Clinical outcomes and complications after pedicle subtraction osteotomy for fixed sagittal imbalance patients : a long-term follow-up data

OBJECTIVE

Clinical, radiographic, and outcomes assessments, focusing on complications, were performed in patients who underwent pedicle subtraction osteotomy (PSO) to assess correction effectiveness, fusion stability, procedural safety, neurological outcomes, complication rates, and overall patient outcomes.

METHODS

We analyzed data obtained from 13 consecutive PSO-treated patients presenting with fixed sagittal imbalances from 1999 to 2006. A single spine surgeon performed all operations. The median follow-up period was 73 months (range 41-114 months). Events during perioperative course and complications were closely monitored and carefully reviewed. Radiographs were obtained and measurements were done before surgery, immediately after surgery, and at the most recent follow-up examinations. Clinical outcomes were assessed using the Oswestry Disability Index and subjective satisfaction evaluation.

RESULTS

Following surgery, lumbar lordosis increased from -14.1 degrees +/- 20.5 degrees to -46.3 degrees +/- 12.8 degrees (p < 0.0001), and the C7 plumb line improved from 115 +/- 43 mm to 32 +/- 38 mm (p < 0.0001). There were 16 surgery-related complications in 8 patients; 3 intraoperative, 3 perioperative, and 10 late-onset postoperative. The prevalence of proximal junctional kyphosis (PJK) was 23% (3 of 13 patients). However, clinical outcomes were not adversely affected by PJK. Intraoperative blood loss averaged 2,984 mL. The C7 plumb line values and postoperative complications were closely correlated with clinical results.

CONCLUSION

Intraoperative or postoperative complications are relatively common following PSO. Most late-onset complications in PSO patients were related to PJK and instrumentation failure. Correcting the C7 plumb line value with minimal operative complications seemed to lead to better clinical results.

Patients with proximal junctional kyphosis after stopping at thoracolumbar junction have lower muscularity, fatty degeneration at the thoracolumbar area

BACKGROUND CONTEXT

There are several reports regarding pathogeneses and risk factors for proximal junctional kyphosis (PJK) in adult spinal deformity surgery. However, the relationship between thoracolumbar muscle condition and PJK has not been investigated yet.

PURPOSE

We aimed to elucidate the thoracolumbar muscle conditions on the incidence of PJK in adult patients with spinal deformity treated by long instrumented spinal fusion surgery stopping at thoracolumbar junction with a minimum 2-year follow-up (F/U).

STUDY DESIGN

This is a retrospective review of prospective database.

PATIENT SAMPLE

A total of 44 cases of patients having multilevel spinal instrumented fusion stopping at thoracolumbar junction for adult spinal deformity in two academic institutions from 2004 to 2012 were enrolled in this study.

OUTCOME MEASURES

For clinical outcomes, the Scoliosis Research Society questionnaire-22r (SRS-22r) was used preoperatively and at ultimate F/U.

METHODS

Inclusion criteria were age >20 and minimum five vertebrae fused from T9 upper instrumented vertebra (UIV) to any lower instrumented vertebra. Radiographic assessment included pelvic parameters, Cobb measurements in the coronal-sagittal plane, and measurements of the thoracolumbar muscularity (cross-sectional area of muscle-vertebral body ratio×100) and fatty degeneration (signal intensity of muscle-subcutaneous fat ratio×100).

RESULTS

The prevalence of PJK was 38.6%. Age at surgery, gender, fusions extending to the sacrum, levels fused, combined anterior-posterior surgery, and a UIV level were not significantly different between PJK and non-PJK groups. Lower bone mineral density (BMD; T-score: -2.5 vs. -1.3, p=.003) and lower muscularity and higher fatty degeneration at the level of T10 to L2 (131.8 vs. 159.0, p<.01; 59.0 vs. 44.0, p<.001, respectively) were identified risk factors for PJK. Radiographic parameters demonstrated a higher postoperative lumbar lordosis (LL) change (43.8 vs. 29.3, p<.001) and a larger sagittal vertical axis (SVA) change with surgery (8.4 cm vs. 4.8 cm, p=.01) in those with PJK. Although SRS postop pain scores were inferior in PJK group (3.3 vs. 4.1, p<.05), there were no significant differences in the average scores between the groups (3.5 vs. 3.3, p<.05).

CONCLUSIONS

Patients with PJK had lower thoracolumbar muscularity and higher fatty degeneration than patients without PJK before surgery. Our data suggest that osteoporosis, large corrections in LL and SVA with surgery, and lower muscularity and higher fatty degeneration at the thoracolumbar area can lead to PJK.

Type of Anchor at the Proximal Fusion Level Has a Significant Effect on the Incidence of Proximal Junctional Kyphosis and Outcome in Adults After Long Posterior Spinal Fusion

STUDY DESIGN

Retrospective review.

OBJECTIVES

To compare the incidence of proximal junctional kyphosis (PJK) and the clinical, radiographic, and functional outcomes in adults undergoing long posterior spinal fusion with transverse process hooks versus pedicle screws at the uppermost instrumented vertebrae.

SUMMARY OF BACKGROUND DATA

Proximal junctional kyphosis often occurs after instrumented long spinal fusion. Although there have been numerous studies of PJK development in adolescents with idiopathic scoliosis, few studies have focused on adults.

