Incidence, risk factors and classification of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis

Factors Associated With the Development of and Revision for Proximal Junctional Kyphosis in 440 Consecutive Adult Spinal Deformity Patients

MINI: Proximal junctional kyphosis (PJK) is a common, yet incompletely understood, complication of surgery for adult spinal deformity. We analyzed 440 consecutive adult spinal deformity patients for trends in development of PJK and need for revision surgery. pelvic tilt and thoracic kyphosis were predictive for developing PJK, while radiographic evidence of proximal junctional failure was predictive for proceeding to revision.

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

The aim of this study was to examine which radiographic parameters and surgical strategies are most closely associated with proximal junctional kyphosis (PJK) after adult spinal deformity (ASD) surgery, the need for revision surgery for PJK, and whether these differ based on the upper instrumented vertebra (UIV).

SUMMARY OF BACKGROUND DATA

Multiple parameters are considered when planning correction of ASD. Determining which of these factors contribute to the development of and need for revision surgery for PJK presents a challenging problem.

METHODS

Consecutive patients undergoing long fusion to the pelvis with age >18 years, minimum 6-month follow-up, and adequate radiographs for analysis in a single institution between 2003 and 2011 were included. Along with chart review, measurement of proximal junctional angle (PJA), sagittal balance, and pelvic parameters was performed on preoperative, postoperative, and latest follow-up radiographs. Postoperative radiographs were also examined for signs of PJF.

RESULTS

A total of 440 patients with a mean follow-up of 34 months met inclusion criteria, 159 of whom developed PJK (36%), with 65 requiring revision surgery (41%). Higher preoperative pelvic tilt (PT) (P = 0.018) and postoperative thoracic kyphosis (TK) (P ≤ 0.001) were predictive for development of PJK, whereas hooks at UIV were protective (odds ratio [OR] 0.049). In patients who developed PJK, revision was more frequent in younger patients (P = 0.005) with greater postoperative sagittal vertical axis and PJA (P = 0.029, P = 0.018). PJF with spondylolisthesis, fracture, or instrumentation failure at the UIV had the highest ORs for proceeding to a revision (5.1, 1.6, and 2.2, respectively).

CONCLUSION

TK and PT are important indicators of overall rigidity and reference the ability of the spine to compensate for sagittal plane deformity. Special attention should be paid to these characteristics and to the choice of proximal instrumentation when attempting to prevent PJK. Prevention of radiographically evident PJF may hold the key to reducing the need for revision surgery.

LEVEL OF EVIDENCE

3.

Adult Degenerative Lumbar Scoliosis

Adult degenerative lumbar scoliosis is a 3-dimensional deformity defined as a coronal deviation of greater than 10°. It causes significant pain and disability in the elderly. With the aging of the population, the incidence of adult degenerative lumbar scoliosis will continue to increase. During the past decade, advancements in surgical techniques and instrumentation have changed the management of adult spinal deformity and led to improved long-term outcomes. In this article, the authors provide a comprehensive review of the pathophysiology, diagnosis, and management of adult degenerative lumbar scoliosis. [Orthopedics. 2017; 40(6):e930-e939.].

Orientation of the Upper-most Instrumented Segment Influences Proximal Junctional Disease Following Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective review of a prospective database.

OBJECTIVE

The aim of this study was to define the role of sagittal orientation of the construct at the upper instrumented levels in the development of proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients.

SUMMARY OF BACKGROUND DATA

PJK following ASD surgery remains challenging. The final alignment of the upper instrumented vertebral segments has been proposed as a risk factor for PJK, but has not been fully investigated.

METHODS

ASD patients with 2-year follow-up and long posterior fusion to the pelvis were analyzed. Radiographic measurements included pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), sagittal vertical axis, and two upper-most instrumented vertebra (UIV) parameters: UIV slope (UIV vs. horizontal) and inclination of the proximal-end of the construct. UIV parameters were secondarily evaluated with regard to the compensatory impact of post-PJK increased PT (PREF). A comparison between PJK and non-PJK patients was performed, according to the UIV location (upper thoracic [UT] or thoracolumbar).

RESULTS

A total of 252 patients (mean age, 61.5 years, 83% females) were included. PJK incidence was 56% at 2-years. PJK patients had a greater change in LL and thoracic kyphosis than non-PJK patients. In the UT group, there was no difference in UIV slope for PJK versus non-PJK. However, PJK patients had a smaller inclination of the upper instrumented segments versus vertical (P < 0.001) and the PREF (P = 0.005). Similarly, in the LT group, PJK patients had a posterior inclination versus the vertical (P < 0.001) and the PREF (P = 0.041).

CONCLUSION

Analysis revealed that a more posterior construct inclination was present in patients who developed PJK. These results support previous hypotheses suggesting that PJK may develop in response to excessive spinal realignment. Proper rod contouring, especially at the proximal end, may reduce the risk of PJK.

LEVEL OF EVIDENCE

3.

Proximal Junctional Kyphosis After Posterior Spinal Instrumentation and Fusion in Young Children With Congenital Scoliosis: A Preliminary Report on its Incidence and Risk Factors

STUDY DESIGN

A retrospective study.

OBJECTIVE

To determine the incidence and risk factors of proximal junctional kyphosis (PJK) in young children who underwent posterior instrumented spinal fusion.

SUMMARY OF BACKGROUND DATA

PJK is a well-recognized postoperative complication in adults and adolescents. However, there is a paucity of valid data with regard to PJK in young children with congenital scoliosis (CS) who were treated with posterior correction surgery.

METHODS

This study reviewed the charts and radiographs of a consecutive series of young children with CS who underwent posterior instrumentation and fusion (≥4 levels) from January 2008 to May 2013. The patients were followed up for more than 24 months. Radiographic measurements were made preoperatively and throughout the follow-up period. From sagittal images, the following values were obtained: proximal junctional angle, sagittal vertical axis, pelvic incidence, thoracic kyphosis, lumbar lordosis, and segmental kyphosis.

RESULTS

Totally 113 children were recruited in this study. The average age at surgery was 6.6 years, and the average follow-up period was 48.8 months. PJK occurred in 21 of the 113 patients and were mostly classified as ligamentous failure. In comparison with the non-PJK group, the PJK group showed greater preoperative Thoracic kyphosis (TK) (45.9° vs. 37.3°, P = 0.027), longer fusion levels (6.6 vs. 5.4, P < 0.01), and greater segmental kyphosis (SK) change (30.1° vs. 11.2°, P = 0.002). Both a change in SK greater than 30° and a preoperative TK greater than 40° were independent risk factors associated with PJK. In the PJK group, the average PJA increased by 12.4° at 3 months postoperatively and followed by slight improvement till the final follow-up.

CONCLUSION

This study demonstrates a high rate of PJK in young children after correction surgery for CS. PJK mainly occurs within 3 months postoperatively and its risk factors include preoperative hyperkyphosis, over-correction of kyphosis, and ligamentous failure.

LEVEL OF EVIDENCE

4.

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.

Comparison Between S2-Alar-Iliac Screw Fixation and Iliac Screw Fixation in Adult Deformity Surgery: Reoperation Rates and Spinopelvic Parameters

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The S2-alar-iliac (S2AI) technique has been described as an alternative method for pelvic fixation in place of iliac screws (ISs) in spinal deformity surgery. The objective of this study was to analyze the impact of S2AI screws on radiographical outcomes, including spinopelvic parameters.

METHODS

A retrospective review of 17 patients receiving ISs and 46 patients receiving S2AI screws for correction of adult spinal deformity between 2010 and 2015 with minimum 1-year follow-up was conducted. Patient data on postoperative complications, including reoperation rates and proximal junctional kyphosis (PJK), and radiographical parameters was collected and statistically analyzed.

