Proximal Junctional Kyphosis and Proximal Junctional Failure

We sought to evaluate the clinical impact of lordosis orientation (LO) on proximal junctional kyphosis (PJK) development in adult spinal deformity surgery.

This study included 152 patients who underwent low thoracic (T9–T12) to pelvis fusion and were followed up for ≥2 years. In the literature, 6 radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV−femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors including 6 LO parameters were investigated using logistic regression analysis to identify risk factors for PJK.

The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI)–lumbar lordosis (LL) (odds ratio [OR] = 0.962, 95% confidence interval: 0.929–0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% confidence interval: 1.028–1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = −0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle.

LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection and overcorrection to prevent PJK development.

Retrospective review.

This bibliometric review summarizes the publication trends and critical information about the most cited Proximal Junction Kyphosis (PJK) articles.

Data: Proximal junctional kyphosis is frequently diagnosed after spinal fusion surgery. However, there continues to be heavy debate regarding the definition, incidence, risk factors, and treatment of this disorder.

Nine hundred eleven articles were found when searching The Web of Science database with the keywords “Proximal junctional kyphosis” and “proximal junctional failure.” The 200 top-cited articles were reviewed and screened to ensure PJK was discussed. The articles were filtered based on the highest to lowest number of citations, and the top 50 articles were chosen. Inclusion criteria included articles that contained a discussion of PJK and outcomes after surgery. Exclusion criteria included articles without mentioning PJK, or that studied non-human subjects. The 50 most cited articles were sorted by level of evidence and their classification for analysis.

The 50 most cited articles in this study were published a total of 6056 times. These articles were cited 71–413 times in the literature, with publications from 1994 to 2018. Most of the top 50 articles (64%) were published in the USA. Specifically, HSS and Washington University are the institutions with the most contributions to the publication of the most cited articles on PJK (n = 16). Lenke was the author that contributed to most publications in the top 50 articles on PJK.

This study provides a framework for the most cited articles published on PJK. Most articles on this topic were in the category of clinical outcomes (36%) and were of a level of evidence III (46%). Most of the top-cited articles came from the journal Spine (68%) and were published in the USA (64%). These top-cited papers are essential to understanding this critical trending topic in spine surgery.

III.

Proximal junctional kyphosis and failure are important complications in reconstructive spine surgery. The impact of proximal junctional pathology on health status is variable, and junctional failure may involve compromise of neural and physical function, and may require revision surgery. The risk factors for proximal junctional kyphosis include multilevel fusion to the sacrum, malalignment of the spine, choice of upper instrumented vertebra, magnitude of realignment, bone and muscle quality, tension band integrity and characteristics of the unfused spine. The pathophysiology of proximal junctional pathology involve fracture and bony failure, ligamentous and soft tissue failure, and combined bone and soft tissue failure. Prevention of proximal junctional pathology is an important goal, and has a significant impact on improving the outcomes and durability of spinal reconstructive surgery. Prevention strategies are derived from an understanding of the underlying causes of junctional pathology. Preoperative planning to determine optimal post-operative alignment, and intraoperative strategies to achieve that alignment are important for prevention of junctional pathology. Preoperative preparation of the patient with optimization of bone quality, extensor muscle strength and body mass index may prevent junctional complications. Surgical strategies including anterior column load sharing and posterior augmentation of fixation are useful for prevention of junctional pathology. Cement augmentation at the upper instrumented vertebra, with possible inclusion of the next cephalad vertebra may be protective of bone failure. Ligamentoplasty and preservation of the tension band may be protective of soft tissue failure. Proximal junctional pathology remains an important complication in spinal reconstructive surgery. Understanding the factors associated with proximal junctional pathology including the mechanisms underlying junctional kyphosis, and awareness of the strategies for avoidance of junctional pathology will empower the surgeon to reduce the risk of post-operative junctional kyphosis and lead to improved outcomes in adult spinal deformity surgery.