METHODS

This study reviewed data on 47 consecutive adult patients who underwent long spinal fusion (five or more levels) with hooks or screws at the uppermost instrumented vertebrae, from 2004 through 2009, and had 2-year radiographic and clinical follow-up. The hook group (20 patients) and screw group (27 patients) were similar in terms of age, gender, and levels fused. Proximal junctional kyphosis was defined as a sagittal Cobb angle of at least 10° between the lower end plate of the uppermost instrumented vertebrae and the upper end plate of the 2 immediately superior vertebrae, and at least 10° of progression from the previous measurement. The groups' radiographs, complications, and functional outcomes (Scoliosis Research Society-22 Patient Questionnaire and the Oswestry Disability Index) were compared using Hotelling's t² test (significance, p < .05).

RESULTS

Comparing immediate postoperative and final follow-ups, none of the 20 patients in the hook group versus 8 of 27 patients in the screw group (29.6%) developed PJK (p = .01). There were no statistical differences between groups in major or minor complications rates. At final follow-up, patients with hooks had significantly higher functional scores than those with screws (p < .05), and patients with PJK had significantly lower functional scores in all Scoliosis Research Society-22 Patient Questionnaire domains except satisfaction.

CONCLUSIONS

Transverse process hooks were associated with a lower incidence of PJK and higher functional scores than pedicle screws.

Acute proximal junctional failure in patients with preoperative sagittal imbalance

BACKGROUND CONTEXT

Proximal junctional failure (PJF) is a recognized complication of spinal deformity surgery. Acute PJF (APJF) has recently been demonstrated to be 5.6% in the adult spinal deformity (ASD) population. The incidence and rate of return to the operating room for APJF have not been specifically investigated in individuals with sagittal imbalance.

PURPOSE

The purpose of this study was to report the incidence of APJF in patients with preoperative sagittal imbalance and the rate of return to the operating room for APJF.

STUDY DESIGN/SETTING

This study is based on a retrospective review of prospectively collected database of ASD patients.

PATIENT SAMPLE

One hundred seventy-three consecutive patients were included with preoperative sagittal imbalance according to one of the following common parameters: sagittal vertical axis (SVA) greater than 50 mm, global sagittal alignment greater than 45°, or pelvic incidence minus lumbar lordosis greater than 10°.

OUTCOME MEASURES

Outcome measure was presence and/or absence of APJF defined as fracture at the upper instrumented vertebra (UIV) or UIV+1, failure of UIV fixation, 15° or more proximal junctional kyphosis, or need for extension of instrumentation within 6 months of surgery.

METHODS

We performed radiographic measurements on X-rays at preoperative, immediate postoperative, and 6-month follow-up visits. The APJF rate was reported for the entire patient population with preoperative sagittal imbalance. Acute PJF incidence was calculated postoperatively for each of the accepted sagittal balance parameters and/or formulas. Patients with persistent postoperative sagittal imbalance were compared with the sagittally balanced group. We also assessed for threshold values.

RESULTS

Acute PJF was observed in 60 of 173 patients (35%) and was least common in fusions with the UIV in the upper thoracic (UT) spine (p=.035). Of those who developed APJF, 21.7% required surgery. Proximal junctional kyphosis 15° or more was the most common form of APJF in fusions to the UT spine but least likely to need revision (p=.014). The most common mode of failure in lower thoracic (LT) or lumbar (L) fusions was UIV fracture. Postoperative SVA less than 50 mm was a significant risk factor for APJF (p=.009).

CONCLUSIONS

Acute PJF is more common in patients with preoperative sagittal imbalance (35%) than the general adult deformity patient population, and 37% of those with APJF require revision. It is least common when the UIV is in the UT spine, compared with the LT or L spine. Sagittal balance correction to an SVA 50 mm or less was a significant risk factor in patients with preoperative sagittal imbalance.

Proximal Junctional Kyphosis: Diagnosis, Pathogenesis, and Treatment

Proximal junctional kyphosis (PJK) is a common radiographic finding after long spinal fusion. A number of studies on the causes, risk factors, prevention, and treatment of PJK have been conducted. However, no clear definition of PJK has been established. In this paper, we aimed to clarify the diagnosis, prevention, and treatment of PJK by reviewing relevant papers that have been published to date. A literature search was conducted on PubMed using "proximal junctional", "proximal junctional kyphosis", and "proximal junctional failure" as search keywords. Only studies that were published in English were included in this study. The incidence of PJK ranges from 5% to 46%, and it has been reported that 66% of cases occur 3 months after surgery and approximately 80% occur within 18 months. A number of studies have reported that there is no significantly different clinical outcome between PJK patients and non-PJK patients. One study showed that PJK patients expressed more pain than non-PJK patients. However, recent studies focused on proximal junctional failure (PJF), which is accepted as a severe form of PJK. PJF showed significant adverse impact in clinical aspect such as pain, neurologic deficit, ambulatory difficulties, and social isolation. Numerous previous studies have identified various risk factors and reported on the treatment and prevention of PJK. Based on these studies, we determined the clinical significance and impact of PJK. In addition, it is important to find a strategic approach to the proper treatment of PJK.