RESULTS

With mean follow-up of 21.1 months, the overall reoperation rate was significantly lower in the S2AI group than in the IS group (21.7% vs 58.8%, P = .01), but the incidence of PJK was similar (32.6% vs 35.3%, P > .99). Moreover, the time to reoperation in the IS group was significantly shorter than in the S2AI group (P = .001), and the S2AI group trended toward a longer time to reoperation due to PJK (P = .08). There was a significantly higher change in pelvic incidence (PI) in the S2AI group (-6.0°) compared with the IS group (P = .001).

CONCLUSIONS

Compared with the IS technique, the S2AI technique demonstrated a lower rate of overall reoperation, a similar rate of PJK, longer time to reoperation, and possible reduction in PI. Future studies may be warranted to clarify the mechanism of these results and how they can be translated into improved patient care.

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.

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.

Age-Adjusted Alignment Goals Have the Potential to Reduce PJK

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

To explore proximal junctional kyphosis (PJK) as a function of age-adjusted surgical correction goals.

SUMMARY OF BACKGROUND DATA

Recent adult spinal deformity (ASD) studies show that alignment targets are age-specific. Despite recognizing age and malalignment as PJK risk factors, no study has assessed the age-specific effects of alignment on PJK.

METHODS

ASD patients with fusions to the pelvis were included and stratified into three groups: young adults (YA <40 years old), middle aged (MA: 40-65 years old), and the elderly (ED >65 years old). Analysis of variance compared the groups with respect to 1-year postoperative alignments and 1-year offsets from age-specific alignment targets.

RESULTS

A total of 679 patients were enrolled (mean age = 61 years old, 77% female, body mass index = 28.1). At 1 year postoperatively, there was a significant decrease in pelvic tilt (PT; 29-23°), spinopelvic mismatch (pelvic incidence [PI]-lumbar lordosis [LL]) (28-5°), and sagittal vertical axis (SVA; 110-37 mm); overall incidence of PJK was 45.1%. Stratification by age (YA, n = 28; MA, n = 389; ED, n = 262) revealed an increase in PJK incidence with age: YA = 17.9%, MA = 43.8%, and ED = 50.2% (P < 0.001). PJK patients had smaller postoperative PI-LL mismatches (ED 0.8° vs. 9.8°, MA 3.1° vs. 7.3°) than non-PJK patients, without any significant differences in PT or SVA. Analysis of the postoperative offsets from age-specific norms revealed that PJK patients in the two older subgroups and in the study cohort as a whole were overcorrected as compared to non-PJK patients (PI-LL offset-all: -5.2° vs. 2.8°, MA: -1° vs. +4°, ED: -11° vs. -2°; SVA offset-all: -10 mm vs. 7 mm, MA: -3 mm vs. 10 mm, ED: -18 mm vs. -6 mm). The correlation coefficients between PJK angles and the offsets from age-adjusted objective were small (0.320 for PI-LL, 0.114 for PT, and 0.136 for SVA).

CONCLUSION

Overall, this study suggests that PJK patients were overcorrected when compared to age-adjusted alignment goals. Certainly, elderly patients are subject to independent risk factors for PJK, making the prevention of PJK complex. However, individualized optimization of surgical alignment can improve outcomes. This emphasizes the need for surgeons to incorporate age-specific alignment targets into the standard preoperative planning process.

LEVEL OF EVIDENCE

3.

Correction of severe spinopelvic mismatch: decreased blood loss with lateral hyperlordotic interbody grafts as compared with pedicle subtraction osteotomy

OBJECTIVE

Pedicle subtraction osteotomy (PSO) provides extensive correction in patients with fixed sagittal plane imbalance but is associated with high estimated blood loss (EBL). Anterior column realignment (ACR) with lateral graft placement and sectioning of the anterior longitudinal ligament allows restoration of lumbar lordosis (LL). The authors compare peri- and postoperative measures in 2 groups of patients undergoing correction of a sagittal plane imbalance, either through PSO or the use of lateral lumbar fusion and ACR with hyperlordotic (20°–30°) interbody cages, with stabilization through standard posterior instrumentation in all cases.

METHODS

The authors performed a retrospective chart review of cases involving a lumbar PSO or lateral lumbar interbody fusion and ACR (LLIF-ACR) between 2010 and 2015 at the authors’ institution. Patients who had a PSO in the setting of a preexisting fusion that spanned more than 4 levels were excluded. Demographic characteristics, spinopelvic parameters, EBL, operative time, and LOS were analyzed and compared between patients treated with PSO and those treated with LLIF-ACR.

RESULTS

The PSO group included 14 patients and the LLIF-ACR group included 13 patients. The mean follow-up was 13 months in the LLIF-ACR group and 26 months in the PSO group. The mean EBL was significantly lower in the LLIF-ACR group, measuring approximately 50% of the mean EBL in the PSO group (1466 vs 2910 ml, p < 0.01). Total LL correction was equivalent between the 2 groups (35° in the PSO group, 31° in the LLIF-ACR group, p > 0.05), as was the preoperative PI-LL mismatch (33° in each group, p > 0.05) and the postoperative PI-LL mismatch (< 1° in each group, p = 0.05). The fusion rate as assessed by the need for reoperation due to pseudarthrosis was lower in the LLIF-ACR group but not significantly so (3 revisions in the PSO group due to pseudarthrosis vs 0 in the LLIF-ACR group, p > 0.5). The total operative time and LOS were not significantly different in the 2 groups.

CONCLUSIONS

This is the first direct comparison of the LLIF-ACR technique with the PSO in adult spinal deformity correction. The study demonstrates that the LLIF-ACR provides equivalent deformity correction with significantly reduced blood loss in patients with a previously unfused spine compared with the PSO. This technique provides a powerful means to avoid PSO in selected patients who require spinal deformity correction.

Radiographic Predictors for Mechanical Failure After Adult Spinal Deformity Surgery: A Retrospective Cohort Study in 138 Patients

STUDY DESIGN

Retrospective cohort study at a single institution.

OBJECTIVE

We aimed at estimating the rate of revision procedures and identify radiographic predictors of mechanical failure after adult spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

Mechanical failure rates after adult spinal deformity surgery range 12% to 37% in literature. Although the importance of spinal and spino-pelvic alignment is well documented for surgical outcome and ideal alignment has been proposed as sagittal vertical axis (SVA) < 5 cm, pelvic tilt < 20° and lumbar lordosis (LL) = pelvic incidence ± 9°, the role of radiographic sagittal spine parameters and alignment targets as predictors for mechanical failure remains uncertain.

METHODS

A consecutive cohort of adult spinal deformity patients who underwent corrective surgery with at least 5 levels of instrumentation between January 2008 and December 2012 at a single tertiary spine unit were followed for at least 2 years. Time to death or failure was recorded and cause-specific Cox regressions were applied to evaluate predictors for mechanical failure or death.

RESULTS

A total of 138 patients with median age of 61 years were included for analysis. Follow up ranged 2.1 to 6.8 years. In total 47% had revision and estimated failure rates were 16% at 1 year increasing to 56% at 5 years. A multivariate analysis adjusting for age at surgery showed increased hazard of failure from LL change > 30°, postoperative TK > 50°, and SS ≤30°. LL change was mostly because of 3-column osteotomy and ending the instrumentation at L5 or S1 increased the hazard of failure more than 6 fold compared with more cranial lumbar levels.

