Instrumentation techniques to prevent proximal junctional kyphosis and proximal junctional failure in adult spinal deformity correction—a systematic review of biomechanical studies

Background contextCorrection of adult spinal deformity (ASD) by long segment instrumented spinal fusion is an increasingly common surgical intervention. However, it is associated with high rates of complications and revision surgery, especially in the elderly patient population. The high construct stiffness of instrumented thoracolumbar spinal fusion has been postulated to lead to a higher incidence of proximal junctional kyphosis (PJK) and failure (PJF). Several cadaveric biomechanical studies have reported on surgical techniques to reduce the incidence of PJF/PJK. As yet, no overview has been made of these biomechanical studies.PurposeTo summarize the evidence of all biomechanical studies that have assessed techniques to reduce PJK/PJF following long segment instrumented spinal fusion in the ASD patient population.Study designA systematic review.MethodsEMBASE and MEDLINE databases were searched for human and animal cadaveric biomechanical studies investigating the effect of various surgical techniques to reduce PJK/PJF following long segment instrumented thoracolumbar spinal fusion in the adult patient population. Studied techniques, biomechanical test methods, range of motion (ROM), intervertebral disc pressure (IDP) and other relevant outcome parameters were documented.ResultsTwelve studies met the inclusion criteria. Four of these studies included non-human cadaveric material. One study investigated the prophylactic application of cement augmentation (vertebroplasty), whereas the remaining studies investigated semi-rigid junctional fixation techniques to achieve a gradual transition zone of forces at the proximal end of a fusion construct, so-called topping-off. An increased gradual transition zone in terms of ROM compared to pedicle screw constructs was demonstrated for sublaminar tethers, sublaminar tape, pretensioned suture loops, transverse hooks and laminar hooks. Furthermore, reduced IDP was found after the application of sublaminar tethers, suture loops, sublaminar tapes and laminar hooks. Finally, two-level prophylactic vertebroplasty resulted in a lower incidence of vertebral compression fractures in a flexion-compression experiment.ConclusionsA variety of techniques, involving either posterior semi-rigid junctional fixation or the reinforcement of vertebral bodies, has been biomechanically assessed. However, the low number of studies and variation in study protocols hampers direct comparison of different techniques. Furthermore, determination of what constitutes an optimal gradual transition zone and its translation to clinical practice, would aid comparison and further development of different semi-rigid junctional fixation techniques. Even though biomechanics are extremely important in the development of PJK/PJF, patient-specific factors should always be taken into account on a case-by-case basis when considering to apply a semi-rigid junctional fixation technique.     

The effect of prophylactic vertebroplasty on the incidence of proximal junctional kyphosis and proximal junctional failure following posterior spinal fusion in adult spinal deformity: a 5-year follow-up study

Background Context

The incidence of proximal junctional kyphosis (PJK) ranges from 5% to 46% following adult spinal deformity surgery. Approximately 66% to 76% of PJK occurs within 3 months of surgery. A subset of these patients, reportedly 26% to 47%, develop proximal junctional failure (PJF) within 6 months postoperatively. To date, there are no studies evaluating the impact of prophylactic vertebroplasty on PJK and PJF incidence at long-term follow-up.

Caudally directed upper-instrumented vertebra pedicle screws associated with minimized risk of proximal junctional failure in patients with long posterior spinal fusion for adult spinal deformity