Proximal junctional kyphosis and failure-diagnosis, prevention, and treatment

Technical advancements have enabled the spinal deformity surgeon to correct severe spinal mal-alignment. However, proximal adjacent segment pathology (ASP) remains a significant issue. Examples include proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Agreement on the definition, classification, and pathophysiology of PJK and PJF remains incomplete, and an understanding of the risk factors, means of prevention, and treatment of this problem remains to be elucidated. In general, PJK is a relatively asymptomatic radiographic diagnosis managed with patient reassurance and monitoring. On the other hand, PJF is characterized by mechanical instability, pain, and more severe kyphosis, with potential for neurologic compromise. Patients who develop PJF more often require revision surgery than those with PJK. This chapter will review the current understanding of PJK and PJF.

Proximal Junctional Kyphosis and Proximal Junctional Failure Following Adult Spinal Deformity Surgery

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. We carried out a systematic search of PubMed for literatures published up to September 2017 with "proximal junctional kyphosis," "proximal junctional failure," and "adult spinal deformity" as search terms. A total of 98 literatures were searched. The 37 articles were included in this review. PJK is multifactorial in origin and likely results from variable risk factors. PJF is a progressive form of the PJK spectrum including bony fracture, subluxation between UIV and UIV+1, failure of fixation, neurological deficit, which may require revision surgery for proximal extension of fusion. Soft tissue protections, adequate selection of the UIV, prophylactic rib fixation, hybrid instrumentation such as hooks, vertebral cement augmentation at UIV and UIV+1, adequate selection material of rods and age-appropriate spinopelvic alignment goals are strategies to minimize PJK and PJF. The ability to perform aggressive global realignment of spinal deformities has also led to the discovery of new complications such as the PJK and PJF. Continuous research on PJK and PJF should be proceeded in order to comprehend the pathophysiology of these complications.

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.

PURPOSE

The purpose of this study is to evaluate the long-term radiographic and clinical outcomes, and incidence of PJK and PJF, after prophylactic vertebroplasty for long-segment thoracolumbar posterior spinal fusion (PSF).

STUDY DESIGN

This is a prospective cohort study.

PATIENT SAMPLE

Thirty-nine patients, of whom 87% were female, who underwent two-level prophylactic vertebroplasty at the upper instrumented and supra-adjacent vertebrae at the time of index PSF were included in this study.

OUTCOME MEASURES

Clinical outcomes were assessed using the Scoliosis Research Society-22 (SRS-22), and Short-Form (SF) 36 questionnaires, and the Oswestry Disability Index (ODI). Radiographic parameters including PJK angle, and coronal and sagittal alignment, were calculated, along with relevant perioperative complications and revision rates.

METHODS

Of the 41 patients who received two-level prophylactic vertebroplasty at the upper instrumented and supra-adjacent vertebrae at the time of index PSF, and comprised a cohort with previously published 2-year follow-up data, 39 (95%) completed 5-year follow-up (average: 67.6 months). Proximal junctional kyphosis was defined as a change in the PJK angle ≥10° between the immediate postoperative and final follow-up radiograph. Proximal junctional failure was defined as acute proximal junctional fracture, fixation failure, or kyphosis requiring extension of fusion within the first 6 months postoperatively.

RESULTS

Thirty-nine patients with a mean age of 65.6 (41-87) years were included in this study. Of the 39 patients, 28.2% developed PJK (11: 7.7% at 2 years, 20.5% between 2 and 5 years), and 5.1% developed acute PJF. Two of the 11 PJK patients required revision for progressive worsening of the PJK. There were no proximal junctional fractures. There was no significant difference in preoperative, immediate postoperative, and final follow-up measurements of thoracic kyphosis, lumbar lordosis, and coronal or sagittal alignment between patients who developed PJK, PJF, or neither (p>.05). There was no significant difference in ODI, SRS-22, or SF-36 scores between those with and without PJK or PJF (p>.05).

CONCLUSIONS

This long-term follow-up demonstrates that prophylactic vertebroplasty may minimize the risk for junctional failure in the early postoperative period. However, it does not appear to decrease the incidence of PJK at 5 years.

Rod stiffness as a risk factor of proximal junctional kyphosis after adult spinal deformity surgery: comparative study between cobalt chrome multiple-rod constructs and titanium alloy two-rod constructs

BACKGROUND CONTEXT

Little is known about the effect of rod stiffness as a risk factor of proximal junctional kyphosis (PJK) after adult spinal deformity (ASD) surgery.

PURPOSE

The aim of this study was to compare radiographic outcomes after the use of cobalt chrome multiple-rod constructs (CoCr MRCs) and titanium alloy two-rod constructs (Ti TRCs) for ASD surgery with a minimum 1-year follow-up.

STUDY DESIGN

Retrospective case-control study in two institutes.

PATIENT SAMPLE

We included 54 patients who underwent ASD surgery with fusion to the sacrum in two academic institutes between 2002 and 2015.

OUTCOME MEASURES

Radiographic outcomes were measured on the standing lateral radiographs before surgery, 1 month postoperatively, and at ultimate follow-up. The outcome measures were composed of pre- and postoperative sagittal vertical axis (SVA), pre- and postoperative lumbar lordosis (LL), pre- and postoperative thoracic kyphosis (TK)+LL+pelvic incidence (PI), pre- and postoperative PI minus LL, level of uppermost instrumented vertebra (UIV), evaluation of fusion after surgery, the presence of PJK, and the occurrence of rod fracture.