CONCLUSION

Mechanical failure rate was 47% after adult spinal deformity corrective surgery. LL change > 30°, postoperative TK > 50°, and postoperative SS ≤30° were independent radiographic predictors associated with increased hazard of failure.

LEVEL OF EVIDENCE

4.

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.

Surgical and Radiographic Outcomes After Pedicle Subtraction Osteotomy According to Surgeon's Experience

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The aim of this study was to evaluate and compare the surgical, radiographic, and clinical outcomes of pedicle subtraction osteotomy (PSO) according to surgeon's experience.

SUMMARY OF BACKGROUND DATA

Although PSO has been widely used to correct spinal deformities, it still remains technically demanding procedure with high complications.

METHODS

Comparative analysis of 40 consecutive patients treated with lumbar PSOs was performed. According to time period, the former and latter 20 patients were divided into group 1 and group 2, respectively. Patients' demographic data, operative, radiographic/clinical outcomes, and complications were compared between the groups.

RESULTS

Baseline characteristics and preoperative radiographic parameters were not different between the groups. Significant reductions of operative time (569.6 vs. 392.0 minutes, P = 0.000), surgical bleeding (1777.5 vs. 949.5 mL, P = 0.002), and transfused volume of red blood cell (1232.6 vs. 864.1 mL, P = 0.041) in group 2 were observed. Postoperative sagittal vertical axis was significantly different between the groups (40.1 and -3.6 mm, groups 1 and 2, respectively, P = 0.008), and the difference was sustained to the ultimate follow-up (59.4 vs. 13.2 mm, P = 0.003). There was a difference regarding the amount of curve correction by PSO, which was significantly greater in group 2 (25.7° vs. 35.8°, P = 0.023). Intraoperative complications (7 vs. 1, P = 0.019) were significantly lower in group 2. Total complications (20 vs. 10, P = 0.070), postoperative transient neurologic deficit (2 vs. 1), and revision surgery (4 vs. 3) were also lower in group 2, without statistical significance. The amount of the improvement of SRS-22 score was not different between the groups (P = 0.395).

CONCLUSION

PSO may be performed in patients with fixed sagittal imbalance with an acceptable rate of complications after about 20 cases. With acquisition of surgical experiences, surgeons could perform PSO more effectively and safely.

Proximal junctional kyphosis in adult spinal deformity with long spinal fusion from T9/T10 to the ilium

BACKGROUND

Proximal junctional kyphosis (PJK) is a common complication after corrective long spinal fusion for adult spinal deformity. Although some reports evaluated PJK after corrective long spinal fusion, there is no report about analysis of PJK cases in the same fusion area. The purpose of this study to investigated the incidence of and risk factors for PJK in adults undergoing long spinal fusion from the distal thoracic vertebrae (T9/T10) to the ilium.

METHODS

We enrolled 56 adult patients (>40 years of age) who underwent posterior corrective surgery with same fusion area from T9 or T10 to the ilium for spinal deformity. Pre- and postoperative radiographic measurements included the sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), and pelvic incidence minus LL (PI-LL). The Oswestry disability index (ODI) was used to evaluate patient outcomes preoperatively and one year after surgery. We analyzed the incidence for PJK and compared PJK and non-PJK cases.

RESULTS

PJK at the final follow-up occurred in 19 of 56 (33.9%) patients. The mean age and ODI were not significantly different between the PJK and non-PJK groups. Both two groups had good spinopelvic sagittal alignment after surgery in terms of SVA and PI-LL. Only three cases required revision surgery for symptomatic PJK. Three cases had history of rheumatoid arthritis and/or total hip arthroplasty surgery.

CONCLUSIONS

The incidence of PJK was 33.9%, and ODI was not significantly different between the PJK and non-PJK groups. Symptomatic PJK was only three cases and all of them had lower extremity joint disorders. We should pay attention also lower extremity joint to prevent symptomatic PJK at the lower thoracic level.

Proximal Junctional Kyphosis Following Posterior Hemivertebra Resection and Short Fusion in Children Younger Than 10 Years

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate whether proximal junctional kyphosis (PJK) or obvious proximal junctional angle (PJA) changes in the sagittal plane develops following short fusion in children younger than 10 years of age with congenital scoliosis, and to investigate the possible risk factors.

SUMMARY OF BACKGROUND DATA

PJK following long spinal fusion in adolescents and adults is a serious postoperative complication. Although the same problem may occur in patients with early-onset scoliosis who have undergone spine fusion, few studies have been reported any relationship between PJK and spinal fusion in young children with congenital scoliosis.

MATERIALS AND METHODS

Thirty-seven children treated in a single institution between 1998 and 2010 were reviewed retrospectively. The inclusion criteria included (1) younger than 10 years of age at the time of operation; (2) simple congenital deformity; (3) hemivertebra treated by posterior hemivertebrectomy with short fusion at a maximum of 5 motion segments; and (4) minimum follow-up for 2 years. The PJA from the caudal endplate of the upper instrumented vertebra (UIV) to the cephalad endplate of the vertebra adjacent to the UIV, thoracic kyphosis (T5-T12), lumbar lordosis (T12-S1), global sagittal balance, and magnitude of scoliosis of the major curves and upper compensated curves were measured on lateral radiographs. PJK was defined by a PJA>10 degrees during the follow-up and at least 10 degrees greater than the preoperative or early postoperative measurement. Wilcoxon tests were performed for statistical analysis.

RESULTS

PJK occurred in 7 of 37 patients (18.9%), during an average of 4.5±3.2 years of follow-up (2-12 y). The UIV level of children with PJK was on T9 in 4 patients, and T11, T12, and L1 in 1. Screw malposition at UIV was confirmed by postoperative computed tomography images in 6 patients. Only 1 patient with a screw deviation did not develop PJK during the follow-up period. None of the patients with PJK was symptomatic, and no patients required revision surgery because of PJK. PJK occurred and progressed during the first 6 months after surgery followed by almost no progression or slight improvement in patients that could be followed up beyond 6 months postoperatively; in association with an increase of the lumbar lordosis.

CONCLUSIONS

PJK occurred in pediatric patients with simple congenital deformities following hemivertebrectomy and short fusion. PJK was more common in patients with (1) greater immediately postoperative segmental kyphosis and PJA; (2) screw malposition on the UIV; and (3) hemivertebra located on the lower thoracic or the thoracolumbar region.

What Is the More Appropriate Proximal Fusion Level for Adult Lumbar Degenerative Flat Back?

OBJECTIVE

To determine the optimal proximal fusion level after long instrumented fusion to the sacrum for lumbar degenerative flat back.

METHODS

Data from 70 patients with lumbar degenerative flat back were reviewed retrospectively. Three groups were designated according to the upper instrumented vertebrae (UIV): group 1 (UIV = T10 or above), group 2 (UIV = T11-12), and group 3 (UIV = L1 or below). Pre- and postoperative pelvic parameters, degree of correction, and prevalence of proximal junctional kyphosis (PJK) and its risk factors were evaluated.

RESULTS

The prevalence of PJK was 27.1% (average 35.5 months of follow-up). Preoperative pelvic incidence (PI) and sacral slope (SS) in group 1 were higher in the PJK group than in the non-PJK group (P = 0.03 and P = 0.001, respectively). Preoperative thoracolumbar (TL) in group 3 was higher in the PJK group than in the non-PJK group (P = 0.01). Postoperative pelvic tilt (PT) was lower (<20°) in the non-PJK group than in the PJK group (P = 0.025 in group 3). Postoperative TL in group 3 was lower than in the non-PJK group (P = 0.024).