BACKGROUND CONTEXTIt is unknown whether upper instrumented vertebra (UIV) pedicle screw trajectory and UIV screw-rod angle are associated with development of proximal junctional kyphosis (PJK) and/or proximal junctional failure (PJF).PURPOSETo determine whether (1) the cranial-caudal trajectory of UIV pedicle screws and (2) UIV screw-vertebra angle are associated with PJK and/or PJF after long posterior spinal fusion in patients with adult spinal deformity (ASD).STUDY DESIGN/SETTINGRetrospective review.PATIENT SAMPLEWe included 96 patients with ASD who underwent fusion from T9–T12 to the pelvis (>5 vertebrae fused) between 2008 and 2015.OUTCOME MEASURESPedicle screw trajectory was measured as the UIV pedicle screw–vertebra angle (UIV-PVA), which is the mean of the two angles between the UIV superior endplate and both UIV pedicle screws. (Positive values indicate screws angled cranially; negative values indicate screws angled caudally.) We measured UIV rod-vertebra angle (UIV-RVA) between the rod at the point of screw attachment and the UIV superior endplate.METHODSDuring ≥2-year follow-up, 38 patients developed PJK, and 28 developed PJF. Mean (± standard deviation) UIV-PVA was ?0.9° ± 6.0°. Mean UIV-RVA was 87° ± 5.2°. We examined the development of PJK and PJF using a UIV-PVA/UIV-RVA cutoff of 3° identified by a receiver operating characteristic curve, while controlling for osteoporosis, age, sex, and preoperative thoracic kyphosis.RESULTSPatients with UIV-PVA ≥3° had significantly greater odds of developing PJK (odds ratio 2.7; 95% confidence interval: 1.0–7.1) and PJF (odds ratio 3.6; 95% confidence interval: 1.3–10) compared with patients with UIV-PVA <3°. UIV-RVA was not significantly associated with development of PJK or PJF.CONCLUSIONSIn long thoracic fusion to the pelvis for ASD, UIV-PVA ≥3° was associated with 2.7-fold greater odds of PJK and 3.6-fold greater odds of PJF compared with UIV-PVA <3°. UIV-RVA was not associated with PJK or PJF.LEVEL OF EVIDENCEIII     

Proximal junctional fracture and kyphosis after long spinopelvic corrective fixation for adult spinal deformity

BackgroundProximal junctional fractures (PJFx) are the main cause for proximal junctional kyphosis (PJK), a complication of adult spinal deformity surgery. This study investigated risk factors for PJFx when performing long spinopelvic corrective fixation with lateral interbody fusion from T9 to ilium.MethodsThis was a retrospective study of 43 patients with a minimum follow-up of 2 years. Radiographic measurements including thoracic kyphosis (TK), sagittal vertical axis (SVA), T1 pelvic angle (TPA), proximal junctional angle (PJA), lumbar lordosis (LL), lower LL, and pelvic tilt were measured preoperatively, one-month postoperatively, and at final follow up. TK and LL were also measured in a fulcrum backward-bending position preoperatively.ResultsAt final follow-up, PJK was found in 30/43 patients (69.8%); 20.9% of the cases had PJFx (9 patients). TPA (preoperative, and one-month postoperative) was significantly higher in the PJFx group than in the other groups. The differences in TPA, TK, and PJA between preoperative and one-month postoperative measurements in the PJFx group were significantly higher than those in the other groups. At final follow up, SVA was significantly higher in the PJFx group than in the “PJK without PJFx” group. TPA and TK were significantly higher in the PJFx group than in the other groups. PJA was significantly different between all groups.ConclusionPreoperative large TPA was the only risk factor for PJFx. Preoperative flexibility of the thoracolumbar spine and overcorrection of sagittal deformity were not related to PJFx or PJK.     

Proximal junctional kyphosis

Proximal Junctional Kyphosis (PJK) is defined as a proximal junctional sagittal Cobb angle of ≥ 10° or a proximal junctional sagittal Cobb angle at least 10° greater than the preoperative measurement. There are several risk factors for the development of PJK identified in literature using univariate analysis. Majority of these risk factors are no longer significant after multivariate analysis. Pointing to the fact that proximal junction kyphosis arises from a multifactorial etiology, further studies with long term follow-up are needed for patients with PJK to elicit risk factors in terms of patients, spinopelvic parameters, and surgical techniques.     

Proximal junctional kyphosis following adult spinal deformity surgery

Purpose

Proximal junctional kyphosis (PJK) is a common radiographic finding following long spinal fusions. Whether PJK leads to negative clinical outcome is currently debatable. A systematic review was performed to assess the prevalence, risk factors, and treatments of PJK.

Methods

Literature search was conducted on PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials using the terms ‘proximal junctional kyphosis’ and ‘proximal junctional failure’. Excluding reviews, commentaries, and case reports, we analyzed 33 studies that reported the prevalence rate, risk factors, and discussions on PJK following spinal deformity surgery.

Results

The prevalence rates varied widely from 6 to 61.7 %. Numerous studies reported that clinical outcomes for patients with PJK were not significantly different from those without, except in one recent study in which adult patients with PJK experienced more pain. Risk factors for PJK included age at operation, low bone mineral density, shorter fusion constructs, upper instrumented vertebrae below L2, and inadequate restoration of global sagittal balance.

Conclusions

Prevalence of PJK following long spinal fusion for adult spinal deformity was high but not clinically significant. Careful and detailed preoperative planning and surgical execution may reduce PJK in adult spinal deformity patients.     