MATERIALS AND METHODS

We reviewed the medical records of 54 patients who underwent ASD surgery. Of these, 20 patients had CoCr MRC and 34 patients had Ti TRC. Baseline data and radiographic measurements were compared between the two groups. The Mann-Whitney U test, the chi-square test, and the Fisher exact test were used to compare outcomes between the groups.

RESULTS

The patients of the groups were similar in terms of age, gender, diagnosis, number of three-column osteotomy, levels fused, bone mineral density, preoperative TK, pre- and postoperative TK+LL+PI, SVA difference, LL change, pre- and postoperative PI minus LL, and location of UIV (upper or lower thoracic level). However, there were significant differences in the occurrence of PJK and rod breakage (PJK: CoCr MRC: 12 [60%] vs. Ti TRC: 9 [26.5%], p=.015; occurrence of rod breakage: CoCr MRC: 0 [0%] vs. Ti TRC: 11 [32.4%], p=.004). The time of PJK was less than 12 months after surgery in the CoCr MRC group. However, 55.5% (5/9) of PJK developed over 12 months after surgery in the Ti TRC group.

CONCLUSIONS

Increasing the rod stiffness by the use of cobalt chrome rod and can prevent rod breakage but adversely affects the occurrence and the time of PJK.

Sagittal balance is more than just alignment: why PJK remains an unresolved problem

BACKGROUND

The durability of adult spinal deformity surgery remains problematic. Revision rates above 20 % have been reported, with a range of causes including wound infection, nonunion and adjacent level pathology. While some of these complications have been amenable to changes in patient selection or surgical technique, Proximal Junctional Kyphosis (PJK) remains an unresolved challenge. This study examines the contributions of non-mechanical factors to the incidence of postoperative sagittal imbalance and PJK after adult deformity surgery.

METHODS

We reviewed a consecutive series of adult spinal deformity patients who required revision for PJK from 2013 to 2015 and examined in their medical records in detail.

RESULTS

Neurologic disorders were identified in 22 (76 %) of the 29 PJK cases reviewed in this series. Neurologic disorders included Parkinson's disease (1), prior stroke (5), metabolic encephalopathy (2), seizure disorder (1), cervical myelopathy (7), thoracic myelopathy (1), diabetic neuropathy (5) and other neuropathy (4). Other potential comorbidities affecting standing balance included untreated cataracts (9), glaucoma (1) and polymyositis (1). Eight patients were documented to have frequent falls, with twelve cases having a fall right before symptoms related to the PJK were noted.

CONCLUSION

PJK is an important contributing factor to the substantial and unsustainable rate of revision surgery following adult deformity correction. Multiple efforts to avoid PJK via alterations in surgical technique have been largely unsuccessful. This study suggests that non-mechanical neuromuscular co-morbidities play an important role in post-operative sagittal imbalance and PJK. Recognizing the multi-factorial etiology of PJK may lead to more successful strategies to avoid PJK and improve surgical outcomes.

Risk Factors of Proximal Junctional Kyphosis after Multilevel Fusion Surgery: More Than 2 Years Follow-Up Data

OBJECTIVE

Proximal junctional kyphosis (PJK) is radiologic finding, and is defined as kyphosis of >10° at the proximal end of a construct. The aim of this study is to identify factors associated with PJK after segmental spinal instrumented fusion in adults with spinal deformity with a minimum follow-up of 2 years.

METHODS

A total of 49 cases of adult spinal deformity treated by segmental spinal instrumented fusion at two university hospitals from 2004 to 2011 were enrolled in this study. All enrolled cases included at least 4 or more levels from L5 or the sacral level. The patients were divided into two groups based on the presence of PJK during follow-up, and these two groups were compared to identify factors related to PJK.

RESULTS

PJK was observed in 16 of the 49 cases. Age, sex and mean follow-up duration were not statistically different between two groups. However, mean bone marrow density (BMD) and mean back muscle volume at the T10 to L2 level was significantly lower in the PJK group. Preoperatively, the distance between the C7 plumb line and uppermost instrumented vertebra (UIV) were no different in the two groups, but at final follow-up a significant intergroup difference was observed. Interestingly, spinal instrumentation factors, such as, receipt of a revision operation, the use of a cross-link, and screw fracture were no different in the two groups at final follow-up.

CONCLUSION

Preoperative BMD, sagittal imbalance at UIV, and thoracolumbar muscle volume were found to be strongly associated with the presence of PJK.

Proximal Junctional Kyphosis in Adult Spinal Deformity: Definition, Classification, Risk Factors, and Prevention Strategies

Proximal junctional problems are among the potential complications of surgery for adult spinal deformity (ASD) and are associated with higher morbidity and increased rates of revision surgery. The diverse manifestations of proximal junctional problems range from proximal junctional kyphosis (PJK) to proximal junctional failure (PJF). Although there is no universally accepted definition for PJK, the most common is a proximal junctional angle greater than 10° that is at least 10° greater than the preoperative measurement. PJF represents a progression from PJK and is characterized by pain, gait disturbances, and neurological deficits. The risk factors for PJK can be classified according to patient-related, radiological, and surgical factors. Based on an understanding of the modifiable factors that contribute to reducing the risk of PJK, prevention strategies are critical for patients with ASD.