CONCLUSIONS

If the PI is ≥50°, TL kyphosis is ≥5°, and SS is ≥20°, the UIV should be raised above T10 up to the midthoracic level. If the PI is ≥50°, SS is ≤20°, and thoracic kyphosis (TK) is normal despite TL kyphosis, the UIV should be at T10. Even if the PI is ≥50°, TK is normal, and there is no TL kyphosis, the UIV should be set at L1 or below. Regardless of the UIV, the postoperative PT should be ≤20°.

Impact of anchor type on porcine lumbar biomechanics: Finite element modelling and in-vitro validation

BACKGROUND

Rigid posterior implants used for spinal stabilization can be anchored to the vertebrae using pedicle screws or screws combined with transverse process hooks. In the present study, a finite element model of a porcine lumbar spine instrumented with screws and hooks is presented and validated.

METHODS

The porcine lumbar spine model was validated using in-vitro measurements on six porcine specimens. Validation metrics included intervertebral rotations (L1 to L6) and nucleus pressure in the topmost cranial instrumented disc. The model was used to compare the biomechanical effect of anchor types.

FINDINGS

Good agreement was observed between the model and validation experiments. For upper transverse hooks construct, intervertebral rotations increased at the upper instrumented vertebra and decreased at the adjacent level. Additionally, nucleus pressures and stress on the annulus decreased in the adjacent disc and increased in the upper instrumented disc. The pull-out forces predicted for both anchor configurations were significantly lower than the pull-out strength found in the literature.

INTERPRETATION

These numerical observations suggest that upper transverse process hooks constructs reduce the mobility gradient and cause less stress in the adjacent disc, which could potentially reduce adjacent segment disease and proximal junction kyphosis incidence without increasing the risk of fixation failure. Future work needs to assess the long-term effect of such constructs on clinical and functional outcomes.

Walking balance and compensatory gait mechanisms in surgically treated patients with adult spinal deformity

BACKGROUND CONTEXT

Gait patterns and their relationship to demographic and radiographic data in patients with adult spinal deformity (ASD) have not been fully documented.

PURPOSE

This study aimed to assess gait pattern in patients with ASD and the effect of corrective spinal surgery on gait.

DESIGN/SETTING

This is a prospective case series.

PATIENT SAMPLE

The gait patterns of 33 consecutive women with ASD (age 67.1 years; body mass index [BMI] 22.5±2.5 kg/m², Cobb angle 46.8±18.2°, coronal vertical axis [CVA] 1.5±3.7 cm, C7 sagittal vertical axis [SVA] 9.1±6.4 cm, pelvic incidence minus lumbar lordosis [PI-LL] 38.2±22.1°, and lean volume of the lower leg, 5.5±0.6 kg) before and after corrective surgery were compared with those of 33 age- and gender-matched healthy volunteers.

OUTCOME MEASURES

Scoliosis Research Society Patient Questionnaire (SRS22r), Oswestry Disability Index (ODI), and forceplate analysis.

METHODS

All subjects underwent gait analysis on a custom-built forceplate using optical markers placed on all joints and spinal processes. Dual X-ray absorptiometry scores were used to calculate the lean composition of the lower legs. Subjects with ASD were followed for at least 2 years post operation.

RESULTS

Preop mean values showed that patients with ASD had a significantly worse gait velocity (54±10 m/min vs. 70.7±12.9 m/min, p<.01) and stride (97.8±13.4 cm vs. 115.3±15.1 cm, p<.01), but no difference was observed in the stance-to-swing ratio. The right and left ground reaction force vectors were also discordant in the ASD group (vertical direction; r=0.84 vs. r=.97, p=.01). The hip range of motion (ROM) was also significantly decreased in ASD. Correlation coefficient showed moderate correlations between the preoperative gait velocity and the gravity line (GL), PI, ROM of the lower extremity joints, and lean volume, and between the stride and the lean volume, GL, and PI-LL. Gait pattern, stride, and velocity all improved significantly in the patients with ASD after surgery, but were still not as good as in healthy volunteers. The SRS22r satisfaction domain correlated moderately with postoperative gait velocity (r=0.34).

CONCLUSIONS

The patients with ASD had an asymmetric gait pattern and impaired gait ability compared with healthy volunteers. Gait ability correlated significantly with the GL, spinopelvic alignment, lower extremity joint ROM, and lean volume. The surgical correction of spinopelvic alignment and exercises to build muscle strength may improve the gait pattern and ability in patients with ASD.

Mismatch Between Proximal Rod Contouring and Proximal Junctional Angle: A Predisposed Risk Factor for Proximal Junctional Kyphosis in Degenerative Scoliosis

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate whether the mismatch between proximal junctional angle (PJA) and the proximal rod contouring contributed to the occurrence of postoperative proximal junctional kyphosis (PJK) in degenerative scoliosis.

SUMMARY OF BACKGROUND DATA

PJK is one of the complications in the treatment of degenerative scoliosis, the postoperative PI-LL mismatch and the increased rod stiffness are supposed to be the etiology of PJK. However, the impact of rod contouring on PJK has not been fully illustrated.

METHODS

A retrospective study was performed on 27 consecutive degenerative scoliosis patients (three males and 24 females) who underwent corrective surgery with more than 2-year follow-up. Radiographic parameters included proximal rod contouring angle (PRCA) and PJA at the three time-points. The subjects were divided into two groups: PJK group and non-PJK group with the definition of PJK as a PJA more than 10°. The mismatch between PRCA and post-op PJA, defined as the difference between PRCA and postop PJA of more than 5°, was then compared with PJK and non-PJK group.

RESULTS

The patients' mean age was 60.48 ± 6.47 years old with a mean Cobb angle of 40.89 ± 14.33°. Twelve patients, with a mean PJA of 18.67 ± 5.31° at the last followup, were stratified into the PJK group, while the remaining 15 patients, with a mean PJA of 5.33 ± 2.47, were placed into the non-PJK group. A significant difference in the mismatch between post-op PJA and PRCA was observed between PJK and non-PJK group (8.83 ± 5.07° vs. 4.07 ± 2.91°, P = 0.005). Meanwhile the difference of mismatch between preop PJA and PRCA showed no statistical significance (5.16 ± 4.24° vs. 3.00 ± 2.48°, P = 0.109).

CONCLUSION

Mismatch between rod contouring and postoperative proximal spinal curve may be a predisposed risk factor for PJK in degenerative scoliosis.

LEVEL OF EVIDENCE

4.

Semitendinosus Graft for Interspinous Ligament Reinforcement in Adult Spinal Deformity

Proximal junctional kyphosis is an increasingly recognized complication following long-segment posterior spinal fusion for adult spinal deformity. The authors describe a novel technique for interspinous ligament reinforcement at the proximal adjacent levels using a cadaveric semitendinosus tendon graft secured with an Ethibond No. 2 double filament (Ethicon, Somerville, New Jersey) via the Krackow suture weave. A retrospective review identified 4 patients who had received this graft. No proximal junctional kyphosis was seen at a mean short-term follow-up of 5.5 months. Interspinous ligament reinforcement at the proximal adjacent level with a cadaveric semitendinosus tendon graft is a feasible strategy for preventing proximal junctional kyphosis. [Orthopedics. 2017; 40(1):e206-e210.].

Results of Revision Surgery for Proximal Junctional Kyphosis Following Posterior Segmental Instrumentation: Minimum 2-Year Postrevision Follow-Up

STUDY DESIGN

A retrospective cohort study.

OBJECTIVES

The aim of this study was to evaluate radiographic and patient-reported outcomes at minimum 2 years after revision surgery for proximal junctional kyphosis (PJK), correlating these results with PJK etiology.