Revision surgery in proximal junctional kyphosis

Proximal junctional kyphosis (PJK) is a relatively common complication following spinal deformity surgery that may require reoperation. Although isolating the incidence is highly variable, in part due to the inconsistency in how PJK is defined, previous studies have reported the incidence to be as high as 39% with revision surgery performed in up to 47% of those with PJK. Despite the discordance in reported incidence, PJK remains a constant challenge that can result in undesirable outcomes following adult spine deformity surgery. A comprehensive literature review using Medline and PubMed was performed. Keywords included “proximal junctional kyphosis,” “postoperative complications,” “spine deformity surgery,” “instrumentation failure,” and “proximal junctional failure” used separately or in conjunction. While the characterization of PJK is variable, a postoperative proximal junction sagittal Cobb angle at least 10°, 15°, or 20° greater than the measurement preoperatively, it is a consistent radiographic phenomenon that is well defined in the literature. While particular studies in the current literature may ascertain certain variables as significantly associated with the development of proximal junctional kyphosis where other studies do not, it is imperative to note that they are not all one in the same. Different patient populations, outcome variables assessed, statistical methodology, surgeon/surgical characteristics, etc. often make these analyses not completely comparable nor generalizable. The goal of adult spine deformity surgery is to optimize patient outcomes and mitigate postoperative complications whenever possible. Due to the multifactorial nature of this complication, further research is required to enhance our understanding and eradicate the pathology. Patient optimization is the principal guideline in not only PJK prevention, but overall postoperative complication prevention. These slides can be retrieved under Electronic Supplementary Material.     

Strap stabilization for proximal junctional kyphosis prevention in instrumented posterior spinal fusion

This is a retrospective, single-institution, cohort study. To evaluate the association of Mersilene tape use and risk of proximal junctional kyphosis (PJK), after surgical correction of adult spinal deformity (ASD) by posterior instrumented fusion (PIF). PJK, following long spinal PIF, is a complication which often requires reoperation. Mersilene tape, strap stabilization of the supra-adjacent level to upper instrumented vertebra (UIV) seems a preventive measure. Patients who underwent PIF for ASD with Mersilene tape stabilization (case group) or without (control group) between 2006 and 2016 were analyzed preoperatively to 2-year follow-up. Matching of potential controls to each case was performed. Radiographic sagittal Cobb angle (SCA), lumbar lordosis, pelvic tilt, sacral slope, and pelvic incidence were measured pre- and postoperatively, using a deformity measuring software program. PJK was defined as progression of postoperative junctional SCA at UIV ≥ 10°. Eighty patients were included: 20 cases and 60 controls. The cumulative rate of PJK ≥ 10° at 2-year follow-up was 15% in cases versus 38% of controls (OR = 0.28; P = 0.04) with higher latent period in cases, (20 vs. 7.5 months), P = 0.018. Mersilene tape decreased risk of PJK linked with the impact of the following confounders: age, ≥ 55 years old (OR = 0.19; 0.02 ≥ P ≤ 0.03); number of spinal levels fused 7–15 (OR = 0.13; 0.02 ≥ P ≤ 0.06); thoracic UIV (T12–T1) (OR = 0.13; 0.02 ≥ P ≤ 0.06); BMI ≥ 27 kg/m2 (OR = 0.22; 0.03 ≥ P ≤ 0.08); and osteoporosis (OR = 0.13; 0.02 ≥ P ≤ 0.08). Mersilene tape at UIV + 1 level decreases the risk of PJK following PIF for ASD. These slides can be retrieved under Electronic Supplementary Material.     

Prophylactic vertebral cement augmentation at the uppermost instrumented vertebra and rostral adjacent vertebra for the prevention of proximal junctional kyphosis and failure following long-segment fusion for adult spinal deformity

Background Context

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are common problems after long-segment (>5 levels) thoracolumbar instrumented fusions in the treatment of adult spinal deformity (ASD). No specific surgical strategy has definitively been shown to lower the risk of PJK as the result of a multifactorial etiology.