Preliminary Results of the Effect of Prophylactic Vertebroplasty on the Incidence of Proximal Junctional Complications After Posterior Spinal Fusion to the Low Thoracic Spine

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To evaluate, in adults undergoing posterior spinal fusions, 1) the effect of prophylactic vertebroplasty on the incidence of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF), and 2) the difference in outcomes between those who did and did not develop PJK or PJF.

SUMMARY OF BACKGROUND DATA

Proximal junctional kyphosis occurs in 20% to 39% of adults after posterior spinal fusions; a subset develops PJF.

METHODS

From 2005 through 2008, we treated 41 consecutive patients (40 years old or more) with spinal deformity with 2-level prophylactic vertebroplasty (at the upper instrumented vertebrae and the supra-adjacent vertebrae) during posterior spinal fusion. The 38 patients with 24 months' follow-up formed our study group. We measured patient outcomes with the Scoliosis Research Society-24 questionnaire, the Oswestry Disability Index, and the 12-item Short Form Survey. All patients completed each assessment preoperatively, and 89% or more did so postoperatively. We compared postoperative and final follow-up radiographs to identify the PJK incidence (ie, a PJK angle change of 10° or more), and analyzed the PJK, PJF, and non-PJK/PJF groups for outcome scores with Student t test and chi-square test (significance, p < .05).

RESULTS

Three patients (8%) developed PJK and 2 (5%) developed PJF, markedly lower incidences than those previously reported. At final follow-up, patients with PJK or PJF reported statistically significant lower pain and satisfaction Scoliosis Research Society-24 scores than did patients in the non-PJK/PJF group, but there were no significant differences in Scoliosis Research Society-24 mental health or function scores between groups. All patients had significant improved Oswestry Disability Index and 12-item Short Form Survey scores.

CONCLUSIONS

Prophylactic vertebroplasty in long posterior spinal fusions for adult spinal deformity resulted in a low incidence of PJF and PJK, with only small differences in outcome scores between those who did and did not develop PJK and PJF.

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.

PURPOSE

The study aimed to assess the incidence of PJK and PJF in patients treated with prophylactic polymethylmethacrylate (PMMA) cement augmentation at the uppermost instrumented vertebrae (UIV) and rostral adjacent vertebrae (UIV+1).

STUDY DESIGN/SETTING

This is a retrospective cohort-matched surgical case series at an academic institutional setting.

PATIENT SAMPLE

Eighty-five adult patients over a 16-year enrollment period were identified with long-segment (>5 levels) posterior thoracolumbar instrumented fusions for ASD.

OUTCOME MEASURES

Primary outcomes measures were PJK magnitude and PJF formation. Secondary outcomes measures were spinopelvic parameters, as well as global and regional sagittal alignment.

METHODS

The impact of adjunctive PMMA use in long-segment (≥5 levels) fusion for ASD was assessed in adult patients aged 18 and older. Patients were included with at least one of the following: lumbar scoliosis >20°, pelvic tilt >25°, sagittal vertical axis >5 cm, central sacral vertical line >2 cm, and thoracic kyphosis >60°. The frequency of PJF and the magnitude of PJK were measured radiographically preoperatively, postoperatively, and at maximum follow-up in controls (Group A) and PMMA at the UIV and UIV+1 (Group B).

RESULTS

Eighty-five patients (64±11.1 years) with ASD were identified: 47 control patients (58±10.6) and 38 patients (71±6.8) treated with PMMA at the UIV and UIV+1. The mean follow-up was 27.9 and 24.2 months in Groups A and B, respectively (p=.10). Preoperative radiographic parameters were not significantly different, except the pelvic tilt which was greater in Group A (26.6° vs. 31.4°, p=.03). Postoperatively, the lumbopelvic mismatch was greater in Group B (14.6° vs. 7.9°, p=.037), whereas the magnitude of PJK was greater in controls (9.36° vs. 5.65°, p=.023). The incidence of PJK was 36% (n=17) and 23.7% (n=9) in Groups A and B, respectively (p=.020). The odds ratio of PJK with vertebroplasty was 0.548 (95% confidence interval=0.211 to 1.424). Proximal junctional kyphosis was observed in 6 (12.8%) controls only (p=.031). The UIV+1 angle, a measure of PJK, was significantly greater in controls (10.0° vs. 6.8°, p=.02). No difference in blood loss was observed. No complications were attributed to PMMA use.

CONCLUSIONS

The use of prophylactic vertebral cement augmentation at the UIV and rostral adjacent vertebral segment at the time of deformity correction appears to be preventative in the development of proximal junctional kyphosis and failure.

Revision surgery in proximal junctional kyphosis

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Outcomes of Short Fusion versus Long Fusion for Adult Degenerative Scoliosis: A Systematic Review and Meta-analysis

The objective of this study was to evaluate differences in clinical and radiographic outcomes between short (<3 levels) and long (≥3 levels) fusions in the setting of degenerative lumbar scoliosis. A literature search was performed from six electronic databases. The key terms of "degenerative scoliosis" OR "lumbar scoliosis" AND "fusion" were combined and used as MeSH subheadings. From relevant studies identified, demographic data, complication rates, Oswestry Disability Index (ODI), and radiographic parameters were extracted and the data was pooled and analyzed. Long fusion was associated with comparable overall complication rates to short fusion (17% vs 14%, P = 0.20). There was a significant difference in the incidence of pulmonary complications when comparing short versus long fusion (0.42% vs 2.70%; P = 0.02). No significant difference was found in terms of motor, sensory complications, infections, construct-related or cardiac complications, pseudoarthrosis, dural tears, cerebrospinal fluid (CSF) leak, or urinary retention. A longer fusion was associated with a greater reduction in coronal Cobb angle and increases in lumbar lordosis, but both findings failed to achieve statistical significance. The ODI was comparable across both cohorts. If shorter fusion lengths are clinically indicated, they should be used instead of longer fusion lengths to reduce perioperative time, costs, and some other complications. However, there are no statistically significant differences in terms of radiographically measurable restoration associated with a short or long fusion.