SUMMARY OF BACKGROUND DATA

There are no studies detailing the results of revision surgery for PJK following posterior segmental instrumentation.

METHODS

Thirty-two consecutive patients treated with revision surgery after PJK above posterior fusions (25 women/7 men, average age at surgery 60.6 yrs) were reviewed for radiographic and patient-reported outcomes (mean follow-up, 4.5 yrs; range, 2-10 yrs). Patients were subdivided into fracture (F) and nonfracture (NF) groups on the basis of PJK etiology.

RESULTS

Radiographic severity of PJK improved significantly with revision surgery and was maintained at ultimate follow-up (P < 0.001). However, initial sagittal vertical axis (SVA) correction was not maintained through ultimate follow-up (P = 0.04). There were significant postrevision improvements in mean Oswestry scores (P < 0.001) and SRS total scores (P < 0.001) in all patients. In patients with pelvic incidence-lumbar lordosis (PI-LL) mismatch < 11°, final PJK measurement was smaller than in patients with mismatch ≥11° (9.4° vs. 19.8°, P = 0.009). Six patients (19%) developed new postrevision PJK, with two (6%) requiring additional surgery. Patients who sustained PJK through a fracture had greater improvements in Oswestry (P = 0.004), total SRS (P = 0.04), pain (P < 0.001), and satisfaction (P = 0.05) scores, although the fracture patients had less maintained SVA correction (P = 0.002).

CONCLUSION

Revision surgery for PJK following posterior instrumentation achieved acceptable radiographic and clinical outcomes at minimum 2-year follow-up. Patients with PI-LL mismatch <11° experienced more ultimate PJK correction than patients with mismatch ≥11°. Although the NF group experienced more sustained correction of sagittal balance, the F group reported greater improvements in patient-reported outcomes. Ultimate clinical outcomes after revision surgery for PJK were similar between patients with and without compression fractures.

LEVEL OF EVIDENCE

3.

Teriparatide improves volumetric bone mineral density and fine bone structure in the UIV+1 vertebra, and reduces bone failure type PJK after surgery for adult spinal deformity

We conducted a prospective comparative study of the effect of teriparatide therapy for preventing vertebral-failure-type PJK after reconstructive surgery for adult spinal deformity. Prophylactic teriparatide improved the volumetric bone mineral density and fine bone structure of the vertebra above the upper-instrumented vertebra and reduced the incidence of vertebral-failure-type PJK.

INTRODUCTION

Proximal junctional kyphosis (PJK) is a complication after corrective surgery for spinal deformity. This study sought to determine whether teriparatide (TP) is an effective prophylactic against PJK type 2 (vertebral fracture) in surgically treated patients with adult spinal deformity (ASD).

METHODS

Forty-three patients who started TP therapy immediately after surgery and 33 patients who did not receive TP were enrolled in this prospective case series. These patients were female, over 50, surgically treated for ASD, and followed for at least 2 years. Preoperative and postoperative standing whole-spine X-rays and dual-energy X-ray absorptiometry scans, and multidetector CT images obtained before and 6 months after surgery were used to analyze the bone strength in the vertebra above the upper-instrumented vertebra (UIV+1).

RESULTS

Mean age was 67.9 years. After 6 months of treatment, mean hip-bone mineral density (BMD) increased from 0.721 to 0.771 g/cm² in the TP group and decreased from 0.759 to 0.729 g/cm² in the control group. This percent BMD change between groups was significant (p < 0.05). The volumetric BMD (326 to 366 mg/cm³) and bone mineral content (BMC) (553 to 622 mg) at UIV+1 were also significantly increased in TP group. The bone volume/tissue volume ratio increased from 46 to 54 % in the TP group, and the trabecular bone thickness and number increased by 14 and 5 %, respectively. At the 2-year follow-up, the PJK type 2 incidence was significantly lower in the TP group (4.6 %) than in the control group (15.2 %; p = .02).

CONCLUSIONS

Prophylactic TP treatment improved the volumetric BMD and fine bone structure at UIV+1 and reduced the PJK-type 2 incidence.

Development of Validated Computer-based Preoperative Predictive Model for Proximal Junction Failure (PJF) or Clinically Significant PJK With 86% Accuracy Based on 510 ASD Patients With 2-year Follow-up

STUDY DESIGN

A retrospective review of large, multicenter adult spinal deformity (ASD) database.

OBJECTIVE

The aim of this study was to build a model based on baseline demographic, radiographic, and surgical factors that can predict clinically significant proximal junctional kyphosis (PJK) and proximal junctional failure (PJF).

SUMMARY OF BACKGROUND DATA

PJF and PJK are significant complications and it remains unclear what are the specific drivers behind the development of either. There exists no predictive model that could potentially aid in the clinical decision making for adult patients undergoing deformity correction.

METHODS

Inclusion criteria: age ≥18 years, ASD, at least four levels fused. Variables included in the model were demographics, primary/revision, use of three-column osteotomy, upper-most instrumented vertebra (UIV)/lower-most instrumented vertebra (LIV) levels and UIV implant type (screw, hooks), number of levels fused, and baseline sagittal radiographs [pelvic tilt (PT), pelvic incidence and lumbar lordosis (PI-LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA)]. PJK was defined as an increase from baseline of proximal junctional angle ≥20° with concomitant deterioration of at least one SRS-Schwab sagittal modifier grade from 6 weeks postop. PJF was defined as requiring revision for PJK. An ensemble of decision trees were constructed using the C5.0 algorithm with five different bootstrapped models, and internally validated via a 70 : 30 data split for training and testing. Accuracy and the area under a receiver operator characteristic curve (AUC) were calculated.

RESULTS

Five hundred ten patients were included, with 357 for model training and 153 as testing targets (PJF: 37, PJK: 102). The overall model accuracy was 86.3% with an AUC of 0.89 indicating a good model fit. The seven strongest (importance ≥0.95) predictors were age, LIV, pre-operative SVA, UIV implant type, UIV, pre-operative PT, and pre-operative PI-LL.

CONCLUSION

A successful model (86% accuracy, 0.89 AUC) was built predicting either PJF or clinically significant PJK. This model can set the groundwork for preop point of care decision making, risk stratification, and need for prophylactic strategies for patients undergoing ASD surgery.

LEVEL OF EVIDENCE

3.

Biomechanical analysis of proximal junctional failure following adult spinal instrumentation using a comprehensive hybrid modeling approach

BACKGROUND

Proximal junctional failure is a severe proximal junctional complication following adult spinal instrumentation and involving acute proximal junctional kyphotic deformity, mechanical failure at the upper instrumented vertebra or just above, and/or proximal junctional osseoligamentous disruption. Clinical studies have identified potential risk factors, but knowledge on their biomechanics is still lacking for addressing the proximal junctional failure issues. The objective of this study was to develop comprehensive computational modeling and simulation techniques to investigate proximal junctional failure.

METHODS

A 3D multibody biomechanical model based on a 47year old lumbar scoliosis surgical case that subsequently had traumatic proximal junctional failure was first developed to simulate patient-specific spinal instrumentation (from T11 to S1), compute the postoperative geometry of the instrumented spine, simulate different physiological loads and movements. Then, a highly detailed finite element model of the proximal junctional spinal segment was created using as input the geometry and displacements from the multibody model. It enabled to perform detailed stress and failure analysis across the anatomical structures.

FINDINGS

The simulated postoperative correction and traumatic failure (wedge fracture at upper instrumented vertebra) agreed well with the clinical report (within 2° difference). Simulated stresses around the screw threads (up to 4.7MPa) generated during the instrumentation and the buckling effect of post-operative functional loads on the proximal junctional spinal segment, were identified as potential mechanical proximal junctional failure risk factors.