Proximal junctional kyphosis in adult spinal deformity: An up-to-date review

Proximal junctional kyphosis (PJK) is a complication following surgical treatment for adult spinal deformity. Most PJK occurs early within the postoperative period with reported rates ranging from 20% to 40%. Proximal junctional failure is a more severe form of PJK. Many risk factors have been identified suggesting multifactorial causation. Methods to prevent PJK include surgical techniques, reducing the rigidity of the construct, preserving surrounding tissue, constructing, and adhering to age-adjusted alignment goals, vertebroplasty, ligament augmentation, and teriparatide. Revision surgery sometimes results in recurrent PJK and is associated with substantial surgical and financial burdens which highlight the importance of prevention strategies and continued study.     

Relationship between iliac screw loosening and proximal junctional kyphosis after long thoracolumbar instrumented fusion for adult spinal deformity

European Spine Journal - Authors assumed that the stability of iliac screw (IS) fixation could affect the development of proximal junctional kyphosis (PJK). The purpose of this study was to analyze...     

脊柱后路固定术后近端交界区迟发性感染分析与治疗探讨

目的 :探讨脊柱后路固定术后近端交界性迟发感染的特点与处理对策。方法 :回顾性分析2010年2月至2015年10月1 325例行脊柱后路固定手术患者,发现10例迟发性感染,其中4例迟发感染发生在近端交界区而非手术部位,分别给予二联广谱抗生素抗感染治疗。对这4例患者的临床症状、体征、实验室检验、MRI、病理及治疗效果进行分析。结果:随访6个月~5年,未发现感染复发,4例患者出院时治疗效果满意,无神经损伤,1例患者2年后随访是出现交界性后凸。按腰椎术后日本N.Nakano和T.Nakano功能评定标准:优3例,差1例。结论:脊柱术后迟发感染发生率低,对脊柱后路固定术后近端交界区迟发感染病因机制可能是固定后临近节段应力集中,邻近节段退变,形成易感染区。患者脊柱后路固定术后顽固性腰背疼痛,结合血沉、C-反应蛋白增高、MRI的表现及病灶取样标本病理,则可明确诊断。足量地联合应用广谱抗生素治疗效果理想。     

Risk factor analysis of proximal junctional kyphosis after posterior fusion in patients with idiopathic scoliosis

Study design

A retrospective analysis of 150 adolescents who underwent spinal fusion for idiopathic scoliosis.

Objective

To analyse the incidence of the postoperative proximal junctional kyphosis after posterior fusion to the upper thoracic vertebra in adolescents with idiopathic scoliosis and to explore its risk factors.

Summary of background data

The reported incidence of the proximal junctional kyphosis after the posterior fusion in patients with idiopathic scoliosis varies depending on surgical methods and strategies adopted by the institution.

Methods

The changes in the Cobb angle of the proximal junctional kyphosis on the lateral spine X-ray were measured and the presence of PJK was recorded. The risk factors were screened using statistical analysis.

Results

PJK occurred in 35 out of 123 patients with an overall incidence of 28%. Among them, 28 patients (80%) experienced PJK within 1.5 years after surgery. The PJK-inducing factors included greater than 10° intraoperative decrease in thoracic kyphosis, thoracoplasty, the use of a pedicle screw at the top vertebra, autogenous bone graft and fusion to the lower lumbar vertebra (below L2).

Conclusions

There is a high incidence of postoperative proximal junctional kyphosis after posterior fusion to the upper thoracic vertebra within 1.5 years after surgery in adolescents with idiopathic scoliosis. In order to reduce its incidence, the risk factors for PJK should be carefully evaluated before surgery.     

Osteotomies in proximal junctional kyphosis in the cervicothoracic area

Introduction

Proximal junctional kyphosis (PJK) of the cervicothoracic spine is a deformity that can affect patients who have undergone long thoracolumbar instrumented fusion. Preoperative hyperkyphosis of the thoracic spine and changes of more than 30° in lumbar lordosis are independent risk factors for the onset of PJK.

Methods

When PJK occurs in the cervicothoracic spine, extension of the fusion with eventual application of osteotomy techniques is frequently necessary to treat symptomatic patients or in case a neurological deficit occurs. Ponte osteotomy and pedicle subtraction osteotomy (PSO) are the two most used techniques to restore a good cervicothoracic alignment, although they are still demanding procedures even for expert surgeons. In junctional fractures, a vertebral column resection can be performed to support the anterior column. Ponte osteotomy ideally restores 10° at each treated level, while PSO allows a segmental correction up to 30°–35°. Adequate preoperative planning is fundamental for outlining the correct surgery and choosing the appropriate osteotomy.