Degenerative lumbar scoliosis patients with proximal junctional kyphosis have lower muscularity, fatty degeneration at the lumbar area

PURPOSE

To assess the lumbar muscle conditions on the incidence of proximal junctional kyphosis (PJK) after long-level correction and instrumentation surgery for degenerative lumbar scoliosis (DLS) patients with a minimum 2-year follow-up.

METHODS

Eighty-four DLS patients undergoing long instrumented fusion surgery (≥ 5 vertebrae) were retrospectively studied. According to the occurrence of PJK at the final follow-up, patients were divided into the PJK group and the Non-PJK group. Patient characteristics, surgical variables and radiographic parameters were analyzed statistically. The lumbar muscularity (cross-sectional area of muscle-disc ratio × 100) and fatty degeneration (signal intensity of muscle-subcutaneous fat ratio × 100) were evaluated on magnetic resonance imaging .

RESULTS

The prevalence of PJK was 20.24%. Gender, age at surgery, body mass index, uppermost instrumented vertebrae level, fusions extending to the sacrum, and levels fused were not significantly different between the groups. Lower bone mineral density, smaller functional cross-sectional area (FCSA) of paraspinal extensor muscles (PSE), higher lean muscle-fat index and total muscle-fat index of PSE, greater preoperative thoracolumbar kyphosis (TLK), smaller preoperative sacral slope (SS), larger preoperative sagittal vertical axis were identified in PJK group. Logistic regression analysis showed that osteoporosis, preoperative TLK > 15°, SS > 24°, FCSA of PSE > 138.75, and total muscle-fat index of PSE > 4.08 were independently associated with PJK. The final follow-up VAS score for back pain was higher, and SRS-22 subcategories of pain, function, self-image, and total score were significantly lower in the PJK group.

CONCLUSION

Osteoporosis, lower lumbar muscularity and higher fatty degeneration, preoperative greater TLK and smaller SS were found to be strongly associated with the presence of PJK in DLS.

Exploratory analysis of predictors of revision surgery for proximal junctional kyphosis or additional postoperative vertebral fracture following adult spinal deformity surgery in elderly patients: a retrospective cohort study

Background

Proximal junctional kyphosis (PJK) following adult spinal deformity (ASD) surgery in elderly patients is markedly influenced by osteoporosis causing additional vertebral fracture and loosening of pedicle screws (PS). This study aimed to investigate the association between mean bone density represented in Hounsfield units (HU) on spinal computed tomography (CT) and revision surgery for PJK or postoperative additional vertebral fracture following ASD surgery in elderly patients.

Methods

The subjects were 54 ASD patients aged 65 years or older who were treated with correction and fusion surgery of four or more levels and could be followed for 2 years or longer. Bone density was measured before surgery using lumbar dual-energy X-ray absorptiometry (DXA) and spinal CT in all patients. The patients were divided into group A (n = 14) in which revision surgery was required for PJK or additional vertebral fracture and group B (n = 40) in which revision surgery was not required. We retrospectively investigated incidences of PJK, additional vertebral fracture, and PS loosening, perioperative parameters, radiographic parameters before and after surgery, and osteoporosis treatment administration rate.

Results

No significant difference was noted in young adult mean (YAM) on DXA between groups A and B, respectively (P = 0.62), but the mean bone densities represented in HU of the T8 (P = 0.002) and T9 (P = 0.01) vertebral bodies on spinal CT were significantly lower in group A, whereas those of the L4 (P = 0.002) and L5 (P = 0.01) vertebral bodies were significantly higher in group A. The incidence of PJK was not significantly different (P = 0.07), but the incidence of additional vertebral fracture was significantly higher in group A (P < 0.001). The incidences of uppermost PS loosening within 3 months after surgery were 71% and 40% in groups A and B, respectively (P = 0.04).

Conclusions

In elderly patients who required revision surgery, the mean bone densities of vertebral bodies at T8 and T9 were significantly lower. The mean bone density represented in HU on spinal CT may be useful for risk assessment of and countermeasures against revision surgery after ASD surgery in elderly patients.

Biomechanical effects of fusion levels on the risk of proximal junctional failure and kyphosis in lumbar spinal fusion surgery

BACKGROUND

Spinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear.

METHODS

A finite element model of the thoracolumbar spine was used. Nine fusion models with pedicle screw systems implanted at the L2-L3, L3-L4, L4-L5, L5-S1, L2-L4, L3-L5, L4-S1, L2-L5, and L3-S1 levels were developed based on the respective surgical protocols. The developed models simulated flexion-extension using hybrid testing protocol.

FINDINGS

When spinal fusion was performed at more distal levels, particularly at the L5-S1 level, the following biomechanical properties increased during flexion-extension: range of motion, stress on the annulus fibrosus fibers and vertebra at the adjacent motion segment, and the magnitude of axial forces on the pedicle screw at the uppermost instrumented vertebra.