INTERPRETATION

Overall, we demonstrated the feasibility of the developed hybrid modeling technique, which realistically allowed the simulation of the spinal instrumentation and postoperative loads, which constitutes an effective tool to further investigate proximal junctional failure pathomechanisms.

Economic Impact of Revision Surgery for Proximal Junctional Failure After Adult Spinal Deformity Surgery: A Cost Analysis of 57 Operations in a 10-year Experience at a Major Deformity Center

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To evaluate the economic impact of revision surgery for proximal junctional failures (PJF) after thoracolumbar fusions for adult spinal deformity (ASD).

SUMMARY OF BACKGROUND DATA

PJF after fusions for ASD is a major cause of disability. Although clinical sequelae are described, PJF-revision operation costs are incompletely defined.

METHODS

Consecutive adults who underwent thoracolumbar fusions for ASD (August, 2003 to January, 2013) were evaluated. Inclusion criteria include construct from pelvis to L2 or above and minimum 6 months follow-up after the index ASD operation. Direct costs (surgical supplies/implants, room/care, pharmacy, services) were identified from medical billing data and calculated for index ASD operations and subsequent surgeries for PJF. Not included in direct cost data were indirect costs, charges, surgeon fees, or revision operations for indications other than PJF (i.e., pseudarthrosis). Patients were compared based on the construct's upper-instrumented vertebra: upper thoracic (UT: T1-6) versus thoracolumbar junction (TLjxn: T9-L2).

RESULTS

Of 501 patients, 382 met inclusion criteria. Fifty-one patients [UT:14; TLjxn: 40 at index; average follow-up 32.6 months (6-92 months)] had revisions for PJF, which summed to $3.2 million total direct cost. Average direct cost of index operations for the cohort ($68,294) was significantly greater than PJF-revisions ($55,547). Compared with TLjxn, UT had a significantly higher average cost for index operations ($79,860 vs. $65,868). However, PJF-revision cases were similar in average cost (UT:$60,103; TLjxn:$53,920; P = 0.09). Costs of PJF amounted to an additional 12.1% of the total index surgical cost in 382 patients.

CONCLUSION

Revision operations for PJF after long thoracolumbar fusions for ASD are associated with an average direct cost of $55,547 per case. Revision costs for PJF are similar based on the index procedure's upper-instrumented vertebra level. At a major tertiary center over a 10-year period, PJF came at a very significant economic expense amounting to $3.2 million for 57 cases.

LEVEL OF EVIDENCE

3.

Orthotic treatment of idiopathic hyperkyphosis with Milwaukee brace

BACKGROUND

Hyperkyphosis with unknown reason is common in teenagers and can be corrected by orthotic management.

OBJECTIVES

Investigation of orthotic outcomes by Milwaukee brace.

METHODS

Sixty-one patients with idiopathic hyperkyphosis (> 45 degrees) were given Milwaukee brace before skeletal maturity. Hyperkyphosis was measured during the first visit without brace, in-brace, at the end of full-time and part time duration of treatment. After treatment completion, participants were categorized in two groups: with hyperkyphosis of 45 degrees and less (Group I) and more than 45 degrees (Group II). These groups were compared to interpret the treatment outcomes.

RESULTS

The mean kyphotic curve was 60.1 (SD ± 7.7) and 71 (SD = 10.1) degrees in Group I and II, respectively. The mean kyphotic curve at the time of full time and part time duration of treatment showed no significant difference in patients successfully completed the treatment (P = 0.10) while there was a significant difference between mean kyphotic curve in full time and part time treatment duration for patients with hyperkyphosis of more than 45 degrees (P < 0.05).

CONCLUSIONS

Hyperkyphosis of less than 70 degrees can be treated if the in-brace correction is saved in part-time duration.

Incidence and risk factors for the progression of proximal junctional kyphosis in degenerative lumbar scoliosis following long instrumented posterior spinal fusion

The aim of this study was to identify the prevalence of proximal junctional kyphosis (PJK) in degenerative lumbar scoliosis (DLS) following long instrumented posterior spinal fusion, and to search for predictable risk factors for the progression of junctional kyphosis.In total 98 DLS patients with a minimum 2-year follow-up were reviewed prospectively. According to the occurrence of PJK at the last follow-up, patients were divided into 2 groups: PJK group and non-PJK group. To investigate risk values for the progression of PJK, 3 categorized factors were analyzed statistically: patient characteristics-preoperative data of age, sex, body mass index (BMI), bone mineral density (BMD) were investigated; surgical variables-the most proximal and distal levels of the instrumentation, the number of instrumented levels; pre- and postoperative radiographic parameters include the scoliotic angle, sagittal vertical axis, thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope.PJK was developed in 17 of 98 patients (17.3%) until to the final follow-up and were enrolled as the PJK group, and 81 patients without PJK at final follow-up were enrolled as the non-PJK group. There was no statistically significant difference between the 2 groups in age at operation (P = 0.900). The patient's sex was excluded in statistical analysis because of the predominance of female patients. There were statistically significant difference between the 2 groups in BMI ([25.5 ± 1.7] kg/m in the PJK group and [23.6 ± 1.9] kg/m in the non-PJK group, P < 0.001) and BMD ([-1.4 ± 0.8] g/cm in the PJK group and [-0.7 ± 0.3] g/cm in the non-PJK group, P < 0.001). No specific surgery-related variables were found to be associated with an increased risk of developing PJK, except when the most proximal instrumented vertebrae stopped at thoracolumbar junction (T11-L1). The upper instrumentation vertebrae (UIV) at thoracolumbar junction was more common in the PJK group than that in the non-PJK group (P = 0.007). No preoperative and early postoperative variable did reveal a statistically significant difference between the 2 groups. When included in a multivariate logistic regression model, BMI>25 kg/m, osteoporosis, and UIV at thoracolumbar junction were independently associated with PJK.In conclusion, osteoporosis, obesity, and UIV at thoracolumbar junction are risk factors for the development and progression of PJK in DLS patients following long instrumented posterior spinal fusion. Antiosteoporosis treatment extends the fusion level above the thoracolumbar region and controlling body weight before and after surgery could provide opportunities to reduce the rate of PJK and to improve therapeutic outcomes.

Does Minimally Invasive Percutaneous Posterior Instrumentation Reduce Risk of Proximal Junctional Kyphosis in Adult Spinal Deformity Surgery? A Propensity-Matched Cohort Analysis

BACKGROUND

Proximal junctional kyphosis (PJK) is a known complication after spinal deformity surgery. One potential cause is disruption of posterior muscular tension band during pedicle screw placement.

OBJECTIVE

To investigate the effect of minimally invasive surgery (MIS) on PJK.

METHODS

A multicenter database of patients who underwent deformity surgery was propensity matched for pelvic incidence (PI) to lumbar lordosis (LL) mismatch and change in LL. Radiographic PJK was defined as proximal junctional angle >10°. Sixty-eight patients made up the circumferential MIS (cMIS) group, and 68 were in the hybrid (HYB) surgery group (open screw placement).

RESULTS

Preoperatively, there was no difference in age, body mass index, PI-LL mismatch, or sagittal vertical axis. The mean number of levels treated posteriorly was 4.7 for cMIS and 8.2 for HYB (P < .001). Both had improved LL and PI-LL mismatch postoperatively. Sagittal vertical axis remained physiological for the cMIS and HYB groups. Oswestry Disability Index scores were significantly improved in both groups. Radiographic PJK developed in 31.3% of the cMIS and 52.9% of the HYB group (P = .01). Reoperation for PJK was 4.5% for the cMIS and 10.3% for the HYB group (P = .20). Subgroup analysis for patients undergoing similar levels of posterior instrumentation in the cMIS and HYB groups found a PJK rate of 48.1% and 53.8% (P = .68) and a reoperation rate of 11.1% and 19.2%, respectively (P = .41). Mean follow-up was 32.8 months.

