Elsevier

The Spine Journal

Volume 17, Issue 10, October 2017, Pages 1499-1505
The Spine Journal

Clinical Study
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

https://doi.org/10.1016/j.spinee.2017.05.015Get rights and content

Abstract

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.

Introduction

Proximal junctional kyphosis (PJK) is a recognized postsurgical phenomenon after spinal fusion in both the treatment of adolescent [1], [2], [3] and adult [1], [4] idiopathic scoliosis, as well as after long-segment instrumented fusion in treating adult spinal deformity (ASD). Proximal junctional kyphosis occurs at the rostral junction between the fixed instrumented spinal segment and the mobile vertebral levels above. The prevalence of PJK varies greatly, owed in part to the disagreement in minimum kyphotic angulation that meets the criteria for PJK [5], [6]. One recent study by Yagi et al. defined PJK as greater than 10° of kyphosis between the lower end plate of the uppermost instrumented vertebra (UIV) and the upper end plate of the adjacent vertebral segment above (UIV+1) [6]. Junctional stress resulting in mild ventral wedging of the vertebral body, loss of disc height, and disruption of the posterior tension band all contribute to PJK. Postoperative refractory pain and loss of correction resulting in reoperation is often termed proximal junctional failure (PJF) [7]. A prevalence of 17% to 40% has been reported for PJK, owing to minor variations in definition of PJK and study design [1], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]. In one large study, Kim et al. found a 39% prevalence of PJK across a 7-year duration, although the vast majority of all cases occur early in the first year [4].

The risk factors for PJF identified in prior observational cohort studies include old age, increased body mass index, and osteoporosis [4], [7], [19], [20]. More recently, radiographic features have been the primary focus: large corrections in the sagittal vertical axis (SVA), increased preoperative and postoperative thoracic kyphosis (TK), increased postoperative lumbar lordosis (LL) [13], and larger corrections in the coronal plane are part of a growing list of risk factors for PJK. Surgical techniques linked to a stiffer construct have been associated with a higher PJK rate: fusion to the sacrum, pedicle screw use, combined anteroposterior (AP) fusion, and pedicle screw use at the UIV [13]. Anteroposterior fusion has been observed as a greater risk factor at the proximal end of the construct, and is likely a result of the increased difference in stiffness between the screw-rod construct and the rostral adjacent vertebra (UIV+1), resulting in larger junctional forces [4].

Importantly, PJK may not achieve clinical relevance and go untreated. Loss of correction or development of a compression fracture resulting in surgical therapy is a PJF and treated by proximal extension of the instrumented fusion [4], [12], [14], [21], [22], [23], [24]. Lengthening of the fusion construct either above the apex of the TK or to the upper thoracic spine proximally [25], the use of hooks at the UIV [26], selection of a proximal vertebral level with a small UIV angle [27], and using preoperative imaging to determine a stable vertebral level are sound methods to lower the incidence of PJK [28].

One surgical technique that may mitigate the development of PJK and PJF is the use of prophylactic vertebroplasty (PV) with polymethylmethacrylate (PMMA) [29], [30], [31], [32]. The placement of PMMA in the UIV increases pedicle screw pullout strength and increases the overall construct stiffness [33]. However, fusion alone in a long-segment construct has been thought to increase stress at the UIV+1. Cement augmentation at the UIV alone increases the stiffness of the proximal construct even further, further loading the UIV+1 [7]. This can increase the risk of PJK or compression fractures at the UIV+1 or more rostral levels [34]. In contrast, PV at the UIV and UIV+1 may buffer axial compression forces and protect the UIV+1 from fracture by spreading adjacent-level forces over an additional segment, thereby stress-shielding the UIV+1 and intervening disc [7].

Moreover, recent biomechanical evidence confirms that PV at the UIV alone places the UIV+1 at a higher risk of compression fracture by redundantly reinforcing the already rigid and immobile UIV level, contributing to additional fracture risk [7]. Another biomechanical study demonstrates the biomechanical advantage to PV at the UIV and UIV+1 [7]. Two-level PV was shown to be 17% more effective, observing significantly fewer fractures [7].

In prior clinical practice, Theologis and Burch evaluated cement augmentation at the UIV and UIV+1 and showed that PV lowered the rate of revision surgery for PJK compared with controls [35]. Similarly, Hart et al. found a 15% reduction of PJF compared with patients not treated with PV [23]. More recently, Martin et al. found that patients treated with two-level PV at the UIV and UIV+1 developed PJK and PJF in 8% and 5% of respective cases, significantly lower than historical controls.

The authors provide a retrospective cohort analysis of patients treated with PV at the UIV and UIV+1 in long-segment spinal fusions for ASD compared with controls.

Section snippets

Materials and methods

Evidence & Methods

Context

Using a retrospective methodology, the authors assessed the impact of prophylactic cement augmentation to prevent PJK and PJF.

Contribution

The findings suggest that this technique might help prevent PJK and PJF.

Implications

Given differences between groups at baseline, it is hard to draw clear conclusions. Additionally, formal functional outcomes were not assessed and we are left with a proxy in this respect. That said, the technique appears to hold some promise and may be useful for

Results

Eighty-five total surgical patients were identified (mean age: 64 years, SD=±11.1) with a mean follow-up of 25.2 months. Of these patients, 46 (54.1%) had adult degenerative idiopathic scoliosis and 39 (45.9%) had primarily a global sagittal imbalance. Forty-seven control patients (56%) were identified (Group A) without cement augmentation and 38 patients (44%) (Group B) had cement augmentation at the UIV and UIV+1.

The respective mean age of Groups A and B were 58.3 and 71.0 years, which

Discussion

Long-segment fusion for adult degenerative scoliosis and spinal deformity carries a significant morbidity in a frail population [4], [5], [8], [13], [16], [21], [42], [43]. One area focused on improving outcomes is by identifying risk factors for PJK and preventing PJF [23]. The retrospective data show that vertebroplasty use was associated with a significantly lower incidence of PJK (23.7% vs. 36.2% in controls). There were no cases of PJF with vertebroplasty use (n=6).

Increased evidence by

Conclusions

The use of prophylactic vertebral cement augmentation at the UIV and adjacent segment above at the time of deformity correction appears to be preventative in the development of proximal junctional kyphosis and failure. However, further prospective study with propensity matching is required to eliminate confounders that serve as a barrier in proximal junctional kyphosis research.

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    FDA device/drug status: Not applicable (Cement augmentation system, Confidence Spinal System, DePuy Synthes Spine).

    Author disclosures: GMG: Nothing to disclose. DGE: Nothing to disclose. JPGK: Nothing to disclose. KM: Nothing to disclose. NHL: Royalties: DePuy Spine (D); Consulting: DePuy Spine (A); Speaking and/or Teaching Arrangements: DePuy (B); Trips/Travel: DePuy (A). BAG: Nothing to disclose. JPG: Consulting: DePuy Synthes (B); Speaking and/or Teaching Arrangements: DePuy (B); Trips/Travel: DePuy, Stryker, Nuvasive, Alphatec (A); Research Support - Staff and/or Materials: Nuvasive (A).

    There are no sources of funding to disclose. This manuscript has not been previously submitted for publication, and is not under consideration for publication elsewhere in part or in full. Institutional review board approval was obtained.

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