INTERPRETATIONS

The results of this study demonstrate that more distal fusion levels, particularly in spinal fusion including the L5-S1 level, lead to greater increases in the risk of proximal junctional kyphosis and failure, as evidenced by larger ranges of motion, higher stresses on fibers of the annulus fibrosus and vertebra at the adjacent segment, and higher axial forces on the screw at the uppermost instrumented vertebra in flexion-extension. Therefore, fusion levels should be carefully selected to avoid proximal junctional kyphosis and failure.

Proximal Junctional Kyphosis Prevention Strategies: A Video Technique Guide

BACKGROUND

Proximal junctional kyphosis (PJK) is a well-recognized complication in patients undergoing posterior instrumented fusion procedures for adult spinal deformity. Strategies that reduce rates of PJK have the potential to improve the safety of these operations and decrease cost by eliminating the need for revision surgery.

OBJECTIVE

To present a set of surgical techniques that can decrease rates of PJK in adults undergoing surgery for spinal deformity.

METHODS

We summarize the use of vertebroplasty, transverse process hooks, terminal rod contouring, and ligament augmentation as means to reduce rates of PJK.

RESULTS

We present PJK prevention strategies and a video technique guide that are safe, technically feasible, and add minimal operative time to these surgical procedures. When applied to appropriate high-risk patients, these techniques have the potential to dramatically reduce rates of PJK, which improves quality of life and decreases the cost associated with this treating adult spinal deformity.

CONCLUSION

PJK prevention strategies represent a critical area for improvement in surgery for adult spinal deformity. We present a summary of techniques that are safe, feasible, and add minimal time to the overall procedure. These techniques warrant investigation in a thoughtful, prospective manner, but are supported by existing data and compelling biomechanical rationale. Our hope is that these strategies can be applied, particularly in high-risk patients, to help reduce rates of PJK.

Cervical sagittal deformity develops after PJK in adult thoracolumbar deformity correction: radiographic analysis utilizing a novel global sagittal angular parameter, the CTPA

PURPOSE

To describe reciprocal changes in cervical alignment after adult spinal deformity (ASD) correction and subsequent development of proximal junctional kyphosis (PJK). This study also investigated these changes using two novel global sagittal angular parameters, cervical-thoracic pelvic angle (CTPA) and the T1 pelvic angle (TPA).

METHODS

Multicenter, retrospective consecutive case series of ASD patients undergoing thoracolumbar three-column osteotomy (3CO) with fusion to the pelvis. Radiographs were analyzed at baseline and 1 year post-operatively. Patients were substratified into upper thoracic (UT; UIV T6 and above) and lower thoracic (LT; UIV below T6). PJK was defined by >10° angle between UIV and UIV + 2 and >10° change in the angle from baseline to post-op.

RESULTS

PJK developed in 29 % (78 of 267) of patients. CTPA was linearly correlated with cervical plumbline (CPL) as a measure of cervical sagittal alignment (R = 0.826, p < 0.001). PJK patients had significantly greater post-operative CTPA and SVA than patients without PJK (NPJK) (p = 0.042; p = 0.021). For UT (n = 141) but not LT (n = 136), PJK patients at 1 year had larger CTPA (4.9° vs. 3.7°, p = 0.015) and CPL (5.1 vs. 3.8 cm, p = 0.022) than NPJK patients, despite similar corrections in PT and PI-LL.

CONCLUSIONS

The prevalence of PJK was 29 % at 1 year follow-up. CTPA, which correlates with CPL as a global analog of cervical sagittal balance, and TPA describe relative proportions of cervical and thoracolumbar deformities. Patients who develop PJK in the upper thoracic spine after thoracolumbar 3CO also develop concomitant cervical sagittal deformity, with increases in CPL and CTPA.

The mechanism in junctional failure of thoraco-lumbar fusions. Part II: Analysis of a series of PJK after thoraco-lumbar fusion to determine parameters allowing to predict the risk of junctional breakdown

PURPOSE

To identify risk factors, in 12 patients with junctional breakdown (JBD) after thoraco-sacral fusions and to test a software locating maximal bending moment on full spine EOS images.

METHODS

Twelve patients underwent long fusions for lumbar degenerative pathologies. Preop EOS images were compared to first postop EOS showing JBD. Parameters analyzed were: spinopelvic parameters [pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA), spinosacral angle (SSA), lordosis, and kyphosis], proximal junctional angle (PJA), odontoid-hip axis angle (ODHA), and CIA. A new software estimated the location of maximum bending moment (M _max) before and after JBD.

RESULTS

All patients except one had a JBD located between T10 and L1, diagnosed at average follow-up of 18.58 months. JBD was a fracture in six patients, severe adjacent disc degeneration in the remaining. Average PI was 52°. PT increased, SS decreased after JBD versus preop (p > 0.05). Average PJA was 34.5°. Global lordosis (GLL), upper lordosis (ULL), L4-S1 lordosis, and thoracic kyphosis (TK) were increased (p < 0.05). Lower lumbar lordosis (LLL), was not increased postJBD (p = 0.6). SVA, SSA, ODHA, and C7 slope were not modified (p > 0.05). CIA average value decreased by 7.5% after JBD. T1-T5 alignment was correlated to C7 slope before (R ² = 0.77075) and after JBD (R ² = 0.85409). ODHA decreased after JBD (p > 0.05). Most JBD occurred at or one level away from preoperative M _max location.