CONCLUSION

Overall rates of radiographic PJK and reoperation for PJK were not significantly decreased with MIS pedicle screw placement. However, a larger comparative study is needed to confirm that MIS pedicle screw placement does not affect 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.

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.

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.

Prevalence and Consequences of the Proximal Junctional Kyphosis After Spinal Deformity Surgery: A Meta-Analysis

The aim of this study was to estimate the prevalence and patient outcomes of proximal junctional kyphosis (PJK) in pediatric patients and adolescents who received surgical interventions for the treatment of a spinal deformity.Literature was searched in electronic databases, and studies were selected by following précised eligibility criteria. Percent prevalence values of the PJK in individual studies were pooled to achieve a weighted effect size under the random effects model. Subgroup and meta-regression analyses were performed to appraise the factors affecting PJK prevalence.Twenty-six studies (2024 patients) were included in this meta-analysis. Average age of the patients was 13.8 ± 2.75 years of which 32 ± 20 % were males. Average follow-up was 51.6 ± 38.8 (range 17 ± 13 to 218 ± 60) months. Overall, the percent prevalence of PJK (95% confidence interval) was 11.02 (10.5, 11.5) %; P < 0.00001 which was inversely associated with age (meta-regression coefficient: -1.607 [-2.86, -0.36]; 0.014). Revision surgery rate in the patients with PJK was 10%. The prevalence of PJK was positively associated with the proximal junctional angle at last follow-up (coefficient: 2.248; P = 0.012) and the change in the proximal junctional angle from surgery to last follow-up (coefficient: 2.139; P = 0.014) but not with preoperative proximal junctional angle.The prevalence of PJK in the children and adolescent patients is 11%. About 10% of those affected require revision surgery.

Clinical Perspective-The Case for Adoption of LLIF

Open surgical procedures have been the mainstay of spinal surgery for decades, but minimally invasive spinal surgery (MIS) has recently gained traction. Translaterally placed cages permit insertion of large cages and promote skeletal realignment and fusion. Lateral surgical procedures with percutaneous skeletal fixation and good fusion allow patients to leave the hospital earlier with fewer complications as compared with open procedures. The challenging learning curve is often a barrier to adoption for surgeons, many of whom believe that their open methods work well. MIS and open surgical procedures are reported to have similar outcomes at 1 year; in the first 6 weeks, patients undergoing open surgery often need blood transfusion, develop infection, and use more narcotics. Spine surgery has been associated with modulus mismatch between osteoporotic bone and titanium and the need for multiple painful and traumatic surgical procedures, and spine surgeons continue the quest to find better ways to do things.

The paravertebral muscle and psoas for the maintenance of global spinal alignment in patient with degenerative lumbar scoliosis

BACKGROUND CONTEXT

Various factors are reported to affect the spinal alignment in degenerative lumbar scoliosis (DLS). Although trunk muscles also appear to affect spinal alignment, the role of the trunk muscles is not yet clear.

PURPOSE

The aim was to elucidate the role of the multifidus (MF) and psoas (PS) in maintaining global spinal alignment in patients with DLS.

STUDY DESIGN

This was a multicenter retrospective matched cohort study.

PATIENT SAMPLE

Surgically treated 60 paired DLS and lumbar spinal stenosis (LSS) female (120 patients), matched for age and body mass index (BMI; DLS age 68.0±6.8 vs. LSS 67.1±8.9 years; BMI 21.6±3.3 vs. 23.2±3.8 kg/m(2)), were included and were followed for at least 2 years.

OUTCOME MEASURES

Spinal alignment, muscle area, and volume were measured from radiographs, magnetic resonance images (MRIs), and whole-body dual-energy X-ray absorptiometry (DXA) scans. Muscle strength was measured by grip power and peak expiratory flow (PEF).

METHODS

As a surrogate of muscle area, we obtained the cross-sectional area (CSA) at the L5-S level from preoperative MRIs.

RESULTS

The MF and PS CSAs were significantly smaller in the DLS group than in the LSS group (MF 477.7±192.5 vs. 779.8±248.6 mm(2), p<.01; PS 692.3±201.2 vs. 943.4±272.4 mm(2), p=.002), whereas percentage of difference between the right and left sides was significantly larger in the DLS group (MF 18.4±30.6 vs. 2.4±3.3%, p<.01; PS 14.4±15.8 vs. 2.1±2.2%, p<.01). In the extremities, there were no significant differences in the left- or right-side lean composition and grip strength or PEF tests between the groups. Correlation coefficient tests showed moderate correlations between the MF average CSA (avCSA) and global spinal alignment and spinopelvic alignment (pelvic incidence-lumbar lordosis; R=-0.37, -0.38) in the DLS group. The MF avCSA was correlated with the postoperative progression of kyphosis at the unfused thoracic vertebrae in the DLS group (R=0.34).

CONCLUSIONS

The CSAs of the MF and PS were significantly smaller in the DLS group. Whole-body DXA showed no significant difference in the lean composition between the groups. There were significant correlations in the DLS patients between the MF CSA and sagittal spinal alignment. These findings suggest the causal relationship between muscles and global spine alignment.

The paraspinal muscles and their role in the maintenance of global spinal alignment. Another wrinkle in an already complex problem

Yagi M, Hosogane N, Watanabe K, Asazuma T, Matsumoto M, Keio Spine Research Group. The paravertebral muscle and psoas for the maintenance of global spinal alignment in patient with degenerative lumbar scoliosis. Spine J 2016:16:451-8 (in this issue).

Prevalence of Poor Bone Quality in Women Undergoing Spinal Fusion Using Biomechanical-CT Analysis

STUDY DESIGN

Retrospective, cross-sectional analysis of vertebral bone quality in spine-fusion patients at a single medical center.

OBJECTIVE

To characterize the prevalence of osteoporosis and fragile bone strength in a spine-fusion population of women with an age range of 50 years to 70 years. Fragile bone strength is defined as the level of vertebral strength below which a patient is at as high a risk of future vertebral fracture as a patient having bone density-defined osteoporosis.

SUMMARY OF BACKGROUND DATA

Poor bone quality--defined here as the presence of either osteoporosis or fragile bone strength--is a risk factor for spine-fusion patients that often goes undetected but can now be assessed preoperatively by additional postprocessing of computed tomography (CT) scans originally ordered for perioperative clinical assessment.

METHODS

Utilizing such perioperative CT scans for a cohort of 98 women (age range: 51-70 yr) about to undergo spine fusion, we retrospectively used a phantomless calibration technique and biomechanical-CT postprocessing analysis to measure vertebral trabecular bone mineral density (BMD) (in mg/cm³) and by nonlinear finite element analysis, vertebral compressive strength (in Newtons, N) in the L1 or L2 vertebra. Preestablished validated threshold values were used to define the presence of osteoporosis (trabecular BMD of 80 mg/cm³ or lower) and fragile bone strength (vertebral strength of 4500 N or lower).

RESULTS

Fourteen percent of the women tested positive for osteoporosis, 27% tested positive for fragile bone strength, and 29% were classified as having poor bone quality (either osteoporosis or fragile bone strength). Over this narrow age range, neither BMD nor vertebral strength were significantly correlated with age, weight, height, or body mass index (P values 0.14-0.97 for BMD; 0.13-0.51 for strength).