Conclusions

The aim of corrective surgery is to restore the cervicothoracic alignment, obtaining an adequate postoperative sagittal balance and decreasing the risk of further complications and new revision surgeries.

     

Effect of overcorrection on proximal junctional kyphosis in adult spinal deformity: analysis by age-adjusted ideal sagittal alignment

BACKGROUND CONTEXTThe effect of the degree of lumbar lordosis (LL) correction on proximal junctional kyphosis (PJK) has not been analyzed in context of the age-adjusted sagittal alignment goal.PURPOSETo determine the effect of sagittal correction on the incidence of PJK after an age-adjusted analysis in patients with adult spinal deformity (ASD).STUDY DESIGN/SETTINGRetrospective comparative study.PATIENT SAMPLESeventy-eight ASD patients who underwent deformity correction.OUTCOME MEASURESVisual analog scale (VAS), Oswestry Disability Index (ODI), and imaging.METHODSThis study included 78 ASD patients who underwent deformity correction and were followed-up more than 2 years. Patients were grouped according to the degree of LL correction relative to pelvic incidence (PI) by adjusting for age using the following formula: (age-adjusted ideal PI - LL) - (postoperative PI - LL). These were group U (undercorrection; <?10?, N=15), group I (ideal correction; ?10?–10?, N=34), and group O (over correction, >10?, N=29). Various clinical and radiological parameters were compared among groups. The risk factors for PJK were also evaluated.RESULTSThe overall incidence of PJK was 32.1% (25/78), with significantly higher PJK rate in group O (48.3%) compared with groups U (13.3%) and I (26.5%) (p=.041). The degree of postoperative LL correction relative to the PI by adjusting for age was a risk factor for the development of PJK (11.4° for PJK vs. 0.2° for non-PJK, p=.033). In addition, 2-year postoperative VAS (7.0 vs. 3.4, p<.001) and ODI (28.9 vs. 24.8, p=.040) scores were significantly higher in the PJK group than in the non-PJK group. A small PI (PI < 45°) was associated with a tendency of overcorrection (73.3%, P < 0.001) and thereby with the high incidence of PJK (53.3%, p=.005).CONCLUSIONSOvercorrection of LL relative to PI considering age-adjusted ideal sagittal alignment tends to increase the incidence of PJK. The incidence of PJK is expected to be high in patients with low PI (<45°) because of the tendency of overcorrection. To reduce the risk of PJK, surgeons should take age-adjusted parameters into account and exercise caution not to overcorrect patients with low PI, since this can result in suboptimal clinical outcomes.     

Progressive thoracic myelopathy caused by spinal calcium pyrophosphate crystal deposition because of proximal junctional vertebral compression fracture after lumbopelvic fusion

Purpose

We describe cases presenting with progressive thoracic myelopathy after lumbopelvic fusion attributed to proximal junctional vertebral compression fracture (PJF) followed by spinal calcium pyrophosphate dehydrate (CPPD) crystal deposition.

Methods

The study included six patients, ranging from 62 to 75 years. All patients had been treated previously with lumbopelvic fusion. The mean period from the detection of PJF to the onset of myelopathy was 4.8 months. Notably, five patients demonstrated upper-instrumented vertebra (UIV) collapse.

Results

After revision surgery involving decompressive laminectomy and extension of the spinal fusion, all patients experienced significant improvement. Photomicrographs of the resected ligamentum flavum showed CPPD crystals and multinucleated giant cells.

Conclusions

The combination of mechanical stress plus PJF and CPPD crystal deposition followed by a foreign body reaction to the deposited crystals caused myelopathy. Patients with radiographic evidence of PJF, especially UIV collapse, after lumbopelvic fusion should be followed carefully for the emergence of myelopathy.     

Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient

Background

To investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations.

Biomechanical study of the atlantoaxial joint after artifi- cial atlanto-odontoid joint arthroplasty

Objective:To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty by comparing with a conventional method.Meth...     

Poor visualization limits diagnosis of proximal junctional kyphosis in adolescent idiopathic scoliosis

Background Context

Multiple methods are used to measure proximal junctional angle (PJA) and diagnose proximal junctional kyphosis (PJK) after fusion for adolescent idiopathic scoliosis (AIS); however, there is no gold standard. Previous studies using the three most common measurement methods, upper-instrumented vertebra (UIV)+1, UIV+2, and UIV to T2, have minimized the difficulty in obtaining these measurements, and often exclude patients for which measurements cannot be recorded.