIF have been reported to be similar to that of open fusion. The technical difficulty of the procedure, combined with inadequate training, is evident in initial studies of MIS TLIF. A difficult learning curve of MIS TLIF demands that surgeons have sufficient preclinical training, and education is obtained before the application of MIS TLIF in clinical practice.

Purpose
Higher viscous cement can be injected through larger-diametered tubes with lower pressure. The lower the cement modulus is, the less the stress-transfer would be. The lower-pressure percutaneous vertebroplasty with blood-mixed cement(LP-PVP^blood ) was devised to overcome technical problems in conventional percutaneous vertebroplasty(C-PVP). We would like to prove the validity of technical modifications to increase viscosity of cement being injected and reduce final modulus of cement.
Methods
Nineteen C-PVPs, 51 kyphoplasty (KPs), 23 LP-PVPs and 70 LP-PVP^blood s were analyzed in radiologic point of view. The successful cases with sufficient cement volume(≥ 5ml) were also analyzed as a subgroup.
Results
Asymptomatic cement leakage(CL) showed a similar tendency in LP-PV^blood (17.1%) compared to other groups(21.1~27.5%, p=0.514), even though the injected cement volume in LP-PVP^blood (6.9ml) was much more than that of C-PVP(3.5ml, p=0.000). Vertebral height restoration(VHR) was significantly higher(11.7%) than C-PVP(4.7%, p=0.024). Vertebral body subsidence(VS) was less in KP(1.1%) than others(2.1~5.9%, p=0.000). But, adjacent vertebral compression fractures(VCFs) happened more frequently in KP(15.7%) than others (0~5.3%, p=0.001). In subgroup analysis, the rates of successful cases were significantly higher in LP-PVP^blood (85.7%) than in C-PVP(5.3%, p=0.000). CLs and VHRs showed no significant differences. VS was significantly less in KP(1.0%, p=0.000) but adjacent VCF developed more frequently in KP(21.1%) than LP-PVP^blood (0%, p=0.001).
Conclusions
The LP-PVP^blood which stands for larger diameter tubes for injecting sufficient volume of higher viscous cement and more interdigitation by omitting balloon and lower modulus blood-mixed cement was appraised to reduce risk of cement leakage than C-PVP and decrease stress transfer to adjacent vertebrae than KP.