CONCLUSION

This study confirms the importance of harmonious distribution of lumbar (GLL, ULL, and ILL) and thoracic curves (TK, T1-T5 segment) in thoraco-sacral fusions. All patients showed an exaggerated ULL, resulting in a posterior shift and increased lever arm at the thoraco-lumbar junction, leading to JBD.

Spinal pedicle subtraction osteotomy for fixed sagittal imbalance patients

In addressing spinal sagittal imbalance through a posterior approach, the surgeon now may choose from among a variety of osteotomy techniques. Posterior column osteotomies such as the facetectomy or Ponte or Smith-Petersen osteotomy provide the least correction, but can be used at multiple levels with minimal blood loss and a lower operative risk. Pedicle subtraction osteotomies provide nearly 3 times the per-level correction of Ponte/Smith-Petersen osteotomies; however, they carry increased technical demands, longer operative time, and greater blood loss and associated significant morbidity, including neurological injury. The literature focusing on pedicle subtraction osteotomy for fixed sagittal imbalance patients is reviewed. The long-term overall outcomes, surgical tips to reduce the complications and suggestions for their proper application are also provided.

Is a gradual reduction of stiffness on top of posterior instrumentation possible with a suitable proximal implant? A biomechanical study

BACKGROUND CONTEXT

Proximal junctional kyphosis (PJK) is a challenging complication after rigid posterior instrumentation (RI) of the spine. Several risk factors have been described in literature so far, including the rigidity of the cranial aspect of the implant.

PURPOSE

The aim of this biomechanical study was to compare different proximal implants designed to gradually reduce the stiffness between the instrumented and non-instrumented spine.

STUDY DESIGN/SETTING

This is a biomechanical study.

METHODS

Eight calf lumbar spines (L2-L6) underwent RI with a titanium pedicle screw rod construct at L4-L6. The proximal transition segment (L3-L4) was instrumented stepwise with different supplementary implants-spinal bands (SB), cerclage wires (CW), hybrid rods (HR), hinged pedicle screws (HPS), or lamina hooks (LH)-and compared with an all-pedicle screw construct (APS). The flexibility of each segment (L2-L6) was tested with pure moments of ±10.0 Nm in the native state and for each implant at L3-L4, and the segmental range of motion (ROM) was evaluated.

RESULTS

On flexion and extension, the native uninstrumented L3-L4 segment showed a mean ROM of 7.3°. The CW reduced the mean ROM to 42.5%, SB to 41.1%, HR to 13.7%, HPS to 12.3%, LH to 6.8%, and APS to 12.3%. On lateral bending, the native segment L3-L4 showed a mean ROM of 15°. The CW reduced the mean ROM to 58.0%, SB to 78.0%, HR to 6.7%, HPS to 6.7%, LH to 10.0%, and APS to 3.3%. On axial rotation, the uninstrumented L3-L4 segment showed a mean ROM of 2.7°. The CW reduced the mean ROM to 55.6%, SB to 77.8%, HR to 55.6%, HPS to 55.6%, LH to 29.6%, and APS to 37.0%.

CONCLUSIONS

Using CW or SB at the proximal transition segment of a long RI reduced rigidity by about 60% in relation to flexion and extension in that segment, whereas the other implants tested had a high degree of rigidity comparable with APS. Clinical randomized controlled trials are needed to elucidate whether this strategy might be effective for preventing PJK.

Surgical correction of Adult Spinal Deformity in accordance to the Roussouly classification: effect on postoperative mechanical complications

STUDY DESIGN

Single-center, retrospective.

OBJECTIVES

To assess the restoration of ideal sagittal spine shape in accordance to the Roussouly classification and the effect on postoperative mechanical complications. Surgical correction of Adult Spinal Deformity is both challenging and complex. The risk of postoperative complications is considerable, especially mechanical complications requiring revision surgery. Attention has been directed toward defining alignment targets in attempts to minimize these risks, and the Roussouly classification has been proposed as a potential surgical aim.

METHODS

All patients undergoing ASD surgery from 2013-2016 were included at a single, quaternary institute. Successful restoration of Roussouly spine shape was retrospectively assessed, and patients were classified as either "restored" or "non-restored". Cumulative incidence of revision surgery due to mechanical failure was estimated using the Aalen-Johansen estimator, with death as the competing risk. A multivariable proportional odds model was used to estimate the effect of the Roussouly algorithm on revision surgery due to mechanical failure.

RESULTS

We identified a complete and consecutive cohort of 233 patients who were followed for a mean period of 36 (± 14) months. The 2-year cumulative incidence of revision surgery was 28%. Comparing the "restored" to the "non-restored" group, the overall revision rates were high in both groups. However, when adjusting for known cofounders in a multivariable proportional odds analysis, there was an almost fivefold increased odds of revision due to mechanical failure in the "non-restored" group (p = 0.036).

CONCLUSION

Surgical correction of ASD in accordance to the ideal Roussouly spine shape was correlated to a marked and significant decrease in risk of revision surgery due to mechanical failure. Nonetheless, the overall revision risk was elevated in both groups.

LEVEL OF EVIDENCE

Therapeutic III.