CONCLUSION

Poor bone quality appears to be common in women between ages 50 years and 70 years undergoing spinal fusion surgery.

LEVEL OF EVIDENCE

3.

The Clinical Correlation of the Hart-ISSG Proximal Junctional Kyphosis Severity Scale With Health-Related Quality-of-life Outcomes and Need for Revision Surgery

STUDY DESIGN

Retrospective analysis of prospective data.

OBJECTIVE

Evaluate the utility of the Hart-International Spine Study Group proximal junctional kyphosis severity scale (Hart-ISSG PJKSS).

SUMMARY OF BACKGROUND DATA

Proximal junctional kyphosis (PJK) and failure (PJF) are well-described complications after long-segment instrumentation. The Hart-ISSG PJKSS was recently developed and incorporates neurological deficit, pain, instrumentation issues, degree of kyphosis, presence of fracture, and level of upper-most instrumented vertebrae.

METHODS

All adult spinal deformity patients with PJK or PJF were identified from two academic centers over a 7-year period. Health-related quality-of-life (HRQOL) outcomes were prospectively collected: Oswestry Disability Index (ODI), visual analogue scale (VAS) pain, SF-36 questionnaire, and SRS-30 questionnaire. Patients were retrospectively assigned Hart-ISSG PJKSS scores. Correlation between the Hart-ISSG PJKSS and outcomes was assessed with linear regression, Pearson correlation coefficients, and χ² analysis.

RESULTS

A total of 184 cases were included; 21.2% were men and mean age was 65.0 years. Weakness and/or myelopathy were present in 11.4% of patients and 88.6% had pain. Instrumentation issues occurred in 44.0% and 64.1% had PJK-associated fractures. PJK occurred in the upper thoracic spine in 21.7% of cases. Mean PJKSS score was 5.9. The Hart-ISSG PJKSS was significantly and strongly associated with ODI (P < 0.001, r = 0.611), VAS pain (P < 0.001, r = 0.676), SRS-30 function (P < 0.001, r = -0.401), SRS-30 mental health (P < 0.001, r = -0.592), SRS-30 self-image (P < 0.001, r = -0.511), SRS-30 satisfaction (P < 0.001, r = -0.531), and SRS-30 pain (P < 0.001, r = -0.445). Higher scores were associated with higher proportion of patients undergoing revision surgery (P < 0.001); scores of 9 to 11 and 12 to 15 underwent revision 96.0% and 100.0% of the time, respectively.

CONCLUSION

The Hart-ISSG PJKSS was strongly correlated with validated functional outcomes and higher scores were associated with higher rates of revision surgery. The Hart-ISSG PJKSS may be a useful clinical tool in the treatment of patient with PJK.

LEVEL OF EVIDENCE

3.

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.

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.

Assessment of impact of standing long-cassette radiographs on surgical planning for lumbar pathology: an international survey of spine surgeons

OBJECT

The associations among global spinal alignment, patient-reported disability, and surgical outcomes have increasingly gained attention. The assessment of global spinal alignment requires standing long-cassette anteroposterior and lateral radiographs; however, spine surgeons routinely rely only on short-segment imaging when evaluating seemingly isolated lumbar pathology. This may prohibit adequate surgical planning and may predispose surgeons to not recognize associated pathology in the thoracic spine and sagittal spinopelvic malalignment. The authors used a case-based survey questionnaire to evaluate if including long-cassette radiographs led to changes to respondents' operative plans as compared with their chosen plan when cases contained standard imaging of the involved lumbar spine only.

METHODS

A case-based survey was distributed to AOSpine International members that consisted of 15 cases of lumbar spine pathology and lumbar imaging only. The same 15 cases were then shuffled and presented a second time with additional long-cassette radiographs. Each case required participants to select a single operative plan with 5 choices ranging from least to most extensive. The cases included 5 “control” cases with normal global spinal alignment and 10 “test” cases with significant sagittal and/or coronal malalignment. Mean scores were determined for each question with higher scores representing more invasive and/or extensive operative plans.

RESULTS

Of 712 spine surgeons who started the survey, 316 (44%) completed the entire series, including 68% of surgeons with spine fellowship training and representation from more than 40 countries. For test cases, but not for control cases, there were significantly higher average surgical invasiveness scores for cases presented with long-cassette radiographs (4.2) as compared with those cases with lumbar imaging only (3.4; p = 0.002). The addition of long-cassette radiographs resulted in 82.1% of respondents recommending instrumentation up to the thoracic spine, a 23.2% increase as compared with the same cases presented with lumbar imaging only (p = 0.008).

CONCLUSIONS

This study demonstrates the importance of maintaining a low threshold for performing standing long-cassette imaging when assessing seemingly isolated lumbar pathology. Such imaging is necessary for the assessment of spinopelvic and global spinal alignment, which can be important in operative planning. Deformity, particularly positive sagittal malalignment, may go undetected unless one maintains a high index of suspicion and obtains long-cassette radiographs. It is recommended that spine surgeons recognize the prevalence and importance of such deformity when contemplating operative intervention.

Prevention of Acute Proximal Junctional Fractures After Long Thoracolumbar Posterior Fusions for Adult Spinal Deformity Using 2-level Cement Augmentation at the Upper Instrumented Vertebra and the Vertebra 1 Level Proximal to the Upper Instrumented Vertebra

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To evaluate efficacy of proximal junction fracture (PJF) prevention in adult spinal deformity (ASD) using 2-level cement augmentation at the construct's proximal extent.

SUMMARY OF BACKGROUND DATA

Prevention of PJF after thoracolumbar fusions is critical because they may result in neurological injury. Cement augmentation of constructs' proximal vertebrae is postulated to decrease PJF.

METHODS

Patients with ASD after PSF from pelvis to thoracolumbar junction with 6 months or more follow-up were retrospectively studied. Demographics, deformity radiographical parameters, and health-related quality of life outcomes (HRQoL) scores were compared with patients with no cement, 2-level cement augmentation at upper instrumented vertebra (UIV) and vertebra 1 level proximal to UIV (UIV+1), and cement at another location ("Other"). Revision surgery for PJF was primary outcome. Univariable and multivariable logistic regression analyses were used for statistical analysis.

RESULTS

51 patients [female-29; male-22; average age: 65 yr (33-82)] met inclusion criteria (2-level-19; no-cement-23; "Other"-9). Average follow-up (mo) was longer for no-cement (25 ± 15) and "Other" (20 ± 16) than 2-level (15 ± 8) (P = 0.06). All perioperative radiographical parameters were similar, save first postoperative thoracic kyphosis and lumbopelvic mismatch. Compared with 2-level cement, non-2-level cement had significantly more revisions for PJF (0% vs. 19%; P = 0.02). After UIV adjustment, risks of PJF revision surgery were 13.1 times higher for "Other" (95% CI: 0.5-346.5, P = 0.12) and 9.2 times higher (95% CI: 0.4-239.1, P = 0.18) for no-cement. All HRQoL scores improved in 2-level cement; only back/leg pain significantly improved in non-2-level cement. Postoperative Oswestry Disability Index was significantly less in 2-level cement.

CONCLUSION

The use of 2-level cement augmentation (UIV and UIV+1) in PSF from pelvis to thoracolumbar junction for ASD is associated with a decreased rate of acute proximal junctional fractures and associated revision surgeries. As only associations can be demonstrated from this study's design, prospective investigations with larger, consecutive cohorts should be performed to explore causal relationships.

LEVEL OF EVIDENCE

3.